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7.2 SRNC Relocation/Handover Between All IP and CS Domain/GSM
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7.2.1 Requirement
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The need to support these handover scenarios is for FFS.
The expected scenarios:
• Inter system handover, where target system does not support the necessary RT requirements for its packet domain (e.g. Inter system hand-over towards R97)
To fulfill this potential requirement, 2 solutions have been currently proposed (other may be studied). Any solution would face the following issues:
1. The MS has one or more PDP context for the signalling and the traffic. As the MS after the HO is handled by the CS domain, these PDP contexts need to be switched out? How to signal to the MS that its traffic is now handled by the CS domain? There is no H323 (H225 / H245) that could be used for such purpose?
2. Multimedia CC messages sizes may be larger than supported in the CS domain. The feasibility of transfering the Multi-media protocol messages on top of GSM CS signalling radio and A interface connections as well as on the MAPE interface needs to be investigated.
3. How does the SGSN determine that sessions involve the CSCF?
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7.2.2 Solution with CSCF supporting MAP E
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The following text considers the scenario when a UE has at least one session active which involves the CSCF.
On receipt of an SRNC relocation required message, the SGSN determines that the SRNC relocation results in a change of SGSN to one, which does not support the All IP services. One option is to force the serving RNS to hold the sessions until those involving the CSCF have been torn down, alternatively the SGSN needs to transfer the sessions not using the CSCF to the SGSN and the CSCF involved sessions to a 3G-MSC.
The signaling described below is based on the procedures for SRNC Relocation in 23.121. It shows that the use of the anchor MSC concept could be applied in order top maintain the Multimedia CC signaling to be tunneled back to the CSCF which acts at the “Anchor MSC”. However, issues still arise as to how to remove the PDP context to terminate it within the network.
1. On receipt of “SRNC relocation Required Message” SGSN checks for
• Do any sessions involve the CSCF? If so,
• is the target SGSN an E-GSN?
2. SGSN signals to the CSCF that a handover to an MSC is required. I.e. sends “Forward SRNC Relocation” message
3. CSCF signals “Prepare SRNC Relocation” to Non-anchor MSC including the information received from the Source RNC.
4. Non-anchor MSC starts the Relocation process, treating the CSCF as the Anchor MSC. This allows the Multi-media client CC messages to be tunneled through the Non-anchor MSC to the CSCF.
5. The CSCF instructs the GW to prepare to transfer the traffic between the PSTN and the Non-Anchor MSC. I.e. to take the GGSN out of the path.
6. Successful switch of the bearers at the RNC, takes the SGSN and GGSN out of the path. The GTP tunnels are then released.
Open Issues:
1. How does the SGSN determine which sessions involve the CSCF?
2. How does the SGSN inform the CSCF to request a connection from the MSC via a MAP-E interface? In the case of the CSCF being in an external network, it may not be possible for the SGSN to know the CSCF address.
3. For a Mobile to PSTN call, the CSCF will need to signal to the GW to route PSTN traffic to the 3G-MSC
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7.2.3 Inter-System handover using the ISHF
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The mechanism described in this section, identifies a new functional element, the ISHF. This isolates MAP/E from the CSCF. Further work is required to identify if this approach, or the approach of supporting MAP/E on the CSCF (see section 7.2.2) should be adopted.
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7.2.3.1 General
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Based on the handover requirements given in Table 4-1, the following intersystem handover scenarios should be accommodated by the All IP architecture.
• UMTS R 00 IP network to/from 2G GSM network handover
These procedures listed shall not require change to the terminal.
Figure 7-1: Support of InterSystem Handover
To support intersystem handover it is proposed that a new function is added to the architecture, called the InterSystem Handover Function (ISHF), see Figure 7-1.
The changes/additions to the baseline architecture given in Figure 7-1 include:
1. ISHF is the Inter-System Handover Function for handover between the UMTS R 00 IP networks and UMTS (PS, CS) networks and between UMTS R 00 IP networks and legacy networks. The ISHF is responsible for the handoff signaling procedures to another core network in addition to the establishment of a bearer connection between the source and target networks.
2. Mx is the interface between ISHF and the R-SGW. This interface is MAP/E and is used to signal handoff messaging between networks.
3. My is the interface between the ISHF and the GGSN. This interface relays handover related Iu signaling between the UTRAN and the ISHF. Note this is interface is tunneled through the SGSN.
4. Mz is the interface between the ISHF and the CSCF. This interface is used setup bearer resources between the source and target networks for inter-system handover.
It is assumed that the R-SGW function will interwork the UMTS R 00 IP handover procedures to the handover procedures of the source or destination network, that is the ISHF resides within the R-SGW. It may be desirable to create a separate function that performs interworking between core network protocols, this is for FFS.
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7.2.3.2 UMTS R 00 IP network to/from 2G network handover
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This example shows how handover (Hard Handover) is performed from UMTS R 00 IP network to a legacy GSM network. This demonstrates the signaling required between the networks and assumes a trunk circuit bearer between the networks. Other bearer connection schemes are possible, but not addressed in this example. (Note that all the air interface messages are not shown for clarity in the diagram. In addition, the MGCF and T-SGW are shown as a combined node and the messaging between these functions are omitted for clarity.)
Figure 7-2: UMTS R 00 IP to GSM handover
Figure 7-3: UMTS R 00 IP to GSM handover (continued)
UMTS R 00 IP GSM handover
1. Upon detection of a trigger SRNC sends RANAP message Relocation Required to the ISHF.
2. The ISHF will send the MAP/E Prepare Handover to the R-SGW.
3. The R-SGW Interworks (if required) the Prepare Handover to the appropriate network protocol (in this case GSM MAP) and sends the message to the other network (MSC)
Note: Steps 4&5 follow the normal GSM procedures and are shown only for clarity.
6. Once initial procedures are complete in GSM MSC/BSS the MSC returns MAP message Prepare Handover Response to the R-SGW.
7. The R-SGW converts (if required) to the MAP/E protocol and sends the resulting Prepare Handover Response message to the ISHF.
8. The ISHF initiates procedures to establish bearer resources between the networks. In this case a trunk circuit is established. The ISH sends a CONNECT message to the CSCF to initiate a call to set up the bearer.
9. The CSCF sends a CONNECT to the circuit gateway (MGCF, T-SGW shown combined for simplicity) to establish an outgoing call to the MSC.
10. The circuit gateway sends the ISUP IAM message to the MSC.
11. The MSC responds with the ACM message.
12. ISHF responds to the initial request from SRNC by sending RANAP message Relocation Command to the SRNC.
13. Via existing RRC connection, SRNC sends RRC message Handover Command (Hard Handover) to the UE.
Parameters: Handover type.
Note: Procedures related to synchronization etc. to GSM BSS are not shown.
Note: Step 14-16 follow normal GSM procedures and are shown only for clarity.
17. Detection of the UE within the GSM coverage results in the MSC sending MAP message Send End Signal Request to the UMTS R 00 IP network (R-SGW)
18. The R-SGW forwards the Send End Signal Request to the ISHF.
19. ISHF initiates release of resources allocated by the former SRNC (Iu Release Command).
20. ISUPAnswer is sent from the MSC to the Circuit Gateway.
21. Connect is returned to the CSCF function
22. Connect is relayed back to the ISHF.
23. Previously allocated bearer resources are released within UMTS (e.g. using RANAP and ALCAP protocols [ALCAP not shown]) (Iu Release Complete).
24. Procedure is concluded from UMTS point of view by ISHF sending MAP/E message Send End Signal Response (this message is not sent until the end of the call).
25. The R-SGW will send the MAP Send End Signal Response to the MSC.
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7.3 Areas for Further Study
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The following areas may require further study.
• Bearer set-up/control between networks during handover
• Anchoring bearer in the UMTS R 00 IP network
• MAHO support
• Inter-RNC Soft handover
• Inter RAN to RAN of same type streamlining
• Inter RAN to RAN of different type streamlining
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8 Radio Aspects
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Note: This section requires support from the RAN group.
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8.1 General
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1) CN – RAN interface definition
(a) Functional split between CN and RAN- new radio access network called EGPRS Radio Access Network (ERAN) is considered. The interface between the radio access network such as ERAN or UTRAN and the CN needs to be defined/extended and should allow different air interface technologies to access to the CN. The detailed functional split between CN and RAN needs further investigation.
(b) Impact on existing GPRS/EGPRS/UTRAN implementations and deployments
(c) Migration scenarios-2G to release 99 (BSS is not IP-based) to release 2000 (all IP-based network)
(d) Protocol stack evaluation (including evaluation of control and user planes from CN to both RAN and MS)
2) ERAN architecture (Refer to SMG2)
(a) ERAN reference model-network entities, protocol stacks and logical or functional elements
(b) Functional split between elements
(c) Definition of interaction between elements
(d) Impact on existing GPRS/EGPRS deployments (BSC, PCU, and BTS) and mitigation strategies
3) UTRAN architecture extensions
(a) Identification of required extensions
4) Realtime Handover for Packet Domain
(a) ERAN issues (Refer to SMG2)
(b) UTRAN issues
5) QoS support
(a) Evaluation of S2 QoS Ad Hoc progress for real-time data support
(b) Signalling mechanism
(c) CN issues
(d) Alignment of GPRS with UMTS QoS
(e) Realization of QoS on radio link
6) (E)GPRS Radio issues (Refer to SMG2)
(a) Real-time support including handover and QoS
(b) Spectrum efficiency/performance (e.g. statistical multiplexing and
source/channel coding)
(c) RLC/MAC enhancements
(d) The effect of various deployment scenarios (e.g. spectrum availability) and traffic mix, such as voice and data, on spectrum efficiency should be considered.
7) UTRA Radio issues
(a) Real-time packet data support including handover and QoS – validation and possible enhancement
(b) Radio efficiency/performance (e.g. statistical multiplexing and
source/channel coding)
(c) RLC/MAC enhancements if needed
(d) The effect of various deployment scenarios (e.g. spectrum availability) and traffic mix, such as voice and data, on spectrum efficiency should be considered.
Note: The RLC/MAC line items about (sections 6(c) and 7(c)) may include
• Enhanced for radio resource allocation.
• Radio access bearer definitions (i.e., define for the various traffic classes the path through the protocol stack and the bearer to be used).
• Flow classification (e.g. mapping of user traffic onto appropriate radio access bearer)
• Enhancement of EGPRS protocol to support real time service and QoS management (e.g. Fast channel allocation schemes).
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8.2 Airlink Optimisation for Real-Time IP
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8.2.1 Introduction
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In the all-IP architecture, a fundamental objective is to support IP-based real-time and non real-time traffic for a mobile terminal while achieving spectral efficiency and error robustness. In the case of real-time voice, spectral efficiency and error robustness have a performance baseline coming from the current cellular systems. There is also a baseline in voice quality. It is natural to expect that the all-IP architecture has to meet this existing baseline for voice services. The question is then how to meet the objectives of spectral efficiency and error robustness and the existing baseline for real-time voice when the all-IP paradigm is applied to cellular systems.
For IP-based real-time multimedia, RTP protocol is predominantly used on top of UDP/ IP. The size of the combined IP/UDP/RTP headers is at least 40 bytes for IPv4 and at least 60 bytes for IPv6, while the voice payload is short, typically shorter than the IP/UDP/RTP header. Clearly, if the headers were sent "as is" over the air interface to conform to the pure IP paradigm, it is not possible to meet or even get close to the baseline spectral efficiency of existing circuit voice. Some header adaptation technique is required, whereby a transformation is applied to the IP/UDP/RTP headers to reduce their size before transmission on the air interface, and the reverse transformation applied after crossing the air interface, to restore the original header size and values. Reduction of the header size is done by removing redundancy in the originally coded header information and/or removing header field information and thereby losing functionality. Impact on transparency and robustness to errors have to be fully understood in order to design the appropriate adaptation techniques (Transparency for a given header field is defined as the property whereby the value after transformation/reverse transformation is the same as in the original header).
This section explores the range of possible adaptation techniques and proposes two adaptation techniques, header stripping and header compression. The two techniques must be further studied as regards error robustness, voice quality and IP transparency.
8.2.2 user plane adaptation
In the following we refer to the functionality that does transformation/reverse transformation as User Plane Adaptation (UPA), and explore the range of possible adaptation techniques, along with their pros and cons.
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8.2.2.1 Full opacity (no adaptation)
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The UPA has no knowledge of the internal structure of the headers or payload, and no transformation is done on the IP/UDP/RTP headers which are sent in full over the air interface. Error protection is applied evenly to all the bits in the header, and evenly to all the bits in the payload. The header part will likely require stronger error protection than the payload, since a header loss will require to discard the corresponding packet, and no error concealment or mitigation can be applied to the header. This technique achieves full transparency, which allows to support protocols such as IPSEC on an end-to-end basis. An obvious con is the high overhead caused by the headers, which results in very poor spectrum efficiency.
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8.2.2.2 Payload opacity (header adaptation only)
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In this case, the UPA only needs to know the internal structure of the IP/UDP/RTP header but not of the payload. Only the headers are adapted, either by header compression or header stripping.
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8.2.2.2.1 Header compression/decompression
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IP/UDP/RTP headers are compressed before transmission over air interface and decompressed at the receiving end. Like before, headers require stronger error protection than payload. The most wellknown header compression algorithm is the Van Jacobson algorithm (RFC 1144, Compressing TCP/IP Headers for low speed serial links). In general compressed headers are more vulnerable to errors than uncompressed headers. The current standardised algorithms has therefore proven to be less efficient over lossy links such as a radio interface.
The benefit of compressing the IP/UDP/RTP header is nevertheless obvious as it significantly reduces the required overhead per packet.For an efficient header compression scheme, the IP/UDP/RTP headers can be compressed down to 2 bytes.
New header compression schemes, adapted to cellular radio link reliability characteristics, will be developed in the future. Such schemes adapted to radio environment may be able to compress the IP/UDP/RTP headers down to 2 bytes. One example among others would be a scheme currently being proposed for development in the IETF in which the compressed header carry a checksum computed over the header before compression. This provides a reliable way to detect and repair errors and increases error robustness.
A general drawback with most header compression schemes are incompatibility with end-to-end security (IPSEC) and bandwidth management, since compressed headers have variable size.
Requirements and evaluation criteria for header compression schemes to be used over the radio interface is summarised in the table 8-1.
Figure 8-1 shows a conceptual diagram of header compression used in conjunction with the lower layers in cellular. Voice is used as an example. The lower layers may perform interleaving and channel coding. For simplicity, the effect of interleaving and channel coding on the bit stream transmitted over the air interface is not shown. The effect of possible link level multiplexing with other traffic streams is not shown either. There is an MS-based UPA point and a network-based UPA point. The MS-based UPA acts as header compressor and header decompressor for the uplink and downlink respectively, while the network-based UPA acts as header decompressor and header compressor for the uplink and downlink respectively.
The requirements for header compression are described in the table below. In each case, some justification for the requirement is also provided.
#
Focus Area
Requirement
Justification
1
Performance / Spectral
Efficiency
Must provide low relative overhead (as defined in [1]) under expected operating conditions
In general, a primary goal is high spectral efficiency. Reduction of overhead has direct impact.
2
IPv6 or IPv4
Must include support for IPv6 and IPv4
Ipv4 and Ipv6 terminals are expected to coexist for some time
3
Ubiquity
Must NOT require modifications to existing IP (v4 or v6), UDP, or RTP protocol stack implementations
Enables use of current devices/services which employ generic IP/UDP/RTP stacks.
4
Cellular HO
Must support the cellular handoff operation, in an efficient manner; All fields must be transparent to the HO process, i.e, are exactly regenerated subsequent to handoff.
