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Monday, June 1, 2009

Why is my internet connection slow?

In our internet connection, we use different mediums or cable types. The most common is the cat5 UTP cable which we commonly use in our PC's for DSL or broadband connections. Cat 5 can have 10mbps (megabit/second) to 1Gbps (gigabit/second) speed depending on the ethernet type used. These are the carrying capacity of the medium or cable but bandwidth largely depends on your provider or ISP (Internet Service Provider). ISP often offers different subscription plans for example a 1 mbps subscription or 2 mbps. Our often question is why is my internet much slower than it shoud be?To answer that question we'll have to discuss "Bandwidth", "Throughput" and "Goodput".
  • Bandwidth - Is considered as the theoritical speed. It is the capacity of a medium to carry data in a given amount of time. The standard measure of bandwidth is in bps or bits per second. As technologies have improved, bandwidth is more commonly associated with kbps or kilobits per second or mbps or megabit per second.
  • Throughput - Is the actual transfer rate of data over the medium in a period of time. Bandwidth is the capacity for moving data, but attaining that capacity is rare because of factors such as interference and errors. Many factors influence throughput, including: the amount of traffic, the type of traffic, and the number of network devices encountered in transmission.
  • Goodput - Is the transfer rate of actual usable data bits. Goodput is the data throughput less the protocol overhead bits, error corrections, and retransmission requests. The difference between between goodput and throughput can vary greatly depending on the quality of network connections and devices.

So having a bandwidth of 1 mbps is just theoritical, with interference in the cables and errors in collision, it is rarely attained. What we must be looking for is the Goodput which is the actual speed. If you are browsing a webpage for example, you are sending a request to the webserver hosting the webpage. The request and reply comes with an address so that it can find its way to your computer, it also has some error control so that a part of it is missing can be retransmitted. Goodput is minus all of this termed as "overhead". Goodput is the actual data itself or in our example, the actual webpage. If your wondering why your 2 mbps is as slow as 256 kbps then this may be the answer. It depends greatly on the quality your ISP deployed its network. If it is poorly managed and configured, most of your bandwidth may be consumed by errors.