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Understanding Broadband Connection Speeds and how they affect Remote Access to your Office Network

With the revolution in Internet access that has happened in the UK over the last 5 years you might think we're living in a Broadband paradise.

While Broadband is cheap and fast for most activities, it does have limitations that makes it unsuitable for some business activities.
I've seen companies enable VPN access to their office network for home workers only to find it was too slow to be usable.

The good news is that the dream of remotely connecting to your office network to access email, files and to work with databases, from home and when travelling is possible, and won't cost a fortune, as long as you choose the right type of Broadband, the right method of remote access and optimise the way you use your network for remote access.

The true speed of Broadband can be very different from the "headline" speed.
8 mbps is now the standard connection speed in the UK.
With an 8 mbps circuit, the actual connection speed that is possible decreases the further your home or office is away from the nearest telephone exchange.
The fastest actual connection speed I've seen is 4 mbps and in many cases it's nearer to
2 mbps.

After monitoring your circuit's performance, your ISP sets a speed limit on it because it's inefficient to keep trying to connect at a speed that produces a high error rate.
This means that if your connection has been capped at 3 mbps then there won't be good days when it performs better as it will never try.

Contention

Your "8 mbps" is shared with other Broadband subscribers at your ISP.
For home users it's shared among 50 customers and for business users it's shared among 20 or maybe 10 customers.
This process is called contention and, if other "contenders" are making heavy use of the Internet, your connection speed can slow right down.
It's now noticeable that Broadband speeds slow down in the early evening.

The Contention Ratio is a measure of how many customers share one block of Internet bandwidth.
For business use, you need to have a Broadband connection with, at most, a 20:1 contention ratio, which is why business Broadband costs at least 50% more than a domestic Broadband connection.
Some ISPs offer Broadband connections with a 5:1 or even a 1:1 Contention Ratio, but these can cost between £150 and £300 per month.

File Transfer Speeds

Here's a table that shows how long it takes to transfer files of various sizes over different Internet connections.
The best possible connection speed is assumed for each connection method plus there's no allowance for contention.

We've divided bits per second by 10 to give bytes per second to take into account protocol overheads.
We didn't include WiFi as a connection type because this is normally an intermediate connection method to another type of Internet connection.

The big lesson to learn from the above table is that for remote access to be useful, you have to have a general idea of the file sizes you're working with and the speed of the Internet connection method you're using.

UP Speeds and DOWN Speeds

The A in ADSL stands for asymmetric which means the connection speed from the Internet to you (DOWN speed) is different from the connection speed from you to the Internet (UP speed).
In an asymmetric connection, the DOWN speed is always higher than UP speed.
Probably because UP bandwidth is more expensive to an ISP as there are tricks to artificially increase the DOWN speed such as using a web- cache.

Here's a table comparing UP and DOWN speeds for various Internet connection methods:-

For general Internet use, such as downloading web pages, more information is downloaded than uploaded so a lower UP speed doesn't affect this.
For remote access, you're just as likely to be uploading as downloading files between, say, your home and the office, however, there is a much more serious consequence of an asymmetric connection which is illustrated in the following diagram:-

Downloading a DVD over GPRS at the standard rate would cost £8000.

If your office and home are connected to the Internet using Broadband, when you are using remote access to your office and downloading a file to your home PC, you are, at the same time, uploading it at work.
When there is a connection path between 2 computers that has different sections operating at different speeds, the end-to-end connection speed attainable is always equal to the speed of the slowest section.
This slowest section is called the bottleneck - the narrowest part of a bottle that limits the speed at which liquid can escape from a bottle.
So, in case you haven't worked out the bad news yet, when you use remote access to your office the connection speed will be the lower figure shown in the UP Speed column in the table above.
The actual speed will be determined by the slowest of the 2 connection types being used.

In the tables shown so far, we've been assuming ideal connection speeds rather than those obtainable in real life and we've completely ignored the effects of contention.
The following diagram shows all the places where contention can affect the actual connection speed:-

Tips for Using Remote Access over Broadband

If you're feeling depressed about the prospect of getting a usable remote access system for your office, don't be. There are lots of ways to make it work and here are some tips:-

	Use Remote Desktop for remote access instead of a VPN. With Windows Server 2003 you get 2 free Remote Desktop connection licences. This way no files are uploaded or downloaded, a remote PC just sends key-presses and mouse information and receives screen update information which only requires 28kbps to make it usable.
	Try and minimise the size of files you work with. For example, have a separate spreadsheet for each month's sales figures instead of having one file fro the whole year with separate sheets for each month.
	Choose the Broadband connection with the smallest contention ratio and highest UP speed that you can afford. Consider an SDSL connection.
	Get a second Broadband connection just for Remote Access clients.
	Host some of the services you use on servers which have a direct, uncontended connection to the Internet. This avoids the double-Broadband speed and contention problems. This can include your office email system, file storage and web-based database services. Arrowmail can help you with hosted email and file storage.

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