Target application is for adaptation of the user plane on cellular air interfaces; therefore this operation must be supported. Efficiency requirement is due to potential impacts on spectral efficiency and voice quality if HO is not properly handled.
5
Integrity
The header compression process must be lossless
Would like to maintain the end-to-end integrity of IP
6
Error Propagation
Error propoagation due to header compresion should be kept to a absolute minimum or avoided if at all possible.; error propagation is defined as the loss of packets subsequent to the one where the error actually occurred, even when those subsequent packets contain no errors
Error propagation results in lower spectral efficiency and lower voice quality; this is a serious problem for existing schemes such as [5].
7
Delay
Must operate under all expected delay conditions; header compression process must not contribute significantly to system delay budget
The user may be in different types of environments with different characteristics; additional delays will have adverse effects on conversational voice
8
Packet Loss
Must operate under all expected packet loss conditions; prefer that header compression efficiency is as independent of packet loss rate as possible
The user may be in different types of environments with different characteristics
9
Media
Supported
Must function regardless of media type in RTP payload (in general, there is NO required knowledge of payload)
The algorithm should be applicable to any type of RTP/UDP/IP data flow; note that this does not preclude optional optimizations for certain media types
10
Independence with respect to call type
Must function for mobile-mobile and mobile-landline calls; performance in each case should be comparable to existing cellular (in terms of both quality and spectral efficiency)
Both types of calls will occur in All-IP cellular systems; each is equally important
Table 8-1: Requirements for Header Compression
Figure 8-1: Header compression
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8.2.2.2.2 Header stripping/regeneration
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IP/UDP/RTP headers are stripped before transmission over air interface and regenerated at the receiving end. Essentially only the payload is transmitted, but some additional header-related information needs to be transmitted to enable the header regeneration. The degree of header transparency achieved is variable, depending on the amount of header-related information that one wants to transmit. No header error protection is needed when the header information is completely removed. However, the necessary information for header regeneration requires a header, at least for some packets. When the payload has constant size, bandwidth management issue is virtually eliminated since the payloads can be carried on a constant bit rate channel. The constant bit rate channel also eliminates QoS (delay and jitter) problems. As before, end-to-end security cannot be accomodated.
Figure 8-2 shows a conceptual diagram of header stripping used in conjunction with the lower layers in cellular. Voice is used as an example. The lower layers may perform interleaving and channel coding. For simplicity, the effect of interleaving and channel coding on the bit stream transmitted over the air interface is not shown. The effect of possible link level multiplexing with other traffic streams is not shown either. There is an MS-based UPA point and a network-based UPA point. The MS-based UPA acts as header stripper and header regenerator for the uplink and downlink respectively, while the network-based UPA acts as header regenerator and header stripper for the uplink and downlink respectively.
Figure 8-2: Header stripping
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8.2.2.3 No opacity (full adaptation)
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The UPA knows the structure of the headers and the payload. Headers can be compressed or stripped. In addition, payload transmission is optimised by techniques such as unequal bit protection, channel and error coding optimised for the payload structure, etc.
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8.2.3 Application to all-IP network
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The all-IP network is expected to provide real-time bearer services intended to carry
• Basic conversational voice (service equivalent to voice in current cellular)
• Real-time Multimedia (includes voice which is seen as a component of multimedia)
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8.2.3.1 Basic voice
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For basic voice, the emphasis is on meeting and if possible exceeding the baseline of traditional cellular in terms of spectrum efficiency, error robustness and voice quality. Traditional cellular systems achieve that baseline by using well known techniques such as unequal bit protection, channel and error coding optimised for the payload, etc. In addition, speech frames do not incur any header (in the IP sense) overhead. In the all-IP system, we propose to define a "basic voice" bearer tailored for conversational voice and possible other media with the same characteristics.
The basic voice will use payload optimisation and unequal bit protection of the payload similar to traditional cellular. Packing more speech frames into one packet will improve the relative overhead, but at the expense of added delay, which negatively impacts voice quality. Transmission of header-related information and/or compressed header will require strong error protection.
Two options eexist to achieve required characteristics for Basic Voice:
Header Stripping: At a minimum, header stripping for basic voice will have to achieve transparency for the static IP/UDP/RTP fields (those that do not change during the call) and the RTP time stamp and RTP sequence number. This bearer corresponds to the full adaptation case above with header stripping.
Header compression adapted to radio characteristics: By using a robust header compression scheme the overhead per packet is reduced to 2 bytes. Also this case shall correspond to the full adaptation case above with header compression.
Additional optimisation techniques may be contemplated to further improve the spectrum efficiency.
The two options and specific algorithms shall be evaluated according to the criteria of table 8-1 of chapter 8.1.2.1.
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8.2.3.2 Real-Time multimedia
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Real-time multimedia is a new service that does not exist in traditional 2G cellular systems. A new bearer is proposed. For that bearer, transparency for all the IP/UDP/RTP fields is crucial. Under the transparency constraint, we want to optimise spectrum efficiency and error robustness, but unlike voice, there is no baseline to be used as target. The transparency objective naturally leads to choosing header compression as the user plane adaptation. Payload will have some error protection and compressed header will have even stronger protection. The ability to provide unequal bit protection of the payload also for this service needs to be studied. This bearer corresponds to the header adaptation only case above with header compression. Specific algorithms applied to Real-Time multimedia shall be evaluated according to the criteria of table 8-1 of chapter 8.1.2.1.
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8.2.3.3 Pure IP
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The Pure IP service can be provided to accommodate end-to-end protocols such as IPSEC. In order to achieve this accomodation, the bearer does not do any adaptation and corresponds to the "No adaptation" case above. Header adaptation may also apply for Pure IP. Specific algorithms for header adaptation shall be evaluated according to the criteria of table 8-1 of chapter 8.1.2.1.
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8.2.4 Conclusions
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IP/UDP/RTP packets require adaptation to the radio link to meet the spectrum efficiency and error robustness requirements of cellular systems. It shall be investigated if a single scheme can simultaneously and fully meet the above requirements and IP transparency. An alternative to a single scheme is a gradation of schemes tailored to the particular type of application. Applications may then use different kinds of bearers optimized for their particular current needs.
real-time bearers can be categorised in Seen from the header compression point of view basic voice (BV) and real-time multimedia (RTMM). BV bearer is intended to carry voice, as a service equivalent to the one in traditional cellular systems. RTMM bearer is intended to carry generic multimedia traffic, which can include voice. In addition, a pure IP service may be contemplated for support of applications, which require full transparency.
• BV will use header stripping or header compression with unequal bit protection in the payload.
• RTMM will use header compression with equal bit protection in the payload. The possibility to support unequal bit protection in the payload shall be investigated.
• Pure IP service will support data transport without transforming the header. Header compression shall also be possible for Pure IP. Pure IP uses equal bit protection in the payload.
In all cases, header (if present) requires strong error protection.
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9 Call Control
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9.1 Terminology for Call Control
The terminology in this section is that terminology used that is new or has been changed from that defined for R99. The terminology defined in this section has not been the object of a real debate and hence cannot be considered as agreed. This section needs to be aligned with the terminology used in R99. R99 terminology should be used unless a new or changed concept is introduced. Changes to terminology defined by S1 require S1 agreement.
This section defines a common set of terms on which the present document is based on. The following list of terms is the first attempt to define some terminology.
The terminology defined here have not been matched with the existing 3GPP terminology and this matching will need to be done. Moreover, 3GPP has not defined all the terms that are needed for an all IP based network yet.
1 Access Profile: contains subscription profile information relevant to a specific bearer network. As an example, E-GPRS profile plus the radio bearer features (e.g. QoS) to which the user can access is an Access Profile. Access specific roaming information for access to and from legacy networks is a part of the access profile . As an example for CS terminals, Access Profile contains information on the allowed LA, on security data for authentication
2 Release 2000 all IP networks Service Profile: contains service subscription data relevant to the Release 2000 all IP network services the user has subscribed to. As an example, Service Profile contains user's identifier, user's aliases, user's temporary location information (e.g. pointer to the current Serving Domain), indication of the multimedia services and capabilities the user has subscribed to, service triggers, status of supplementary services, etc.
3 User Profile: is a combination of one or more Access Profiles and zero, one or more Release 2000 all IP networks and Roaming Service Profiles. The User Profile is maintained in the HSS. (FFS)
4 PDP Flow: it is a PDP context without the restriction that a different IP address has to be assigned to different PDP contexts. Differentiation between PDP flows is based on protocol type (e.g. TCP, UDP etc.) and port number. (FFS)
5 Bearer Network: it is a set of network elements that provides a user with means to connect to a serving/home domain to use services or facilities of the network the user is roaming in and gain access to the home domain or other service networks. Examples of bearer networks are:
• E-GPRS plus one or more different RANs;
• Cable Access Network, etc.
6. Domain: A domain is a logical association of network elements. A domain may contain any number of HSS, CSCFs and MRF. A domain can be Home Domain for some users (those whose subscription profile is stored in the HSS in that specific domain) and Serving Domain for other users (those whose subscription profile is stored in the HSS in a distinct domain). A domain can connect to a multitude of bearer networks. (FFS) The purpose of introducing the domain concept in release 00 is to enforce access Independence in the core, support of NAI addresses, scalability, additional services and servers expected (ex. Email/CSCF interworking), allow the use of DNS and directories for translations. Domain’s already provide the glue for many useful services and functionalities. A domain is a logical realm that indicates a system or zone. A domain is used to associate services and servers with a common identifier for translation purposes. A domain is used as a key into databases in order to obtain the network addresses of nodes for respective services associated with the domain. The actual location of nodes supporting these services is not restricted in any way by a domain. The term domain used here refers to the DNS definition of domain.
Open Issue: The use of the term, domain, home domain and serving domain requires further clarification and analysis.
7 Home Domain: it is a domain that contains an HSS. In particular, the Home Domain of a user is the domain containing the HSS that stores the user profile. Home Domain may or may not contain the Home CSCF, the MRF or service logic. Home Domain:
• provides and maintains the user and user’s subscription data in a HSS for the user belonging to the domain;
• supports also access independent users and users profile such as browser bookmarks and phone lists;
• user provides and updates the currently visited serving domain with user’s profile;
• store routing and mobility information that enables service delivery to users and users roaming outside and inside the home network;
• maintains roaming agreements and service level agreements with other networks;
• Home Domain is seen as the initial termination point from the originating network when it contains the Home CSCF;
• may collect and consolidate charging data.
Other functions are FFS.
8 Serving Domain:
• stores roaming profile as received from the home domain
• provides services or access to services in the home domain (as per terminal capabilities and service level agreement if different operator domain) with the same “look, touch and feel” as much as possible;
• stores routing and mobility information that enables service delivery to users roaming in the service domain;
• optionally collects data for billing and statistics;
• can provide local services such as location based services and information (e.g. advertisements, operator announcements to local events, etc.);
• provides optional resources such as conference devices, multimedia call control etc. (Resource could be provided in home network)
• Home Domain can act as Serving Domain when the user is registered in the home domain. (FFS)
9 Release 2000 all IP networks: A Release 2000 all IP networks comprises of the following logical components:
• One or more domain(s);
• Any number of bearer network(s);
• Connectivity to one or more MGCFs and MGWs.
• Zero, one or more MSC/GMSC Servers
10 Home Network (HN): considering a specific user, the Home Network is made of zero, one or more serving domains, any number of bearer networks, zero, one or more MGCF/MGW, and the home domain for that specific user. (FFS)
11 Serving Network (SN): considering a specific user, the Serving Network is made of zero, one or more serving domains and one or more bearer networks, zero, one or more MGCF/MGW, and does not contain the home domain of that specific user. (FFS)
12 Service Logic Domain: includes the following functions:
• contains existing telecom service capabilities (i.e. SCP for IN);
• contains WAP type capabilities for Web-based services;
• allows easy access to services by the users (notifications of new services, activation/deactivation of services in the network, capability for payment and upgrade for new services, etc.);
• updates profile data in the home domain in the event of modifications by the user or by the provider of the Service Logic Domain operator;
• provides access to or capabilities to reach other Service Logic Domain;
• some location based services can also reside in the Service Logic Domain.
The Service Logic Domain could have a tight coupling with the Home Network in order to manage/charge/provide application service capability set uniformly to the users. In particular, if CSCF handles service triggers the Service Logic Domain and Home Domain may be providing both the user’s user profile and subscription profile to CSCF in a co-ordinated/transparent fashion. The Service Logic Domain could also be stand-alone, i.e. independent from the network location. (FFS) It is for further study whether or not the CSCF can be logically associated with the service logic domain.
13 Home User: is a user of the home network having a subscription in the home domain. A user is considered a home user when the user is located in a serving domain in its home network. The user may or may not be located in their home domain.
14 Roaming User: is a user roaming outside its Home Network and being served in a Serving Network. (FFS)
Figure 9-1: Modelling of the network in domains
15 Legacy Network: a legacy network can be:
• SS7 based networks (e.g. PLMN, PSTN and ISDN) as well as CAS based networks;
• GPRS networks. (FFS)
16 Multimedia IP Network: it is an external IP network with support of real-time multimedia services (using H.323 and/or SIP protocols), and includes SIP/H.323 network elements and terminals, and possibly gateways to interface with Release 2000 all IP networks. (FFS)
17 Serving CSCF (S-CSCF): it is a CSCF in the Serving Domain with which the user is registered and that is providing the services depending on the Service Profile(s) obtained from the Home Domain of the user. (FFS)
18 Home CSCF (H-CSCF): the Home CSCF is a CSCF in the Home Domain or Private Domain. The Home CSCF is associated to a user at the subscription time and, if the user is identified by aliases that might require translation to an IP address (e.g. logical names translated by DNS), the transport address of the Home CSCF will be provided as translation of the aliases. (FFS)
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9.2 Assumptions
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The following assumptions have been considered in the development of the roaming models described in the present version of the document.
1 The addressing requirements and mechanisms will be based on the requirements and mechanisms identified by 3GPP in 3G TR 22.975 and 3G TS 33.003.
2 Call admission/denying and call re-routing will be considered. Details of call admission (e.g. authentication and QoS) will not be discussed here.
3 Re-routing of incoming voice or data communication requests that are addressed to the user's directory number during periods of realignment of the national numbering plans will be considered. Probably, a non final solution (e.g. re-direction of calls based on databases) will be provided.
4 A specific PDP flow (called Signalling PDP flow), distinct from PDP flows carrying media PDUs, is adopted to carry signalling between UE and CSCF (e.g. call set-up, in-call signalling such as flash requests). The signalling PDP flow does not need to have an IP address different from the one of the PDP flows carrying the media.
5 The user profiles are stored in a permanent way into a database/server in the Home Domain.
6 In case of roaming the user profile in the home network must be interrogated by the serving network at least at registration and part of user profile could be temporarily stored into the serving network.
7 The roaming architecture will be optimised with the assumption that IP addresses will be allocated dynamically.
8 No new requirements would be placed on the legacy (e.g. PSTN, 2G PLMN) and Multimedia IP Networks to interconnect with the Release 2000 all IP networks. Release 2000 all IP networks would have to ensure inter-operability with the existing legacy and Multimedia IP Networks. In case a 2G HLR (e.g. GPRS HLR) is re-used to hold data for Release 2000 all IP network users, the 2G HLR will be upgraded to support Release 2000 all IP network user and its interfaces might need to be upgraded.
10. An MS registration procedure consists logically of a bearer level registration (e.g. GPRS attach) and, if so specified/allowed by the MS subscription profile, an application level registration. MS registration is performed, as an example, at MS power up.
