Internet Engineering Task Force Ken Carlberg
INTERNET DRAFT UCL
September, 2002 Ran Atkinson
Extreme Networks
IP Telephony Requirements for
Emergency Telecommunication Service
<draft-carlberg-ets-telephony-00.txt>
Status of this Memo
This document is an Internet-Draft and is in full conformance with
all provisions of Section 10 of RFC2026 [1].
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Abstract
This document presents a list of requirements in support of Emergency
Telecommunications Service (ETS) within the context of IP telephony.
It is an extension to the general requirements presented in [3].
Solutions to these requirements are not presented in this document.
1. Introduction
Effective telecommunications capabilities can be imperative to
facilitate immediate recovery operations for serious disaster events,
such as, hurricanes, floods, earthquakes, and terrorist attacks.
Disasters can happen any time, any place, unexpectedly. Quick
response for recovery operations requires immediate access to any
public telecommunications capabilities at hand. These capabilities
include: conventional telephone, cellular phones, and Internet
access via online terminals, IP telephones, and wireless PDAs. The
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commercial telecommunications infrastructure is rapidly evolving to
Internet-based technology. Therefore, the Internet community needs to
consider how it can best support emergency management and recovery
operations.
1.1 Problem
Standards have been developed by other standards bodies concerning
emergency communications. As discussed in [2] and [3], some of these
standards, such as T1.693 [4], define specific indicators or labels
for emergency communications in SS7 networks. Certain requirements
must be defined in order to achieve peering services across hybrid
networks (networks that communicate between IP and other types of
networks such as that realized by the Public Switched Telephone
Network).
2. Scope
[2] has defined a set of general system requirements to support
Emergency Telecommunications Service (ETS). This document defines an
additional set of system requirements to achieve support for ETS
within the specific context of IP telephony. Solutions to
requirements are not defined. The document does not specify protocol
enhancements or specifications.
2.1 Out of Scope
An item that is not in scope of this document is mandating acceptance
and support of the requirements presented in this document. The IETF
does not mandate requirements or capabilities to independent networks
that comprise the Internet. As an example, IP Carriers might choose
not to operate any telephony-related gateways or services. The IETF
cannot and does not mandate that an IP Carrier deploy either
telephony-related gateways or telephony-related services. There is
an expectation that business contracts, for example Service Level
Agreements (SLA), will be used to satisfy those following
requirements that apply to service providers. Absence of an SLA
implies best effort service is provided.
It is assumed that some carriers will choose to offer ETS services
and that other carriers will choose not to offer ETS services. These
requirements do not apply to carriers that have chosen not to offer
ETS services.
3. IP Telephony Requirements
The requirements in this section relate only to Telephony Signalling
(e.g. SS7, DSS1, SIP) as used in Internet-based telephony services.
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They are an extension to the general requirements specified in [2].
The following requirements explicitly do not relate to IP-layer
mechanisms, such as Differentiated Services or Integrated Services.
1) Telephony signalling applications used with Internet-based
telephony MUST be able to carry labels.
2) The ability to carry labels MUST be extensible to support
various types and numbers of labels. A single binary value will
not be sufficient given the various labeling standards in existance
today.
3) Telephony signalling labels MUST have a mapping with the various
labels/markings used in other telephony based networks. This
includes existing labels defined for the PSTN. This ensures that
a telephone call that is placed over a hybrid infrastructure
(traditional PSTN over some portion(s) of the path, Internet
telephony over some other portion(s) of the path) can carry the
labels end-to-end with appropriate translation at PSTN/Internet
boundaries.
3.1 Value Added Requirements:
1) Alternate paths
Experience with GETS has shown the utility of alternate paths
to a destination to help facilitate emergency-related
communications. From the perspective of the Internet, this
utility may be difficult to achieve and have a more limited
benefit. Hence, we present this requirement as one that is
value added, but not to considered critical in supporting ETS.
Unlike the PSTN, the Internet routing system maintains awareness
of all paths to a destination. Further the Internet is
packet-based, rather than circuit-switched, so existing flows
will automatically be rerouted if an initial route ceases to be
available and an alternate route exists.
4. Security
Only authorised users or operators SHOULD be able to create non-
ordinary labels. Labels SHOULD have mechanisms to provide strong
end-to-end integrity during their transmission through the telephony
systems. Finally, in cases where labels are expected to be acted
upon by operators, these operators SHOULD have the capability of
authenticating the label on a received message or transmission in
order to prevent theft of service and reduce risk of denial of
service (e.g. by unauthorised users consuming any limited resources).
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Security is also discussed in the general requirements of [2], which
applies to section 3 above.
5. References
1 Bradner, S., "The Internet Standards Process -- Revision 3", BCP
9, RFC 2026, October 1996.
2 Carlberg, K., Atkinson, R., "General System Requirements for
Emergency Telecommunications Service", Internet Draft,
Work In Progress, September, 2002
3 Folts, H., et. al., "User Requirements for Emergency
Telecommunications Service", Internet Draft, Work In
Progress, September 2002
4 ANSI, "Signaling System No. 7(SS7): High Probability of
Completion (HPC) Network Capability, ANSI T1.631, 1993.
Ken Carlberg Ran Atkinson
University College London Extreme Networks
Department of Computer Science 3585 Monroe Street
Gower Street Santa Clara, CA
London, WC1E 6BT 95051 USA
United Kingdom
k.carlberg@cs.ucl.ac.uk rja@extremenetworks.com
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