| 摘要 |
<p>This invention concerns a protection scheme for a metro optical network having 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, multicast communications are sent on the primary LSP (107), however, on the occurrence of a fault, the nodes (102A to 102F) continue to send the multicast communication in the primary LSP (107) but also send a duplicate of the communication 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, while 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 avoids the need for signalling to establish a working LSP on occurrence of a fault (as is the case for protection schemes that determine a back-up LSP on demand).</p> |
