Re: XTRA network having problems?

21 Aug 2001


      I have no idea.. but if someone is filtering out All ICMP on Public Routable
Addresses then they are "Breaking the NET" for a large number of users.. A
little anoying yes. Also still a large number of routers still break ECN
:-(

Thanks
Craig Whitmore
Orcon Internet
http://www.orcon.net.nz

----- Original Message -----
From: "Dean Pemberton" 
To: "Don Stokes" 
Cc: 
Sent: Wednesday, August 22, 2001 1:02 PM
Subject: Re: XTRA network having problems?
...
Now correct me if I'm wrong.  But hasn't xtra/telecom always filtered out
ICMP?
...
Dean
On Wed, Aug 22, 2001 at 12:16:53PM +1200, Don Stokes wrote:
...
"Gordon Smith"  wrote:
...
Site is up.
All ICMP is blocked at the border router, instead of just filtering out
undesirable ICMP traffic...
If you're really filtering *all* ICMP traffic, you've broken it.  Path
MTU discovery relies on ICMP fragmentation-required messages getting
through, and *lots* of TCP implementations rely on MTU path discovery.
It works fine as long as the MTUs are all the same, but when they
aren't, or if encapsulation such as ESP or GRE are in use, it doesn't.
ICMP is there for a reason.  If you don't know what you're doing, don't
touch it.
-- don
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