1、Report No. 55 A Technical ReportonOctober 1998 Reliability andSurvivability Aspectsof the InteractionsBetween the Internet andthe PublicTelecommunicationsNetworkPrepared byT1A1.2Working GrouponNetwork SurvivabilityPerformanceCommittee T1 is sponsored by the Alliance for Telecommunications Industry S
2、olutionsAccredited by the American National Standards InstituteCopyright 1998 by Alliance for Telecommunications IndustrySolutionsAll rights reserved.No part of this publication may be reproduced in any form,in an electronic retrieval system or otherwise, without theprior written permission of the p
3、ublisher.A Technical ReportonReliability and Survivability Aspects of theInteractions Between the Internet and thePublic Telecommunications NetworkAbstractThis Technical Report addresses the reliability and survivability aspects of theinteractions between the Internet and the Public Telecommunicatio
4、ns Network(PTN). It examines the general architectures of both networks and the interfacesbetween them. This document offers suggestions for meeting reliabilitychallenges posed by changing network traffic characteristics. Two majorcategories of solutions are introduced: network engineering and netwo
5、rkarchitecture. Within these categories, alternatives may be selected depending onthe operators local circumstances.Document T1A1.2/98-001R6Prepared by T1A1.2Working Group on Network Survivability PerformanceForewordThis Technical Report addresses the reliability and survivability aspects of theinte
6、ractions between the Internet and the Public Telecommunications Network(PTN). It examines the general architectures of both networks and the interfacesbetween them. This document offers suggestions for meeting reliability challengesposed by changing network traffic characteristics. Two major categor
7、ies ofsolutions are introduced: network engineering and network architecture. Withinthese categories, alternatives may be selected depending on the operators localcircumstances.This Technical Report is intended for providers of telecommunications networks andservices (including Internet services), a
8、nd telecommunications equipment suppliers.Suggestions for enhancement of this report are welcome. These should be sent tothe Alliance for Telecommunications Industry Solutions, Suite 500, 1200 G StreetN.W., Washington, D.C. 20005.Working Group T1A1.2 on Network Survivability Performance, which devel
9、opedthis report, has the following officers and participants:Chair: F. KaudelVice-Chair: S. MakrisEditors:F. Kaudel S. Makris J. Bennett M. KocaturkActive Participants:J. BennettL. BrownR. CanadayM. DaneshmandR. JensenF. KaudelM. KocaturkJ. LordS. MakrisA. McCainI. SebuktekinD. SetzkeL. SzerenyiS. V
10、inayagamurthyR. WalleriTable of Contents0. EXECUTIVE SUMMARY. 11. PURPOSE, SCOPE, APPLICATION, AND OUTLINE . 11.1 PURPOSE 11.2 SCOPE 11.3 APPLICATION . 11.4 OUTLINE 12. RELATED WORK . 22.1 T1A1 TECHNICAL SUBCOMMITTEE . 22.2 INTERNATIONAL STANDARDS WORK . 22.3 INTERNET GOVERNING AND STANDARDS BODIES
11、32.4 OTHER FORUMS AND COMMITTEES . 33. INTRODUCTION. 44. INTERNET AND THE CHALLENGE OF CHANGING PTN TRAFFIC CHARACTERISTICS 45. INTERNET 55.1 INTERNET OVERVIEW 55.2 INTERNET INDUSTRY STRUCTURE 65.2.1 Network Service Providers (NSPs) 65.2.2 Internet Service Providers (ISPs) 65.2.3 Network Access Poin
12、t (NAP) Service Providers . 65.2.4 User Networks. 75.3 INTERNET ARCHITECTURE . 75.3.1 Organizational Boundaries of the Internet Architecture 75.3.1.1 Backbone and Access Networks of the Internet. 85.3.1.2 Network Access Points 115.3.1.3 Internet Users. 115.3.1.4 Routers. 125.4 INTERNET ROUTING AND T
