Identifying Features of a WAN
Sometimes people mistakenly want to identify a Wide-Area Network (WAN) by the size of the network or by the devices that compose the network. For example, if your network has 5,000, devices and you are not using WAN technologies to interconnect them, you do not necessarily have a WAN. If you have a large campus network using routers and dynamic routing protocols and an internal infrastructure, you do not necessarily have a WAN.
So, in case you have not already guessed, a WAN, by definition, uses infrastructure that you do not own, but that is owned by a telephone company or another external provider. If your network uses a network infrastructure that is owned by your service provider, implementing WAN technologies, you have a WAN. This infrastructure can fall into many areas or technologies; the big criterion is that the infrastructure is not yours.
Sending data long distances
Although long distances are not criteria for defining a WAN, commonly, WANs do span substantial distances. If your WAN spans only a single city, across town is a long way; nevertheless, your carrier may choose different technologies for that distance than they would if your network spanned a state, country, or continent.
So, although distance is not a true criterion for determining whether your network is a WAN, most WANs do span a great distance, and the technologies used in the WAN depend a great deal on the distances involved.
Implementing routing protocols
Routing protocols are also not true criteria for a WAN definition. A WAN can either use manual routing or implement a routing protocol such as RIP or EIRGP. Although larger, more complex networks like a national WAN may be easier to manage when implementing a routing protocol, their use does not dictate that you have a WAN.
A large corporation could have a single (but large) building or a campus of several buildings that causes the network to have several routers. To make life easier on the routing front, you could choose to implement one of the many available routing protocols. So, although most WAN environments make use of routing protocols, not all networks that implement routing protocols are necessarily WANs.
Using carrier equipment
Carrier equipment, means the equipment from your telephone company that allows you to connect your network to the backbone of its network. These network connections can be digital subscriber line (DSL), frame relay, fiber optic, broadband cable, or another technology used by your telephone company or network provider.
This component really turns a network into a WAN, allowing your traffic to travel between your locations while traversing another provider’s network, mainly your ISP or telephone company.
In some cases, this traffic may cross several providers’ networks. If you are connecting two offices and they are in different countries, you may be crossing networks owned by a regional provider, which connects to a national provider and then crosses borders and travels across the other national provider to another regional provider before finally reaching your other branch office location.
It is this use of other people’s networks that really defines use of a large LAN versus a WAN (LANs are covered in the next section). So, a WAN is not related to the size of your network, or to your choice of routing protocols, or to any other factors.