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
<draft-ietf-ieprep-reference-00.txt>
Status of This Memo
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Copyright
Copyright (C) Internet Society 2002. All rights reserved.
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Abstract
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].
Diameter
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
[Blake98].
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
[ANSI93].
International Emergency Multimedia Service (IEMS)
A counterpart to the International Emergency Preference Scheme that
provides enhanced treatment for a wide range of multimedia services
[ITU02].
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
[ITU00].
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
1994.
[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
2002.
[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
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published and distributed, in whole or in part, without restriction
of any kind, provided that the above copyright notice and this
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However, this document itself may not be modified in any way, such
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