Internet subnets (RFC0917)
Original Publication Date: 1984-Oct-01
Included in the Prior Art Database: 2000-Oct-06
Internet Society Requests For Comment (RFCs)
The original view of the Internet universe was a two-level hierarchy: the top level the catenet as a whole, and the level below it a collection of "Internet Networks", each with its own Network Number. (We do not mean that the Internet has a hierarchical topology, but that the interpretation of addresses is hierarchical.)
Network Working Group Jeffrey Mogul
Request for Comments: 917 Computer Science Department
Status Of This Memo
This RFC suggests a proposed protocol for the ARPA-Internet
community, and requests discussion and suggestions for improvements.
Distribution of this memo is unlimited.
We discuss the utility of "subnets" of Internet networks, which are
logically visible sub-sections of a single Internet network. For
administrative or technical reasons, many organizations have chosen
to divide one Internet network into several subnets, instead of
acquiring a set of Internet network numbers.
We propose procedures for the use of subnets, and discuss approaches
to solving the problems that arise, particularly that of routing.
This proposal is the result of discussion with several other people.
J. Noel Chiappa, Chris Kent, and Tim Mann, in particular, provided
The original view of the Internet universe was a two-level hierarchy:
the top level the catenet as a whole, and the level below it a
collection of "Internet Networks", each with its own Network Number.
(We do not mean that the Internet has a hierarchical topology, but
that the interpretation of addresses is hierarchical.)
While this view has proved simple and powerful, a number of
organizations have found it inadequate and have added a third level
to the interpretation of Internet addresses. In this view, a given
Internet Network might (or might not) be divided into a collection of
The original, two-level, view carries a strong presumption that, to a
host on an Internet network, that network may be viewed as a single
edge; to put it another way, the network may be treated as a "black
box" to which a set of hosts is connected. This is true of the
RFC 917 October 1984
ARPANET, because the IMPs mask the use of specific links in that
network. It is also true of most local area network (LAN)
technologies, such as Ethernet or ring networks.
However, this presumption fails in many practical cases, because in
moderately large organizations (e.g., Universities or companies with
more than one building) it is often necessary to use more than one
LAN cable to cover a "local area". For example, at this writing
there are eighteen such cables in use at Stanford University, with
There are several reasons why an organization might use more than one
cable to cover a campus:
- Different technologies: Especially in a research environment,
there may be more than one kind of LAN in use; e.g., an
organization may have some equipment that suppo...