ITU-T G 841-1998 Types and Characteristics of SDH Network Protection Architectures - Series G Transmission Systems and Media Digital Systems and Networks Digital Transmission Systeis.pdf

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1、ITU-T TELECOMMUNICATION STANDARDIZATION SECTOR OF ITU G.841 (I 0/98) SERIES G: TRANSMISSION SYSTEMS AND MEDIA, DIGITAL SYSTEMS AND NETWORKS Digital transmission systems - Digital networks - SDH network characteristics Types and characteristics of SDH network protection architectures ITU-T Recommenda

2、tion G.841 (Previously CCllT Recommendation) ITU-T G-SERIES RECOMMENDATIONS TRANSMISSION SYSTEMS AND MEDIA, DIGITAL SYSTEMS AND NETWORKS Il INTERNATIONAL TELEPHONE CONNECTIONS AND CIRCUITS INTERNATIONAL ANALOGUE CARRIER SYSTEM Il GENERAL CHARACTERISTICS COMMON TO ALL ANALOGUE CARRIER- TRANSMISSION S

3、YSTEMS G.100-G.199 G.200-G.299 Il INDIVIDUAL CHARACTERISTICS OF INTERNATIONAL CARRIER TELEPHONE SYSTEMS ON METALLIC LINES G.300-G.399 I GENERAL CHARACTERISTICS OF INTERNATIONAL CARRIER TELEPHONE G.400-G.449 WITH METALLIC LINES SYSTEMS ON RADIO-RELAY OR SATELLITE LINKS AND INTERCONNECTION For further

4、 details, please refer to ITU-T List of Recommendations. STDnITU-T RECMN G-84L-ENGL L998 48b2591 Obb0797 540 ITU-T RECOMMENDATION G.841 TYPES AND CHARACTERISTICS OF SDH NETWORK PROTECTION ARCHITECTURES Summary This Recommendation provides the necessary equipment-level specifications to implement dif

5、ferent choices of protection architectures for Synchronous Digital Hierarchy (SDH) networks. Protected entities may range from a single SDH multiplex section (e.g. linear multiplex section protection), to a portion of an SDH end-to-end path (e.g. subnetwork connection protection), or to an entire SD

6、H end-to-end path (e.g. HOkO linear VC trail protection). Physical implementations of these protection architectures may include rings or linear chains of nodes. Each protection classification includes guidelines on network objectives, architecture, application functionality, switching criteria, pro

7、tocols, and algorithms. Source ITU-T Recommendation G.841 was revised by ITU-T Study Group 15 (1997-2000) and was approved under the WTSC Resolution No. 1 procedure on the 13th of October 1998. Recommendation G.841 (10/98) 1 FOREWORD ITU (International Telecommunication Union) is the United Nations

8、Specialized Agency in the field of telecommunications. The ITU Telecommunication Standardization Sector (ITU-T) is a permanent organ of the ITU. The ITU-T is responsible for studying technical, operating and tariff questions and issuing Recommendations on them with a view to standardizing telecommun

9、ications on a worldwide basis. The World Telecommunication Standardization Conference (WTSC), which meets every four years, establishes the topics for study by the ITU-T Study Groups which, in their turn, produce Recommendations on these topics. The approval of Recommendations by the Members of the

10、ITU-T is covered by the procedure laid down in WTSC Resolution No. l. In some areas of information technology which fall within ITU-Ts purview, the necessary standards are prepared on a collaborative basis with IS0 and IEC. NOTE In this Recommendation the term recognized Operating agency (ROA) inclu

11、des any individual, company, corporation or governmental organization that operates a public correspondence service. The terms Administration, ROA and public correspondence are defined in the Constitution of the ITU (Geneva, 1992). INTELLECTUAL PROPERTY RIGHTS The ITU draws attention to the possibil

12、ity that the practice or implementation of this Recommendation may involve the use of a claimed Intellectual Property Right. The 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

13、Recommendation development process. As of the date of approval of this Recommendation, the 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 represent the latest inform

14、ation and are therefore strongly urged to consult the TSB patent database. O ITU 1999 All rights reserved. No part of this publication may be reproduced or utilized in any form or by any means, electronic or mechanical, including photocopying and microfilm, without permission in writing from the ITU

15、. Il Recommendation G.841 (10198) 1 2 3 4 5 6 6.1 6.2 6.3 6.4 6.5 6.6 6.7 7 7.1 7.2 7.3 7.4 STD-ITU-T RECMN G=BYL-ENGL L778 m 48b259L 0bb0999 3L3 CONTENTS Page Scope References Terms and definitions . Abbreviations . Protection classifications Applications considerations MS shared protection rings .

