D-Link DES-3326 User Manual - page 105
DES-3326 Layer 3 Fast Ethernet Switch User’s Guide
Switch Management and Operating Concepts
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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.
Figure 5-15. UDP Packet Header
The UDP header is shorter than a TCP header. UDP also uses a
checksum to verify that data is received uncorrupted.
The Internet Control Message Protocol (ICMP) is also a simplified
protocol used for error messages and messages used by TCP/IP.
ICMP, like UDP, processes messages that will fit into a single