ATIS T1 TR 84-2004 IP Network Traffic Priorities and ETS.pdf

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1、 TECHNICAL REPORT T1.TR.84-2004 Technical Report on IP Network Prioritiess and ETS Prepared by T1A1.2 Working Group on Network Survivability Performance Problem Solvers to the Telecommunications Industry A Word from ATIS and Committee T1 Established in February 1984, Committee T1 develops technical

2、standards, reports and requirements regarding interoperability of telecommunications networks at interfaces with end-user systems, carriers, information and enhanced-service providers, and customer premises equipment (CPE). Committee T1 is sponsored by ATIS and is accredited by ANSI. T1.TR.84-2004 P

3、ublished by Alliance for Telecommunications Industry Solutions 1200 G Street, NW, Suite 500 Washington, DC 20005 Committee T1 is sponsored by the Alliance for Telecommunications Industry Solutions (ATIS) and accredited by the American National Standards Institute (ANSI). Copyright 2004 by Alliance f

4、or Telecommunications Industry Solutions 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. For information contact ATIS at 202.628.6380. ATIS is online at . Printed in

5、 the United States of America. T1.TR.84-2004 Technical Report on IP Network Traffic Priorities and ETS Secretariat Alliance for Telecommunications Industry Solutions Abstract This Technical Report (TR) identifies the need for establishing a set of priorities for traffic over IP networks. It proposes

6、 that communications services over IP networks be prioritized such that critical services have a higher probability of successful session set up and completion than other types of services. This report also identifies the need for signaling traffic priorities across IP networks and networks of diffe

7、rent technologies e.g., an originating ETS call over a Wireless circuit-switched access network transported over an IP backbone, with termination over a circuit-switched Wireless egress network. Traffic priority levels over the multiple technologies require mapping agreement, and appropriate signali

8、ng protocols will need to be developed such that these levels are recognized. T1.TR.84-2004 ii FOREWORD This Technical Report (TR) provides an assessment of the role of traffic priorities in Emergency Telecommunications Service in evolving IP network architectures. This is intended for providers of

9、IP-based communications networks and services, communications equipment suppliers, and government agencies responsible for addressing emergency situations. Suggestions for enhancement of this report are welcome. These should be sent to the Alliance for Telecommunications Industry Solutions, Suite 50

10、0, 1200 G Street N.W., Washington, D.C. 20005. Working Group T1A1.2 on Network Survivability Performance, which developed this report, has the following officers and participants: O. Avellaneda, T1A1.2 Chair S. Makris, T1A1.2 Vice Chair F. Kaudel, T1A1.2 Chief Editor P. Tarapore and A. Webster, T1A1

11、.2 Technical Editors C. Underkoffler, ATIS Chief Editor Active Participants: O. Avellaneda J. Bennett W. Downum C. Dvorak P. Kimbrough J. Lankford S. Makris A. McCain A. Nguyen R. Paterson G. Stanek P. Tarapore K. Trahan A. Thiessen J. Trakinat A. Webster R. Wohlert T1.TR.84-2004 iii TABLE OF CONTEN

12、TS 0 EXECUTIVE SUMMARY 1 1 PURPOSE, SCOPE, APPLICATION, AND OUTLINE 1 1.1 PURPOSE.1 1.2 SCOPE .1 1.3 APPLICATION 1 1.4 OUTLINE .2 2 INTRODUCTION 2 3 RELATED WORK.3 4 GETS HISTORICAL PERSPECTIVE .3 5 ETS - QUALITY OF SERVICE REQUIREMENTS IN EVOLVING IP NETWORKS 4 6 ETS AND CONNECTION ADMISSION CONTRO

13、L (CAC) .4 6.1 IP NETWORK CAC PRIORITIES AND EMERGENCY SERVICES.5 6.2 CAC PRIORITY LEVELS.5 6.3 IP CONTROL PLANE TRAFFIC 5 7 ETS AND SERVICE RESTORATION.5 8 ETS PRIORITY AND SIGNALING.6 8.1 PRIORITY SIGNALING IN IP NETWORKS.6 8.2 PRIORITY SIGNALING BETWEEN NETWORKS WITH DIFFERENT TECHNOLOGIES 7 9 CO

14、NCLUSIONS.8 10 BIBLIOGRAPHY.8 11 DEFINITIONS9 12 ABBREVIATIONS AND ACRONYMS.9 TECHNICAL REPORT ON T1.TR.83-2004 IP Network Traffic Priorities and ETS 0 EXECUTIVE SUMMARY This Technical Report (TR) provides an assessment of the role of traffic priorities for Emergency Telecommunications Service (ETS)

