Technical data

TraverseEdge 2020 Applications and Engineering Guide, Chapter 3: System Applications
Page 3-26 Turin Networks Release 5.0.x
Turin Networks BLSR rings also offer Protection Channel Access (PCA) and Non-preemptable Unpro-
tected Traffic (NUT) provisioning features. PCA supports "extra" traffic in the BLSR protection channel,
which is not protected in the event of a fiber cut or ring switch. NUT supports bidirectionally provisioned
traffic in protection pairs that is not preempted by protection switching.
The TE-2020 supports both OC-192 and OC-48 BLSR-to-BLSR and BLSR-to-UPSR inter-working. In
addition, the TE-2020 can automatically create end-to-end connections over combined BLSR and UPSR
rings.
3.7 BLSR (Bi-directional Line Switched Rings)
The TE-2020 supports two-fiber BLSR operation. In two-fiber BLSRs, each fiber is divided into working
and protect bandwidths. For example, in an OC-192 BLSR, STSs 1 - 96 carry the working traffic (1-24 in
an OC-48 BLSR), and STSs 97 - 192 are reserved for protection (25-48 in an OC-48 BLSR). There is an
exception to this rule if the timeslot has been specifically configured to pass NUT traffic. One advantage of
BLSRs is that working traffic can be routed on the ring in either of the two different directions, the long
route around the ring or the short route. Although the short route will usually be preferred, occasionally
routing working traffic over the long route permits some load balancing.
Refer to Figure 3-25, circuits going from Node 1 to Node 2 typically will travel on Fiber 1, unless that fiber
is full, in which case connections will be made on Fiber 2 through Node 3 to Node 2. Traffic from Node 1
to Node 2 (or Node 1 to Node 3), may be routed on either fiber, depending on circuit provisioning require-
ments and traffic loads. A protected BLSR connection is implemented as a single cross-connect regardless
if it is adding, dropping or passing through traffic for the ring. In effect, Node 1 may choose to make a con-
nection over STS1-96 going out one set of optics (usually refered to as Westbound or Eastbound), or
STS1-96 out of the second set of optics. Both set of optics have reserved bandwidth for protection. Traffic
will be dropped from either set of receiving optics according to the connection made to the node. All other
traffic will pass through to continue its path around the ring.