Network protection with multiple availability guarantees

We develop a novel network protection scheme that provides guarantees on both the fraction of time a flow has full connectivity, as well as a quantifiable minimum grade of service during downtimes. In particular, a flow can be below the full demand for at most a maximum fraction of time; then, it must still support at least a fraction q of the full demand. This is in contrast to current protection schemes that offer either availability-guarantees with no bandwidth guarantees during the downtime, or full protection schemes that offer 100% availability after a single link failure. We develop algorithms that provide multiple availability guarantees and show that significant capacity savings can be achieved as compared to full protection. If a connection is allowed to drop to 50% of its bandwidth for 1 out of every 20 failures, then a 24% reduction in spare capacity can be achieved over traditional full protection schemes. In addition, for the case of q = 0, corresponding to the standard availability constraint, an optimal pseudo-polynomial time algorithm is presented.