wdiff rfc8496.original rfc8496.txt

Internet Engineering Task Force (IETF) D. York
Internet-Draft
Request for Comments: 8496 Individual
Intended status:
Category: Informational T. Asveren
Expires: January 1, 2019
ISSN: 2070-1721 Ribbon Communications
June 30,
October 2018

P-Charge-Info -

P-Charge-Info: A Private Header Field (P-Header) Extension to the
Session Initiation Protocol (SIP)
draft-york-p-charge-info-08

Abstract

This text documents the current usage of P-Charge-Info, an existing
private
Session Initiation Protocol (SIP) private header field (P-Header)
used to convey billing information about the party to be charged.
This P-Header is currently used in production by several equipment
vendors and carriers and has been in usage use since at least 2007. This
document is submitted to request details the registration of this header field with the Internet Assigned Numbers Authority (IANA). IANA.

Status of This Memo

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provisions of BCP 78 and BCP 79.

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This Internet-Draft will expire on January 1, 2019.
https://www.rfc-editor.org/info/rfc8496.

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Table of Contents

1. Overview . . . . . . . . . . . . . . . . . . . . . . . . . . 2 3
2. Requirements Language . . . . . . . . . . . . . . . . . . . . 3 4
3. Purpose of this This Document . . . . . . . . . . . . . . . . . . 4
4. Use Cases . . . . . . . . . . . . . . . . . . . . . . . . . . 4
5. The P-Charge-Info Header . . . . . . . . . . . . . . . . . . 4 5
5.1. Applicability Statement for the P-Charge-Info header
field Header
Field . . . . . . . . . . . . . . . . . . . . . . . . . . 4 5
5.2. Usage of the P-Charge-Info header field Header Field . . . . . . . . . 4 5
5.2.1. Procedures at the UA . . . . . . . . . . . . . . . . 5
5.2.2. Procedures at the Proxy . . . . . . . . . . . . . . . 5 6
5.3. Use-Case Example of Usage . . . . . . . . . . . . . . . . . . . . 6
6. Formal Syntax . . . . . . . . . . . . . . . . . . . . . . . . 6 7
7. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 7
7.1. Header Field . . . . . . . . . . . . . . . . . . . . . . 7
8. Security Considerations . . . . . . . . . . . . . . . . . . . 7
8.1. Trust Relationship . . . . . . . . . . . . . . . . . . . 7
8.2. Untrusted Peers . . . . . . . . . . . . . . . . . . . . . 7 8
8.2.1. Ingress from Untrusted Peers . . . . . . . . . 7 . . . 8
8.2.2. Egress to Untrusted Peers . . . . . . . . . . 8
9. Acknowledgements . . . . . . . . . . . . . . . . . . . . . . 8
10.
9. References . . . . . . . . . . . . . . . . . . . . . . . . . 8
10.1.
9.1. Normative References . . . . . . . . . . . . . . . . . . 8
10.2.
9.2. Informative References . . . . . . . . . . . . . . . . . 9
Appendix A. Alternatives . . . . . . . . . . . . . . . . . . . . 9 10
A.1. P-Charging-Vector . . . . . . . . . . . . . . . . . . . . 9 10
A.2. P-DCS-Billing-Info . . . . . . . . . . . . . . . . . . . 10
A.3. P-Asserted-Identity . . . . . . . . . . . . . . . . . . . 10
Appendix B. Changes 11
Acknowledgements . . . . . . . . . . . . . . . . . . . . . . . . 11
Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . 15 11

1. Overview

In certain network configurations, several network entities have
found it useful to decouple the identity of the caller (what is
normally thought of as "Caller ID") from the identity/number used for
billing purposes. This document records the current usage of P-
Charge-Info,
P-Charge-Info, a private SIP header field, to provide simple billing
information and requests details the registration of this header field with
IANA as required by Section 4 of [RFC5727].

In a typical configuration, the identity of the caller, commonly
referred to as "Caller ID" by end users, is derived from one of the
following SIP header fields:

o P-Asserted-Identity

o From (in the absence of P-Asserted-Identity)

(NOTE: Some service providers have also used the Remote-Party-ID
header field field, but this was never standardized and was replaced by P-
Asserted-Identity
P-Asserted-Identity in [RFC3325].)

This identity/number is typically presented to the receiving user
agent (UA) (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 some network configurations configurations, the "Caller ID" presented to
the receiving UA may be different from the number to be used for
billing purposes.

