Subject: Re: Problem with BFD with ECMP

From: Alexander Vainshtein <[email-masked]>
Date: Fri, 9 May 2014 13:54:59 +0000

I concur with Jeff.

My 2c

Thumb typed on my LG,
Sasha

------ Original message ------
From: Jeffrey Haas
Date: 09/05/2014 16:27
To: Loa Andersson;
Cc: [email-masked];
Subject:Re: Problem with BFD with ECMP

On Fri, May 09, 2014 at 12:52:39PM +0200, Loa Andersson wrote:
> I guess that the answer to this type of question is somewhere around
> "Is it worth doing?". If we see an easy way to fix it and we are pretty
> sure that it will be deployed, then let us go ahead and do it. If the
> fix is shady and no one really want it, then just leave it.
>
> No in those terms where are we?

We are in the same state of Doom that we have been in for years. :-)

ECMP is a well known but not well specified bit of Internet architecture.
In some cases, it's a vendor differentiated feature and may differ depending
on platform, line card(s) and software revision.

Addressing the this in a general fashion would require some mechanism that
permitted exposing an algebra that documents traffic hashing on a hop by hop
basis, where hops may also include internals of a given device.

While I suspect such an effort is, I believe,  mathematically tractable, I
don't believe such a proposal would be well received.

In my opinion, I think we must proceed with an understanding that this
situation is status quo.  This means mechanisms that intend to probe
reachability have to contain a reasonable level of internal mistrust. "I can
see the far end, this path *might* work."

-- Jeff