| 摘要 |
This invention concerns a protection scheme for a metro optical network h aving a ring topology. The scheme involves programming ingress nodes (102A) and egress nodes (102B to 102F) with a primary LSP (107) and a back-up LSP ( 108) to provide one-to-one protection over the network. During normal use, m ulticast communications are sent on the primary LSP (107), however, on the o ccurrence of a fault, the nodes (102A to 102F) continue to send the multicas t communication in the primary LSP (107) but also send a duplicate of the co mmunication in the back-up LSP ( 108). In this way, the primary and back-up LSPs (107 and 108) can be configured in advance of the fault occurring, whil e at the same time avoiding failure of the network to transmit the multicast communication on occurrence of a fault. Configuring the primary and back-up LSPs (107 and 108) in advance of a fault occurring is advantageous as it av oids the need for signalling to establish a working LSP on occurrence of a f ault (as is the case for protection schemes that determine a back-up LSP on demand).
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