In order to achieve high availability of network services, alternative links between the network components provide backup path. For example, offering a network access to a plurality of hosts using protocols at any one of the layers 3 to 7 of the Open Systems Interconnection (OSI) model is conventionally implemented using a protection mechanism on layer 2 of the OSI model, which provides the alternative links or backup paths. Such protection mechanisms include Ethernet Ring Protection (ERP), Link Aggregation (LAG), Spanning Tree Protocol (STP), Multi-Protocol Label Switching Transport Profile (MPLS-TP), etc.
When a link failure is detected in the network, data traffic previously traversing the failed link has to be rerouted immediately using the alternative one or more links forming the backup path and avoiding the failed link. The protection mechanism may be triggered by deleting entries in a table associating Medium Access Control (MAC) addresses and switch ports. Entries that relate to MAC addresses and/or switch ports potentially affected by the link failure are deleted. Some of the protection mechanisms, e.g., ERP, LAG or MPLS-TP, complete all operations for rerouting the data traffic to the backup path in a very short time, e.g., within 50 ms or less. Hence, the network service provided to the host fulfills a certain Quality of Service (QoS) requirement. For example, the QoS requirement may specify that glitch is less than 50 ms for a network service providing an audio conversation.
However, the deleted MAC entries are relearned not until a data frame including the corresponding source MAC address is received by switches along the backup path. As long as no corresponding entry exists for a data frame to be forwarded at a switch, the switch floods the data frame, i.e., the data frame is sent at all of its switch ports except for the switch port at which the data frame was received. Consequently, unnecessary flooding consumes network bandwidth. Furthermore, some network components may set a limit, e.g. 10% of the total bandwidth, for flooded data traffic. Consequently, the QoS may be compromised before the corresponding MAC address is relearned, e.g., even in the presence of fast protection switching mechanisms.