North American Network Operators Group

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Re: backbone routers' priority settings for ICMP & UDP

  • From: Marc Slemko
  • Date: Tue Feb 03 15:56:49 1998

On Tue, 3 Feb 1998, Dean Anderson wrote:

> At 2:17 PM -0500 2/3/98, Marko B. wrote:
> >Greetings,
> >
> >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.

When a lot of people talk about that, what they are really referring to is
that an ICMP ping to a router can take longer to get a response than a
packet going through the router and coming back through it because packets
to the router have to be handled by the often puny CPU while packets
passing through normally don't.

> 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. 

> away, but the rest is necessary.