1、 INTERNATIONAL TELECOMMUNICATION UNION ITU-T Y.1413TELECOMMUNICATION STANDARDIZATION SECTOR OF ITU (03/2004) SERIES Y: GLOBAL INFORMATION INFRASTRUCTURE, INTERNET PROTOCOL ASPECTS AND NEXT GENERATION NETWORKS Internet protocol aspects Interworking TDM-MPLS network interworking User plane interworkin
2、g ITU-T Recommendation Y.1413 ITU-T Y-SERIES RECOMMENDATIONS GLOBAL INFORMATION INFRASTRUCTURE, INTERNET PROTOCOL ASPECTS AND NEXT GENERATION NETWORKS GLOBAL INFORMATION INFRASTRUCTURE General Y.100Y.199 Services, applications and middleware Y.200Y.299 Network aspects Y.300Y.399 Interfaces and proto
3、cols Y.400Y.499 Numbering, addressing and naming Y.500Y.599 Operation, administration and maintenance Y.600Y.699 Security Y.700Y.799 Performances Y.800Y.899 INTERNET PROTOCOL ASPECTS General Y.1000Y.1099 Services and applications Y.1100Y.1199 Architecture, access, network capabilities and resource m
4、anagement Y.1200Y.1299 Transport Y.1300Y.1399 Interworking Y.1400Y.1499 Quality of service and network performance Y.1500Y.1599 Signalling Y.1600Y.1699 Operation, administration and maintenance Y.1700Y.1799 Charging Y.1800Y.1899 NEXT GENERATION NETWORKS Frameworks and functional architecture models
5、Y.2000Y.2099 Quality of Service and performance Y.2100Y.2199 Service aspects: Service capabilities and service architecture Y.2200Y.2249 Service aspects: Interoperability of services and networks in NGN Y.2250Y.2299 Numbering, naming and addressing Y.2300Y.2399 Network management Y.2400Y.2499 Networ
6、k control architectures and protocols Y.2500Y.2599 Security Y.2700Y.2799 Generalized mobility Y.2800Y.2899 For further details, please refer to the list of ITU-T Recommendations. ITU-T Rec. Y.1413 (03/2004) i ITU-T Recommendation Y.1413 TDM-MPLS network interworking User plane interworking Summary T
7、his Recommendation addresses required functions for network interworking between TDM networks up to DS3 or E3 rates and MPLS networks. This Recommendation addresses user plane interworking mechanisms and procedures. Details of the interworking model and required interworking functions are described.
8、 Source ITU-T Recommendation Y.1413 was approved on 15 March 2004 by ITU-T Study Group 13 (2001-2004) under the ITU-T Recommendation A.8 procedure. Keywords Interworking, MPLS, Network, TDM, user plane. ii ITU-T Rec. Y.1413 (03/2004) FOREWORD The International Telecommunication Union (ITU) is the Un
9、ited Nations specialized agency in the field of telecommunications. The ITU Telecommunication Standardization Sector (ITU-T) is a permanent organ of ITU. ITU-T is responsible for studying technical, operating and tariff questions and issuing Recommendations on them with a view to standardizing telec
10、ommunications on a worldwide basis. The World Telecommunication Standardization Assembly (WTSA), which meets every four years, establishes 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 p
11、rocedure laid down in WTSA Resolution 1. In some areas of information technology which fall within ITU-Ts purview, the necessary standards 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 t
12、elecommunication administration and a recognized operating agency. Compliance with this Recommendation is voluntary. However, the Recommendation may contain certain mandatory provisions (to ensure e.g. interoperability or applicability) and compliance with the Recommendation is achieved when all of
13、these mandatory provisions are met. The words “shall“ or some other obligatory language such as “must“ and the negative equivalents are used to express requirements. The use of such words does not suggest that compliance with the Recommendation is required of any party. INTELLECTUAL PROPERTY RIGHTS
14、ITU draws attention to the possibility that the practice or implementation of this Recommendation may involve the use of a claimed Intellectual Property Right. ITU takes no position concerning the evidence, validity or applicability of claimed Intellectual Property Rights, whether asserted by ITU me
15、mbers or others outside of the Recommendation development process. As of the date of approval of this Recommendation, ITU had received notice of intellectual property, protected by patents, which may be required to implement this Recommendation. However, implementors are cautioned that this may not
16、represent the latest information and are therefore strongly urged to consult the TSB patent database. ITU 2004 All rights reserved. No part of this publication may be reproduced, by any means whatsoever, without the prior written permission of ITU. ITU-T Rec. Y.1413 (03/2004) iii CONTENTS Page 1 Sco
17、pe 1 2 References. 1 3 Definitions 3 4 Abbreviations 3 5 Conventions 4 6 TDM-MPLS interworking 4 7 General requirements 6 7.1 User plane requirements. 6 7.2 Control plane aspects 7 7.3 Fault management aspects 7 7.4 Traffic management aspects. 8 7.5 Connection admission control for the IWF 8 8 Funct
18、ional group considerations for TDM-MPLS network interworking 9 8.1 Transport label 9 8.2 Interworking label 9 8.3 Common interworking indicators. 9 8.4 Optional timing information. 12 9 Payload formats 12 9.1 Structure-agnostic transport 12 9.2 Structure-aware transport . 13 10 Timing aspects 16 10.
