In same country. The Bus topology is characterized

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.

LAN

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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.

Communication

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.

Advantages

It is cost effective and simple to implement. There is comparatively minimal cabling with each site connected by a single cable.

Disadvantages

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.

Ring_Topology

Communication

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.

Advantages

  • Data transmission is unidirectional.
  • Cheap to install and easy to add on nodes.

Disadvantages

  • Troubleshooting issues can be difficult and adding/removing nodes can cause network disruptions.

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.

Star_Topology

Communication

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.

Advantages

  • Adding and removing nodes is easy and the network is more robust, with the orientation preventing data collision between sites.

Disadvantages

  • It requires more hardware.
  • The entire networks operation and efficiency depends entirely on the hub.

    If the hub fails for any reason the whole network goes down.

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.

Mesh_Topology

Communication

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.

Advantages

  • This topology is very robust and less prone to wide scale system failure.
  • Troubleshooting is simple.

  • There is an increased level of security and privacy.

Disadvantages

  • Implementation and configuration are more complex than the other topologies.
  • Implementation incurs high costs.

Tiered Network Topology

The Tiered topology entails the interconnection of clusters of Star network WANs by the use of concentration routers.

Communication

The Tiered topology with close examination is a partial mesh/bus combination. Data transmission via concentration routers helps to boost the broadcast signal in the presence of so many nodes forming the network. Numerous redundant data transmission routes makes the system very robust.

Advantages:

  • This is a combination of Star and bus topologies.
  • Extension of the network is simple easily maintained and robust.
  • Troubleshooting is simpler.

Disadvantages:

  • It is hardware intensive and so implementation is expensive.

    As the number of nodes increases maintenance becomes complex and more expensive.

Lesson Summary

Network topology describes the different ways in which the components of Wide Area Networks are arranged. There are different types of topologies. They are the Bus Topology, Ring Topology, Star Topology, Mesh Topology and the Tiered Topology. While the Bus, Ring and Star configuration are simpler and inexpensive to implement they are vulnerable to failure.

The Mesh and Tiered topologies are much more robust and more reliable but very expensive to implement as the number of nodes grow.

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