ATIS T1 TR 31-1994 Delay and Echo Performance Guidelines for SONET Self-Healing Rings During Diversity Routing.pdf
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1、Report No. 31 A Technical ReportonApril 1994 Delay and EchoPerformance Guidelinesfor SONET Self-HealingRings During DiversityRoutingPrepared byT1A1.1 Working Groupon NetworkPerformance forVoice and VoicebandDataCommittee T1 is sponsored by the Alliance for Telecommunications Industry SolutionsAccred
2、ited by American National Standards InstituteCopyright 1994 by Alliance for Telecommunications IndustrySolutions All rights reserved.No part of this publication may be reproduced in any form, in an electronic retrieval system or otherwise, without the prior written permission of the publisher.A Tech
3、nical Report onDelay and Echo Performance GuidelinesforSONET Self-Healing RingsDuring Diversity RoutingAbstractThis Technical Report addresses echo path delay and echo performance of largeSONET fiber self-healing interoffice rings during their failed state in which diversityprotection routing is use
4、d. Guidelines regarding the delay during ring diversityprotection mode have been included in the recent addendum to ANSI Standard T1.508-1992, Loss Plan for Evolving Digital Networks. The Technical Report is intended toprovide further guidance regarding this emerging technology. The Report includes
5、abrief general description of the operation of large self-healing rings and associatedissues followed by a technical analysis of listener echo, talker echo, and their effect onecho canceler performance in large rings. Finally, based on the above analysis, theReport provides delay and echo performanc
6、e guidelines for rings. For normal operationof a ring, it is assumed that delay performance guidelines in ANSI T1.508-1992 will bemaintained. For operation during a temporary diversity protection mode, which isexpected to be brief and infrequent, it is recommended that higher-than-normal delaysbe al
7、lowed, but that maximum round-trip delay be limited, based on echo performanceconsiderations. In particular, it should be noted that during the diversity protectionmode, round-trip delay may increase to a maximum of 35 ms for intraLATA calls with 6-dB design loss, to a maximum of about 20 ms for int
8、raLATA calls with 0-dB or 3-dBdesign loss, and to a maximum of 20 ms for the access portion of interLATA calls.Because the guidelines presented in this report are based only on voice transmissionquality criteria, it should be noted that other considerations, such as the interworking ofnetwork equipm
9、ent, may present more restrictive delay limitations.Document T1A1/93-059Prepared byT1A1.1Working Group on Network Performance for Voice and Voiceband DataiDelay and Echo Performance Guidelines forSONET Self-Healing Rings During Diversity RoutingFOREWORDThis T1 Technical Report was initiated in the T
10、1A1.1 Subworking Group onLoss/Level Planning. The Technical Report provides network planners anddesigners guidelines concerning the transmission delays and echo performancethat can be anticipated during temporary diversity rerouting of large SONETrings. The intent of the Report is to provide, to the
11、 telecommunications industry,technical information on delay and performance aspects of SONET rings.Accordingly, the use of “should“ or “recommend“ throughout the document is notto be construed as implying any requirement.Suggestions for improvement of the Technical Report are welcome and shouldbe se
12、nt to: Alliance for Telecommunications Industry Solutions - Committee T1Secretariat, 1200 G Street N.W., Suite 500, Washington, D.C. 20005,iiCONTENTS1 - Introduction 11.1 - Scope and Purpose. 11.2 - Overview of Rings, Delay, and Echo Performance Issues 12 - Definitions and Classifications. 32.1 - Ri
13、ng and Ring-Protection-Switching Definitions 32.2 - Ring Classifications . 32.2.1 - Ring. 42.2.2 - Line Switched Ring . 42.2.3 - Path Switched Ring. 42.2.4 - Unidirectional Ring 42.2.5 - Bi-directional Ring . 43 - Performance Issues. 44 - Criteria for Acceptable Degradation of Echo Performance Durin
14、g DiversityProtection 55 - Listener Echo 66 - Talker Echo . 77 - Echo Canceler Tail Delay 88 - Conclusions and Guidelines 9References . 19Abbreviations and Acronyms 20FiguresFigure 1 - Guidelines for NI-to-POT Delay (from ANSI T1.508-1992). 11Figure 2 - Typical Fiber Ring Architecture. 12Figure 2a -
15、 Diversity Protection Example 1. 12Figure 2b - Diversity Protection Example 2. 13Figure 2c - Diversity Protection Example 3. 13Figure 2d - Diversity Protection Example 4. 14Figure 2e - Diversity Protection Example 5. 14Figure 3 - Various Echo Paths 15Figure 4 - Effect of Delay on Listener Echo Perfo
16、rmance. 16Figure 5 - Effect of Delay on Talker Echo Performance (Design Loss = 6 dB) . 17Figure 6 - Effect of Delay on Talker Echo Performance (Design Loss = 3 dB) . 1811 Introduction1.1 Scope and PurposeThis Technical Report addresses the effect that protection diversity routing inSynchronous Optic
17、al NETwork (SONET) rings may have on voice transmission quality.Rural rings can be several hundred miles in circumference and, under diversity routingconditions, additional network nodes and path length can cause a significant increasein transmission and signal processing delay. This could affect ec
18、ho performance andecho canceler operation on intraLATA calls, interLATA calls or both.Transmission delay for exchange access is treated in ANSI T1.506a1and ANSIT1.508.2Figure 1 graphically depicts the typical range of round-trip delay in exchangeaccess networks for normal routing. Additional delay g
19、uidelines for exchange accessprovided on SONET rings are given in ANSI T1.508a.3This Technical Reportsupplements the information in these standards, and includes material on intraLATAconnections as well as exchange access connections.This Technical Report presents the results of analysis of the voic
20、e transmissionperformance of large SONET rings during temporary diversity rerouting caused by anoutage on the normal route, and provides round-trip delay guidelines for networkproviders, end-users, and network equipment designers and manufacturers.4, 5, 6, 7, 8, 9The effects of listener and talker e
21、cho on end-user perception of voice transmissionquality and the effects of increased delay on echo canceler performance are discussed.Guidelines for maximum delay are given for exchange access and intraLATAconnections during diversity rerouting.1.2 Overview of Rings, Delay, and Echo Performance Issu
22、esNetwork survivability is a major concern for network providers. To enhance networksurvivability, some transport facility networks are being arranged geographically in theform of fiber rings.4, 5, 10, 11, 12, 13Unidirectional and bi-directional, and path switched andline switched, types of rings ma
23、y be used. The delay during a failure depends on thetype of ring because each type uses a different method for routing the protectionchannels. The details of these routing methods are outside the scope of thisdocument. In general, line switched rings switch the working channels to and from theprotec
24、tion channels at the two nodes adjacent to a failure, effectively replacing thefailed span with the long arc of the ring between these two nodes. Path switched ringsswitch a failed working channel to the protection channel along the other arc of the ringthat is not used by the working channel. Trans
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