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6500/sup720 performance with classic modules.

I'm trying to get an better understanding of the performance hit that one might see in a 6513 that has both fabric and non-fabric modules installed. I have reviewed the description of compact vs truncated mode:

•Compact mode—Operational mode when all modules in the system are CEF256 or CEF720 (no non-fabric-enabled modules can be present for this mode). In this mode, CEF256/CEF720 modules send a "compact" 32-byte header for each frame to the supervisor engine over the switching bus. Once a forwarding decision is made, CEF256/CEF720 modules send the entire frame through the switch fabric to the egress module.

•Truncated mode—Operational mode when at least one non-fabric-enabled module is present in the system. In this mode, CEF256/CEF720 modules send the first 64 bytes of each frame to the supervisor engine over the switching bus. Once a forwarding decision is made, CEF256/CEF720 modules send the entire frame through the switch fabric to the egress module.

Does this mean that the first 32 or 64 bytes of "EVERY" frame is sent to the supervisor or just the "FIRST" frame of each session or flow? If its the first frame I would not think the perfromance hit is that big of a deal. If its every frame that would be a problem.

The customer is asking me to quantify the performance hit they might take in truncated mode. Any insights would be helpful.

2 REPLIES

Re: 6500/sup720 performance with classic modules.

The performance "hit" it's referring to is when there is a legacy line card in the chassis with SFM capable line card is that the line cards will not fully utilized the "fabric" b/w which is 256 Gbps depending if we are talking about SFM or Sup720. With truncated mode since the legacy does not use the fabric channel the switching will fall back to 32 Gbps which is what the 6500 can do before SFM or Sup720.

New Member

Re: 6500/sup720 performance with classic modules.

"If its every frame that would be a problem"

I don't think it's problem because module is CEF256/CEF720. If module is dCEF256/dCEF720, I think that it is problem if "its every frame ".

just from my opinion.

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