UDP - User Datagram Protocol

We know that the TCP/IP suite of protocols offers two protocols at the transport layer. The first one is Transmission Control Protocol (TCP)and other protocol in layer is User Datagram Protocol (UDP).

TCP, UDP is a connectionless protocol. UDP allows computers to send data without feeding a virtual connection. Since there is no error checking involved here, UDP is simpler than does not provide for any acknowledgement, sequencing or reordering mechanisms. Thus, UDP packets may be lost, duplicated or arrive out of order at the destination. UDP contains very primitive of error checking (such as checksums). The UDP packets are not numbered, unlike TCP. Thus, even when multiple UDP packets are sent by the same source to the same destination, each packet is completely independent of all previous UDP packets. Since there is no connection between the sender and the destination, the path taken by a UDP packet cannot be predicted.

It is left to the application program that uses UDP to accept the full responsibility of handling such as reliability, including data loss, duplication, delay and loss of connection. Clearly, this is a good idea for every application program to perform these checks, when a reliable data transmission such as TCP is available. However, when the speed of delivery is more important than 'ability of data, UDP is preferred to TCP. For instance, in voice and video transmissions, it is light to lose a few bits of information, than sending every bit correctly at the cost of transmission speed. such a situation, UDP would be a better choice. In contrast, computer data transmission must be very reliable. Therefore, for transferring computer data such as files and messages, TCP is used.

UDP PACKET

UDP packets are also known as user . Each UDP packet has a fixed 8 byte header that is sub divided into four fields, each of two This is followed by the actual data to be transmitted using this UDP packet.
Let us briefly examine the fields in the UDP packet header.

Source port number: This is the port number corresponding to the application running on, source computer. Since it can take up to two bytes, it means that a source port number between 0 and 65,535.

Destination port number: This is the port number corresponding to the application running on destination computer. Since it can also take up to two bytes, it means that a destination port number can also be between 0 and 65,535.

Total packet length: This 2 byte field defines the total length of the UDP packet, i.e. header data. Actually, this field is not required at all, because there is a similar packet length field in packet, which encapsulates a UDP packet inside it before sending it to the destination. There the following equation is always true:

UDP packet length = IP packet length IP header length However, this field is retained in the UDP packet header as an additional check

Checksum: This field is used for error detection and correction, as usual.

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