The Domain Name System - D-Link DES-3326SR User Manual

DES-3326SR Layer 3 Fast Ethernet Switch User's Guide
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 5-13. Ethernet 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 packet. ICMP does not, however use ports
because its messages are processed by the network software.

The Domain Name System

Computer users usually prefer to use text names for computers
they may want to open a connection with. Computers
themselves, require 32 bit IP addresses. Somewhere, a
database of network devices' text names and their
corresponding IP addresses must be maintained.
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