User's Manual

436 Features

Table 109

DHCP message types (cont’d.)

DHCP Message Types

Description

DHCPNAK Notifies client that requested parameters

cannot be met.

DHCPDECLINE Notifies server that offer is unsatisfactory and

will not be accepted.

DHCPRELEASE Notifies server that IP address is no longer

needed.

DHCP message format

The DHCP message format shown inFigure 76 "DHCP message format"

(page 436) is common to all DHCP messages. Each message consists

of 15 fields: 14 fixed-length fields and one variable length field. The

fixed-length fields must be the specified number of bytes, as indicated in

the brackets. If there is not enough data, or there is no data at all, zeros

are used to fill in the extra spaces.

Figure 76

DHCP message format

The Options field is the only field with a variable length. It is optional,

but very important, as it transports additional network configuration

parameters. The DHCP options are the actual subfields that are used in

this project.

DHCP message exchange

Nortel Communication Server 1000

IP Phones Fundamentals

NN43001-368 05.06 30 April 2010