Information Technology Reference
In-Depth Information
Table 8.1
Common port numbers
Port number
Description
20
FTP data
21
FTP control
23
Telnet
25
Simple Mail Transfer Protocol (SMTP)
53
Domain Name System (DNS)
80
Hypertext Transfer Protocol (HTTP), Web
88
Kerberos
110
Post Office Protocol v3 (POP3)
443
Secure HTTP (HTTPS)
Understanding IP Addressing
Understanding IP addressing is critical to understanding how IP works. An IP address is
a numeric identifier assigned to each device on an IP network. This type of address is a
logical software address that designates the device's location on the network. It isn't the
physical hardware address hard-coded in the device's network interface card.
In the following sections, you will see how IP addresses are used to identify uniquely
every machine on the network (MAC address).
The Hierarchical IP Addressing Scheme
An IP address consists of 32 bits of information. These bits are divided into four sections
(sometimes called
octets
or
quads
) containing 1 byte (8 bits) each. There are three common
methods for specifying an IP address:
■
Dotted-decimal, as in 130.57.30.56
■
Binary, as in 10000010.00111001.00011110.00111000
■
Hexadecimal, as in 82 39 1E 38
All of these examples represent the same IP address.
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