RE: 923Mbits/s across the ocean

The jumbo frames effectively increase the congestion avoidance additive increase of the congestion avoidance phase of TCP by a factor of 6. Thus after a congestion event, that reduces the window by a factor of 2, one can recover 6 times as fast. This is very important on large RTT fast links where the recovery rate(for TCP/Reno) goes as the MTU/RTT^2. This can be seen in some of the graphs at: or more fully at:

We saw little congestion related packet loss on the testbed. With big windows SACK becomes increasingly important so one does not have recover a large fraction of the window for a single packet.

Once one gets onto networks where one is really sharing the bandwidth with others performance drops off rapidly (see for example the measuremsnts at and compare them with those at

One of the next things we want to look at next is how the various new TCP stacks work on production Academic & Research Networks (e.g. from Internet2, ESnet, GEANT, ...) with lots of other competing traffic.