All data being transferred is in packets. It is a unit of data that has the ability to be routed over network(s). It usually has 3 parts: the header, the body or payload and the footer/trailer. The header contains details such as the destination IP, the host IP & host MAC address. The body contains the actual data or part of the data to be transferred and lastly the footer signifies the end of the packet and also contains the packet number. Why can the data transmission rate across a network vary? Data transmission rate across a network can vary for several reasons.

Some are given low: 1) The transmission media: The transmission media used to transmit the data across a network Is an Important factor that can Limit the transmission rate. If a fast medium such as fiber optic cables are used then the transmission will be faster. However if a slower medium such as telephone cables are used then obviously the transmission will be slower. 2) The level of activity on the network is also a important factor. The network is limited by the amount of data it can transmit at a point in time.

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This Is called the bandwidth. Thus if the level of activity on the network Is very high r exceeding the allowed bandwidth, then any further data to be transmitted will have to wait/ be queued. 3) collisions on the .NET;ark can also determine the rate of data transfer. Whenever a data collision occurs, a jamming signal will need to sent from the sender to receiver and then the data will need to resent. This will take more time. Thus the greater number of collisions, the longer the data transfer will take.

Why Is compression of data often necessary when transmitting across a network? Networks are Limited to how much data they can transmit at a particular time. This Is now as the network bandwidth. Thus in order to transfer very large files across the network, the d ACTA/files need to made as small as possible so that they take up as little bandwidth when being transferred. This "making small" of files/data is done by compression and this is why compression is often necessary - to reduce the amount of bandwidth being used. Edie differ from each other significantly in terms of both the physical transfer medium as well as the rate of data transfer. Some of the common transmission media are: 1) Telephone Lines: This is when data, voice and video are transferred ever the standard telephone line using a set of copper wires. They require a modem to allow communicate. Since data is transferred over a telephone wire, there is a very little data can be transferred at a given time. Thus it suffers from narrow bandwidth and slow transmission times. ) Twisted Pair: This is a type of cable which usually uses a 16 coppers wires twisted together in pairs to transmit the data. This offers a greater bandwidth and higher transmission rate than the regular telephone wire but is slower than fiber optic. This also requires a modem for communication. 3) Wireless: This is method to transmit data using wireless technology. Since this uses such technology a different type of network card is needed called as the Wireless Network Interface Card.

This allows data transfer without the need of a physical connection. However the disadvantage is that transmission rates are slower than cable as the wireless signals can be affected by radio waves, etc. This also tends to less secure than a physical connection as anyone with a Wireless NICE can connect to the network if it is not secure. 4) Fiber Optic: This is another type of physical medium ever which data can be transferred. This first converts data from the digital format to the optical format (pulses of light) by using a special modem.

The data is then beamed through think bundles of glass tubes to allow the transfer to take place. Since the data is traveling at the speed of light the data transfer is extremely fast and there is relatively very less chances of errors occurring. However this type of technology is expensive and tends to be only used in Hick who can afford them. Explain how data is transmitted by packet switching? Packet switching sends data in individual groups called data packets. A single data transmission is broken up into individual packets and then each packet is transmitted.

The key feature is that the individual packets need not be transmitted over the same links, but can be sent over the best available link. The original data transmission that was broken up into packets is then reassembled at the destination. The re-ordering is possible because each packet has a separate packet number. Thus the packets can be re-ordered according to this packet number. The main advantage is that if a link is broken or unavailable during transmission another link can be used ND the transmission can continue.

Packet switching is suitable when small delays can be tolerated e. G. Email transmission as compared to real-time video where it is important that there is no delay in either the sound or pictures. Packet switching is also suitable where data transmission is not a constant stream or rather where there is a burst of data transmission and then some idle time before another burst. During the idle time the network link can be used to handle another transfer. The advantage is that it can be fast, but subject to failure if a link is broken during transmission.