On Tue, Jul 02, 2013 at 06:48:14AM +0200, Mikael Abrahamsson wrote:
> On Tue, 2 Jul 2013, Juliusz Chroboczek wrote:
> 
> >Anybody seen anything similar?
> 
> I don't know if this is the cause, but older gear from Extreme
> Networks (their end-of-90ties and beginning of 2000s), will do ICMP
> in slow-path when routing (even packets going through the device) and
> "everything else" in fast-path. This could cause latency spikes and
> PDV approximately similar to what's seen in the picture.

This looks like a plausible explanation, thanks.  They may not be the
only router make to exhibit this behaviour.

Is there a reason for this slow-path routing of ICMP?  I've seen
routers applying some kind of rate-limiting to ICMP packets, but as
far as I know, it's only limited to ICMP packets originating from the
router.