On Fri, Apr 11, 2014 at 3:10 AM, Varun Sharma <vsdssd@gmail.com> wrote:

Hi,

if we off tso (tcp segmentation offload) on sending side , TCP Bidirectional test sending throughput decrease as compare to TCP Unidirectional test sending throughput .

whereas if we on tso(tcp segmentation offload) on sending side , both test give almost same sending throughput result.

is anyone know how tso(tcp segmentation offload) effect TCP Bidirectional sending throughput ?

i am using iperf-2.0.5 for this case.

There are couple of things here.

1. Depending on the NIC, it could potentially have hardware offload in the hardware. So offing TSO might not off it.

2. There is Linux kernel offload for receive, so there might be kernel offload for send also

3. Different cards deal with offloading differently, with very different result

4. If TSO is actually off, it might mean that eventually acks from remote side are delayed filling its buffers

So this is very card, kernel version dependent.