13、RANSMISSION TECHNOLOGIES 125.5 CURRENT RELIABILITY/AVAILABILITY OBJECTIVES FOR THE INTERNET 125.6 QUALITY OF SERVICE (QOS) AND DIFFERENTIATED SERVICES 135.7 CURRENT TRENDS IN THE INTERNET 136. PUBLIC TELECOMMUNICATIONS NETWORK. 136.1 PTN OVERVIEW 136.2 PTN ARCHITECTURE . 146.2.1 The Architecture of
14、Todays PSTN . 146.2.2 Hypothetical Local Network Configurations 156.2.2.1 End Office Switching Systems. 156.2.2.2 Host/Remote Switching Unit and Remote Terminals 166.2.2.3 Interexchange Carrier Point Of Presence (POP) 176.3 PTN RELIABILITY/AVAILABILITY OBJECTIVES 186.3.1 Local Exchange PTN Hypotheti
15、cal Reference Connection. 196.3.2 End-to-End Network Availability Objective 197. INTERACTIONS BETWEEN INTERNET AND PTN. 197.1 OVERVIEW. 197.2 INTERNET/PTN CONNECTION ARCHITECTURES. 217.3 INTERACTIONS RELATED TO RELIABILITY/SURVIVABILITY 22ii7.3.1 Customer View of Internet Reliability. 227.3.2 Intern
16、et Access Traffic Impact Points . 227.4 FAILURE MODES 247.5 PARAMETER DESCRIPTIONS . 247.6 PARAMETER MEASUREMENT. 257.6.1 Failure Data 257.6.2 Traffic Performance Data. 267.6.3 Equipment Data 267.7 FAILURE ANALYSIS METHODS . 278. RELIABILITY/SURVIVABILITY SOLUTIONS AND SUGGESTIONS TO GENERAL INDUSTR
17、Y . 288.1 ENGINEERING SOLUTIONS 288.2 ARCHITECTURAL SOLUTIONS. 288.3 OTHER SOLUTIONS. 298.4 FAILURE PREVENTION/MITIGATION METHODS 309. RECOMMENDATIONS TO STANDARDS ORGANIZATIONS. 309.1 RECOMMENDATIONS FOR COMMITTEE T1 . 319.2 RECOMMENDATIONS FOR FUTURE T1A1.2 WORK. 3110. SUMMARY. 3111. BIBLIOGRAPHY.
18、 3212. DEFINITIONS 3413. ABBREVIATIONS AND ACRONYMS . 36APPENDIX A. NRSC INTERNET STUDY TEAMS MAJOR FINDINGS . 39A.1 BACKGROUND 39A.2 NRSC INTERNET STUDY TEAMS CONCLUSIONS. 39A.3 NRSC INTERNET STUDY TEAMS RECOMMENDATIONS. 39APPENDIX B. INTERNET GOVERNING AND STANDARDS BODIES: ROADMAP 40B.1 INTERNET
19、SOCIETY (ISOC)40B.2 INTERNET ARCHITECTURE BOARD (IAB) 40B.3 INTERNET ENGINEERING STEERING GROUP (IESG) . 40B.4 INTERNET ENGINEERING TASK FORCE (IETF) . 40B.5 INTERNET ASSIGNED NUMBERS AUTHORITY (IANA) 41B.6 FEDERAL NETWORKING COUNCIL (FNC). 41APPENDIX C. INTERNET ROUTING AND TRANSMISSION TECHNOLOGIE
20、S: ROADMAP. 42C.1 NAMING AND ADDRESSING 42C.1.1 Host Identifiers 42C.1.2 Domain Name System (DNS) 42C.1.3 Classes of IP Addresses 43C.1.4 Subnetting . 43C.1.5 Classless Interdomain Routing . 43C.2 ROUTING 44C.2.1 Routing Arbitration. 44C.2.2 Border Gateway Protocol, Version 4 (BGP4). 45C.2.3 Inter-A
21、S Policy Enforcement via BGP4 45C.3 CORE INTERNET PROTOCOLS . 45C.3.1 Internet Protocol (IP) 46C.3.2 Internet Control Message Protocol (ICMP) . 47iiiC.3.3 User Datagram Protocol (UDP). 47C.3.4 Transmission Control Protocol (TCP) 47APPENDIX D. QOS SUPPORT FOR THE INTERNET AND ATM 49D.1 QOS SUPPORT FO
22、R INTERNET 49D.2 QOS SUPPORT FOR ATM NETWORKS 49APPENDIX E. CURRENT TRENDS IN INTERNET: ROADMAP 51E.1 QOS AND DIFFERENTIATED SERVICES . 51E.2 BUSINESS APPLICATIONS OF THE WORLD WIDE WEB (WWW) . 51E.3 BANDWIDTH EXPANSION/DEMAND 52E.4 LABEL SWITCHING TECHNOLOGIES 52E.5 ADDRESS EXHAUST/SCALABILITY SOLU
23、TIONS. 53E.6 SECURITY 53E.7 SPAM INTERNET ETHICS, LAWS 54APPENDIX F. END-TO-END NETWORK AVAILABILITY OBJECTIVE. 55F.1 ALLOCATION OF THE END-TO-END NETWORK AVAILABILITY OBJECTIVE 55F.2 NETWORK SEGMENT AVAILABILITY OBJECTIVES. 55F.2.1 Distribution Network Segment 55F.2.2 Circuit Switch 56F.2.3 ISDN Sw
24、itch 57F.2.4 Facility-Entrance Network Segment . 58F.2.5 Interoffice Network Segment. 58INDEX . 6010. Executive SummaryThis Technical Report addresses the reliability and survivability aspects of the interactions between the Internet andthe Public Telecommunications Network (PTN1). It examines the g
25、eneral architectures of both networks and theinterfaces between them. This document offers suggestions for meeting reliability challenges posed by changingnetwork traffic characteristics. Two major categories of solutions are introduced: network engineering and networkarchitecture. Within these cate
