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Versions: (draft-saintandre-sip-xmpp-im) 00 01 02 03 04 05 06 07 08 09 10 11 12 13 RFC 7572

Network Working Group                                     P. Saint-Andre
Internet-Draft                                                      &yet
Intended status: Standards Track                                A. Houri
Expires: September 6, 2015                                           IBM
                                                           J. Hildebrand
                                                     Cisco Systems, Inc.
                                                           March 5, 2015


   Interworking between the Session Initiation Protocol (SIP) and the
  Extensible Messaging and Presence Protocol (XMPP): Instant Messaging
                         draft-ietf-stox-im-13

Abstract

   This document defines a bidirectional protocol mapping for the
   exchange of single instant messages between the Session Initiation
   Protocol (SIP) and the Extensible Messaging and Presence Protocol
   (XMPP).

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-
   Drafts is at http://datatracker.ietf.org/drafts/current/.

   Internet-Drafts are draft documents valid for a maximum of six months
   and may be updated, replaced, or obsoleted by other documents at any
   time.  It is inappropriate to use Internet-Drafts as reference
   material or to cite them other than as "work in progress."

   This Internet-Draft will expire on September 6, 2015.

Copyright Notice

   Copyright (c) 2015 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
   to this document.  Code Components extracted from this document must



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   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.  Introduction  . . . . . . . . . . . . . . . . . . . . . . . .   2
   2.  Intended Audience . . . . . . . . . . . . . . . . . . . . . .   3
   3.  Terminology . . . . . . . . . . . . . . . . . . . . . . . . .   3
   4.  XMPP to SIP . . . . . . . . . . . . . . . . . . . . . . . . .   4
   5.  SIP to XMPP . . . . . . . . . . . . . . . . . . . . . . . . .   6
   6.  Message Size  . . . . . . . . . . . . . . . . . . . . . . . .   8
   7.  Content Types . . . . . . . . . . . . . . . . . . . . . . . .   9
   8.  Internationalization Considerations . . . . . . . . . . . . .   9
   9.  IANA Considerations . . . . . . . . . . . . . . . . . . . . .  10
   10. Security Considerations . . . . . . . . . . . . . . . . . . .  10
   11. References  . . . . . . . . . . . . . . . . . . . . . . . . .  10
   Appendix A.  Acknowledgements . . . . . . . . . . . . . . . . . .  12
   Authors' Addresses  . . . . . . . . . . . . . . . . . . . . . . .  13

1.  Introduction

   In order to help ensure interworking between instant messaging (IM)
   systems that conform to the instant messaging / presence requirements
   [RFC2779], it is important to clearly define protocol mappings
   between such systems.  Within the IETF, work has proceeded on two
   instant messaging technologies:

   o  Various extensions to the Session Initiation Protocol ([RFC3261])
      for instant messaging, in particular the MESSAGE method extension
      [RFC3428].

   o  The Extensible Messaging and Presence Protocol (XMPP), which
      consists of a formalization of the core XML streaming protocols
      developed originally by the Jabber open-source community; the
      relevant specifications are [RFC6120] for the XML streaming layer
      and [RFC6121] for basic presence and instant messaging extensions.

   One approach to helping ensure interworking between these protocols
   is to map each protocol to the abstract semantics described in
   [RFC3860]; that is the approach taken by
   [I-D.ietf-simple-cpim-mapping] and [RFC3922].  By contrast, the
   approach taken in this document is to directly map semantics from one
   protocol to another (i.e., from SIP/SIMPLE to XMPP and vice-versa),
   since that is how existing systems solve the interworking problem.

   Both XMPP and IM-capable SIP systems enable entities to exchange
   "instant messages".  The term "instant message" usually refers to a



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   message sent between two entities for delivery in close to real time
   (rather than a message that is stored and forwarded to the intended
   recipient upon request).  This document covers single messages only
   (sometimes called "page-mode" messaging), since they form the lowest
   common denominator for IM.  Separate documents cover "session-mode"
   instant messaging in the form of one-to-one chat sessions
   [I-D.ietf-stox-chat], as well as multi-party chat sessions
   [I-D.ietf-stox-groupchat].  In particular, session-mode instant
   messaging supports several features that are not part of page-mode
   instant messaging, such as a higher level of assurance regarding end-
   to-end message delivery.

