1、 Technical Report No. 68, Feb r uary 2001 T1.TR.68 - 2001 Technical Report on Enhanced Network Survivability Performance Prepared by T1A1.2 Working Group on Network Survivability Performance Problem Solvers to the Telecommunications Industry T1.TR.68 - 2001 Copyright 2001 by Alliance for Telecommuni
2、cations Industry Solutions All rights reserved. Committee T1 is sponsored by the Alliance for Telecommunications Industry Solutions (ATIS) and accredited by the American National Standards Institute (ANSI). No part of this publication may be reproduced in any form, in an electronic retrieval system
3、or otherwise, without the prior written permission of the publisher.Technical Report on Enhanced Network Survivability Performance Abstract This Technical Report (TR) provides information on the network survivability performance of telecommunications networks. Although techniques, parameters, and me
4、thods needed to study network survivability performance are defined, recommended par ameter objectives are not established. This document is intended to provide a basis for designing and operating telecommunications networks to meet users expectations regarding network survivability, fulfilling the
5、need for a common understanding, and as sessment techniques. It emphasizes the classification of network failures ( i.e., identifying whether or not a service outage has occurred) and provides a framework to quantify the severity of failure events. This TR also provides improved measures of fai lure
6、s with respect to service outage severity. It classifies the architectures and services of all industry segments ( i.e., wireline, Internet, wireless, cable TV, and satellite) and provides methods to calculate outage index values for communication serv ice outages. T1.TR.68 - 2001 Document T1A1.2/20
7、01 - 001 R1 Prepared by T1A1.2 Working Group on Network Survivability Performance Foreword This Technical Report addresses the growing concerns from the telecommunications community about the survivability of t elecommunications networks, including the services provided under failure conditions. It
8、is intended to provide a basis for designing and operating telecommunications networks to meet users expectations regarding network survivability. This Technical Re port is intended for providers of telecommunications networks and services (including Internet services), and telecommunications equipm
9、ent suppliers. Suggestions for enhancement of this report are welcome. These should be sent to the Alliance for Telecom munications Industry Solutions, Suite 500, 1200 G Street N.W., Washington, D.C. 20005. Working Group T1A1.2 on Network Survivability Performance, which developed this report, has t
10、he following officers and participants: Chair: S. Makris Vice - Chair: G. Gr otefeld Chief Editor: F. Kaudel Editors: J. Bennett G. Grotefeld M. Kocaturk B. Manseur S. Makris Active Participants: O. Avellaneda J. Bennett R. Canaday W. Chiles G. Grotefeld R. Jensen F. Kaudel M. Kocaturk J. Lord S. Ma
