draft-ietf-rtgwg-multihomed-prefix-lfa-00.txt   draft-ietf-rtgwg-multihomed-prefix-lfa-01.txt 
Routing Area Working Group P. Sarkar, Ed. Routing Area Working Group P. Sarkar, Ed.
Internet-Draft Individual Internet-Draft Individual
Intended status: Informational S. Hegde Intended status: Informational S. Hegde
Expires: February 5, 2017 C. Bowers Expires: July 20, 2017 C. Bowers
Juniper Networks, Inc. Juniper Networks, Inc.
U. Chunduri, Ed. U. Chunduri, Ed.
Ericsson Inc. Huawei Technologies
J. Tantsura J. Tantsura
Individual Individual
B. Decraene B. Decraene
Orange Orange
H. Gredler H. Gredler
Unaffiliated RtBrick, Inc.
August 4, 2016 January 16, 2017
LFA selection for Multi-Homed Prefixes LFA selection for Multi-Homed Prefixes
draft-ietf-rtgwg-multihomed-prefix-lfa-00 draft-ietf-rtgwg-multihomed-prefix-lfa-01
Abstract Abstract
This document shares experience gained from implementing algorithms This document shares experience gained from implementing algorithms
to determine Loop-Free Alternates for multi-homed prefixes. In to determine Loop-Free Alternates for multi-homed prefixes. In
particular, this document provides explicit inequalities that can be particular, this document provides explicit inequalities that can be
used to evaluate neighbors as a potential alternates for multi-homed used to evaluate neighbors as a potential alternates for multi-homed
prefixes. It also provides detailed criteria for evaluating prefixes. It also provides detailed criteria for evaluating
potential alternates for external prefixes advertised by OSPF ASBRs. potential alternates for external prefixes advertised by OSPF ASBRs.
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Copyright Notice Copyright Notice
Copyright (c) 2016 IETF Trust and the persons identified as the Copyright (c) 2017 IETF Trust and the persons identified as the
document authors. All rights reserved. document authors. All rights reserved.
This document is subject to BCP 78 and the IETF Trust's Legal This document is subject to BCP 78 and the IETF Trust's Legal
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the Trust Legal Provisions and are provided without warranty as the Trust Legal Provisions and are provided without warranty as
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4. LFA selection for the multi-homed external prefixes . . . . . 8 4. LFA selection for the multi-homed external prefixes . . . . . 8
4.1. IS-IS . . . . . . . . . . . . . . . . . . . . . . . . . . 8 4.1. IS-IS . . . . . . . . . . . . . . . . . . . . . . . . . . 8
4.2. OSPF . . . . . . . . . . . . . . . . . . . . . . . . . . 8 4.2. OSPF . . . . . . . . . . . . . . . . . . . . . . . . . . 8
4.2.1. Rules to select alternate ASBR . . . . . . . . . . . 8 4.2.1. Rules to select alternate ASBR . . . . . . . . . . . 8
4.2.2. Multiple ASBRs belonging different area . . . . . . . 9 4.2.2. Multiple ASBRs belonging different area . . . . . . . 9
4.2.3. Type 1 and Type 2 costs . . . . . . . . . . . . . . . 10 4.2.3. Type 1 and Type 2 costs . . . . . . . . . . . . . . . 10
4.2.4. RFC1583compatibility is set to enabled . . . . . . . 10 4.2.4. RFC1583compatibility is set to enabled . . . . . . . 10
4.2.5. Type 7 routes . . . . . . . . . . . . . . . . . . . . 10 4.2.5. Type 7 routes . . . . . . . . . . . . . . . . . . . . 10
4.2.6. Inequalities to be applied for alternate ASBR 4.2.6. Inequalities to be applied for alternate ASBR
selection . . . . . . . . . . . . . . . . . . . . . . 10 selection . . . . . . . . . . . . . . . . . . . . . . 10
4.2.6.1. Forwarding address set to non zero value . . . . 10 4.2.6.1. Forwarding address set to non-zero value . . . . 10
4.2.6.2. ASBRs advertising type1 and type2 cost . . . . . 11 4.2.6.2. ASBRs advertising type1 and type2 cost . . . . . 11
5. LFA Extended Procedures . . . . . . . . . . . . . . . . . . . 12 5. LFA Extended Procedures . . . . . . . . . . . . . . . . . . . 12
5.1. Links with IGP MAX_METRIC . . . . . . . . . . . . . . . . 12 5.1. Links with IGP MAX_METRIC . . . . . . . . . . . . . . . . 12
5.2. Multi Topology Considerations . . . . . . . . . . . . . . 13 5.2. Multi Topology Considerations . . . . . . . . . . . . . . 13
6. Acknowledgements . . . . . . . . . . . . . . . . . . . . . . 14 6. Acknowledgements . . . . . . . . . . . . . . . . . . . . . . 14
7. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 14 7. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 14
8. Security Considerations . . . . . . . . . . . . . . . . . . . 14 8. Security Considerations . . . . . . . . . . . . . . . . . . . 14
9. References . . . . . . . . . . . . . . . . . . . . . . . . . 14 9. References . . . . . . . . . . . . . . . . . . . . . . . . . 14
9.1. Normative References . . . . . . . . . . . . . . . . . . 14 9.1. Normative References . . . . . . . . . . . . . . . . . . 14
9.2. Informative References . . . . . . . . . . . . . . . . . 15 9.2. Informative References . . . . . . . . . . . . . . . . . 15
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for P with the N as the alternate neighbor. for P with the N as the alternate neighbor.
