[mpls] Comments on draft-kompella-larp

[Stewart Bryant <[e-mail]>]

Kireeti,

This is an interesting problem and we are pleased that you
have brought discussion of this topic to the IETF MPLS WG.
The proposal on the table however is a point solution and
it may be worth considering the wider problem of host
to network  MPLS interfaces (UNIs).

In particular whilst the majority of traffic is IPv4 today, the
stated policy of the IETF is to recognize the need to deliver IPv6
solutions and thus not to design IPv4 only solutions.

Whilst it is true that everyone does ARP, and ARP can in
principle be extended, the reality of the situation is that
the majority of ARP implementations are optimized IPv4
specific, and thus in most cases extending ARP would
require a similar effort to deploying a new IPv4/IPv6 agnostic
protocol for the UNI.

Given that Ethernet, whilst the most popular server network
interface, is not the exclusive interface and recognizing
that new link types may emerge, particularly in the IOT space,
it may serve us better to take an approach that is
MPLS specific but data-link neutral.

A further consideration is that whilst it may be possible to
extend ARP for other address families, it is not a protocol
that is well suited to the transport of other necessary
UNI information, for example, metrics, QOS information,
MTU, authentication, integrity, spectral information etc.

An alternative approach that is worth considering as a starting
point is described in draft-ietf-mpls-gach-adv (in the RFC
Editor's queue). When we wrote this draft we were attempting
to define a general UNI approach for MPLS with a focus on
simplicity.

If you are interested in exploring this with us further we
would be pleased to work with you on this.

Dan and Stewart