Liaison from MPLS & Frame Relay Alliance on RFC 3036 Proposed Revisions
Date: 7 October 2004
From: Alexa Morris <a morris@mplsforum.org>

Dear George, Loa and Ina:

A recent message on the MPLS WG mailing list
(http://www.cell-relay.com/mhonarc/mpls/2004-Sep/msg00043.html) has
suggested changes to RFC 3036 ("LDP Specification") and called for comments
on the proposed changes. One of the proposed changes is to deprecate the
use of the Host Address FEC TLV. Two Implementation Agreements published by
the MPLS & Frame Relay Alliance (MFA), "MPLS Proxy Admission Control
Definition" and "MPLS Proxy Admission Control Protocol", MFA.6.0.0 and MFA.7.0.0
(http://www.mplsforum.org/tech/mpls-proxy-admission-control-definition-ia.pdf 
and http://www.mplsforum.org/tech/mpls-proxy-admission-control-protocol-ia.pdf)
make use of the Host Address FEC TLV. MPLS Proxy Admission Control provides
a bandwidth-based reservation/admission facility for MPLS networks. There
are implementations of this protocol in progress.

While the proposed changes make a Prefix FEC TLV with a 32-bit mask
equivalent to a Host Address FEC TLV, adopting the Prefix FEC TLV would
require changes to approved and published MFA documents, and changes to the
implementations. Also, since MPLS Proxy Admission Control only uses host
addresses, using the Prefix FEC TLV would necessitate an additional check
that the prefix was always 32 bits. Therefore, the MFA kindly requests that
the Host Address FEC TLV not be deprecated, and that it continues to be
supported in future revisions of LDP.

In RFC 3036, there is a semantic difference between a Host Address and a
prefix with length 32. The new version proposes to remove the semantic
difference. This is not a problem for the MPLS Proxy Admission Control; we
are just requesting that the Host Address codepoint not be deprecated.

Please advise us as soon as possible about the decision on this issue.

Cordially,
Rao Cherukuri
MPLS & Frame Relay Alliance
Technical Committee Chair