15、 in evolving IP architectures. It is intended as a guide for service providers, equipment vendors, and government agencies responsible for addressing emergency situations. 1 PURPOSE, SCOPE, APPLICATION, AND OUTLINE 1.1 Purpose Todays IP networks offer a single “Best Effort” service class to all form

16、s of communications traffic. No mechanisms are in place to distinguish between critical services (e.g., ETS and E911 services) from other types of commercial traffic. Under conditions of congestion such as traffic overloads or network failures, all service types receive equal probability of session

17、set up and completion. This TR identifies the need for establishing a set of priorities for traffic over IP networks. Specifically, this TR proposes that communications services over IP networks be prioritized such that critical services have a higher probability of successful session set up and com

18、pletion than other types of services. This TR also identifies the need for signaling traffic priorities across IP networks and networks of different technologies e.g., an originating ETS call over a Wireless circuit-switched access network transported over an IP backbone, with termination over a cir

19、cuit-switched Wireless egress network. Traffic priority levels over the multiple technologies require mapping agreement, and appropriate signaling protocols will need to be developed such that these levels are recognized. 1.2 Scope The need for service priority classification in IP networks for conn

20、ection admission control and service restoration is emphasized. Also emphasized is the need to maintain end-to-end service priority between IP networks as well as between IP networks and networks of different technologies (e.g., Wireless 3GPP). Thus the need for signaling service priorities for crit

21、ical services such as ETS is discussed. This report complements the ongoing work on Emergency Telecommunications Service building on Technical Report T1.TR-79-2003, Overview of Standards in Support of Emergency Telecommunications Service (ETS) 1. 1.3 Application The priority aspects dealt with in th

22、is report pertain to IP network architectures. Necessary signaling aspects for priority indicators between IP networks and networks of other technologies, such as wireless/mobile radio and circuit-switched networks, are also discussed. T1.TR.84-2004 21.4 Outline Clause 2 provides an introduction. Re

23、lated standards activities are presented in clause 3. Clause 4 provides a brief description of priority treatment in the existing Government Emergency Telecommunications Service (GETS) for calls in the Public Switched Telephone Network (PSTN). Quality of Service (QoS) expectations for ETS, are brief

24、ly discussed in clause 5. Detailed discussions on Connection Admission Control (CAC) priority are presented in clause 6. A discussion on restoration priority is presented in clause 7. Clause 8 examines the need to signal the desired QoS (and therefore, to indicate the required traffic priorities) wi

25、thin an IP environment and between IP networks and other network environments such as wireless/mobile radio access networks. Conclusions are presented in clause 9. 2 INTRODUCTION IP networks currently offer a single “Best Effort” service class for all types of packet traffic. In the traditional circ

26、uit-switched PSTN, SS7 signaling is done over a separate network. That is not the case in IP networks all packets are treated equally regardless of whether they represent the control plane or the bearer (or user) plane. However, it is becoming clear that certain types of communications traffic are d

27、eemed more critical than others. Examples of critical traffic include control plane traffic (e.g., critical network management/control and signaling traffic) as well as user plane traffic associated with services such as E911 and ETS. Many initiatives are underway in industry standards development o

28、rganizations to establish a preferential service for emergency recovery operations for disaster events such as hurricanes, earthquakes, and terrorist attacks. These initiatives have identified several high-level requirements for the effective offering of ETS over evolving wireless and wireline netwo

29、rks 1 (e.g., IP-based networks). This TR builds on previous efforts on traffic priority in IP networks 2, 3. Priority is presented as a reliability function that facilitates successful establishment and usage of emergency communications services. In that sense, service priority can be considered as

30、an integral component of QoS in addition to various performance criteria (e.g., delay, packet loss) associated with the transaction type (e.g., voice, data, multimedia). Priority therefore is a necessary component for network functions such as Connection Admission Control (CAC) when applied to criti

31、cal services such as ETS. The discussions presented in this report on priority can serve as useful guidance to industry members in advancing the necessary protocols and related signaling mechanisms, in evolving networks, to support critical services such as ETS. In summary, the goals of this TR are

32、the following: Recognize the importance of traffic priorities in IP networks such that critical services such as ETS and E911 are given a higher probability of successful completion over other types of customer traffic. Highlight the need to provide priority for signaling traffic between IP networks

