Routing and fast protection in networks of long-reach PONs

This paper reports on proposed solutions to the recovery from faults in a generic class of networks, where customer access is achieved via long-reach passive optical networks (LR-PONs), with the majority of customers enjoying protection in the backhaul regime to two separate metro nodes. Initial modelling studies suggest that in the event of a cable failure or single equipment element failure, redirected data will almost always leave the transmitting node in under 50 ms. For more catastrophic failures (such as router failure or loss of a metro node), recovery might take between 100—200 ms. Reachability information for each LR-PON is discovered over each area of the network, and used to inform the redirection of traffic via tunnels. The scheme uses IP signalling to enable traffic re-routing, although the underlying services may be of any type (e.g. private line) — making the scheme separate from the service, customer or provider.