11、krisB. Manseur R. PatersonP. Raush J. Roquet A. Websteri Table of Contents 0. EXECUTIVE SUMMARY .1 1. PURPOSE, SCOPE, APPLICATION, AND OUTLINE 2 1.1 PURPOSE .2 1.2 SCOPE .2 1.3 APPLICATION 2 1.4 OUTLINE .2 2. RELATED WORK 2 2.1 T1A1 TECHNICAL SUBCOMMITTEE.2 2.2 OTHER T1 TECHNICAL SUBCOMMITTEES3 2.3
12、INTERNATIONAL STANDARDS WORK 3 2.4 OTHER FORUMS AND COMMITTEES 3 2.5 U.S. NATIONAL SECURITY TELECOMMUNICATIONS ADVISORY COMMITTEE (NSTAC) INITIATIVES 4 3. INTRODUCTION5 4. NETWORK SURVIVABILITY PERFORMANCE.5 4.1 DEFINITIONS5 4.2 RELIABILITY AND MAINTAINABILITY METRICS FOR IP-BASED SERVICES 5 4.2.1 O
13、verview.6 4.2.2 Metrics Framework.6 4.2.2.1 Network Service Provider Metric Domain 7 4.2.2.2 Network Supplier Metric Areas 7 4.2.3 Service Reliability Metrics for IP-based Networks.8 4.2.3.1 Service Provider Domain 8 4.2.3.2 Network Supplier Domain 10 4.2.4 Summary .12 5. NETWORK SURVIVABILITY TECHN
14、IQUES AND MEASURES .12 5.1 PHYSICAL LAYER14 5.2 SYSTEM LAYER.15 5.3 LOGICAL LAYER15 5.4 SERVICE LAYER 16 5.5 NETWORK SURVIVABILITY CONSIDERATIONS .17 5.5.1 Basic Steps for Restoration.17 5.5.2 Operator Considerations 18 5.5.3 Deployment Options .19 5.5.4 Survivability Architectures .21 5.5.4.1 Overv
15、iew. 21 5.5.4.2 Protection 22 5.5.4.3 Restoration 22 5.5.4.4 Survivability Mechanisms. 22 5.5.5 Factors Influencing Choice of Survivability Architectures.25 5.6 MULTI-LAYER SURVIVABILITY .26 5.6.1 Survivability Options 28 5.6.2 Multi-layer Survivability Issues and Benefits .28 5.6.3 Multi-layer Surv
16、ivability Principles .32 5.6.4 Multi-layer Survivability Inter-Layer Recommendation.34 5.6.4.1 Protection Selectivity 34 5.6.4.2 Hold-Off Timer. 35 5.6.5 Multi-Layer Survivability Network Architecture Recommendation35 5.6.5.1 Supporting Extra Traffic . 35 ii 5.6.5.2 Avoiding Single Points of Failure
17、. 36 5.7 SUMMARY.36 6. NETWORK AND DATABASE RELIABILITY IN A NUMBER PORTABILITY ENVIRONMENT.37 6.1 NETWORK IMPACTS 37 6.2 OVERCOMING OVERLOADS.37 6.3 PREEMPTING NETWORK FAULTS .38 6.4 QUICKER FAULT RESOLUTION.38 6.5 HIGHER CALL COMPLETION RATES.38 6.6 CONTROLLING NETWORK DELAY38 7. ARCHITECTURES.39
18、7.1 WIRELINE39 7.2 WIRELESS .40 7.3 PCS NETWORK BASIC ARCHITECTURE 41 7.4 VOICEBAND TELEPHONY VIA CABLE TV 42 7.4.1 Background.42 7.4.2 Architectures.43 7.4.2.1 Cable Television Network Evolution 43 7.4.2.2 New Wireline Access Networks 43 7.4.3 Failure Modes, Effects, and Mitigation 44 7.4.3.1 Digit
19、al Switch . 44 7.4.3.2 Headend 44 7.4.3.3 Access Network Failure Modes 44 7.4.3.4 Power 45 7.4.3.5 Hybrid Fiber-Coax Technology Failure Modes 45 7.4.3.6 Fiber/Cable Cuts . 45 7.4.4 Cable TV Network Interconnections.45 7.4.4.1 Description and Diagram 46 7.5 VOICEBAND TELEPHONY VIA SATELLITE 46 7.5.1
20、Background.46 7.5.2 Services.47 7.5.2.1 Fixed Satellite Services (FSS). 47 7.5.2.2 Broadcast Satellite Services (BSS) . 47 7.5.2.3 Mobile Satellite Services (MSS). 48 7.5.3 Architectures.48 7.5.4 Failure Modes, Effects, and Mitigation 49 7.5.4.1 Satellite Failure Modes . 50 7.5.4.2 Earth Terminal Fa
