What Is a WAN Topology?
By Andy Walton
A wide area network (WAN) topology describes the layout of network components and connections on a given WAN. Although WAN design can appear complex, most such networks are based around one of a few simple topologies. Learning these topologies will aid in understanding the design of large modern networks, and could provide an insight into the workings of your own business's network.
Point-to-point networks see WAN sites connected by high-capacity network cabling known as backbone. The sites are connected as if in a line, with each site (other than the ones at the ends of the line) only linked to the sites directly before and after it. This is a simple topology to implement, and provides cost benefits in that it requires minimal cabling. However, it leaves networks vulnerable to failure, as a single fault on the backbone can bring whole sections of the network down.
The ring topology is the same as the point-to-point topology, except the sites at the end of the backbone are connected to each other as well. This makes ring topology WANs less vulnerable to failure, as traffic can be routed the opposite way around the ring if a fault is detected on the network. However, adding new sites to ring topology WANs requires additional work and cost when compared to point-to-point setups, as each new site requires two connections instead of one.
The star topology sees all sites connected to a central hub, a little like the spokes of a wheel. WAN hubs use a technology known as a concentrator router to ensure data is sent to the right destination. This topology allows for sites to be added to the network easily – an important consideration for business WANs – and is not vulnerable to a single cable failure bringing down the whole network. However, it is entirely dependent on the concentrator router to be able to run.
A tiered WAN sees many smaller star-type WANs linked together by concentrator routers. This provides the scalability benefits of the star WAN while reducing the network's dependency on individual pieces of network hardware. If one of the routers fails, traffic can be rerouted to avoid the affected area. Some tiered networks also include direct links between sites, known as meshing. The principle downside to tiered and meshed networks is complexity – they can involve a lot of links and require a lot of management.
Andy Walton has been a technology writer since 2009, specializing in networking and mobile communications. He was previously an IT technician and product manager. Walton is based in Leicester, England, and holds a bachelor's degree in information systems from the University of Leeds.