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Failure recovery using vlan-tag in SDN: High speed with low memory requirement

To achieve high availability, fault tolerance is desirable for most networks, including Software Defined Networks (SDNs). Link and switch failures are commonly observed in SDN, severely affecting the network performance and even making the whole system break down. In this paper, we propose a protection-based recovering method for link failures using vlan-tag, which is fast with low memory consumption. Inheriting from protection mechanism, our method is able to react and recover quickly without the participation of controller(s) by immediately switching to the backup path(s) precomputed when failure occurs. More importantly, it is memory efficient as it calculates the backup based on each link (instead of each flow), and simply assigns a vlan-id for each link, avoiding the high memory (TCAM used for flow table storage is costly) requirements of conventional protection methods. The simulation results expose that our method can recover from link failures within 20 ms (on the average) like other protection approaches, while the restoration needs 50 ms (on the average). Moreover, in experimental environment our method requires 100 times less flow table entries' amount than the protection method based on each flow to store backup paths.