11. The bearer level registration procedure entails registration with the GPRS nodes, according to GPRS-derived procedures.
12. The application level registration procedure entails registration with a serving CSCF/MSC server in order to inform the CSCF/MSC server of the MS presence and to allow the CSCF/MSC server to retrieve the user information from the HSS.
13. Bearer level registration and application level registration are considered to be two separate procedures. Bearer level registration completeion may trigger in the UE a signalling PDP flow activation as a possible mean of supporting the application level registration procedure.
14. The MS location is tracked at the GPRS level using GPRS mobility management, and user mobility is tracked at the application level through a specific procedure aimed at updating the user information maintained by the CSCF / MSC Server and, possibly, location information held by the HSS.”
15. HSS keeps track of the user mobility in terms of the current CSCF/MSC server or Serving Domain.
16. Support of multiparty voice and data communication sessions (including the capability for the user or service logic to dynamically add or delete users from an active communication session) is not considered in the present version of this document.
17. Roaming agreements (static or dynamic) between the co-operating operators must exist.
18. Service Level Agreements (SLA) between network operators are defined (statically or dynamically) to ensure consistent level of services (e.g. end-to-end QoS, security etc.).
19. All network components that require address analysis and address translation for routing of terminating calls (e.g. CSCF, MSC server, MGCF) are capable of doing so or has access to consistent translation databases or to the HSS in order to resolve routing/call termination issues.
20. O&M functions exist to connect various components of a Release 2000 all IP network to each other, making it possible for each component to know how to address/access any other component within the network domain.
21. O&M functions exist to make network provisioning profiles (e.g. 800 triggers, tone information) available in each domain whenever.
22. In order to obtain user-plane optimisation, the serving GGSN will be preferably located in the serving network.
23. Service profile (subscription and activation status) and service triggers are either maintained by the HSS and/or updated by the HSS towards the CSCF/MSC Server.
24. CSCF-routed call signalling is assumed for real-time services.
25. Every CSCF is associated to one or more MRF, and every MRF can be controlled by more than one CSCF. For sake of clarity, if H.323 terminology is used to describe the MRF, MCU is part of the MRF. MRF could be located in the home network (when the Home CSCF is controlling the current call) or in the serving network (when the serving CSCF is controlling the current call).
26. Some of the functions of the A Home CSCF is are needed in all the roaming scenarios in order to support:
• incoming calls addressed to a DN from other Release 2000 all IP networks or Multimedia IP Networks with optimised routing (i.e. calls not routed through PSTN);
• incoming calls from other Release 2000 all IP networks or Multimedia IP Networks originated with a LN (Logical Name);
• implementation of supplementary services and Incoming Call Screening-like functions for terminated calls (e.g. Call Forwarding Unconditional).
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9.3 Roaming Within All IP networks
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In the follow, a set of roaming scenarios is described.
Editor's Note: please note that the network interfaces and the names shown in the diagrams from 6.4 to 6.7 may not always be correct.
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9.3.1 Call Model
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The call model described by the following statements has been adopted in the present document:
• Calls from/through PSTN are routed to an MGCF with connectivity to the Home Network corresponding to the dialled DN.
• Calls from a Release 2000 all IP network to a different Release 2000 all IP networks originated with a DN can be optimised (i.e. not routed to PSTN) only if the originating Release 2000 all IP networks has knowledge of the numbering plan of the destination Release 2000 all IP networks and can route the call directly to the destination Release 2000 all IP networks without leaving the IP domain. Further optimisations could be possible if the network where the call is originated has also access to the HSS of the network to which the call is destined and corresponding to the dialled DN. The same applies to calls from a Multimedia IP Network to a Release 2000 all IP network originated with a DN. (FFS)
• Assuming scenario 1, for incoming calls (i.e. mobile terminated calls), the call setup request always arrives at the ICGW which interrogates the HSS, implements Incoming Call Screening and relays (without performing any call control function) the request to Serving CSCF / MSC Server. If the originating Release 2000 all IP networks had the capability to interrogate HSS of the destination network, it would be possible to address the call setup request to the Serving CSCF directly.
• Regarding originating calls, the call request is handled by the Serving CSCF/MSc server (when present), or the Home CSCF when a Serving CSCF is not present.
This section covers only PS services.
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9.3.2 Scenario 1, Traditional Model
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The following pictures show respectively the roaming scenario 1 applied to roaming inside a single network and applied to roaming between networks.
Figure 9-2: Scenario 1 applied to roaming inside a single network
Figure 9-3: Scenario 1 applied to roaming between networks
The following points characterise scenario 1:
• both a Home CSCF and Serving CSCF are present and active;
• MT calls are routed to the Serving CSCF through the Home CSCF;
• non-basic services (e.g. supplementary services, etc.) invoked by MO calls and requiring interaction with service logic specific to the home network operator can be provided in two ways:
• Serving CSCF has a direct interface to the service logic (e.g. direct interface to a SCP in case of IN), case (1) in the above pictures;
• only Home CSCF has access to the service logic and the two CSCFs co-operate in order to provide the service, case (2) in the above pictures;
• MT Calls which reach the Serving CSCF are handled by the Servering CSCF for basic voice services;
• MT calls invoking non-basic services are handled as described for MO calls;
• user plane for MT calls is routed from the originating network to the serving network through the home network (i.e. from PSTN to MGW to GGSN in the serving network);
• user plane for MO calls to non Release 2000 all IP networks (and for non-optimised Release 2000 all IP networks to Release 2000 all IP networks calls) is routed from the serving network to PSTN through a MGW in the serving network, thus optimising the routing of user plane. In case of roaming within the same network, MGW can be chosen "close" to the bearer network again in order to optimise the routing of user plane;
• Home CSCF implements Incoming Call Screening triggers (i.e. triggers for supplementary services and IN services for incoming calls) and relays the call control signalling to the Serving CSCF address retrieved during the HSS interrogation.
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9.3.3 Scenario 2
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The following pictures show respectively the roaming scenario 2 applied to roaming inside a single network and applied to roaming between networks.
Figure 9-4: Scenario 2 applied to roaming inside a single network
Figure 9-5: Scenario 2 applied to roaming between networks
The following points characterise scenario 2:
• only a Serving CSCF is present;
• MT calls are routed to the Serving CSCF through the ICGW in the Home Domain/Network;
• all the services (basic and non-basic) invoked during MT and MO calls are provided by Serving CSCF;
• If "non basic" service means non standardised, these services will involve serving CSCF and elements within the Home domain and service logic domain.]
• user plane for MT calls is routed from the originating network to the serving network through the home network (i.e. from PSTN to MGW to GGSN in the serving network);
• user plane for MO calls to non Release 2000 all IP networks (and for non-optimised Release 2000 all IP network to Release 2000 all IP network calls) is routed from the serving network to PSTN through a MGW in the serving network, thus optimising the routing of user plane. In case of roaming within the same network, MGW can be chosen "close" to the bearer network again in order to optimise the routing of user plane.
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9.3.4 Scenario 1: Information Flows for Validation
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In order to validate scenario 1 proposed above, information flows for registration, location management and call delivery/origination are provided in this section.
The information flows presented in the Call Control and Roaming proposal do not provide many details. Generic names have been chosen for signalling messages. Any resemblance to known existing protocols is due to an attempt simply to proposing information flows immediately comprehensible. Only a restricted subset of the possible information flows is included in the document.
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9.3.4.1 Registration and Location Management
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• In this version of the Technical Report, only a basic registration procedure is considered.
• The basic registration procedure is composed of three steps:
• GPRS attach: is a plain GPRS attach procedure;
• PDP context activation: a PDP context is set up to support application level signalling;
• application level registration with CSCF.
The latter is considered in the registration flows reported in the follow.
Two basic cases of registration are shown here, in order to provide an initial picture of the application level registration.
Figure 9-6: Release 2000 all IP network user registering in Release 2000 all IP network Serving Domain
Steps 4 and 5 are optional and take place only in two cases:
• if the user was previously registered in a different Serving CSCF;
• if the user was not previously registered but, during a MT call, HSS determined that a service profile was needed in the Home CSCF to handle the supplementary services triggered by the incoming call (e.g. a forwarded-to multimedia call triggered by the MT call).
Other registration and location management scenarios are FFS.
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9.3.4.2 MT/MO Calls
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Two call information flows are presented in this version of the Technical Report. The call flows are based on the following call delivery model:
• a call from PSTN towards a DN corresponding to the user is received by one of the MGCF of the Home Network, ISP or corporate LAN domain in the IP multimedia network;
• MGCF reaches the Home CSCF translating the DN;
• Home CSCF interrogates the HSS to retrieve information regarding the user corresponding to DN;
• Home CSCF receives information on how the call has to be routed: in the flows shown here, HSS returns the signalling address of a Serving CSCF, but in general could be the transport address of the MS if there is no Serving CSCF or a forwarde-to number). Also, HSS might return service profile information in case the user is not registred.
• Home CSCF forwards call signalling to the retrieved address
Regarding user-plane, packets are routed from the MGW in the corporate LAN domain or home network to the GGSN in the bearer network where the user is presently located.
No optimisation has been considered for user-plane of MO calls. In case MO routing optimisation is desired, the MGCF used to route the call towards PSTN can be chosen using different possible criteria.
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9.3.4.2.1 Incoming call from PSTN to a Release 2000 all IP network
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The following flow describes the call delivery for a MT call from PSTN to a Release 2000 all IP network user addressed through a DN.
Figure 9-7: Incoming call from PSTN to a Release 2000 all IP network
Issues such as QoS negotiation, policy management, etc. are FFS.
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9.3.4.2.2 Call from an 3GPP IP based network/Multimedia IP Network to 3GPP IP network
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The following flow assumes that a Release 2000 all IP network user has roamed into a visited network. The flow describes a call from a different Release 2000 all IP network terminated into the home domain of the called user. It is assumed that the Release 2000 all IP network where the call is coming from, is aware of the addressing plan information (IP based addressing) that allows the call to directly terminate into the H-CSCF (otherwise, it may have been routed through the PSTN and terminated into MGCF).
Details will need to be worked on.
Figure 9-8: Call from Release 2000 all IP network to Release 2000 all IP network
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9.3.5 Scenario 2: Information Flows for Validation
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No flow will be shown for this version of the document.
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9.4 Roaming to Other Networks
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In order to ensure compatibility and easy roaming between 2G GSM/GPRS, UMTS R99 and UMTS R00 CS and GPRS domain (excluding the VoIP/multimedia domain), the same mobility procedures are used within and between the 3 kind of networks (storage of the current location in the HSS, use of MAP to update the HSS with the current subscriber location of an user and to download / update the subscriber data in the visited node).
Some enhancements with regard to current mobility procedures are obviously needed:
• in case of a R00 terminal roaming in a MSC/SGSN of a 2G / R99 network:
• R-SGW relays all the MAP / CAP messages between the HSS / SCP and the functions (MSC, SGSN, …) handling Call / Session in the 2G / R99 CN.
• the R00 HSS sends to the MSC/SGSN a MAP_R99 translation of the subscriber data compatible with the data a R99 MSC/SGSN can handle. This should be classical for MAP application context handling.
• in case of a R00 terminal roaming in R99 network and requesting Multimedia service: as in R99 there is no standard way to have a visited GK,
• Either, in order to get a customized service, the R00 terminal requests service from its Home CSCF in its R00 network. The R-SGW is not impacted in this case.
• Or, the service of a GK in the visited PLMN is used and the service cannot be customized. The R-SGW is not impacted in this case.
• in case of a R99 terminal roaming in a MSC/SGSN of a R00 network:
• R-SGW relays all the MAP / CAP messages between the 2G / R99 HLR / SCP and the functions (SGSN, …) handling Call / Session in the All IP R00 CN. The R00 VLR (in SGSN and/or CS domain) or Call / Session handling function is able to interpret MAP_R99 / CAP_R99 received from R99 HLR / SCP
• in case of a R99 terminal roaming in R00 network and requesting Multimedia service: as in R99 there is no standard way to have a visited GK,
• Either, in order to get a customized service, the R99 terminal requests service from its Home CSCF in its R99 network. The R-SGW is not impacted in this case.
• Or, the service of a GK in the visited PLMN is used and the service cannot be customized. The R-SGW is not impacted in this case.
There are currently two proposed solutions for roaming. These solutions are not completely in contradiction with each other but actually include a good set of commonalities. However, further work is needed to identify the commonalities and to consolidate the proposals. The two proposals are summarised in this section with references to more detailed descriptions. The presented roaming cases and key issues addressed in the contributions should be further considered and taken as a baseline for further work on roaming model definition for R00 networks. Alternative solutions for roaming are for further study.
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9.4.1 Roaming Procedures for R00 networks
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One possible solution for the support of roaming in R00 networks is described in Tdoc S2k99117. The contribution covers both roaming between R00 networks and roaming to mobile legacy networks. The contribution only covers the PS-only architecture in UMTS R00. Roaming from UMTS R99 considered in this document is in terms of USIM roaming. The contribution makes certain assumptions on mobility management and network identities that have to be considered as part of the future work. A basic registration procedure is introduced in order to allow the discussion on roaming.
The roaming scenarios described are:
• Roaming within R00 PS domain networks;
• Roaming from R00 PS domain networks to 2G/UMTSR99 networks;
• Roaming from 2G/UMTS R99 networks to R00 PS domain networks;
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9.4.2 Overlaid solution to roaming
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One roaming solution is to introduce an overlaid personal number service, which keeps track of users registrations (attached to 2G/3G CS and/or PS MultiMedia) and call reception preferences. This enables inter-service as well as inter network roaming for Telephony as classical TeleService Speech in 2G/3G networks and Telephony as the voice component of a MultiMedia service.
The proposed roaming solution is further detailed in Tdoc S2K-99070. The Tdoc elaborates on the driving forces for overlaid roaming and includes examples of user registration and call reception cases.
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9.5 Open Issues
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The following issues need to be discussed and solved through interaction with the other working groups in Release 2000 all IP network and might require discussion in the plenary.
• Support of multiparty voice and data communications sessions (including the capability for the user or service logic to dynamically add or delete users from an active communications session). The impact on the control plane (e.g. CSCF) and on the user plane (e.g. use of MRF vs. IP multicast) has to be studied.
• UMS structure and functionality has to be defined. As an example, UMS might have additonal interface (e.g. GRIC CSP) to the clean houses as defined in H.225. GRIC Communications, Inc. develops a global intelligent transaction platform (GRIC CSP) that allows diverse networks to interoperate. This platform allows ISPs, Telcos, and emerging carriers to offer multiple IP-based services such as IP Telephony, E-commerce, Internet Roaming, and Internet Faxing. Leveraging its GRIC Alliance Network, a worldwide membership of over 450 major ISPs and telcos in more than 140 countries, GRIC has aggregated an addressable user base of 30 million dial-up users and an estimated 40 million corporate users. For more information on GRIC see http://www.gric.org/ Routing optimisation for calls originated in a Release 2000 all IP network towards a MS of another Release 2000 all IP network and addressed using a DN (Directory Number) in order to bypass the PSTN has to be discussed.
• Also, routing of MT calls towards LN has to be specified.
• CSCF discovery has to be discussed and solutions have to be presented at the next meetings.
• Impact of requirements regarding backward compatibility with 2G networks (e.g. RAN, terminals, call control and roaming, services) needs to be addressed.
• Location confidentiality issues have to be considered versus optimisation of signalling and transport paths.
• The Release 2000 all IP network must provide the capability for service logic to deny or re-route voice and/or data communication requests. This capability has to apply to both incoming and to user initiated communication requests.
• Also, signalling flooding problems and malicious attacks to the network have to be considered.
