What is the Importance of "Back-up network switching" in Telecommunication?

Back-up network switching: Modern society is virtually completely dependent on communications technology. Trying to imagine a modern office without any connection to telephone or data networks is like trying to work out how a laundry can operate without water. Network failures, whether due to human error or faulty technology, can be very expensive for users and network providers alike. During the network failure it is very important to how it can be alive again as soon as possible. Back-up network switching is a way to recover the network alive again.As a result, the subject of so-called fall-back mechanisms or back-up network switching is currently one of the most talked about in the SDH world. A wide range of standardized mechanisms is incorporated into synchronous networks in order to compensate for failures in network elements.

Back-up network switching

Back-up network switching

Automatic protection switching (APS):Two basic types of protection architecture are distinguished in APS. One is the linear protection mechanism used for point-to-point connections.The other basic form is the so-called ring protection mechanism which can take on many different forms. Both mechanisms use spare circuits or components to provide the back-up path. Switching is controlled by the overhead bytes K1 and K2.

Linear protection: The simplest form of back-up is the so-called 1 + 1 APS. Here, each working line is protected by one protection line. If a defect occurs, the protection agent in the network elements at both ends switch the circuit over to the protection line. The switch over is triggered by a defect such as LOS. Switching at the far end is initiated by the return of an acknowledgment in the backward channel.

1+1 architecture includes 100% redundancy, as there is a spare line for each working line. Economic considerations have led to the preferential use of 1:N architecture, particularly for long-distance paths. In this case, several working lines are protected by a single back-up line. If switching is necessary, the two ends of the affected path are switched over to the back-up line.

The reserve circuits can be used for lower-priority traffic, which is simply interrupted if the circuit is needed to replace a failed working line.

Back-up network switching

Linear Protection Ring

Ring protection: The greater the communications bandwidth carried by optical fibers, the greater the cost advantages of ring structures as compared with linear structures. A ring is the simplest and most cost-effective way of linking a number of network elements. Various protection mechanisms are available for this type of network architecture. A basic distinction must be made between ring structures with unidirectional and bi-directional connections.

Unidirectional rings: Below figure shows the basic principle of APS for unidirectional rings. Let us assume that there is an interruption in the circuit between the network elements A and B. Direction y is unaffected by this fault. An alternative path must, however, be found for direction x. The connection is therefore switched to the alternative path in network elements A and B. The other network elements (C and D) switch through the back-up path. This switching process is referred to as line switched. A simpler method is to use the so-called path switched ring. Traffic is transmitted simultaneously over both the working line and the protection line. If there is an interruption, the receiver (in this case A) switches to the protection line and immediately takes up the connection.

Protection of network

Two fiber unidirectional path switched ring

Bi-directional rings: In this network structure, connections between network elements are bi-directional. This is indicated in below figure by the absence of arrows when compared with figure 18. The overall capacity of the network can be split up for several paths each with one bi-directional working line, while for unidirectional rings, an entire virtual ring is required for each path. If a fault occurs between neighboring elements A and B, network element B triggers protection switching and controls network element A by means of the K1 and K2 bytes in the SOH.

Bi-Directional

Two fiber bi-directional line-switched ring (BLSR)

Even greater protection is provided by bi-directional rings with 4 fibers. Each pair of fibers transports working and protection channels. This results in 1:1 protection, i.e. 100 % redundancy. This improved protection is coupled with relatively high costs.

Conclusion

Customer can not accept network failure at any cost so it is very necessary to provide the "Back-up network switching".It is depend upon the protection architecture of the network. With the help of "Back-up network switching" network re-installation can be provided as soon as possible. How's this post, please comment me inbox.