Re: network controls are necessary

[Bill Sommerfeld <sommerfeld@orchard.arlington.ma.us>]

> |   Maybe a site could withdraw the identifier->locator mapping when a
> |   link is known to have lost connectivity, but that clearly limits
> |   what can be done to cache identifier-locator mappings..
> 
> Oy.  I think the thought was that the routing system would detect the
> loss of connectivity via the locator and would send an ICMP unreachable,
> which would then trigger a switch to an alternate locator.

I thought of that sort of mechanism but immediately dismissed it; it's
got a track record of failing miserably in the as-built Internet[1].
I'm skeptical that this would be effective without some sort of
black-hole detection (rotating to a new locator after a couple RTO's
of silence?).

					- Bill

[1] Path MTU discovery.  Try surfing the web with a <1500 MTU
bottleneck in the path some time.  PPPoE implementations which rewrite
TCP MSS options don't count.