Subject: RE: network controls are necessary

From: "Tony Li" <[email-masked]>
Date: Mon, 9 Dec 2002 11:09:33 -0800

|   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.

Tony

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From: Bill Sommerfeld <[email-masked]>
Date: Mon, 09 Dec 2002 14:32:01 -0500

> 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.

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From: "Craig A. Huegen" <[email-masked]>
Date: Mon, 9 Dec 2002 16:12:17 -0600 (Central Standard Time)

> which would then trigger a switch to an alternate locator.

I'm slightly concerned about the security/DoS implications of allowing
unsolicited messages to vastly affect connectivity, even though some
topologies support the use of ingress filtering and unicast-RPF to
mitigate.

I'm also concerned with the network device having to send back all those
ICMP messages in response to active traffic in case of a major link
failing.

/cah

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Craig A. Huegen, Chief Network Architect      C i s c o  S y s t e m s
IT Transport, Network Technology & Design           ||        ||
Cisco Systems, Inc., 400 East Tasman Drive          ||        ||
San Jose, CA  95134, (408) 526-8104                ||||      ||||
email: [email-masked]       CCIE #2100      ..:||||||:..:||||||:..