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
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
   | DESCRIPTION   |  Reserved     |           Length              |
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
   |                           Description                         |
   :                                                               :
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
      
     This Option:

      Option Name: Description Option (DESCRIPTION)
      Number: TBA in the optional-to-process range (IANA)
      Purpose: Used to associate a text description with a mapping
      Valid for Opcodes: MAP, PEER
      Length: Variable
      May appear in: both request and response
      Maximum occurrences: 1

Figure 1: Description Option

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.

Issues related to the usage of this field for troubleshooting or for any further usage are out of scope of this document.

3. Behaviour

DESCRIPTION Option is optional to be supported by PCP Servers and PCP Clients.

This option (Code TBA, Figure 1) MAY be included in a PCP MAP/PEER request to associate a description with the requested mapping.

The PCP Server MAY be configurable to accept the DESCRIPTION Option. If the PCP Server does not support the DESCRIPTION Option or it is configured to ignore it, received DESCRIPTION Options MUST be ignored by the PCP Server and no DESCRIPTION Option MUST be included in the response. The PCP Server MUST store the content of DESCRIPTION Option only if it supports the DESCRIPTION Option and if it is configured to accept handling DESCRIPTION Options it receives.

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 that Option. The PCP Client SHOULD avoid including the DESCRIPTION Option in any subsequent request to that PCP Server.

If the DESCRIPTION Option is not included in the request, the PCP Server MUST NOT include the DESCRIPTION Option in the associated response.

The PCP Client MUST NOT include empty DESCRIPTION Option (i.e., Length set to 0) in a request. Empty DESCRIPTION Options MUST be ignored by the PCP Server.

The maximum length SHOULD be configurable in the PCP Server. If a PCP Client includes a DESCRIPTION PCP Option with a length exceeding the maximum length supported by the PCP Server, only the portion of the Description field fitting that maximum length is stored by the PCP Server and returned to the PCP Client in the response.

If the PCP Server receives a DESCRIPTION Option having a length which does not exceed the maximum value configured, the PCP Server MUST record the complete sequence of the description text and MUST send back to the PCP Client the same DESCRIPTION Option as the one included in the request. If the description text carried in the DESCRIPTION Option is null terminated, the exact description text, including Null characters, MUST be returned by the PCP Server.

4. Security Considerations

Security considerations discussed in [I-D.ietf-pcp-base] must be considered. In addition, administrators of PCP Servers SHOULD configure a maximum description length which does not lead to exhaust storage resources in the PCP Server.

Within this document, the content of DESCRIPTION Option is not used as a hint to construct a mapping in the PCP Server. If future documents make use of this option to influence the PCP Server decisions, those document MUST elaborate on the associated security considerations.

5. IANA Considerations

The following PCP Option Codes are to be allocated in the optional-to-process range:

• DESCRIPTION

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.
[I-D.ietf-pcp-base]	Wing, D., Cheshire, S., Boucadair, M., Penno, R. and P. Selkirk, "Port Control Protocol (PCP)", Internet-Draft draft-ietf-pcp-base-29, November 2012.
[RFC3629]	Yergeau, F., "UTF-8, a transformation format of ISO 10646", STD 63, RFC 3629, November 2003.

6.2. Informative References

[I-D.ietf-pcp-upnp-igd-interworking]

Boucadair, M., Penno, R. and D. Wing, "Universal Plug and Play (UPnP) Internet Gateway Device (IGD)-Port Control Protocol (PCP) Interworking Function", Internet-Draft draft-ietf-pcp-upnp-igd-interworking-06, December 2012.

Authors' Addresses