Handle Router Failures and Unpredictable Trafﬁc
T. V. Lakshman
Bell Laboratories, Lucent Technologies, Holmdel, NJ, USA
Massachusetts Institute of Technology, Cambridge, MA, USA
Abstract— We consider the realization of trafﬁc-oblivious routing in IP-over-Optical networks where routers are interconnected over a switched optical backbone, also called IP-over-OTN
(Optical Transport Network). The trafﬁc-oblivious routing we consider is a scheme where incoming trafﬁc is ﬁrst distributed in a preset manner to a set of intermediate nodes. The trafﬁc is then routed from the intermediate nodes to the ﬁnal destination. This splitting of the routing into two-phases simpliﬁes network conﬁguration signiﬁcantly , . In implementing this scheme, the ﬁrst and second phase paths are realized at the optical layer with router packet grooming at a single intermediate node only. Studies like  indicate that IP routers are 200 times more unreliable than traditional carrier-grade switches and average 1219 minutes of down time per year. Given this unreliability of routers, we consider how two-phase routing in IP-over-OTN can be made resilient against router node failures. We propose two different schemes for provisioning the optical layer to handle router node failures – one that is failure node independent and static, and the other that is failure node dependent and dynamic. We develop linear programming formulations for both schemes
and a fast combinatorial algorithm for the second scheme so as to maximize network throughput. In each case, we determine
(i) the optimal distribution of trafﬁc to various intermediate routers for both normal (no-failure) and failure conditions, and (ii) provisioning of optical layer circuits to provide the needed inter-router links. We evaluate the performance of the two router failure protection schemes (in terms of throughput) and compare it with that of...