16、 MS shared protection rings (transoceanic application) MS dedicated protection rings Unidirectional and bidirectional protection switching . Linear VC trail protection Subnetwork connection protection . Linear multiplex section protection switching . SDH trail protection . Linear multiplex section p

17、rotection 7 . 1 . 1 MSP protocol 7.1.2 MSP commands 7.1.3 MSP conditions . 7.1.4 Switch operation MS shared protection rings . 7.2.1 Two- and four-fibre MS shared protection rings . 7.2.2 Network objectives 7.2.3 Application architecture 7.2.4 Switch initiation criteria 7.2.5 Protection switch proto

18、col . 7.2.6 Protection algorithm operation 7.2.7 Examples . MS dedicated protection rings Linear VC trail protection 7.4.1 Network architecture . 7.4.2 Network objectives 7.4.3 Application architecture 7.4.4 Switch initiation criteria 7.4.5 Protection swltch1ng protocol Recommendation G.841 (10/98)

19、. 1 1 2 11 20 20 25 25 26 26 27 27 27 27 28 33 34 35 43 43 47 49 57 60 62 75 75 75 75 76 77 82 84 iii 8 8.1 8.2 8.3 8.4 8.5 8.6 STDmITU-T RECMN G-84L-ENGL L998 7.4.6 Protection algorithm operation SDH subnetwork connection protection . Network objectives . Network architecture Application architectu

20、re . 8.3.1 Routing 8.3.2 1 + 1 unidirectional protection switching 8.3.3 Other architectures Switch initiation criteria . 8.4.1 1 + 1 unidirectional protection switching 8.4.2 Other architectures Protection switching protocol . 8.5.1 1 + 1 unidirectional protection switching 8.5.2 Other architecture

21、s Protection algorithm operation . 8.6.1 1 + 1 unidirectional protection switching algorithm . 8.6.2 Other architectures Annex A . MS shared protection rings (transoceanic application) . A . 1 Application . A.2 Network objectives . A.3 Application architecture . A.4 Swltchlng criteria A.5 Protection

22、 switch protocol A.6 Protection algorithm operation . Annex B . Multiplex section protection (MSP) 1 + 1 optimized protocol. commands and operation . B.l 1 + 1 bidirectional switching optimized for a network using predominantly 1 + 1 bidirectional switching . B . 1 . 1 Lockout B . 1.2 Secondary sect

23、ion failure B . 1.3 K1 /K2 byte coding B . 1.4 K2 byte coding B . 1.5 Primary section mismatch . B.2 Switch commands . B.3 Switch operation . Page 84 85 85 85 86 86 86 86 87 87 88 89 89 89 89 89 89 90 90 90 91 91 92 92 96 96 96 97 97 98 98 98 99 iv Recommendation G.841 (10/98) Appendix I . Examples

24、of protection switching in an MS shared protection ring I . 1 Unidirectional signal fail (span) in a four-fibre ring 1.2 Unidirectional signal fail (ring) 1.3 Bidirectional signal fail (ring) 1.4 Unidirectional signal degrade (ring) . 1.5 Node failure 1.6 Unidirectional SF-R pre-empting a unidirecti

25、onal SD-S on non-adjacent spans . 1.7 Unidirectional SF-S pre-empting a unidirectional SF-R on adjacent spans - SF-S and SF-R detected at non-adjacent nodes . 1.8 Unidirectional SF-R pre-empting a unidirectional SD-S on adjacent spans 1.9 Unidirectional SF-R coexisting with a unidirectional SF-R on

26、non-adjacent spans I . 1 O Node failure on a ring with extra traffic capability (see Figure 1.1 1) . I . 1 1 Unidirectional SF-S pre-empting a unidirectional SF-R on adjacent spans - SF-S and SF-R detected at adjacent nodes Appendix II . Generalized squelching logic . II . 1 Squelching for unidirect

27、ional (and bidirectional) circuits 11.2 Squelching of multiply dropped and multiply sourced unidirectional circuits 11.2.1 Multiply dropped unidirectional circuits . 11.2.2 Multiply sourced unidirectional circuits . 11.2.3 Application to ring intenvorking . Page 100 100 101 101 102 102 103 104 105 1

28、06 107 107 127 127 127 127 128 128 Recommendation 6.841 (10/98) V Recommendation G.841 TYPES AND CHARACTERISTICS OF SDH NETWORK PROTECTION ARCHITECTURES (revised in 1998) 1 Scope This Recommendation describes the various protection mechanisms for Synchronous Digital Hierarchy (SDH) networks, their o

29、bjectives and their applications. Protection schemes are classified as: - SDH trail protection (at the section or path layer); - SDH subnetwork connection protection (with inherent monitoring, non-intrusive monitoring, and sub-layer monitoring). Protection intenvorking (including switching hierarchy

30、) and interconnection scenarios are under development in a separate Recommendation. OAM all 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

31、 ITU-T Recommendations is regularly published. - ITU-T Recommendation G.707 (1996), Network node interface for the Synchronous Digital - CCITT Recommendation G.774 (1 992), Synchronous Digital Hierarchy (SOH) management - ITU-T Recommendation G.783 (1 997), Characteristics of Synchronous Digital Hie

32、rarchy - TTU-T Recommendation G.784 (1 994), Synchronous Digital Hierarchy (SOH) management. - ITU-T Recommendation G.803 (1997), Architectures of transport networks based on the Hierarchy (SDH). information model for the network element view. (SDH) equipment functional blocks. Synchronous Digital H

