RWIN (TCP Receive Window) is the amount of data that your computer can accept without acknowledging the sender. If sender has not received acknowledgement for the first packet it sent, it will stop and wait and if this wait exceeds a certain limit, it may even retransmit. This is how TCP achieves reliable data transfer.

How to find your RWIN:

1) Open up a DOS Prompt box:
Start>Run>command

2) Type: ping -l #### dslreports.com
#### is your MSS. (MSS = MTU - 40)

Example Screenshot

Take your average large packet ping, multiply by 1.5, multiply that by your proposed advertised speed, and divide that value by 8. You now have your raw RWIN.

Example: 450ms average latency (x 1.5) with 53Kbps available downstream bandwidth:

450 x 1.5 = 675. 675 x 53kbps = 35775. 35775/8 = 4472 (RWIN).

3) To change the RWIN:

•Download DrTCP to your Desktop.•Change the TCP Receive Window field to whatever value you got.•Save, Exit, then reboot your PC.

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by redxii edited by TravisB
last modified: 2006-11-02 01:45:55