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AW: Phantom packet loss is being shown when using pathping in connection with asynchronous routing - although there is no real loss.

  • From: Gunther Stammwitz
  • Date: Tue Jun 06 11:39:47 2006

Hello Alan,

Thanks for your reply.
I know that icmp is being handled by the router's cpu and that the
forwarding is being done in hardware.
The interesting part here is that the loss starts at the router where the
asynchronous routing begins and is even being seen at the final destination
host - but this only happens with pathping and mtr. An ordinary ping doesn't
show this problem.

The problems in mtr/pathping disappear when a synchronous routing is being
established.


What's the case for this? What are the programmers of mtr and pathping doing
wrong or is there another problem mayb in the implementation of icmp?

Gunther


> -----Ursprüngliche Nachricht-----
> Von: Alan Clegg [mailto:alan@clegg.com] 
> Gesendet: Dienstag, 6. Juni 2006 17:27
> An: Gunther Stammwitz
> Betreff: Re: Phantom packet loss is being shown when using 
> pathping in connection with asynchronous routing - although 
> there is no real loss.
[..]
> 
> I'd guess that the routing devices are just droping/ignoring 
> ICMP echo request packets.  They are the least interesting 
> packet, and are quite often, responses to them are given 
> extremely low priority.
> 
> Just my guess,
> AlanC





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