RFC 1716 (rfc1716) - Page 2 of 186

Towards Requirements for IP Routers

RFC 1716          Towards Requirements for IP Routers      November 1994


1.  INTRODUCTION

The goal of this work is to replace RFC-1009, Requirements for Internet
Gateways ([INTRO:1]) with a new document.

This memo is an intermediate step toward that goal. It defines and
discusses requirements for devices which perform the network layer
forwarding function of the Internet protocol suite.  The Internet
community usually refers to such devices as IP routers or simply
routers; The OSI community refers to such devices as intermediate
systems.  Many older Internet documents refer to these devices as
gateways, a name which more recently has largely passed out of favor to
avoid confusion with application gateways.

An IP router can be distinguished from other sorts of packet switching
devices in that a router examines the IP protocol header as part of the
switching process.  It generally has to modify the IP header and to
strip off and replace the Link Layer framing.

The authors of this memo recognize, as should its readers, that many
routers support multiple protocol suites, and that support for multiple
protocol suites will be required in increasingly large parts of the
Internet in the future.  This memo, however, does not attempt to specify
Internet requirements for protocol suites other than TCP/IP.

This document enumerates standard protocols that a router connected to
the Internet must use, and it incorporates by reference the RFCs and
other documents describing the current specifications for these
protocols.  It corrects errors in the referenced documents and adds
additional discussion and guidance for an implementor.

For each protocol, this final version of this memo also contains an
explicit set of requirements, recommendations, and options.  The reader
must understand that the list of requirements in this memo is incomplete
by itself; the complete set of requirements for an Internet protocol
router is primarily defined in the standard protocol specification
documents, with the corrections, amendments, and supplements contained
in this memo.

This memo should be read in conjunction with the Requirements for
Internet Hosts RFCs ([INTRO:2] and [INTRO:3]).  Internet hosts and
routers must both be capable of originating IP datagrams and receiving
IP datagrams destined for them.  The major distinction between Internet
hosts and routers is that routers are required to implement forwarding
algorithms and Internet hosts do not require forwarding capabilities.
Any Internet host acting as a router must adhere to the requirements
contained in the final version of this memo.


Almquist & Kastenholz