LFA selection for Multi-Homed Prefixes
draft-ietf-rtgwg-multihomed-prefix-lfa-04
Routing Area Working Group P. Sarkar, Ed.
Internet-Draft Arrcus, Inc.
Updates: 5286 (if approved) S. Hegde
Intended status: Standards Track Juniper Networks, Inc.
Expires: June 4, 2018 U. Chunduri, Ed.
Huawei Technologies
J. Tantsura
Individual
H. Gredler
RtBrick, Inc.
December 1, 2017
LFA selection for Multi-Homed Prefixes
draft-ietf-rtgwg-multihomed-prefix-lfa-04
Abstract
This document shares experience gained from implementing algorithms
to determine Loop-Free Alternates for multi-homed prefixes. In
particular, this document provides explicit inequalities that can be
used to evaluate neighbors as a potential alternates for multi-homed
prefixes. It also provides detailed criteria for evaluating
potential alternates for external prefixes advertised by OSPF ASBRs.
This documents updates and expands some of the "Routing Aspects" as
specified in Section 6 of [RFC5286].
Requirements Language
The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT",
"SHOULD", "SHOULD NOT", "RECOMMENDED", "MAY", and "OPTIONAL" in this
document are to be interpreted as described in RFC2119 [RFC2119].
Status of This Memo
This Internet-Draft is submitted in full conformance with the
provisions of BCP 78 and BCP 79.
Internet-Drafts are working documents of the Internet Engineering
Task Force (IETF). Note that other groups may also distribute
working documents as Internet-Drafts. The list of current Internet-
Drafts is at https://datatracker.ietf.org/drafts/current/.
Internet-Drafts are draft documents valid for a maximum of six months
and may be updated, replaced, or obsoleted by other documents at any
time. It is inappropriate to use Internet-Drafts as reference
material or to cite them other than as "work in progress."
Sarkar, et al. Expires June 4, 2018 [Page 1]
Internet-Draft LFA selection for Multi-Homed Prefixes December 2017
This Internet-Draft will expire on June 4, 2018.
Copyright Notice
Copyright (c) 2017 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
(https://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
1.1. Acronyms . . . . . . . . . . . . . . . . . . . . . . . . 3
2. LFA inequalities for MHPs . . . . . . . . . . . . . . . . . . 4
3. LFA selection for the multi-homed prefixes . . . . . . . . . 4
3.1. Improved coverage with simplified approach to MHPs . . . 6
3.2. IS-IS ATT Bit considerations . . . . . . . . . . . . . . 8
4. LFA selection for the multi-homed external prefixes . . . . . 8
4.1. IS-IS . . . . . . . . . . . . . . . . . . . . . . . . . . 8
4.2. OSPF . . . . . . . . . . . . . . . . . . . . . . . . . . 8
4.2.1. Rules to select alternate ASBR . . . . . . . . . . . 9
4.2.2. Multiple ASBRs belonging different area . . . . . . . 10
4.2.3. Type 1 and Type 2 costs . . . . . . . . . . . . . . . 11
4.2.4. RFC1583compatibility is set to enabled . . . . . . . 11
4.2.5. Type 7 routes . . . . . . . . . . . . . . . . . . . . 11
4.2.6. Inequalities to be applied for alternate ASBR
selection . . . . . . . . . . . . . . . . . . . . . . 11
4.2.6.1. Forwarding address set to non-zero value . . . . 11
4.2.6.2. ASBRs advertising type1 and type2 cost . . . . . 12
5. LFA Extended Procedures . . . . . . . . . . . . . . . . . . . 13
5.1. Links with IGP MAX_METRIC . . . . . . . . . . . . . . . . 13
5.2. Multi Topology Considerations . . . . . . . . . . . . . . 14
6. Acknowledgements . . . . . . . . . . . . . . . . . . . . . . 15
7. Contributing Authors . . . . . . . . . . . . . . . . . . . . 15
Show full document text