Tiêu đề unit-4.pdf ✅

UDP Protocol UDP provides connectionless, unreliable, datagram service. Connectionless service means that there is no logical connection between the two ends exchanging messages. Each message is an independent entity encapsulated in a datagram. UDP does not see any relation (connection) between consequent datagram coming from the samesource and going to the same destination. UDP has an advantage: it is message-oriented. It gives boundaries to the messages exchanged. An application program may be designed to use UDP if it is sending small messages and the simplicity and speed is more important for the application than reliability. User Datagram UDP packets, called user datagram, have a fixed-size header of 8 bytes made of four fields, eachof 2 bytes (16 bits). . The 16 bits can define a total length of 0 to 65,535 bytes. However, the total length needs to be less because a UDP user datagram is stored in an IP datagram with the total length of 65,535 bytes. The last field can carry the optional checksum UDP Services Process-to-Process Communication UDP provides process-to-process communication using socket addresses, a combination of IP addresses and port numbers.
Connectionless Services As mentioned previously, UDP provides a connection less service. This means that each user datagram sent by UDP is an independent datagram. There is no relationship between the different user data grams even if they are coming from the same source process and going to the same destination program. Flow Control UDP is a very simple protocol. There is no flow control, and hence no window mechanism.The receiver may overflow with incoming messages. Error Control There is no error control mechanism in UDP except for the checksum. This means thatthe sender does not know if a message has been lost or duplicated. Checksum UDP checksum calculation includes three sections: a pseudo header, the UDP header, and the data coming from the application layer. The pseudo header is the part of the header of the IP packet in which the user datagram is to be encapsulated with some fields filled with 0s UDP Applications UDP Features Connectionless Service As we mentioned previously, UDP is a connectionless protocol. Each UDP packet is independent from other packetssent by the same application program. This feature can be considered as an advantage or disadvanta8e depending on the application requirements.