OPTIMAL PROVISIONING OF OPTICAL NETWORKS WITH ASYMMETRIC NODES

Wavelength Switched Optical Networks (WSONs) have been designed to take advantage of all optical switching fabrics with a high level of automation and efficiency. Therein, the Wavelength Selective Switches (WSS) represent the core switching elements with a technology enabling multi-degree Reconfigurable Optical Add\Drop Multiplexers (ROADM) architectures with colorless and directionless switching. In this paper, we propose an optimization model to establish the best ROADM switching connectivity to maximize the grade of service, for a given number of ports. We show that the grade of service can vary significantly, up to 30%, depending on the switching connectivity. Besides, the larger the network is, the more the variance increases: from 20% to 30%, when the number of nodes varies from 14 to 24.

Modeling of Clos Switching Structures with Dynamically Variable Number of Active Switches in the Spine Stage

This article proposes a new analytical model of a switching structure using a Clos network topology. The assumption is that, in the structure under consideration, it is possible to switch off temporarily a certain number of spine switches (those in the middle stage of the switching fabric) depending on the current intensity of the offered traffic to reduce power consumption. The solution presented in the article can be used in present-day multiservice switching fabrics and in networks connecting servers in data centers. The developed analytical model allows the value of blocking probabilities for different stream classes of multiservice traffic to be evaluated in switching structures (switching fabrics) with a variable number of switches in the middle stage. The results obtained on the basis of the analytical model are compared with the results obtained as a result of relevant simulation experiments for a selected structure of the switching fabric. The study confirms high accuracy of the proposed model. This model can be used in further works to evaluate the effectiveness of energy-saving switching fabrics and the networks of data centers, as well as to construct energy-saving control algorithms that would control these switching structures, that is, algorithms that would change the topology of the switching fabric depending on changes in the offered traffic.

Rearrangeable and Repackable S-W-S Elastic Optical Networks for Connections with Limited Bandwidths

Elastic optical networks flexibly allocate bandwidth to a connection for improving utilization efficiency. The paper considers an optical node architecture that is similar to a three-stage Clos network for elastic optical networks. The architecture, which employs space switching in the first and the third stages and wavelength switching in the second stage, is called an S-W-S switching fabric. In this paper, we propose a graph-theoretic approach and different routing algorithms to derive the sufficient conditions under which an S-W-S switching fabric will be rearrangeable nonblocking and repackable nonblocking. The proposed rearrangeable and repackable nonblocking S-W-S switching fabrics for connections with limited bandwidths consume around half the number of middle wavelength switches compared to strictly nonblocking S-W-S switching fabrics.

Strict-Sense Nonblocking Conditions for the log2⁡N-1 Multirate Switching Fabric for the Discrete Bandwidth Model

The article discusses the strict-sense nonblocking conditions derived for the log2⁡N-1 multirate switching fabric for the discrete bandwidth model at the connection level. Architecture of the log2⁡N-1 switching fabric was described in previous study; however, conditions for the multirate discrete bandwidth model as well as comparison with different structures have not been published before. Both sufficient and necessary conditions were introduced and proved in this study. A few numerical examples which help to understand an idea of the multirate bandwidth model for the log2⁡N-1 switching fabrics were delivered as well. Additionally a comparison of achieved results to the banyan switching structures and a comparison of the costs of all mentioned in this study structures expressed as the number of optical elements were done.