The speed that matters is the access speed you have to the websites you use, despite what certain Internet Service Providers try to claim.
To explain, certain ISPs declare that they will provide "up to" a certain speed, such as "up to 21Mbps," yet when a speed test is run on the Internet connection, it is oftentimes around one-third (or even less) of that speed. However, due to the legalese phrase "up to," they are not breaking any service agreements.
I see this as dirty pool, especially when they try to confuse issue further by using a speed test application located on their local web server. There is a very good reason why this test is invalid for measuring the speed of an Internet connection. Think about this: you have your Internet connection there at home hooked up to your computers through a router. Your computers each report that they are connected (to the router) at 100Mbps. You happen to have a speed test application on one of your machines and you test to see what the speed is. Let's say, for the sake of argument, it comes in around 80Mbps. Okay, cool. Now, does that mean that your connection outside of the router will be running at 80Mbps? No, not at all. In fact, the speed outside the router will most definitely be slower, no more than 21Mbps. So, if you are trying to test for access outside the router, your test is invalid since all you did was test the internal network.
This is where ISPs often fall: they think that a speed test application on their local servers, which is within their network, can gauge the speed of the Internet connection for their users. This is not the case. When they state that they will sell an Internet connection of a certain speed, they need to test across the Internet, not only inside where the Internet is not even a consideration. Therefore, the best way to test your true connection speed is to forget the ISP-provided speed tests, no matter how cool they might look, and get to something that is located on the Internet. The one that I prefer to use is located at speakeasy.net/speedtest. All you need to do on that page is click "Start Test" button. This will test both your download speed as well as your upload speed and give you the real numbers. These are the numbers that should matter to you and to your ISP.
What I suggest is taking several different readings at different times of the day to see how the numbers look. Once you have the data, you can consider whether to talk with your ISP and see what they can do to speed up your connection if it seems like the bandwidth you are getting is less than that for which you pay. As a general rule, if you are getting about 70 percent of the promised speed (about 21Mbps if promised 30Mbps), you should grin and bear it. There is always some network overhead and that 30 percent is going to be used up by that (as well as possible line problems that could be within your home and, thus, something not covered by the service agreement with the ISP). If you are getting half or less of your bandwidth on a constant basis, as reflected by the multiple tests, then your ISP should be able to do something about it. Chances are that they will send a technician out to test the circuit and see where the problem lies. This is normally a free service and the fix is free as well as long as it is outside the home (such as a bad cable from the house to the service pole).
If your ISP is not resolving your speed problems to your satisfaction, then you can always change providers. Before considering that, though, give the ISP a chance to implement the changes or find the problem. Not all ISPs are created equal: not all hire the most knowledgeable of technicians or engineers. Because of this, give them a chance to make things right, even though it might take them a few days to a few weeks. Frequently they will hit upon the solution if given enough time. If not, then bail for someone better.
One definite warning sign of a questionable ISP: the ISP keeps trying to blame the service problems on the customer's equipment. One of the local services here kept trying to say to my client that the problem was his modem or router or even his surge protector when the fact was that the ISP had a router that was bad and causing the Internet connection to drop every few minutes. I actually hooked up test equipment and watched the connection drop 80 times in eight hours. The connection was down for a total of 3-1/2 hours during that 8-hour time period. I tested from another location in another part of town so as to insure that it was not isolated to the one neighborhood and found the same problem. At that point, I traced it back to the specific router causing the problem and called to let the ISP know. About two weeks later, they fixed the router. During that time, though, they lost many customers because of their inability to resolve the problem in a timely fashion. While it is possible for the user's equipment to go bad, if the ISP tries to say that every problem is related to the customer's equipment, it is showing a definite lack of interest in resolving the issue as well as a lack of good customer service and, therefore, is a sign that it's time to move on.