EFAH: An energy and fatigue aware heuristic for provisioning highly available connections in optical backbone networks

Optical backbone operators need to meet the availability requirements specified in the Service Level Agreements (SLAs). While less stringent availability constraints, i.e., less than three 9's might be met by provisioning connections without any protection, more stringent requirements, i.e., five 9's, force operator to use proactive protection strategies. The connection provisioning process becomes more cost-efficient when green aspects are considered. On the other hand, energy awareness introduces thermal fatigue effects, which may in turn lower the lifetime of devices that undergo frequent power state transitions, i.e., between Active Mode (AM) and Sleep Mode (SM). As a result the availability level experienced by the unprotected connections may decrease. At the same time, with devices failing more frequently the protection level chosen for a given connection might not be enough to guarantee the required average connection availability performance. This work tackles the problem of managing an optical back-bone network when green and thermal fatigue aspects are introduced. We propose an Energy and Fatigue Aware Heuristic (EFAH) that is able to balance between thermal fatigue effects and energy saving performance. When compared to the pure Energy-Aware (EA) strategies, EFAH manages to significantly improve the value of the average connection availability of both unprotected and protected connections. On the other hand, there is a price to pay in terms of lower energy saving performance.