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Versions: 00                                                            
Internet Engineering Task Force                                I. Brown
INTERNET-DRAFT                                University College London
Expiration Date: 31 January 2003                              July 2002

     Terms of Reference for an Emergency Telecommunications Service

Status of This Memo

   This document is an Internet-Draft and is in full conformance with
   all provisions of Section 10 of RFC2026.

   Internet-Drafts are working documents of the Internet Engineering
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   Copyright (C) Internet Society 2002.  All rights reserved.
   Reproduction or translation of the complete document, but not of
   extracts, including this notice, is freely permitted.


   An Emergency Telecommunications Service gives authorised emergency
   personnel a higher probability of successful communication under
   high network load conditions. This document explains the different
   terms and acronyms used in defining and implementing this service,
   and is intended to be used as a common basis for negotiations when
   emergency service providers are contracting with telecommunications
   operators to provide the service. It can also be used in procurement
   of and tendering for ETS provision.

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1. Definitions

Assured Forwarding (AF)

   A set of DiffServ Per-Hop Behaviours that group packets into one of
   four independent classes, each of which has three levels of drop
   precedence [Heinanen99].


   A protocol that provides authentication, authorisation and
   accounting services between home and remote networks and their
   users [Calhoun02].

Differentiated Services Code Point (DSCP)

   The value used in the DiffServ field of a packet header that selects
   a specific Per-Hop Behaviour [Grossman02].

Differentiated Services (DiffServ)

   A mechanism for classifying traffic flows into aggregates and
   providing specific forwarding treatment within a network. Flows
   are classified and policed at the edge of a network and forwarded
   according to the service provider's policies

Expedited Forwarding (EF)

   A DiffServ Per-Hop Behaviour that provides a flow with low loss,
   jitter and delay. This is achieved by ensuring that the output rate
   of an EF queue in a router is higher than the arrival rate of EF-
   marked packets over short and long time intervals [Davie02].

Government Emergency Telecommunications Service (GETS)

   A scheme operated under contract by US telecommunications providers
   that provides a High Probability of Completion for calls made by
   authorised emergency personnel in the Public Switched Telephone
   Network [Folts02].

Global System for Mobile communications (GSM)

   The family of European Telecommunications Standards Institute
   standards for first generation digital mobile telecommunications,
   used in many countries around the world for public land mobile
   networks. Contains an extended version of MLPP to allow precedence
   and preemption for calls from authorised users.

High Probability of Completion (HPC)

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   Emergency prioritised calls in the Public Switched Telephone Network
   are given a higher chance of successful setup by the network. These
   calls can be queued, exempted from restrictive management controls
   and routed via alternate carriers when they encounter congestion

International Emergency Multimedia Service (IEMS)

   A counterpart to the International Emergency Preference Scheme that
   provides enhanced treatment for a wide range of multimedia services

International Emergency Preference Scheme (IEPS)

   An International Telecommunications Union standard that provides a
   High Probability of Completion for calls made by authorised emergency
   personnel in the international Public Switched Telephone Network

Integrated Services (IntServ)

   An extension to the Internet architecture to support real-time
   services for communications sessions [Braden94]. Bandwidth can be
   reserved using the Resource ReSerVation Protocol [Braden97]. IntServ
   is usually only supported within specific domains.

Internet Protocol Security (IPSec)

   A set of extensions to the standard Internet Protocol that allows
   packets or the data they contain to be encrypted and signed,
   ensuring their confidentiality and integrity [Thayer98].

ISDN User Part (ISUP)

   A set of protocols used in SS7 networks to support ISDN services
   such as controlling telephone calls, and network maintenance such
   as blocking or resetting circuits [ITU99]. The ISUP Initial Address
   Message is used to carry the National Security/Emergency
   Preparedness codepoint which marks a GETS call as prioritised.

Multimedia Internet Keying (MIKEY)

   A key agreement protocol designed to meet the low latency
   requirements of real-time media streams and to work with signalling
   protocols such as SIP [Arkko02].

Multi-Level Precedence and Preemption (MLPP)

   A system that allows higher-priority telephony calls to receive
   resources ahead of (and if necessary to tear down) lower priority
   calls [ITU90].

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National Security/Emergency Preparedness (NS/EP)

   A codepoint set for GETS calls in the Calling Party Category of the
   SS7 ISUP Initial Address Message, indicating that the setup should
   have a High Probability of Completion.

Per-Hop Behaviour (PHB)

   The forwarding behaviour applied by a DiffServ node to flows marked
   with a specific DSCP.

Real-time Transport Protocol

   A network-independent end-to-end transport protocol for real-time
   data such as audio,video and simulation results [Schulzrinne96].

Secure Real-time Transport Protocol

   A Real-time Transport Protocol profile that provides
   confidentiality, authentication and replay protection for RTP and
   associated control traffic [Baugher02].

Session Initiation Protocol (SIP)

   A signalling protocol used to set up, manage and tear down
   communications sessions between one or more participants. Telephone
   calls, video conferences and multimedia distribution are all
   supported [Rosenberg02].

