OSPF Two-Part Metric
RFC 8042

Document Type RFC - Proposed Standard (December 2016; No errata)
Updates RFC 2328
Last updated 2016-12-28
Replaces draft-zzhang-ospf-two-part-metric
Stream IETF
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Reviews
Stream WG state Submitted to IESG for Publication (wg milestone: Jun 2016 - Standardize OSPF 2-P... )
Document shepherd Yingzhen Qu
Shepherd write-up Show (last changed 2016-04-29)
IESG IESG state RFC 8042 (Proposed Standard)
Consensus Boilerplate Yes
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Responsible AD Alia Atlas
Send notices to "Yingzhen Qu" <yiqu@cisco.com>
IANA IANA review state Version Changed - Review Needed
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Internet Engineering Task Force (IETF)                          Z. Zhang
Request for Comments: 8042                                       L. Wang
Updates: 2328                                     Juniper Networks, Inc.
Category: Standards Track                                      A. Lindem
ISSN: 2070-1721                                            Cisco Systems
                                                           December 2016

                          OSPF Two-Part Metric

Abstract

   This document specifies an optional OSPF protocol extension to
   represent router metrics in a multi-access network in two parts: the
   metric from the router to the network and the metric from the network
   to the router.  For such networks, the router-to-router metric for
   OSPF route computation is the sum of the two parts.  This document
   updates RFC 2328.

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 7841.

   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/rfc8042.

Copyright Notice

   Copyright (c) 2016 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.

Zhang, et al.                Standards Track                    [Page 1]
RFC 8042                  OSPF Two-Part Metric             December 2016

Table of Contents

   1.  Introduction  . . . . . . . . . . . . . . . . . . . . . . . .   2
     1.1.  Requirements Language . . . . . . . . . . . . . . . . . .   3
   2.  Proposed Enhancement  . . . . . . . . . . . . . . . . . . . .   3
   3.  Specifications  . . . . . . . . . . . . . . . . . . . . . . .   4
     3.1.  Router Interface Parameters . . . . . . . . . . . . . . .   4
     3.2.  Advertising Network-to-Router Metric in OSPFv2  . . . . .   4
     3.3.  Advertising Network-to-Router Traffic Engineering (TE)
           Metric  . . . . . . . . . . . . . . . . . . . . . . . . .   5
     3.4.  Advertising Network-to-Router Metric in OSPFv3  . . . . .   5
     3.5.  OSPF Stub Router Behavior . . . . . . . . . . . . . . . .   5
     3.6.  SPF Calculation . . . . . . . . . . . . . . . . . . . . .   5
     3.7.  Backward Compatibility  . . . . . . . . . . . . . . . . .   6
   4.  IANA Considerations . . . . . . . . . . . . . . . . . . . . .   6
   5.  Security Considerations . . . . . . . . . . . . . . . . . . .   6
   6.  References  . . . . . . . . . . . . . . . . . . . . . . . . .   7
     6.1.  Normative References  . . . . . . . . . . . . . . . . . .   7
     6.2.  Informative References  . . . . . . . . . . . . . . . . .   7
   Acknowledgements  . . . . . . . . . . . . . . . . . . . . . . . .   8
   Contributors  . . . . . . . . . . . . . . . . . . . . . . . . . .   8
   Authors' Addresses  . . . . . . . . . . . . . . . . . . . . . . .   9

1.  Introduction

   With Open Shortest Path First (OSPF) [RFC2328] [RFC5340]), a Network-
   LSA (Link State Advertisement) is advertised to list all routers on a
   broadcast network.  Additionally, each router on the broadcast
   network includes a link in its Router-LSA to describe its connection
   to the network.  The link in the Router-LSA includes a metric but the
   listed routers in the Network-LSA do not include a metric.  This is
   based on the assumption that from a particular router, all others on
   the same network can be reached with the same metric.

   With some broadcast networks, different routers can be reached with
   different metrics.  [RFC6845] extends the OSPF protocol with a hybrid
   interface type for that kind of broadcast network, where no Network-
   LSA is advertised and Router-LSAs simply include point-to-point links
   to all routers on the same network with individual metrics.
   Broadcast capability is still used to optimize database
   synchronization and adjacency maintenance.

   This works well for broadcast networks where the metric between
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