[e-nsp] Extreme Networks Summit1iTx L3 switch delays ICMP traffic routed through the switch or addressed to the switch

[Martin T]

Mikael,

in this case it all makes sense. Thanks!


regards,
Martin

On 9/1/14, Mikael Abrahamsson <swmike at swm.pp.se> wrote:
> On Mon, 1 Sep 2014, Martin T wrote:
>
>> Thanks for all the information! So in case the utilization of tBGTask
>> process is less than 90%, all the other IP traffic should suffer as
>> well?
>
> No. By default ICMP is slow-pathed, everything else is fast-pathed. ICMP
> can be made fast-pathed on some incarnations i-chipset platforms by
> issuing "disable icmp access-lists". They re-spun the forwardig ASICs back
> in 2004-2005 or so to enable this feature, as the inferno chipset in the
> original design punted all ICMP to CPU, they introduced a system-wide flag
> to disable this behavior. Since the ASIC doesn't have the capability to
> inspect ICMP in fast-path, when you change this flag, you no longer can
> ACL ICMP at all.
>
> If you're running i-chipset devices as routers and have a decent amount of
> flows, I also recommend to "enable ip-subnet lookup" feature. A masksize
> of /20 or so is a balanced approach for Internet use. This helps to not
> deplete the ipfdb and also speeds of convergence after a re-route.
>
>> For some odd reason I didn't observe this. Based on my
>> tests(hping and custom-made script utilizing bash UDP and TCP
>> sockets), only the RTT of ICMP traffic increased while RTT for example
>> for UDP or TCP traffic did not change at the time when CPU utilization
>> of tBGTask was <90%.
>
> That is default behavior.
>
> --
> Mikael Abrahamsson    email: swmike at swm.pp.se
>