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... [continues]
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