Network Topologies

Network Topologies:

Introduction:
Each network is different and this requires a structure, also known as ‘topology’, this is the layout of the network devices. In this blog post I will be explaining about the different network topologies which are listed below (these are the most common ones).

• Bus
• Ring
• Star
• Tree (or hierarchical)
• Mesh

With each topology, I will identify its use of operation, its advantages and limitations. In addition, I will also use suitable diagrams to further enhance my explanations.

Bus:
The bus is an old historical topology which allows easy connection for different devices to the network by having a single core cable (bus) running through the middle, (see figure 1). By having this structure laid out conveniently, the advantages of the bus topology is that it allows new devices to be added easily because the core cable can be extended. Furthermore, this is also beneficial for LAN because it is used within the same geographical area. On the other hand, the limitations for the bus topology is that one half of the system and devices on one side will not work if cut, making it unable to communicate from the first device to the last.  Despite the above limitation, the whole line can also be disrupted if the core cable has an issue, therefore the network stops working. Data collisions may also take place if the traffic of the data overflows.

Figure 1: Bus Topology

Ring:
The ring topology is a very well operated network as each network has an equal share of bandwidth. It works together in harmony as each node has the opportunity to communicate by taking in turns, ultimately meaning that there will be no overflow of data as only one is used at a time, (see figure 2). This allows an overwhelming advantage/benefit as it is very well structured and organised. This leads to another benefit of it as being convenient to add more nodes/computers. However, the limitations are that there is a chance one node may send more data by communicating more, slowing down the network overall. Additionally, using this topology also means that there is less privacy and the security is greatly limited due to each node being able to see the traffic of its adjacent neighbours next to it. Lastly, because each node is connected, it can affect the system if either one node or if the central hub fails.

Figure 2: Ring Topology

Star:
The star topology is when different nodes are all connected and linked directly to the centre, known as the ‘hub’ such as a router for data transfer and connection. The router in the middle can control all of the other nodes as they work together indirectly, (see figure 3). The benefits of this topology are if one part of the system gets cut off, it will not affect the others. Moreover, if each node has its own cable running directly to the core router, then that means the chances of data collisions are greatly reduced. Nonetheless, the limitations are simple – if the main router hub gets dislocated, the whole of the network will also go down and fail. This also makes it unbeneficial and therefore a limitation because the amount of cables required can be costly to set up despite its reliability.

Figure 3: Ring Topology

Tree (or hierarchical):
This topology is convenient when it represents a hierarchy of an organisation, company, or business as it can represent how the system is laid out for different fields of importance in the form of a tree shape (or a star/bus), see figure 4. It is formatted in a logical order as the core centre at the top, and leading down is expansions and a variety of branches for the nodes. The advantage of this topology is it allows components to be added easily due to its organised layout. Another benefit of the tree topology is if one connection line or node is down, it can be easily identified as the structure is well defined. Nevertheless, one limitation is that the centre still has the properties of a star, so if the main hub fails, the whole system will too. Another limitation is the maintenance as the costs are high due to its size and complexity of cables needed to run this network structure.

Figure 4: Tree Topology

Mesh:

The mesh topology is a series of connections for multiple and varied paths for the data to travel to, generally attached to each other node so that it allows data to be relayed from one place to the other in the quickest route possible, (see figure 5). The benefit of mesh is the ability for the system to keep functioning to communicate and thus relay more data even if one connection line fails, suitable for high data traffic. In conjunction with the above benefit, it also allows easy identification of its whereabouts if one node and or line fails. However, to set up the network to be structured in a mesh topology, it will require a lot of complex set up and maintenance as it expands forwardly, this is also because of the excessive amount of cables needed. Additionally, as it expands continuously as time progresses, the second limitation is many connection lines may become redundant as other connection lines may be faster than others, (no longer needed) and this will mean some cables are wasted, increasing overall costs.

Figure 5: Mesh Topology

Harvard Referencing: (In order of reference)
- Anderson, K. Atkinson-Beaumont, D.Kaye, A. Lawson, J. McGill, R. Phillips, J and Richardson, D. 2011. Information Technology Level 3 Book 1 BTEC National. Harlow: Pearson Education Limited. P.305.
- Figure 1: bbc, 2014. Bus Topology. [Online] Available at: <http://www.bbc.co.uk/staticarchive/9933e41867b45fa9319fa74db5ac7f33b71d44c8.gif> [Accessed 15 January 2015].
- Figure 2: studydroid, n.d. Ring Topology. [Online] Available at: <http://studydroid.com/imageCards/0p/ld/card-26916531-back.jpg> [Accessed 15 January 2015].
- Figure 3: mattytv, 2012. Star Topology. [Online] Available at: <http://www.mattytv.com/blog/wp-content/uploads/2012/06/star.png> [Accessed 15 January 2015].
- Figure 4: ecomputernotes, n.d. Tree Topology. [Online] Available at: <http://ecomputernotes.com/images//thumb474-Tree-Topology-9b75e7959710e5df73e20d5806405a51.jpg> [Accessed 15 January 2015].
- Figure 5: brainbell, n.d. Mesh Topology. [Online] Available at: <http://www.brainbell.com/tutorials/Networking/images/01fig06.gif> [Accessed 15 January 2015].

Bibliography: (In alphabetical order)
- ianswer4u, 2011. Mesh Topology Advantages and Disadvantages. [Online] Available at: <http://www.ianswer4u.com/2011/05/mesh-topology-advantages-and.html#axzz3Ovjx0358> [Accessed 15 January 2015].