21、ilure Modes 50 7.5.4.3 Propagation Outages. 50 7.5.4.4 Controller and Switching Center Failures. 51 7.5.5 PSTN Interconnection.51 7.5.5.1 Critical Interconnections. 53 8. SUGGESTIONS TO GENERAL INDUSTRY 54 9. RECOMMENDATIONS TO STANDARDS ORGANIZATIONS54 9.1 RECOMMENDATIONS TO COMMITTEE T1 54 9.2 REC
22、OMMENDATIONS FOR FUTURE T1A1.2 WORK54 10. BIBLIOGRAPHY56 11. DEFINITIONS .60 12. ABBREVIATIONS AND ACRONYMS61 iii APPENDIX A. OUTAGE INDEX FOR WIRELINE INDUSTRY SEGMENTS PROVIDING FIXED VOICEBAND TELEPHONY SERVICE65 A.1 INTRODUCTION .65 A.2 DATA ITEMS65 A.2.1 Data Items for Dedicated Outages .65 A.2
23、.2 Data Items for Diversified Outages 66 A.3 OUTAGE INDEX .66 A.3.1 Outage Index for Isolation from IntraLATA Intraoffice Service.67 A.3.2 Outage Index for Isolation from IntraLATA Interoffice Service.67 A.3.3 Outage Index for Isolation from InterLATA Interoffice Service .68 A.3.4 Outage Index for B
24、locked Call Attempts 68 A.3.5 Outage Index for 911 Service .68 A.4 COMMON TECHNIQUES .69 A.4.1 Duration Weight .69 A.4.2 Magnitude Weight.70 A.4.3 Time Factor 71 A.4.4 Normalization .72 A.5 OUTAGE INDEX WORKSHEETS 72 APPENDIX B. OUTAGE INDEX FOR THE MOBILE WIRELESS INDUSTRY SEGMENT.77 B.1 INTRODUCTI
25、ON .77 B.2 DATA ITEMS77 B.3 OUTAGE INDEX .78 B.3.1 Index for Wireless Mobile Customers Blocked from Initial Registration .78 B.3.2 Index for Wireless Mobile Registered Customers Whose Call Attempts Are Blocked 79 B.4 COMMON TECHNIQUES .79 B.4.1 Duration Weight .79 B.4.2 Magnitude Weight.80 B.4.3 Nor
26、malization .81 B.5 OUTAGE INDEX WORKSHEET82 APPENDIX C. OUTAGE INDEX FOR THE CABLE TV INDUSTRY SEGMENT 84 C.1 INTRODUCTION .84 C.2 DATA ITEMS84 C.2.1 Data Items for Dedicated Outages .84 C.2.2 Data Items for Diversified Outages 85 C.3 OUTAGE INDEX .85 C.3.1 Outage Index for Isolation from IntraLATA
27、Intraoffice Service.86 C.3.2 Outage Index for Isolation from IntraLATA Interoffice Service.86 C.3.3 Outage Index for Isolation from InterLATA Interoffice Service .86 C.3.4 Outage Index for Blocked Call Attempts 87 C.3.5 Outage Index for 911 Service .87 C.4 COMMON TECHNIQUES .87 C.4.1 Duration Weight
28、 .87 C.4.2 Magnitude Weight.88 C.4.3 Time Factor 90 C.4.4 Normalization .91 C.5 OUTAGE INDEX WORKSHEETS 91 APPENDIX D. OUTAGE INDEX FOR THE MOBILE SATELLITE INDUSTRY SEGMENT.96 D.1 INTRODUCTION .96 D.2 DATA ITEMS96 D.3 OUTAGE INDEX .96 D.3.1 Index for Satellite Mobile Customers Blocked from Registra
29、tion.97 iv D.3.2 Index for Satellite Mobile Registered Customers Whose Call Attempts Are Blocked.97 D.4 COMMON TECHNIQUES .98 D.4.1 Duration Weight .98 D.4.2 Magnitude Weight.98 D.4.3 Normalization .100 D.5 OUTAGE INDEX WORKSHEET100 APPENDIX E. USER EXPECTATIONS.103 E.1 U.S. GOVERNMENT USER EXPECTAT
30、IONS 103 E.2 OTHER USER EXPECTATIONS 104 APPENDIX F. NETWORK SURVIVABILITY TECHNIQUES 105 F.1 SYSTEM LAYER.105 F.1.1 Point-to-Point Systems with Automatic Protection Switching105 F.1.2 Rings .105 F.1.2.1 Unidirectional Ring 105 F.1.2.2 Bidirectional Ring. 106 F.1.2.3 Line Protection Switched Ring .
