1、3GPP TR 23.894 V0.6.0 (2008-11)Technical Report3rd Generation Partnership Project;Technical Specification Group Services and System Aspects;System enhancements for the use of IMS services in local breakout and optimal routing of media(Release 8)The present document has been developed within the 3rd
2、Generation Partnership Project (3GPP TM) and may be further elaborated for the purposes of 3GPP.The present document has not been subject to any approval process by the 3GPP Organizational Partners and shall not be implemented. This Specification is provided for future development work within 3GPP o
3、nly. The Organizational Partners accept no liability for any use of this Specification.Specifications and reports for implementation of the 3GPP TM system should be obtained via the 3GPP Organizational Partners Publications Offices.3GPP3GPP TR 23.894 V0.6.0 (2008-11)2Release 8Keywords3GPP, Architect
4、ure, SAE3GPPPostal address3GPP support office address650 Route des Lucioles Sophia AntipolisValbonne FRANCETel.: +33 4 92 94 42 00 Fax: +33 4 93 65 47 16Internethttp:/www.3gpp.orgCopyright NotificationNo part may be reproduced except as authorized by written permission.The copyright and the foregoin
5、g restriction extend to reproduction in all media. 2007, 3GPP Organizational Partners (ARIB, ATIS, CCSA, ETSI, TTA, TTC).All rights reserved.3GPP3GPP TR 23.894 V0.6.0 (2008-11)3Release 8ContentsForeword .5Introduction.51 Scope.62 References.73 Definitions, symbols and abbreviations73.1 Definitions .
6、73.2 Symbols .73.3 Abbreviations.74 Overall Requirements .85 Architectural Requirements and Assumptions .86 Scenarios and Solutions for local breakout.96.1 Scenarios96.1.1 P-CSCF located in home network dual IP address .96.1.2 P-CSCF located in home network single IP address 106.1.3 P-CSCF located i
7、n serving network.116.2 Alternative 1: Dual IP address.116.2.1 Description.116.2.2 Impact on IMS .146.2.3 Impact on EPS146.2.4 Impact on UE .156.3 Alternative 2 156.5 Comparison of the scenarios157 Scenarios and Solutions for optimal routing of media .157.1 Scenarios157.2 Extension to SDP for TrGW b
8、ypass167.2.1 Introduction167.2.2 Reference Architecture 177.2.3 Description of base algorithm187.2.3.1 Overview 187.2.3.2 Procedures and call flows.197.2.3.2.1 Example flow for base algorithm .197.2.4 Description of active bypass option.207.2.4.1 Overview of Operation of the Active-Bypass Option207.
9、2.4.2 Example flow for Active Bypass Option .218 Evaluation of the Solutions.228.1 Evaluation Criteria.228.2 Evaluation Results .228.2.1 Relationship between local breakout and optimal media routing 229 Conclusions.239.1 Conclusion on LBO dual IP address solutions 23Annex A: OMR use cases .24A.1 Dis
10、cussion24A.2 Common Transit Network .24A.3 Common Serving Network26A.4 Two Transit Networks (1) .28A.5 Two Transit Networks (2) .29A.5.1 Two Transit Networks (2) Example optimization 29A.5.2 Two Transit Networks (2) Alternative optimizations .30A.6 Four transit networks .31A.7 User performs SC 323GP
11、P3GPP TR 23.894 V0.6.0 (2008-11)4Release 8A.8 User splits media across access networks33A.9 Media server in Home A .34A.10 No Transit networks 35Annex B: Interconnect Assumptions 36B.1 Direct Interconnects.36B.2 In-direct Inter-connects36B.2.1 Interconnection over “Internets“ 36B.2.2 Interconnection
12、s over IPX networks36B.2.2.1 General .36B.2.2.2 Transport mode 37B.2.2.3 Service transparent mode: 37B.2.2.4 Hubbing mode 37B.2.2.5 Roaming Interconnections38B.2.3 Interconnection using IMS transit functionality 38B.2 Actions at Interconnects that may affect OMR .38B.2.1 General.38B.2.2 Security 38B
13、.2.3 Charging.38B.2.4 QoS Monitoring .38Annex C: Change history 403GPP3GPP TR 23.894 V0.6.0 (2008-11)5Release 8ForewordThis Technical Report has been produced by the 3rd Generation Partnership Project (3GPP).The contents of the present document are subject to continuing work within the TSG and may c
14、hange following formal TSG approval. Should the TSG modify the contents of the present document, it will be re-released by the TSG with an identifying change of release date and an increase in version number as follows:Version x.y.zwhere:x the first digit:1 presented to TSG for information;2 present
15、ed to TSG for approval;3 or greater indicates TSG approved document under change control.Y the second digit is incremented for all changes of substance, i.e. technical enhancements, corrections, updates, etc.z the third digit is incremented when editorial only changes have been incorporated in the d
16、ocument.IntroductionDue to the increasing volume of data traffic exchanged by mobile users and the rapid decrease of roaming rates that is being imposed by the regulator, mobile operators will most likely have to revisit their roaming agreements, moving towards a more extensive usage of local breako
