On 2008-10-14 16:31, Kai Schaetzl wrote:
Sean Carolan wrote on Tue, 14 Oct 2008 08:13:34 -0500:
My mail logs are showing that customers who specifically disallow ICMP
traffic have many "Connection Reset" entries in our logs:
Could somebody explain why ICMP might play a role in mail delivery?
Any host may reply to a IP-datagram (tcp included) with e.g. ICMP type 3,
code 4 "datagram too large" and indicating the maximum size in the ICMP reply.
Disallowing these ICMP packets can result in a TCP handshake that
succeeds, but hangs when the next packets with real data are blocked.
http://en.wikipedia.org/wiki/PMTUD
--
Paul Bijnens, xplanation Technology Services Tel +32 16 397.511
Technologielaan 21 bus 2, B-3001 Leuven, BELGIUM Fax +32 16 397.512
http://www.xplanation.com/ email: Paul.Bijnens@xxxxxxxxxxxxxx
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