Segment protection

consists of nodes C, D, E, and F. Lets assume that link B-C failed.

This type of protection allows node C to fail and for the backup of segment

In the long term it is more cost efficient to implement overlapping segment protection because the a provisioned circuit's availability would be much higher.

Shared segment protection allows a more efficient network to be deployed.

The "working path" diagram illustrates the dedicated-overlapping segment protection.

Although the networks provided here as examples are simple the benefits of sharing are noticeable.

In the previous example we can see that a new backup segment protection is not necessary for each working path.

When this scheme is scaled to a large network a substantial cost improvement can be seen.

Another important parameter is the number of hops or distance that each segment should have to have an optimal network.

Although there is no secret number that would work for any network, there have been studies which show their experiment results.

[3] Generalized Segment Protection "The algorithm works as follows: K working paths are selected based on a predetermined criterion (shortest path, minimum unavailability, shortest hop count, etc.).

The cost of every link that has at least one spare channel is degraded by a negligible coefficient ε.

Upon obtaining the path, the modified links are restored, and the connection is provisioned with the corresponding backup segments"[2][4][5]