PhD defense of Amanvon Ferdinand ATTA on December 9th, 2021

Amanvon Ferdinand Atta defended his thesis on December9, 2021 at 8:30 am (GMT) in B3 room at Cocody Danga Campus of Institut National Polytechnique Félix Houphouët Boigny in Côte d’Ivoire. The title of the thesis is “Reconfiguration of Multicast Routing in Sparse Wavelength Converter Networks”. The direction of this thesis has been assured by Prof. Bernard Cousin and Prof. Souleymane Oumtanaga. The jury members were Michel Babri, Miklos Molnar, Eyouléki T. G. Palanga, Mouhamadou Dosso, Bernard Cousin, Souleymane Oumtanaga.


Optical networks using Wavelength Division Multiplexing (WDM) and wavelength conversion technologies are an efficient solution for very high-speed core networks. They make it possible to cope with the very high bandwidth and short delay requirements of applications such as telemedicine, distance learning, distributed computing, and online games. However, to reduce the costs of network dimensioning, it is quite practical that only some nodes of the network are equipped with wavelength conversion capability. Such a network is called a sparse wavelength converter network.

In the WDM networks, operators establish optical connections for their customers who need to use unicast or multicast applications. It is common for a customer, given the critical nature of its business, to require from the operator little or no interruption in the delivery of the optical flow it generates. In addition, following the occurrence of events such as an increase in connection requests, the network operator could be required to reconfigure the routing in order to improve network performance. However, the requirement for continuity of flow is not always easy to meet during the reconfiguration process if it is not done carefully. Reconfiguration becomes even more challenging for multicast routing in a WDM optical network with the property of partial wavelength conversion. Existing works address the reconfiguration of unicast or multicast connection routing in networks having the property of full wavelength conversion.

In this thesis, we deal on the one hand with the problem of reconfiguring the routing of a single multicast connection in a sparse wavelength converter network and on the other hand with the problem of reconfiguring the routing of a set of several multicast connections. In the first case, one aims to migrate the flow from an initial multicast routing to a final multicast routing without flow interruption. In the second case, we aim to migrate the optical flow from the initial multicast routing to the final multicast routing with a low number of flow interruptions. Note that the initial multicast routing and the final multicast routing are each supposed to be a set of light-trees.

The method denoted Para_SbSRA (Parallel Subtree by Subtree Reconfiguration Algorithm) has been proposed to solve the problem of routing reconfiguration relating to a single multicast connection and the methods LSRA (Light-tree Set Reconfiguration Algorithm) and LSRA_2 have been proposed to solve the problem of routing reconfiguration relating to a set of multicast connections. The effectiveness of these methods has been confirmed through simulations.

Keywords : Reconfiguration, flow interruption, multicast routing, WDM optical network, light-tree, wavelength conversion.