Helping people with computers... one answer at a time.

ISPs control bandwidth with very extensive routers. The equipment owned by the ISP keeps track of exactly what data is being sent to and from your internet connection.

How do ISPs control the speed that each customer receives with so many different plans and charges for each level of increase? I just wondered how they know which household gets how many megabytes technically speaking? My service is with a major cable/internet provider (not DSL, etc.) and no complaints with speed, only with the prices that they charge.

In this excerpt from Answercast #78, I look at the ways that ISPs can limit and track the internet connections that they sell.

ISPs control bandwidth

Well, ultimately, they end up using equipment that's not too dissimilar probably from equipment that you have yourself.

Basically what it boils down to is that on the other side of your internet connection is a router. Now, it's not like the router that you've got; a small home device that maybe cost you somewhere between $50 or $100. No, these are multiple thousands of dollars of different kinds of high-end routers that are specifically designed for this kind of activity.

Throttling speed

Among the many, many different things that these routers can do, is they can throttle the amount of speed that you are allowed to get.

In other words, if your speed is limited to say 10 MB per second, then that router will be configured to send data to your connection at no faster than that.

Now, in many cases, it's actually the connection itself that limits the speed. Particularly with services like DSL, where the actual signal that's used is limited in some fashion to how much data it can provide.

However, even in cases where the signal itself is strong enough (or potentially fast enough) to contain more bits per second than you may be receiving, it will still be the router at the other end that is throttling or controlling the data that you receive.

Monitoring connections

The same is true for monitoring and keeping an eye on what it is you visit, where you go, what you are allowed to do, and what services your ISP is actually providing you. It's the router at the end of your connection, possibly in conjunction with other equipment owned by the ISP, that simply keeps track of exactly what data it is that's being sent to and from your internet connection.

(Transcript lightly edited for readability.)

Article C6126 - December 12, 2012 « »

Leo Leo A. Notenboom has been playing with computers since he was required to take a programming class in 1976. An 18 year career as a programmer at Microsoft soon followed. After "retiring" in 2001, Leo started Ask Leo! in 2003 as a place for answers to common computer and technical questions. More about Leo.

Not what you needed?

Comments on this entry are closed.

If you have a question, start by using the search box up at the top of the page - there's a very good chance that your question has already been answered on Ask Leo!.

If you don't find your answer, head out to to ask your question.