Hierarchical (multi-core) Wavelength Division Multiplexing (WDM) networks present
a challenging design problem to the network designer who wishes to establish all-optical circuits
end-to-end and across multiple network cores. Due to the nature of the hierarchical structure and its
traffic distribution, it is likely that the inner core requires more capacity when compared to the capacity
required by the metro cores, which are individually connected to the inner core. This capacity
mismatch cannot be addressed by assigning distinct transmission rates to each core, as this solution
would result in using electronic time division add-drop multiplexer to interconnect the traffic across
cores with distinct rates.
An alternative solution to addressing the capacity mismatch betweenWDM metro and inner core
is explored in this paper, which is based on a limited number of wavelengths (a subset of the full set)
being used in the metro core, when compared to the full set of wavelengths being used in the inner
core. Two available architectures are presented in the paper, discussing their respective advantages
The paper studies the impact of OXC equipment failure in WDM networks with dynamic end-to-end optical circuit provisioning. At the OXC level, equipment reliability is calculated using proven component level reliability models. At the network level, end-to-end optical circuits are provisioned with various levels of reliability, thus
offering differentiated reliability to applications. The desired reliability level is obtained via shared path protection (SPP) switching, that provides efficient resource utilization. A selection of representative OXC architectures is examined to assess the influence of various switching technologies on the overall network level reliability. The selected OXC architectures are compared in terms of both the cost of switching equipment and the ability of the
network to accommodate incoming circuit requests, while satisfying their required reliability level.
Differentiated Reliability (DiR) is a concept that was recently introduced by the authors. The DiR concept can be applied to provide multiple reliability degrees (or classes) at the same network layer, using a desired protection scheme, e.g., dedicated path
protection switching. According to the DiR concept, each connection is
guaranteed a minimum reliability degree, or equivalently a maximum downtime ratio, that is chosen by the client. The reliability degree chosen for a given connection is thus determined by the application requirements, independently by the actual network topology, design constraints, robustness of the network components, and span of the connection. In this paper, two protection schemes are used to
provide DiR in a WDM network with arbitrary topology: the path protection scheme and the partial path protection scheme. With either scheme, differentiation of reliability is successfully achieved. It is noted that the latter scheme is 10% more resource efficient than the former scheme in providing the desired reliability level. The former scheme is however less complex to manage than the latter.
Survivability to faulty components and simplified management
drive the practical deployment of ring-based WDM networks.
In many applications, location constraints and user
scalability require that multiple rings are
interconnected to form a single large network.
Survivability of connections spanning across multiple
rings is then achieved by resorting to dual-interconnection,
i.e., two (or more) nodes are available to crossconnect the
inter-ring traffic between two neighboring rings.
By providing one backup crossconnect-node
to be used in case of failure of the primary
crossconnect-node, network wide connectivity
is thus guaranteed also in presence of any faulty node.
This paper addresses the problem of optimally provisioning
both bandwidth and crossconnect ports required to satisfy
a set of traffic demands in a dual-interconnected
WDM dual-ring network architecture.
The problem is solved under two design scenarios.
In the first scenario, priority is given to
the minimization of the number of wavelengths.
In the second scenario, priority is given to
the balancing of traffic between the crossconnect-nodes.
Two efficient approaches are proposed that provide
a near-optimal solution in each considered scenario.
The discussed performance comparison provides the network designer with a
quantitative assessment of the trade-off between the two approaches.
A fundamental task of the optical layer in modern telecommunication systems consists of providing a fast protection mechanism against possible faults in the network. A particularly attractive protection technique in the optical layer is the so called shared line protection, in which network lines are protected using shared resources. A previous work of the authors formally describes the problem of minimizing the total wavelength mileage, or (lambda) -mileage, necessary in a Wavelength Routing network with arbitrary topology to provide shared line protection. This paper presents an efficient approach to solving the above wavelength mileage problem.
CATO (prototype CAD Tool for Optical Networks and Interconnects) performs DWDM network design, balancing costs and performance. CATO's interactive visual interface allows demand conversion; topology creation/editing; protection; lightpath routing and wavelength assignment; reduction and placement of OXC ports, (lambda) -converters, amplifiers, and other critical resources; network simulation; and graphical reporting. CATO combines novel heuristics with artificial intelligence, solving problems unique to optical networks, yielding dramatic savings, and running in half the time or less of tools based on linear programming. Thus, CATO can maximize performance, utilization, and survivability in real time, and is suited for management tasks.