On Fri, 10 Jul 2009, victor wrote:
We are getting ready a residential triple-play network for the launch. As
part of my job I'm conducting various tests on its performance, delays,
etc before we go into production. Today was the multicast time and testing
it I got very discouraging results. Under very moderate load of 15 IPTV
streams (each approximately 1-1,5Mbps) the cpu gauge on the core C7604
increased by 15% but on the distribution C4924 hit 50% from zero! When I
went on with the test and launched iperf adding one more 50 Mbps stream in
udp multicact mode to stress-test both even more the cpu utilization on
C7604 became 60% and on C4924 hit 100%. It even became visible as the
responses of the telnet console considerable slowed down.
Both switches work as ip multicast routers in sparse-dense mode. The RP is
C7604. Apparently all the multicast traffic gets process switched, though
I explicitly entered “ip mroute-cache” under every interface.
Did someone encounter something similar? Is it expected behavior? Is there
a way to force cef to do it's job. Specs say that C4924 can switch/route
up to 72gbps irrespectively of L2/L3/L4 protocol.
I don't think you want “ip mroute-cache”, at least not on 7600/6500 boxes.
My guess is that by configuring that you're disabling the hardware-based
forwarding & forcing it to software-based forwarding. Get rid of the “ip
mroute-cache” & see if things get better on the 7600.
Are the 4900 boxes doing L3 or just L2? I suspect they'd do much better at
L2 fan-out of multicast than at L3 fan-out. You're probably hitting a pps or
packet replication limit before hitting the bps limit.
________________________________________________________________________
Jay Ford, Network Engineering Group, Information Technology Services
University of Iowa, Iowa City, IA 52242
email: [email protected], phone: 319-335-5555, fax: 319-335-2951
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