draft-ietf-rtgwg-lfa-manageability-05.txt   draft-ietf-rtgwg-lfa-manageability-06.txt 
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Expires: July 10, 2015 C. Filsfils Expires: July 10, 2015 C. Filsfils
K. Raza K. Raza
Cisco Systems Cisco Systems
M. Horneffer M. Horneffer
Deutsche Telekom Deutsche Telekom
P. Sarkar P. Sarkar
Juniper Networks Juniper Networks
January 6, 2015 January 6, 2015
Operational management of Loop Free Alternates Operational management of Loop Free Alternates
draft-ietf-rtgwg-lfa-manageability-05 draft-ietf-rtgwg-lfa-manageability-06
Abstract Abstract
Loop Free Alternates (LFA), as defined in RFC 5286 is an IP Fast Loop Free Alternates (LFA), as defined in RFC 5286 is an IP Fast
ReRoute (IP FRR) mechanism enabling traffic protection for IP traffic ReRoute (IP FRR) mechanism enabling traffic protection for IP traffic
(and MPLS LDP traffic by extension). Following first deployment (and MPLS LDP traffic by extension). Following first deployment
experiences, this document provides operational feedback on LFA, experiences, this document provides operational feedback on LFA,
highlights some limitations, and proposes a set of refinements to highlights some limitations, and proposes a set of refinements to
address those limitations. It also proposes required management address those limitations. It also proposes required management
specifications. specifications.
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o attributes from the PLR to alternate path are retrieved using the o attributes from the PLR to alternate path are retrieved using the
PLR's primary SPF if P space is used or using the neighbor's SPF PLR's primary SPF if P space is used or using the neighbor's SPF
if extended P space is used, combined with the attributes of the if extended P space is used, combined with the attributes of the
link(s) to reach that neighbor. In both cases, no additional SPF link(s) to reach that neighbor. In both cases, no additional SPF
is required. is required.
o attributes from alternate to destination path are retrieved from o attributes from alternate to destination path are retrieved from
SPF rooted at the remote alternate. An additional forward SPF is SPF rooted at the remote alternate. An additional forward SPF is
required for each remote alternate as indicated in required for each remote alternate as indicated in
[I-D.psarkar-rtgwg-rlfa-node-protection] section 3.2.. [I-D.ietf-rtgwg-rlfa-node-protection] section 3.2..
The number of remote alternates may be very high, simulations shown The number of remote alternates may be very high, simulations shown
that hundred's of PQs may exist for a single interface being that hundred's of PQs may exist for a single interface being
protected. Running a forward SPF for every PQ-node in the network is protected. Running a forward SPF for every PQ-node in the network is
not scalable. not scalable.
To handle this situation, it is needed to limit the number of remote To handle this situation, it is needed to limit the number of remote
alternates to be evaluated to a finite number before collecting alternates to be evaluated to a finite number before collecting
alternate path attributes and running the policy evaluation. [I- alternate path attributes and running the policy evaluation. [I-
D.psarkar-rtgwg-rlfa-node-protection] Section 2.3.3 provides a way to D.ietf-rtgwg-rlfa-node-protection] Section 2.3.3 provides a way to
reduce the number of PQ to be evaluated. reduce the number of PQ to be evaluated.
Link Remote Remote Link Remote Remote
alternate alternate alternate alternate alternate alternate
------------- ------------------ ------------- ------------- ------------------ -------------
Alternates | LFA | | rLFA (PQs) | | Static | Alternates | LFA | | rLFA (PQs) | | Static |
sources | | | | | tunnels | sources | | | | | tunnels |
------------- ------------------ ------------- ------------- ------------------ -------------
| | | | | |
| | | | | |
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[RFC4205] Kompella, K. and Y. Rekhter, "Intermediate System to [RFC4205] Kompella, K. and Y. Rekhter, "Intermediate System to
Intermediate System (IS-IS) Extensions in Support of Intermediate System (IS-IS) Extensions in Support of
Generalized Multi-Protocol Label Switching (GMPLS)", RFC Generalized Multi-Protocol Label Switching (GMPLS)", RFC
4205, October 2005. 4205, October 2005.
[RFC5286] Atlas, A. and A. Zinin, "Basic Specification for IP Fast [RFC5286] Atlas, A. and A. Zinin, "Basic Specification for IP Fast
Reroute: Loop-Free Alternates", RFC 5286, September 2008. Reroute: Loop-Free Alternates", RFC 5286, September 2008.
11.2. Informative References 11.2. Informative References
[I-D.ietf-isis-node-admin-tag]
psarkar@juniper.net, p., Gredler, H., Hegde, S.,
Litkowski, S., Decraene, B., Li, Z., Aries, E., Rodriguez,
R., and H. Raghuveer, "Advertising Per-node Admin Tags in
IS-IS", draft-ietf-isis-node-admin-tag-00 (work in
progress), December 2014.
[I-D.ietf-rtgwg-remote-lfa] [I-D.ietf-rtgwg-remote-lfa]
Bryant, S., Filsfils, C., Previdi, S., Shand, M., and N. Bryant, S., Filsfils, C., Previdi, S., Shand, M., and N.
So, "Remote LFA FRR", draft-ietf-rtgwg-remote-lfa-09 (work So, "Remote LFA FRR", draft-ietf-rtgwg-remote-lfa-09 (work
in progress), December 2014. in progress), December 2014.
[I-D.litkowski-rtgwg-lfa-rsvpte-cooperation] [I-D.ietf-rtgwg-rlfa-node-protection]
Litkowski, S., Decraene, B., Filsfils, C., and K. Raza,
"Interactions between LFA and RSVP-TE", draft-litkowski-
rtgwg-lfa-rsvpte-cooperation-02 (work in progress), August
2013.
[I-D.psarkar-isis-node-admin-tag]
psarkar@juniper.net, p., Gredler, H., Hegde, S.,
Litkowski, S., Decraene, B., Li, Z., and H. Raghuveer,
"Advertising Per-node Admin Tags in IS-IS", draft-psarkar-
isis-node-admin-tag-03 (work in progress), October 2014.
[I-D.psarkar-rtgwg-rlfa-node-protection]
psarkar@juniper.net, p., Gredler, H., Hegde, S., Bowers, psarkar@juniper.net, p., Gredler, H., Hegde, S., Bowers,
C., Litkowski, S., and H. Raghuveer, "Remote-LFA Node C., Litkowski, S., and H. Raghuveer, "Remote-LFA Node
Protection and Manageability", draft-psarkar-rtgwg-rlfa- Protection and Manageability", draft-ietf-rtgwg-rlfa-node-
node-protection-05 (work in progress), June 2014. protection-01 (work in progress), December 2014.
[RFC3630] Katz, D., Kompella, K., and D. Yeung, "Traffic Engineering [RFC3630] Katz, D., Kompella, K., and D. Yeung, "Traffic Engineering
(TE) Extensions to OSPF Version 2", RFC 3630, September (TE) Extensions to OSPF Version 2", RFC 3630, September
2003. 2003.
[RFC3906] Shen, N. and H. Smit, "Calculating Interior Gateway [RFC3906] Shen, N. and H. Smit, "Calculating Interior Gateway
Protocol (IGP) Routes Over Traffic Engineering Tunnels", Protocol (IGP) Routes Over Traffic Engineering Tunnels",
RFC 3906, October 2004. RFC 3906, October 2004.
[RFC4090] Pan, P., Swallow, G., and A. Atlas, "Fast Reroute [RFC4090] Pan, P., Swallow, G., and A. Atlas, "Fast Reroute
 End of changes. 6 change blocks. 
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