For Linux there is the popular Advanced Routing & Traffic Control website, (http://lartc.org/) which contains information on how to implement traffic management on a Linux server. This solution is robust and costs nearly nothing when compared with similar commercial products.
Lastly, if your way cool and have a Cisco router, you can use the "rate-limit" command to control the bandwidth consumed by each IP. If you require further information for this, visit Cisco's site ( www.cisco.com) and perform a search.
This was first published in April 2004