It’s upgrade time at the company and this is good news. Why is it good news? The network infrastructure is getting overhauled – and it desperately needs it. Currently the network is struggling to supply the demand. The throughput is slow and if one segment of the network has a problem, it effects all the computers – not just one (Barrett & King, 2005)(pgs 93-94). This isn’t due to the network being set up incorrectly though. The problem lies in the topology that was chosen to do the job.
The company decided to initially use what is known as a Bus Topology. This is a fairly simple way of setting up a LAN. The cabling is easy to set up and the layout is simple.
There is one main ‘backbone’ that all the computers are hooked into. This is a single cable that connects all computers to each other. When the company created this network, bus topology seemed to be a fine way to quickly connect all the computers together. This is true, but it comes with its downfalls too.
For starters, this topology is making use of 10base-T Ethernet standard. This is created using a Cat3 cable that enables a transfer speed of 10Mbps (GeekInterview.com, 2010). This is fine for simple document transfers between a few computers. The problem is that as more computers are added to the network, and larger files begin being shared, 10baseT just doesn’t suffice. This topology is bogged down due to the fact that all the computers on it are running on the same bandwidth. This slows throughput as more computers join the line. For this reason, there are seldom more than a dozen computers on one network.
The bus topology is a non-intelligent network. Imagine a circle of computers all connected. They are labeled Host A though G. If Host A were to send something to Host E, the data would be sent from Host A to the backbone. The backbone would then circulate the data from one computer to the next until the computer listening for the information claimed it. This type of ‘passive’ topology can cause problems. Pieces called terminators are needed in this topology at either end: otherwise the signals that weren’t claimed would continue bouncing back and forth – tying up the line (Barrett & King, 2005)(pg 94).
The last problem with bus topologies is error control. This type of network depends on a complete circuit throughout. If one computer were to come unconnected, the entire network would malfunction. Finding where these problems are located becomes very difficult when the problem could easily be anywhere (Barrett & King, 2005)(pg 94). Many of these problems are easily solved through the use of a different topology – A Star Topology.
The star topology – the far better choice over the outdated bus topology. In a star topology, all computers are connected to a central hub using their own cable – their own dedicated line! Remember that problem the bus topology had with error control? If one segment went down, the whole network went done. With the star topology, this isn’t the case.
If one of the lines from the router to a computer got cut, the rest of the network wouldn’t even know it! It’s much easier to find the problem when it’s completely isolated (Barrett & King, 2005)(pg 98). Of course, there is always the chance the hub – in this case, a router – could break. This would disrupt the entire network, but it would still be fairly easy to assume where the problem is if all the computers were having a problem. Making computers isolated also provides the company with the ease of being able to move or remove computers at anytime (Barrett & King, 2005)(pg 96).
Lets talk about growth too! Perhaps the company is in the need for more that just ten computers on their network. Maybe the company needs more like 300 because it’s growing everyday. Bus topology would not be able to handle this demand at all. Star topology though, can physically support up to 1024 workstations (Barrett & King, 2005)(pgs 96-97)!
Last, but certainly not least – speed. 10Base-T is barely fast enough for a company needing to network 300 computers together – not to mention it just couldn’t handle that many connections. 100Base-T can run ten times faster though and using Cat5e cabling, is definitely possible on a star topology. 100Base-T is capable of transfer rates of up to 100Mbps (www.geekinterview.com(2), 2010).The only real downside to a star topology is that it will require much more cabling than that of a
bus topology. The positives far outweigh this small downside though and should keep a company from using a star topology.
References:
Barrett & King. (2005). Computer Networking Illuminated. Sudbury, MA: Jones and Bartlett Publishing.
