SPelham

Hi,

We currently have a site to site VPN setup between our offices which is used for general network access (opening/transferring files, email, etc etc ).
We now have a load more users and the company has been looking at upgrading the bandwidth to a 100Mb link, due to the line constantly maxing out.
However a couple of network guys have told me that it won't help at all. The reason they gave me was that, Even with a 100Mbit/s link, the latency to our other site (about 100ms), and the fact that Windoze uses an 8KB TCP window size, means that you actually only get about 640Kbit/s raw throughput. Then add the fact that it's shoddy CIFS and that just drops through the floor...
So we have now been looking at using some sort of packet shaping hardware, but can anyone confirm that the info I have above is correct.

TIA :-)

unfeasablylargegonads

iTrader: (3)

Yes, this is partaily true, this is refered to as the bandwidth delay product.

If your link has both high latency and some packet loss you are screwed. If however it has just high latency and exceptionaly low or no packet loss then there are tweeks you can make to most OS TCP/IP stacks that can greatly increase the throughput without the need for additional hardware, including increasing the window size you mention.

Have a look at Enabling High Performance Data Transfers [PSC] for easy how to's.

Iperf is a great tool for testing throughput with different window sizes etc and its free : NLANR/DAST : Iperf 1.7.0 - The TCP/UDP Bandwidth Measurement Tool

Its also worth pointing out that it only limits indervidual conversations so although only one TCP session may be limited, multiple TCP sessions or other non connection orentatied traffic can happlily use the full 100Mbs you will have (excluding other factors).