Re: [Idr] I-D Action: draft-ietf-idr-rs-bfd-02.txt

Robert Raszuk <robert@raszuk.net> Tue, 14 March 2017 10:05 UTC

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From: Robert Raszuk <robert@raszuk.net>
Date: Tue, 14 Mar 2017 11:05:05 +0100
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To: Randy Bush <randy@psg.com>
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Subject: Re: [Idr] I-D Action: draft-ietf-idr-rs-bfd-02.txt
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Randy ..

Any ASBR (even software running in a VM or container) today used as peering
router can handle Internet table. That is 600K+ nets.

IXes give you tiny subset of it via open or selective policy. Moreover as I
mentioned in my original comment - over RS you get local customer and
internal routes and no more. So for any net it will be usually one or two
paths anyway.

So if someone has one path (and client has no way of knowing) signalling to
RS that next hop is gone is not helpful as there is no backup path RS could
recompute and send to such client.

Learning two paths for given net with different NHs (even if RS has more
then two) seems to provide sufficient robustness and enables you to measure
quality to the destinations as well as do things line multipath TCP

= =  =

Little suggestion:

Now if someone is really so weak on the edge and attaches to IX to only
peer locally we should perhaps invent co-located with RS pair of data plane
boxes where such weak guys would for forwarding just default to such data
plane gateway. That way those two forwarders could have as many paths as RS
feeds it with yet all weak clients are happy to forward and reach all open
peers of a given IX.

In fact most IX switches while running in L2 mode could be configured for
L3 as well so no need to even invest new $$$ needed.

Kind regards,
Robert.




On Tue, Mar 14, 2017 at 10:52 AM, Randy Bush <randy@psg.com>; wrote:

> >> why do folk use RS?  to offload the bgp decision process.
> > RS are used to establish one (or two) eBGP session and get all the
> > juice. ‚Äč
>
> that is one.  my case is one.  and there are others.
>
> folk are at large exchanges with small routers; some can handle about
> one view.  they do not have the horsepower to make best next hop choices
> from large sets.  we should not disenfranchise them.
>
> randy
>