Transcript 25-UDP - UTRGV Faculty Web

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-toend 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.
Position of UDP in the TCP/IP protocol suite
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.
Well-known ports used with UDP
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.
User datagram format
Encapsulation and decapsulation