I'm using boto to upload and download files to S3 & Glacier. 
How can I ratelimit/throttle the uploading and downloading speeds?
The simplest would be to use traffic shaping tools under linux, like tc.  These tools let you control bandwidth and even simulate network packet loss or even long distance communication issues.   Easy to write a python script to control the port behavior via a shell.
How to throttle S3 & Glacier upload/download speeds with boto?