Network Working Group                          Internet Architecture Board
Request for Comments: 1370                             Lyman Chapin, Chair
                                                              October 1992


                    Applicability Statement for OSPF

Status of this Memo

   This memo is an IAB standards track Applicability Statement for the
   Internet community, and requests discussion and suggestions for
   improvements.  Please refer to the current edition of the "IAB
   Official Protocol Standards" for the standardization state and status
   of this specification.  Distribution of this memo is unlimited.

1. INTRODUCTION

   Users and vendors have expressed a strong need for IP routers from
   different vendors that can interoperate using a common Interior
   Gateway Protocol (IGP).  There is therefore an urgent requirement for
   a high-functionality non-proprietary 'open' IGP that will be
   ubiquitously available from all IP router vendors.

   The Open Shortest Path First (OSPF) routing protocol [1] was
   developed by the IETF to fill this need.  This Applicability
   Statement specifies the circumstances under which OSPF must be
   implemented by router vendors.  The history of OSPF development and
   the reasoning behind this Applicability Statement will be found in
   [5].

   This Applicability Statement places a requirement on vendors claiming
   conformance to this standard, in order to assure that users will have
   the option of deploying OSPF when they need a multivendor,
   interoperable IGP in their environment.  Users are of course free to
   use whatever routing protocol best meets their requirements.

2.  APPLICABILITY OF OSPF

   An IP router that implements any routing protocol (other than static
   routes) is required to implement OSPF [1] and the OSPF MIB [2].
   Within OSPF, implementation of all features except TOS (Type-of-
   Service) routing is required; implementation of TOS routing is
   recommended.

   This requirement does not prevent a router from implementing other
   routing protocols in addition to OSPF.  Complete and definitive
   requirements on all aspects of an IP router will be found in a
   forthcoming Applicability Statement: "Requirements for IP Routers"



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RFC 1370             Applicability Statement: OSPF          October 1992


   [4], currently in preparation in the IETF.  "Requirements for IP
   Routers", when it becomes a Standard, will take precedence if its
   requirements for OSPF should conflict with this present RFC.

   It should be noted that OSPF is intended for use by routers for
   exchanging dynamic routing information, and not for use by hosts.  As
   discussed in Section 3.3.1.4 of STD-2, "Requirements for Internet
   Hosts -- Communication Layers" [3], 'wiretapping' of routing
   protocols by hosts is not recommended.  Recommended mechanisms for a
   host to use for discovering local routers and detecting dead routers
   will be found in [3].  In particular, the ICMP Router Discovery
   messages, under development, will provide a standard way for a host
   to learn the addresses of local routers [6].

3.  REFERENCES

   [1] Moy, J., "OSPF Version 2", RFC 1247, Proteon, Inc., July 1991.

   [2] Baker, F., and R. Coltun, "OSPF Version 2 Management Information
       Base", RFC 1253, ACC, Computer Science Center, August 1991.

   [3] Braden, R., Editor, "Requirements for Internet Hosts --
       Communication Layers", IETF, STD 3, RFC 1122, October 1989.

   [4] Almquist, P., Editor, "Requirements for IP Routers", Work in
       Preparation, IETF.

   [5] Gross, P., Editor, "Choosing a "Common IGP" for the IP Internet
       (The IESG's Recommendation to the IAB)", RFC 1371, IESG, October
       1992.

   [6] Deering, S., Editor, "ICMP Router Discovery Messages", RFC 1256,
       Xerox PARC, September 1991.

Security Considerations

   Security issues are not discussed in this memo.

Author's Address

   A. Lyman Chapin
   BBN Communications Corporation
   150 Cambridge Park Drive
   Cambridge, MA  02140

   Phone: 617-873-3133
   Fax:   617-873-4086
   Email: Lyman@BBN.COM



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