TCP can be tuned quite a bit as the defaults don't always work well on things like high speed networks.
There are plenty of resources out on the web giving tuning advice:
http://www-didc.lbl.gov/TCP-tuning/linux.htmlhttp://www-128.ibm.com/developerworks/linux/library/l-hisock.html?ca=dgr-lnxw01BoostSocketThe main thing for end nodes is that your TcpWindow needs to be bigger than the sum of your BandwidthDelayProduct.
Your speed is limited by the size of your packets (check your MSS), the loss rate, the RTT and how you use Delayed Acks. For an online calculator see: http://wand.net.nz/perry/max_download.php
2 pages link to TcpTuning:
