RFC 3527 (rfc3527) - Page 3 of 9

Link Selection sub-option for the Relay Agent Information Option for DHCPv4

RFC 3527               Link Selection sub-option              April 2003


2.  Terminology

   The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT",
   "SHOULD", "SHOULD NOT", "RECOMMENDED", "MAY", and "OPTIONAL" in this
   document are to be interpreted as described in BCP 14, RFC 2119 [RFC
   2119].

   This document uses the following terms:

      o  "DHCP client"

         A DHCP client is an Internet host using DHCP to obtain
         configuration parameters such as a network address.

      o  "DHCP relay agent"

         A DHCP relay agent is a third-party agent that transfers BOOTP
         and DHCP messages between clients and servers residing on
         different subnets, per [RFC 951] and [RFC 1542].

      o  "DHCP server"

         A DHCP server is an Internet host that returns configuration
         parameters to DHCP clients.

      o  "link"

         A link is a communications facility or medium over which nodes
         can communicate at the link layer, i.e., the layer immediately
         below IPv4.  Examples are Ethernets (simple or bridged); PPP
         links; X.25, Frame Relay, or ATM networks; and internet (or
         higher) layer "tunnels", such as tunnels over IPv4 or IPv6
         itself.

      o  "subnet"

         A subnet (for the purposes of this document) consists of a
         routable address range.  It may be one of several that exist on
         a link at the same time.

3.  Link selection sub-option definition

   The link-selection sub-option is used by any DHCP relay agent that
   desires to specify a subnet/link for a DHCP client request that it is
   relaying but needs the subnet/link specification to be different from
   the IP address the DHCP server should use when communicating with the
   relay agent.




Kinnear, et al.             Standards Track