• The issue could affect the architecture in terms of where more firewall functions will have to be implemented.
• Addressing of multiple PDP flow by means of the same IP address has to be solved as an issue if not yet standardised for GPRS.
• Details regarding the set of vocoders supported in Release 2000 all IP network and the vocoder negotiation mechanism need to be investigated.
• Signalling PDP flow can be activated when the MS attaches/registers with the network and kept alive for all the duration of the attach/registration session (dorment signalling PDP flow), or it can be activated on demand. The choice between the two options has to be discussed considering paging issues, load due to MM for the dorment PDP context even when the MS is idle, and the impact on the MS.
• Is T.120 considered as real-time application, i.e. do T.120 components of multimedia calls have to be controlled by a CSCF?
• Database queries in the HSS and other network databases has to be discussed and defined.
• Addressing of network entities and address translation need to be defined (e.g. It is assumed that MGCF has the ability to retrieve the CSCF/MSC server corresponding to a DN; how MGCF does it is FFS).
• Storage of 2G profiles in Release 2000 all IP network in order to support roaming to 2G legacy networks has to be discussed. In particular, the presence of a 2G HLR functionality in HSS need to be discussed and possible alternatives evaluated.
• Long term issues and assumptions, i.e. not related only to R00, should be considered in order to have a future proof solution. As an example, long terms requirements on addressing mechanisms (e.g. dynamic vs. static, IPv4 vs. IPv6) should be considered.
• a "VLR" type functionality capable of caching the service profile for the user in a serving domain needs to be defined. The functionality should not be related to location management but focus on service profile.
• Differences in the definition of the term “Location” as understood within the cellular/wireless community and in the IETF community have not been addressed yet in this document. This needs to be harmonized.
• Provisioning of location-based services (e.g. service based on geo-location information) and the impact on the architecture need to be considered.
• QoS and security issues have not been addressed yet.
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10 Service Platform Impacts
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10.1 3GPP Release 2000 Service Architecture
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This section describes how the 3GPP release 99 service architecture [3] can be applied to the 3GPP release 2000 network by extending the VHE/OSA concept to the Multi-Media core network. This can be done by providing an application interface (as described in VHE specification [3]) from the CSCF, see Figure 10-1.. As VHE expect the service to be located in the home domain of the end–user (the Home Environment), other network elements besides the CSCF may be needed to provide an roaming architecture that allow the serving domain to pass control to the home domain where the service logic resides. 1
Note: The architectures in Figure 10-1 and Figure 10-2 show the CAMEL Service Environment (CSE) which is not shown in the Reference Architecture in Section 5.
Figure 10-1: 3GPP Release 2000 service architecture
The Open Service Architecture consists of three parts, as illustrated in Figure 10-1(note that the figure is not meant to be exhaustive of all interrelationships):
• Applications, e.g. VPN, conferencing, location based applications. These applications are implemented in one or more Application Servers;
• Framework, providing the applications with basic services that enable applications to make use of the service capabilities in the network. Examples of framework services are Authentication, Registration and Discovery;
• Service Capabilities, providing the applications with services that are abstractions from underlying network functionality. Examples of services offered by the Service Capabilities are Call Control, Message Transfer and Location. Services are possibly provided by more than one Service Capability Server. For example, the Call Control service might be provided by CAMEL and MexE. The Service Capability Servers taken into account for UMTS Release 99 are CAMEL, MExE, SAT and HLR.
Figure 4
Figure 10-2: Overview of Open Service Architecture
Note: This may not be in line with the latest version of the VHE/OSA Stage 2 document
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10.2 IN based Services
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The IN based service is one example of legacy services and the IN based service logic is one example of how legacy services may be introduced to the 3GPP Release 2000 networks. This IN based service logic may need to be enhanced in 3GPP Release 2000 networks, based on the proposed architecture, when full support for multi-media is required.
When only voice/audio has to be supported several options exist:
1. Re-route call to legacy system. This is applicable to very specific services such as 800- and 900- services.
2. Provide ’INAP’ like interfaces between the 3GPP Release 2000 network functional blocks (e.g. CSCF) and a legacy SCP. These interfaces will be used for inter- and intra-network connections, and as such should be based on a suitable INAP protocol (e.g. CAP).
3. Provide new interfaces between legacy IN and 3GPP Release 2000 network functions, allowing the AS to access the application in the legacy SCP.
It shall be noted that the Operator Specific Services defined for the QoS enabled GPRS network are still available and apply for the access bearers towards the MM core network. This will for instance enable the pre-paid charging of the GPRS bearer.
As indicated in the sections below, option 2 (section 10.2.1) will allow the possibility that existing services can be upgraded to provide 3G users with a seamless transition of familiar 2G services, especially whilst roaming. Option 3 (section 10.2.2) does not have this advantage but benefits from future proofing. It would thus seem appropriate to allow the two options to co-exist, where support of legacy CAMEL services would be carried via option 2 and enhanced/future services can be provided via OSA principles as outlined via option 3 or a combination of both.
10.2.1 ‘INAP’ based interface between legacy SCP and R00 network entities
In this option, the classical IN model is extended to include the CSCF as a node capable of supporting a service switching function (based on the 23.078 specification of the gsmSSF) and a transaction based protocol (TCAP) with CAP. Conceptually, a new functional entity is introduced between the CSCF and the CSE. This functional entity, called a softSSF, can potentially be based on a modified release 99 GMSC, VMSC and VLR functionality, where call control, billing and database functions are retained or enhanced. This softSSF interacts with the CSE via CAP and interacts with the CSCF either via an internal interface (if it is co-located with the CSCF) or via an open interface based on OSA concepts (if the softSSF is deployed as a Service Capability Server). Some changes to CAP can be expected to take into account the impact of the underlying IP call control. The CSE is able to offer its services via defined open interfaces based on OSA principles. These services can be implemented by the CSE via the CAP interfaces to the SGSN and the CSCF. (Note the CSCF may also offer its services via defined open interface based on OSA principles).
This option benefits for the extensive re-use of standardised process (gsmSSF), protocol (CAP) and already deployed services.
Figure 10-2 Functional Architecture to support option 2
10.2.1.1 Advantages
• Maximises the re-use of existing functional entities, protocols and services. Such reuse decreases the development and ownership costs allowing existing familiar 2G services to be provided to 3G users from an early stage.
• Minimum changes to the CSE for the support of legacy services. There are several IN/CAMEL services already deployed PrePaid, VPN, Mobile Number Portability, etc which can be used in a voice over IP network.
• Potentially, CAP/TCAP can be carrier over IP (this requires further study/contributions)
• This approach is in line with the work currently underway in ETSI SPAN 3 (Services and Protocols), in particular a work item addressing IN support for voice over IP on the H.323 architecture and associated protocols in association with the TIPHON project. The study will investigate how an H.323 gatekeeper can act as a virtual Service Switching Point (SSP). It is worth noting that ETSI plan to harmonise the fixed line IN protocol (ETSI Core INAP CS3.1) and mobile equivalent (CAP Phase 3) into a common protocol targeted for ETSI Core INAP CS4.
10.2.1.2 Disadvantages
• Introduces new functional entity ‘softSSF’, which provides the necessary mapping between the CSCF and the CSE. However, this functional entity is based on the functions already provided by a VMSC/GMSC, where already standardised process such as the gsmSSF can be reused. The interface between the CSCF and the softSSF requires further study.
10.2.2 New open interface between legacy SCP and R00 network entities
This option adopts the OSA principles where the service capability servers such as the CSCF and the legacy SCF have defined APIs that allow applications in separate application servers to use the features offered by these SCS. This approach allows the service features that are provided by the SCS to be made available to applications designers with out having detailed knowledge of the specific protocols. Currently, the SCSs reflect the service capabilities in UMTS phase1, and CAMEL is one example. From TS 22.121 - “A service capability server consists of one or several server components. Taking CAMEL Services as an example, the server components could be Call Control, Location/Positioning, PLMN Information & Notifications. Each of these server components offers its services via defined open interfaces, and implements these by using GSM/UMTS protocols”.
The problem is that within an all IP network, the above mentioned server components are not all available via the CSE as there is no underlying protocol between the CSE and the network for call control (apart form the CSE/SGSN interface). To provide the same functionality provided by existing legacy services, new applications will have to be created that make some limited use of the features that may be offered by the CSE (for example database lookup), plus service features offered in the CSCF.
APIs supporting client-server models will exist. These APIs will enable the users to access service logic via the UE and specialist servers (e.g. MexE). The interface these specialist servers and the CSCF is for further study.
Figure 10-3 Functional Architecture for option 3
10.2.2.1 Advantages
• An open interface based on OSA concepts. APIs that may interface with the CSCF and the CSE are expected to become available allowing specific protocols to be hidden from the service/application designers
• Easier deployment of new/enhanced services for multimedia applications.
10.2.2.2 Disadvantages
• When considering existing CSE based services, little re-use is made of already standardised protocols, services and processes. More significantly, new processes and protocols must be re-defined and re-implemented for services that already exists, increasing development and ownership costs.
• Requires new applications on an application server to be created in order to support legacy services.
• Impact on the legacy CSE and services considered greater than option 2.
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10.3 Issues requiring further contributions
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The following issues require further contributions:
• Applications may reside not only in Application Servers (AS) but also in terminals.
• Options for sharing applications or parts of them between AS and terminals
• Which elements, beside the CSCF, will provide API for application design (aligned with VHE/OSA)
• Terminal shall also provide API for application design (aligned with MExE)
• Which new Service Capabilities/Service Capability Features are needed for 3GPP Release 2000 (e.g. WIN)
• Specific implementation cases of the proposed architecture should be provided.
• If and how 3GPP Release 2000 service features could be made accessible to 2G terminals via 2G networks
• If and how 3GPP Release 2000 service features could be made accessible to dual mode 2G/3G terminals via 2G networks
•
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11 Security
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There will be a common authentication scheme for the terminals operating in the all-IP mode, which will be SIM/USIM based. It is required that all-IP terminals will be able to register and provide basic service when used with a 3GPP SIM/USIM.
12 Work Plan
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12.1 Milestones for Release 00
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3GPP has the objective of producing the second release of specification for UMTS by the end of 2000. The project management for this work will need to include the elements of work package definition, the interdependency of these work packages and their scheduling. As the work is undertaken in the various TSGs and WGs in 3GPP there will need to be agreement across these groups on the overall plan. Subsequent communication between these groups on such issues as changes to schedules and requirements will be essential. An additional task relating to communication is the reviewing of requirements documents to identify technical problems in the implementation at an early stage. The completion of release 99 has the potential to impact the availability of resources and hence the time scales for release 00.
Note: "The text that follows is of more general nature than the rest of the document. This has been included to show the framework for release 2000, of which an All IP Architecture may be one Work Item. The dates shown are assumed dates and need to be verified by TSG-S2."
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12.1.1 Release 00 milestones
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3GPP has not yet agreed overall milestones for release 00. For the purposes development of a high-level work plan the following key milestones are proposed.
July 99 3GPP All-IP network feasibility study started
Sept 99 TSG-S2 R00 Ad Hoc will submit the results of the TSG-S2 for approval
Oct 99 After TSG-S2 approval, TSG-S2 R00 Ad Hoc Group results will be submitted to TSG-S for approval
Oct 99 After TSG-S approval Project planning work for R00 (including all IP option) will be started at TSG-S2 project planning ad hoc groups (These groups have adequate participation from all relevant TSGs/WGs).
Dec 99 After TSG-S2 approval the detailed workplan for R00 (including all-IP network option) will be submitted to TSG-S for approval.
Dec 99 Release 00 service requirements available
Jan 00 TSG-SA2 completes first draft architecture for all-IP network.
Jan 00-Dec 00 Work within 3GPP TSGs and WGs proceed according the TSG-S approved R00 Project Plan
Dec 00 Release 00 specifications completed including all-IP option
A high level PERT chart is given overleaf to form the basis of the planning for releases beyond R99. The reviewed first drafts of the service and architecture specifications should be available before the end of 1999.
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12.1.2 Detailed activity plan
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Date
Meeting group
Proposed activity
August 23 – 27
S2
Progress architectural study
September 13 - 17
S2
Joint S1 – S2 activity on R00 - Finalize the requirements for the architectural study and identify the key issues. Finalize the proposed R00 architecture at the TSG-S2 R00 ad hoc group.
Late September/early October
S2 R00 Ad Hoc Group meeting (provisional)
Possible refinements to the outcome of the ad hoc group
September 29 - 1
S1
Review input on service requirements for R00
October 11 - 13
SA Plenary
Approve the results of TSG-S2 R00 Ad Hoc Group
October 25 – 29
S2
Start the specification of the architecture, and detailed work plan.
Initiate the S2 project coordination adhoc groups work for R00 based on the approved results from TSG-SA Plenary as well as results from other groups, e.g. the Mobile IP ad-hoc group.
November 29 - 3
S1
Review service requirement and architecture
November 29 - 3
S2
Develop architecture specifications
December 15 - 17
SA Plenary
Approve detailed work plan from TSG-S2 project coordination adhoc groups
Figure 14-1: 3GPP Standardisation Activities Beyond Release 99
History
Document history
V0.0.0
July 1999
Creation of document.
V0.0.1
11 Aug 1999
Updated after R2000 Ad Hoc Swindon, 10-11th August.
Scope is clarified and new text added to requirements, Service Platform sections and a new architecture sub-section on support for R99 terminals.
Architecture changes: new CSCF <-> CSCF interface. MGW split into MGW and Transport signalling gateway. SGW to legacy network labelled as roaming gateway.
V0.0.2
1 Sept 1999
Updated after R00 Ad Hoc, based on tdocs s2k99030, s2k99031, s2k99032, s2k99035, s2k99045, s2k99049
V0.0.3
6th Sept 1999
Updated with new sections reviewed by e-mail. Contains marked changes from v0.0.2
V0.1.0
22 Sept 1999
Updated as per meeting week beg. 13th Sept (Bonn). New text on handover and IP header compression /stripping. Definitions on Mc reference point and on the Media Gateway function al blocks.
V0.1.1
28th Sept 1999
Draft for Ad Hoc Helsinki, changes include addition of HSS in section 5, agreeed solution for support of CS terminals.
V0.1.2
29th Sept 1999
2nd draft for Ad Hoc Helsinki, changes include addressing editor’s notes in section 9, addirtion of text to sections on QoS and Security and new subscetions to service Platforms
V0.1.3
30th Sept 1999
Interim draft at R00 Ad Hoc, Helsinki
V0.1.4
1st Oct 1999
Final draft for approval
V.1.0.0
7th Oct 1999
Prepared for presentation at SA#5. Technical content identical to v.0.1.4
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1 Scope
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The present document specifies the overall requirements for 3G Fault Management as it applies to the NE, EM and NM.
Clauses 4 and 5 define the fault management concept and functional requirements for the detection of faults and the generation, collection and presentation of alarms, operational state data and test results across 3G systems. These functions are described on a non-formal level since the formal standardisation of these functions across the different vendors' equipment is not required. The functional areas to be specified in this part of the document cover:
• fault surveillance and detection in the NEs;
• notification of alarms (including alarm cease) and operational state changes;
• retrieval of current alarms from the NEs;
• fault isolation and defence mechanisms in the NEs;
• alarm filtering;
• management of alarm severity levels;
• alarm and operational state data presentation and analysis at the OS;
• retention of alarm and operational state data in the NEs and the OS; and
• the management of tests.
Any (re)configuration activity exerted from the OMC as a consequence of faults will not be subject of the present document, these are described in [1].
