lowpri - RTO for unidirectional reciever
Subsystems (2)
Folks -
I was going through old email to do a status report and was reminded of a discussion in netperf-talk that might be of interest to people here since it involved a Linux receiver:
http://www.netperf.org/pipermail/netperf-talk/2008-November/000478.html
A Mac OSX bug was found/presumed, but there was an interesting behaviour on the linux receiver side as well - the rtx of the ignored FIN happened after what IIRC is the initial RTO. It suggested that the ACK of the SYN|ACK didn't update the rtt estimate or if it did, didn't so so very much. Bug? Feature? No idea, but food for thought.
rick jones
David Miller
maintainerFrom: Rick Jones <[email protected]>
Date: Mon, 08 Dec 2008 18:02:01 -0800
Quoted 6 lines
A Mac OSX bug was found/presumed, but there was an interesting behaviour on the linux receiver side as well - the rtx of the ignored FIN happened after what IIRC is the initial RTO. It suggested that the ACK of the SYN|ACK didn't update the rtt estimate or if it did, didn't so so very much. Bug? Feature? No idea, but food for thought.
We should not use the SYN|ACK for RTT estimates.
It's a bug, and in fact we used to, but I fixed that long ago.
Since there is no data in the packet, and it's therefore very small compared to real data bearing packets, the RTT measured might be artificially small and not really representative.
Quoted 8 lines · David Miller
We should not use the SYN|ACK for RTT estimates.
It's a bug, and in fact we used to, but I fixed that long ago.
Since there is no data in the packet, and it's therefore very small compared to real data bearing packets, the RTT measured might be artificially small and not really representative.
A miracle occurs going from zero bytes of payload but several bytes of TCP options (scale and MSS) to having one byte of payload and no bytes of options? (Timestamp options remaining the same in both cases)
rick jones
David Miller
maintainerFrom: Rick Jones <[email protected]>
Date: Tue, 09 Dec 2008 11:25:19 -0800
Quoted 4 lines
A miracle occurs going from zero bytes of payload but several bytes of TCP options (scale and MSS) to having one byte of payload and no bytes of options? (Timestamp options remaining the same in both cases)
All it takes is ~40 bytes on an extremely slow link.