Technical data

TraverseEdge 2020 Applications and Engineering Guide, Chapter 3: System Applications
Page 3-28 Turin Networks Release 5.0.x
Figure 3-26 Three Node, 2-Fiber BLSR Traffic Pattern Following Line Break
All circuits originating on Node 1 carried to Node 2 on Fiber 1 are switched to the protect bandwidth of
Fiber 2. For example, a circuit carried on STS-1 on Fiber 1 is switched to STS-97 on Fiber 2. A circuit car-
ried on STS-2 on Fiber 1 is switched to STS-98 on Fiber 2. Fiber 2 carries the circuit to Node 2 (the origi-
nal routing destination). Node 2 switches the circuit back to STS-1 on Fiber 1 where it is routed to Node 3
on STS-1.
Circuits originating on Node 2 that were normally carried to Node 1 on Fiber 2 are switched to the protect
bandwidth of Fiber 1 at Node 2. For example, a circuit carried on STS-4 on Fiber 2 is switched to STS-100
on Fiber 1. Fiber 1 carries the circuit to Node 1 where the circuit is switched back to STS-4 on Fiber 2 and
then dropped to its destination.
PCA (Preemptable- Unprotected) BLSR Connection
Protected Channel Access (or PCA or Extra traffic) is the term used to describe connections made in the
upper numbered time slots of a BLSR ring. These connections will pass traffic as long as there are no fail-
ures on the ring. However, when there is a protection event like a fiber failure, PCA traffic may be dropped
while the protected traffic uses the uppre numbered time slots for protection. when the protection event has
ended the PCA traffic will start passing again as the protected traffic returns to the original lower num-
bered time slots.
NUT (Non-Preemptable Unprotected) BLSR Connection