Assume an office of people, they want to limit HTTP downloads to a max of 40% bandwidth of their internet connection speed so that it doesn't block other traffic.

We say "it's not supported in your firewall", and they say the inevitable line "we used to be able to do it with our Netgear/DLink/DrayTek".

Thinking about it, a download is like this:

HTTP GET request
Server sends file data as TCP packets
Client acknowledges receipt of TCP packets
Repeat until download finished.

The speed is determined by how fast the server sends data to you, and how fast you acknowledge it.

So, to limit download speed, you have two choices:

1) Instruct the server to send data to you more slowly - and I don't think there's any protocol feature to request that in TCP or HTTP.

2) Acknowledge packets more slowly by limiting your upload speed, and also ruin your upload speed.

How do devices do this limiting? Is there a standard way?