How Fast Can You Go?

I've been following the CalTech and CERN groups responsible for achieving what they claim is the "latest Land Speed Record" of 5.4 Gbps and a claimed throughput of 6.25 Gbps over an average period of 10 minutes, according to the announcement to the Internet 2 newslist on February 24th.

Of course, what does this mean? They claim that "best achieved throughput with Linux is ~5.8Gbps in point to point and 7.2Gbps in single to many configuration". They claim they're melting down the "hardware" at 6.6 Gbps. Is this true?

Here's what Mr. Cluster himself, Jim Gray, says (thank you): "we are running from Pasadena to Cern at 6.6 Gbps (800MBps) and not saturating the cpu (we are melting the NIC)." So he does confirm that it's not the processor.

Hmm, not processor but NIC? How can you "melt down" something as simple as a physical link (layer 1), or a CRC (layer 2) or even the IP processing (layer 3)? They're all pretty straightforward. You only run into problems when you hit stack for TCP, and that's done for TOE's in the processor.

Well, sounds like the limit must be the bus - getting it in and out in the first place. But why are they being so obscure about it? Only AMD and Intel can deal with the real issue - putting it on the processor itself. But then, maybe you'll get back to that fundamental problem of the stack latency processing again. And wouldn't that be embarrassing if all these new approaches still got you caught up in stack?

Kind of makes me wonder - don't you?