The use of real-time multimedia or
mission-critical applications over IP networks puts strong pressure on service
providers to operate disruption-free networks. However, after any topological
change, link-state Interior Gateway Protocols (IGPs), such as IS-IS or OSPF,
enter a convergence phase during which transient forwarding loops may occur.
Such loops increase the network latency and cause packet losses. In this paper,
we propose and evaluate an efficient algorithm aimed at avoiding such traffic
disruptions without modifying these IGPs. In case of an intentional modification
of the weight of a link (e.g., to shut it down for maintenance operations or to
perform traffic engineering), our algorithm iteratively changes this weight,
splitting the modification into a sequence of loop-free transitions. The number
of weight increments that need to be applied on the link to reach its target
state is minimized in order to remain usable in existing networks. Analysis
performed on inferred and real Internet service provider (ISP) topologies shows
that few weight increments are required to handle most link shutdown events
(less than two intermediate metrics for more than 85% of the links). The
evaluation of our implementation also reveals that these minimal sequences can
be computed in a reasonable time.
No comments:
Post a Comment