Subject: [mpls] Comments on draft-kompella-larp

From: Stewart Bryant <[email-masked]>
Date: Thu, 06 Mar 2014 09:10:28 +0000

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

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From: Stewart Bryant <[email-masked]>
Date: Thu, 06 Mar 2014 09:16:21 +0000

Resending adding Matthew to the CC list.

On 06/03/2014 09:10, Stewart Bryant wrote:
> _______________________________________________
> mpls mailing list
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> https://www.ietf.org/mailman/listinfo/mpls
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From: Kireeti Kompella <[email-masked]>
Date: Thu, 6 Mar 2014 13:22:40 +0000

Hi Stewart,

> have brought discussion of this topic to the IETF MPLS WG.

Cool.

> solutions and thus not to design IPv4 only solutions.

Got that message; will fix.

> require a similar effort to deploying a new IPv4/IPv6 agnostic

Understood that this will be new code; the actual code isn’t that much, though.

> MPLS specific but data-link neutral.

ARP is not Ethernet specific.  We prefer to have different code points for MPLS-over-Ethernet, MPLS-over-foo, etc. rather than have TLVs for the link layer.

> MTU, authentication, integrity, spectral information etc.

What we are going for is simplicity.  We have metrics and entropy label capability on deck; but we really don’t want to add too much more.

> to define a general UNI approach for MPLS with a focus on

I took a quick look.  The immediate question is, can gach-adv be run over native Ethernet?  I don’t see a UDP port or IP encoding.  I do see that this can be used over MPLS; but the L-ARP draft is for establishing tunnels when you have none.  That’s why I prefer something that runs at the link layer.

If I missed something, please let me know.

Cheers,
Kireeti.

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From: "Stewart Bryant (stbryant)" <[email-masked]>
Date: Thu, 6 Mar 2014 14:03:30 +0000

Just a quick response.

It runs over MPLS, and you can run MPLS(GAL) over datalinks.

Stewart

> On 6 Mar 2014, at 13:22, "Kireeti Kompella" <[email-masked]> wrote:
> 
> Hi Stewart,
>