This is the support for the normal startup process. The DHCP client system boots up, and very early in the booting process it finds DHCP servers, selects one of the DHCP servers to be its server, queries that server to obtain a variety of information, and continues DHCP client self-configuration using the results of that query. DHCP servers may optionally provide a variety of information, such as server locations, normal routes. This transaction identifies what information shall be provided by a compliant DHCP server, and identifies what information shall be requested by a compliant DHCP client. A compliant DHCP server in not required to provide this optional information.
Figure F.1-4 Find and Use DHCP Server
Actor: DHCP Server
Role: Responds to DHCP acquisition queries. Multiple actors may exist. The DHCP client will select one.
Actor: DHCP client
Role: Queries for DHCP Servers. Selects one responding server.
RFC-2131 DHCP Protocol
RFC-2132 DHCP Options
RFC-2563 Auto Configuration control
Figure F.1-5 DHCP Interactions
The DHCP client shall comply with RFC-2131 (DHCP Protocol), RFC-2132 (DHCP Options), RFC-2563 (Auto Configuration Control), and their referenced RFCs.
The DHCP client shall query for available DHCP servers. It shall select the DHCP server to use.
The DHCP client shall query for an IP assignment. The DHCP Server shall determine the IP parameters in accordance with the current DHCP configuration, establish a lease for these parameters, and respond with this information. (See below for lease maintenance and expiration.) The DHCP client shall apply these parameters to the TCP/IP stack. The DHCP client shall establish internal lease maintenance activities.
The DHCP client shall query for the optional information listed in Table F.1-2 when required by additional profiles used by the client system. If the DHCP server does not provide this information, the default values shall be used by the DHCP client.
Table F.1-2 DHCP Parameters
|NTP||List of NTP servers||Empty list|
|DNS||List of DNS servers||Empty list|
|Router||Default router||Empty list|
|Hostname||Requested machine name|
|Subnet mask||Derived from network value|
|Broadcast address||Derived from network value|
|Time offset||Site configurable|
|Auto-IP permission||From NVRAM|
The DHCP client shall make this information available for other actors within the DHCP client machine.