A A Wide Area Network or, "WAN" is a computer network that extends beyond a single physical location to span multiple, geographically disparate, locations.  Perhaps the most common use of WANs in the world today is found in business where regional offices are connected together to share resources such as documents, email functionality, financial systems and the like.

WANs can use open networks such as the Internet or dedicated lines connecting offices directly to span the distance between them.  WANs over the Internet are by far the most common, mainly due to their convenience and far lower costs than the alternatives.

A. Most business broadband providers only state the downstream connection speed (typically 8Mb/s to 24Mb/s) rather than the far slower upstream connection speed (typically 0.5Mb/s to 0.8Mb/s).  To give this some context, even in the very rare situations where the advertised speeds are reached the downstream and upstream connections are still 43 and 1280 times slower respectively than a modern (Gigabit) office network.

Exacerbating this, is the fact that if a user in one office wishes to download a file from a second office, it is the second office's upstream connection that becomes the bottleneck.  Combine this with typical broadband performance, contention between different subscribers to the same broadband provider and mulitple users and it is not unusual to see opening a Microsoft Word or Excel document take several minutes.  Clearly, such performance is likely to be extremely inefficient and unacceptable to users.

<p>A. In its most common use, a VPN, or Virtual Private Network, is a computer network spanning multiple physical locations using links which are open to the public.&#160; For example, VPNs are frequently used to link different geographical locations over the Internet.</p>
<p>Given the universally accessible nature of the Internet, data transmitted over a VPN might be intercepted by external parties.&#160; VPN traffic is therefore protected with strong authentication and encryption making it extremely secure.</p>

A. MPLS is all about using bandwidth more intelligently - simply put, MPLS can prioritise certain types of data over others to ensure business critical applications or applications requiring minimal latency (for example VoIP telephony) are not slowed down by less important data.

For example, if a user is speaking to a customer over VoIP and another user starts to download a very large file from a website, without traffic management neither would have a priority and the VoIP telephone call would likely suffer from lag and poor voice quality.  Clearly, it would make more sense to slow down the file download and prioritise the voice traffic since a few extra seconds for the download would make no discernible difference.  MPLS can achieve this over the WAN.