In this case, 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.

Several carriers, application providers, and equipment providers have
been using the P-Charge-Info header field since at least 2007 as a
simple mechanism to exchange this billing identifier.

This document specifies the use of the P-Charge-Info header field in
INVITE requests. The header field might be useful in other SIP
messages, but such use is beyond the scope of this document.

2. Requirements Language

The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT",
"SHOULD", "SHOULD NOT", "RECOMMENDED", "NOT RECOMMENDED", "MAY", and
"OPTIONAL" in this document are to be interpreted as described in BCP
14 [RFC2119] [RFC8174] when, and only when, they appear in all
capitals, as shown here.

The key words describe requirements needed to interoperate with
existing usage.

3. Purpose of this This Document

This document has been prepared to document the existing deployed
usage of the P-Charge-Info header field and to comply with Section 4
of [RFC5727] to register in registering this header field with IANA. It is noted
that RFC 5727 specifically deprecates new usage of "P-" header
fields, but P-Charge-Info has been in deployment since prior to before 2007
and pre-dates predates RFC 5727. Given this, the authors request believe that P-
Charge-Info be admitted as
P-Charge-Info is a "grandfathered case" per Section 4 of RFC 5727.

4. Use Cases

The simplest use case for P-Charge-Info is an enterprise environment
where each SIP endpoint has a direct number that is passed by the
enterprise SIP proxy across to a SIP proxy at a SIP service provider
who provides connectivity to the Public Switched Telephone Network
(PSTN). Rather than cause the SIP service provider to have to track
each individual direct number for billing purposes, the enterprise
SIP proxy sends sends, in the P-Charge-Info header field field, a single billing
identifier that the SIP service provider uses for billing purposes.

As another example, a hosted telephony provider or hosted voice voice-
application provider may have a large SIP network with customers who
are distributed over a very large geographic area using local and use local-
market PSTN
numbers but with numbers, although the network has only a very few actual
PSTN interconnection points.

The customers may all have local phone numbers numbers, yet outgoing calls
are actually routed across a SIP network and out specific PSTN
gateways or across specific SIP connections to other SIP service
providers. The hosted provider may want to pass a billing identifier
to its SIP service providers either for the purpose of simplicity in
billing or to obtain better rates from the SIP service providers.

5. The P-Charge-Info Header

5.1. Applicability Statement for the P-Charge-Info header field Header Field

The P-Charge-Info header field is applicable within a single private
administrative domain or between different administrative domains
where there is a trust relationship between the domains.

5.2. Usage of the P-Charge-Info header field Header Field

The P-Charge-Info header field is used to convey information about
the identity of the party to be charged. The P-Charge-Info header
field is typically inserted into a SIP request, usually an INVITE, by
one of the following:

o the SIP proxy on the originating network;

o a PSTN gateway acting as a SIP UA; or

o an application server generating billing information.

P-Charge-Info is to be used by the SIP entity that provides billing
services for a session. This could be an entity that is generating
billing records or an another entity interacting with another enitity generating
billing records. it. Upon receipt
of an INVITE request with the P-
Charge-Info P-Charge-Info header field, such an
entity MAY use the value present in P-Charge-Info as indicating the
party responsible for the charges associated with the session. This
decision, for example , example, could be based on local policy.

5.2.1. Procedures at the UA

The P-Charge-Info header field may be inserted by PSTN gateways or
application servers acting as a SIP UA.

The P-Charge-Info header field is ignored by an end-user UA and
should not normally be received by such a UA. It MUST NOT be sent to
such a UA
an end-user UA, as this would provide information to the UA about the
party to be charged
to the UA, which charged; providing such information may cause security security-
related issues, e.g. calling
party issues; for example, calling-party information would be known
by the UA for an otherwise anonymous call. A UA SHOULD ignore it if
it receives this header. Similarly, an end-user UA originating a SIP
message SHOULD NOT insert this header field.

A PSTN gateway or application server acting as a UA MAY use the
content of the P-Charge-Info header field present in an INVITE
request it received as the identity to be charged for billing related the session for
billing-related procedures, e.g. e.g., in a billing record or during
interaction with another entity generating billing
records, as the identity of the party to be charged for the session. records. A PSTN
gateway or application server acting as a UA MAY use the content of
the P-Charge-Info header field to populate information about the
identity of the party to charge in another type of signaling, e.g. ISUP. such as
ISDN User Part (ISUP).

