1、 STD-ITU-T RECMN G-842-ENGL I777 4862573 Ob39145 3Ub m INTERNATIONAL TELECOMMUNICATION UNION ITU=T TELECOMMUNICATION STANDARDIZATION SECTOR OF ITU G.842 (04/97) SERIES G: TRANSMISSION SYSTEMS AND MEDIA, DIGITAL SYSTEMS AND NETWORKS Digital transmission systems - Digital networks - SDH network charac
2、teristics Interworking of SDH network protection arch i tectu res ITU-T Recommendation G.842 (Previously CCIlT Recommendation) STD-ITU-T RECMN G-8Li2-ENGL 1997 M LiBb259L Ob3914b 242 = ITU-T G-SERIES RECOMMENDATIONS TRANSMISSION SYSTEMS AND MEDIA, DIGITAL SYSTEMS AND NETWORKS INTERNATIONAL TELEPHONE
3、 CONNECTIONS AND CIRCUITS INTERNATIONAL ANALOGUE CARRIER SYSTEM TRANSMISSION SYSTEMS INDIVIDUAL CHARACTERISTICS OF INTERNATIONAL CARRIER TELEPHONE SYSTEMS ON METALLIC LINES GENERAL CHARACTERISTICS OF INTERNATIONAL CARRIER TELEPHONE WITH METALLIC LINES COORDINATION OF RADIOTELEPHONY AND LINE TELEPHON
4、Y TRANSMISSION MEDIA CHARACTERISTICS DIGITAL TRANSMISSION SYSTEMS TERMINAL EQUIPMENTS DIGITAL NETWORKS GENERAL CHARACTERISTICS COMMON TO ALL ANALOGUE CARRIER- SYSTEMS ON RADIO-RELAY OR SATELLITE LINKS AND INTERCONNECTION General aspects Design objectives for digital networks Quality and availability
5、 targets Network capabilities and functions G. 1 OO-G. I99 G.200-G.299 G.300-G.399 G.400-G.449 G .450-G.499 G.700-G.799 G.800-G.899 G.800-G.809 G.810-G.819 G.820-G.829 G.8304.839 haracterlstics - , Telecommunications management network General Parameters for optical fibre cable systems Digital secti
6、ons at hierarchical bit rates based on a bit rate of 2048 kbiffs Digital line transmission systems on cable at non-hierarchical bit rates Digital line systems provided by FDM transmission bearers Digital line systems Digital section and digital transmission systems for customer access to ISDN Optica
7、l fibre submarine cable systems Optical line systems for local and access networks DIGITAL SECTIONS AND DIGITAL LINE SYSTEM G.850-G.859 G.900-G .999 G.900-G.909 G.910-G.919 G .920-G. 929 G.930-G.939 G.950-G.959 G .960-G.969 G.970-G.979 G.980-G.999 G .940-G.949 For further details, please refer to IT
8、U-T List of Recommendations. STD-ITU-T RECMN G-842-ENGL 1997 i.rBb2591 Ob3911i7 189 D ITU-T RECOMMENDATION 6.842 INTERWORKING OF SDH NETWORK PROTECTION ARCHITECTURES Summary This Recommendation provides specifications for the interworking of network protection architectures. Specifically covered are
9、 single and dual node interconnection between MS-shared protection rings and SNCP rings of like or unlike types. Source ITU-T Recommendation G.842 was prepared by IT-T Study Group 15 (1997-2000) and was approved under the WTSC ResolutionNo. 1 procedure on the 8th of April 1997. FOREWORD ITU (Interna
10、tional Telecommunication Union) is the United Nations Specialized Agency in the field of telecommunications. The IT Telecommunication Standardization Sector (IT-T) is a permanent organ of the ITU. The ITU-T is responsible for studying technical, operating and tariff questions and issuing Recommendat
11、ions on them with a view to standardizing telecommunications on a worldwide basis. The World Telecommunication Standardization Conference (WTSC), which meets every four years, establishes the topics for study by the IT-T Study Groups which, in their tun, produce Recommendations on these topics. The
12、approval of Recommendations by the Members of the ITU-T is covered by the procedure laid down in WTSC Resolution No. 1. In some areas of information technology which fall within ITU-Tspurview, the necessary standards are prepared on a collaborative basis with IS0 and IEC. NOTE In this Recommendation
13、, the expression “Administration“ is used for conciseness to indicate both a telecommunication administration and a recognized operating agency. INTELLECTUAL PROPERTY RIGHTS The ITU draws attention to the possibility that the practice or implementation of this Recommendation may involve the use of a
14、 claimed Intellectual Property Right. The IT 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, t
15、he IT hadhad not 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 information and are therefore strongly urged to consult the TSB patent database. O IT 19
16、97 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. 11 Recommendation 6.842 (04/97) 1 2 4 5 5.1 6 6.1 6.2 7 8 STD-ITU-T RECMN G.842-E
17、NGL L777 D 48b257L Ob37147 T5L D CONTENTS Page Scope References Terms and definitions . Abbreviations . Interworking cntendobj ectives Criteria for ring interworking with an MS-shared protection ring . Single node interconnection Dual node interconnection 6.2.1 Generalized architecture 6.2.2 Ring in
18、terworking with an MS-shared protection ring . 6.2.3 6.2.4 Multiple rings . Interworking architectures Ring interworking With an SNCP ring Interworking among network layers . Switch contention . Recommendation G.842 (04/97) 1 1 1 3 4 4 5 5 5 5 7 21 32 32 32 . 111 STD-ITU-T RECMN G-AVZ-ENGL L997 LiAb
