According to question 1, group of business employees wants to build up a small networking office. A good computer network should builds up with minimal cost of physical media and installation, but the maximum performance, which helps lower the business budget and optimizes business productivity. It is also must have the scalability and flexibility to make changes, to upgrades, to increase stations, to increase coverage, and etc, when in time of a huge increases of demand. Moreover, the computer network should not have any single point of complete failures, which mean if a single station on the network is out of service and it must not affect the whole network's functionalities. In order to builds up a computer network that achieve these requirements, we need to understand the various types of network topology.
Network topology refers to the physical layout or design of network, and computers are connected using the design of the topology. Network topology also defined as the style which nodes are geometrically arranged and connected. There are five types of topologies commonly used in the network, which is bus, ring, star, tree, and mesh.
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Bus topology consists of a main run of cable, or bus, as a backbone of the whole network system. In each end of the bus consists of a terminator. All the nodes (servers, stations, and peripherals) are attached directly onto a bus through a hardware interface called a tap. Any of the station could sends out the message onto the bus. When a station sends out a message, the signal is broadcasting and all the other stations on the network could receive the information, but only one station accepts the information by using address matching. However, the signals on the bus would not discard by itself, so the terminators works to absorb the signals and removing it from the bus.
The advantages of the bus topology are easiest to use and install, requires fewer physical connection media, thus lower cost. It is also able to extend the network by adding the repeaters.
However, the disadvantages of bus topology are only allows a station transmitting at a time, because the signals will be overlapped if two stations transmitting at a time. Another situation is, when one station attempt to transmit continuously for a long period of time, it makes heavy network traffic. Failure of the bus will affect all the attached nodes on it, since the bus was the main cable supplying the connections of the entire network. When the whole bus network was down, it is very difficult to identify the problem, or troubleshooting. If the bus is damaged, if wont not have any connections on the entire network until the bus has been replaced or fixed. Furthermore, it is very difficult to add new nodes after the network has been built up.
In ring topology, each repeater is connected to the next repeater, and the last one connected to the first. It physically created a ring-shape like when looks from the top. The signals on the cable travel in one direction only, since the repeater retransmits what it receives to the next repeater, so the data will be circulate in ring. The direction could be either clockwise or anti-clockwise.
Each station attached onto the network via a repeater. The data is sends in frame with the receiver's station address onto the network through repeaters. The frame will circulate on the ring and the receiver station will identify its address and copies the frames. The frame will keep on circulate until it reaches back to the sender's station and then removed. Therefore, the ring network does not require terminators.
The advantages of the ring topology are cable failures are easy to found and equal access for every node. Since the signal on the networking is on one direction, it easy to track the failure cable. Every node is given equal access to the token, and no one node can dominate the network. The token is like a ticket travels around on the ring network to grant each station the permission of insert frames. Any one station has the token, it able to sends frames.
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The disadvantages of this topology are the connection will be interrupted when adding or removing nodes. In case of failure of any station, repeater, or cable, the whole network will be shut down and no connection service until it is replaces or fixed.
In star topology, each node connected directly to the common central node, called the hub. This network physically star-shape like when looks form the top. Each node connected to the hub view two point-to-point links, which one for sending and another for receiving. Every data on the star network must passes through the hub before reaches the destination node. The hub may act as a switcher, concentrator manager, or an repeater.
The hub could run the either of two different operations, which is broadcasting or switching. In the broadcasting manner, the frame that received by a hub from a node is retransmitted to all other nodes. Thus, the other nodes are able to receive the frame as well. In this manner, the transmission from a node is only allows once at a time. For switching operation, the frame that received form a node is retransmitted by a hub to the destination node only.
The advantages of the star topology are easier to make changes and add new nodes without affecting the whole network functionalities. It is easy to control the data traffic and data flow through a concentrator manager. Failures on this network could be easily found and repairs. Failures of any node do not affect the whole network functionalities or network down would not down.
The disadvantages of this topology are the whole network functionalities is highly depending on the central hub. Therefore, if the central hub fails, the whole network will collapse. The network only functions until the hub is replaced or fixed. The scalabilities of this network are very low depending on the hub's capabilities. There is limitation on number of nodes that could be connected to the central hub. The whole network performance will drop down is too much of nodes connected and/or the cables are too long. A node may dominate the whole connection on the star network, and again decreases the connection performance for the other connected nodes.
A tree topology, also known as hierarchical network, is the combination of bus and star topologies. Hubs are connected directly to the tree bus (backbone), and each hubs act as the root of tree that connected the nodes or another hubs that could be connected by the other nodes as well. The tree topology could be expended to even more roots deepening on the hubs capabilities.
The advantages of the tree topology are higher expandability than other topologies. This network is supported by many network vendors and hardware vendors. Therefore, replacement of physical connection media could be easily brought. Point-to-point links are also able to implement on this topology, which allows rapid data transfers between specific nodes.
The disadvantages of this topology are if the tree bus breaks down, the entire network connection will be shut down. Besides, the configuration and wiring system of this topology is much complex than other topology.
In mesh topology, each node on the networks is connected to each other. The routers play important role in this network. The message sent by source node onto the network is route by the routers to the destination node through shortest distance. If all the nodes are fully connected to each other, it called full mesh topology, while the nodes are connected indirectly, it called partial mesh topology.
The advantages of the mesh topology are higher bandwidth and performance, since all the nodes are connected directly. The connections on the network will not break down if any of the nodes fails. The failures on the network are easy to be detected and isolated.
The disadvantages of this topology are sophisticated installation and the costliest topology compared with other topologies, due to its redundant wire links. Another disadvantage is, it will be much difficulty to reconfigure the network system.
Topologies are the basic of computer networks design and each of them has its own strengths and weaknesses. In order to build an efficient network, a complete knowledge of topologies and understating is required. With the knowledge of topologies, helps decides the best option for the network requirements. Furthermore, it helps built up a network cost-efficiently. Choosing the inappropriate topology will just lead to waste of time, resources, and efforts.
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According to question 1, I would like to recommend the group of business employees to build up a small networking office based on star topology. The reason I chose this topology is the cost of physical media and installation is inexpensive, so helps them to lower the budget. Another reason is if any one of the node failed, it will not affect the entire star network connection. Thus, it will not affect their daily business operation and decreases the lost of profits while not wastes time for repairing. Star topology enables to control the data traffic and data flow by using concentrator manager, to ensure no one node can dominate the network connection for a long period of time. Thus, provides equal access to network connection for every employee and avoid heavy network traffic. Besides, failures on the star network are easy to track. Hence, save the time for troubleshooting. Yet again, maintains or repairs any nodes would not affect the whole network connection.
The main disadvantage of the star topology is if the hub failed, the entire network will be shut down and there will be no connection until the hub has been repaired or replaced. This could bring a huge affect for the daily business operation, like lost of profits while wasting time for repairing the hub. To avoid or minimize the lost of the business, I would like to suggest the business group to buy and store some replacements for the hub in the store room or any convenient place. In case of the hub failed, they can replace the hub as fast as possible and allows the business operation continue running as usual.