Subject: [pim] Question about draft-ietf-pim-ecmp

From: "Adrian Farrel" <[email-masked]>
Date: Sat, 24 Mar 2012 20:17:10 -0000

Hi authors of draft-ietf-pim-ecmp,

I'm doing my AD review in response to the publication request for your draft.

One point has me confused (Only one point? It must be a short draft).

I can't decide whether this document is intended to apply to ECMP between
adjacent routers (i.e. parallel links), or a more generic ECMP across the
network (i.e. parallel paths).

The concept of ECMP bundle in Section 3 encourages me to think you are talking
about parallel links, but then the document talks about selection of a different
upstream router, which must mean parallel paths.

If parallel paths are the intention of the document then there are some oddities
that confuse me further: the addition of a member of an ECMP bundle seems to be
based on configuration which is fine for parallel links, but it seems a much
larger issue to configure an ECMP bundle across a collection of routers, and it
could lead to the actual path being not the shortest; the definition of an ECMP
bundle seems to require that all bundle members have the same upstream and
downstream ends; an upstream router is required to announce that it is not the
preferred router which requires it to know about all other upstream routers that
are an option for the computed path.

Can you sort me out on this point so that I can complete my review?

Thanks,
Adrian

---

From: Liming Wei <[email-masked]>
Date: Sat, 24 Mar 2012 21:36:17 -0700

Hi Adrian,

This document is intended to apply to ECMP links between routers 
adjacent to each other.
Your assumption about the downstream routers sharing the same set of 
ECMP "next hop"'s is correct.

  Thanks,
-Liming

On 3/24/12 1:17 PM, Adrian Farrel wrote:
> _______________________________________________
> pim mailing list
> [email-masked]
> https://www.ietf.org/mailman/listinfo/pim

---

From: "Adrian Farrel" <[email-masked]>
Date: Mon, 26 Mar 2012 12:25:55 +0100

Thanks for that.

I may pick out some points where you need to make this a bit clearer.

Cheers,
Adrian

> -----Original Message-----
> From: Liming Wei [mailto:[email-masked]]
> Sent: 25 March 2012 05:36
> To: [email-masked]
> Cc: [email-masked]; [email-masked]
> Subject: Re: [pim] Question about draft-ietf-pim-ecmp
> 
> Hi Adrian,
>