  In this paper, we study the influence of technology, traffic properties and
price trends on optimized design of a reference IP-over-WDM network with rich
underlying fiber topology. In each network node, we investigate the optimal
degree of traffic switching in an optical (lambda) domain versus an electrical
(packet) domain, also known as measure of node transparency. This measure is
studied in connection to changes in traffic volume, demand affinity, optical
circuit speeds and equipment cost. By applying variable design constraints, we
assess the relative roles of the two distinct equipment groups, IP routers and
optical cross-connects, with respect to resulting changes in cost-sensitive
network architectures.