17、ut. This will allow to reduce the cost per bit of data traffic exchanged by roaming customers, since at least part of it will be handled directly by the visited operator, with no need to waste bandwidth on the international links between home and visited networks; moreover, local breakout would allo
18、w to offer better performance to the customers.Based on the analysis of the requirements on local breakout and on the increasing number of the services controlled by IMS that operators are expected to face, it has been proposed that system enhancements are needed to enable extensive usage of IMS ser
19、vices in local breakout.Furthermore, international communications and terminal roaming introduce a number of scenarios where sessions may traverse multiple IMS networks. The use of Border Control Function makes both the signalling and bearer path traverse through the same networks path and could mak
20、e the media path not optimized.In order to ensure Quality of Service (QoS) and, in certain cases, minimal routing costs, there is a need to enable the routing of media traffic via an optimal path between those networks, without necessarily being linked to the path that the signalling flow needs to t
21、ake. The optimal media path between two endpoints may involve IP transit networks, which in normal circumstances are not included in the SIP signalling path. Current QoS reservation is negotiated based on the SIP pre-conditions model, and hence the lack of SIP signalling in the transit network prese
22、nts a problem for the negotiation of QoS between the end-points.3GPP3GPP TR 23.894 V0.6.0 (2008-11)6Release 81 ScopeThis study intends to investigate the general problem of system enhancements for the use of IMS services in local breakout and optimal routing of media.In particular the above issues w
23、ill be addressed identifying- solutions for the home operator to control - whether the IMS user may connect to a PDN in the visited network, and - whether connections to PDNs provided from the home and visited network may exist in parallel;- solutions to enable the IMS network to be aware of whether
24、 local breakout can be invoked or not; - solutions to allow the home operator to determine which of the IMS sessions (for a given UE) can be handled in local breakout and which in home routed mode, and what information (e.g. operators policies, customers subscription profile, UE connectivity, and lo
25、cation of the remote end terminal/service) is needed for the decision;- solutions to allow the UE to concurrently use IMS services through local breakout and other IMS services through home routing;- the feasibility of having the local breakout option in IMS service nodes:- is there a need for a P-C
26、SCF at both PDN accesses?- if one P-CSCF is enough, what requirements are there for connectivity between the PDNs?- if methods are necessary to discover an additional P-CSCF in the visited network after the UE has moved to the visited network, even if the network-layer mobility mechanisms can sustai
27、n IP connectivity to the previously discovered P-CSCF in the home network;- the exact location of the decision point in the home network whether to use local breakout (application or delegated to IP-CAN);- solutions for SIP/SDP signalling related to the use of IMS services through local breakout.- i
28、nteractions with network entities such as NAT (as specified in TS 23.228) when providing IMS services through local breakout;- interactions with and support of PCC to provide IMS services through local breakout;- security implications if there is need for multiple P-CSCFs per UE.Moreover- describing
29、 a set of scenarios where the selection of an alternative media path (i.e., different to the signalling path) provides benefits to IMS operators by reducing the number of network entities in the media path; - providing requirements for suitable mechanisms to achieve optimal media routing;- analysing
30、 the potential solution(s) to solve those scenarios in line with IMS procedures, while taking into account any impact of extensions required to existing functions/procedures (e.g., NAT, transcoding, Security, PCC, BCF, LI, etc.);- reducing the number of options for solving the same requirement and a
31、gree on a preferred solution.In the end this study will provide conclusions with respects to what further specification work is required in order to fulfil the requirements for the use of IMS services through local breakout and achieve optimal routing of media.3GPP3GPP TR 23.894 V0.6.0 (2008-11)7Rel
32、ease 82 ReferencesThe 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, subse
33、quent revisions do not apply. For a non-specific reference, the latest version applies. In the case of a reference to a 3GPP document (including a GSM document), a non-specific reference implicitly refers to the latest version of that document in the same Release as the present document.1 3GPP TR 21
