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Figure 2-13. 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.
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 VH-2402-L3 must be used.
The DNS servers are identified by IP addresses.
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