Udp And Icmp - D-Link DES-3326 User Manual

24-port NWay Ethernet Switch User's Guide

UDP and ICMP

There are many applications that do not require long messages
that cannot fit into a single packet. Looking up computer names
is an example. Users wanting to make connections to other
computers will usually use a name rather than the computer' s IP
or MAC address. The user' s computer must be able to determine
the remote computer' s address before a connection can be made.
A designated computer on the network will contain a database of
computer names and their corresponding IP and MAC addresses.
The user' s computer will send a query to the name database
computer, and the database computer will send a response. Both
the query and the response are very short. There is no need to
divide the query or response between multiple packets, so the
complexity of TCP is not required. If there is no response to the
query after a period of time, the query can simply be resent.
The User Datagram Protocol (UDP) is designed for
communications that do not require division among multiple
packets and subsequent reassembly. UDP does not keep track of
what is sent.
UDP uses port numbers in a way that is directly analogous to
TCP. There are well-known UDP port numbers for servers that
use UDP.
Switch Management and Operating Concepts
97