Technical Summary
RFC 3032 established two data link layer codepoints for MPLS, used to
distinguish whether the data link layer frame is carrying an MPLS
unicast or an MPLS multicast packet. However, this usage was never
deployed. This specification updates RFC 3032 by redefining the
meaning of these two codepoints. Both codepoints can now be used to
carry multicast packets. The second codepoint (formerly the
"multicast codepoint") is now to be used only on multiaccess media,
and it is to mean "the top label of the following label stack is an
upstream-assigned label".
RFC 3032 does not specify the destination address to be placed in the
"MAC DA" field of an ethernet frame which carries an MPLS multicast
packet. This document provides that specification.
This document updates RFC 3032 and RFC 4023.
Working Group Summary
No controversy reported (see PROTO writeup by Loa Andersson).
This document, along with one other (draft-ietf-mpls-upstream-
label) are the forerunners on a set of multicast documents that
are being worked on and have been widely discussed in the working
group and will be submitted to the IESG once these two documents
are approved.
Document Quality
The document has been well reviewed, and represents clear consensus
in the WG. It is also the basis of related ongoing work.
Implementation of draft-ietf-mpls-multicast-encaps is quite
straightforward. However, in and of itself it is not useful.
Rather protocol specifications that will make use of this
encapsulation are currently being progressed in the MPLS WG.
The reason for pushing this document forward at this time is
because:
o It forms a clear means of updating RFC 3032
o Ensures that protocols needing such an encapsulation will be
done consistently
Personnel
Loa Andersson is the document shepherd, however both WG chairs
(Loa and George) have reportedly reviewed the document. Ross Callon
is the responsible AD. Ross will inquire regarding choice of IANA
expert.