OSPF Hybrid Broadcast and Point-to-Multipoint Interface Type
RFC 6845

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Internet Engineering Task Force (IETF)                          N. Sheth
Request for Comments: 6845                              Contrail Systems
Updates: 2328, 5340                                              L. Wang
Category: Standards Track                                       J. Zhang
ISSN: 2070-1721                                         Juniper Networks
                                                            January 2013

      OSPF Hybrid Broadcast and Point-to-Multipoint Interface Type

Abstract

   This document describes a mechanism to model a broadcast network as a
   hybrid of broadcast and point-to-multipoint networks for purposes of
   OSPF operation.  Neighbor discovery and maintenance as well as Link
   State Advertisement (LSA) database synchronization are performed
   using the broadcast model, but the network is represented using the
   point-to-multipoint model in the router-LSAs of the routers connected
   to it.  This allows an accurate representation of the cost of
   communication between different routers on the network, while
   maintaining the network efficiency of broadcast operation.  This
   approach is relatively simple and requires minimal changes to OSPF.

   This document updates both OSPFv2 (RFC 2328) and OSPFv3 (RFC 5340).

Status of This Memo

   This is an Internet Standards Track document.

   This document is a product of the Internet Engineering Task Force
   (IETF).  It represents the consensus of the IETF community.  It has
   received public review and has been approved for publication by the
   Internet Engineering Steering Group (IESG).  Further information on
   Internet Standards is available in Section 2 of RFC 5741.

   Information about the current status of this document, any errata,
   and how to provide feedback on it may be obtained at
   http://www.rfc-editor.org/info/rfc6845.

Sheth, et al.                Standards Track                    [Page 1]
RFC 6845        OSPF Hybrid Broadcast and P2MP Intf Type    January 2013

Copyright Notice

   Copyright (c) 2013 IETF Trust and the persons identified as the
   document authors.  All rights reserved.

   This document is subject to BCP 78 and the IETF Trust's Legal
   Provisions Relating to IETF Documents
   (http://trustee.ietf.org/license-info) in effect on the date of
   publication of this document.  Please review these documents
   carefully, as they describe your rights and restrictions with respect
   to this document.  Code Components extracted from this document must
   include Simplified BSD License text as described in Section 4.e of
   the Trust Legal Provisions and are provided without warranty as
   described in the Simplified BSD License.

Table of Contents

   1.  Introduction  . . . . . . . . . . . . . . . . . . . . . . . . . 3
   2.  Requirements Language . . . . . . . . . . . . . . . . . . . . . 3
   3.  Motivation  . . . . . . . . . . . . . . . . . . . . . . . . . . 3
   4.  Operation . . . . . . . . . . . . . . . . . . . . . . . . . . . 4
     4.1.  Interface Parameters  . . . . . . . . . . . . . . . . . . . 4
     4.2.  Neighbor Data Structure . . . . . . . . . . . . . . . . . . 4
     4.3.  Neighbor Discovery and Maintenance  . . . . . . . . . . . . 5
     4.4.  Database Synchronization  . . . . . . . . . . . . . . . . . 5
     4.5.  Generating Network-LSAs . . . . . . . . . . . . . . . . . . 5
     4.6.  Generating Router and Intra-Area-Prefix-LSAs  . . . . . . . 5
       4.6.1.  Stub Links in OSPFv2 Router-LSA . . . . . . . . . . . . 6
       4.6.2.  OSPFv3 Intra-Area-Prefix-LSA  . . . . . . . . . . . . . 6
     4.7.  Next-Hop Calculation  . . . . . . . . . . . . . . . . . . . 6
     4.8.  Graceful Restart  . . . . . . . . . . . . . . . . . . . . . 6
   5.  Compatibility Considerations  . . . . . . . . . . . . . . . . . 6
   6.  Scalability and Deployment Considerations . . . . . . . . . . . 7
   7.  Management Considerations . . . . . . . . . . . . . . . . . . . 7
   8.  Security Considerations . . . . . . . . . . . . . . . . . . . . 7
   9.  Acknowledgements  . . . . . . . . . . . . . . . . . . . . . . . 7
   10. Normative References  . . . . . . . . . . . . . . . . . . . . . 8

Sheth, et al.                Standards Track                    [Page 2]
RFC 6845        OSPF Hybrid Broadcast and P2MP Intf Type    January 2013

1.  Introduction

   OSPF [RFC2328] operation on broadcast interfaces takes advantage of
   the broadcast capabilities of the underlying medium for doing
   neighbor discovery and maintenance.  Further, it uses a Designated
   Router (DR) and Backup Designated Router (BDR) to keep the Link State
   Advertisement (LSA) databases of the routers on the network
   synchronized in an efficient manner.  However, it has the limitation
   that a router cannot advertise different costs to each of the
   neighboring routers on the network in its router-LSA.

   Consider a radio network that supports true broadcast, yet the
   metrics between different pairs of terminals could be different for