[c-nsp] packet processing delay & LLQ

[Dmitry Volkov]

Volodymyr,

try to change "tx-ring-limit 4"

Oliver, since You are from Cisco, would You please let us know whether this
below is valid for serial interfaces as well ? :

http://www.cisco.com/en/US/partner/tech/tk39/tk824/technologies_tech_note091
86a00800c9699.shtml#net
<quote>
The FIFO queue on the port adaptor stores the packets before they are
segmented into cells for transmission. When this queue is full, the port
adaptor or network module signals to the IOS software that the queue is
congested. This mechanism is called back-pressure. On receiving this signal,
the router stops sending packets to the interface FIFO queue and stores the
packets in the IOS software until the queue is uncongested again. When the
packets are stored in IOS, the system can apply QoS.
</quote>


I don't see any reason for FIFO queue when CBWFQ is enabled


Thanks
Dmitry

> -----Original Message-----
> From: cisco-nsp-bounces at puck.nether.net 
> [mailto:cisco-nsp-bounces at puck.nether.net]On Behalf Of Oliver 
> Boehmer (oboehmer)
> Sent: Tuesday, March 15, 2005 11:21 AM
> To: Volodymyr Yakovenko; cisco-nsp at puck.nether.net
> Subject: RE: [c-nsp] packet processing delay & LLQ
> 
> 
> 
> > 
> >  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?
> 
> 	oli
> 
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