SIPPING D. York
Internet-Draft Voxeo
Intended status: Informational T. Asveren
Expires: August 24, 2008 Sonus
February 21, 2008
P-Charge-Info - A Private Header (P-Header) Extension to the Session
Initiation Protocol (SIP)
draft-york-sipping-p-charge-info-01
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Copyright (C) The IETF Trust (2008).
Abstract
This document describes 'P-Charge-Info', a private Session Initiation
Protocol (SIP) header (P-header) used by a number of equipment
vendors and carriers to convey simple billing information.
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Table of Contents
1. Overview . . . . . . . . . . . . . . . . . . . . . . . . . . . 3
2. Requirements Language . . . . . . . . . . . . . . . . . . . . . 4
3. The P-Charge-Info Header . . . . . . . . . . . . . . . . . . . 4
3.1. Applicability Statement for the P-Charge-Info header . . . 4
3.2. Usage of the P-Charge-Info header . . . . . . . . . . . . . 4
3.2.1. Procedures at the UA . . . . . . . . . . . . . . . . . 4
3.2.2. Procedures at the Proxy . . . . . . . . . . . . . . . . 4
3.3. Examples of Usage . . . . . . . . . . . . . . . . . . . . . 4
4. Formal Syntax . . . . . . . . . . . . . . . . . . . . . . . . . 5
5. IANA Considerations . . . . . . . . . . . . . . . . . . . . . . 5
6. Security Considerations . . . . . . . . . . . . . . . . . . . . 6
7. References . . . . . . . . . . . . . . . . . . . . . . . . . . 6
7.1. Normative References . . . . . . . . . . . . . . . . . . . 6
7.2. Informative References . . . . . . . . . . . . . . . . . . 6
Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . . 6
Intellectual Property and Copyright Statements . . . . . . . . . . 8
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1. Overview
In certain network configurations, it is desirable to decouple the
Caller ID from the number used for billing purposes. This document
describes the current usage of 'P-Charge-Info', a private SIP header,
to provide simple billing information and requests the registration
of this header with IANA as required by section 4.1 of RFC 3427
[RFC3427].
In a typical configuration, "Caller ID" is derived from one of the
following SIP headers:
o Remote-Party-ID
o P-Asserted-Identity
o From (in the absence of the other two)
This number is typically presented to the receiving UA where it is
usually displayed for the end user. It is also typically used for
billing purposes by the network entities involved in carrying the
session.
However, in a distributed environment the "Caller ID" presented to
the receiving UA may not reflect the actual reality of the underlying
network in terms of costs incurred on the PSTN. This may result in
excessive charging of one carrier by another based on the erroneous
assumption that the call was originating from a different point on
the PSTN.
There exists a need for a way to pass an additional billing
identifier that can be used between network entities in order to
correctly bill for services. At least one equipment provider, Sonus
Networks, and several carriers have been using the "P-Charge-Info"
header for the last 2-3 years as a simple mechanism to exchange this
billing identifier.
It should be noted that the 3GPP has also recognized the need for
such a billing identifier and in section 4.6 of RFC 3455 [RFC3455]
established a SIP P-Header, "P-Charging-Vector", to provide similar
information. This header, though, is designed for use within 3GPP
environments and thus includes parameters appropriate within a 3GPP
context. It also allows for the use of any general value as the
billing identifier whereas P-Charge-Info, as noted below,
specifically requires a SIP URI as the content.
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2. Requirements Language
The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT",
"SHOULD", "SHOULD NOT", "RECOMMENDED", "MAY", and "OPTIONAL" in this
document are to be interpreted as described in RFC 2119.
3. The P-Charge-Info Header
3.1. Applicability Statement for the P-Charge-Info header
The P-Charge-Info header is applicable within a single private
administrative domain or between different administrative domains
where there is a trust relationship between the domains.
3.2. Usage of the P-Charge-Info header
The P-Charge-Info header is used to convey information related to
billing record for a particular call. The P-Charge-Info header is
typically inserted by the SIP proxy on the originating network.
