Question

Post a one paragraph summary about how errors in the transmission could affect the quality of the data sent through a network, and give an example of how those errors could affect you in your activities or place of work ( Pls dont copy from the internet and i want it typed pls No hand written bec i cant read it )

Answer 1

Error occur when the bits from the physical layer are misplaced or grabbed during transmission, or when there is hardware malfunctioning that result in the lost of frames.How to make sure all frames are eventually delivered to the network layer at the destination and in the proper orderd. Suppose that the sender just kept outputting frames without regard to whether they were arriving properly. This might be fine for unacknowledged connectionless service, but would most certainly not be fine for reliable, connection-oriented service. The usual way to ensure reliable delivery is to provide the sender with some feedback about what is happening at the other end of the line. Typically,the protocol calls for the receiver to send back special control frames bearing positive or negative acknowledgement about a frame, it knows the frame has arrived safely. On the other hand, a negative acknowledgement means that something has gone wrong, and the frame must be transmitted again. An additional complication comes from the possibililty that hardware troubles may cause a frame to vanish completely (e.g. in a noise burst). In this case, the receiver will not react at all, since it has no reason to react. It should be clear that a protocol in which the sender transmits a frame and then waits for an acknoledgement, positive or negative, will hang forever if a frame is ever lost due to, for example malfunctioning hardware.

This possibility is dealt with by introducing timers into the data link layer. When the sender transmits a frame, it generally also starts a timer. The timer is set to expire after an interval long enough for the frame to reach the destination, be processed there and have the acknowlegement propagate back to the sender. Normally, the frame will be correctly received and the acknowledgement will get back before the timer runs out, in which case the timer will be canceled. However, if either the frame or the acknowledgement is lost, the timer will go off, alerting the sender to a potetial problem. The obvious solution is to just transmit the frame again. However, when frames may be transmitted multiple times there is a danger that the receiver will accept the same frame two or more times and pass it to the network layer more than once. To prevent this from happening, it is generally necessary to assign sequence numbers to outgoing frames, so that the receiver can distinguish retransmissions from originals.

Example: When employee was sending information too quickly for a sever computer to store a file being uploaded, the server might run out of memory to store the file. At that time the sent data frames will losted and can't be restored the employee thinks that the information was uploaded to the server machine.