Аннотация
The IETF currently discusses fast reroute mechanisms for IP networks
(IP FRR) to accelerate the recovery in case of network element failures
and to avoid microloops during network-wide routing re-convergence.
Several mechanisms are proposed. Loop-free alternates (LFAs) are
simple, but they cannot cover all single link and node failures.
Not-via addresses are more complex and cover all single failures, but
they potentially lead to longer backup paths and require tunnelling
which may reduce the forwarding speed of the routers. In addition, they
increase the size of the forwarding tables. This work studies the
combination of those simple and complex mechanisms to achieve full
single failure coverage with least overhead. First, we establish a
taxonomy for LFAs according to their ability and propose combination
options with not-vias for different resilience requirements. Then, we
quantify the effect of combining both mechanisms regarding their
applicability for the resilience requirements, routing table size, link
utilization, backup path length, and amount of traffic requiring
decapsulation per router. The results show that there are no strong
advantages of the combined application of both mechanisms over not-via
as the only IP FRR concept if 100% coverage for single link and node
failures is required.
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