3.2.1. Procedures at the UA
The P-Charge-Info header may be inserted by PSTN gateways acting as a
SIP UA, either through local policy or as a result of information
received via PSTN signaling, e.g. the charge parameter in an ISUP IAM
message.
The P-Charge-Info header is not used/interpreted by a regular (i.e.
non-gateway) UA and should not normally be seen by such a UA. If the
header is transmitted to such a UA, the UA should ignore the header.
3.2.2. Procedures at the Proxy
A SIP proxy that supports this extension and receives a request,
typically a SIP INVITE, without the P-Charge-Info header MAY insert a
P-Charge-Info header. The contents of the inserted header may be
decided based on local policy or by querying an external entity.
A SIP proxy that does not support this extension will pass any
received P-Charge-Info header unmodified in compliance with RFC 3261.
3.3. Examples of Usage
The content of the P-Charge-Info header is typically simply a SIP URI
used as a billing indicator. As such, an example would be as simple
as:
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P-Charge-Info: <sip:4075555555@1.2.3.4>
Any other applicable SIP URI could be used.
P-Charge-Info optionally includes the numbering plan indicator as an
additional parameter. This is used when an ISUP message is built
from a SIP message for scenarios where SIP is used to connect two
PSTN segments and needs to pass charging information between them.
An example of the usage of the optional header is:
P-Charge-Info: <sip:6835555555;npi=ISDN@10.10.7.21>
4. Formal Syntax
The Private Header specified in this document is described in both
prose and an augmented Backus-Naur Form (BNF) defined in RFC 2234.
Further, several BNF definitions are inherited from SIP and are not
repeated here. Implementors need to be familiar with the notation
and contents of SIP [1] and RFC 2234 [3] to understand this document.
The syntax of the P-Charge-Info header is described as follows:
P-Charge-Info = "P-Charge-Info" HCOLON charge-param * (SEMI
charge-param)
charge-param = (addr-spec) * (SEMI charge-params)
charge-params = (("npi" EQUAL npi-value))
npi-value = ("ISDN" / "DATA" / "TELEX" / "PRIVATE" / "SPARE0" /
"SPARE1" / "SPARE2" / "SPARE3" / "SPARE4" / "SPARE5" /
"SPARE6" / "SPARE7" )
5. IANA Considerations
This document defines a private SIP extension header field (beginning
with the prefixe "P-").
The extension is registered as a private extension field:
RFC Number: RFCXXXX [Note to IANA: Please fill in with the RFC number
of this specification.
Header Field Name: P-Charge-Info
Compact Form: none
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6. Security Considerations
Given that the information contained in the P-Charge-Info header will
be used for billing purposes the proxies that share this information
MUST have a trust relationship.
If an untrusted entity were inserted between the trusted entities, it
could potentially interfere with the billing records for the call.
If the SIP connections are not made over a private WAN, a mechanism
for securing the confidentiality and integrity of the SIP connection
should be used to protect the information.
7. References
7.1. Normative References
[RFC3427] Mankin, A., Bradner, S., Mahy, R., Willis, D., Ott, J.,
and B. Rosen, "Change Process for the Session Initiation
Protocol (SIP)", BCP 67, RFC 3427, December 2002.
7.2. Informative References
[RFC3455] Garcia-Martin, M., Henrikson, E., and D. Mills, "Private
Header (P-Header) Extensions to the Session Initiation
Protocol (SIP) for the 3rd-Generation Partnership Project
(3GPP)", RFC 3455, January 2003.
Authors' Addresses
Dan York
Voxeo Corporation
Burlington, VT
USA
Phone: +1-407-455-5859
Email: dyork@voxeo.com
URI: http://www.voxeo.com/
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Tolga Asveren
Sonus Networks
3 Paragon Way
Freehold, NJ 07728
USA
Email: tasveren@sonusnet.com
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