   The architectural assumptions underlying such direct mappings are
   provided in [RFC7247], including mapping of addresses and error
   conditions.  The mappings specified in this document cover basic
   instant messaging functionality, i.e., the exchange of a single
   instant message between a SIP user and an XMPP user in either
   direction.  Mapping of more advanced functionality is out of scope
   for this document, but other documents in this "series" cover such
   topics.

2.  Intended Audience

   The documents in this series are intended for use by software
   developers who have an existing system based on one of these
   technologies (e.g., SIP), and would like to enable communication from
   that existing system to systems based on the other technology (e.g.,
   XMPP).  We assume that readers are familiar with the core
   specifications for both SIP [RFC3261] and XMPP [RFC6120], with the
   base document for this series [RFC7247], and with the following IM-
   related specifications:

   o  Session Initiation Protocol (SIP) Extension for Instant Messaging
      [RFC3428]

   o  Extensible Messaging and Presence Protocol: Instant Messaging and
      Presence [RFC6121]

   Note well that not all protocol-compliant messages are shown (such as
   SIP 100 TRYING messages), in order to focus the reader on the
   essential aspects of the protocol flows.

3.  Terminology

   A number of terms used here are explained in [RFC3261], [RFC3428],
   [RFC6120], and [RFC6121].





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   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
   [RFC2119].

4.  XMPP to SIP

   As described in [RFC6121], a single instant message is an XML
   <message/> stanza of type "normal" sent over an XML stream (since
   "normal" is the default for the 'type' attribute of the <message/>
   stanza, the attribute is often omitted).

   When the XMPP user Juliet <juliet@example.com> wants to send an
   instant message to Romeo, she interacts with her XMPP client, which
   generates an XMPP <message/> stanza.  The syntax of the <message/>
   stanza, including required and optional elements and attributes, is
   defined in [RFC6121] (for single instant messages, Section 5.1 of
   [RFC6121] recommends that the value of the 'to' address be a "bare
   JID" of the form "localpart@domainpart").  The following is an
   example of such a stanza:

   Example 1: XMPP user sends message

   |  <message from='juliet@example.com/yn0cl4bnw0yr3vym'
   |           to='romeo@example.net'>
   |    <body>Art thou not Romeo, and a Montague?</body>
   |  </message>

   Upon receiving such a message stanza, the XMPP server needs to
   determine the identity of the domainpart in the 'to' address, which
   it does by following the procedures explained in Section 5 of
   [RFC7247].  If the domain is a SIP domain, the XMPP server will hand
   off the message stanza to an XMPP-to-SIP gateway that natively
   communicates with IM-aware SIP servers.

   The XMPP-to-SIP gateway is then responsible for translating the XMPP
   message stanza into a SIP MESSAGE request from the XMPP user to the
   SIP user:













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   Example 2: XMPP user sends message (SIP transformation)

   |  MESSAGE sip:romeo@example.net SIP/2.0
   |  Via: SIP/2.0/TCP x2s.example.com;branch=z9hG4bK776sgdkse
   |  Max-Forwards: 70
   |  To: sip:romeo@example.net
   |  From: <sip:juliet@example.com;gr=yn0cl4bnw0yr3vym>;tag=12345
   |  Call-ID: D9AA95FD-2BD5-46E2-AF0F-6CFAA96BDDFA
   |  CSeq: 1 MESSAGE
   |  Content-Type: text/plain
   |  Content-Length: 35
   |
   |  Art thou not Romeo, and a Montague?

   The destination SIP server is responsible for delivering the message
   to the intended recipient, and the recipient is responsible for
   generating a response (e.g., 200 OK).

