Router as a weak WAN link?

Our ISP advertises 1.5M downstream and 256K upstream. We have a four-port Linksys router and have four PCs at home using the Internet. The FTP server software displays the throughput that each uses, as well as the total server numbers (we limit the number of simultaneous users to seven). We never see the total server number reach 64K. I’m guessing the 256K upload limit is divided by four (because of the four-port router). Are we being limited by the router?

The router contributes to the delay but is probably not the limiting factor. DSL speeds usually refer to bits per second, so a 256K upstream connection means 256K bit/sec. This translates to 32K bytes per second.

Processor limitations, network congestion, buffering inefficiencies, transmission errors and traffic loads all contribute to reducing throughput. Throughput is determined by the speed of the link and the propagation delay. When congestion or errors occur, TCP hosts slow down their transmissions.

Adjusting the TCP window size to match the capacity of the pipe can improve performance. Go to this page for more information on manually adjusting the TCP window size for Windows and Macintosh systems.