19、2591 Ob39150 773 D Recommendation G.842 INTERWORKING OF SDH NETWORK PROTECTION ARCHITECTURES (Geneva, 1997) 1 Scope This Recommendation describes mechanisms for interworking between network protection architectures. The network protection architectures are described in Recommendation G.84 1. Interwo
20、rking is described for single and dual node interconnection for exchanging traffic between rings. Each ring may be configured for MS-shared protection or for SNCP protection. 2 References The following ITU-T Recommendations, and other references contain provisions which, through reference in this te
21、xt, constitute provisions of this Recommendation. At the time of publication, the editions indicated were valid. All Recommendations and other references are subject to revision; all users of this Recommendation are therefore encouraged to investigate the possibility of applying the most recent edit
22、ion of the Recommendations and other references listed below. A list of the currently valid ITU-T Recommendations is regularly published. - ITU-T Recommendation G.803 (1 997), Architecture of transport networks based on the Synchronous Digital Hierarchy (SDW. - ITU-T Recommendation G.841 (1999, Type
23、s and characteristics of SDH network protection architectures. ITU-T Recommendation G.783 (1 997), Characteristics of Synchronous Digital Hierarchy (SDH) equipment functional blocks. - 3 Terms and definitions NOTE - These definitions need to be reviewed with respect to the emerging Recommendation on
24、 SDH vocabulary. This Recommendation defines the following terms. 3.1 drop-and-continue: A function within a ring node where traffic is both extracted from the working channels on the ring (drop), and transmitted onwards on the ring (continue). 3.2 dual hubbed: Dual hubbed traffic can be routed to e
25、ither or both of two central offices (or similar sites). Dual hubbed traffic is survivable under a failure of one of the two hubs. 3.3 dual node interconnection: An architecture between two rings where two nodes in each ring are interconnected. 3.4 hold-off time: The time that a protection switch co
26、ntroller waits after detecting a failure before initiating the switch. 3.5 path selector: Within an SNCP architecture, the node function that selects a tributary which is extracted from the working channels arriving fi-om one side of the node or fi-om the other side of the node, according to path le
27、vel criteria. 3.6 primary node: Within an MS-shared protection ring interworking architecture, the node which provides the service selection and drop-and-continue functions for a tributary. Different tributaries may have different designated primary nodes. Recommendation 6.842 (04197) 1 3.7 propagat
28、ion of switching: One protection switch leading to another. Propagation of switching is often, though not always, undesirable from a maintenance point of view. 3.8 ring interconnection: An architecture between two rings where one or more nodes in each ring are interconnected. 3.9 ring interworking:
29、A network topology whereby two rings are interconnected at two nodes on each ring, and the topology operates such that a failure at either of these two nodes will not cause loss of any working traffic. This is illustrated in Figure 1. 3.10 secondary circuit: Within an MS-shared protection ring inter
30、working architecture, this is the alternate routing that traffic travelling from one ring to another follows. This alternate additional routing is used when the service circuit is interrupted. 3.11 secondary node: Within an MS-shared protection ring interworking architecture, the node which provides
31、 the alternate interworking route for a tributary. 3.12 service circuit: Within an MS-shared protection ring interworking architecture, this is the preferred original routing that traffic travelling from one ring to another normally follows. 3.13 service selector: Within an MS-shared protection ring
32、 architecture, the node function used for ring interworking. It selects traffic fiom either the channels arriving from one side of the node, or fiom trafic entering the ring, according to some criteria. 3.14 single node interconnection: An architecture between two rings where one node in each ring i
33、s interconnected. 3.15 termination node: The node (other than a primary or secondary node) where a tributary enters or exits the ring. - 2 Recommendation 6.842 (04/97) T1524330-96 Failure free state (from perspective of top ring) Figure UG.842 - Generalized ring interworking 4 Abbreviations This Rec
34、ommendation uses the following abbreviations: ADM Add/Drop Multiplexer AIS Alarm Indication Signal AU Administrative Unit HO Higher Order HP Higher order Path HPC Higher order Path Connection HPOM LO Lower Order LOF Loss of Frame LOP Loss of Pointer LOS Loss of Signal LPC Lower order Path Connection