   Example 3: SIP user agent indicates receipt of message

   |  SIP/2.0 200 OK
   |  Via: SIP/2.0/TCP x2s.example.com;branch=z9hG4bK776sgdkse
   |  From: sip:juliet@example.com;tag=12345
   |  To: sip:romeo@example.net;tag=vwxyz
   |  Call-ID: D9AA95FD-2BD5-46E2-AF0F-6CFAA96BDDFA
   |  CSeq: 1 MESSAGE
   |  Content-Length: 0

   As described in [RFC3428], a downstream proxy could fork a MESSAGE
   request, but it would return only one 200 OK to the gateway.

      Note: This document does not specify handling of the 200 OK by the
      XMPP-to-SIP gateway (e.g., to enable message acknowledgements).
      See [I-D.ietf-stox-chat] for a mapping of message acknowledgements
      in the context of one-to-one chat sessions.

   The mapping of XMPP syntax to SIP syntax MUST be as shown in the
   following table.













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   Table 1: Message syntax mapping from XMPP to SIP

      +-----------------------------+--------------------------+
      |  XMPP Element or Attribute  |  SIP Header or Contents  |
      +-----------------------------+--------------------------+
      |  <body/>                    |  body of MESSAGE         |
      |  <subject/>                 |  Subject                 |
      |  <thread/>                  |  Call-ID                 |
      |  from                       |  From (1)                |
      |  id                         |  transaction identifer   |
      |  to                         |  To or Request-URI       |
      |  type                       |  (no mapping) (2)        |
      |  xml:lang                   |  Content-Language        |
      +-----------------------------+--------------------------+

   1.  As shown in the foregoing example and described in [RFC7247], the
       XMPP-to-SIP gateway MUST map the bare JID
       ("localpart@domainpart") of the XMPP sender to the SIP From
       header and include the resourcepart of the full JID as the GRUU
       portion [RFC5627] of the SIP URI.

   2.  Because there is no SIP header field that matches the meaning of
       the XMPP message 'type' values ("normal", "chat", "groupchat",
       "headline", "error"), no general mapping is possible here.

5.  SIP to XMPP

   As described in [RFC3428], a single instant message is a SIP MESSAGE
   request sent from a SIP user agent to an intended recipient who is
   most generally referenced by an Instant Message URI of the form
   <im:user@domain> but who might be referenced by a SIP or SIPS URI of
   the form <sip:user@domain> or <sips:user@domain>.

   When the SIP user Romeo <sip:romeo@example.net> wants to send an
   instant message to Juliet, he interacts with his SIP user agent,
   which generates a SIP MESSAGE request.  The syntax of the MESSAGE
   request is defined in [RFC3428].  The following is an example of such
   a request:













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   Example 4: SIP user sends message

   |  MESSAGE sip:juliet@example.com SIP/2.0
   |  Via: SIP/2.0/TCP s2x.example.net;branch=z9hG4bKeskdgs677
   |  Max-Forwards: 70
   |  To: sip:juliet@example.com
   |  From: sip:romeo@example.net;tag=vwxyz
   |  Call-ID: 9E97FB43-85F4-4A00-8751-1124FD4C7B2E
   |  CSeq: 1 MESSAGE
   |  Content-Type: text/plain
   |  Content-Length: 44
   |
   |  Neither, fair saint, if either thee dislike.

   Section 5 of [RFC3428] stipulates that a SIP User Agent presented
   with an im: URI should resolve it to a sip: or sips: URI.  Therefore
   we assume that the Request-URI of a request received by an IM-capable
   SIP-to-XMPP gateway will contain a sip: or sips: URI.  Upon receiving
   the MESSAGE, the SIP server needs to determine the identity of the
   domain portion of the Request-URI or To header, which it does by
   following the procedures explained in Section 5 of [RFC7247].  If the
   domain is an XMPP domain, the SIP server will hand off the MESSAGE to
   an associated SIP-to-XMPP gateway that natively communicates with
   XMPP servers.

