draft-ietf-rtgwg-mrt-frr-algorithm-04.txt   draft-ietf-rtgwg-mrt-frr-algorithm-05.txt 
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Intended status: Standards Track Ericsson Intended status: Standards Track Ericsson
Expires: January 3, 2016 A. Atlas, Ed. Expires: January 3, 2016 A. Atlas, Ed.
C. Bowers C. Bowers
Juniper Networks Juniper Networks
A. Gopalan A. Gopalan
University of Arizona University of Arizona
July 2, 2015 July 2, 2015
Algorithms for computing Maximally Redundant Trees for IP/LDP Fast- Algorithms for computing Maximally Redundant Trees for IP/LDP Fast-
Reroute Reroute
draft-ietf-rtgwg-mrt-frr-algorithm-04 draft-ietf-rtgwg-mrt-frr-algorithm-05
Abstract Abstract
A complete solution for IP and LDP Fast-Reroute using Maximally A complete solution for IP and LDP Fast-Reroute using Maximally
Redundant Trees is presented in [I-D.ietf-rtgwg-mrt-frr- Redundant Trees is presented in [I-D.ietf-rtgwg-mrt-frr-
architecture]. This document defines the associated MRT Lowpoint architecture]. This document defines the associated MRT Lowpoint
algorithm that is used in the default MRT profile to compute both the algorithm that is used in the default MRT profile to compute both the
necessary Maximally Redundant Trees with their associated next-hops necessary Maximally Redundant Trees with their associated next-hops
and the alternates to select for MRT-FRR. and the alternates to select for MRT-FRR.
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7. Python Implementation of MRT Lowpoint Algorithm . . . . . . . 45 7. Python Implementation of MRT Lowpoint Algorithm . . . . . . . 45
8. Algorithm Alternatives and Evaluation . . . . . . . . . . . . 66 8. Algorithm Alternatives and Evaluation . . . . . . . . . . . . 66
8.1. Algorithm Evaluation . . . . . . . . . . . . . . . . . . 66 8.1. Algorithm Evaluation . . . . . . . . . . . . . . . . . . 66
9. Implementation Status . . . . . . . . . . . . . . . . . . . . 76 9. Implementation Status . . . . . . . . . . . . . . . . . . . . 76
10. Algorithm Work to Be Done . . . . . . . . . . . . . . . . . . 76 10. Algorithm Work to Be Done . . . . . . . . . . . . . . . . . . 76
11. Acknowledgements . . . . . . . . . . . . . . . . . . . . . . 76 11. Acknowledgements . . . . . . . . . . . . . . . . . . . . . . 76
12. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 76 12. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 76
13. Security Considerations . . . . . . . . . . . . . . . . . . . 76 13. Security Considerations . . . . . . . . . . . . . . . . . . . 76
14. References . . . . . . . . . . . . . . . . . . . . . . . . . 76 14. References . . . . . . . . . . . . . . . . . . . . . . . . . 76
14.1. Normative References . . . . . . . . . . . . . . . . . . 76 14.1. Normative References . . . . . . . . . . . . . . . . . . 76
14.2. Informative References . . . . . . . . . . . . . . . . . 76 14.2. Informative References . . . . . . . . . . . . . . . . . 77
Appendix A. Option 2: Computing GADAG using SPFs . . . . . . . . 78 Appendix A. Option 2: Computing GADAG using SPFs . . . . . . . . 79
Appendix B. Option 3: Computing GADAG using a hybrid method . . 83 Appendix B. Option 3: Computing GADAG using a hybrid method . . 84
Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . 85 Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . 86
1. Introduction 1. Introduction
MRT Fast-Reroute requires that packets can be forwarded not only on MRT Fast-Reroute requires that packets can be forwarded not only on
the shortest-path tree, but also on two Maximally Redundant Trees the shortest-path tree, but also on two Maximally Redundant Trees
(MRTs), referred to as the MRT-Blue and the MRT-Red. A router which (MRTs), referred to as the MRT-Blue and the MRT-Red. A router which
experiences a local failure must also have pre-determined which experiences a local failure must also have pre-determined which
alternate to use. This document defines how to compute these three alternate to use. This document defines how to compute these three
things for use in MRT-FRR and describes the algorithm design things for use in MRT-FRR and describes the algorithm design
decisions and rationale. The algorithm is based on those presented decisions and rationale. The algorithm is based on those presented
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Broadcast Interfaces: The algorithm assumes that broadcast Broadcast Interfaces: The algorithm assumes that broadcast
interfaces are already represented as pseudo-nodes in the network interfaces are already represented as pseudo-nodes in the network
graph. Given maximal redundancy, one of the MRT will try to avoid graph. Given maximal redundancy, one of the MRT will try to avoid
both the pseudo-node and the next hop. The exact rules need to be both the pseudo-node and the next hop. The exact rules need to be
fully specified. fully specified.
11. Acknowledgements 11. Acknowledgements
The authors would like to thank Shraddha Hegde for her suggestions The authors would like to thank Shraddha Hegde for her suggestions
and review. and review. We would also like to thank Anil Kumar SN for his
assistance in clarifying the algorithm description and pseudocode.
12. IANA Considerations 12. IANA Considerations
This document includes no request to IANA. This document includes no request to IANA.
13. Security Considerations 13. Security Considerations
This architecture is not currently believed to introduce new security This architecture is not currently believed to introduce new security
concerns. concerns.
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