We have seen situations under heavy load where a VIP2-40 with an OC3
running at 80% and a Fast Ethernet PA running at 50% have resulted in
severe packet loss and latency. After addressing this with our Cisco reps
(including the Product Manager and Product Engineer for the 7513/VIP
family) they acknowledged the problem and stated:
"We do not recommend putting any other PA into a VIP2-40 if an OC3-PA is
already installed. We have seen adverse performance, in the way of latency
and packet loss, resulting from such a configuration. Customer's choosing
to do so, do so at their own risk".
Whether this is a company wide, advertised position at Cisco is unknown.
During a recent, major launch, our Fast-E PA providing uplink connectivity
to our download servers was located on the same VIP as one of our major NAP
OC3 PA's. At 80% utilization on the Fast E and 50% on the OC3 we started
seeing packet loss and increased latency. When the OC3 gets real busy, the
SARing work consumes most of the VIP's resources. Additional taxation from
other media interfaces pushes the VIP over the edge and it starts dropping
packets and delaying throughput.
It was such a problem for us that Cisco offered special pricing bundle's
for us until the VIP2-50 could come out and handle the aggreagate loads