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RFC 7220 - Description Option for the Port Control Protocol (PCP)

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Internet Engineering Task Force (IETF)                      M. Boucadair
Request for Comments: 7220                                France Telecom
Category: Standards Track                                       R. Penno
ISSN: 2070-1721                                                  D. Wing
                                                                May 2014

         Description Option for the Port Control Protocol (PCP)


   This document extends the Port Control Protocol (PCP) with the
   ability to associate a description with a PCP-instantiated mapping.
   It does this by defining a new DESCRIPTION option.

Status of This Memo

   This is an Internet Standards Track document.

   This document is a product of the Internet Engineering Task Force
   (IETF).  It represents the consensus of the IETF community.  It has
   received public review and has been approved for publication by the
   Internet Engineering Steering Group (IESG).  Further information on
   Internet Standards is available in Section 2 of RFC 5741.

   Information about the current status of this document, any errata,
   and how to provide feedback on it may be obtained at

Copyright Notice

   Copyright (c) 2014 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
   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.  Format  . . . . . . . . . . . . . . . . . . . . . . . . . . .   3
   3.  Behavior  . . . . . . . . . . . . . . . . . . . . . . . . . .   4
   4.  Security Considerations . . . . . . . . . . . . . . . . . . .   5
   5.  IANA Considerations . . . . . . . . . . . . . . . . . . . . .   5
   6.  References  . . . . . . . . . . . . . . . . . . . . . . . . .   5
     6.1.  Normative References  . . . . . . . . . . . . . . . . . .   5
     6.2.  Informative References  . . . . . . . . . . . . . . . . .   6

1.  Introduction

   This document extends the base PCP [RFC6887] with the ability to
   associate a human-readable description with a PCP-instantiated
   mapping.  It does this by defining a new DESCRIPTION option.

   This PCP option can be used in simple scenarios with a PCP client and
   PCP server, as well as in more complex scenarios where an
   interworking function is used to proxy between a UPnP IGD Control
   Point and a PCP server [RFC6970].

   Querying the PCP server to get the description text of an existing
   mapping is out of scope.

   The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT",
   document are to be interpreted as described in RFC 2119 [RFC2119].

2.  Format

   The format of the DESCRIPTION option is shown in Figure 1.

       0                   1                   2                   3
       0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1
      |Option Code=128|  Reserved     |           Length              |
      |                           Description                         |
      :                                                               :

        This Option:

         Option Name: DESCRIPTION
         Number: 128
         Purpose: Used to associate a text description with a mapping
         Valid for Opcodes: MAP, PEER
         Length: Variable,  maximum 1016 octets.
         May appear in: request. May appear in response only if it
                        appeared in the associated request.
         Maximum occurrences: 1

                       Figure 1: DESCRIPTION Option

   The 'Reserved' field is initialized as specified in Section 7.3 of

   The Description field MUST carry UTF-8 encoded [RFC3629] description
   text.  The description text MUST NOT be null terminated.  The length
   of the description text is indicated by the Length field.  In
   particular, the description text is not null terminated, and when a
   client or server receives a DESCRIPTION option, it MUST NOT rely on
   the presence of a NUL character in the wire format data to identify
   the end of the text.

   This option can be used by a user (or an application) to indicate a
   description associated with a given mapping, such as "FTP server",
   "My remote access to my CP router", "Camera", "Network attached
   storage serve", etc.

   How the content of the DESCRIPTION option is used is deployment-
   specific.  For example, the description text can be used by the
   entity managing the PCP server for many purposes, such as the

   o  The description text can be used as a hint when cleaning a mapping
      table by an administrator.

   o  In some deployments making use of a portal to instruct PCP
      mappings (e.g., Section 5.2 of [PCP-DEPLOY]), the description text
      can be used to store a subscriber identifier.