26、gories, alternatives may be selected depending on the operators local circumstances.1. Purpose, Scope, Application, and Outline1.1 PurposeOver the past few years, the traffic characteristics of telecommunications networks have been changing. Forexample, Internet users are adding many calls with shor
27、ter and longer holding times than usual. This change, in turn,raises concerns about maintaining the performance and reliability of telecommunications services using the PublicSwitched Telecommunications Network (PSTN). The purpose of this Technical Report is to describe the challengesand propose som
28、e potential solutions to help maintain a high level of availability, reliability, and survivability of thePSTN.1.2 ScopeThis Technical Report focuses on analysis of the impact of changing traffic characteristics on the PSTN, and the useof the PSTN for access to the Internet. The availability, reliab
29、ility, and survivability aspects of the interactionsbetween the Internet and the PTN, as well as the impact of that interaction on other PTN services, are addressed froman end-users viewpoint.1.3 ApplicationThe intended audience of this Technical Report includes providers of telecommunications netwo
30、rks and services(including Internet services), as well as suppliers of telecommunications equipment and support systems.Network-provider personnel including designers, planners, traffic engineers, and individuals in charge ofoperations, administration, maintenance, and management can use this docume
31、nt to enhance the performance andsurvivability of their networks. Telecommunications equipment and support system suppliers can use this documentto guide the design and building of equipment to improve network survivability performance.1.4 OutlineSection 2 provides an overview of related work at the
32、 different national and international standards bodies, as well asat other industry forums and committees. Section 3 is an introduction to the Technical Report. Section 4 discussesthe challenge of changing network traffic characteristics in the PTN with the advent of the Internet. Section 5 isdevote
33、d to Internet and discusses the Internet industry structure, architecture, technologies, reliability/availabilityobjectives, Quality of Service (QoS), and trends. Section 6 addresses the PTN architecture and somereliability/availability objectives for a hypothetical reference connection of a local e
34、xchange PTN. Section 7focusses on the interactions between the Internet and the PTN. In particular, it provides connection architectures,failure modes, parameter descriptions and measurements, as well as failure analysis methods. Section 8 providessome reliability/survivability solutions and suggest
35、ions to general industry, including failure prevention/mitigation1The term PTN, as used in this Technical Report, encompasses the Public Switched Telephone Network (PSTN), the PublicPacket Switched Network (PPSN), and leased facilities. The PTN contains publically available network elements that can
36、 beleased by Internet Service Providers (ISPs) and used in their networks.Technical Report No. 552methods. Section 9 gives some recommendations to standards organizations. Finally, Section 10 summarizes thefindings of this Technical Report.2. Related Work2.1 T1A1 Technical SubcommitteeIn addition to
37、 the T1A1.2 Working Group (WG), the following three T1A1 WGs are involved in work related toInternet: T1A1.3, T1A1.5, and T1A1.7. T1A1.3 WG on Performance of Digital Networks and Services has project T1A1-14, Specification andAllocation of Internet Services Performance. Under this project, T1A1.3 pl