1.a. If LFA inequality condition is met, 1.a. If LFA inequality condition is met,
select N as a LFA for prefix P. select N as a LFA for prefix P.
1.b. Else, N is not a LFA for prefix P. 1.b. Else, N is not a LFA for prefix P.
Node-Protection : Node-Protection :
================= =================
1. If alternate neighbor N is also prefix-originator of P, 1. If alternate neighbor N is also prefix-originator of P,
1.a. Select N as a LFA for prefix P (irrespective of 1.a. Select N as a LFA for prefix P (irrespective of
the metric advertised by N for the prefix P). the metric advertised by N for the prefix P).
2. Else, evaluate the apporpriate node-protecting LFA inequality 2. Else, evaluate the appropriate node-protecting LFA inequality
for P with the N as the alternate neighbor. for P with the N as the alternate neighbor.
2.a. If LFA inequality condition is met, 2.a. If LFA inequality condition is met,
select N as a LFA for prefix P. select N as a LFA for prefix P.
2.b. Else, N is not a LFA for prefix P. 2.b. Else, N is not a LFA for prefix P.
Figure 2: Rules for selecting LFA for MHPs Figure 2: Rules for selecting LFA for MHPs
In case an alternate neighbor N is also one of the prefix-originators In case an alternate neighbor N is also one of the prefix-originators
of prefix P, N MAY be selected as a valid LFA for P. of prefix P, N MAY be selected as a valid LFA for P.
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4.2.4. RFC1583compatibility is set to enabled 4.2.4. RFC1583compatibility is set to enabled
When RFC1583Compatibility is set to enabled, multiple ASBRs belonging When RFC1583Compatibility is set to enabled, multiple ASBRs belonging
to different area advertising same prefix are chosen based on cost to different area advertising same prefix are chosen based on cost
and hence are valid alternate ASBRs for the LFA evaluation. and hence are valid alternate ASBRs for the LFA evaluation.
4.2.5. Type 7 routes 4.2.5. Type 7 routes
Type 5 routes always get preference over Type 7 and the alternate Type 5 routes always get preference over Type 7 and the alternate
ASBRs chosen for LFA calculation should belong to same type.Among ASBRs chosen for LFA calculation should belong to same type. Among
Type 7 routes, routes with p-bit and forwarding address set have Type 7 routes, routes with p-bit and forwarding address set have
higher preference than routes without these attributes. Alternate higher preference than routes without these attributes. Alternate
ASBRs selected for LFA comparison should have same p-bit and ASBRs selected for LFA comparison should have same p-bit and
forwarding address attributes. forwarding address attributes.
4.2.6. Inequalities to be applied for alternate ASBR selection 4.2.6. Inequalities to be applied for alternate ASBR selection
The alternate ASBRs selected using above mechanism described in The alternate ASBRs selected using above mechanism described in
3.2.1, are evaluated for Loop free criteria using below inequalities. 3.2.1, are evaluated for Loop free criteria using below inequalities.
4.2.6.1. Forwarding address set to non zero value 4.2.6.1. Forwarding address set to non-zero value
Link-Protection: Link-Protection:
F_opt(N,PO_i)+ cost(PO_i,P) < D_opt(N,S) + F_opt(N,PO_i)+ cost(PO_i,P) < D_opt(N,S) +
F_opt(S,PO_best) + cost(PO_best,P) F_opt(S,PO_best) + cost(PO_best,P)
Link-Protection + Downstream-paths-only: Link-Protection + Downstream-paths-only:
F_opt(N,PO_i)+ cost(PO_i,P) < F_opt(S,PO_best) + cost(PO_best,P) F_opt(N,PO_i)+ cost(PO_i,P) < F_opt(S,PO_best) + cost(PO_best,P)
Node-Protection: Node-Protection:
F_opt(N,PO_i)+ cost(PO_i,P) < D_opt(N,E) + F_opt(N,PO_i)+ cost(PO_i,P) < D_opt(N,E) +
F_opt(E,PO_best) + cost(PO_best,P) F_opt(E,PO_best) + cost(PO_best,P)
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dual environments", RFC 1195, DOI 10.17487/RFC1195, dual environments", RFC 1195, DOI 10.17487/RFC1195,
December 1990, <http://www.rfc-editor.org/info/rfc1195>. December 1990, <http://www.rfc-editor.org/info/rfc1195>.
