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14
N
ETWORKING
C
ONCEPTS
This appendix contains the following:
■
Introduction to TCP/IP
■
Network Address Translation (NAT)
■
Dynamic Host Configuration Protocol (DHCP)
■
Port Numbers
■
Virtual Private Network Services
Introduction to
TCP/IP
Protocols are rules that networking hardware and software follow to
communicate with one another. The Firewall uses the TCP/IP protocol.
IP and TCP IP stands for Internet Protocol. This protocol provides connectionless data
transfer over a TCP/IP network. Because IP alone does not provide
end-to-end data reliability as well as some other services, other protocols
such as TCP can be added to provide these services. TCP stands for
Transmission Control Protocol. In TCP/IP, TCP works with IP to ensure the
integrity of the data traveling over the network. TCP/IP is the protocol of
the Internet.
IP Addressing To become part of an IP network, a network device must have an IP
address. An IP address is a unique number that differentiates one device
from another on the network to avoid confusion during communication.
To help illustrate IP addresses, the following sections compare an IP
address to the telephone numbering system, a system that is used every
day.
Like a phone number with a long distance number and area code, an IP
address contains a set of four numbers. Where the components in phone
numbers can be separated with dashes, for example,
1-408-555-1212
, IP
address number components are separated by decimal points or dots
DUA1611-0AAA02.book Page 179 Thursday, August 2, 2001 4:01 PM