1、 ETSI TR 123 919 V15.0.0 (2018-06) Digital cellular telecommunications system (Phase 2+) (GSM); Universal Mobile Telecommunications System (UMTS); LTE; Direct tunnel deployment guideline (3GPP TR 23.919 version 15.0.0 Release 15) TECHNICAL REPORT ETSI ETSI TR 123 919 V15.0.0 (2018-06)13GPP TR 23.919
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9、V15.0.0 (2018-06)23GPP TR 23.919 version 15.0.0 Release 15Intellectual Property Rights Essential patents IPRs essential or potentially essential to normative deliverables may have been declared to ETSI. The information pertaining to these essential IPRs, if any, is publicly available for ETSI member
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13、nd/or tradename. Mention of those trademarks in the present document does not constitute an endorsement by ETSI of products, services or organizations associated with those trademarks. Foreword This Technical Report (TR) has been produced by ETSI 3rd Generation Partnership Project (3GPP). The presen
14、t document may refer to technical specifications or reports using their 3GPP identities, UMTS identities or GSM identities. These should be interpreted as being references to the corresponding ETSI deliverables. The cross reference between GSM, UMTS, 3GPP and ETSI identities can be found under http:
15、/webapp.etsi.org/key/queryform.asp. Modal verbs terminology In the present document “should“, “should not“, “may“, “need not“, “will“, “will not“, “can“ and “cannot“ are to be interpreted as described in clause 3.2 of the ETSI Drafting Rules (Verbal forms for the expression of provisions). “must“ an
16、d “must not“ are NOT allowed in ETSI deliverables except when used in direct citation. ETSI ETSI TR 123 919 V15.0.0 (2018-06)33GPP TR 23.919 version 15.0.0 Release 15Contents Intellectual Property Rights 2g3Foreword . 2g3Modal verbs terminology 2g3Foreword . 4g31 Scope 5g32 References 5g33 Abbreviat
17、ions . 5g34 Direct Tunnel Feature . 5g34.1 General . 5g35 Impacts on Functions and Characteristics 6g35.1 Charging . 6g35.2 Lawful Interception 6g35.3 CAMEL 6g35.4 Error Handling 6g36 Impacts on 3GPP Network Entities, Features and Transport Network 7g36.1 SGSN 7g36.2 GGSN . 7g36.3 RNC 8g36.4 IP Back
18、bone Network 8g36.5 IP versions 8g36.6 QoS Architecture 9g37 Limitations of Direct Tunnel Solution . 9g38 Upgrade considerations 9g38.1 Interworking with Pre-DT GGSN 9g38.2 Interworking with Pre-DT SGSN . 9g38.3 Interworking with Pre-Rel-7 RNC . 10g3Annex A: Change history 11g3History 12g3ETSI ETSI
19、TR 123 919 V15.0.0 (2018-06)43GPP TR 23.919 version 15.0.0 Release 15Foreword This Technical Report has been produced by the 3rdGeneration Partnership Project (3GPP). The contents of the present document are subject to continuing work within the TSG and may change following formal TSG approval. Shou
20、ld 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.z where: x the first digit: 1 presented to TSG for information; 2 presented to TSG for approval; 3 or greater
21、 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 document. ETSI ETSI TR 123 919 V15
22、.0.0 (2018-06)53GPP TR 23.919 version 15.0.0 Release 151 Scope The present document contains deployment guidelines for the use of direct tunnelling of user plane data between the RNC and the GGSN (earlier known as the One Tunnel approach). This report highlights the impacts of the 3GPP Release 7 Dir
23、ect Tunnel solution to the current UMTS system in order to guide equipment development and network deployment. 2 References The following documents contain provisions which, through reference in this text, constitute provisions of the present document. - References are either specific (identified by
24、 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. In the case of a reference to a 3GPP document (including a GSM document), a non-specific reference i
25、mplicitly refers to the latest version of that document in the same Release as the present document. 1 3GPP TS 23.060: “General Packet Radio Service (GPRS); Service description; Stage 2“. 2 3GPP TS 23.107: “ Quality of Service (QoS) concept and architecture“. 3 3GPP TS 23.203: “Policy and charging c
26、ontrol architecture“. 4 3GPP TS 33.106: “Lawful interception requirements“. 5 3GPP TS 33.107: “3G security; Lawful interception architecture and functions“. 6 3GPP TS 33.108: “3G security; Handover interface for Lawful Interception (LI)“. 3 Abbreviations For the purposes of the present document, the
27、 following abbreviations apply: DT Direct Tunnel LI Lawful Interception 4 Direct Tunnel Feature 4.1 General Direct Tunnel is an optional feature in Iu mode that allows the SGSN to establish a direct user plane tunnel between RAN and GGSN within the PS domain. The SGSN handles the control plane signa
28、lling and makes the decision when to establish a Direct Tunnel. In case of Direct Tunnel, the SGSN provides the RAN with the TEID and user plane address of the GGSN, and provides the GGSN with the TEID and user plane address of the RAN. The detailed procedures are specified in TS 23.060 1. ETSI ETSI
29、 TR 123 919 V15.0.0 (2018-06)63GPP TR 23.919 version 15.0.0 Release 15Figure 4-1: Direct Tunnel concept 5 Impacts on Functions and Characteristics 5.1 Charging When a Direct Tunnel is active, the SGSN will no longer be able to count data volumes associated with the PDP context for which the Direct T
30、unnel is established. As a result of activating a Direct Tunnel for a specific PDP context, an inconsistency in the data volumes captured by the SGSN and GGSN will arise for that PDP context. Hence, if Direct Tunnel is active, volume based charging can no longer operate when relying on SGSN charging
31、 information alone (e.g. CAMEL pre-paid service or charging only on S-CDRs). During an upgrade phase when there exist Pre-DT GGSN or Pre-DT RNC in the network there may in some error situations as described in clause 8 occur a discrepancy in CDR closure time between S-CDRs and G-CDRs. However, no im
