Thursday, June 21, 2007

Speed vs Bandwidth.....The Age Old Question

It's easy to get bandwidth and speed confused.

In simple terms, the speed "depends" on the bandwidth.

Bandwidth is simply the "amount" of data that can be transmitted across a digital circuit within a specific amount of time. It's measured in bits per second(bps). Therefore, the higher the bandwidth, the "faster" (there's where your reference to "speed" comes in) that your data can be transferred.

Here's an example:

An ISDN BRI provides up to 128kbps of bandwidth (2 x 64kb for voice) or a "combined" 128kb for data.

Customer A wants a 128kbps BRI for their VTC circuit.

Customer B wants three separate 128kbps BRIs for their VTC enabling them a combined (bonded) bandwidth of 384kbps for their VTC.

Since customer B's circuit has 3 times the bandwidth, their data can be transferred at 3 times the "speed" as customer A.

There ya go.....question answered.

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7 Comments:

Blogger Alexander said...

Acutally Customer B doesn't go any "faster"... He can just transfer more data at that speed.

Hypothetically, let's say you're transfering a file at it's going at 128kbps, if you start to transfer another file it will compete for bandwidth and slow you down. If you added another 128kpbs ISDN line your 1 file will still go at 128kpbs, but now you can transfer the 2 files at 128kbps without it slowing down.

Think of it like a freeway with a 65mph speed limit. You can add more lanes to the freeway to handle more cars, but there is still a 65mph speed limit.

8:46 PM  
Anonymous Kyle said...

Alexander, If you can transfer more data in the same amount of time. Wouldn't you say that is faster?

1:33 PM  
Blogger Patty said...

Kyle, Alexander is correct. Having more bandwidth "results in" virtually faster speed, but, if we look at the speed the first file is being transmitted, having more bandwidth doesn't really make this first transmission "faster".

Increasing bandwidth will allow more files to travel at the same time at potentially same speed, as long as we have enough bandwidth. but transferring only one file on high bandwidth link doesn't result in increased transfer rate.

8:21 AM  
Blogger Arthur said...

Kyle, look at it this way. If you have 1 car going from point A to point B on the aforementioned 4 lane, 65mph highway, it will get there no faster than the front car of 1000 cars going down the same highway. Likewise, if it were expanded to 8 lanes, the front car of the 1000, or the car by itself get there at the same time, so "speed" is not effected.

Basically, it is only "faster" at transporting larger volumes. So in reality, it is not "faster", but only more efficient.

11:28 AM  
Anonymous Anonymous said...

Ah, but what if you have too many cars to go down a single lane at once - result? - traffic Jam and a slowing of traffic. It would be nice at that point to have a second or third lane so that the cars could actually get up to speed.
So yes, bandwidth does effect speed - it allows the data to proceed without conflict. But speed can also be negatively be effected by lack of bandwidth.

11:56 AM  
Anonymous Anonymous said...

Perception is everything. Talking about the actual "speed" at 2/3 of light, you are not going to get faster than that, but what is going to make you think that is slow? The Bandwidth allows more traffic to travel at that speed, which perception wise to the customer/consumer is how fast can my web page get to me. If you think of a file as a single continuous stream of data, a single packet, then that train is going to move slow on a single lane of the highway. If that file is chopped up into several packets and then all sent at once, the perception is that it arrives that many times faster. While the additional complications of added security/routing/etc overhead of each packet increases the amount of data, the Bandwidth in the end is the perceptual determination of "speed" in the data world.

11:59 AM  
Anonymous Anonymous said...

I think of bandwidth as the size of a pipe carrying water or data if you prefer. The water will travel just as fast in a small pipe as a large pipe only the broader the pipe the more information is being transferred a the same speed. So speed is one thing and volume is another. Id rather have a slower speed and greater bandwidth than a faster speed with less bandwidth. I may be wrong who knows.

10:19 PM  

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