Dynamic Host Configuration Protocol

Configuration Parameters Delivery

The DHCP server is designed to supply DHCP clients with the configuration parameters defined in the Host Requirements RFCs (1122 and 1123).

The client queries the DHCP server to retrieve its configuration parameters. The client interface to the configuration parameters repository consists of protocol messages to request configuration parameters and responses from the server carrying the configuration parameters.

The server provides a persistent storage of network parameters for network clients. The model of DHCP persistent storage of a set of key-value pairs for each client, where the key is some unique identifier and the value contains the configuration parameters for the client.

The storage will therefore include a list of entries of the following type for each client host:

Not all of these parameters are required for a newly initialized client. A client and server may negotiate for the transmission of only those parameters required by the client or specific to a particular subnet. DHCP allows the configuration of client parameters not directly related to the IP protocol.

Not all clients require initialization of all possible parameters. Two techniques are used to reduce the number of parameters transmitted from the server to the client:

1. Most of the parameters have defaults defined in the Host Requirements RFCs (1122 and 1123). If the client receives no parameters from the server that override the defaults, a client uses those default values.
2. A client and server may negotiate for the transmission of only those parameters required by the client. The client will then include the parameter request list option in the requested message to notify the server which parameters he needs.

Quiz

1. Configuration parameters are:
   • Stored on a persistent storage device, requested by server.
   • Stored in a 'parameter request list', requested by client.
   • Stored on server, requested by client.

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