5.2.2. Procedures at the Proxy

A SIP proxy that supports this extension and receives a request,
typically a SIP INVITE, MAY insert a P-Charge-Info header field. The
contents of the inserted header field may be decided based on local
policy or by querying an external entity to determine the identity of
the party to be charged.

When a proxy receives an INVITE request, it MAY use the content of
the P-Charge-Info header field present contained in an INVITE the request it received for billing billing-
related procedures, e.g. e.g., in a billing record or during interaction
with another entity that is generating billing records.

A SIP proxy that does not support this extension will pass any
received P-Charge-Info header field unmodified unmodified, in compliance with
RFC 3261.

A proxy supporting this extension MUST remove the P-Charge-Info
header field before sending a request to a UA that is not acting as a
PSTN gateway or appropriate application server, if the role of the UA
is known.

5.3. Use-Case Example of Usage

The content of the P-Charge-Info header field is typically just a
SIP/tel URI used as a billing indicator. An example could be as
simple as one of:

P-Charge-Info: <sip:+14075550134@example.net;user=phone>

P-Charge-Info: <sip:+12345550167@example.com>

P-Charge-Info: <sips:1234@example.com>

P-Charge-Info: <tel:+14075551234>

Any other applicable SIP URI could be used.

6. Formal Syntax

This RFC contains the definition of one or more SIP header fields
that allow choosing between addr-spec and name-addr when constructing
header field
header-field values. [RFC8217] prohibits the use of addr-spec if its
value would contain a comma, semicolon, or question mark.

The Private Header Field private header field specified in this document here is described in both prose
and an augmented Backus-Naur Form (BNF) defined in [RFC5234].
Further, several BNF definitions are inherited from SIP and are not
repeated here. Implementors need to be familiar with the notation
and contents of [RFC3261] and [RFC5234] to understand this document.

The syntax of the P-Charge-Info header field is described as follows:

P-Charge-Info = "P-Charge-Info" HCOLON (name-addr / addr-spec)
; name-addr and addr-spec are specified in RFC 3261

The SIP URI contained in the name-addr/addr-spec is the billing
indicator that is passed between the parties.

7. IANA Considerations

This specification registers a new proprietary SIP header field
according to the procedures defined in [RFC5727].

7.1. Header Field

The P-Charge-Info private header field described in Section 7 is has been registered in the
"Header Fields" sub-registry subregistry of the "Session Initiation Protocol (SIP)
Parameters" registry by adding a row with these values: as follows:

Header Field Name: P-Charge-Info

Compact Form: none

Reference: [TBD: This document] RFC 8496

8. Security Considerations

8.1. Trust Relationship

Given that the information contained in the P-Charge-Info header
field will be used for billing purposes, the proxies and other SIP
entities 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 network, a
mechanism for securing the confidentiality and integrity of the SIP
connection MUST be used to protect the information. One such
mechanism could be TLS-encryption TLS encryption of the SIP signaling stream.

8.2. Untrusted Peers

8.2.1. Ingress from Untrusted Peers

If the P-Charge-Info header field was accepted by a SIP entity from
an untrusted peer, there is the potential for fraud if the untrusted
entity sent incorrect information, either inadvertently or
maliciously.

Therefore

Therefore, a SIP entity MUST remove and ignore the P-Charge-Info
header field when it is received from an untrusted entity.

8.2.2. Egress to Untrusted Peers

If the P-Charge-Info header field was sent by a SIP entity to an
untrusted peer, there is the potential for exposure of network
information that is internal to a trust domain. For instance, the
untrusted entity may learn the identities of public SIP proxies used
within the trust domain domain, which could then potentially be directly
attacked.

If an implementation does not strip P-Charge-Info from the message
where specified in this document, it introduces serious privacy
risks. Examples include revealing third-party billing relationships
that might be sensitive, as well as unmasking the identity of callers
who wish to remain anonymous. Depending on circumstances, the latter
case may result in unwanted harassment and even physical harm to the
calling party.

Therefore

Therefore, a SIP entity MUST remove the P-Charge-Info header field
when it is sent to an untrusted entity.

9. Acknowledgements

The authors thank the following people for their comments: Keith
Drage, Miguel Garcia, Sumit Garg, John Haluska, Juha Heinanen,
Christer Holmberg, Paul Kyzivat, Adam Roach, Jonathan Rosenberg,
Henning Schulzrinne, Tom Taylor and Glen Wang.

