Re: [Idr] I-D Action: draft-ietf-idr-rs-bfd-03.txt

["John G. Scudder" <[e-mail]>]

On Jul 4, 2017, at 5:26 AM, Job Snijders <[e-mail]> wrote:
> We already observed that path _diversity_ isn't that great at IXPs in
> the sense that often there is only a single path towards a prefix:
> https://mailarchive.ietf.org/arch/msg/idr/qhgG2cCs0UuDHdPRdfDIMs7jeHs

which earlier message says in part:

> AMS-IX RS indicated that one out of three routes have an alternative path
> DE-CIX RS 1 out of 2 routes have an alternative path
> INEX RS seemed to have virtually no alternative paths for the routes


The first two seem to me like non-trivial cases of diversity, although of course well short of full coverage. One thing not taken in by your quick survey is whether there's any correlation between traffic and diversity (e.g., it could be that the 1 out of 2 DE-CIX routes that have alternative paths account for well over 50% of the traffic). I don't necessarily advocate trying to go down the path of generating these statistics, because the "one out of two routes would benefit" point already seems like reasonable motivation to me. I'm merely cautioning against reading the numbers as being more conclusive than they are.

--John