[c-nsp] 6500 / 7600 output drops

[Richard Harvey]

If you're getting output drops then the interface may well be getting
genuinely congested, albeit on a very temporary basis. 

I have seen an IPTV platform achieve a target streaming rate by
'bursting' at full line rate - eg. 100mbps achieved by sending full
1Gbps of traffic then 9 x 0Gbps of traffic every interval. Add this to
the existing background unicast traffic and you have easily filled the
egress buffers of a 67xx card during the burst. 

I was able to resolve my issue by attaching the headend at a lower
access rate, (100mb in this case), reducing it's ability to fill core
links. A little crude, but very effective!

Richard


-----Original Message-----
From: cisco-nsp-bounces at puck.nether.net
[mailto:cisco-nsp-bounces at puck.nether.net] On Behalf Of Colin Whittaker
Sent: 16 April 2007 15:00
To: cisco-nsp at puck.nether.net
Subject: [c-nsp] 6500 / 7600 output drops

Hi All, 

We are seeing some very serious with output drops on our 6500 / 7600
platforms. We have sup720-3b with 6748 series lines cards, rj45 and sfp.

We have our IPTV headend connected via a single interface (int 1)  and
is producing 400 - 450 Mbit/sec of multicast traffic. 
We have a downstream network connected to a second interface (int 2)
that is watching all the tv channels at the same time and so all groups
are forwarded out int 2 With just multicast traffic flowing between two
interfaces everthing works fine but as soon as we add any unicast
traffic to the downstream network which enters the 7600 via a different
ingress interface we start to see output drops on interface 2 and the
associated problems in the video.

The unicast traffic is about 200Mbit/sec so the total traffic on the
link is 600Mbit/sec at 50kpps

Disabling QOS / giving the video queue the highest priority don't seem
to make a difference. 

Is there anything else I should try.

Colin
-- 
Colin Whittaker						+353 (0)86 8211
965
http://colin.netech.ie
colin@(magnet|netech).ie
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