31、106 F.1.2.4 Path Protection Switched Ring . 108 F.2 LOGICAL LAYER108 F.2.1 DCS Reconfiguration Strategies.108 F.2.1.1 Detection and Notification 109 F.2.1.2 Identification. 109 F.2.1.3 Path (Route) Selection 109 F.2.1.4 Rerouting 111 F.2.1.5 Normalization . 111 F.2.1.6 Summary of DCS Reconfiguration
32、 Methods 111 F.3 SERVICE LAYER 111 F.3.1 Circuit Switching 111 F.3.1.1 Size Limits 111 F.3.1.2 Dynamic Routing 112 F.3.1.3 Reconfiguration 112 F.3.1.4 Network Management. 112 F.3.1.5 Multi-Serving 112 F.3.2 Packet Switching.112 F.3.3 Common Channel Signaling.113 F.3.3.1 Service Layer Architecture fo
33、r MTP. 113 F.3.3.2 Service Layer Architecture for SCCP . 116 F.3.3.3 Manual Traffic Management Controls 117 F.3.3.4 Relationship of Software Diversity to CCSN Reliability 117 F.4 INTEGRATED TECHNIQUES (MULTILAYER SURVIVABILITY EXAMPLES) 119 APPENDIX G. CCS NETWORK SURVIVABILITY ASSESSMENT EXAMPLE.12
34、1 G.1 INTRODUCTION .121 G.2 DEFINITIONS121 G.3 NUMBER OF SPANNING TREES IN A NETWORK122 G.4 REDUNDANCY.123 APPENDIX H. NETWORK SURVIVABILITY PERFORMANCE ANALYSIS 133 H.1 NETWORK SURVIVABILITY CHARACTERIZATION.133 H.2 NETWORK SURVIVABILITY ANALYSIS MODELS.133 H.2.1 Given Occurrence of Failure Surviva
35、bility Model .133 H.2.2 Random Occurrence of Failure Survivability Model134 H.2.3 Application of GOF and ROF Models134 H.3 GOF NETWORK SURVIVABILITY MEASURES 134 H.3.1 Service Layer Examples135 H.3.2 Logical and System Layer Examples 136 v H.4 ROF NETWORK SURVIVABILITY MEASURES.137 H.4.1 Service Lay
36、er Examples138 H.4.1.1 Circuit Switching 138 H.4.1.2 Packet Switching. 138 H.4.1.3 Common Channel Signaling. 138 H.4.2 Logical and System Layer Examples 142 H.5 QUALITATIVE ASSESSMENT OF NETWORK SURVIVABILITY TECHNIQUES143 H.6 EXAMPLE NETWORK SURVIVABILITY ANALYSES AND ASSESSMENTS.144 H.6.1 Bidirect
37、ional Ring Survivability Example 144 H.6.2 Network Survivability Assessment Example145 APPENDIX I. TELECOMMUNICATIONS SERVICE PRIORITY SYSTEM .148 I.1 BACKGROUND.148 I.2 TSP RULE.148 I.3 TSP DOCUMENTS .148 I.4 TSP REQUIREMENTS.148 I.5 IMPACTS OF TSP.149 APPENDIX J. TOLERANCE CATEGORIES FOR RESTORATI
38、ON TIMES150 APPENDIX K. GOALS AND USES OF QUANTIFICATION TECHNIQUES.154 K.1 INTRODUCTION .154 K.2 TYPE OF OUTAGE INDEX.154 K.2.1 “Universal” Outage Index154 K.2.2 “Service-based” Outage Index.155 K.2.3 Decision on the Type of Outage Index155 APPENDIX L. INTERRELATIONSHIPS OF SERVICES AND ARCHITECTUR
39、ES 156 L.1 DEFINITION OF SERVICE GROUP156 L.2 DEFINITION OF ARCHITECTURE CONCEPT .156 L.2.1 Technologies and Platforms .156 L.3 SERVICE GROUPS AND ARCHITECTURES .156 L.4 INTERRELATIONSHIPS OF VOICEBAND SERVICES IN THE PSTN .157 APPENDIX M. SERVICES159 M.1 PARTIAL LIST OF CANDIDATE SERVICES .159 APPE
40、NDIX N. ANALYSIS OF THE NUMBER OF OUTAGES 160 N.1 ANALYSIS OF THE NUMBER OF OUTAGES WITH RESPECT TO A REFERENCE PERIOD160 N.2 TREND ANALYSIS161 N.2.1 Statistical Theory162 N.2.1.1 Poisson Distribution . 162 N.2.1.2 Testing for Evidence of a Trend 162 N.2.1.3 Calculating the Parameters for the Model.