33、ierarchy (SDH). Recommendation G.841 (10/98) 1 3 Terms and definitions This Recommendation defines the following terms: 3.1 APS controller: That part of a node that is responsible for generating and terminating information carried in the APS protocol and implementing the APS algorithm. 3.2 Add/Drop

34、Multiplex (ADM): Network elements that provide access to all, or some subset of the constituent signals contained within an STM-N signal. The constituent signals are added to (inserted), andor dropped from (extracted) the STM-N signal as it passes through the ADM. See 3.5fG.782. 3.3 add traffic: Nor

35、mal or extra traffic inserted into working, protection, or non-pre-emptible unprotected channels on the ring at a ring node. 3.4 Administrative Unit (AU): See Recommendation G.707. 3.5 Alarm Indication Signal (AIS): A code sent downstream in a digital network as an indication that an upstream failur

36、e has been detected and alarmed. It is associated with multiple transport layers. 3.6 APS request: That set of signals into an APS controller that determines its behaviour. An APS request can be either an externally initiated command or an automatically initiated command. 3.7 AU-AIS: See Recommendat

37、ion G.783. 3.8 AU pointer: See Recommendation G.707. 3.9 automatically initiated command: An APS request that is initiated by any one of the following: 1) multiplex section performance criteria; 2) local equipment performance criteria; or 3) received bridge requests. 3.10 auto-provisioning: The assi

38、gnment of values to parameters within a network element, without those values being specifically entered externally by a user. 3.11 bidirectional connection: See Recommendation G.803. An illustration is given in Figure 3-2. 3.12 bidirectional protection switching: A protection switching architecture

39、 in which, for a unidirectional failure (Le. a failure affecting only one direction of transmission), both directions (of the “trail“, subnetwork connection“, etc.) including the affected direction and the unaffected direction, are switched to protection. 3.13 bidirectional ring: In a bidirectional

40、ring, normal routing of the normal traffic signals is such that both directions of a bidirectional connection travel along the ring through the same nodes, but in opposite directions. 3.14 Bit Interleaved Parity N (BIP-N): See Recommendation G.707. 3.15 bridge: The action of transmitting identical t

41、raffic on both the working and protection channels. 3.16 bridge request: A message sent from a tail-end node to the head-end node requesting that the head-end perform a bridge of the normal traffic signals onto the protection channels. 3.17 bridge request status: A message sent from a tail-end node

42、to all other nodes within the protection system indicating that the tail-end has requested a bridge. 3.18 container: See Recommendation G.707. 3.19 controller failure: The condition during which a node is no longer able to correctly operate the APS protocol, but still generates a correctly formatted

43、 SDH frame. 2 Recommendation G.841 (10/98) 3.20 crossing K-bytes: When a node sees ring bridge requests of equal priority on both sides (This includes a switching node receiving a ring bridge request from the other end). 3.21 Data Communications Channel CC): See Recommendation G.784. 3.22 dedicated

44、protection: A protection architecture that provides capacity dedicated to the protection of tr :i ;i b.“ .-.-.-.-.-.-.-.-.-.-3,. Trail, 0 NCP . T1516710-94 * Required for dual-ended switching. Not required for single-ended switching. Adaptation SD Signal Degrade Protection Adaptation SF Signal Fail

45、Protection Matrix Connection SSF Server Signal Fail Protection Network Connection Trai$ Protection Trail Working Network Connection Trail, Working Trail Remote Defect Indication TT Trail Termination Remote Error Indication TTp Protection Trail Termination States: 1 Normal state 2 Failure state Figur

46、e 5-4/6.841- Functional model for generic 1 + 1 linear trail protection Recommendation 6.841 (10/98) 15 STD-ITU-T RECMN G-84L-ENGL L998 m 4862591 ObbLOL? T37 9 Extra Normal Normal Extra Protected trail .“.“. ._ ;ib i Aps iApS :. :i i SF; + *P : + . !i .“-“ .“.“.“ “, : Trail . . .“. 11516720-94 * SSF

47、 active on open connection Failure state (2). This is for further study. A Adaptation SD Signal Degrade pb Protection Adaptation SF Signal Fail MC, Protection Matrix Connection SSF Server Signal Fail NC, Protection Network Connection Trai$ Protection Trail NCW Working Network Connection Trail,., Wor

48、king Trail RD1 Remote Defect Indication TT Trail Termination Remote Error Indication Protection Trail Termination States: 1 Normal state 2 Failure state Figure 5-5/G.841- Functional model for generic 1:l linear trail protection - Revertive operation 16 Recommendation 6.841 (10/98) On failure state (

49、2), Trail, becomes Trail, Trail, becomes Trail, NC, becomes NC, and NC, becomes NC,. Adaptation SD Signai Degrade Protection Adaptation SF Signal Fail Protection Matrix Connection SSF Server Signal Fail Protection Network Connection Trai$, Protection Trail Working Network Connection Trail, Working Trail Remote Defect Indication TT Trail Termination Remote Error Indication TT, Protection Trail Termination states: 1 Normal state 2 Failure state Figure 5-6/G.841- Functional model for generic 1:l linear trail protection - Non-revertive operation Reco