   The SIP-to-XMPP gateway is then responsible for translating the
   request into an XMPP message stanza from the SIP user to the XMPP
   user and returning a SIP "200 OK" message to the sender:

   Example 5: SIP user sends message (XMPP transformation)

   |  <message from='romeo@example.net/dr4hcr0st3lup4c'
   |           to='juliet@example.com'>
   |    <body>Neither, fair saint, if either thee dislike.</body>
   |  </message>

   Note that the stanza handling rules specified in [RFC6121] allow the
   receiving XMPP server to deliver a message stanza whose 'to' address
   is a bare JID ("localpart@domainpart") to multiple connected devices.
   This is similar to the "forking" of messages in SIP.

   The mapping of SIP syntax to XMPP syntax MUST be as shown in the
   following table.








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   Table 2: Message syntax mapping from SIP to XMPP

      +--------------------------+-----------------------------+
      |  SIP Header or Contents  |  XMPP Element or Attribute  |
      +--------------------------+-----------------------------+
      |  Call-ID                 |  <thread/>                  |
      |  Content-Language        |  xml:lang                   |
      |  CSeq                    |  (no mapping)               |
      |  From                    |  from (1)                   |
      |  Subject                 |  <subject/>                 |
      |  Request-URI or To       |  to                         |
      |  body of MESSAGE         |  <body/>                    |
      |  transaction identifier  |  id                         |
      +--------------------------+-----------------------------+

   1.  As shown in the foregoing example and described in [RFC7247], if
       the IM-capable SIP-to-XMPP gateway has information about the GRUU
       [RFC5627] of the particular endpoint that sent the SIP message
       then it MUST map the sender's address to a full JID
       ("localpart@domainpart/resourcepart") in the 'from' attribute of
       the XMPP stanza and include the GRUU as the resourcepart.

   When transforming SIP pager-mode messages, an IM-capable SIP-to-XMPP
   gateway MUST specify no XMPP 'type' attribute or, equivalently, a
   'type' attribute whose value is "normal" [RFC6121].

   See Section 7 of this document about the handling of SIP message
   bodies that contain content types other than plain text.

6.  Message Size

   [RFC3428] specifies that (outside of a media session) the size of a
   MESSAGE request is not allowed to exceed 1300 bytes.  Although in
   practice XMPP instant messages do not often exceed that size, neither
   [RFC6120] nor [RFC6121] sets an upper limit on the size of XMPP
   stanzas.  However, XMPP server deployments usually do limit the size
   of stanzas in order to help prevent denial of service attacks, and
   [RFC6120] states that if a server sets a maximum stanza size then the
   limit is not allowed to be less than 10,000 bytes.  Because of this
   mismatch, an XMPP-to-SIP gateway SHOULD return a <policy-violation/>
   stanza error if an XMPP user attempts to send an XMPP message stanza
   that would result in a SIP MESSAGE greater than 1300 bytes.  Although
   such a gateway might decide to "upgrade" from page mode to session
   mode using the Message Session Relay Protocol (MSRP) and thus
   treating the instant message as part of a chat session as described
   in [I-D.ietf-stox-chat], such behavior is application-specific and
   this document provides no guidelines for how to complete such an
   upgrade.



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7.  Content Types

   SIP requests of type MESSAGE are allowed to contain essentially any
   content type.  The recommended procedures for SIP-to-XMPP gateways to
   use in handling these content types are as follows.

   An IM-aware SIP-to-XMPP gateway MUST process SIP messages that
   contain message bodies of type "text/plain" and MUST encapsulate such
   message bodies as the XML character data of the XMPP <body/> element.

   An IM-aware SIP-to-XMPP gateway SHOULD process SIP messages that
   contain message bodies of type "text/html"; if so, a gateway MUST
   transform the "text/html" content into XHTML content that conforms to
   the XHTML-IM Integration Set specified in [XEP-0071].

   Although an IM-aware SIP-to-XMPP gateway MAY process SIP messages
   that contain message bodies of types other than "text/plain" and
   "text/html", the handling of such content types is a matter of
   implementation.

8.  Internationalization Considerations

   Both XMPP and SIP support the UTF-8 encoding [RFC3629] of Unicode
   characters [UNICODE] within messages, along with tagging of the
   language for a particular message (in XMPP via the 'xml:lang'
   attribute and in SIP via the Content-Language header).  Gateways MUST
   map these language tagging mechanisms if they are present in the
   original message.  Several examples follow, using the "XML Notation"
   [RFC3987] for Unicode characters outside the ASCII range.