10. References

10.1.

9.1. Normative References

[RFC2119] Bradner, S., "Key words for use in RFCs to Indicate
Requirement Levels", BCP 14, RFC 2119,
DOI 10.17487/
RFC2119, 10.17487/RFC2119, March 1997,
<http://www.rfc-editor.org/info/rfc2119>.
<https://www.rfc-editor.org/info/rfc2119>.

[RFC3261] Rosenberg, J., Schulzrinne, H., Camarillo, G., Johnston,
A., Peterson, J., Sparks, R., Handley, M., and E.
Schooler, "SIP: Session Initiation Protocol", RFC 3261,
DOI 10.17487/RFC3261, June 2002. 2002,
<https://www.rfc-editor.org/info/rfc3261>.

[RFC5727] Peterson, J., Jennings, C., and R. Sparks, "Change Process
for the Session Initiation Protocol (SIP) and the Real-
time Applications and Infrastructure Area", BCP 67,
RFC 5727, DOI 10.17487/RFC5727, March 2010. 2010,
<https://www.rfc-editor.org/info/rfc5727>.

[RFC8174] Leiba, B., "Ambiguity of Uppercase vs Lowercase in RFC
2119 Key Words", BCP 14, RFC 8174, DOI 10.17487/RFC8174,
May 2017, <https://www.rfc-editor.org/info/rfc8174>.

[RFC8217] Sparks, R., "Clarifications for When to Use the name-addr
Production in SIP Messages", RFC 8217,
DOI 10.17487/
RFC8217, 10.17487/RFC8217, August 2017, <https://www.rfc-editor.org/info/
rfc8217>.

10.2.
<https://www.rfc-editor.org/info/rfc8217>.

9.2. Informative References

[RFC5234] Crocker, D., Ed. and P. Overell, "Augmented BNF for Syntax
Specifications: ABNF", STD 68, RFC 5234,
DOI 10.17487/
RFC5234, 10.17487/RFC5234, January 2008, <https://www.rfc-editor.org/info/
rfc5234>.
<https://www.rfc-editor.org/info/rfc5234>.

[RFC3325] Jennings, C., Peterson, J., and M. Watson, "Private
Extensions to the Session Initiation Protocol (SIP) for
Asserted Identity within Trusted Networks", RFC 3325,
DOI 10.17487/RFC3325, November 2002. 2002,
<https://www.rfc-editor.org/info/rfc3325>.

[RFC5503] Andreasen, F., McKibben, B., and B. Marshall, "Private
Session Initiation Protocol (SIP) Proxy-to-Proxy
Extensions for Supporting the PacketCable Distributed Call
Signaling Architecture", RFC 5503, DOI 10.17487/RFC5503,
March 2009, <https://www.rfc-editor.org/info/rfc5503>.

[RFC7315] Jesske, R., Drage, K., and C. Holmberg, "Private Header
(P-Header) Extensions to the Session Initiation Protocol
(SIP) for the 3GPP", RFC 7315, DOI 10.17487/RFC7315, July
2014, <https://www.rfc-editor.org/info/rfc7315>.

Appendix A. Alternatives

A.1. P-Charging-Vector

P-Charging-Vector is defined in Section 4.6 of [RFC7315] and used by
the 3GPP to carry information related to the charging of a session.
There are, however, some differences in the semantics associated with
P-Charging-Vector and P-Charge-Info. P-Charging-Vector is mainly
used to carry information for correlation of multiple charging
records generated for a single session. On the other hand, P-Charge-
Info
P-Charge-Info is used to convey information about the party to be
billed for a call. Furthermore, P-Charging-Vector has a mandatory
icid-value parameter that is a globally unique value to identify the
session for which the charging information is generated. Such a globally-unique
globally unique identifier is not necessary when carrying information
about the user to be billed when it is attached to the corresponding
session-related signaling.

A.2. P-DCS-Billing-Info

P-DCS-Billing-Info is defined in Section 7 of [RFC5503] and used for
passing billing information between trusted entities in the
PacketCable Distributed Call Signaling Architecture. For many
billing situations, particularly the very large-scale residential
telephone networks for which this header field is designed, P-DCS-
Billing-Info
P-DCS-Billing-Info is an excellent solution. However, this ability
to address a range of situations adds complexity. According to RFC
5503, the following information is mandatory to include in each use
of the P-DCS-Billing-Info header field:

o Billing-Correlation-ID, a globally unique identifier

o Financial-Entity-ID

o RKS-Group-ID (record keeping (record-keeping server)

and

The P-DCS-Billing-Info header field may also include a variety of
additional parameters.

