C6800-32P10G oversubscription

[Ralf Kleineisel]

I have a question regarding a C6800-32P10G module in a 6509-E chassis with Sup-2T.

The module can operate in 4:1 oversubscription mode or 2:1 oversubscribed performance mode because the chassis backplane bandwidth is only 80 Gbps.

Does this oversubscription also affect traffic that is switched within the module by the DFC?

Or can the 32 ports use line rate speed as long as the traffic does not leave the module and only the traffic going to a different line card is oversubscribed / limited to 80 Gbps?

[Joseph W. Doherty]

Traffic to/from the rest of the chassis is (I recall) via two 40 Gbps fabric channels (for a 65xx-E with Sup-2T).  I.e. half the ports use one fabric channel, the other half the other fabric channel.  (To obtain the 80 Gbps, you need to balance traffic across both fabric channels.)

I don't recall what the architecture supports for traffic between ports on the same C6800-32P10G line card.

BTW, I also recall (?) many DFCs cannot guarantee wire-rate for full fabric bandwidth if using minimum sized (64 byte) Ethernet packets.

The 32 port card has two DFC4Es (one per half the cards ports?), each rated at 60 Mpps (IPv4).  60 Mpps guarantees about 40 Gbps (for minimum sized Ethernet packets).