19、1 Timing distribution scenarios. 16 11 Packet loss aspects 18 12 Support of CAS and CCS signalling 18 12.1 Support of CAS signalling 18 12.2 Support of CCS signalling 18 13 Security considerations. 18 Appendix I Alternative methods for TDM-MPLS interworking 19 I.1 Use of ITU-T Rec. Y.1411. 19 I.2 Us
20、e of AAL type 2 . 19 Appendix II Optional processing of HDLC-based CCS signals. 19 Appendix III Examples of functional diagrams 20 Appendix IV MPLS network performance metrics 21 IV.1 Errors in the MPLS network that impact TDM service . 22 IV.2 Relationship to TDM service impairment metrics . 22 IV.
21、3 Availability requirements . 23 IV.4 Voice quality requirements. 23 iv ITU-T Rec. Y.1413 (03/2004) Page Appendix V Suggested common clock frequencies for RTP . 23 Appendix VI Suggested payload sizes for structure-agnostic transport . 24 Appendix VII Suggested number of AAL1 SAR PDUs per packet . 24
22、 ITU-T Rec. Y.1413 (03/2004) v Introduction There is a need to define interworking between conventional synchronous or plesiochronous networks (hereafter denoted TDM networks) with MPLS networks. Such interworking must ensure that TDM timing, signalling, voice quality, and alarm integrity be maintai
23、ned. ITU-T Rec. Y.1413 (03/2004) 1 ITU-T Recommendation Y.1413 TDM-MPLS network interworking User plane interworking 1 Scope This Recommendation focuses on required functions for network interworking between TDM and MPLS, specifically the user plane interworking mechanisms and procedures for transpo
24、rt. In particular it specifies a list of requirements, interworking scenarios and interworking encapsulation formats and semantics for TDM-MPLS network interworking. Since TDM connections are inherently point-to-point, this interworking defines a single connection between two IWFs. This Recommendati
25、on only addresses TDM rates up to and including T3 and E3. 2 References The following ITU-T Recommendations and other references contain provisions which, through reference in this text, constitute provisions of this Recommendation. At the time of publication, the editions indicated were valid. All
26、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 references listed below. A list of the currently valid ITU-T Recommendations is regu
27、larly published. The reference to a document within this Recommendation does not give it, as a stand-alone document, the status of a Recommendation. 1 ITU-T Recommendation G.705 (2000), Characteristics of plesiochronous digital hierarchy (PDH) equipment functional blocks. 2 ITU-T Recommendation G.70
28、2 (1988), Digital hierarchy bit rates. 3 ITU-T Recommendation G.704 (1998), Synchronous frame structures used at 1544, 6312, 2048, 8448 and 44 736 kbit/s hierarchical levels. 4 ITU-T Recommendation G.751 (1988), Digital multiplex equipments operating at the third order bit rate of 34 368 kbit/s and
29、the fourth order bit rate of 139 264 kbit/s and using positive justification. 5 ANSI T1.107-2002, Digital Hierarchy, Formats Specification. 6 ETSI TS 100 592 V8.0.0 (2000-06), Digital cellular telecommunications system (Phase 2+) (GSM); Base Station Controller Base Transceiver Station (BSC BTS) inte
30、rface; General aspects. (GSM 08.51 version 8.0.0 Release 1999.) 7 ITU-T Recommendation Y.1411 (2003), ATM-MPLS network interworking Cell mode user plane interworking. 8 IETF RFC 3031 (2001), Multiprotocol Label Switching Architecture. 9 ITU-T Recommendation G.805 (2000), Generic functional architect
31、ure of transport networks. 10 ITU-T Recommendation V.36 (1988), Modems for synchronous data transmission using 60-180 kHz group band circuits. 11 ITU-T Recommendation V.37 (1988), Synchronous data transmission at a data signalling rate higher than 72 kbit/s using 60-108 kHz group band circuits. 12 I
32、TU-T Recommendation I.231.1 (1988), Circuit-mode bearer service categories: Circuit-mode 64 kbit/s unrestricted, 8 kHz structured bearer service. 13 ITU-T Recommendation Q.700 (1993), Introduction to CCITT Signalling System No. 7. 2 ITU-T Rec. Y.1413 (03/2004) 14 ITU-T Recommendation Q.931 (1998), I
33、SDN user-network interface layer 3 specification for basic call control. 15 ITU-T Recommendation G.823 (2000), The control of jitter and wander within digital networks which are based on the 2048 kbit/s hierarchy. 16 ITU-T Recommendation G.824 (2000), The control of jitter and wander within digital
34、networks which are based on the 1544 kbit/s hierarchy. 17 ITU-T Recommendation Y.1711 (2004), Operation in particular those belonging to PDH (plesiochronous digital hierarchy) as described in ITU-T Rec. G.705 1. The bit rates traditionally used in various regions of the world are detailed in ITU-T R
