Loop-free convergence using oFIB

The information below is for an old version of the document
Document Type Expired Internet-Draft (rtgwg WG)
Authors Mike Shand  , Stewart Bryant  , Stefano Previdi  , Clarence Filsfils 
Last updated 2011-04-20 (latest revision 2010-10-22)
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This Internet-Draft is no longer active. A copy of the expired Internet-Draft can be found at


This document describes a mechanism for use in conjunction with link state routing protocols which prevents the transient loops which would otherwise occur during topology changes. It does this by correctly sequencing the FIB updates on the routers. This mechanism can be used in the case of non-urgent link or node shutdowns and restarts or link metric changes. It can also be used in conjunction with a fast re-route mechanism which converts a sudden link or node failure into a non-urgent topology change. This is possible where a complete repair path is provided for all affected destinations. After a non-urgent topology change, each router computes a rank that defines the time at which it can safely update its FIB. A method for accelerating this loop-free convergence process by the use of completion messages is also described. The technology described in this document has been subject to extensive simulation using real network topologies and costs, and pathological convergence behaviour. A variant of the technology described here has been experimentally deployed in a production network.


Mike Shand (mshand@cisco.com)
Stewart Bryant (stbryant@cisco.com)
Stefano Previdi (sprevidi@cisco.com)
Clarence Filsfils (cfilsfil@cisco.com)

(Note: The e-mail addresses provided for the authors of this Internet-Draft may no longer be valid.)