IPTEL WG J. Peterson
Internet-Draft NeuStar
Expires: April 27, 2003 October 27, 2002
The Calling Party's Category tel URL Parameter
draft-peterson-tel-cpc-01
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Copyright Notice
Copyright (C) The Internet Society (2002). All Rights Reserved.
Abstract
This document specifies a new parameter for the tel URL [1] that
represents the Calling Party's Category, a parameter used in SS7 ISUP
[2] signaling.
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Table of Contents
1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . . . 3
2. Parameter Definition . . . . . . . . . . . . . . . . . . . . . . 3
3. Usage . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 4
4. Security Considerations . . . . . . . . . . . . . . . . . . . . 4
5. IANA Considerations . . . . . . . . . . . . . . . . . . . . . . 4
References . . . . . . . . . . . . . . . . . . . . . . . . . . . 5
Author's Address . . . . . . . . . . . . . . . . . . . . . . . . 5
Full Copyright Statement . . . . . . . . . . . . . . . . . . . . 6
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1. Introduction
ISUP defines a Calling Party's Category (CPC) parameter that
characterizes the station used to originate a call and carries other
important state that can describe the originating party. When
telephone numbers are contained in URLs, such as the tel URL, it may
be desirable to communicate any CPC associated with that telephone
number or, in the context of a call, the party calling from it.
Note that in some networks (including North America), the Originating
Line Information (OLI) parameter is used to carry this information in
ISUP rather than the CPC parameter. Legacy multifrequency (MF)
signaling networks carry this information in the ANI II Digits. The
tel URL parameter specified in this document is designed to carry
data from these sources as well.
2. Parameter Definition
The Calling Party's Category is represented as a tel URL parameter.
The ABNF syntax is as follows:
cpc = cpc-tag "=" cpc-value
cpc-tag = "cpc"
cpc-value = string
CPC values (``cpc-value'' strings) must be registered with IANA. The
following values are pre-registered by this document:
ordinary: The caller has been identified, and has no special
features.
priority: This call has priority/emergency status.
data: This call will contain voice-band data.
test: This is a test call that has been originated as part of a
maintenance procedure.
operator: The call was generated by an operator position.
payphone: The calling station is a payphone.
prison: The calling station is in a prison.
unknown: The CPC could not be ascertained.
An example of the syntax of the CPC parameter (in a small fragment of
a SIP message) is given below:
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INVITE sip:bob@biloxi.com SIP/2.0
To: "Bob" <sip:bob@biloxi.com>
From: <tel:+17005554141;cpc=payphone>;tag=1928301774
3. Usage
The CPC is generally useful only when describing the originator of a
telephone call. Therefore, when this parameter is used in an
application such as SIP, it is recommended that the parameter be
applied to URLs that characterize the originator of a call (such as a
SIP URI or tel URL in the From header field of a SIP message).
It is anticipated that this URL will be used primarily by gateways
that interwork ISUP networks with SIP networks. Various SIP network
intermediaries might consult the CPC as they make routing decisions,
although no specific behavior is prescribed in this document. While
no specific mapping of the various ISUP parameters that contain CPC
data is offered in this document, creating such a mapping would be
trivial.
If the CPC parameter is not present, consumers of the CPC should
treat the URL as if it specified a CPC of "unknown".
Generally, only one instance of the CPC will be associated with a
particular URL.
4. Security Considerations
The information contained in the CPC parameter may be of a private
nature, and it may not be appropriate for this value to be revealed
to the destination user (typically it would not be so revealed in the
PSTN).
Otherwise, this mechanism adds no new security considerations to
those discussed in RFC2806 [1].
5. IANA Considerations
This document requests the creation of an IANA registry for Calling
Party's Category values. The values of the CPC parameter in use in
ISUP are unfortunately quite specific to national networks, and thus
it is very difficult to uncover all the usages that may be in place
in various networks. Note that in North American networks, the
Originating Line Information parameter contains information common
found in the Calling Party's Category elsewhere; it is therefore
legitimate to register values associated with the Originating Line
Information in this registry.
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In order to file a registration, interested parties must contact IANA
and supply them with both a new ``cpc-value'' and a short reason
phrase describing the usage of the new CPC. Some values are given in
Section 2; we ask that these values be pre-registered upon
publication of this document as an RFC. It is not expected that this
registry will require any expert supervision.
References
[1] Vaha-Sipila, A., "URLs for Telephone Calls", RFC 2806, April
2000.
[2] International Telecommunications Union, "Recommendation Q.763:
Signalling System No. 7: ISDN user part formats and codes",
September 1997, <http://www.itu.int>.
[3] Handley, M., Schulzrinne, H., Schooler, E. and J. Rosenberg,
"SIP: Session Initiation Protocol", RFC 2543, March 1999.
Author's Address
Jon Peterson
NeuStar, Inc.
1800 Sutter St
Suite 570
Concord, CA 94520
US
Phone: +1 925/363-8720
EMail: jon.peterson@neustar.biz
URI: http://www.neustar.biz/
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