Re: missing icmp errors for udp packets

From: Pekka Savola (
Date: Tue Jul 31 2001 - 14:59:39 EST

On Wed, 1 Aug 2001, Chris Wedgwood wrote:
> --- cheap router thing
> "really good ping responder" is a pointless purpose.

bad ping responder == bad PR ;-)

And anyway, who is anyone to judge what the system should be used for?

I want a system to respond to ping without limitations; it's good for
debugging, diagnostics, etc. If I want, I can just filter the requests
out, or rate-limit the responses.

However, ICMP error messages cannot be effectively filtered; they may
happen due to TTL=0 when forwarding, legit or illegit UDP connection etc.;
only way to effectively limit them is by rate-limiting. If rate-limiting
with informational and error types are the same, we have an inflexible
situation here.

> Then kernel must be shipped out without rate-limiting enabled by
> default, that's problem.
> I guess I missed something. That doesn't seem like a problem to
> me... and if you need to ship with a rate by default, then ship with a
> very-high rate. I've never managed to respond to more than 60,000
> ICMP packets/second, so I suggest 60,001.

Yes you did. 60,000 responses/sec is effectively no protection at all,
and most people would appeaciate protection for the error messages, which
are crucial to the working of TCP/IP; not so with informational ICMP

And by the way, rate-limiting ICMP error messages is a MUST item for IPv6.

Pekka Savola                 "Tell me of difficulties surmounted,
Netcore Oy                   not those you stumble over and fall"
Systems. Networks. Security.  -- Robert Jordan: A Crown of Swords

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