Operational Management of Loop-Free Alternates
RFC 7916

Document Type RFC - Proposed Standard (July 2016; No errata)
Last updated 2016-07-11
Replaces draft-litkowski-rtgwg-lfa-manageability
Stream IETF
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Stream WG state Submitted to IESG for Publication Jul 2015
Document shepherd Jeff Tantsura
Shepherd write-up Show (last changed 2015-05-04)
IESG IESG state RFC 7916 (Proposed Standard)
Consensus Boilerplate Yes
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Responsible AD Alia Atlas
Send notices to (None)
IANA IANA review state Version Changed - Review Needed
IANA action state No IC
Internet Engineering Task Force (IETF)                 S. Litkowski, Ed.
Request for Comments: 7916                                   B. Decraene
Category: Standards Track                                         Orange
ISSN: 2070-1721                                              C. Filsfils
                                                                 K. Raza
                                                           Cisco Systems
                                                            M. Horneffer
                                                        Deutsche Telekom
                                                               P. Sarkar
                                                  Individual Contributor
                                                               July 2016

             Operational Management of Loop-Free Alternates

Abstract

   Loop-Free Alternates (LFAs), as defined in RFC 5286, constitute an IP
   Fast Reroute (IP FRR) mechanism enabling traffic protection for IP
   traffic (and, by extension, MPLS LDP traffic).  Following early
   deployment experiences, this document provides operational feedback
   on LFAs, highlights some limitations, and proposes a set of
   refinements to address those limitations.  It also proposes required
   management specifications.

   This proposal is also applicable to remote-LFA solutions.

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/rfc7916.

Litkowski, et al.            Standards Track                    [Page 1]
RFC 7916                    LFA Manageability                  July 2016

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.

Litkowski, et al.            Standards Track                    [Page 2]
RFC 7916                    LFA Manageability                  July 2016

Table of Contents

   1. Introduction ....................................................4
      1.1. Requirements Language ......................................4
   2. Definitions .....................................................4
   3. Operational Issues with Default LFA Tiebreakers .................5
      3.1. Case 1: PE Router Protecting against Failures
           within Core Network ........................................5
      3.2. Case 2: PE Router Chosen to Protect against Core
           Failures while P Router LFA Exists .........................7
      3.3. Case 3: Suboptimal P Router Alternate Choice ...............8
      3.4. Case 4: No-Transit LFA Computing Node ......................9
   4. Need for Coverage Monitoring ....................................9
   5. Need for LFA Activation Granularity ............................10
   6. Configuration Requirements .....................................11
      6.1. LFA Enabling/Disabling Scope ..............................11
      6.2. Policy-Based LFA Selection ................................12
           6.2.1. Connected versus Remote Alternates .................12
           6.2.2. Mandatory Criteria .................................13
           6.2.3. Additional Criteria ................................14
           6.2.4. Evaluation of Criteria .............................14
           6.2.5. Retrieving Alternate Path Attributes ...............18
           6.2.6. ECMP LFAs ..........................................23
   7. Operational Aspects ............................................24
      7.1. No-Transit Condition on LFA Computing Node ................24
      7.2. Manual Triggering of FRR ..................................25
      7.3. Required Local Information ................................26
      7.4. Coverage Monitoring .......................................26
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