User Guide

CTI 2572 Technical Overview Manual
22
5.2 Internet Protocol
Internet Protocol (IP) provides a basic packet delivery service. Technically, this service is
defined as unreliable, connectionless, and best-effort. Unreliable means that delivery is not
guaranteed by the protocol. The packet may be lost, duplicated, delayed, or delivered out of
order. Connectionless, as defined previously, means that each packet is treated independently of
all others. Finally, best-effort means that IP software makes an earnest attempt to deliver packets
and does not discard packets capriciously.
IP defines the structure of the unit of data
transfer, called an internet datagram. IP
also defines the rules and procedures for
routing datagrams, how and when error
messages should be generated, and the
conditions under which a packet will be
discarded. The datagram consists of an IP
header and the data from the upper layer
protocol. Fields in the datagram header
contain control information and the IP
address of both the source and the
destination node.
IP Address
An IP address is a 32 bit field which uniquely identifies the network and the host computer node.
The IP address is conceptually divided into four 8 bit bytes (called octets in some technical
publications). An IP address is usually expressed in dotted notation, with one byte expressed as
its decimal equivalent. For example, an address containing all 1’s would be notated
255.255.255.255 (see below).
Notation Byte 1 Byte 2 Byte 3 Byte 4
Binary 11111111 11111111 11111111 11111111
Decimal 255 255 255 255
ETHERNET
HEADER
IP CONTROL
INFORMATION
IP
SOURCE
ADDRESS
ETHERNET
TRAILER
IP
HEADER
DATA
IP
DESTINATION
ADDRESS
IP DATAGRAM
IP
OPTIONS
DATA
Figure 12 Datagram