1、 INTERNATIONAL TELECOMMUNICATION UNION ITU-T Q.2920TELECOMMUNICATION STANDARDIZATION SECTOR OF ITU (12/2003) SERIES Q: SWITCHING AND SIGNALLING Broadband ISDN B-ISDN application protocols for access signalling Broadband integrated services digital network (B-ISDN) Digital Subscriber Signalling Syste
2、m No. 2 (DSS 2): Call/connection control for the support of ATM-MPLS network interworking ITU-T Recommendation Q.2920 ITU-T Q-SERIES RECOMMENDATIONS SWITCHING AND SIGNALLING SIGNALLING IN THE INTERNATIONAL MANUAL SERVICE Q.1Q.3 INTERNATIONAL AUTOMATIC AND SEMI-AUTOMATIC WORKING Q.4Q.59 FUNCTIONS AND
3、 INFORMATION FLOWS FOR SERVICES IN THE ISDN Q.60Q.99 CLAUSES APPLICABLE TO ITU-T STANDARD SYSTEMS Q.100Q.119 SPECIFICATIONS OF SIGNALLING SYSTEMS No. 4, 5, 6, R1 AND R2 Q.120Q.499 DIGITAL EXCHANGES Q.500Q.599 INTERWORKING OF SIGNALLING SYSTEMS Q.600Q.699 SPECIFICATIONS OF SIGNALLING SYSTEM No. 7 Q.7
4、00Q.799 Q3 INTERFACE Q.800Q.849 DIGITAL SUBSCRIBER SIGNALLING SYSTEM No. 1 Q.850Q.999 PUBLIC LAND MOBILE NETWORK Q.1000Q.1099 INTERWORKING WITH SATELLITE MOBILE SYSTEMS Q.1100Q.1199 INTELLIGENT NETWORK Q.1200Q.1699 SIGNALLING REQUIREMENTS AND PROTOCOLS FOR IMT-2000 Q.1700Q.1799 SPECIFICATIONS OF SIG
5、NALLING RELATED TO BEARER INDEPENDENT CALL CONTROL (BICC) Q.1900Q.1999 BROADBAND ISDN Q.2000Q.2999 General aspects Q.2000Q.2099 Signalling ATM adaptation layer (SAAL) Q.2100Q.2199 Signalling network protocols Q.2200Q.2299 Common aspects of B-ISDN application protocols for access signalling and netwo
6、rk signalling and interworking Q.2600Q.2699 B-ISDN application protocols for the network signalling Q.2700Q.2899 B-ISDN application protocols for access signalling Q.2900Q.2999 For further details, please refer to the list of ITU-T Recommendations. ITU-T Rec. Q.2920 (12/2003) i ITU-T Recommendation
7、Q.2920 Broadband integrated services digital network (B-ISDN) Digital Subscriber Signalling System No. 2 (DSS 2): Call/connection control for the support of ATM-MPLS network interworking Summary MPLS has the potential to consolidate service provider networks and services over a single common network
8、 core infrastructure. Different services and technologies such as ATM, frame relay, circuit emulation and IP can be supported over MPLS networks. DSS 2 may be used for setting up and controlling ATM connections between two ATM/MPLS network nodes attached to an MPLS network. Extensions to DSS 2 infor
9、mation elements and procedures are defined to allow the exchange of MPLS LSP labels and other parameters specific to support ATM services over MPLS networks. Source ITU-T Recommendation Q.2920 was approved on 22 December 2003 by ITU-T Study Group 11 (2001-2004) under the ITU-T Recommendation A.8 pro
10、cedure. Keywords ATM, control plane, interworking, MPLS, network. ii ITU-T Rec. Q.2920 (12/2003) FOREWORD The International Telecommunication Union (ITU) is the United Nations specialized agency in the field of telecommunications. The ITU Telecommunication Standardization Sector (ITU-T) is a permane
11、nt organ of ITU. ITU-T is responsible for studying technical, operating and tariff questions and issuing Recommendations on them with a view to standardizing telecommunications on a worldwide basis. The World Telecommunication Standardization Assembly (WTSA), which meets every four years, establishe
12、s the topics for study by the ITU-T study groups which, in turn, produce Recommendations on these topics. The approval of ITU-T Recommendations is covered by the procedure laid down in WTSA Resolution 1. In some areas of information technology which fall within ITU-Ts purview, the necessary standard
