BT's new fibre optic broadband

If you live in the UK you only really have two options when it comes to Internet. Either you select a DSL service provided over your standard local telephone network, or cable primarily provided by Virgin Media.

The most common DSL technologies in use today are ADSL and if you are lucky ADSL2+. The biggest weakness of DSL is the reliance on the copper infrastructure, which results in significant performance degradation the further you are from your local exchange. For example, ADSL2+ has a maximum theoretical bandwidth of 24Mb/s downstream, however to get that speed you would literally need to be attached to your local exchange. Most common ADSL speeds across the UK range from 2Mb/s up to 8Mb/s downstream. If you have cable you have the option for greater performance, currently up to 50Mb/s downstream, however only approximately 50% of the UK is connected and therefore cable has limited consumer reach.

Although these performance numbers probably don’t sound too bad for the average user, when you consider countries like South Korea are currently offering to the majority of households 100Mb/s downstream for less than £30 a month, with plans for aggressive expansion up to 1Gb/s downstream, suddenly the UK infrastructure looks quite obsolete.

Thankfully BT (who own most of the standard local telephone network across the UK) aim to improve the situation with their Fibre to the Cabinet (FTTC) roll-out which began in 2009.

Fibre to the Cabinet (FTTC) is the generic term for broadband network architecture delivered by optical fibre up to your local cabinet. As a result, users are able to receive significant performance increases as the fibre is less susceptible to interference and is capable of maintaining higher bandwidth over longer distances. "To the Cabinet" means that you will be connected by fibre from your local exchange to your local cabinet which is normally no more then a few hundred meters from your home. As a result, only the last few hundred metres relies upon the existing copper infrastructure which should allow for up to 40Mb/s downstream.

As well as the switch from copper to fibre, DSL has also evolved to VDSL2. This new technology theoretically provides data rates exceeding 100Mb/s simultaneously in both downstream and upstream directions. The maximum available bit rate is achieved at a range of about 300 metres, which makes it the perfect technology to accompany the BT FTTC roll-out.

The downside to this technology is that it will take time to get enabled in your area. The infrastructure is being delivered by BT Openreach and involves a significant amount of work. You will also need a new VDSL2 compatible modem/router to be able to terminate the new connection. BT have predicted that only 40% of the UK will be enabled by 2012.

To check when your area will be completed head over to the BT Infinity website (Infinity is what BT are calling their fibre broadband service). From here you can enter your BT phone number to check for availability. Thankfully my area was one of the first in the UK to be completed so I receive the following results:

Although it could be a long wait before all of the UK infrastructure is upgraded, at least there is now a plan for the future and the advantage of FTTC is that the next logical step is FTTP (Fibre to the Premises) which will deliver fibre right to your home and should offer speeds up to and beyond 100Mb/s downstream.

So the future of the Internet is in sight, it's just not quite here yet. For more information on the FTTC roll-out I suggest you head over to www.leyingitout.co.uk.

Using a Proxy Auto-Config File

A proxy auto-config (PAC) file is used by web browsers to automatically choose an appropriate route to a proxy server for connection to the Internet. It can also be used to route certain groups of users to a specific proxy server and dictate different actions such as routing or filtering for certain URL’s and/or IP Addresses.

PAC files are primarily used in medium to large enterprise networks that use proxy servers with multiple breakout points to the Internet. The PAC file is used to simplify browser configuration, management and support as each time a user attempts to access the web the browser will automatically fetch the PAC file before attempting to access the Internet. This is useful because if you make a change to your network that impacts your Internet gateway infrastructure you don’t need to individually roll out a change of settings to all your users, instead you update a single file which is generally stored in a central location. By storing the file centrally it also makes management and support significantly easier. However, it should be noted that it can also add a single point of failure if no additional redundancy is introduced.

The PAC file settings can be configured in Internet Explorer by going to: "Internet Options > Connections > LAN Settings" and ticking "Use automatic configuration script".

The PAC file is essentially a JavaScript file that includes the function "FindProxyForURL" that accepts two arguments "url and host". This function is called before the browser requests a page and it tells the browser whether it should route to a proxy or attempt to go direct.

An example of a simple PAC file can be seen below:

function FindProxyForURL(url, host) { return "PROXY proxy01.fakecompany.com:8080; DIRECT"; }

In the above example all URL’s will be routed to “proxy01.fakecompany.com” on port “8080” and if this address is unavailable it will attempt to route direct. However, unless you have specific routing configured on your network for direct access, the request would fail.

For more information on PAC files please refer to the article "Writing Effective Proxy PAC Files".