The MPLS WG Archive

[Philip Matthews <pmatthews@hyperchip.com>]

Title: Node-id: Concerned about using one of the last RRO flag bits for this

I would like to repeat my concerns with the proposal in
   draft-ietf-mpls-nodeid-subobject-01

Though I strongly support the concept of a node-id sub-object,
as it will be very useful for Fast Re-route,
I remain concerned about the proposal to use one of the
last unallocated flag bits in the RRO to indicate this object.

For those who have not read the draft, it proposes to use a flag
bit in the IPv4 or IPv6 address subject to indicate that the address
given in the subobject is not an interface address, but instead a router ID.
Nodes that wanted to include both an interface address and their
router id would include the IPv4 (or IPv6) subobject twice,
one with the flag set and one not.

To me, a much more obvious method is to assign a new type code
to the node-id subobject, rather than using a flag bit. Since there are
currently 252 unassigned subcodes, but only 3 unassigned flag bits
(or just 2 if this proposal goes through), it seems to me that
there needs to be a strong justification to use up one of the
three remaining bits.

I also feel that using a new type code would improve interoperability
with nodes that do not support this flag.

Am I missing something? Is there a good reason to use a flag bit?

- Philip