A traditional corporate or enterprise network is usually defined with a hierarchy of different topologies.  Most internal networks will be constructed (or perhaps grow) with a series of LANs (Local Area Networks) combined together.  While moving up to local and regional networks which will be constructed using things like educational or campus backbones or perhaps a series of MANs (metropolitan area networks).  WANS will generally work on a wider scale linking geographically dispersed locations based in offices or sites across the globe.

What medium can you use to construct a WAN?  Well there is no strict definition, in fact just about any long distance communication medium can be used as a WAN link if it works.  Typical setups usually include switched and permanent telephone circuits, terrestrial radio link and even satellite systems.  All sorts of factors determine which is used ranging from geography, atmospheric and of course costs of the solutions.   There is another level of complexity to setting up a network connection on such a wide scale and in fact WAN’s are well known for being high cost to set up with slower data rates especially if you have to use long distance leased lines.  The slow data transfer rates are often simply due to cost, high speed leased lines like T1s are available but usually costs a huge amount of money.

Often the driving force of a leased line is security – ensuring that a line is both secure and private.  The speed of transfer is normally sacrificed in order to minimize costs, although whether it’s constructed using leased lines or satellite links they are almost always an expensive option.

Nowadays there are more options for creating WANS, it is possible to connect remote offices using virtual circuits over traditional packet switched, frame relay or even cell relay (ATM) networks which work out much cheaper than the leased line options. Most of these can be set up either by corporations themselves if they have the skill sets or it’s often more economical to purchase such links through Internet Service Providers (ISPs).  Typically these connections will be known as VPNs (Virtual private networks), secure encrypted lines effectively being transported through other people’s hardware.

Typically some businesses will use these connections to set up extranets  which are really extensions of a company’s internal network across the internet to another business. Obviously these are only suitable for businesses which work closely and trust each other implicitly, you’ll often find them created between companies who share owners or are members of the same group.  What is important is that although these connections use hardware not controlled by the companies themselves they are protected by encryption and a strong authentication system.   Both the inside networks should be protected against external attacks which will also require firewalls and IDS (intrusion detection systems) set up at the endpoints of the network connections.

There are many examples of WAN technologies which you may not have come across as it’s a relatively specialised field.  A WAn is very different from a series of shared LANs because it will allow simultaneous transport of traffic of many users using whatever transmission mediums if selected – here’s a brief list of some of the technologies which are used to build a wide area network like this:

  • Switched Digital Services
  • Leased Lines ( Private Network)
  • Packet Switching
  • Frame Relay and Dial up Private Networks
  • Cell Relay (ATM)
  • SMDS (Switched Multimegabit Data Service)
  • Internet ( The biggest public packet switched network!)

Within this web site we hope to cover all of these communication methods in more detail.  Most of these methods are still used extensively across the world and you’ll find that they all have strengths and weaknesses.  WAN links often are crucial to an enterprise and it is important that the function reliably and can accommodate all the users and applications transmission requirements fairly.   The ability to prioritise and schedule connections using techniques such as multiplexing is also an extensive technology field that should be understood before creating and managing a WAN connection.

John Harris

http://www.theninjaproxy.org/