How to test and optimize internet connection

Applicability: Windows 2000, Windows XP
If you suspect having issues with your Internet connection, check the speed at the following site:
http://www.my-speedtest.com/speedtest.htm
and transfer efficiency at:
http://www.dslreports.com/tweaks
Your internet speed should be as advertised by your provider (or very close to it) and transfer efficiency of no less than 99% If you do have problems see instructions below.
The following freewares will be used:
a. TCP Optimizer from http://www.speedguide.net/downloads.php
b. DrTCP from http://www.dslreports.com/drtcp
(these programs do not require "installation", you can simply run/move/delete the program anytime you like)
1. Use TCP Optimizer to find latency and largest MTU
2. Calculate approximate RWIN (Tcp Receive Window) as follows:
Rwin approximate = 0.1875 x DS x L ,
where DS-your advertised download speed at kbits per second, and L- average latency in ms.
3. Calculate MSS as follows:
MSS=MTU-40
4. Divide Rwin by MSS and round the result to closest even number N:
N (even)=round(Rwin/MSS)
5. Calculate final Rwin as follows:
Rwin=N(even) x MSS
6. use DrTCP to set Rwin and MTU (pay attention to choose the right network adapter card). If RWIN is greater than 65535, set Windows Scaling to "yes". If you use router then set MTU in router.
7. Reboot
8. Go to http://www.dslreports.com/tweaks and check connection. You should get transfer efficiency of no less than 99%
9. Go to http://www.my-speedtest.com/speedtest.htm and check your down and up speeds. You should get your advertised speeds or very close values.

Example: Your advertised speed is 2500, average latency is 200ms, and maximum MTU=1400.
MSS=1400-40=1360
Approximate value of RWIN should be:
Rwin approximate=0.1875 x 2500 x 200=93750
N(even)= round(93750/1360)=round(68.9338)=70
Rwin =70 x 1360=95200.
As Rwin is greater than 65535 set windows scaling to "yes"
Good luck and happy surfing