Luckily, buffering issues are easy to check. Look for output drops in
"show interface" as well as "sh plat port-asic stats drop gi x/y/z"
Don't forget, as some others have touched on, state changes. If TCNs
occur, we fast-age mac addresses - including IGMP-learned.
Who is the mrouter/querier? Does this device always have igmp/mrouter
state? IGMP join/leave activity should be investigated.
It's an important distinction to see if you are missing traffic on all
receivers, or a subset.
Regards,
John Gill
cisco
On 6/26/12 11:31 AM, Gert Doering wrote:
Hi,
On Tue, Jun 26, 2012 at 09:07:32AM -0600, John Neiberger wrote:
These are extremely expensive real-time video encoders taking in
baseband video and outputting multicast MPEG at a constant bit rate
for customer-facing video feeds. Any pauses would be unacceptable, as
are dropped packets, unfortunately for this site. hehe
Bit rate is never "constant". It's always "constant if averaged over
a certain time window".
If you send 20 packets per second, and send them in bursts of 20 packets
and then 0.99s of silence, you are *still* sending a "constant bit rate
of 20 packets per second", if averaged over a time window of 5 seconds.
Unless you are really sure (by having done a wireshark / tcpdump dump
with time stamps directly on the encoder port, with no other gear in
between) that packets are space out evenly, with only one packet ever
sent per burst, and then a delay that's the same for every packet, do
not assume that "constant bit rate" is really non-bursty at the microsecond
level.
We've learned this the hard way with our audio streaming setup - some
streaming server software is quite good at pacing the packets (windows
media server), some is particularily bursty (icecast, if I remember
right). Of course I do not know the application that you're using, just
trying to break some "it can not be this!" assumptions.
I'm engaging our Cisco team on this to have them investigate queueing
and buffer issues. I don't think they've looked at that yet.
"We do not have buffer issues in these switches! They do not HAVE
enough buffers to have issues with them!"
gert
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