A 2-fiber bidirectional line-switched ring (BLSR) is a self-healing ring configuration in which switching is bidirectional between each pair of adjacent nodes and is protected by redundant bandwidth on the bidirectional lines that interconnect the nodes in the ring. Because switching is bidirectional between nodes, traffic can be added at one node and dropped at the next without traveling around the entire ring. This leaves the spans between other nodes available for additional traffic. Therefore, with distributed traffic patterns, a BLSR can carry more traffic than the same facilities could carry if configured for a unidirectional line-switched ring.
Alcatel-Lucent 1665 DMX supports 15 simultaneous BLSR protection groups in a single shelf. The 15 protection groups can be provisioned on any available OC-48 and OC-192 port pairs within the high-speed and low-speed groups.
Alcatel-Lucent 1665 DMX 2-fiber BLSRs are self-healing in that transport is automatically restored after node or fiber failures. Each OC-192 line carries 96 STS-1 equivalent time slots of working capacity plus 96 STS-1 equivalent time slots of protection capacity. Each OC-48 line carries 24 STS-1 equivalent time slots of working capacity plus 24 STS-1 equivalent of protection capacity. In the event of a fiber or node failure, service is restored by switching traffic from the working capacity of the failed line to the protection capacity in the opposite direction around the ring. In the event of a node failure, traffic added and dropped from the failed node is not protected by line switching.
When a line failure triggers a protection switch, the nodes adjacent to the failure switch traffic on to protection capacity. Traffic heading toward the failure is looped back on to the protection capacity traveling away from the failure to reach its destination by traveling the opposite way around the ring. Service is reestablished on the protection capacity in 50 milliseconds after detection of the failure (for catastrophic failures in rings without existing protection switches or extra traffic).
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