38、ans to complete (by the end of1998) a new American National Standard (“T1.5IP”) that defines performance parameters for thecharacterization of end-to-end public data communication services using the Internet Protocol (IP). T1A1.3work on IP performance will include the preparation of United States (U
39、.S.) inputs to ITU-T2Study Group13 (Question 13). That group is beginning the development of a corresponding new ITU-TRecommendation (“I.35IP”). For additional information, contact the T1A1.3 Chair (Garry Couch,). T1A1.5 WG on Multimedia Communications Coding and Performance has project T1A1-15, Cod
40、ingImplications and Performance Specifications for Multimedia Communications on Internet Services. Underthis project, T1A1.5 plans to complete (by the first quarter of 1999) a new American National Standard(“T1.8Internet”) that will define Internet Reference Connections for transporting multimedia s
41、ervices.Subsequently, supplements to T1.8Internet will define (i) associated service performance parameters andmeasurement methods at the connection interface points, and (ii) corresponding performance specificationsfor various service categories. The initial emphasis of the T1A1.5 work will be on v
42、ideo teleconferencingand video telephony applications. For additional information, contact the T1A1.5 Chair (Warner Johnston,). T1A1.7 WG on Signal Processing and Network Performance for Voiceband Services Processing has projectT1A1-16, Interaction between the Public Switched Telephone Network PSTN
43、and Other Networks andTerminals. Under this project, T1A1.7 will investigate voice and voiceband data performance issues oftransport over non-PSTN networks, including IP-based networks, which may be interconnected with thePSTN. Two new Technical Reports will be published. The first will consider per
44、formance and the secondwill define statistical tools for measuring end-to-end performance. For additional information, contact theT1A1.7 Chair (Barry Lerich, ).2.2 International Standards WorkThe following ITU-T study groups are involved in work related to network survivability performance: Study Gr
45、oup 2 addresses the overall operation of telecommunication networks. This work addressesvarious design alternatives for survivable networks Study Group 4 is studying the restoration of failed international exchanges, and transmission systems Study Group 5 is studying survivability issues for the out
46、side plant Study Group 11 is studying Common Channel Signaling (CCS) networks and switching systems Study Group 13 (Question 7) is working on a baseline document on “ATM Network SurvivabilityArchitectures and Mechanisms,” and (Question 13) is working on IP performance2International Telecommunication
47、 Union Telecommunications standardization sector.Technical Report No. 553 Study Group 15 is addressing transmission system requirements, including the protection requirements forSynchronous Digital Hierarchy (SDH) rings, and restoration requirements for Digital Cross-connectSystems (DCSs).2.3 Intern
48、et Governing and Standards BodiesRepresentatives of many of the suppliers actively participate in the Internet standards bodies along with the networkand content service providers, researchers, and representatives of user communities of interest3. This wide base ofparticipants, and the open structur
49、e and consensus-building operation of the Internet standards organizations basedon voluntary membership, in turn, cultivates the development, standardization, implementation, and deployment ofmany new services and applications at a fast pace.Appendix B provides a roadmap of the Internet governing and standards bodies. Namely, these bodies are: Internet Society (ISOC) Internet Architecture Board (IAB) Internet Engineering Steering Group (IESG) Internet Engineering Task Force (IETF) Internet Assig