   Example 6: SIP user sends message

   |  MESSAGE sip:juliet@example.com SIP/2.0
   |  Via: SIP/2.0/TCP s2x.example.net;branch=z9hG4bKeskdgs677
   |  Max-Forwards: 70
   |  To: sip:juliet@example.com
   |  From: sip:romeo@example.net;tag=vwxyz
   |  Call-ID: 5A37A65D-304B-470A-B718-3F3E6770ACAF
   |  CSeq: 1 MESSAGE
   |  Content-Type: text/plain
   |  Content-Length: 45
   |  Content-Language: cs
   |
   |  Nic z ob&#xC3A9;ho, m&#xC3A1; d&#xC49B;vo spanil&#xC3A1;,
   |  nenavid&#xC3AD;&#xC5A1;-li jedno nebo druh&#xC3A9;.






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   Example 7: SIP user sends message (XMPP transformation)

   |  <message from='romeo@example.net'
   |           to='juliet@example.com'
   |           xml:lang='cs'>
   |    <body>
   |  Nic z ob&#xC3A9;ho, m&#xC3A1; d&#xC49B;vo spanil&#xC3A1;,
   |  nenavid&#xC3AD;&#xC5A1;-li jedno nebo druh&#xC3A9;.
   |    </body>
   |  </message>

9.  IANA Considerations

   This document requests no actions of IANA.

10.  Security Considerations

   Detailed security considerations for instant messaging protocols are
   given in [RFC2779], for SIP-based instant messaging in [RFC3428] (see
   also [RFC3261]), and for XMPP-based instant messaging in [RFC6121]
   (see also [RFC6120]).  The security considerations provided in
   [RFC7247] also apply.

   This document specifies methods for exchanging "page-mode" instant
   messages through a gateway that translates between SIP and XMPP, and
   [I-D.ietf-stox-chat] specifies such methods for "session-mode"
   instant messaging between MSRP and XMPP.  Such a gateway MUST be
   compliant with the minimum security requirements of the textual chat
   protocols for which it translates (i.e., SIP or MSRP and XMPP).

   The addition of gateways to the security model of instant messaging
   specified in [RFC2779] introduces some new risks.  In particular,
   end-to-end security properties (especially confidentiality and
   integrity) between instant messaging clients that interface through a
   gateway can be provided only if common formats are supported.
   Specification of those common formats is out of scope for this
   document.  For instant messages, it is possible to use [RFC3862] and
   [RFC3923], but those methods are not widely implemented.  A more
   widely implemented albeit unstandardized method for interoperable
   end-to-end encryption would be Off-the-Record Messaging [OTR].

11.  References

11.1.  Normative References

   [RFC2119]  Bradner, S., "Key words for use in RFCs to Indicate
              Requirement Levels", BCP 14, RFC 2119, March 1997.




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   [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.

   [RFC3428]  Campbell, B., Rosenberg, J., Schulzrinne, H., Huitema, C.,
              and D. Gurle, "Session Initiation Protocol (SIP) Extension
              for Instant Messaging", RFC 3428, December 2002.

   [RFC5627]  Rosenberg, J., "Obtaining and Using Globally Routable User
              Agent URIs (GRUUs) in the Session Initiation Protocol
              (SIP)", RFC 5627, October 2009.

   [RFC6120]  Saint-Andre, P., "Extensible Messaging and Presence
              Protocol (XMPP): Core", RFC 6120, March 2011.

   [RFC6121]  Saint-Andre, P., "Extensible Messaging and Presence
              Protocol (XMPP): Instant Messaging and Presence", RFC
              6121, March 2011.

   [RFC7247]  Saint-Andre, P., Houri, A., and J. Hildebrand,
              "Interworking between the Session Initiation Protocol
              (SIP) and the Extensible Messaging and Presence Protocol
              (XMPP): Architecture, Addresses, and Error Handling", RFC
              7247, May 2014.

