I'm a C/C++ computer programmer turned IT support guy working for a public library. My day is usually spent helping random grandparents learn how to use email, so my networking knowledge is limited to what I can glean from google.

Here's the situation. We have a public library with 20 PCs on a LAN and also public wifi access. Previously we were running all of this on 1 ADSL connection and people complained about low speeds.

We hired a networking company to set up a Cisco dual-WAN router for us, and purchased an additional ADSL connection. The intention was to give the LAN PCs a guaranteed amount of bandwidth each, and then let the wifi users split the rest.

The results were far worse than what we expected, and all we got from the company was excuses and they've since washed their hands of us. During busy periods, net performance on the LAN PCs are so poor that attaching files to gmail etc often times out and fails - far from the "guaranteed amount of bandwidth each" that we hope for! Sometimes it feels like performance is worse than before when we had 1 ADSL link and an unconfigured router?

Anyways, surely this is a problem encountered a million times over across the world? (Sharing internet across many users effectively.) What are standard solutions for something like this? I admit to not even knowing the right jargon to google for (load balancing?)

I'd appreciate any links to resources/guides that might help me get a better understanding of the problem/solutions, and perhaps some stories of your own experience in solving similar problems. This will help us evaluate and negotiate with network consultants in the future.

If its relevant, our router config contains a section "policy-map" with "bandwidth percent" for each class of user (LAN, wifi), and "fair queue".