RFC 6887, "Port Control Protocol (PCP)", April 2013

Note: This RFC has been updated by RFC 7488, RFC 7652, RFC 7843

Errata ID: 3891
Status: Held for Document Update
Type: Technical
Publication Format(s) : TEXT
Reported By: Matt Dainty
Date Reported: 2014-02-14
Held for Document Update by: Ted Lemon
Date Held: 2014-02-17

Section 13.3 says:

The Prefix Length indicates how many bits of the address are used for
the filter.  For IPv4 addresses (which are encoded using the
IPv4-mapped address format (::FFFF:0:0/96)), this means valid prefix
lengths are between 96 and 128 bits, inclusive.  That is, add 96 to
the IPv4 prefix length.  For IPv6 addresses, valid prefix lengths are
between 0 and 128 bits, inclusive.  Values outside those ranges cause
the PCP server to return the MALFORMED_OPTION result code.

To remove all existing filters, the Prefix Length 0 is used.  There
is no mechanism to remove a specific filter.

It should say:

The Prefix Length indicates how many bits of the address are used for
the filter.  For IPv4 addresses (which are encoded using the
IPv4-mapped address format (::FFFF:0:0/96)), this means valid prefix
lengths are between 97 and 128 bits, inclusive.  That is, add 96 to
the IPv4 prefix length.  For IPv6 addresses, valid prefix lengths are
between 1 and 128 bits, inclusive.  Values outside those ranges cause
the PCP server to return the MALFORMED_OPTION result code.

To remove all existing filters, the Prefix Length 0 is used.  The
Remote Peer Port and Remote Peer IP Address fields MUST be set to zero
on transmission and MUST be ignored on reception.  There is no
mechanism to remove a specific filter. 

Notes:

A mapping with a filter containing an address-specific prefix length of 0 doesn't provide any value as it's no different to a mapping with no filters at all.

Since a prefix length of 0 is not even possible for IPv6 addresses, it should not be possible for IPv4 addresses either. Therefore the valid prefix length range for IPv4 addresses should be 97 to 128 bits inclusive and the valid range for IPv6 addresses should be documented as 1 to 128 bits inclusive in addition to a prefix length of 0 being documented as the special case.

Also clarify in that special case that it doesn't matter what the remote peer port and IP address fields are and therefore follow the convention throughout the RFC of setting to zero on transmission and ignoring on reception.

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