33、 and networks of other technologies (e.g., Wireless). T1.TR.84-2004 33 RELATED WORK A significant amount of work on ETS requirements is ongoing in various standards bodies. A detailed list of such efforts can be found in T1.TR.79-2003, Overview of Standards in Support of Emergency Telecommunications

34、 Service (ETS)” 1. In the ITU-T, Recommendation E.361 4has progressed work on the definition of reliability and priority parameters for QoS service classes. This Recommendation also provides useful insights on the priority signaling across multiple networks. 4 GETS HISTORICAL PERSPECTIVE Currently,

35、in the United States, the Government Emergency Telecommunications Service (GETS) supports emergency recovery operations. GETS is a communications service provided by the Office of the Manager, National Communications System (OMNCS) that supports federal, state, and local government, industry, and no

36、n-profit organization personnel in performing their National Security and Emergency Preparedness (NS/EP) missions. GETS provides emergency access and priority processing for voice calls in the local and long distance segments of the PSTN. It is intended for use in an emergency or crisis situation du

37、ring which the probability of completing a call over normal or other alternate telecommunication means has significantly decreased. GETS uses three major types of networks: 1. Long-distance networks provided by Inter-exchange Carriers (IXCs). 2. The local networks provided by Local Exchange Carriers

38、 (LECs), such as the Bell Operating Companies and Independent Telephone Companies (ITCs), cellular carriers, and personal communications services (PCS). 3. Government-leased networks, including the Federal Telecommunications System (FTS) and the Defense Information System Network (DISN). GETS is acc

39、essed through a universal access number using common telephone equipment. The call is routed at high priority into an IXC that supports GETS. A prompt will direct the caller to enter a PIN and the desired destination phone number. Once the caller has been authenticated1as a valid user, the call is i

40、dentified as an NS/EP call and receives special treatment, such as enhanced routing services and capabilities. GETS traffic receives priority treatment over normal traffic through: Mechanisms such as trunk queuing, trunk sub-grouping, or trunk reservation. Exemption from protective network managemen

41、t controls, which are used to reduce network congestion. Invocation of the High Probability of Completion (HPC) 5network capability to identify the call as an NS/EP call and to provide priority for call setup signaling. 1If the GETS call cannot reach the authentication system in the first IXC the ca

42、ll is routed to, it may use Alternate Carrier Routing to reroute into a second IXC. T1.TR.84-2004 4These features enhance the capability of NS/EP calls to be completed in congested networks. GETS will not preempt public traffic, nor are there multiple levels of priority in GETS. Going forward, the k

43、ey issue here is that GETS (along with E911) emergency traffic is afforded a higher priority for successful call completion than ordinary voice calls in the PSTN network. 5 ETS - QUALITY OF SERVICE REQUIREMENTS IN EVOLVING IP NETWORKS ETS can provide multiple forms of communications media voice, dat

44、a, video, 1 etc. That is a major difference between ETS offerings over evolving networks and GETS which is solely a voice-based service. In evolving IP networks, QoS expectations for ETS need to be examined from two perspectives performance QoS objectives related to the type of packet transaction an

45、d reliability expectations related to the type of service. In IP networks, packet performance objectives such as packet loss, delay, etc., are grouped into six QoS classes specified in ITU-T Recommendation Y.1541 6. These classes can support a wide range of applications such as voice, data, and mult

46、imedia applications. To date, no mechanisms exist for implementation of these Y.1541 classes, though initial work on signaling requirements for requesting these classes have commenced. Nonetheless, it is conceivable that future ETS sessions will request an appropriate Y.1541 QoS class. It is equally

47、 important to note that depending on the severity of the emergency, network conditions may have degraded to a state such that the desired performance criteria may not be met for all ETS transactions 1. Reliability expectations may be met by the setup of a high priority link or “connection” such as a

48、 Multi-Protocol Label Switching (MPLS) Label Switched Path (LSP) over which an IP transaction can be routed in the network. In this case, priority is associated with the type of service. For example, critical services such as ETS require a higher priority for establishing successful call completions

49、 than other types of services. Mechanisms used to achieve QoS objectives include call and connection routing methods and QoS resource allocation methods to facilitate call setup such as bandwidth allocation, priority routing, priority queuing, and transport restoration. Thus, two aspects of the session are important 1) performance criteria related to the transaction type (e.g., voice, data, multimedia); and 2) priority class related to the type of service. This is the motivation for developing a set of suggested