Unreachable messages

[karn@ka9q.bellcore.com (Phil Karn)]

Doug,

You can still see the unreachable messages, but you have to say
"icmp trace on" first.

As for the ICMP messages not resetting the session, this is a feature, not a
bug. In fact, it's in the Requirements for Internet Hosts RFC.

The reason is that ICMP messages are often transitory by nature, and you
don't want them resetting connections unnecessarily. The operator always has
the option of resetting the connection manually if he sees too many
unreachable messages, and the TCP backoff keeps the network from getting
congested even if it is allowed to retry forever.

Phil