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Versions: (draft-york-dispatch-p-charge-info) 00 01 02 03 04 05 06 07 08 RFC 8496

Internet Engineering Task Force                                  D. York
Internet-Draft                                                Individual
Intended status: Informational                                T. Asveren
Expires: January 1, 2019                           Ribbon Communications
                                                           June 30, 2018


   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) 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 since at least 2007.  This
   document is submitted to request the registration of this header
   field with the Internet Assigned Numbers Authority (IANA).

Status of This Memo

   This Internet-Draft is submitted in full conformance with the
   provisions of BCP 78 and BCP 79.

   Internet-Drafts are working documents of the Internet Engineering
   Task Force (IETF).  Note that other groups may also distribute
   working documents as Internet-Drafts.  The list of current Internet-
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   Internet-Drafts are draft documents valid for a maximum of six months
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   This Internet-Draft will expire on January 1, 2019.

Copyright Notice

   Copyright (c) 2018 IETF Trust and the persons identified as the
   document authors.  All rights reserved.

   This document is subject to BCP 78 and the IETF Trust's Legal
   Provisions Relating to IETF Documents
   (http://trustee.ietf.org/license-info) in effect on the date of
   publication of this document.  Please review these documents
   carefully, as they describe your rights and restrictions with respect



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   to this document.  Code Components extracted from this document must
   include Simplified BSD License text as described in Section 4.e of
   the Trust Legal Provisions and are provided without warranty as
   described in the Simplified BSD License.

Table of Contents

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

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, a private SIP header field, to provide simple billing
   information and requests the registration of this header field with
   IANA as required by Section 4 of [RFC5727].





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   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 but this was never standardized and was replaced by P-
   Asserted-Identity in [RFC3325].)

   This identity/number is typically presented to the receiving user
   agent (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 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.








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3.  Purpose of 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 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 2007
   and pre-dates RFC 5727.  Given this, the authors request that P-
   Charge-Info be admitted as 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 in the P-Charge-Info header field a single billing
   identifier that the SIP service provider uses for billing purposes.

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

   The customers may all have local phone 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

   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

   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:



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   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 generating billing
   records or an entity interacting with another enitity generating
   billing records.  Upon receipt of an INVITE request with the 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 , 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 as this would provide information about party to be charged
   to the UA, which may cause security related issues, e.g. 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 for billing related procedures, 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.
   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.

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.





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

   A SIP proxy that does not support this extension will pass any
   received P-Charge-Info header field 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.  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 values.  [RFC8217] prohibits the use of addr-spec if its
   value would contain a comma, semicolon, or question mark.

   The Private Header Field specified in this document 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



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   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 header field described in Section 7 is registered in the "Header
   Fields" sub-registry of the "Session Initiation Protocol (SIP)
   Parameters" registry by adding a row with these values:

   Header Field Name: P-Charge-Info

   Compact Form: none

   Reference: [TBD: This document]

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





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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 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 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 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.  Normative References

   [RFC2119]  Bradner, S., "Key words for use in RFCs to Indicate
              Requirement Levels", BCP 14, RFC 2119, DOI 10.17487/
              RFC2119, March 1997,
              <http://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,
              June 2002.

   [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, March 2010.






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   [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, August 2017, <https://www.rfc-editor.org/info/
              rfc8217>.

10.2.  Informative References

   [RFC5234]  Crocker, D., Ed. and P. Overell, "Augmented BNF for Syntax
              Specifications: ABNF", STD 68, RFC 5234, DOI 10.17487/
              RFC5234, January 2008, <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,
              November 2002.

   [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 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
   identifier is not necessary when carrying information about the user




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   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 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 server)

   and may 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 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 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 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.




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   It would be typical to find both P-Asserted-Identity and P-Charge-
   Info used in a SIP exchange.  P-Asserted-Identity would be used to
   provide the caller identity which would be displayed to the end user
   as "Caller 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 the expert review by 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;



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   o  a reference to RFC 8217 in the formal syntax; and

   o  multiple editorial 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'.



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   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.



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   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



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      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.

Authors' Addresses

   Dan York
   Individual
   Keene, NH
   USA

   Email: dyork@lodestar2.com


   Tolga Asveren
   Ribbon Communications
   NJ
   USA

   Email: tasveren@rbbn.com













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