41、 164 N.2.1.4 Predicting Future Outage Rates 164 N.2.2 Example Test for Evidence of a Trend Using a 95% Level of Confidence .165 N.2.3 Trend Analysis of FCC-Reportable Service Outage Data (Number of Outages) .166 APPENDIX O. ADDITIONAL EXAMPLES OF OUTAGE INDEX CALCULATION168 O.1 DEDICATED (LOCAL SWIT
42、CH) PARTIAL SERVICES OUTAGE EXAMPLE WITH SAME SERVICE OUTAGE DURATIONS.168 O.2 DEDICATED (LOCAL SWITCH) PARTIAL SERVICES OUTAGE EXAMPLE WITH DIFFERENT SERVICE OUTAGE DURATIONS.169 O.3 DIVERSIFIED (TANDEM SWITCH) OUTAGE EXAMPLE 170 O.4 DIVERSIFIED (FACILITIES, DCS) OUTAGE EXAMPLE.171 vi O.5 DIVERSIFI
43、ED (FACILITIES, FIBER) OUTAGE EXAMPLE .172 APPENDIX P. GRADUAL RESTORATION OF SERVICE 173 P.1 EXAMPLE 173 P.2 GENERAL TECHNIQUE.174 APPENDIX Q. ESTIMATING CONFIDENCE INTERVALS FOR AGGREGATED OUTAGE INDEX VALUES BASED ON MOMENTS OF THE INDEX DISTRIBUTION .175 Q.1 BOOTSTRAP TECHNIQUES .175 Q.2 CLOSED-
44、FORM TECHNIQUES.175 Q.2.1 Theorem176 Q.2.2 Application to Outage Index Using FCC-Reportable Service Outage Data 176 Q.2.2.1 Estimate the Mean and Standard Deviation of the Annual Sum of Outage Index Values Based on the Baseline Year 176 Q.2.2.2 Estimate the Mean and Standard Deviation of the Quarter
45、ly Sum of Outage Index Values Based on the Baseline Year 176 Q.2.3 Uses of the Mean and Standard Deviation Estimates.177 Q.3 POWER OF THE TEST .177 APPENDIX R. NORMALIZED OUTAGE INDEX179 R.1 NORMALIZATION IN THE ATIS NRSC 1994 ANNUAL REPORT179 R.1.1 Normalization Data 179 R.1.2 Normalization of Magn
46、itude.179 R.1.3 Normalization of Frequency .179 R.1.4 Normalization Factors180 R.1.5 Calculation Based on Normalized Customers 180 R.1.5.1 Frequency Normalization 180 R.1.5.2 Index Normalization . 180 R.2 GENERALIZATION FOR FUTURE REPORTS181 R.2.1 Normalization Factors Example.182 R.2.2 Frequency No
47、rmalization .183 R.2.3 Index Normalization .183 R.2.4 Analysis of Normalized Data 183 INDEX 184 Technical Report No. 68 (T1.TR.68) 1 0. Executive Summary This Technical Report (TR) combines, updates, enhances, and supersedes the Committee T1 Technical Report Nos. 24 1 (TR No. 24, Network Survivabili
48、ty Performance) and 24A 2 (Supplement to TR No. 24), which addressed the need for (i) a common understanding of network survivability, and (ii) common techniques for assessing network survivability. This report resolves some of the issues and questions left for further study from the previous techni
49、cal reports. TR No. 24 emphasized (i) the classification of network failures (i.e., identifying whether or not a service outage has occurred), and (ii) addressed the quantification of failure events and techniques to measure the severity of the failure. TR No. 24A provided improved measures of failures with respect to service outage severity. TR No. 24A also classified the architectures and services other than the wireline (i.e., wireless, cable TV, and satellite) that can provide voiceband telephony service and illustrated methods to calculate outage index values comparable to