Clauses 6 and 7 of the present document describe specific aspects of the Fault Management for the UTRAN and the CN, respectively, with particular emphasis on the exact fault definitions and alarm information to be generated. The definition of the test procedures and the relationship with the UTRAN resp. CN management architecture as defined in [3].
Finally, Clause 8 of the present document defines the functional requirements for the standard Itf-N, for the purpose of Fault Management of 3G networks, as seen from the Network Manager (NM). The Itf-N is fully standardised so as to connect systems of any vendor to the NM via this interface.
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2 References
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The following documents contain provisions which, through reference in this text, constitute provisions of the present document.
• References are either specific (identified by date of publication, edition number, version number, etc.) or non‑specific.
• For a specific reference, subsequent revisions do not apply.
• For a non-specific reference, the latest version applies.
[1] 3G TS 32.106: "3G Configuration Management".
[2] 3G TS 32.101: "3G Telecom Management principles and high level requirements".
[3] 3G TS 32.102: "3G Telecom Management architecture".
[4] 3G TS 32.106: "3G Performance Management".
[5] ITU-T Recommendation X.710: "Common management information service definition for CCITT applications".
[6] ITU-T Recommendation X.711: "Common management information protocol specification for CCITT applications".
[7] ITU-T Recommendation X.721: "Information technology - Open Systems Interconnection - Structure of management information: Definition of management information".
[8] ITU-T Recommendation X.731: "Information technology - Open Systems Interconnection - Systems Management: State management function".
[9] ITU-T Recommendation X.733: "Information technology - Open Systems Interconnection - Systems Management: Alarm reporting function".
[10] ITU-T Recommendation X.734: "Information technology - Open Systems Interconnection - Systems Management: Event report management function".
[11] ITU-T Recommendation X.735: "Information technology - Open Systems Interconnection - Systems Management: Log control function".
[12] ISO 8571: "File Transfer, Access and Management".
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3 Definitions and abbreviations
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3.1 Definitions
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For the purposes of the present document, the following terms and definitions apply:
Active alarm: an alarm that has not been cleared. An alarm is active until the fault that caused the alarm is corrected and a clear alarm is generated
Alarm: an alarm is an abnormal network entity condition which categorises an event as a fault
Alarm notification: a notification used to inform the recipient about the occurrence of an alarm
Clear alarm: an alarm where the severity value is set to "cleared"
Event: this is a generic term for any type of occurrence within a network entity. A notification or event report may be used to inform one or more OS(s) about the occurrence of the event
Fault: a deviation of a system from normal operation. This deviation may result in the loss of operational capabilities of the element or the loss of redundancy in case of a redundant configuration
Notification: information message originated within a network entity to inform one or more OS(s) about the occurrence of an event
Steady fault: a steady fault is characterised by well-defined conditions for the declaration of its presence or absence, i.e. fault occurrence and fault clearing conditions. This implies that the fault can be both detected and cleared automatically by the fault management functions of the network entity
Unsteady fault: an unsteady fault is characterised by a defined condition for the declaration of the fault, but no clearing condition exists. This implies that the fault can be detected but not cleared automatically by the fault management functions of the network entity
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3.2 Abbreviations
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For the purposes of the present document, the following abbreviations apply:
CCITT The International Telegraph and Telephone Consultative Committee
CM Configuration Management
CMIP Common Management Information Protocol
CMIS Common Management Information Service
CMISE Common Management Information Service Element
EIR Equipment Identity Register
ETSI European Telecommunications Standards Institute
FTAM File Transfer Access and Management
FTP File Transfer Protocol
HLR Home Location Register
ISO International Standards Organisation
MMI Man-Machine Interface
MML Man-Machine Language
MOC Managed Object Class
MOI Managed Object Instance
MS Mobile Station
MSC Mobile Services Switching Centre
NE Network Element
NMC Network Management Centre
OA&M Operation, Administration and Maintenance
OMC Operation and Maintenance Centre
OS Operations System
OSI Open System Interconnection
O&M Operations and Maintenance
QoS Quality of Service
RNC Radio Network Controller
TFTP Trivial File Transfer Protocol
TMN Telecommunications Management Network
TS Technical Specification
VLR Visitors Location Register
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4 Fault Management concept
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Any evaluation of the network elements' and the overall network health status will require the detection of faults in the network and, consequently, the notification of alarms to the OS (EM and/or NM). Depending on the nature of the fault, it may be combined with a change of the operational state of the logical and/or physical resource(s) affected by the fault. Detection and notification of these state changes is as essential as it is for the alarms. A list of active alarms in the network and operational state information as well as alarm/state history data are required by the system operator for further analysis. Additionally, test procedures can be used in order to obtain more detailed information if necessary, or to verify an alarm or state or the proper operation of NEs and their logical and physical resources.
The following subclauses explain the detection of faults, the handling of alarms and states and the execution of tests.
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4.1 Faults and alarms
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Faults that may occur in the network can be grouped into one of the following categories:
• Hardware failures, i.e. the malfunction of some physical resource within a NE.
• Software problems, e.g. software bugs, database inconsistencies.
• Functional faults, i.e. a failure of some functional resource in a NE and no hardware component can be found responsible for the problem.
• Loss of some or all of the NE's specified capability due to overload situations.
• Communication failures between two NEs, or between NE and OS, or between two OSs.
In any case, as a consequence of faults, appropriate alarms related to the physical or logical resource(s) affected by the fault(s), shall be generated by the network entities.
The following subclauses focus on the aspects of fault detection, alarm generation and storage, fault recovery and retrieval of stored alarm information.
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4.1.1 Fault detection
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When any type of fault described above occurs within a 3G network, the affected network entities must be able to detect them immediately.
The network entities accomplish this task using autonomous self-check circuits/procedures, including, in the case of Nes, the observation of measurements, counters and thresholds. The threshold measurements may be predefined by the manufacturer and executed autonomously in the NE, or they may be based on performance measurements administered by the EM, cf. [4]. The fault detection mechanism as defined above shall cover both active and standby components of the network entities.
The majority of the faults will have well-defined conditions for the declaration of their presence or absence, i.e. fault occurrence and fault clearing conditions. Any such incident shall be referred to in the present document as a steady fault. The network entities must be able to recognise when a previously detected steady fault is no longer present, i.e. the clearing of the fault, using similar techniques as they use to detect the occurrence of the fault. For some faults, no clearing condition exists. For the purpose of the present document, these faults shall be referred to as unsteady faults. An example of this is when the network entity has to restart a software process due to some inconsistencies, and normal operation can be resumed afterwards. In this case, although the inconsistencies are cleared, the cause of the problem is not yet corrected. Manual intervention by the system operator will always be necessary to clear unsteady faults since these, by definition, cannot be cleared by the network entity itself.
For some faults there is no need for any short-term action, neither from the system operator, nor from the network entity itself, since the fault condition lasted for a short period of time only and then disappeared. An example of this is when an NE detects the crossing of some observed threshold, and in the next sampling interval, the observed value stays within its limits.
For each fault, the fault detection process shall supply the following information:
• the device/resource/file/functionality/smallest replaceable unit as follows:
• for hardware faults, the smallest replaceable unit that is faulty;
• for software faults, the affected software component, e.g. corrupted file(s) or databases or software code;
• for functional faults, the affected functionality;
• for faults caused by overload, information on the reason for the overload;
• for all the above faults, wherever applicable, an indication of the physical and logical resources that are affected by the fault if applicable, a description of the loss of capability of the affected resource.
• the type of the fault (communication, environmental, equipment, processing error, quality of service) according to [9];
• the severity of the fault (indeterminate, warning, minor, major, critical), as defined in [9];
• the probable cause of the fault;
• the time at which the fault was detected in the faulty network entity;
• the nature of the fault, i.e. steady or unsteady;
• any other information that will help understanding the cause and the location of the abnormal situation (system/implementation specific).
For some faults, additional means, such as test and diagnosis features, may be necessary in order to obtain the required level of detail. See subclause 4.3 for details.
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4.1.2 Generation of alarms
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For each detected fault, appropriate alarms shall be generated by the faulty network entity, regardless of whether it is a steady or unsteady fault. Such alarms shall contain all the information provided by the fault detection process as described in subclause 4.1.1.
In order to ease the fault localisation and repair, the faulty network entity should generate for each single fault, one single alarm, also in the case where a single fault causes a degradation of the operational capabilities of more than one physical or logical resource within the network entity. An example of this is a hardware fault which affects not only a physical resource but also degrades the logical resource(s) that this hardware supports. In this case the network entity shall generate one single alarm for the faulty resource (i.e. the resource which needs to be repaired) and a number of events related to state management (cf. subclause 4.2) for all the physical/logical resources affected by the fault, including the faulty one itself.
In case a network entity is not able to recognise that a single fault manifests itself in different ways, the single fault is detected as multiple faults and originates multiple alarms. In this case however, when the fault is repaired the network entity must be able to detect the repair of all the multiple faults and clear the related multiple alarms.
When a fault occurs on the connection media between two NEs or between a NE and an OS, and affects the communication capability between such NE/OS, each affected NE/OS will detect the fault as described in subclause 4.1.1 and generate its own associated communication alarm toward the managing OS. In this case it is the responsibility of the OS to correlate alarms received from different NEs/OSs and localise the fault in the best possible way.
Within each NE, all alarms generated by that NE shall be input into a list of active alarms. The NEs must be able to provide such a list of active alarms to the OS when requested.
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4.1.3 Clearing of alarms
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The alarms originated in consequence of faults need to be cleared. To clear an alarm it is necessary to repair the corresponding fault. The procedures to repair faults are implementation dependent and therefore they are out of the scope of the present document, however, in general:
• the equipment faults are repaired by replacing the faulty units with working ones;
• the software faults are repaired by means of partial or global system initialisations, by means of software patches or by means of updated software loads;
• the communication faults are repaired by replacing the faulty transmission equipment or, in case of excessive noise, by removing the cause of the noise;
• the QOS faults are repaired either by removing the causes that degraded the QOS or by improving the capability of the system to react against the causes that could result in a degradation of the QOS;
• Solving the environmental problem repairs the environment faults (high temperature, high humidity, etc.).
It is also possible that a steady fault is spontaneously repaired, without the intervention of the operator (e.g. a threshold crossed fault). In this case the NE behaves as for the steady faults repaired by the operator.
In principle, the NE uses the same mechanisms to detect that a fault has been repaired, as for the detection of the occurrence of the fault. However, for unsteady faults, manual intervention by the operator is always necessary to clear the fault. Practically, various methods exist for the system to detect that a fault has been repaired and clear alarms and the faults that triggered them. For example:
• The system operator implicitly requests the NE to clear a fault, e.g. by initialising a new device that replaces a faulty one. Once the new device has been successfully put into service, the NE will clear the fault(s). Consequently, the NE will clear all related alarms.
• The system operator explicitly requests the clearing of one or more alarms. Once the alarm(s) has/have been cleared, the NE will detect that the fault condition has ceased.
• The NE detects the exchange of a faulty device by a new one and initialises it autonomously. Once the new device has been successfully put into service, the NE will clear the fault(s). Consequently, the NE will clear all related alarms.
• The NE detects that a previously reported threshold crossed alarm is no longer valid. It will then clear the corresponding active alarm and the associated fault, without requiring any operator intervention. The details for the administration of thresholds and the exact condition for the NE to clear a threshold crossed alarm are implementation specific and depend on the definition of the threshold measurement, see also subclause 4.1.1.
• Unsteady faults/alarms can, by definition, not be cleared by the NE autonomously. Therefore, in any case, system operator functions shall be available to request the clearing of unsteady alarms/faults in the NE. Once an unsteady alarm/fault has been cleared, the NE will clear the associated unsteady fault/alarm.
Details of these mechanisms are system/implementation specific.
Each time an alarm is cleared the NE shall generate an appropriate clear alarm event. A clear alarm is defined as an alarm, as specified in subclause 4.1.2, except that its severity is set to "cleared". The relationship between the clear alarm and the active alarm is established:
• by re-using a set of parameters that uniquely identify the active alarm (cf. subclause 4.1.2); or
• by including a reference to the active alarm in the clear alarm.
When a clear alarm is generated the corresponding active alarm is removed from the active alarm list.
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4.1.4 Alarm forwarding and filtering
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4.1.5 Storage and retrieval of alarms in/from the NE
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For fault management purposes, each NE will have to store and retain the following information:
• a list of all active alarms, i.e. all alarms that have not yet been cleared; and
• alarm history information, i.e. all notifications related to the occurrence and clearing of alarms.
The storage space for alarm history in the NE will be limited. Therefore it shall be organised as a circular buffer, i.e. the oldest data item(s) shall be overwritten by new data if the buffer is full. Further "buffer full" behaviours, e.g. those defined in [11], may be implemented as an option. The storage capacity itself, and thus the duration for which the data can be retained, will be Operator and implementation dependent.
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4.1.6 Fault Recovery
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After a fault has been detected and the replaceable faulty units have been identified, some management functions are necessary in order to perform system recovery and/or restoration, either automatically by the NE and/or the EM, or manually by the operator.
The fault recovery functions are used in various phases of the fault management:
1) Once a fault has been detected, the NE shall be able to evaluate the effect of the fault on the telecommunication services and autonomously take recovery actions in order to minimise service degradation or disruption.
2) Once the faulty unit(s) has (have) been replaced or repaired, it shall be possible from the EM to put the previously faulty unit(s) back into service so that normal operation is restored. This transition should be done in such a way that the currently provided telecommunication services are not, or only minimally, disturbed.
3) At any time the NE shall be able to perform recovery actions if requested by the operator. The operator may have several reasons to require such actions; e.g. he has deduced a faulty condition by analysing and correlating alarm reports, or he wants to verify that the NE is capable of performing the recovery actions (proactive maintenance).
The recovery actions that the NE performs (autonomously or on demand) in case of faults depend on the nature and severity of the faults, on the hardware and software capabilities of the NE and on the current configuration of the NE.
Faults are distinguished in two categories: software faults and hardware faults. In the case of software faults, depending on the severity of the fault, the recovery actions may be system initialisations (at different levels), activation of a backup software load, activation of a fallback software load, download of a software unit etc. In the case of hardware faults, the recovery actions depend on the existence and type of redundant (i.e. back-up) resources. Redundancy of some resources may be provided in the NE in order to achieve fault tolerance and to improve system availability.
If the faulty resource has no redundancy, the recovery actions shall be:
a) Isolate and remove from service the faulty resource so that it cannot disturb other working resources;
b) Remove from service the physical and functional resources (if any) which are dependent on the faulty one. This prevents the propagation of the fault effects to other fault-free resources;
c) State management related activities for the faulty resource and other affected/dependent resources, cf. subclause 4.2;
d) Generate and forward appropriate notifications to inform the OS about all the changes performed.
If the faulty resource has redundancy, the NE shall perform action a), c) and d) above and, in addition, the recovery sequence that is specific to that type of redundancy. Several types of redundancy exist (e.g. hot standby, cold standby, duplex, symmetric/asymmetric, N plus one or N plus K redundancy, etc.), and for each one, there is a specific sequence of actions to be performed in case of failure. The present document specifies the Fault Management aspects of the redundancies, but it does not define the specific recovery sequences of the redundancy types.
In the case of a failure of a resource providing service, the recovery sequence shall start immediately. Before or during the changeover, a temporary and limited loss of service shall be acceptable. In the case of a management command, the NE should perform the changeover without degradation of the telecommunication services.
The management of the redundancies is strictly related to the way they are modelled in the MIM of the NE. For the modelling of the redundancies, the relationships shall be defined among the objects, which participate in each redundancy. This will identify the objects and the roles that they have in the redundancy. By defining the relationships, also the role of the objects participating in the relationships are implicitly defined by the relationships’ attribute values.
