Hi ,

I am one of the members who is managing a Wide Area Network . The
Backbone speed of
this network is around 1.4 gbps and the links that connect to
this backbone are of 10 mpbs
and 100mpbs speed .
I am managing a LAN which connects to the above WAN with a 10mbs
link. Some other
sites are connected with 100 mbps link . Now to gain better
performance , some TCP
tuning had to be done at the Host level. So , I was trying to
calculate the size of the TCP
window (Bandwidth Delay Product ) which is given by

BDP = bandwidth * round trip time.

My Doubt is regarding this formula . For bandwidth , which bandwidth
I should consider, the
speed of host's NIC (100 mbps), or the speed of the link (10 mbps )
which connects us
to the WAN or the speed of the Backbone (1.4 gbps).

And for Round Trip Time , I communicate with different links with
different RTT . e.g With
one link the RTT is 26.678 ms and with another is 67.786 mps. So
which RTT should I
consider.

Please somebody help me out in understanding the formula correctly.