We have been performing some latency tests across Cat6509 switches with SUP720-3B and 67xx blades and wondered what the expected improvement (if any) should be after we installed DFC modules on the blades. We used the DFC-3B modules, so that they matched the supervisor hardware.
During the testing, we noted that the installation of a DFC-3B on each 67xx blade provided no noticeable latency improvement, however, at this stage no load is being placed on the 6509.
Without the DFC modules, I expected the traffic to have the following flow. This is a layer III traffic test within the same 6509:
Ethernet Port--(Switch-Fabric)--(SUP720-Central FDB)--Switch-Fabric)--Ethernet Port
This is with the clients being on the same 67xx blade.
With a DFC installed, I expected:
Ethernet Port--(DFC Module)--Ethernet Port
I guess that there would be an initial flow to allow the switch to confirm the destination of the packet flow, but after that it would be processed by the DFC.
No non-67xx blades are installed in the cat6509.
I may have this completely wrong and the DFC will come into play for switching throughput, rather than improving latency.
Any feedback on this would be appreciated.