RFC 922 (rfc922) - Page 2 of 12
Broadcasting Internet datagrams in the presence of subnets
Alternative Format: Original Text Document
RFC 922 October 1984 Broadcasting Internet Datagrams in the Presence of Subnets When a datagram is broadcast, it imposes a cost on every host that hears it. Therefore, broadcasting should not be used indiscriminately, but rather only when it is the best solution to a problem. 2. Terminology Because broadcasting depends on the specific data link layer in use on a local network, we must discuss it with reference to both physical networks and logical networks. The terms we will use in referring to physical networks are, from the point of view of the host sending or forwarding a broadcast: Local Hardware Network The physical link to which the host is attached. Remote Hardware Network A physical network which is separated from the host by at least one gateway. Collection of Hardware Networks A set of hardware networks (transitively) connected by gateways. The IP world includes several kinds of logical network. To avoid ambiguity, we will use the following terms: Internet The DARPA Internet collection of IP networks. IP Network One or a collection of several hardware networks that have one specific IP network number. Subnet A single member of the collection of hardware networks that compose an IP network. Host addresses on a given subnet share an IP network number with hosts on all other subnets of that IP network, but the local-address part is divided into subnet-number Mogul