13、s are prepared on a collaborative basis with ISO and IEC. NOTE In this Recommendation, the expression “Administration“ is used for conciseness to indicate both a telecommunication administration and a recognized operating agency. Compliance with this Recommendation is voluntary. However, the Recomme
14、ndation may contain certain mandatory provisions (to ensure e.g. interoperability or applicability) and compliance with the Recommendation is achieved when all of these mandatory provisions are met. The words “shall“ or some other obligatory language such as “must“ and the negative equivalents are u
15、sed to express requirements. The use of such words does not suggest that compliance with the Recommendation is required of any party. INTELLECTUAL PROPERTY RIGHTS ITU draws attention to the possibility that the practice or implementation of this Recommendation may involve the use of a claimed Intell
16、ectual Property Right. ITU takes no position concerning the evidence, validity or applicability of claimed Intellectual Property Rights, whether asserted by ITU members or others outside of the Recommendation development process. As of the date of approval of this Recommendation, ITU had not receive
17、d notice of intellectual property, protected by patents, which may be required to implement this Recommendation. However, implementors are cautioned that this may not represent the latest information and are therefore strongly urged to consult the TSB patent database. ITU 2004 All rights reserved. N
18、o part of this publication may be reproduced, by any means whatsoever, without the prior written permission of ITU. ITU-T Rec. Q.2920 (12/2003) iii CONTENTS Page 1 Scope 1 2 References. 1 3 Definitions 2 4 Abbreviations 2 5 Description 3 5.1 Reference network architecture 3 5.2 Transport and Interwo
19、rking LSP 3 5.3 Encapsulating ATM VCCs or VPCs into MPLS packets 4 5.4 Establishment and maintenance of LSPs 4 5.5 Signalling channel Interworking LSP 4 6 Operational requirements 4 7 Primitives 5 8 Coding requirements. 5 8.1 Messages. 5 8.2 Information elements coding 6 9 Procedures for the support
20、 of ATM-MPLS network interworking 10 9.1 Interworking label exchange and VPCI/VCI allocation. 10 9.2 Indication and negotiation of Encapsulation mode 11 9.3 Call/connection clearing procedure 13 9.4 Restart procedures 13 BIBLIOGRAPHY 14 ITU-T Rec. Q.2920 (12/2003) 1 ITU-T Recommendation Q.2920 Broad
21、band integrated services digital network (B-ISDN) Digital Subscriber Signalling System No. 2 (DSS 2): Call/connection control for the support of ATM-MPLS network interworking 1 Scope This Recommendation specifies extensions to the Digital Subscriber Signalling System No. 2 (DSS 2) protocol to allow
22、the use of DSS 2 between two ATM/MPLS network equipments being connected via a Multi-Protocol Label Switching (MPLS) network as specified in ITU-T Recs Y.1411 and Y.1412. This Recommendation addresses the role of ATM signalling to establish Interworking LSPs between IWFs (Interworking Functions) dur
23、ing ATM VCC or VPC establishment and to perform related signalling functions. This Recommendation is part of the DSS 2 family of ITU-T Recommendations. It specifies extensions to DSS 2 Recommendations and does not repeat states, information elements, messages and procedures contained therein. DSS 2
24、extensions defined in this Recommendation are limited to point-to-point connections. Point-to-multipoint connections may be considered in the future. This Recommendation is applicable to equipment, supporting DSS 2 signalling capabilities as defined, in particular, in ITU-T Recs Q.2931, Q.2934 and o
25、ther DSS 2-related Recommendations. TRQ.2830 1 provides the signalling requirements for the support of ATM-MPLS network interworking. 2 References The following ITU-T Recommendations and other references contain provisions which, through reference in this text, constitute provisions of this Recommen