34、.905: “Vocabulary for 3GPP Specifications“.2 3GPP TS 22.258: “Service requirements for the AIPN”.3 3GPP TS 22.278: “Service requirements for evolution of the 3GPP system”.4 3GPP TS 23.401: “GPRS enhancements for E-UTRAN access“5 3GPP TS 23.402: “Architecture enhancements for non-3GPP accesses“6 3GPP
35、 TS 23.203: “Policy and charging control architecture“.7 GSMA PRD IR.34 “Inter-Service Provider IP Backbone Guidelines”8 3GPP TS 23.228: “IP Multimedia Subsystem (IMS)”3 Definitions, symbols and abbreviations3.1 DefinitionsFor the purposes of the present document, the following definitions apply. IP
36、 gateway: The node in the operators network that is responsible for allocating an IP address to a subscriber.3.2 SymbolsFor the purposes of the present document, the following symbols apply:3.3 AbbreviationsFor the purposes of the present document, the abbreviations given in TR 21.905 1 and the foll
37、owing apply. An abbreviation defined in the present document takes precedence over the definition of the same abbreviation, if any, in TR 21.905 1.EPC Evolved Packet CoreEPS Evolved Packet SystemGW GateWayIP Internet ProtocolP-CSCF Proxy-Call Session Control FunctionSDP Session Description ProtocolU
38、E User Equipment3GPP3GPP TR 23.894 V0.6.0 (2008-11)8Release 8LBO Local BreakoutOMR Optimal Media Routing4 Overall Requirements The overall requirements to provide IMS services through local breakout are defined in 3GPP TS 23.401 4.Editors Note: Requirements for optimal routing of media need to be ad
39、ded.Editors Note: Additional requirements may be added as the study work progresses.5 Architectural Requirements and AssumptionsThe following general architecture principles shall be used when developing solutions for LBO and OMR:- Radio impacts/Access network procedures like IDLE mobility should no
40、t be affected;- S-CSCF is the service control entity for IMS, as per current IMS core principle; even though media may be routed according to LBO or OMR procedures; (except for emergency case where E-CSCF is used as described in TS 23.167);- Backward compatibility with Rel-7 (e.g. Rel-8 Terminal sha
41、ll be able to connect to a Rel-7 IMS system and Rel-7 terminal shall be able to connect to Rel-8 IMS) shall be maintained and impacts from the development within Rel-8 IMS system shall be addressed before reaching final conclusion;- UE battery consumption and complexity/cost of impacts must be consi
42、dered;- An UE shall not use the same IP address simultaneously across multiple accesses;- Any solution(s) developed should work in single PLMN scenario as well as roaming scenarios.Editors note: Current IMS sessions between two or more end points are based on the HPLMN roaming agreements. In case of
43、 media routed via different PLMN than signaling traffic, where is the decision responsibility regarding operator agreements on charging, roaming, SLA etc.?In addition to the general requirements above, the following requirements shall be used when developing solutions for Optimal Media Routing (OMR)
44、:- OMR shall apply to IMS systems that use IBCF and TrGW for interconnection.- OMR shall establish an optimal media path for each of the media streams of an IMS session, subject to the Home operators policy, system constraints (such as transcoding function location) and the information available wit
45、hin SIP signalling;- All media components of a session that traverse the same un-optimized sequence of IBCFs/TrGWs and networks shall, subject to Home operators policy, traverse the same optimized sequence of IBCFs/TrGWs and networks. This ensures similar end to end path delay characteristics for me
46、dia components that may be synchronized;- Where end points are located within the same residence or enterprise network, OMR should be able to support the routing of the media path such that it does not egress that network;- OMR should be capable of optimizing the media paths for a session where the
47、same interconnect network is used for multiple legs of the un-optimized media path;- OMR should be capable of optimizing the media paths for a session between two UEs where the same serving network is used by the UEs;3GPP3GPP TR 23.894 V0.6.0 (2008-11)9Release 8- Home operators (of both calling and
48、called UE) may be informed, upon session establishment/modification, of the successful enforcement or removal of OMR for that session;- On session establishment, OMR shall establish an optimal media path separately for each remote endpoint of the session;- OMR should re-establish an optimal media pa
49、th for a session in the event of session modification (SDP offer/answer exchange);- Impacts on IMS shall be minimized. Solutions should be based on existing IMS functional entities, use existing message flows and avoid the addition of new protocols or new messages between network elements;- A single bandwidth reservation mechanism shall be used (for both roaming and non-roaming cases and for optimized and non-optimized sessions);- Entities in one network shall not need to be aware of the internal structure of other networks;- The routing of media
