large organization nameservers sending icmp packets to dns servers.

Valdis.Kletnieks at Valdis.Kletnieks at
Mon Aug 6 17:37:06 UTC 2007

On Mon, 06 Aug 2007 12:13:03 EDT, "Steven M. Bellovin" said:

> > 1) ICMP is handled at the same rate as TCP/UDP packets in all the
> > routers involved (so there's no danger of declaring a path "slow"
> > when it really isn't, just becase a router slow-pathed ICMP).
> This is aimed at hosts, not routers, right?  As far as I know, routers
> don't slow-path forwarded ICMP.  Hosts will probably reply to ICMP from
> their kernel, so it's a faster response than a user-level DNS reply.

Well, they don't *directly* slow-path it.  But we've seen *plenty* of cases
of "multi-hop performance as indicated by ICMP Echo Request/Reply doesn't at
all match throughput/latency as indicated by TCP-level stats" mentioned on
this list...
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