26、dation. At the time of publication, the editions indicated were valid. All Recommendations and other references are subject to revision; users of this Recommendation are therefore encouraged to investigate the possibility of applying the most recent edition of the Recommendations and other reference
27、s listed below. A list of the currently valid ITU-T Recommendations is regularly published. The reference to a document within this Recommendation does not give it, as a stand-alone document, the status of a Recommendation. ITU-T Recommendation Y.1411 (2003), ATM-MPLS network interworking Cell mode
28、user plane interworking. ITU-T Recommendation Y.1412 (2003), ATM-MPLS network interworking Frame mode user plane interworking. ITU-T Recommendation Q.2931 (1995), Digital Subscriber Signalling System No. 2 User-Network Interface (UNI) layer 3 specification for basic call/connection control. ITU-T Re
29、commendation Q.2934 (1998), Digital Subscriber Signalling System No. 2 Switched virtual path capability. ITU-T Recommendation Q.2610 (1999), Usage of cause and location in B-ISDN user part and DSS 2. 2 ITU-T Rec. Q.2920 (12/2003) 3 Definitions This Recommendation defines the following terms: 3.1 bac
30、kward LSP: A Transport or Interworking LSP carrying the traffic in the backward call direction from the succeeding IWF to the preceding IWF. 3.2 cell concatenation: See ITU-T Rec. Y.1411. 3.3 forward LSP: A Transport or Interworking LSP carrying the traffic in the forward call direction from the pre
31、ceding IWF to the succeeding IWF. 3.4 interworking LSP: See ITU-T Rec. Y.1411. 3.5 interworking: See ITU-T Rec. Y.1411. 3.6 interworking LSP label: See ITU-T Rec. Y.1411. 3.7 preceding IWF: The IWF initiating the establishment of an ATM VCC or VPC within an Interworking LSP. 3.8 succeeding IWF: The
32、IWF receiving a request to establish an ATM VCC or VPC within an Interworking LSP. 3.9 transport LSP: See ITU-T Rec. Y.1411. 4 Abbreviations This Recommendation uses the following abbreviations: AAL ATM Adaptation Layer ATM Asynchronous Transfer Mode B-ISDN Broadband Integrated Services Digital Netw
33、ork CII Common Interworking Indicators CPCS Common Part Convergence Sub-layer DSS 2 Digital Subscriber Signalling System No. 2 IE Information Element I-LSP Interworking LSP IWF InterWorking Function LSP Label Switched Path LSR Label Switching Router MPLS Multi-Protocol Label Switching PHY Physical S
34、AAL Signalling ATM Adaptation Layer SSCF Service Specific Convergence Function SSCOP Service Specific Connection Oriented Protocol T-LSP Transport LSP UNI User-Network Interface VCC Virtual Channel Connection VPC Virtual Path Connection ITU-T Rec. Q.2920 (12/2003) 3 5 Description 5.1 Reference netwo
35、rk architecture A general ATM-MPLS network interworking reference architecture is provided in ITU-T Rec. Y.1411 and is reproduced in Figure 1. It consists of the following main elements: an MPLS core network consisting of MPLS nodes; preceding and succeeding IWFs; ATM switches or nodes; ATM users. Q
36、.2920_F01MPLSEnd System 1ATMIWFATMMPLSEnd System 2ATMLSR LSPATMIWFMPLSFigure 1/Q.2920 Reference network architecture for ATM-MPLS network interworking 5.2 Transport and Interworking LSP From an ATM signalling perspective, the MPLS network and Transport LSPs can be considered as an abstraction of a p
37、hysical link established between two ATM nodes. Figure 2 captures this view. For information regarding cell and frame mode encapsulations into MPLS packets, refer to ITU-T Recs Y.1411 and Y.1412 respectively. Q.2920_F02 MPLS NetworkNetwork nodewith IWFNetwork nodewith IWFATMnodeATMnodeATMnodeATMnode
