The Cisco ONS is interoperable with our existing Cisco ONS UPSR architecture and it also gives us 16 rings of completely interoperable ONS. BLSR,Bi-directional Line Switched ring. There are two types of BLSR deployed in various networks. i. 2-fiber BLSR ii. 4-fiber BLSR. How is Bi-directional Line Switched Ring (SONET) abbreviated? BLSR stands for Bi-directional Line Switched Ring (SONET). BLSR is defined as Bi-directional.

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Plug fiber connected to an east port at one node into the west port on an adjacent node.


The input at node A travels clockwise on ring1 and egresses at node C. The signal egresses at node A completing the circuit, establishing communications between nodes A and B. Each site has free slots for future traffic needs. When the fiber between B and C is restored the selector at node C will not switch back because the there is not any path degradation to cause the selector to switch. The intermediate nodes continue to drop and insert traffic on the working channels as normal.

The Span Upgrade Wizard provides no way to back out of an upgrade. Ring 1 runs on Nodes 1, 2, 3, and 4. If the upgrade is conducted on spans residing in a BLSR, all spans in the ring must be upgraded. The capacity advantage here is 2 times that of a UPSR, or Posted by Shankar BLR at Hoping to read more post from you in the future. This flexibility in the reuse of bandwidth is one of the major advantages of a BLSR.

Subtending rings from an ONS reduces the number of nodes and cards required and reduces external shelf-to-shelf cabling. By doing this, the backup bandwidth would increase if multiple links were to be protected.


In the example, each remote switch requires eight DS-1s to return to the host switch. Cisco recommends using the Span Upgrade Wizard to perform span upgrades. Timeslot assignment of extra traffic on the protection channel will be supported. When the affected nodes return to the Idle, K-byte pass-through, or span switching state, extra traffic on spans whose protection channels are not used for protection purposes is restored. The p-cycle technique is based on the property of a ring to protect not only its own links, but also any possible links connecting two non-adjacent ring nodes called chordal links.

Multiple span switches can bls at the same time. This is rinb an interesting topic. Manual Span Upgrades are mainly provided as error recovery for the Span Upgrade Wizard, but they can be used to perform span upgrades.

If both directions of transmission rin the same set of nodes and links, the transmission is said to be bidirectional. This system is also known as four-fiber multiplex-section shared protection ring. In path protection, a backup path is used from the source to its destination to bypass the failure.

Figure 2 illustrates this fact. Wish you more success. When the protection channels are not required, they can be used to carry extra traffic, but at the time of protection switching, this extra traffic is dropped.


In two-fiber BLSRs, each fiber is divided into working and protect bandwidths. Protection architectures like Path protection and Link protection safeguard the above-mentioned networks from different kinds of failures. For instance, if all the LSPs are to be protected, then the net capacity should equal the bandwidth of the protected link.

The nodes to which the requests were addressed then perform ring switches. A single fiber cut can lead to heavy losses of traffic and protection-switching rinv have been used as the key source to ensure survivability in such networks. The Cisco Transport Controller CTC circuit routing routines calculate the “shortest path” for circuits based on many factors, including requirements set by the circuit provisioner, traffic patterns, and distance. With multiple nodes, a span upgrade is rong coordinated series of upgrades on all nodes in the ring or protection group in which traffic carried at a lower OC-N rate is transferred to a higher OC-N.


Notice that all that is needed for this circuit to be operational is the ring1 fiber unidirectional path.

In this system, bi-directional pairs of fibers are used to connect each span in the rinf. Traffic is delivered to the service provider’s major hubs. Slot 6 west and Slot 13 east carry the protect traffic.

Only ring switching is supported by this architecture. In a ring switch, traffic is routed to the protect fibers throughout the full ring. This is reminiscent of the UPSR case. So if nodes A and C had 3 DS-s provisioned between them then the entire ring bandwidth would be used and no traffic could be added at nodes B and D.

Because node C is adjacent to the fiber cut all of its selectors will make a path switch. Newer Post Older Post Home. Because each traffic path is transported around the entire ring, UPSRs are best suited for networks where traffic concentrates at one or two locations and is not widely distributed. Working traffic flows in one direction and protection traffic flows in the opposite direction. In this example a circuit is to be set up between nodes A and C. Really looking forward to read more.

In the case of a link or network failure, the simplest mechanism for network survivability is automatic protection switching APS.