[RFC2119] Bradner, S., "Key words for use in RFCs to Indicate [RFC2119] Bradner, S., "Key words for use in RFCs to Indicate
Requirement Levels", BCP 14, RFC 2119, Requirement Levels", BCP 14, RFC 2119,
DOI 10.17487/RFC2119, March 1997, DOI 10.17487/RFC2119, March 1997,
<http://www.rfc-editor.org/info/rfc2119>. <http://www.rfc-editor.org/info/rfc2119>.
9.2. Informative References 9.2. Informative References
[I-D.ietf-rtgwg-lfa-manageability]
Litkowski, S., Decraene, B., Filsfils, C., Raza, K., and
M. Horneffer, "Operational management of Loop Free
Alternates", draft-ietf-rtgwg-lfa-manageability-11 (work
in progress), June 2015.
[RFC3137] Retana, A., Nguyen, L., White, R., Zinin, A., and D. [RFC3137] Retana, A., Nguyen, L., White, R., Zinin, A., and D.
McPherson, "OSPF Stub Router Advertisement", RFC 3137, McPherson, "OSPF Stub Router Advertisement", RFC 3137,
DOI 10.17487/RFC3137, June 2001, DOI 10.17487/RFC3137, June 2001,
<http://www.rfc-editor.org/info/rfc3137>. <http://www.rfc-editor.org/info/rfc3137>.
[RFC4915] Psenak, P., Mirtorabi, S., Roy, A., Nguyen, L., and P. [RFC4915] Psenak, P., Mirtorabi, S., Roy, A., Nguyen, L., and P.
Pillay-Esnault, "Multi-Topology (MT) Routing in OSPF", Pillay-Esnault, "Multi-Topology (MT) Routing in OSPF",
RFC 4915, DOI 10.17487/RFC4915, June 2007, RFC 4915, DOI 10.17487/RFC4915, June 2007,
<http://www.rfc-editor.org/info/rfc4915>. <http://www.rfc-editor.org/info/rfc4915>.
skipping to change at page 15, line 47 skipping to change at page 15, line 41
[RFC5308] Hopps, C., "Routing IPv6 with IS-IS", RFC 5308, [RFC5308] Hopps, C., "Routing IPv6 with IS-IS", RFC 5308,
DOI 10.17487/RFC5308, October 2008, DOI 10.17487/RFC5308, October 2008,
<http://www.rfc-editor.org/info/rfc5308>. <http://www.rfc-editor.org/info/rfc5308>.
[RFC5838] Lindem, A., Ed., Mirtorabi, S., Roy, A., Barnes, M., and [RFC5838] Lindem, A., Ed., Mirtorabi, S., Roy, A., Barnes, M., and
R. Aggarwal, "Support of Address Families in OSPFv3", R. Aggarwal, "Support of Address Families in OSPFv3",
RFC 5838, DOI 10.17487/RFC5838, April 2010, RFC 5838, DOI 10.17487/RFC5838, April 2010,
<http://www.rfc-editor.org/info/rfc5838>. <http://www.rfc-editor.org/info/rfc5838>.
[RFC7916] Litkowski, S., Ed., Decraene, B., Filsfils, C., Raza, K.,
Horneffer, M., and P. Sarkar, "Operational Management of
Loop-Free Alternates", RFC 7916, DOI 10.17487/RFC7916,
July 2016, <http://www.rfc-editor.org/info/rfc7916>.
Authors' Addresses Authors' Addresses
Pushpasis Sarkar (editor) Pushpasis Sarkar (editor)
Individual Individual
Email: pushpasis.ietf@gmail.com Email: pushpasis.ietf@gmail.com
Shraddha Hegde Shraddha Hegde
Juniper Networks, Inc. Juniper Networks, Inc.
Electra, Exora Business Park Electra, Exora Business Park
Bangalore, KA 560103 Bangalore, KA 560103
skipping to change at page 16, line 21 skipping to change at page 16, line 21
Chris Bowers Chris Bowers
Juniper Networks, Inc. Juniper Networks, Inc.
1194 N. Mathilda Ave. 1194 N. Mathilda Ave.
Sunnyvale, CA 94089 Sunnyvale, CA 94089
US US
Email: cbowers@juniper.net Email: cbowers@juniper.net
Uma Chunduri (editor) Uma Chunduri (editor)
Ericsson Inc. Huawei Technologies
300 Holger Way, 2330 Central Expressway
San Jose, California 95134 Santa Clara, CA 95050
USA USA
Phone: 408 750-5678 Email: uma.chunduri@huawei.com
Email: uma.chunduri@ericsson.com
Jeff Tantsura Jeff Tantsura
Individual Individual
Email: jefftant.ietf@gmail.com Email: jefftant.ietf@gmail.com
Bruno Decraene Bruno Decraene
Orange Orange
Email: bruno.decraene@orange.com Email: bruno.decraene@orange.com
Hannes Gredler Hannes Gredler
Unaffiliated RtBrick, Inc.
Email: hannes@gredler.at Email: hannes@rtbrick.com
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