In my travels I have heard numerous times that it is a popular practice to give ICMP and even UDP traffic a lower priority on backbone routers in times of congestion.
The question was about the priority of ICMP. Perhaps I erred in mentioning that ICMP is important for congestion control. "Congestion control" is far too vague. Perhaps I should have used the more generic term "network control" instead. ICMP is an important protocol, and cannot be blocked blindly. As a protocol, it is not obsolete, though some functions are deprecated. In certain cases however, ICMP is given a high priority in the TOS field. --Dean ++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++ Plain Aviation, Inc dean@av8.com LAN/WAN/UNIX/NT/TCPIP http://www.av8.com ++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++