In this lesson, we’ll examine and understand the different types of network typologies and how they apply to Wide Area Network. Their differences in data transmission will be examined. We’ll understand their advantages and disadvantages accordingly.
What is a Wide Area Network?
A Wide Area Network (WAN) is a communication network of devices which spans geographical areas. It is an interconnection across geographical locations, of multiple Local Area Networks (LANs) which are small communication networks in the same locality. WANs can be compared to a spider web. The multiple webs confined with a house (locality within building or area or country) are LANs while when they grow to the extent that they traverse multiple houses (internationally across different countries), they become WANs. This is illustrated in Figure 1 and Figure 2.
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Network topology describes the arrangement by which the components of networks (LANs or WANs) are organized. We will now examine the different topologies by which a WAN may be arranged.
Types of Network Topologies
Bus Network Topology
The Bus topology within the WAN environment often covers small geographical areas i.e. within the same country. The Bus topology is characterized by the hard cabling (commonly called backbone) in which the different sites on the network are connected by high capacity network cabling.
In this orientation each site is connect in a line with the other sites via the backbone. With the exception of the sites at the end, each site is connected to another directly before and after it. This is illustrated in Figure 3.
In this Bus topology, if a site wishes to communicate with another site, it broadcasts a message on the backbone, which is accessible and seen by all connected sites The recipient, however, will be the only one to retrieve the message.
It is cost effective and simple to implement. There is comparatively minimal cabling with each site connected by a single cable.
There is complete network failure in the event that one of the site cables fail.
An increase in the number of nodes increases the traffic on the backbone reducing network efficiency.
Ring Network Topology
As the name suggests the Ring topology orientation has sites arranged in a ring. This is very similar to the Bus topology discussed earlier. The main difference being there are no sites at the end.
Each site is connected to each other as seen in Figure 4 with the last and first sites connected completing the ring.
Network traffic can be routed in both directions. This makes this topology less vulnerable than the Bus topology. If a line connection fails traffic is rerouted in the opposite direction and communication is not lost. Repeaters are also used to maintain network integrity and prevent data loss, when there are a high number of sites.
This is because for n number of sites data will have to traverse n nodes until it gets to the desired destination increasing the likelihood of data loss.
Star Network Topology
With the Star topology, the sites are arranged in a star formation. There is a central hub and each site is connected directly to the hub. This is illustrated in Figure 5.
In this topology the central hub is known as concentration router which ensures that transmission reaches the correct destinations at all times. A failure is a site connection that does not affect other parts of the network.
Mesh Network Topology
In the Mesh topology every device belonging to the network is connected to every other device in a mesh formation. This is quite different from the previous topologies where sites are connected to a maximum of two sites at a time.
With this topology there are multiple routes by which data transmissions reach their destination.
All sites are connected to each other and there are redundant paths for data transmission. This is a total mesh orientation. With the partial mesh topology some sites are connected to all the others while other sites are only connected to a few sites. Data transmission is achieved by routing or flooding.
Tiered Network Topology
The Tiered topology entails the interconnection of clusters of Star network WANs by the use of concentration routers.