Nowadays, there have several types of network topologies with different characteristic, price and level, it was very important to choose a suitable network. Now we are going to discuss four basic network topologies : Bus, Ring, Star and Mesh.
Let’s discuss bus topologies first, bus network topologies is a single cable which use to connect to different points between network, as it only have one channel to support the bus network for communication, so the total capacity will send to all the points averagely. When a point want to send instructions to another point, it will announce a message to all the points thru wire and all the points will see it but only the destination point will receive and return the message to the sender point, other points will not give any response.
Bus network topologies are cheaper than other network topologies because it use less cable and materie and also the installation is easier than other topologies. But because it is a single cable, when there have many points connect to the device, it will slow down the transmission speed and the total capacity.
On the other hand, once the network have problem, it cost many times to fix it as you have to check all the cable connection to find out the problems. Also in a bus topology, once a single connection failure, it will stop the passage between all points.
(The image of the About.com guide)
Second topologies which we are going to discuss is Ring topology.
In a ring network, each apparatus connected to two users for communication purpose. It looks like a circle and the message move around the circle to each point use single direction. Each node connect to its own cable to the Medium Attachment Unit (MAU). Ring network topology is easy to install and reconfigure and also easy to add new node as only two connections need changes.
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However, Ring network is not too convenience for the user as the data have to pass through all the points before getting to the destination. For example, if one network have six user, when the A computer want to send message to F computer, it have to pass through B, C, D, E computer and then to F. And if one network failure, whole network will disable because it only have single pathway to transmit the data.
(The image of the About.com guide )
The third network topology is Star.
Star network is one of the most usual computer network topologies. It features a central connection point call hub or concentrator (Bruce A Hallberg 2005) and it will radiate to other points. The characteristic of Star network is the hub or concentrator work as a central union to provide different route for signal send out to any two sites. Data on star network will send the message to hub or concentrator first before send to the destination point. Hub or concentrator works like a repeater for the data flow.
In the star network topology, if one connection stoppage, only one node will lose the connection from this site and it won’t be affect to other networks. On the other hand, it will be easy to find out the problem as all network is obey to hub, so once the network out of service, mostly it must be some problem with the hub and the problem can be fix quickly instead of checking all the points. Furthermore, as hub is control everything included add or remove devices, that means Star network is easy to install. If you want to add some new devices to the network, just need to connect the cable to hub and other computer will detect the devices and can use it. It save lots times to install the devices to all computers separately in the network. Moreover, hub can also be act as a backup file, once the network is not work, you can move to another computer and using the data from hub.
Although star network is more stable than other network topology, but star network is more expensive as it needs more wires to support the network. And because it is fully obey to hub, once there have many nodes, the network maybe slow down.
(The image of the Florida Center for Instructional Technology College of Education, University of South Florid 1997.)
Last network topology we have to share is Mesh.
Mesh network is a network where all the nodes connected to each other with different ways, maybe single hop or multiple hops.
In a mesh network, if one node or cable have problem occur, there will have another way to communicate with other node, it won’t be halt the whole network. Mesh network will also default the short way automatically while the message moving on the mesh network, that means the data no need to pass through all the points before reach to destination, it save many times for transaction the data.
Mesh network is a network which is not easy to interruption by connection problem as there have many possible patterns that can use. When one node failure to connect, mesh network will find another way to reach the destination easily.
Mesh network separate to two similar types: Full mesh and Partial mesh.
Full mesh which every node will connect to each other so the network can provide best redundancy function. Once one of the nodes breakdowns, connection between the networks will be stronger under full mesh network because there have more possible route to reach to destination. Because of more wires need, so full mesh network is expensive than partial mesh network and it may also affect the set up procedure because of the complexity.
For the economical reasons, some of the company will prefer to use the partial mesh network. In partial mesh network, devices are only connects to a subsection node instead of all nodes. This may affect the entire network once the connection have problem because it only have one or two ways to reach the destination point. Although the communication between the networks is not as strong as full mesh network, but the cost is cheaper than it, so nowadays partial mesh network is more popular than full mesh network.
(The image of the network dictionary 2004)
Physical communication media is a path that can let the electronic data move from one computer to another. And now will going to describe different physical communication media, for example Twisted-Pair cable, Coaxial Cable and Fiber-optic cable.
The first cable we are going to talk about is Twisted-Pair cable.
Twisted-pair cable which can be subdivided as unshielded twisted pair (UTP) and shielded twisted pair (STP) (Bruce A Hallberg 2005). Both UTP and STP have eight separate brown metal wires and cover by insulate material. Besides, each pair of wires was wound to each other.
UTP and STP not only have similar structure and also have similar transmission technology. Even though STP has a better protection interface and quality than UTP, but it cost more expensive and not easy to install.
Using Twisted-pair cable’s advantage is its size is smaller than others so that it will easy to install and it cost cheaper than Coaxial cable and Fiber-optic cable.
On the other hand, the transmission signal is shorter than other communication media and the coverage area is only 100 meters.
Another cable we are going to talk about is Coaxial Cable.
Coaxial cable is cover by 4 layers: copper wire, insulation, copper mesh and cable jacket. Coaxial cable can aid 10-100 Mbps and it coverage 500 meters. (Scribd n.d.)
The advantage of Coaxial Cable is it can run for a long distance between network but use less power. The cost of Coaxial cable is cheaper than Fiber-optic cable and because of it use for many years, so it will be more popular.
However, the size of Coaxial Cable not as thin as Twisted-pair cable, so it will be difficult to install and relatively the set up fee will be higher than Twisted-pair cable.
The last one we have to talk about is Fiber-Optic cable.
Fiber-Optic cable is made by narrow core and insulates material. It use the lights to transmission the date. Most of the corporate network will use Fiber-optic cable as back bones to connect different network.
The advantage of Fiber-optic cable is it has a higher data speed and the higher bandwidth is good for future development.
But Fiber-optic cable is not quite flexible as it cannot curve, so it will be more difficult to install and the cost is the most expensive one.
Different computers have its own different purpose, we are going to compare Microcomputers, Laptop computers, Minicomputers, Mainframe computers and Supercomputers’ size, speed, processing capabilities, price and how many users can use at the same time.
Types of computers
Fits on desk
Small and conveyable
Size in between microcomputers and mainframe computers
Partial room of apparatus
Full room of apparatus
Up to 400 million
Up to 400 million
Thousands to millions
Millions to billions
Surfing the web
Surfing the web
Basic productivity software
Processing data quickly and information storage, mostly using on airline system, back or insurance company.
Process very large amounts of date, such as weather forecasting and government.
Price of computers
From $2500 up to $17000
From $2500-up to $23000
several million dollars
Several million dollars and up
Simultaneously connected users
For individual use only
For individual use only
Two to four thousand
Hundred to thousand
Hundred to thousand
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