Advantages of UNI/BI-directional Protection Switching

Many times we heard that we should implement Unidirectional or Bidirectional APS in the network.Just some of the advantages of these are:-

Unidirectional and bidirectional protection switching

Possible advantages of unidirectional protection switching include:

• Unidirectional protection switching is a simple scheme to implement and does not require a protocol.
• Unidirectional protection switching can be faster than bidirectional protection switching because it does not require a protocol.
• Under multiple failure conditions there is a greater chance of restoring traffic by protection switching if unidirectional protection switching is used, than if bidirectional protection switching is used.

Possible advantages of bidirectional protection switching when uniform routing is used include:

• With bidirectional protection switching operation, the same equipment is used for both directions of transmission after a failure. The number of breaks due to single failures will be less than if the path is delivered using the different equipment.
• With bidirectional protection switching, if there is a fault in one path of the network, transmission of both paths between the affected nodes is switched to the alternative direction around the network. No traffic is then transmitted over the faulty section of the network and so it can be repaired without    further  protection switching.
• Bidirectional protection switching is easier to manage because both directions of transmission use the same equipments along the full length of the trail.
• Bidirectional protection switching maintains equal delays for both directions of transmission. This may be important where there is a significant  imbalance in the length of the trails e.g. transoceanic links where one trail is via a satellite link and the other via a cable link.
•  Bidirectional protection switching also has the ability to carry extra traffic on the protection path.

@above is extracted form ITU-G.*841