   [XEP-0071]
              Saint-Andre, P., "XHTML-IM", XSF XEP 0071, November 2012.

11.2.  Informative References

   [I-D.ietf-simple-cpim-mapping]
              Rosenberg, J. and B. Campbell, "CPIM Mapping of SIMPLE
              Presence and Instant Messaging", draft-ietf-simple-cpim-
              mapping-01 (work in progress), June 2002.

   [I-D.ietf-stox-chat]
              Saint-Andre, P. and S. Loreto, "Interworking between the
              Session Initiation Protocol (SIP) and the Extensible
              Messaging and Presence Protocol (XMPP): One-to-One Text
              Chat Sessions", draft-ietf-stox-chat-11 (work in
              progress), March 2015.









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   [I-D.ietf-stox-groupchat]
              Saint-Andre, P., Corretge, S., and S. Loreto,
              "Interworking between the Session Initiation Protocol
              (SIP) and the Extensible Messaging and Presence Protocol
              (XMPP): Groupchat", draft-ietf-stox-groupchat-11 (work in
              progress), March 2015.

   [OTR]      Ian Goldberg, , "Off-the-Record Messaging", <https://
              otr.cypherpunks.ca/>.

   [RFC2779]  Day, M., Aggarwal, S., and J. Vincent, "Instant Messaging
              / Presence Protocol Requirements", RFC 2779, February
              2000.

   [RFC3629]  Yergeau, F., "UTF-8, a transformation format of ISO
              10646", STD 63, RFC 3629, November 2003.

   [RFC3860]  Peterson, J., "Common Profile for Instant Messaging
              (CPIM)", RFC 3860, August 2004.

   [RFC3862]  Klyne, G. and D. Atkins, "Common Presence and Instant
              Messaging (CPIM): Message Format", RFC 3862, August 2004.

   [RFC3922]  Saint-Andre, P., "Mapping the Extensible Messaging and
              Presence Protocol (XMPP) to Common Presence and Instant
              Messaging (CPIM)", RFC 3922, October 2004.

   [RFC3923]  Saint-Andre, P., "End-to-End Signing and Object Encryption
              for the Extensible Messaging and Presence Protocol
              (XMPP)", RFC 3923, October 2004.

   [RFC3987]  Duerst, M. and M. Suignard, "Internationalized Resource
              Identifiers (IRIs)", RFC 3987, January 2005.

   [UNICODE]  The Unicode Consortium, "The Unicode Standard, Version
              7.0.0", 2014,
              <http://www.unicode.org/versions/Unicode7.0.0/>.

Appendix A.  Acknowledgements

   The authors wish to thank the following individuals for their
   feedback: Mary Barnes, Dave Cridland, Dave Crocker, Adrian Georgescu,
   Christer Holmberg, Saul Ibarra Corretge, Olle Johansson, Paul
   Kyzivat, Salvatore Loreto, Daniel-Constantin Mierla, and Tory Patnoe.

   Special thanks to Ben Campbell for his detailed and insightful
   reviews.




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   Francis Dupont reviewed the document on behalf of the General Area
   Review Team.

   Spencer Dawkins, Stephen Farrell, and Barry Leiba provided helpful
   input during IESG review.

   The authors gratefully acknowledge the assistance of Markus Isomaki
   and Yana Stamcheva as the working group chairs and Gonzalo Camarillo
   and Alissa Cooper as the sponsoring Area Directors.

   Peter Saint-Andre wishes to acknowledge Cisco Systems, Inc., for
   employing him during his work on earlier versions of this document.

Authors' Addresses

   Peter Saint-Andre
   &yet

   Email: peter@andyet.com
   URI:   https://andyet.com/


   Avshalom Houri
   IBM
   Rorberg Building, Pekris 3
   Rehovot  76123
   Israel

   Email: avshalom@il.ibm.com


   Joe Hildebrand
   Cisco Systems, Inc.
   1899 Wynkoop Street, Suite 600
   Denver, CO  80202
   USA

   Email: jhildebr@cisco.com













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