Signalling System No. 7 (SS7)

   The procedures and protocols by which network elements in the Public
   Switched Telephone Network exchange information over a digital
   signalling network for call setup, routing and control [ITU93].

Telephony Routing over IP (TRIP)

   A protocol that allows IP telephony gateways to advertise and
   exchange routes to specific numbers in the Public Switched
   Telephone Network [Rosenberg00].

Traffic Class

   DiffServ packets are marked as part of a specific traffic
   aggregate using a DiffServ Code Point. This DSCP goes in
   the traffic class field of the packet header [Grossman02].

Transport Layer Security (TLS)

   A set of cryptographic protocols that allow processes running on two
   separate hosts to communicate across an insecure network such as the
   Internet with protection against eavesdropping and modification of

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   data [Dierks99].

2. Security Considerations

   The security aspects of an Emergency Telecommunications Service are
   described in [Brown02].

3. Acknowledgements

   Thanks to Alistair Munro for comments on this document.

4. Author's Address

   Ian Brown
   Department of Computer Science
   University College London
   Gower Street
   London WC1E 6BT
   United Kingdom

   Phone: +44 20 7679 3704
   Fax: +44 20 7387 1397
   E-mail: I.Brown@cs.ucl.ac.uk

5. Informative References

   [ANSI93] ANSI Recommendation T1.631, "Signaling System No. 7 (SS7) -
   High Probability of Completion (HPC) Network Capability", 1993.

   [Arkko02] Arkko, J., Carrara, E., Lindholm, F., Naslund, M. and
   K. Norrman, "MIKEY: Multimedia Internet KEYing", Internet draft,
   July 2002.

   [Blake98] Blake, S., Black, D., Carlson, M., Davies, E., Wang, Z.,
   and W. Weiss, "An Architecture for Differentiated Services", RFC
   2475, December 1998.

   [Baugher02] Baugher, M., Blom, R., Carrara, E., McGrew, D., Naslund,
   M., Norrman, K., and D. Oran, "The Secure Real-time Transport
   Protocol", IETF work-in-progress, June 2002.

   [Braden94] Braden, B., Clark, D. and S. Shenker, "Integrated
   Services in the Internet Architecture: an Overview", RFC 1633, June

   [Braden97] Braden, B. (Ed.), "Resource ReSerVation Protocol (RSVP)
   -- Version 1 Functional Specification", RFC 2205, September 1997.

   [Brown02] Brown, I., "A Security Framework for Emergency
   Communications", IETF work-in-progress, June 2002.

   [Calhoun02] Calhoun, P., Arkko, J., Guttman, E., Zorn, G. and J.

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   Loughney, "Diameter Base Protocol", IETF work-in-progress, April

   [Davie02] Davie, B. et al., "An Expedited Forwarding PHB (Per-Hop
   Behavior)", RFC 3246, March 2002.

   [Dierks99] Dierks, T. and C. Allen, "The TLS Protocol Version 1.0",
   RFC 2246, January 1999.

   [Folts02] Folts, H. and C. Beard, "Requirements for Emergency
   Telecommunication Capabilities in the Internet", Internet draft,
   June 2002.

   [Grossman02] D. Grossman, "New Terminology and Clarifications for
   Diffserv", RFC 3260, April 2002.

   [Heinanen99] Heinanen, J., Baker, F., Weiss, W. and J. Wroclawski,
   "Assured Forwarding PHB Group", RFC 2597, June 1999.

   [ITU90] ITU-T Recommendation I.255.3, "Multilevel precedence and
   preemption service (MLPP)", July 1990.

   [ITU93] ITU-T Recommendation Q.700, "Introduction to CCITT Signalling
   System No. 7", March 1993.

   [ITU99] ITU-T Recommendation ITU-T Q.764, "Signaling System
   No. 7; ISDN User Part Signaling procedures", December 1999.

   [ITU00] ITU-T Recommendation E.106, "Description of an International
   Emergency Preference Scheme (IEPS)", March 2000.

   [ITU02] ITU-T Draft Recommendation F.706, "International Emergency
   Multimedia Service", 2002.

   [Rosenberg00] Rosenberg, J. and H. Schulzrinne, "A Framework for
   Telephony Routing over IP", RFC 2871, June 2000.

   [Rosenberg02] Rosenberg, J. et al, "SIP: Session Initiation Protocol",
   RFC 3261, June 2002.

   [Schulzrinne96] Schulzrinne, H., Casner, S., Frederick, R. and V.
   Jacobson, "RTP: A Transport Protocol for Real-time Applications", RFC
   1889, January 1996.

   [Thayer98] Thayer, R., Doraswamy, N. and R. Glenn, "IP Security
   Document Roadmap", RFC 2411, November 1998.

6. Full Copyright Statement

   Copyright (C) The Internet Society (2002).  All Rights Reserved.

   This document and translations of it may be copied and furnished to

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   others, and derivative works that comment on or otherwise explain
   it or assist in its implementation may be prepared, copied,
   published and distributed, in whole or in part, without restriction
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   However, this document itself may not be modified in any way, such
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   The limited permissions granted above are perpetual and will not be
   revoked by the Internet Society or its successors or assigns.

   This document and the information contained herein is provided on

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