[c-nsp] CEF and multicast on a 3750

[Phil Mayers]

On 26/06/12 16:07, 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

It might be interesting to capture the MPEG data using a "real" tap i.e. 
physical fibre tap, proper copper tap, and look at the inter-packet 
spacing *before* it goes into the switch.

My guess is that the MPEG codec, extremely expensive or not, is emitting 
all the data for a P/I frame as a single burst of line-rate or near 
line-rate packets.

When >1 of these bursts converge at an output port, you will get loss on 
a 3750 because the buffers are tiny and the offered load will exceed 
line rate.