RFC 1256 (rfc1256) - Page 2 of 19

ICMP Router Discovery Messages

RFC 1256             ICMP Router Discovery Messages       September 1991


                 in [2].  This does not include systems that, though
                 capable of IP forwarding, have that capability turned
                 off.  Nor does it include systems that do IP forwarding
                 only insofar as required to obey IP Source Route
                 options.

   host          any system that is not a router.

   multicast     unless otherwise qualified, means the use of either IP
                 multicast [4] or IP broadcast [6] service.

   link          a communication facility or medium over which systems
                 can communicate at the link layer, i.e., the protocol
                 layer immediately below IP.  The term "physical
                 network" has sometimes been used (imprecisely) for
                 this. Examples of links are LANs (possibly bridged to
                 other LANs), wide-area store-and-forward networks,
                 satellite channels, and point-to-point links.

   multicast link
                 a link over which IP multicast or IP broadcast service
                 is supported.  This includes broadcast media such as
                 LANs and satellite channels, single point-to-point
                 links, and some store-and-forward networks such as SMDS
                 networks [8].

   interface     a system's attachment point to a link.  It is possible
                 (though unusual) for a system to have more than one
                 interface to the same link.  Interfaces are uniquely
                 identified by IP unicast addresses; a single interface
                 may have more than one such address.

   multicast interface
                 an interface to a multicast link, that is, an interface
                 to a link over which IP multicast or IP broadcast
                 service is supported.

   subnet        either a single subnet of a subnetted IP network [7] or
                 a single non-subnetted IP network, i.e., the entity
                 identified by an IP address logically ANDed with its
                 assigned subnet mask.  More than one subnet may exist
                 on the same link.

   neighboring   having an IP address belonging to the same subnet.







Router Discovery Working Group