The Dynamic Host Configuration Protocol (DHCP) is a protocol service that dynamically assigns an IP address to DHCP clients. It also has the additional duty of allocating Transmission Control Protocol/ Internet Protocol (TCP/IP) transmissions and control procedures to the different DHCP clients tethered to it, such as subnet mask information, default gateway IP address and other IP addresses. This service runs atop the application layer of the TCP/IP protocol stock that assigns multiple variables to the client computer’s TCP/IP information architecture, thus allowing it to connect to the server remotely and effectively. Derived from the BOOTstrap Protocol (BOOTP), this service also assigns WINS IP and Domain Name Server IP’s that control the domain IP translation services.
The Dynamic Host Configuration Protocol’s relay agent is an agent that remotely relays DHCP broadcast messages from the DHCP server to the DHCP client in different IP networks, establishing a systematic communications layer between the two nodes for effective data transmission especially when there is no mode of forwarding the DHCP broadcast messages to the router. If not properly configured, the DHCP client and server architecture will fail completely as the messages are dropped across the server resulting in a loss of data and communications.
DHCP relay agents are available for configuration on Windows NT, 2000 and Server 2003 servers. This entails the proper routing protocol information for DHCP transmission from client to server and perfect allocation of TCP/IP procedures.
The DHCP relay agent is simply a message transport system that trans-receives four basic types of data relay:-
* DHCPDISCOVER: Sent by the client at boot time to request an IP address on lease from the DHCP list. This is a broadcast message, i.e. public, for any one server to quickly assign an IP for the client.
* DHCPOFFER: Sent by one of the servers on a network to the client that sends the DHCPDISCOVER message – as an offer of an IP address.
* DHCPREQUEST: The client sends a request for a particular IP address on lease from the server or servers. Replied by a DHCPOFFER if available.
* DHCPACK: This is the acknowledgement message sent by the server to the client before administering the requisite IP address to the particular node and connecting it to the network.
All these data packets are sent via the DHCP relay agent which transports these messages back and forth to the router, client and server in the client server architecture.
