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The TCP/IP Guide  9  TCP/IP Application Layer Protocols, Services and Applications (OSI Layers 5, 6 and 7)       9  TCP/IP Network Configuration and Management Protocols (BOOTP, DHCP, SNMP and RMON)            9  Host Configuration and TCP/IP Host Configuration Protocols (BOOTP and DHCP)

BOOTP Relay Agents (Forwarding Agents) 1 DHCP Overview, Motivation, History and Standards

In some ways, technological advancement can be considered more a journey than a destination. When a particular technology is refined or replaced with a superior one, it's usually only a matter of time before it too is replaced with something better. And so it was with the TCP/IP Boot Protocol. While BOOTP was far more capable than the protocol it replaced (RARP), after a number of years BOOTP itself was replaced with a new TCP/IP configuration protocol: the Dynamic Host Configuration Protocol (DHCP).

Where BOOTP represented a revolutionary change from RARP, DHCP is more of an evolution of BOOTP. It was built using BOOTP as a foundation, with the same basic message format. The most significant addition in DHCP is the ability to dynamically assign addresses to clients and to centrally manage them. It is this capability that both gives DHCP its name, and makes it so powerful. DHCP today is the standard TCP/IP host configuration protocol and is used in everything from single-client home networks to enterprise-class internetworks.

In this section I describe the concepts behind DHCP and explain how it works in detail. I begin with a topic that provides an overview of the protocol, discussing its history and the standards that define it. I then have four subsections that describe DHCP concepts and operation. The first talks about the different ways DHCP can assign addresses, with a focus on dynamic addressing. The second discusses how DHCP operates, including a look at configuration parameter management and the procedures for allocating addresses and managing those allocations. The third describes DHCP messaging and illustrates the DHCP message format. The fourth gets into more of the details of DHCP clients and servers, and also looks at special features and issues with DHCP. Finally, I conclude with a topic describing how DHCP changes to support the new IP version 6.

BOOTP Relay Agents (Forwarding Agents) 1 DHCP Overview, Motivation, History and Standards