D-Link DES-3326 User Manual - The Domain Name System
24-port NWay Ethernet Switch User’s Guide
98
Switch Management and Operating Concepts
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 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.
The Domain Name System (DNS) is used to map names to IP
addresses throughout the Internet and has been adapted for use
within intranets.
For two DNS servers to communicate across different subnets,
the DNS Relay of the DES-3326 must be used. The DNS
servers are identified by IP addresses.
Mapping Domain Names to Addresses
Name-to-address translation is performed by a program called a
Name server. The client program is called a Name resolver. A
Name resolver may need to contact several Name servers to
translate a name to an address.