bridge query

[suvashrestha at wlink.com.np]

Hello....

I am using TCP sockets to measure packet transfer. And I am also not
looking to optimise the link. I just want to know if this is the usual
behaviour of the freeBSD TCP or bridge when we apply delay and packet
loss.

The throughtput falls from around 8 Mbps (8000 Kbps) to just 80 Kbps.
This is very significant.

Thanks
suva



How are you measuring packet transfer (single TCP socket, multiple TCP
sockets or UDP) and what were you expecting?


For a TCP connection, the window size needs to be able to handle at
least 1 RTT (0.5 second in this case) of data.  This translates to a
total of 5Mb (~640KB) outstanding data to get 10Mbps throughput.  With
only a single cnnection, you would need a 640KB window size - which is
far larger (an order of magnitude or so) than typical.

TCP is also designed to work on a mostly lossless link.  I am not sure
how much a 5% packet loss will affect it but I would expect it to be
significant.  I'm not sure how to optimise throughput in this
situation.

Peter Jeremy