[alcatel-nsp] Smoothness of egress shaped scheduler-policy with multi-service-site.

[Smith, Anton (Anton)]

Hi Pawel,

Try egress-rate under the port itself.

conf port 1/1/1 ethernet egress-rate

Not sure but you might also need to reference the port parent scheduler from your service schedulers.

Regards,
Anton

From: alcatel-nsp-bounces at puck.nether.net [mailto:alcatel-nsp-bounces at puck.nether.net] On Behalf Of Pawel_Sikora at netia.pl
Sent: Monday, March 28, 2011 6:42 PM
To: alcatel-nsp at puck.nether.net
Subject: [alcatel-nsp] Smoothness of egress shaped scheduler-policy with multi-service-site.

Hi.
I was forced to use ill-behaving transmission devices (EoSDH) that have netto speed STM-1 and GE ports, but have only single 16kB packet buffer available at the bottleneck.
The traffic I must pass through it is rather bursty*  and comes from the GE port of 7750.
It is sourced from dozen of SAP-s (several different services with aggregated classes).
*(mainly Internet access)

I can shape it together to the given average max rate (i.e.150Mbps), using multiservice-site scheduler-policy with parent port scheduler, but observe that
still some bursts of traffic leaves from the SR port that 16kB buffer cannot accomodate (mtu used on every service is no more than 1564B).
The symptoms are both reported as buffer overflows on EoSDH port (sdh side) and visible as lost packets in ordinary ping.
Unfortunately the lost packets are observed even at average utilization of 70-80 Mbps, far below the physical link capacity.

Constant, non-bursty flows generated form traffic tester show proper shaping and smooth operation of EoSDH box,
 but after introducing some burstiness on traffice source (that enters SR) I observe drops on the the EoSDH small buffer.

Is there any parameter or guideline how to tune the scheduler behaviour , to achieve better smoothness on egress port traffic?

In contrast, I've connected the Cisco 3750 with ordinary egress port bandwith limit feature (still using four different traffic classes within shaped speed),
and there are no drops on EoSDH box, up to the link capacity on the same traffic type.

Regards
Pawel/

(SR-7 with 8.0.6 and IOM2)
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