Network Fault Tolerance by Means of Diverse Physical Layers

Wired networks are deployed in scenarios requiring the highest levels of performance in terms of reliability and timeliness. Unfortunately, broken wires might permanently compromise the network operation unless fault tolerance mechanisms are in place. Fault tolerance is commonly achieved by replicating the wired network components, but this paper examines the use of a wireless backup network, since the wireless physical layer (PHY) is not expected to display permanent failures due to broken wires. Two mechanisms at medium access control (MAC) level are presented to take advantage of the wireless backup network: one allocating redundancy statically and one dynamically. Without loss of generality, redundancy is applied using the standard mechanisms from IEEE 802.3 (Ethernet) and IEEE 802.11 (Wi-Fi). The performance increase added by the backup network is studied both analytically and by simulation, showing considerable improvements in a very compromised midsize wired network.