UDP(User Datagram Protocol)
Introduction
IN the TCP/IP protocol suite, the User Datagram Protocol or UDP allow a
application progarm
to send datagram to other aplication program on the
remote machine[1]. Basically UDP is an
unreliable datagram service;
delivery and duplicate detection are not guaranteed[2]. UDP uses IP
to transport a message between the machiness. It is connectionless and
unreliable; It dose not uses
acknowlegements, or control the order of
arrival, or flow control. So UDP message can be lost.[3]
In the protocol layering scheme, UDP lies in the transport layer, above IP
and below the application layer. Usually IP layer is only resposible for
transferring data on an internet. UDP layer is reponsible only for identifing
the source or destination ports within a host.
All Multiplexing and demuliplexing are based on protocol ports by UDP.
Protocol ports are set of abstract destination points that each machine
contains
Applications and protocols which use UDP:[4]
Format of UDP Messages
The format of UDP Messages is as the following:
UDP mesage provides:[5]
- Source Port - 16 bit port number
- Destination Port - 16 bit port number
- Length (of UDP header + data) - 16 bit count of octets in the UDP datagram
- UDP checksum - 16 bit field - if 0, then there is no checksum, else it is
a checksum over a pseudo header + UDP data area
UDP uses a pseudo-header to verify that the UDP message has arrived at both
the correct machine and the correct port. UDP pseudo-header consists of
the source and destination IP address. UDP pseudo-header shows as the follows:
- Proto : IP protocol type code.
- UDP length : Length of the UDP datagram.
References
[1]The User
Datagram Protocol(*****)
[2]User Datagram Protocol (UDP)(*****)
[3]RFC 768(*****)
[4]User Datagram Protocol(*****)
[5]User Datagram Protocol (UDP)(*****)
Further Information
[6] TCP an d UDP transport(****)
[7]udp(****)
[8]An introduction to TCP/IP Programming(***)
[9]Transport Protocols(****)
[10]Higer layer protocols(****)
[11]TCP/IP(*****)
[12]User Datagram Protocol(*****)
[13]Navigational information for ``The User Datagram Protocol''(*****)
[14]The Glossary of Telecommunications and Internetworking Terms(****)
[15]Network Working Group(****)
[16]TCP and UDP Port Structure(****)
[17]User Datagram Protocol(*****)
[18]Firewalls.9504: UDP(*****)
[19]UDP Transport Lecture(*****)
[20]
UDP Broadcast Flooding(***)
Question
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This page was written by Tao Lu (student number:45141u).