How to set packet size for iperf in TCP

Sud_paddy · 12-19-2014, 01:06 AM

Can any on tell me How to set packet size for iperf in TCP .
There is opiton for window size which set doubled you requsted , is Window size is same as packet size ....

Ser Olmy · 12-19-2014, 07:01 PM

No, it's not. The window size determines how many packets a host can buffer.

Unlike UDP, TCP performs automatic segmentation of the data stream. Unless one can somehow specify a the segment size manually, TCP will attempt to send packets that are as large as the interface Maximum Transmission Unit setting will allow.

In iperf (well, in iperf3 at least), you can override this with the --set-mss option.

Sud_paddy · 12-19-2014, 11:25 PM

So there is no mechanism to set TCP packet size??

Ser Olmy · 12-20-2014, 07:32 AM

As I said, what you're looking for is a way to control the segment size, and the --set-mss option should do that. It's an option that's available in the version of iperf I'm using, but if yours doesn't support it, you're probably out of luck.

You could of course change the MTU of the outgoing interface, as that would affect all outgoing traffic, including packets generated by iperf. Unfortunately, having different MTU settings on hosts in the same network could cause other issues.