HEDGE: Traffic Engineering with Probabilistic Link Capacities

Cloud providers have adopted higher modulation formats to achieve higher data-rate wavelengths in their optical wide-area networks. However, higher modulation formats reduce signal quality margins, making wavelengths more susceptible to wavelength-specific faults (WSFs)—temporary faults that selectively affect certain wavelengths while others remain unaffected, even though they all share the same optical fiber and equipment. WSFs cause the capacity of inter-datacenter links to fluctuate, frequently disrupting traffic engineering systems. We propose HEDGE, a system that mitigates the effects of WSFs by implementing link-local resilience and global network-wide resilience against WSFs. For local resilience, HEDGE provisions inter-datacenter links with a guaranteed minimum capacity and availability target, in spite of WSFs, while using the fewest possible constituent wavelengths. For global resilience, HEDGE optimally balances throughput and availability while allocating flows on a stochastic wide-area network with fluctuating link capacities. HEDGE sustains equivalent throughput with state-of-the-art traffic engineering systems, while dropping 12.2× less network flow in worst-case scenarios and reducing disruptions to tunnel allocations by 622× in spite of a rapidly changing topology.