Re: [v6ops] PI heresy [draft-ietf-v6ops-ula-usage-recommendations - work or abandon?]

[Gert Doering <[e-mail]>]

Hi,

On Fri, Nov 13, 2015 at 01:49:13PM +0100, Philip Homburg wrote:
> >Networks break further upstream, without the actual upstream being
> >noticeable
> >broken.  Networks break certain paths, while others are working fine.
> >
> >We can do better than all-or-nothing.  We should.
> 
> I don't think a host should try to figure out which paths work and which
> don't.

I disagree, and strongly so.  Maybe not "probe all paths at the same time",
but if one is not working, it would be silly not to try alternatives if
they exist.

[..]
> I propose that routers just inform hosts which source prefixes are unusable
> according to unspecified monitoring code running on the router. (Obviously,
> routers should also propate that knowledge over internal routing protocols in
> setups with multiple routers).

So, if you have upstreams A and B, and targets C and D, of which "C" cannot
be reached over "A" and "D" not via "B" (not all that unlikely given the
direction in which low-price SoHo ISPs and peering wars are developing),
would you rather declare both broken, or just use B to reach C, and A to
reach D?

Defining "the upstream is broken" is actually fairly hard - the router might
be perfectly happy about upstream A, because 99% of its monitoring targets
work perfectly well - but if the user's 1% that he wants to talk to do not
work (routing hickup, anycast cluster broken, peering overloaded), it is
the wrong conclusion to declare "it is working, no need to try anything
else"...

Gert Doering
        -- NetMaster
-- 
have you enabled IPv6 on something today...?

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