The NE shall provide the OS with the capability to monitor and control any redundancy of the NE. The control of a redundancy by the OS (which means the capability to trigger a changeover or a change-back) can be achieved by means of state management, cf. subclause 4.2.
If a fault causes the interruption of ongoing calls, then the interrupted calls shall be cleared, i.e. all resources allocated to these calls shall immediately be released by the system.
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4.1.7 Support of Maintenance Action
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4.1.8 Configuration of Alarms
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4.2 State management
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The State Management is a common service defined within Configuration Management (TS 32.106) and used by several management areas, including Fault Management. In this clause, some detailed requirements on State Management as they apply to the Fault Management are defined.
From the point of view of Fault Management, only two of the three primary state attributes are really important: the Administrative state and the Operational state. In addition the resources may have some secondary ‘status’ attributes which give further detailed information about the reason of the primary state.
The Administrative state is used by the Operator to make a resource available for service, or to remove a resource from service. For example:
• for fault correction the Administrative state can be used to isolate a faulty resource;
• in case of redundancy the Administrative state can be used to lock the active resource and let the standby resource to become active (preventive maintenance);
• for Test management the Administrative state can be used to put a resource out of service to run an intrusive test on it.
The Operational state gives the information about the real capability of a resource to provide or not provide service.
• The operational state is "enabled" when the resource is able to provide service, "disabled" when the resource cannot provide service.
• A resource can lose the capability to provide service because of a fault or because another resource on which it depends is out of service (e.g. disabled or locked).
• In case a resource does not loose completely its capability to provide service, the Operational state shall be "enabled" and the Availability status shall be "degraded".
The changes of the state and status attributes of a resource must be notified to the relative manager(s) as specified in TS 32.106.
When a state change is originated by a failure, the alarm notification and the related state change notifications must be correlated to each other by means of explicit relationship information.
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4.2.1 Propagation of state change
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Within a managed element, when for any reason a resource changes its state, the change must be propagated, in a consistent way, to all the other resources that are functionally dependent on the first one. Therefore:
• In case of a fault occurring on a resource makes that resource completely out of service, if the current operational state is "enabled", it shall be changed to "disabled" and a state change notification shall be generated. Then, all the dependant resources (following the fault dependency diagram specific to that managed element) must be checked and, in case they are "enabled" they shall be changed to "disabled". In this process, also the secondary status must be changed consistently, in a way that it shall be possible to distinguish whether an object is disabled because it is faulty or because of it is functionally dependent on another object which is disabled.
• In case a faulty resource is repaired, the Operational state of that resource is changed from "disabled" to "enabled" and all the dependent resources are turned back to "enabled" (this is the simple case). In more complex cases, some of the objects may be disabled for different causes (different faults or faults plus locks on different superior resources), in this cases the repaired resource can be turned "enabled" only when all the causes are cleared (i.e. faults are repaired and superior resources are unlocked). Also in this process the secondary status must be changed consistently.
• In case the operator locks a resource, the process of the state change propagation is similar to the first case (resource failure) except for the locked resource which does not change its operational state but only the administrative state from "unlocked" to "locked". The dependent resources are processed as in the first case.
• In case the operator unlocks a resource, the process of the state change propagation is similar to the second case (fault reparation) except for the first resource (the unlocked one) which does not change its operational state but only the administrative state from "locked" to "unlocked". The dependent resources are processed as in the first case.
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4.3 Test management
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x Fault management requirements
This clause defines the FM requirements from the OS's perspective. According to the concept described in clause 4, the NEs shall maintain alarm and state change information. This information shall then be forwarded to one or more OS(s), i.e. the OMC and/or NMC. The OMC's role to play in this environment depends on implementation options chosen by the vendor and the network operator.
• The NMC interface (cf. clause 8) may be implemented in the NEs or the OMC. This means that the OMC may not be involved in the forwarding of alarm and state information to the NMC, if the NMC interface is implemented in the NE. In contrast, the OMC may have to act as a mediation device if the interface to the NMC is implemented in the OMC and the interface between OMC and the NEs uses a different (proprietary) technology.
• The network operator may choose to operate his network, in terms of FM, mainly from the NMC. This implies that functions for the forwarding and retrieval of alarms and states as well as the processing and user interface presentation of this information may not be required in the OMC, but the NMC. As a consequence, all of these functions, as described in the following subclauses, are optional in the OMC, which means they may or may not be implemented, but if implemented, they shall comply with the present document. Details of these considerations are a matter of vendor/operator agreement.
x.y Alarm and state management
x.y.z Alarm/state change forwarding and filtering
Alarm and state change events shall be forwarded by the NE, in the form of unsolicited notifications, according to the following scheme:
• as soon as an alarm is entered into or removed from the pending alarms list;
• immediately when an operational state change event is recorded in the NE.
If forwarding is not possible at this time, e.g. due to communication breakdown, then the notifications shall be sent as soon as the communication capability has been restored.
If the NMC interface is implemented in the NE, then the destination of the notifications is the NMC, and the interface shall comply with the stipulations made in clause 8. If the NMC interface resides in the OMC, proprietary means may be employed to forward the notifications to the OMC. Note that, even if the NMC interface is implemented in the NE, the OMC may still also receive the notifications by one of the above mechanisms, however, the present document does not explicitly require the NEs to support the OMC as a second destination.
The event report shall include all information defined for the respective event (cf. subclauses 4.1.2, 4.1.3 and 4.1.4), plus an identification of the NE that generated the report. This NE identification shall be identical to the identifiers defined within the CM domain, see [1].
The system operator shall be able to allow or suppress alarm reporting by the NE. As a minimum, the following criteria shall be supported for alarm filtering:
• the NE that generated the alarm, i.e. all alarm messages of that NE will be suppressed;
• the device/resource/function to which the alarm relates;
• the severity of the alarm, except "clear". Suppression of alarm clear messages shall be determined according to the following stipulations:
• if the initial alarm was not suppressed, then the alarm cleared message shall also be forwarded;
• if the initial alarm was suppressed, then the criteria set for alarm suppression at the time the cleared message occurs shall be taken into account;
• the time at which the alarm was detected, i.e. the alarm time; and,
• any combination of the above criteria.
The same functionality and criteria, as far as applicable, shall also be available for state changes, as follows:
• the NE that generated the state change event, i.e. all state change messages of that NE will be suppressed;
• the device/resource/function to which the state change relates;
• the time at which the state change occurred; and,
• any combination of the above criteria.
The result of any command to modify the forwarding criteria shall be confirmed by the NE to the requesting operator.
x.y.z Retrieval of alarm and state information
The NEs shall offer a facility for an OS to retrieve alarm and operational state information stored in the NE (cf. subclause 4.1.5). If the interface to the NMC is implemented in the NEs, then this facility shall be implemented according to the stipulations given in clause 8. If the NMC interface resides in the OMC, then proprietary means may be employed on the NE-OMC interface, however, a bulk data retrieval based on existing protocols, such as FTP, TFTP, or FTAM, is anticipated. Note that either of the two above mechanisms may still be used by the OMC even if the NMC interface resides in the NEs.
The alarm retrieval facility shall entail the following features:
• read alarms from the alarm history;
• read state changes from the state change history;
• retrieve the pending alarms from the NE; and
• read current values of the operational state.
It shall be possible to apply filters to each of the above operations as defined in subclause 5.1.1, plus the "cleared" alarm severity level.
x.y.z Support of Maintenance Action
In order to facilitate maintenance of the network, the system shall support the following OMC commands:
• request isolation of device for maintenance. Ongoing calls shall be allowed to be terminated by the users.
• request clearing of calls for maintenance. This will isolate the device addressed by the command, and ongoing calls using the device will be cleared.
• clear device from control channels (Node B - per channel, per carrier, per cell). It shall be possible to specify an alternate device to take over the channel(s), otherwise automatic reconfiguration shall be performed.
• establish priorities for automatic reconfiguration. This will force the NE's automatic reconfiguration after a fault to follow a scheme predefined by the system operator.
The NE shall confirm the result of the command to the requesting system operator.
x.y.z Configuration of Alarms
It shall be possible to configure the alarm actions, thresholds and severities through OMC commands, according to the following requirements:
• upon detection of a fault, certain actions will be carried out by the NE, e.g. putting the defective device/resource/function out of service. It shall be possible to change these activities for each individual fault.
• the operator shall be able to configure any threshold that determines the declaration or clearing of a fault. If a series of thresholds are defined to generate alarms of various severities, then for each alarm severity the threshold values shall be configurable individually.
• it shall be possible to modify, in the NE, the severity of each alarm defined in the system, e.g. from major to critical.
The NE shall confirm the result of any such alarm configuration command to the requesting system operator.
x.y.z Communication failure
If forwarding of alarms or state change events by a NE is not possible due to communication breakdown, then the notifications shall be sent as soon as the communication capability has been restored. The recipient of the notifications, i.e. the OMC and/or NMC, shall notice the communication failure and generate appropriate internal alarms in order to alert the system operator of the problem.
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5 N interface
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5.1 Fault Management concept of Itf-N
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An operations system on the network management layer (i.e. the NM) provides fault management services and functions required by the 3G operator on top of the element management layer.
As pointed out in clause 5, the N interface (Itf-N) may connect the network management system either to EMs or directly to the NEs. This is done by means of IRPs. In the following, the term "subordinate entities" defines either EMs or NEs, which are in charge of supporting the N interface.
This clause describes the properties of an interface enabling a NM to supervise a 3G-telecommunication network including - if necessary - the managing EMs. To provide to the NM the fault management capability for the network implies that the subordinate entities have to provide information about:
• events and failures occurring in the subordinate entities;
• events and failures of the connections towards the subordinate entities and also of the connections within the 3G network;
• the network configuration (due to the fact that alarms and related state change information are always originated by network resources, see [1]). This is, however, not part of the FM functionality.
Therefore, for the purpose of fault management the subordinate entities send notifications to a NM indicating:
• alarm reports (indicating the occurrence or the clearing of failures within the subordinate entities), so that the related alarm information can be updated;
• state change event reports, so that the related (operational) state information can be updated.
The forwarding of these notifications is controlled by the NM operator using adequate filtering mechanisms within the subordinate entities.
The Itf-N provides also means to allow the NM operator the storage ("logging") and the later evaluation of desired information within the subordinate entities.
The retrieval capability of alarm-related information concerns two aspects:
• retrieval of "dynamic" information (e.g. alarms, states), which describes the momentary alarm condition in the subordinate entities and allows the NM operator a synchronisation of its alarm overview data;
• retrieval of "history" information from the logs (e.g. active/clear alarms and state changes occurred in the past), which allows the evaluation of events that may have been lost, e.g. after an Itf-N interface failure or a system recovery.
As a consequence of the requirements described above, both the NM and the subordinate entity must be able to initiate the communication.
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5.2 Management of alarm and state change event reports
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5.2.1 Mapping of alarm and related state change event reports
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The alarm and state change reports received by the NM relate to functional objects in accordance with the information model of Itf-N. This information model tailored for a multi-vendor capability is different from the information model of the EM-NE interface (if an EM is available) or from the internal resource modelling within the NE (in case of direct NM-NE interface), thus a mapping of alarm and related state change event reports is performed by a mediation function within the subordinate entity.
The mediation function translates the original alarm/state change event reports (which may contain proprietary parameters or parameter values) taking into account the information model of the Itf-N.
If a mediation application function is needed, it works according to the following principles:
• Every alarm notification generated by a functional object in a subordinate entity is mapped to an alarm report of the corresponding ("equivalent") functional object at the Itf-N. If the functional object generating the original alarm notification has not a direct corresponding object at the Itf-N, the mediation functions maps the alarm to the next superior functional object in accordance with the containment tree of the Itf-N.
• Every state change notification generated by a functional object in a subordinate entity is mapped to a state change report of the corresponding ("equivalent") functional object at the Itf-N. If the functional object generating the original state change notification has not a direct corresponding object at the Itf-N, the mediation functions maps the alarm to the next superior functional object in accordance with the containment tree of the Itf‑N.
Every alarm notification generated by a manufacturer-specific, equipment-related object in the subordinate entity is mapped to an alarm report of a generic logical object, which models the corresponding equipment-related resource.
NOTE: In some cases a failure or the locking of an equipment-related object implies also the change of the operational state of its corresponding functional object within the NE or EM (if EM is available). The mapping of this state change notification to an alarm or state change notification of the corresponding functional object at the Itf-N is subject of further study.
On the Itf-N the correlation between functional related and the generic logical objects (modeling equipment-related network resources) is performed explicitly by means of a relationship attribute in the functional object class definition.
With regard to the multi-vendor capability of the Itf-N, this mapping concept combines the following requirements:
• Precise information about manufacturer-specific, equipment-related failures for the NM operator in charge of network maintenance (this information is provided in some parameters of alarm reports mapped to the generic logical objects).
• If functionality is affected, an additional alarm report concerning the related functional object is provided for the NM operator in charge of network's quality of service.
If possible, the two types of alarm reports generated by the mediation function shall be correlated.
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5.2.2 Real-time forwarding of event reports
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If the Itf-N is in normal operation (the NM connection to the subordinate entities is up), alarm and related state change event reports are forwarded in real-time to the NM via appropriate filtering located in the subordinate entity. These filters may be controlled either locally or remotely by the managing NM (via Itf-N) and ensure that only the event reports which fulfil pre-defined criteria can reach the superior NM. In a multi-NM environment each NM must have an own filter within every subordinate entity which may generate notifications.
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5.2.3 Alarm clearing
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On the Itf-N, alarm reports containing the value "cleared" of the parameter perceivedSeverity are used to clear the alarms. The correlation between the clear alarm and the related active alarms is performed by means of unambiguous identifiers.
This clearing mechanism ensures the correct clearing of alarms, independently of the (manufacturer-specific) implementation of the mapping of alarms/state change events in accordance with the information model of the Itf-N.
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5.3 Retrieval of alarm and state information
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The retrieval of alarm and state information comprises two aspects:
a) Retrieval of current information
This mechanism shall ensure data consistency about the current alarm/state change information between the NM and its subordinate entities and is achieved by means of a so-called synchronisation ("alignment") procedure, triggered by the NM. The synchronisation is required after every start-up of the Itf-N, nevertheless the NM may trigger it at any time.
b) Logging and retrieval of history information
This mechanism offers to the NM the capability to get the alarm/state change information stored within the subordinate entities for later evaluation.
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5.3.1 Retrieval of current alarm information on NM request
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The present document defines a flexible, generic synchronisation procedure, which fulfils the following requirements:
• The alarm information provided by means of the synchronisation procedure shall be the same (at least for the mandatory parameters) as the information already available in the alarm list. The procedure shall be able to assign the received synchronisation-alarm information to the correspondent requests, if several synchronisation procedures triggered by one NM run at the same time.
• The procedure shall allow the NM to trigger the start at any time and to recognise unambiguously the end and the successful completion of the synchronisation.
• The procedure shall allow the NM to discern easily between an "on-line" (spontaneous) alarm report and an alarm report received as consequence of a previously triggered synchronisation procedure.
NOTE: This requirement is for further investigation.
• The procedure shall allow the NM to specify filter criteria in the alignment request (e.g. for a full network or only a part of it.
• The procedure shall support connections to several NM and route the alignment-related information only to the requesting NM.
• During the synchronisation procedure new ("real-time") alarms may be sent at any time to the managing NM.
If applicable, an alarm synchronisation procedure may be aborted by the requesting NM. (This requirement is for further investigation.
