[c-nsp] packet processing delay & LLQ

[Volodymyr Yakovenko]

On Tue, Mar 15, 2005 at 05:21:13PM +0100, Oliver Boehmer (oboehmer) wrote:
>>  I need some advice in LLQ tuning for delay-critical traffic.
>> 
>>  As far as I know the right way to provide minimal delay for certain
>>  type of traffic is to put it into priority queue.
>> 
>>  To test it out I am using 2M Serial connected 2610 (Serial0/0) with
>>  the following LLQ configuration:
>> 
>> ip access-list ext NOC
>>  permit ip any host 172.20.2.20
>>  permit ip host 172.20.2.20 any
>> class-map match-any IS-NOC
>>   match access-group name NOC
>> policy-map E2
>>   class IS-NOC
>>    priority 512
>>   class class-default
>>    fair-queue
>> int Serial0/0
>>  service-policy output E2
>> 
>>  In clean channel case (no other traffic flowing on link) RTT (ping to
>>  172.20.2.20) over Serial is about 3ms. When I am saturating link with
>>  class-default traffic RTT jumps to about 90-110ms and remains almost
>>  stable. Priority queue works (class-default traffic RTT is 200ms and
>>  more), but delay value is not applicable.
> 
>you have LLQ enabled on both ends of the connection? Where is the
>172.20.2.20 located? On the router itself? What is the CPU load of the
>box when you saturate the link?

LLQ are configured on both ends. 172.20.2.20 is BSD machine connected ahead
Cisco router. On other side Cisco router there is same BSD machine.

Unfortunately I am not able to reproduce test case results. Same environment, 
same devices - different result, priority-matched traffic:

round-trip min/avg/max/stddev = 4.187/11.080/18.798/3.783 ms

class-default traffic:

round-trip min/avg/max/stddev = 7.680/15.276/34.544/4.806 ms

cpu utilization:

CPU utilization for five seconds: 15%/14%; one minute: 14%; five minutes: 12%

I will try all that again on weekend.

-- 
Regards,
Volodymyr.