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25-UDP. Dr. John P. Abraham Professor UTPA. User Datagram Protocol. A Datagram transport service
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25-UDP Dr. John P. Abraham Professor UTPA
User Datagram Protocol • A Datagram transport service • IP alone can’t distinguish among multiple application programs running on a given host. Another words, once the datagram is delivered to the computer, how does the computer use it? Is it an email datagram? Is it a web datagram? • Transport layer protocols are known as end-to-end protocols (rather than host-to-host), because they deliver to the application on each end.
Features of UDP (thin protocol) • End-to-end • Connectionless • Message oriented. Programmers may choose a message size that produces datagrams that fit in a standard MTU (1400 to 1450 octets of data). • Best effort • Arbitrary interaction: allows an application to send to many other applications (1 to many), or many-to-1 or many-to-many, or 1 to 1. • Operating system independent.
UDP communication semantics • UDP uses IP to send messages, as such problems of IP are inherited. An application must be immune to these problems or programmers should take additional steps to handle these problems.
Endpoint identification with protocol numbers • Protocol port numbers (sockets) are independent of underlying operating system. Each computer that supports UDP must map port numbers and program identifiers that the OS uses.