[c-nsp] Nexus 7k F2E line cards vs F3 vs M3

[Curtis Piehler]

As it appears the F2E line cards are terrible at dequeuing packets quick
enough across a port-channeled application.  There was an incident where
traffic got pinned to one link from the same source/destination causing
input discards due to back pressure from VoQ drops/congestion on some
port-channel egress ports.  The issue went away on its own and
correlated to a sudden increase in traffic (sessions per second)  between a
single source and destination.  All ingress and egress ports are
port-channeled with at least two members in them.

Looking at the F3 line cards they have about 7k more egress queue per port
and double the amount of egress queue per SOC (512k vs 256k).  Granted the
F3 lines are a huge cost increase would they be an appropriate upgrade to
handle this type of burst traffic?

I see the Nexus 7k platform has M3 line cards which cost 3x-4x F3 line
cards.  What is typically used in data center environments these days in
Nexus 7k switches that handle voice applications and such?