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Getting technical: What are T1 and T3 lines anyway?

t1 t3 linesIn the world of the internet, and computer networking in general, there are often terms we just throw around. T1 and T3 are just two designed to baffle the uninitiated. So what do these deceivingly simple terms mean? Read on and find out.

The shortest description is that they are both cables (or lines) used to transmit voice and data between two points. The biggest difference between them is in how much data they each can carry.

A T1 is capable of carrying 1.544 Mbps while a T3 line supports 44.736 Mbps. ISPs use these lines as backbones to their networks and to connect to the Internet at their points of presence. Since the average UK broadband speed is 18.7 Mbps, you might guess that there are a lot more T3s out there than T1s. But it doesn’t have to work that way.

You see a T3 line is just 28 T1s bundled together (it’s a little more complicated, but for our purposes we’ll leave it at that). So an ISP could actually have many, many T1s rather than the equivalent T3s. It’s also possible to lease T1s or T3s if your business needs a dedicated amount of bandwidth. Dedicated is the keyword there. Because while the average broadband speed may be over 18 Mbps, it can often slow to much less than that due to contention. That’s when your neighbourhood kids get home and all crank up their computer to watch YouTube or play online video games. Generally speaking, ISP resources are shared unless you spend a ton of money for a dedicated line.

How much? Leased lines can cost hundreds to thousands of pounds per month depending on how much you need. If you’re a company that is producing a lot of high quality broadcast video for streaming it’s certainly worth the cost because you know you’ll have the bandwidth every hour of the day. Of course there are other companies like high volume call centres could also use that kind of dedicated bandwidth.

In reality though, it doesn’t matter if you get the bandwidth you need from T1s, T3s, or even a combination. It will all be transparent to you, except for the pricing.

Oliver Burt

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