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Re: backbone routers' priority settings for ICMP & UDP
On Tue, 3 Feb 1998, Marc Slemko wrote: > On Tue, 3 Feb 1998, Dean Anderson wrote: > > > > > ICMP in general is or should be given higher priority, since it is > > necessary for congestion control. Echo requests (pings) could be thrown > > Please, tell me of this magic ICMP that is used for congestion control. > Obsolete things that are now recommended against don't count. Since so many people are telling me all about the wonders of ICMP source quench messages, may I remind them of section 220.127.116.11 of RFC-1812 which says: A router SHOULD NOT originate ICMP Source Quench messages. As specified in Section [4.3.2], a router that does originate Source Quench messages MUST be able to limit the rate at which they are generated. Sure, hosts can generate them, but that is seldom of much utility (especially in the discussion here about network congestion control as opposed to host/processing congestion control) because the network is more often the backlog than the host, and the host can't generate messages saying the network is congested. ICMP messages are not a commonly used or particularily useful method of congestion control on the Internet today.