38、ATMnodeATMnodeIWF IWFMPLSMPLSATMATMTransport LSPTransmission directionI-LSPs carrying User information within T-LSPI-LSPs carrying Sig. CONNECT; RESTART; RESTART ACKNOWLEDGE; SETUP. Changes to the structure of these messages are provided below. 8.1.2 Call proceeding Table 1 provides changes to the s
39、tructure of this message from that shown in Table 3-3/Q.2931. Table 1/Q.2920 Changes to CALL PROCEEDING message content Message type: CALL PROCEEDING Significance: Local Direction: Both Information element Reference Direction Type Length Connection identifier 8.2.1 Both O (Notes 1, 3) 4-14 (Note 4)
40、NOTE 3 Mandatory if this IE is used for ATM-MPLS network interworking. NOTE 4 Increased upper limit for the length of this IE applies for ATM-MPLS network interworking. 8.1.3 Connect Table 2 provides changes to the structure of this message from that shown in Table 3-4/Q.2931. Table 2/Q.2920 Changes
41、 to CONNECT message content Message type: CONNECT Significance: Global Direction: Both Information element Reference Direction Type Length Interworking 8.2.2 Both O (Note 8) 8-14 NOTE 8 Mandatory if this IE is used for ATM-MPLS network interworking. 6 ITU-T Rec. Q.2920 (12/2003) 8.1.4 Restart Table
42、3 provides changes to the structure of this message from that shown in Table 3-22/Q.2931. Table 3/Q.2920 Changes to RESTART message content Message type: RESTART Significance: Local Direction: Both Information element Reference Direction Type Length Connection identifier 8.2.1 Both O (Note 2) 9-14 (
43、Note 3) NOTE 3 Increased limits for the length of this IE apply for ATM-MPLS network interworking. 8.1.5 Restart Acknowledge Table 4 provides changes to the structure of this message from that shown in Table 3-23/Q.2931. Table 4/Q.2920 Changes to RESTART ACKNOWLEDGE message content Message type: RES
44、TART ACKNOWLEDGE Significance: Local Direction: Both Information element Reference Direction Type Length Connection identifier 8.2.1 Both O (Note 2) 9-14 (Note 3) NOTE 3 Increased limits for the length of this IE apply for ATM-MPLS network interworking. 8.1.6 Setup Table 5 provides changes to the st
45、ructure of this message from that shown in Table 3-8/Q.2931. Table 5/Q.2920 Changes to SETUP message content Message type: SETUP Significance: Global Direction: Both Information element Reference Direction Type Length Connection identifier 8.2.1 Both O (Notes 9, 17) 14 (Note 18) Interworking 8.2.2 B
46、oth O (Note 17) 8-59 (Note 19) NOTE 17 Mandatory if this IE is used for ATM-MPLS network interworking. NOTE 18 Increased maximum length for this IE applies for ATM-MPLS network interworking. NOTE 19 Increased upper limit due to the fact that octet group “Encapsulation Id“ may appear six times within
47、 this IE. 8.2 Information elements coding The Connection identifier information element is extended to carry MPLS Interworking label between the two IWFs. A new information element, the Interworking information element, is defined to carry ATM-MPLS network interworking-related parameters. ITU-T Rec.
48、 Q.2920 (12/2003) 7 8.2.1 Connection identifier information element The Connection identifier information element is extended to allow the carriage of the forward or backward Interworking LSP between two IWFs. The new maximum length of the Connection identifier information element is 14 octets. The
49、extensions to the Connection identifier information element (Figure 4-22/Q.2931) are shown in Figures 4 and 5. 8 7 6 5 4 3 2 1 Octet ATM-MPLS network interworking identifier 10* (Note 4) 0 0 0 0 0 0 0 1 ATM-MPLS network interworking length 10.1* ATM-MPLS network interworking value 10.2*-10.4* NOTE 4 Octet group 10 is only present when connection is established over an MPLS interface. Figure 4/Q.2920 Extensions to the Connection identifier information element Preferred/Exclusive field (octet