35、ec. G.702 2. 3.2 structured TDM: TDM with any level of structure imposed by a FA (Frame Alignment Signal), such as that defined in 3, 4, 5, or 6. 3.3 unstructured TDM: A TDM bit stream with no structure imposed, so that all bits are available for user data. 3.4 structure-agnostic transport: Transpor
36、t of unstructured TDM, or of structured TDM when the structure is completely disregarded by the transport mechanism. Structure-agnostic transport maintains the precise bit sequence of data and any structure overhead that may be present. The encapsulation provides no mechanisms for the location or ut
37、ilization of a FA. 3.5 structure-aware transport: Transport of structured TDM taking at least some level of the structure into account. In structure-aware transport, it is not required to carry all bits of the TDM bit-stream over the MPLS network; specifically, FAS may be stripped at ingress and reg
38、enerated at egress. 3.6 structure-locked encapsulation: Encapsulation utilized for structure-aware TDM transport where TDM structure boundaries are indicated by packet payload boundaries. 3.7 structure-indicated encapsulation: Encapsulation utilized for structure-aware TDM transport where TDM struct
39、ure boundaries are indicated by pointers. 3.8 TDM segment: Octets extracted from a continuous TDM stream. Each octet in the TDM segment is filled with bits starting from its most significant bit, and octets are placed in the segment in the order received. 3.9 interworking: See ITU-T Rec. Y.1411 7. 3
40、.10 Interworking Function (IWF): See ITU-T Rec. Y.1411 7. 3.11 ingress IWF: The IWF where a continuous TDM stream is segmented and encapsulated into MPLS packets (TDM-to-MPLS direction). 3.12 egress IWF: The IWF where the TDM segments are extracted from MPLS packets and reassembled into a continuous
41、 TDM stream (MPLS-to-TDM direction). 4 Abbreviations This Recommendation uses the following abbreviations: AAL ATM Adaptation Layer AIS Alarm Indication Signal AP Access Point ATM Asynchronous Transfer Mode CAS Channel Associated Signalling CCS Common Channel Signalling CES Circuit Emulation Service
42、 CP Connection Point 4 ITU-T Rec. Y.1413 (03/2004) EXP Experimental Bit FAS Frame Alignment Signal HDLC High level Data Link Control IWF Interworking Function LOF Loss of Frame synchronization LOS Loss of Signal LSP Label Switched Path LSR Label Switching Router MPLS Multi-Protocol Label Switching M
43、TU Maximum Transport Unit OAM Operation and Maintenance PDB Per Domain Behaviour PDU Protocol Data Unit PHB Per Hop Behaviour PM Performance Monitoring PSC PHB Scheduling Class QoS Quality of Service RDI Remote Defect Indication RFC Request for Comments RTP Real Time Protocol SAR Segmentation And Re
44、assembly TCP Termination Connection Point TDM Time Division Multiplex TTL Time to Live 5 Conventions This Recommendation uses traditional terminology for digital signals at the various levels of the G.702 rate hierarchy. In particular, the first level digital signal of rate 2048 kbit/s (P12 in G.705
45、 terminology) is designated E1, and the third level signal of rate 34 368 kbit/s derived from it (P31), E3. Similarly, the first level signal of rate 1544 kbit/s (P11) is designated T1, its second level derivative of rate 6312 kbit/s (P21), T2, and its third level derivative at rate 44 736 kbit/s (P
46、32), T3. 6 TDM-MPLS interworking The multi-protocol label switching (MPLS) technology 8 allows multiple services (such as IP, ATM, frame relay, and TDM) to be supported over a single networking infrastructure. This Recommendation defines interworking with TDM services up to and including T3 or E3 ra
47、tes. Interworking of MPLS with higher rate TDM services, such as SONET/SDH, are beyond the scope of this Recommendation. ITU-T Rec. Y.1413 (03/2004) 5 Figure 6-1 provides a general network architecture for TDM-MPLS network interworking where TDM networks are interconnected through an MPLS network. F
48、or the TDM-to-MPLS direction, the continuous TDM stream is segmented and encapsulated into an MPLS packet by the interworking function (IWF). For the MPLS-to-TDM direction, the TDM segments are extracted from the MPLS packets and the continuous TDM stream is reassembled. Figure 6-2 depicts the netwo
49、rk functional architecture of TDM-MPLS interworking using the diagrammatic techniques of ITU-T Rec. G.805 9. Examples for specific scenarios are given in Appendix III. Figure 6-3 shows the network reference model and protocol layers for TDM-MPLS user plane interworking. Figure 6-1/Y.1413 Reference architecture for TDM-MPLS network interworking Figure 6-2/Y.1413 Functional architecture of TDM-MPLS interworking depicted according to the diagrammatic conventions of ITU-T Rec. G.805 6