While this may work well in many billing scenarios, there are other
billing scenarios that do not need this level of complexity. In
those simpler scenarios scenarios, all that is needed is simply a number to use for
billing. P-Charge-Info provides this simple solution for simple
billing scenarios.

Additionally, according to Section 7.3 of RFC 5503, it is mandatory
for a UA to create a Billing-Correlation-ID and insert this into the
P-DCS-Billing-Info header field (along with the other required
information) sent in the initial SIP INVITE. This again makes sense
for the residential telephone service residential-telephone-service environment for which this
header field is designed. In contrast, P-Charge-Info is designed to
be used among proxies and not to be used at all by normal user agents.
(P-Charge-Info may, though, be used by user agents associated with
PSTN gateways.)

A.3. P-Asserted-Identity

Early reviewers of this document asked why the P-Asserted-Identity
header field documented in [RFC3325] could not be used. As mentioned
in the use case use-case example above, P-Asserted-Identity is used to
indicate the identity of the calling party. However, in this
instance, the requirement is to provide an additional identity of the
SIP-to-PSTN interconnect point.

It would be typical to find both P-Asserted-Identity and P-Charge-
Info
P-Charge-Info used in a SIP exchange. P-Asserted-Identity would be
used to provide the caller identity which that would be displayed to the
end user as "Caller ID" ID", while P-Charge-Info would provide the
billing identifier used for the billing associated with the call.

Appendix B. Changes

NOTE TO RFC EDITOR - Please remove this "Changes" section prior to
publication. Thank you.

Revision -08 incorporates significant feedback from Ben Campbell
including:

o Moving section on alternatives to an Appendix;

o Clarifying some uses of normative language;

o Moving RFCs 3261 and 8217 to Normative references; and

o multiple small tweaks to the text.

Revision -07 incorporates significant feedback from Jean Mahoney
including:

o Updating references to obsolete RFCs;

o Updating IANA considerations section;

o Changing example phone numbers; and

o multiple editorial and proofreading updates.

Revision -06 fixes one nit and updates the Requirements Language to
comply with BCP 14 / RFC 8174.

Revision -05 fixed a few typos and had other editorial changes.

Revision -04 removes the PASSporT and RFC 8224/8225 references
(inserted in Revision -03), as it was decided to capture that usage
in a separate draft.

Revision -03 incorporates feedback from

Acknowledgements

The authors thank the expert review by following people for their comments: Keith
Drage, Miguel Garcia, Sumit Garg, John Haluska, Juha Heinanen,
Christer Holmberg, Paul Kyzivat, Adam Roach, including:

o changing all references to "header" to be "header field";

o the addition of references to RFCs 8224 and 8225 related to STIR;
o a reference to RFC 8217 in the formal syntax; and

o multiple editorial Jonathan Rosenberg,
Henning Schulzrinne, Tom Taylor, and proofreading updates.

Revision -02 incorporates a range of feedback provided by Henning
Schulzrinne.

Revision -01 is a refresh as -00 expired. The affiliation of Tolga
Asveren was changed to Ribbon Communications.

Revision -00 strips out the NPI and NOA parameters to focus only on
the usage in a pure SIP-to-SIP environment. Multiple editing changes
were made for readability.

NAME CHANGE - The document is now "draft-york-p-charge-info" to
reflect the fact that the publishing route for the draft is being
determined.

Revision -06 updates the text for 2017 and changes Dan York's
affiliation to "Individual".

Revision -05 is a refresh as -04 expired. Several small tweaks were
also made to narrative text.

Revision -04 is purely a refresh as -03 expired.

Revision -03 is purely a refresh as -02 expired.

Revision -02 is purely a refresh as -01 expired. My hope is to move
this document forward soon to put closure on it.

Revision -01 is purely a refresh as -00 expired. Only a few minor
tweaks to this "Changes" section of the document.