3.  Behavior

   Support for the DESCRIPTION option by PCP servers and PCP clients is
   optional.  This option (Code 128; see Figure 1) MAY be included in a
   PCP MAP/PEER request to associate a description with the requested

   A PCP server MAY ignore the DESCRIPTION option sent to it by a PCP
   client (e.g., if it does not support the option or if it is
   configured to ignore it).  To signal that it has not accepted the
   option, a PCP server simply does not include the DESCRIPTION option
   in the response.  If the PCP client does not receive a DESCRIPTION
   option in a response to a request enclosing a DESCRIPTION option,
   this means the PCP server does not support the option or it is
   configured to ignore it.

   If the DESCRIPTION option is not included in the PCP client request,
   the PCP server MUST NOT include the DESCRIPTION option in the
   associated response.

   A PCP server SHOULD be able to store at least 128 bytes for a
   description.  When the PCP server receives a DESCRIPTION option, it
   first stores the value of the received Description field, truncating
   it if it cannot store the entire value.  The server MUST then send
   the stored value back to the PCP client in the DESCRIPTION option in
   the response.

   If the PCP client request contains invalid DESCRIPTION options (e.g.,
   the content is not a legal UTF-8 string), the PCP server MUST ignore
   the request (i.e., MUST NOT return a DESCRIPTION option in the

   To update the description text of a mapping maintained by a PCP
   server, the PCP client generates a PCP MAP/PEER renewal request that
   includes a DESCRIPTION option carrying the new description text.
   Upon receipt of the PCP request, the PCP server proceeds to the same

   operations to validate a MAP/PEER request refreshing an existing
   mapping.  If validation checks are successfully passed, the PCP
   server replaces the old description text with the new one included in
   the DESCRIPTION option, and the PCP server returns the updated
   description text in the response, truncated (if necessary) as
   described above.

   The PCP client uses an empty DESCRIPTION option (i.e., Length set to
   0) to erase the description text associated with a mapping.  To
   indicate that the PCP server has successfully cleared the description
   text associated with a mapping, the PCP server returns the empty
   DESCRIPTION option in the response.

4.  Security Considerations

   PCP-related security considerations are discussed in [RFC6887].  In
   addition, administrators of PCP servers SHOULD configure a maximum
   description length that does not lead to exhausting storage resources
   in the PCP server.

   If the PCP client and the PCP server are not under the same
   administrative entity, the DESCRIPTION option has the potential to
   leak privacy-related information.  PCP clients should not use the
   DESCRIPTION option for such leakage.  For example, the option should
   not be used to include user identifiers, locations, or names.  Refer
   to Section 3.2 of [RFC6462] for a discussion on information leakage.

5.  IANA Considerations

   IANA has allocated the following value in the "PCP Options" registry
   (http://www.iana.org/assignments/pcp-parameters) from the optional-
   to-process range (see Section 19.4 of [RFC6887]):

      DESCRIPTION set to 128 (see Section 2)

6.  References

6.1.  Normative References

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

   [RFC3629]  Yergeau, F., "UTF-8, a transformation format of ISO
              10646", STD 63, RFC 3629, November 2003.
   [RFC6887]  Wing, D., Ed., Cheshire, S., Boucadair, M., Penno, R., and
              P. Selkirk, "Port Control Protocol (PCP)", RFC 6887, April

6.2.  Informative References

              Boucadair, M., "Port Control Protocol (PCP) Deployment
              Models", Work in Progress, April 2014.

   [RFC6462]  Cooper, A., "Report from the Internet Privacy Workshop",
              RFC 6462, January 2012.

   [RFC6970]  Boucadair, M., Penno, R., and D. Wing, "Universal Plug and
              Play (UPnP) Internet Gateway Device - Port Control
              Protocol Interworking Function (IGD-PCP IWF)", RFC 6970,
              July 2013.

Authors' Addresses

   Mohamed Boucadair
   France Telecom
   Rennes  35000

   EMail: mohamed.boucadair@orange.com

   Reinaldo Penno

   EMail: repenno@cisco.com

   Dan Wing
   Cisco Systems, Inc.
   170 West Tasman Drive
   San Jose, California  95134

   EMail: dwing@cisco.com


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