32、pacts on flow based charging, as defined in TS 23.203 3, are foreseen. 5.2 Lawful Interception If a Direct Tunnel is in use, the LI system can only collect the communication content from the GGSN. When the LI function in the GGSN is used, some control plane related information, such as SMS and MM-re
33、lated information can only be collected from the SGSN. Details for LI are specified in following documents: TS 33.106 4, TS 33.107 5, and TS 33.108 6. 5.3 CAMEL Direct Tunnel is not enabled for a subscriber that has controlling PS domain CAMEL services active. 5.4 Error Handling With the Rel-7 Direc
34、t Tunnel feature, the GTP-U related error handling has been slightly changed in the GGSN and RNC. For the Error Handling function to work fully correctly, the GGSN and RNC need to be upgraded to support Direct Tunnel. During a deployment phase, the Direct Tunnel feature may however be used without t
35、he GGSN and/or the RNC being upgraded. The shortcomings and issues related with this are mainly that the network may experience hanging PDP contexts or inconsistent PDP context data in some rare error cases, e.g. at node failures or restarts. This is further explained in clause 8. ETSI ETSI TR 123 9
36、19 V15.0.0 (2018-06)73GPP TR 23.919 version 15.0.0 Release 156 Impacts on 3GPP Network Entities, Features and Transport Network 6.1 SGSN The main principle is that whenever a RAB is assigned for a PDP context (or re-assigned) the SGSN decides whether to use a direct user plane tunnel between RNC and
37、 GGSN, or, if it needs to handle user plane data and use two tunnels as in earlier 3GPP releases. Further, when a Direct Tunnel was in use and the RAB assigned for a PDP context is released (i.e. the PDP context is preserved) the GTP-U tunnel is (re)established between the GGSN and SGSN in order to
38、be able to handle the downlink packets. The SGSN needs to decide before every RAB assignment and every SRNS relocation if direct tunnel will be used or not. Figure 6-1: Connected mode and Idle mode handling In the Intra SGSN Inter-system Change procedure from 3G to 2G, the SGSN needs to perform a PD
39、P Context Update Procedure to establish the tunnel between the 2G SGSN and the GGSN and release the Direct Tunnel between RNC and GGSN. In the Intra SGSN Inter-system Change procedure from 2G to 3G, the SGSN provides to the RNC the GGSNs Address(es) for User Plane and TEID(s) for Uplink data in the
40、RAB Assignment Request during the Service Request Procedure. Then the SGSN performs a PDP Context Update Procedure to establish the Direct Tunnel between the RNC and the GGSN and release the tunnel between SGSN and GGSN. Toggling between 2G and 3G might (or might not) be frequent. This may effect th
41、e Gn signalling when Direct Tunnel is deployed. It is implementation specific how this is addressed. 6.2 GGSN In order to inform the GGSN of the IP address of the RNC and the TEID for the active PDP context, the SGSN will send an Update PDP Context Request message to the GGSN during every PDP Contex
42、t Activation procedure for which a Direct Tunnel is established. This message, which is an optional message in two-tunnel system, increases the signalling load on SGSN and GGSN. RAB release and re-establishment procedures, which become visible to the GGSN in a Direct Tunnel system, also increase the
43、 signalling load on SGSN and GGSN. If the radio-link is bad, and the RNC releases the Iu connection, the frequent RAB release and re-establishment increases the signalling load on SGSN and GGSN. One consequence is that it is useful if the RNC utilises URA-PCH state. Some Intra SGSN procedures, such
44、as Intra SGSN inter RNC, Intra SGSN Inter-system change, and possibly other procedures, which are invisible to the GGSN in two-tunnel system, will become visible to the GGSN and increase the signalling load on both SGSN and GGSN. Receipt of the Direct Tunnel Indicator makes the GGSN aware that the S
45、GSN is using a Direct Tunnel. ETSI ETSI TR 123 919 V15.0.0 (2018-06)83GPP TR 23.919 version 15.0.0 Release 15When using Direct Tunnel, if the GGSN receives a GTP-U Error Indication (from the RNC) it shall not release the related PDP context locally but the GGSN shall notify the SGSN that the RAB in
46、RAN is invalid. This needs the GGSN to be updated. NOTE: During a deployment phase, the Direct Tunnel feature may however be used without the GGSN being upgraded. This is further explained in clause 8.1. If, when using two tunnels transport network QoS was used on Iu-PS but not on Gn then moving to
47、Direct Tunnel requires the GGSN to implement transport network QoS. 6.3 RNC RNCs that only support ATM transport should support IP transport for the Iu-PS interface. Alternatively a solution as described below in clause 6.4 can be used. Due to this Direct Tunnel feature, the Error Handling Behaviour
48、 of Rel-7 RNC is changed. NOTE: During a deployment phase, the Direct Tunnel feature may however be used without the RNC being upgraded. This is further explained in clause 8.3. If, when using two tunnels transport network QoS was used on Gn but not on Iu-PS then moving to Direct Tunnel requires the
49、 RNC to implement transport network QoS. 6.4 IP Backbone Network Within the network area where Direct Tunnel is used, the Iu-PS and Gn transport networks must be made visible to each other, this is a network configuration issue. This is minor security drawback. The risk could be reduced by using firewall between Iu-PS and Gn networks instead of simple router (this might impact user-plane latency). Only IP traffic to predefined IP-addresses/ports from predefined addresses/ports would be allowed between Iu-PS and Gn networks. Considering network security,
