What determines speed

[Seymour Butts]

Our service provider advise us that Internet Speed can be broken down into 3 distinct categories (and without trying to teach you how to suck eggs),
These are;
Download speed (the speed a user can retrieve something from the Internet),
Upload speed (the speed a user can send something to a remote location on the Internet) and
Latency (the lag or length of time that occurs between each point during information transfer).

Download and upload speeds are measured in the number of bits (or bytes) per second transferred, while latency is measure in milliseconds (or thousandths of a second). To provide an extremely simplistic explanation, think of this measurement as comparable to a truck payload, such that a big truck can carry more than an economy pickup truck.

But what really determines Internet speed? I can assume it's a variety of things, but how much does componentry play in the overall scheme of things?.

I have a small network at home there are only 4 PC's networks and I've noticed that if all 4 are working it only requires one to be downloading a big movie file and the whole network starts to lag and get slower and slower, even the transfer of files from one PC to another can slow down.

From this I do wonder how larger networks survive.

On our own corporate network (7 sites, each with 10 laptops - None better than a dual core. Each site has it's own DC and FS servers, each site has a dedicated ADSL1 connection) we use proprietary software for data recording yet when our users operate and do their paperwork, usually between 9.30 and 10.30am and 2.30 and 4.00pm daily, latency times per site can rise from a standard 50 - 75ms to over 700ms, indeed I've seen latency times over 1500ms

Needless to say the higher the latency the slower the internet

So, as a general question "How can we speed things up" ?

[autotuner]

I have a small network at home there are only 4 PC's networks and I've noticed that if all 4 are working it only requires one to be downloading a big movie file and the whole network starts to lag and get slower and slower, even the transfer of files from one PC to another can slow down.

The switch itself will have a 'bandwidth', the speed at which the backplane can transfer. Also the architecture of the switch, Store and Forward or Cut Through will affect sustained transfer rates.

From this I do wonder how larger networks survive.

Large networks use careful planning, continual monitoring and QOS / bandwidth control to keep things under control.
For instance, an application that moves big amounts of data may not run on the actual PC, instead it may be a Terminal server session back to a powerful machine in the data centre so that all that is crossing the link is screen and mouse/keyboard data.
There are heaps of ways to improve performance without throwing bandwidth at it, it just requires analysis of what is actually happening.