35、 LPOM Higher order Path Overhead Monitor Lower order Path Overhead Monitor Recommendation G.842 (04/97) 3 STD-ITU-T RECMN G-842-ENGL 1777 48b2.591 Ob37153 482 MS SDH SNC SNCP SNC/I SNC/N STM(-N) TIM UNEQ vc Multiplex Section Synchronous Digital Hierarchy SubNetwork Connection SubNetwork Connection P
36、rotection SubNetwork Connection Protection with Inherent Monitoring SubNetwork Connection Protection with Non-Intrusive Monitoring Synchronous Transport Module (-N) Trace Identifier Mismatch Unequipped Virtual Container 5 Interworking criteria/objectives Interworking SDH protection architectures are
37、 meant to provide an even greater degree of protection within a network. Some considerations for interworking criteria are as follows: - end-to-end availability requirements; - - implementation complexity and costs. The following is a list of intenvorking objectives: 1) 2) 3) robustness against vari
38、ous failure events; Ring intenvorking shall be accommodated in such a way that if two rings are connected at more than one node each, a failure at one of these node shall not cause loss of any service. It should be possible to avoid propagation of switching between interworking rings. The ring shall
39、 be able to drop traffic at multiple nodes, i.e. working traffic can be dropped at two, or more, nodes on a ring without compromising the ability to restore traffic that is dual hubbed (or any other traffic). Ring interconnection may occur among multiple rings. Interconnection boundaries should be t
40、he same for all similar instances of intenvorking between two ring types. 4) 5.1 The following objectives apply to the particular case of ring interworking with an MS-shared protection ring: - MS-shared protection ring nodes should support the capability to interconnect with another architecture at
41、two nodes. In particular, MS-shared protection ring nodes should support the capability to interconnect with mother ring at two nodes, regardless of the type of protection switching employed by the other ring (e.g. SNCP or MS-shared protection rings). For a tributary being protected against ring int
42、erconnection failures, the interconnection architecture should be capable of protecting against the failure of one interconnecting node, two interconnecting nodes (each on different rings, but on the same interconnect), or the connection between the two interconnecting nodes. The two interconnecting
43、 nodes should not need to be adjacent. The ring interconnect architecture should support STM-1 electrical or STM-N optical interconnection (where STM-N signals may contain concatenated payloads). The ring interconnection architecture should not require inter-ring signalling. Providing protection for
44、 the interconnecting line is not considered inter-ring signalling. Criteria for ring interworking with an MS-shared protection ring - - - - 4 Recommendation 6.842 (04/97) - - - Protection for ring interconnection failures should be based on detecting path defects. To avoid propagation of failures wh
45、en possible, a hold-off time should be allowed. Ring interworking using protection bandwidth between ring interworking nodes will be accommodated. The details of ring interworking using protection bandwidth are for further study. 6 Interworking architectures This clause describes the interworking be
46、tween multiple instances of protection architectures within the same network layer intersecting at one or more network nodes (e.g. two or more SNC rings exchanging traffic within a single office). - 6.1 Single node interconnection Single node interconnection is an architecture between two rings wher
47、e one node in each ring is interconnected. This architecture (shown in Figure 2) has a single point of failure at the point where the rings are interconnected. Interconnection protection can be provided by multiplex section protection of the interconnecting span, but no protection is available due t
48、o failure of either interconnecting node. P-O-9 Ring 1 Ring 2 c T1524340-96 Figure 2/G.842 - Example of single node interconnection 6.2 Dual node interconnection 6.2.1 Generalized architecture Dual node interconnection is an architecture between two rings where two nodes in each ring are interconnec
49、ted. This is illustrated in Figure 3. The two interconnections between the two rings can be arranged to provide protection of the traffic crossing fiom one ring to the other. A special form of Recommendation G.842 (04/97) 5 STD-ITU-T RECMN G.842-ENGL 1997 U 4862592 Ob37255 255 D dual node interconnection is given the term ring interworking. Ring interworking is a network topology whereby two rings are interconnected at two nodes on each ring, and the topology operates such that a failure at either of these two nodes will not cause loss of any working traflic. This i
