tailieunhanh - User Datagram Protocol (UDP)

User Datagram Protocol (UDP) UDP is the polar opposite of TCP. Whereas TCP is connection oriented, reliable, and relatively complex, UDP is a connectionless, unreliable | User Datagram Protocol UDP UDP is the polar opposite of TCP. Whereas TCP is connection oriented reliable and relatively complex UDP is a connectionless unreliable and a relatively simple protocol. The initial response might be to ask Why use an unreliable protocol To understand this you need to have the proper perspective of what we mean by unreliable. Unreliable does not mean that it will not work or that the data will not get delivered. Indeed when using unreliable protocols such as UDP it is generally a safe bet that the data will be successfully delivered. Why Because most networks today are designed to eliminate things such as latency and packet loss thus ensuring that data gets delivered regardless of what protocol is used. Consequently UDP was developed in large part to provide a simple low-overhead method of delivering data across the network. Yes UDP messages can be lost duplicated or sent out of order but in most cases on most networks they will not be. The reason that UDP is low overhead is because two UDP hosts do not establish a session prior to transmitting data and they do not periodically check to verify that the data was received as is done with TCP. This makes UDP an excellent choice for the transmission of small bursts of data or the transmission of data that handles reliability at the application layer. Some common applications that make use of this are things such as DNS TFTP and SNMP. Like TCP UDP uses port numbers to identify the higher-layer application or protocol from which the data came and for which it is destined. These port numbers are assigned and maintained by IANA which provides a full list of registered port numbers at http assignments port-numbers. Note RFC 0768 defines UDP. UDP Message Structure Because of the simplicity of the design of UDP the UDP segment structure is much simpler than the TCP segment structure. The UDP message contains two components the UDP header and the UDP data. The UDP header is merely 8 .