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5.3.2 Retrieval of current state change information on NM request
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The requirements defined above for the alarm synchronisation procedure are valid analogously for the retrieval of current state change information as well.
Nevertheless the state change synchronisation procedure takes into account only the object instances whose state information is different from a combined default state. As combined default state the following values (according to [7]) shall be used:
• Operational state: enabled.
• Administrative state: unlocked.
• Usage state: idle (if supported).
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5.3.3 Logging and retrieval of alarm and state change history information on NM request
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The alarm/state change history information may be stored in the subordinate entities in dependence on the NM requirements. The NM is able to create logs for alarms/state change event reports and to define the criteria for storage of alarm/state change information according to [11].
The subsequent retrieval of stored information is possible on NM request in two different ways:
• via a read command with appropriate filtering;
• via bulk data transfer, using standardised file transfer procedures, as mentioned in subclause 5.1.2.
Nevertheless these particular requirements are not specific for alarm or state change information.
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5.4 Co-operative alarm acknowledgement on the Itf-N
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The acknowledgement of an alarm is a maintenance function that aids the operators in his day to day management activity of his network. An alarm is acknowledged by the operator to indicate he has started the activity to resolve this specific problem. In general a human operator performs the acknowledgement, however a management system (NM or EM) may automatically acknowledge an alarm as well.
The alarm acknowledgement function requires that:
a) All involved OSs have the same information about the alarms to be managed (including the current responsibility for alarm handling).
b) All involved OSs have the capability to send and to receive acknowledgement messages associated to previous alarm reports.
A co-operative alarm acknowledgement means that the acknowledgement performed at EM layer is notified at NM layer and vice versa, thus the acknowledgement-related status of this alarm is the same across the whole management hierarchy.
The co-operative alarm acknowledgement on Itf-N shall fulfil the following requirements:
• Acknowledgement messages may be sent in both directions between EMs and NM, containing the following information:
• Correlation information to the alarm just acknowledged. - Acknowledgement history data, including the current alarm state (active | cleared), the time of alarm acknowledgement and, as configurable information, the management system (EM | NM) and the operator in charge of acknowledgement (the parameter operator name or, in case of auto-acknowledgement, a generic system name).
• Acknowledgements notifications sent to NM shall be filtered with the same criteria applied to the alarms.
• The alarm acknowledgement procedure on the Itf-N shall cope with different customer requirements concerning the acknowledgement competence between operators working at EMs and NM. This matter may be managed by means of a "competence type" information, which may be controlled by every connected EM.
• Every time the communication between the two management systems is established, the NM is able to determine which OS is most suitable to handle the acknowledgement of alarms.
• Taking into account the acknowledgement functionality, the above described synchronisation procedure for retrieval of current alarm information on NM request may be extended. Additionally to the requirements defined in subclause 8.3.1, this extended synchronisation procedure relates not only to the active, but also to the "cleared and not acknowledged" alarms, which have still to be managed by the EM.
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5.5 Overview of IRPs related to fault management
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The N interface is built up by a number of IRPs. The basic structure of the IRPs is defined in [2] and [3].
For the purpose of Fault Management the following IRPs are needed:
• Alarm IRP
• Notification IRP
• Log IRP
(NOTE: This IRP may not be part of Release 1999)
Annex A (informative):
Change history
This annex lists all change requests approved for this document since the specification was first approved by 3GPP TSG-SA.
Change history
TSG SA#
Version
CR
Tdoc SA
New Version
Subject/Comment
S_07
2.0.0
-
SP-000013
3.0.0
Approved at TSG SA #7 and placed under Change Control
Mar 2000
3.0.0
3.0.1
cosmetic
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1 Scope
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This document outlines the working methods [to be] used by SMG and its sub-groups and by PT SMG in relation to document management, i.e. handling of specifications, updating procedures, change request procedures, version control mechanisms, specifications status information etc. It complements the rules and procedures defined in ETSI. This document does not stipulate the details of the internal working of the TB sub-groups. From the Technical Specification Group point of view, a task and responsibility is given to a Working Group (WG) directly answering to SMG. In practice, the work/task may be carried out in a subgroup of that WG.
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2 Definitions and Abbreviations
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Change Control When a specification has been put under change control, changes to the specification require an approval of formal change requests. Rules for change control are defined in section 4.
Closed A closed major version of a specification is still published; however no changes to the major version of the specification are possible anymore (not even essential corrections).
CR Change Request.
Draft A specification is draft before getting under change control.
Frozen For a frozen major version of a specification, the only allowed change requests are essential corrections.
Major Version For version w.x.y of a specification, w is called the major version. Example: For version 7.2.0 of a specification, the major version is 7.
Project Team The support group supporting the Technical Body.
PT Project Team
Specification In this document, the generic term Specification is used for both Technical Specifications and Technical Reports. A distinction between the two is done only where relevant.
TB Technical Body, denotes Technical Body SMG
TB Change Control Technical Body Change Control: The Technical Body is responsible for approval of Change Requests.
TB Sub-Group: An TB Working Group or a subgroup installed by a TB Sub-Group (recursive definition)
TB WG Technical Body Working Group
Technical Body Working Group A working group installed by the TB and reporting to the TB. This denotes an SMG Sub-Technical Committee, such as SMG1, SMG2, …
TB WG Change Control Technical Body Working Group Change Control: The TB Working Group is responsible for approval of Change Requests.
Version A specification has versions which are identified by three numbers w.x.y. Example: version 7.12.3.
WI Work Item.
WID Work Item Description.
Withdrawn A withdrawn specification doesn’t belong to the set of valid specifications.
Work Item A work item aims at introduction of a new feature or at enhancement of existing features. It may entail new specifications and/or changes to existing specifications.
Work Item Description The description of a Work Item in a standard Work Item Description sheet.
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3 General responsibilities of the Project Team
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The Project Team for SMG (PT, or PT SMG) is responsible for the project management of the work of the TB. This includes editorship and management of specifications once they have been put under TB change control. It also includes preparation of and support for the meetings (including meeting reports) of the TB and its Sub-groups, in descending priority
TB > TB WG > other TB SG.
It furthermore includes liaison to other bodies and relevant groups and institutions.
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4 Handling of Specifications
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This section describes the general procedures and events involved in, and related to, the lifetime of a specification.
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4.1 Overview
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This section gives an overview on the development of a specification, dealing with the unexceptional cases only, and leaving out details. A more detailed description is given in the remainder of section 4.
A new specification is created in a TB WG. At creation, a rapporteur is nominated. The rapporteur elaborates the first versions, version 0.0.0, version 0.1.0, possibly 0.1.1, 0.1.2 and so on, then version 0.2.0 etc..
The versions 0.1.0, 0.2.0, 0.3.0 etc. must be presented to the responsible TB SG. The versions 0.i.1, 0.i.2 etc. may be internal versions.
As soon as title, scope and some other information on the specification is stable, the PT assigns a specification number and enters the specification into the Status List of Specifications, see section 7.
When a specification is sufficiently stable, it is presented as version 1.0.0 to the TB for information.
Further versions 1.x.y are elaborated until version 2.0.0 is presented for approval at the TB.
After approval, the specification becomes version x.0.0 where x >=3. It is under TB change control. Further changes are made by means of formal change requests, to be approved by the TB. The number x is called the major version of the specification. If all change requests approved were editorial, the new version increments the right most number (e.g., from 7.2.1 to 7.2.2); if at least one approved CR has been non-editorial, the middle number is incremented and the right most number reset to 0 (e.g., from 7.2.1 to 7.3.0).
At some point in time, the specification is frozen: Only corrections of essential errors will be applicable. (At the same time, a new major version may be developed for inclusion of new features.)
At a later point in time, the specification is closed: it is still publicly available, but no changes are carried out any more. (At the same time, higher major versions of the specification may be under development.)
The major versions of specifications may be developed in releases: Releases like Release 1999, Release 2000, Release 20001 are specified in major versions of the specifications.
For example,
- GSM phase 1 is specified in the most recent versions 3.x.y of the specifications, that is in major version 3;
- GSM phase 2 is specified in the most recent versions 4.x.y of the specifications, that is in major version 4;
- GSM Release 96 is specified in the most recent versions 5.x.y of the specifications, that is in major version 5;
- GSM Release 97 is specified in the most recent versions 6.x.y of the specifications, that is in major version 6;
- GSM Release 98 is specified in the most recent versions 7.x.y of the specifications, that is in major version 7.
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4.2 Characteristics of a specification
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- The specification has a prime responsible TB.
- The specification may have a prime responsible TB WG.
- The specification may have one or more secondary responsible TBs and/or TB WG.
- The specification may have a prime responsible TB Sub-Group below a Working Group as decided by the prime responsible TB WG.
- The specification should have a rapporteur (i.e., at least one rapporteur): a delegate from a member company (or, in exceptional cases, a PT expert); the delegate participates regularly in the prime responsible TB WG (and further TB SG if applicable).
- The specification is a Technical Report or a Technical Specification
- A specification has versions which are identified by three numbers w.x.y where w is called the major version.
Note: In the description above, attribute values are underlined while attributes aren’t.
The prime responsible TB WG may assign prime responsibility for a specification to one of its subgroups.
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4.3 Characteristics of a major version of a specification:
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A major version 0 or 1 or 2 of a specification has the following characteristics:
- It is either a draft or withdrawn.
- It is TB internal.
A major version w > 2 of a specification has the following characteristics:
- It is either under TB WG Change Control or under TB Change Control or closed or withdrawn.
- It is either authorised for publication or TB internal.
A major version of a specification under TB WG Change Control is TB internal.
A major version under TB WG Change Control or TB Change Control is called major version under Change Control.
A major version of a specification under TB Change Control is
- either not yet frozen or frozen.
Note: In the description above, attribute values are underlined while attributes aren’t.
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4.4 Characteristics of a version of a specification
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0.x.y
- draft (or withdrawn)
- TB internal
- no version of the specification has been presented for information to the TB yet
- no major version of the specification is under TB change control yet
1.0.0
- draft (or withdrawn)
- TB internal
- this version 1.0.0 is presented to TB
- for information
- or for information and approval
- no major version of the specification has been under TB Change Control yet
1.x.y (x > 0 or y > 0)
- draft (or withdrawn)
- earlier version 1.0.0 has been presented for information to the TB
- no major version of the specification is under TB Change Control yet
2.0.0
- draft or withdrawn
- TB internal
- earlier version 1.0.0 has been presented for information to the TB
- this version 2.0.0 is presented to the TB for approval
- no version of the specification has been approved yet
- no major version of the specification has been under TB Change Control yet
2.x.y (x > 0 or y > 0)
- draft
- TB internal
[- earlier version 1.0.0 has been presented for information to the TB]
- no major version of the specification is under TB Change Control yet
- earlier version 2.0.0 had been presented to the TB for approval but had not been approved by the TB
x.y.z (x 3)
- under TB Change Control or closed
- TB internal or authorised for publication
[- earlier version 1.0.0 has been presented for information to the TB]
- earlier major versions of the specification, if any, shall be under TB Change Control or closed or withdrawn
draft y.z of version x
- under TB WG Change Control
- TB internal
[- earlier version 1.0.0 has been presented for information to TB]
- earlier major versions of the specification, if any, shall be under TB Change Control or closed or withdrawn
Notes: In a future version, file name conventions should be added in the table above.
In the table above, statements between square brackets are true but not relevant. The first two lines of each row are implied by section 4.2.
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4.5 Actions on a specification
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In the following subsections the concept of "stability" is used , which is linked to the likelihood that a given specification will change more or less significantly before reaching it's final steady. The attributes "low stability", "medium stability" and "good stability" are used. The assessment of stability cannot be based on absolute criteria and is left to the decision of the responsible TB WG(s) and finally decision of the TB.
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4.5.1 Actions on a new specification (version 0.x.y)
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- A new specification (a specification version 0.0.0) may be created by a TB WG. A rapporteur (more exactly: at least one rapporteur) is assigned by that WG. A prime responsible subgroup of the TB WG may be allocated by the TB WG.
- The rapporteur prepares version 0.1.0 and presents it to the prime responsible TB WG/SG for discussion.
- In an iterative process, the rapporteur prepares a new version 0.x+1.0 incorporating comments from the prime responsible TB WG/SG to versions 0.x.y and presents version 0.x+1.0 to the prime responsible TB WG/SG for discussion.
- Between version 0.x.0 and 0.x+1.0, the rapporteur may create versions 0.x.1, 0.x.2, … with only editorial modifications.
- When the title and scope of a specification is sufficiently stable, a Specification Number is assigned by the PT, which also informs the other relevant Technical Bodies.
- The TB WG reports the creation of a new specification to the TB.
- New specifications should be co-ordinated between the 3GPP TSGs and SMG. These bodies should seek agreement on prime and secondary responsibilities for each specification. In areas of common interest it is recommended to agree on new specifications in joint meetings.
- The TB may cancel a new specification.
- The TB WG may decide to present a specification version 0.x.y to the prime responsible TB and to the secondary responsible TB SG(s) for information; the specification should then have reached the “medium stability” state.
- The TB WG may also conclude that the specification has already reached the “good stability” state and decide to present it to the TB for information and approval; before doing that, comments from secondary responsible TB SGs, if any, should have been taken into account.
Then the specification is handed over to the PT for the necessary - strictly editorial - cleaning up resulting in version 1.0.0.
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4.5.2 Actions on version 1.x.y of a specification
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- On decision of the prime responsible TB WG, the PT transforms version 0.x.y of a specification into version 1.0.0, performing the necessary - strictly editorial - cleaning up, and version 1.0.0 is presented by the TB WG to the to the prime responsible TB and to the secondary responsible TB SG(s) for information or for information and approval.
- The TB may decide to put the specification under change control as major version x (where x > 2 depends on the Release which the specification belongs to). In this case, version 1.0.0 is transformed by the PT into version x.0.0, and the further handling is described in section 4.5.4. Otherwise, the handling of the specification continues as described below:
- In an iterative process, the rapporteur prepares a new version 1.x+1.0 incorporating comments from the prime and secondary responsible TB SGs to versions 1.x.y and presents version 1.x+1.0 to the prime and secondary responsible TB SGs for discussion.
- Between version 1.x.0 and 1.x+1.0, the rapporteur may create versions 1.x.1, 1.x.2, … with only editorial modifications.
- The prime responsible TB WG may decide to present a specification version 1.x.y to the prime responsible TB for approval; the specification should then have reached the “good stability” state ; comments of the secondary responsible TB SGs should have been taken into account.
Then the specification is handed over to the PT for the necessary - strictly editorial - cleaning up resulting in version 2.0.0.
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4.5.3 Actions on version 2.x.y of a specification
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- On decision of the prime responsible TB WG, the PT transforms version 1.x.y of a specification into version 2.0.0, performing the necessary - strictly editorial - cleaning up, and version 2.0.0 is presented by the prime responsible TB WG to the prime responsible TB for approval; comments of the secondary responsible TB SGs should have been taken into account. If version 2.0.0 is not approved, work continues with versions 2.x.y.
- The TB may decide to put the specification under change control. In this case, version 2.0.0 is transformed by the PT into version x.0.0, (where x > 2, see section a.4), and the further handling is described in section 4.5.4. Otherwise, the handling of the specification continues as described below:
- In an iterative process, the rapporteur prepares a new version 2.x+1.0 incorporating comments from the prime and secondary responsible TB SGs to versions 2.x.y and presents version 2.x+1.0 to the prime and secondary responsible TB SGs for discussion.
- Between version 2.x.0 and 2.x+1.0, the rapporteur may create versions 2.x.1, 2.x.2, … with only editorial modifications.
