Which of the following statements about UDP are correct? UDP has a checksum to d

Question

Which of the following statements about UDP are correct? UDP has a checksum to detect bit errors, but it is not always used by the applications using UDP. UDP has a retransmission mechanism to deal with packet loss, but it is not always used by the applications using UDP. UDP does not have any mechanisms to deal with congestion. UDP leaves it up to the application to decided how to deal with packet loss and bit errors. If a client sends two messages to a server, UDP will guarantee that they arrive in the correct order. UDP guarantees that all UDP packets between a sending and receiving process take the same path through the network.

Explanation / Answer

1. UDP has an optional checksum.It will detect any single bit error, but if the packet is altered such that the sum of all the data as 16 bit values remains constant, the checksum will not detect the error.The checksum is optional under IPv4,because the Data-Link layer checksum provides the desired level of error protection.

2.UDP is not having any build-in retransmission mechanism to deal with packet loss.It is an unreliable,connectionless protocol.We wont be able to see the packet loss.There is no guarantee of delivery.

3.UDP is not having congestion control mechanism.When UDP data are sent in a network, there is no requirement for the UDP data rates to back off.Packets are sent without some sort of flow control, this results in flooding the connection and inducing severe latency as routers become congested.Ther is no ACKs, so the network cannot signal congestion to the sender.

4.UDP leaves to the application to decide how to deal with retransmission and bit error.UDP ia a connectionless and unreliable protocol.It will just send the packets to the destination.The receiver has to detect whether there is a packet loss or not and can check whether packet delivered is having any errors.According to it they can ask the sender to retransmit the packets.

5.UDP does not guarantee that the packets arrives in order.It does not even guarantee that the packets will arrive. UDP does not insert sequence numbers. The packets are expected to arrive as a continuous stream or they are dropped.

6.UDP packets always follow the same path. UDP packets are used for realtime media streams such as phone calls,if the voice packets arrive out of order, this results in terrible audio quality.

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