If you want to limit your download and upload speeds use one of the following tools
1) Wondershaper
2) Trickle
An easy to use traffic shaping script that provides these improvements:
* Low latency for interactive traffic (and pings) at all times
* Allow websurfing at reasonable speeds while uploading / downloading
* Make sure uploads don’t hurt downloads
* Make sure downloads don’t hurt uploads
It does this by:
* Limiting upload speed slightly, to eliminate queues
* Limiting download speed, while allowing bursts, to eliminate queues
* Interactive traffic skips the queue
* ACKs and tiny packets skip the queue
Configuring the wondershaper requires you to accurately and precisely determine your consistent upload and download speeds.
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http://www.ubuntugeek.com/use-bandwidth-shapers-wondershaper-or-trickle-...