Revision -00 is the initial release of "draft-york-dispatch-p-charge-
info" and is identical to "draft-york-sipping-p-charge-info-15"
except for changes to wording to reflect the change to the DISPATCH
working group. The "organization" name for Dan York was also changed
from blank to "DisTel Research" to remove the confusion that it
looked like he was also employed by Sonus Networks.

NAME CHANGE - The document is now "draft-york-dispatch-p-charge-info"
to reflect the fact that the SIPPING Working Group no longer exists.

Revision -15 simply fixes a wording error in the abstract in the
previous revision. This will also be the last version of 'draft-
york-sipping-p-charge-info'. The next version will be 'draft-york-
dispatch-p-charge-info'.

Revision -14 incorporates the following changes:

o Two examples were updated to include a "+1" at the beginning of
the SIP URI.

o An example was changed to use "example.net" to be compliant with
RFC 2606.

o Dan York's organization was updated to "Individual" (from empty)
to indicate that his involvement with this draft is purely as an
individual with no connection to his employer.

o The length of time the header has been used in the Introduction
was changed to 7 years, to reflect the first usage around 2005.

o A note was added to the abstract indicating that this is expected
to be the last version using the name 'draft-york-sipping-p-
charge-info'.

o Informative references were added to RFC 3261 and RFC 2234 to
address missing references in the text.

o Numerous other tweaks to the text for readability.

Revision -13 has no changes to content and was issued as -12 expired.
Discussions are under way coming out of IETF 83 on a plan to move
this draft forward. As the SIPPING working group no longer exists,
the draft name needs to change and there are a couple of other
required changes.

Revision -12 included the following modifications based on feedback
from John Haluska and Glen Wang:

o Modification of Appendix B to reflect ANSI T1.113 values.

Revision -11 represents a fairly significant revision responding to a
solid review by Paul Kyzivat and providing additional explanation. A
major shift was the move to using decimal values for the npi-value
parameter versus the text values of previous drafts. Changes
include:

o ABNF definition updated to indicate that npi is now a number vs
text.

o The "npi" and "noa" acronyms were expanded and stated near the
formal syntax definition.

o New section created explicitly mentioning the optional parameters.

o Example of optional parameters updated to have npi use a number vs
text.

o Appendix B added to give examples of NOA parameter.

o Overview text updated to indicate that P-Charge-Info was been in
use now for over 5 years (given that the draft has been in
development for 3 years).

o Several small fixes for readability.

Revision -10 included the following modifications:

o Formal ABNF definition updated.

o In formal syntax, semicolons added to npi-param and noa-param
definitions.

o npi-param changed to a 'gen-value' to use digits vs text. Values
npi-param are shown in Appendix A.

o Corrected example to show proper use of parameters.

o Updated references to RFC 3427 and RFC 3968 to reference RFC 5727.

Revision -09 included the following modifications:

o Re-submitted with only a date change. Discussions are ongoing to
finalize this draft and submit it for expert review.

Revision -08 included the following modifications:

o The ABNF for the "npi-value" was modified to conform to the
sequence of possible values stated in ANSI T1.113.

o An Appendix A was created listing the values from ANSI T1.113.

Revision -07 was updated to the "trust200902" IPR statement and added
references to RFC 3968. At this point all comments have been
incorporated and publication will be requested.

Revision -06 had only a minor correction to the second usage example.
The IPR statement was also updated to comply with RFC 5378.

Revision -05 included the following modifications:

o The usage of P-Charge-Info for carrying the ISUP Charge Number
parameter was formally incorporated into the draft. Previous
revisions had mentioned it as a possible use case but had not
really explicitly included it.

o The examples/use cases section was expanded to include further
examples of where P-Charge-Info may be used.

o The original use case which discussed inter/intra-state billing
practices was changed as the geographical references were clouding
the more fundamental issue.

o The "UNKNOWN" value was added to the ABNF for the "npi-value"
parameter as that was identified as missing but required for ISUP
interworking.

o The optional "Nature of Address" parameter was added to support
interworking with the ISUP Charge Number.

Revision -04 corrected a major error in the example where the
parameter was placed inside the angle brackets. The P-DCS-Billing-
Info header was also added as an alternative and a few minor edits
were made. Glen Wang.

Authors' Addresses

Dan York
Individual
Keene, NH
USA
United States of America

Email: dyork@lodestar2.com

Tolga Asveren
Ribbon Communications
3 Paragon Way, Suite 100
Freehold, NJ
USA 007728
United States of America

Email: tasveren@rbbn.com