> "firewalls MUST NOT block packets that the legitimate use of the Internet
> rely on for proper operation" or something like that.

 Probably 10% of the complaints to our security mailbox are from people hyper-
ventilating over our backbone routers "hacking their computer" with ICMP
packets.

> So, the trick is to find the RFC #, and contact the owner of the firewall and
> scream that they are "not RFC-mumble compliant!!!"  :-)

 Good luck. I often refer admins to http://www.worldgate.com/~marcs/mtu/.