Hi, I just had DSL installed and was told to adjust the DefaultReceiveWindow in the windows registry. This dramatically improved performance. To be clear, my understanding of the setting is this. It defines the amount of data which can be sent before an ACK must be received.
The logic is the overhead of ACKs becomes tremendous as the link speeds up. I believe the default is 8KB. That is to say only 8KB can be sent before an ACK must be received. With a slow link, this worked great. Missing ACK - retransmit only 8KB. With faster links, one is constantly waiting for ACKs. My question regards the setting for Linux. What is the default size? Where is it defined? Please keep in mind, latency is the critical factor here. When an ACK takes 200ms to be received, it is very detrimental to wait for ACKs. Even fast lines often suffer this latency. Of course, Bandwidth and Latency are separate issues. Bandwidth is reduced as a function of latency due to handshaking nature of the protocol. This also implies LANs would suffer as much as the latency should be very low. Side Issue: This is what led to dramatic performance increases when sliding window protocols such as zmodem emerged. I wonder if TCP/IP uses any sliding window technology. Probably not since the parameters of the exchange are not rigidly defined as in zmodem. I don't believe it does use sliding window but would love to hear if it does or will. Regards, Paul -- Paul McHale Work: 937-320-5495 Double E Solutions Mobile: 937-371-2828 1435 Edenwood Dr Fax: 413-215-3232 Beavercreek, Ohio 45434 --