- The prime responsible TB WG may decide to present a specification version 2.x.y to the TB for approval; the specification should then have reached the “good stability” state ; comments of the secondary responsible TB SGs should have been taken into account.
Then the specification is handed over to the PT for the necessary - strictly editorial - cleaning up resulting in version 2.x+1.0.
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4.5.4 Actions on version w.x.y of a specification (w > 2)
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- On decision of the TB, the PT transforms a version v.x.y of a specification into version w.0.0, performing the necessary - strictly editorial - cleaning up.
- The prime responsible TB WG may agree on Change Requests to the most recent version w.x.y of major version w of a specification. It will then propose these CRs to the TB for approval, however before doing that, it has to seek comments from the secondary responsible TB (WG)s - if any - and to take them into account (joint meetings of the appropriate TB SGs are recommended for that purpose). If and when at least one Change Request to version w.x.y of major version w of that specification is approved by the TB, the PT includes all Change Requests to version w.x.y of major version w of that specification into a new version
- w.x.y+1 if all change requests approved by the TB are editorial
- w.x+1.0 if at least one change request approved by the TB is not editorial
- From a version w.x.y of major version w of a specification, the PT may create a new version w.x.y+1 where only changes in the front sheet, preface and history are performed (for publication purposes)
- From the most recent version w.x.y of major version w of a specification, the PT may create a new version w.x.y+1 in agreement with the rapporteur and the prime responsible TB WG where only strictly editorial changes are performed.
- If Change Requests have been introduced incorrectly into the most recent version w.x.y of major version w of a specification, the PT may create a new version w.x+1.0 in agreement with the rapporteur and the prime responsible TB WG, to correct the introduction of Change Requests.
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4.5.5 Actions on the major version of a specification
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- The TB may decide to create a new major version >2 of a specification.
- The TB may decide to withdraw a major version of a specification.
- The TB may decide to close a frozen major version of a specification.
- The TB may authorise a major version >2 for publication or decide that it is TB internal.
- The TB may decide to freeze a major version of a specification under change control.
- The TB may decide to unfreeze a major version of a specification under change control.
- The prime responsible TB WG may decide to create a new major version > 2 of a specification under TB WG Change Control.
These decisions have to be taken in agreement with all relevant TBs (that is with all applicable TSGs, if UMTS is concerned).
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4.6 Change Request Regime
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Modifications to specifications under TB Change Control are decided by the TB, on the basis of Change Requests (CR). These CRs, described in the following sections, shall in principle only be presented to the TB after having been scrutinised by the TB WG responsible for the concerned specification; comments from secondary responsible TBs (if any) have to be have sought and comments have to be have taken into account.
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4.6.1 Change Requests
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Whenever an error or an inconsistency is discovered or when a new feature is proposed to be included, a Change Request is produced, normally by the one discovering the error but in consultation with the rapporteur and/or with the PT.
In the case of an essential error corrections, separate Change Requests for each affected major versions that is under TB Change Control or TB WG Change Control shall be produced.
In the case of a correction of a non-essential error, separate Change Requests for each affected major versions that is
- under TB Change Control and not yet frozen or
- under TB WG Change Control
shall be produced.
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4.6.2 Change Request forms
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To ensure an appropriate and consistent way of presenting and documenting Change Requests, there exist standardised front covers (forms) for CRs as well as rules on how to accurately identify the modified parts of the specification.
The purpose of the CR form itself is to provide the relevant management information of the proposed changes, e.g. such as
- Target specification with its version number,
- Source of the CR,
- Reason for the proposed change and consequences if not accepted,
- Category of proposed change (i.e. correction, change request corresponding to an earlier phase change request, addition of feature, functional modification of feature, or editorial modification),
- Cross-phase compatibility aspects.
As the degree of acceptability for modifications differs between not yet frozen major versions of specifications and frozen major versions of specifications, the CRs differ on the allowed/possible Categories:
- CRs to a frozen major version of a specification can only be essential corrections whilst
- CRs to a not yet frozen major version of a specification can also fall into any other of the categories quoted above.
The actual CR forms to be applied and guidance how to apply them are distributed by the PT. The access to them is described in an annex of each TB plenary report.
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4.6.3 Contents of Change Requests
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Although the CR form shall indicate the details of change, each CR shall have attached the pages of the specification that are affected by the CR, using the latest version of the major version. These pages shall have the proposed modifications clearly marked, by means of the word processor's "revision mode", i.e. new proposed text should be double underlined (xxx) and proposed deletions should be marked by strike through (xxx), and a bar in the margin should further indicate the change.
In case there are more than one independent CR to the same part of the specification, neither of them should contain the proposed modifications from the other(s), however any potential interaction between the modifications should of course be resolved before presentation.
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4.6.4 Handling of the Change Requests
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Entry to the TB WG:
A proposed CR should be brought to the relevant TB WG or, if applicable, to the prime responsible TB SG in charge of the specification concerned and discussed there, before presentation to the TB. If possible it should be distributed, by the source, as soon as possible and prior to the coming TB SG / TB WG meeting to the relevant email reflector (with a clear indication of the subject) , for the purpose of shortening discussions in meetings and to try at an as early stage as possible to come to a widely acceptable solution. Comments from secondary responsible TBs (if any) have to be have sought and comments have to be have taken into account before presentation to the TB for approval.
When the relevant TB WG decides to submit a CR to the TB for approval, the CR is categorised as strategic or non-strategic by the TB WG chairperson in agreement with the TB WG. Non-strategic CRs are submitted to the TB for approval without presentation; strategic CRs are submitted to the TB for approval with presentation.
To ease the work of the TB SG and of the PT, a proposed CR should be presented in a form suitable for TB SG agreement and TB approval. If a CR is not immediately accepted it is the responsibility of the originator to update the CR taking into account comments and other guidelines from the relevant groups, including change of reference version if needed, and to re-present it to the TB SG.
Note: It is also highly important that the originator of the CR provides the PT with an electronic copy since the contents is supposed to be incorporated into the specification, by the PT, and re-typing of CRs is clearly a waste of resources and a possible source of errors.
CR identification:
A CR can have different revisions: rev. 0, 1, 2, and so on. Revision 0 of a CR is the not revised CR. A given revision of a CR is applicable to a certain version of a specification. The CR identifies, to which specification, which version of the specification and which phase it applies. A given revision of a CR is uniquely defined by
- the specification it belongs to
- an alphanumeric string (the CR number) and
- the revision number (default, i.e. the value if no number is given, is 0).
One CR may only apply to one version of a specification, that is to the latest version of a major version. If more than one major version of a specification exists, it may be necessary to elaborate parallel CRs for different major versions.
The uniqueness of the CR number is on a per specification basis, but independent of the major version, i.e. CR No 001 [may] exist for each specification but only once.
The CR number is allocated by the PT. It may be allocated prior, during or after the TB SG meeting at which it is discussed but before submission to the TB. Even though different TB SGs have different working routines it is beneficial and thus recommended that CR numbers are allocated no later than at TB SG agreement.
CR numbers are unique and shall never be reused, not even numbers used for [early] rejected CRs.
Impact on other specifications and Joint CRs:
If the contents of the CR is such that isolated it makes the whole set of approved Specifications inconsistent, corresponding CRs must also be considered and produced. This shall preferably be carried out by the originator of the CR (and his/her colleagues in other TBs and TB SGs) in advance. The PT is co-responsible for identifying and communicating cross TB and cross TB SG impacts.
In principle, a CR shall not be forwarded to the TB unless the potential impact on other specifications have been thoroughly examined and concluded, either resulting in a 'No impact' statement or in a full and consistent set of corresponding CRs to all affected specifications. Such sets of CRs are normally combined in one single document, by the PT, before submission to all responsible TBs and called 'Joint CR'. An approval by all prime responsible TBs is necessary.
If some of the corresponding CRs are to be considered by other TB SGs or TBs then the PT is responsible for monitoring the result in the TB SGs and to submit the full set, when available, to the TB. This might mean that in some cases the TB SG agreed CRs are not presented to the immediately following TB meeting due to outstanding CRs from other TB SGs or TBs.
Other "consequential" CRs, needed for reasons other than direct consistency, may be drafted, presented and agreed independently. This covers typically additions to Test specifications and O&M specifications. It should be noted though that if a CR causes an inconsistency with an existing/approved test or O&M specification, the corresponding CRs should be presented together with the core specification CR.
Handling of the CR in the TB:
If the TB WG has agreed to a CR and comments from secondary responsible TB (SG)s have been taken into account, the CR is forwarded to the prime responsible TB for formal approval. It is the responsibility of the PT to make sure that TB WG agreed CRs are made available to the TB, and that they are properly formatted, numbered and consistent. Likewise, it is the responsibility of the PT to ensure that Joint CRs are complete and put together before submission to the TB(s).
Non-strategic CRs are submitted to the TB for approval without presentation; strategic CRs are submitted to the TB for approval with presentation.
The PT is responsible for making available to the TB summary lists of all CRs presented for decision. This list is then updated to include the result of each and every CR.
Note: This list is generated from the CR database held by the PT, see section 7.
Decisions on CRs, and results:
The TB considers and concludes on each strategic CR independently, except for Joint CRs which are handled and concluded together, and the verdicts could be as follows:
Verdict
Meaning
Approved:
Contents to be incorporated in the specification.
Postponed:
Concept of CR seems acceptable in principle but further refinements are necessary. CR is sent back to the TB-SG for revision and possible re-submission at a later TB meeting.
Rejected:
CR not acceptable in any sense. If further discussions on the subject should take place that shall be done on the basis of different documents and approaches.
Non-strategic CRs presented to a TB meeting are automatically accepted at the end of the meeting if no TB delegate requested discussion of the CR during the TB meeting. If at least one delegate requests discussion of a non-strategic CR during the TB meeting, the CR is presented to the meeting and further treated as a strategic CR.
If there is at least one Approved CR to a given specification, a new version number of the specification is allocated (see clause 4.2.3), and the PT will produce and issue a new version of the specification after the TB approval.
Control and notification of CR decisions:
• The PT makes available the list of non-strategic CRs presented to a TB meeting before the meeting to all heads of delegation.
• Towards the end of each TB meeting, the PT issues lists containing the detailed result of the CRs presented at the meeting, including information about the consequential new version numbers of the concerned specifications. These lists form an annex to the meeting report (and hence are part of a permanent document). These lists, being the evidence of which specifications have changed and how, are important management tools for both TB delegates and the PT since it always takes some time before the new versions of the specifications as such can be compiled and released.
Databases: See section 7.
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4.6.5 Updating and release of new versions of the specifications
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After TB approval of one or more CRs, the PT produces a new version of the specification (with the version number incremented according to above).
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5 Availability and distribution of specifications
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The latest versions of TB approved and TB WG approved specifications are made available on a TB server (exact location see TB meeting report) by the PT. For specifications (or major versions of specifications) that are not yet under change control, the versions presented to the responsible TB-SG or WG, shall be made available to the PT by the rapporteur and made available on a TB server by the PT.
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6 Work items
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For project management purposes, the work is itemised in Work Items (WI), which are documented, developed and handled as described in this section.
The possible modifications of the specifications are basically of different natures:
- Error corrections; Modifications which correct overlooked errors or inconsistencies in the specifications.
- Enhancements; Modifications that enhance the system, e.g. by new services or features, or by improving performance or decreasing costs.
Modifications of the correction category are ongoing maintenance tasks and are handled with direct CRs and thus not by means of Work Items.
Modifications of the enhancement category are handled within the concept of Work Items as described in the sections below. Note that prior agreement of the TB is needed before any substantial work is launched.
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6.1 Creation of a Work Item
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When an enhancement of the standard is considered desirable a delegate or delegation can make a proposal by submitting a Work Item Description sheet to the relevant TB or TB WG.
- For new services, features or functions, the TB responsible for Services and System Aspects is the relevant TB. This TB also assigns prime and, if necessary, second responsible TBs for the corresponding work items.
- For pure performance enhancements, other TB WGs may be the responsible TBs (the test specifications are normally not seen as independent work items).
The relevant TB WG should study and refine the WI sheet before passing it on to the TB for adoption.
No substantial work shall commence in a TB WG prior to a decision of the responsible TB.
The actual WI description sheets to be used and guidance how to apply them are distributed by the PT. The access to them is described in an annex of each TB plenary report.
The TB shall not approve a WI unless the Work Item Description (WID) sheet has been properly filled in to the degree possible at that time.
Once the TB has approved the WI, it is included in the WI Status List and the WI Description sheet is included in the WID compilation. Both these actions are carried out by the PT. The WID should be updated as soon as new information is available.
The effects of the WI in terms of initial work distribution and responsibilities in the TB (WG)s must be identified and allocated. Also, one or more rapporteurs have to be identified for the initial tasks, typically one for the service aspects and one for the system requirements. This should preferably be done prior to submission to the TB, but in the worst case during the following TB (WG) meetings. This information is also included in the WI Status List managed by the PT. During the lifetime of the WI, additional responsibilities as well as output documents and corresponding rapporteurs can be identified. Similarly, this information is then included in the status list.
A work item normally implies the creation of new specification and Change Requests to existing specifications.
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6.2 Type of Work Items
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Modifications of the standard could in principle be of two different types:
- New services/features/functions that in general affects several specifications and several TB-SGs;
- Pure [technical] enhancements that affects a small number of specifications and TB-SGs only (generally only one).
Of these, modifications of the latter type can be submitted to the TB SG(s) and then TB directly as a Change Request without prior presentation/agreement of a WI Description sheet. Such CRs shall instead refer to the pseudo Work Item 'Technical Enhancements'. For the other type of modifications, the following sections apply.
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6.3 Start and continuation of the work and responsibilities
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An early task when elaborating a work item is to identify the tasks related to the WI and allocate those to the TBs and TB SGs.
In most cases the tasks from a WI can be split immediately in the following areas:
- Service requirements
- System/Architectural requirements and implications
- Protocol specifications
Service requirements:
The responsibility of the service requirements can usually be allocated immediately at the creation/adoption of the WI. Occasionally other groups may be given responsibility for the service requirements. This might be another TB-SG, e.g. a Task Force. In any case, however, it should be a single group and one that reports directly to the TB.
System/Architectural requirements and implications:
Also, the responsibility for system/architectural requirements should be allocated immediately, even though the implications and requirements normally will be seen only after the study on service/system requirements have been initiated. The responsibility for the system/architectural requirements must be given to a single body to guarantee the consistency of the adopted solution.
The choice of group should not [pre-]determine the technical choices and in many cases, the responsibility for system and architectural requirement study needs a widening of the competency and a readiness to look to a variety of technical aspects. This can be obtained either by drawing the attraction of the suitable experts (e.g., by setting special meetings or clear meeting dates) or by the organisation of joint meetings.
The overall consistency of the system architecture must be maintained along with the numerous modifications due to various work items. This responsibility is allocated to the TB SG on system/architecture (SMG 12) which for this purpose ensures the co-ordination of the development of general architecture concepts and their applications to individual Work Items, and should thus also draw attention and expertise from other TBs and TB SGs as well.
Protocol specifications:
The responsibility for the elaboration of the protocol specifications can in most cases not be allocated at the early stages since it depends on the technical implementation choices and hence on the results of the study of the service/system requirements as well as on the architectural conclusions.
The identification of new protocols to be specified and/or existing protocols to enhance will be derived from the system/architectural requirements. In general, modifications of existing protocols are done by the TB SG in charge of the protocol in question, whilst the responsibility for development of new protocols is allocated by the TB based on proposals from the TB SG on system/architecture. Then, whether the actual work is done in the TB SG itself or in an ad hoc subgroup thereof is at the discretion of that TB SG.
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