Due to quality of service and network usability issues, so called Two-Level networks may incorporate some additional constraints. In this work, we follow Current and Schilling and consider the Two-Level Network Design problem with an additional constraint on the distance between secondary nodes and the primary network. We propose a formulation that is slightly adapted from a formulation presented in Gouveia and Janssen. Computational results taken from instances with up to 50 nodes are also reported for this problem.

This presentation discusses an extension to the network design model where there in addition to the flow conservation constraints also are constraints that require design conservation. This means that the number of arcs entering and leaving a node must be the same. As will be shown the model has applications within the design of transportation networks. The model is solved using a Tabu Search heuristic using a hybrid of the add/drop procedure and cycle-based neighbourhoods.

The proposed talk will outline the basic concepts and advantages of the p-cycles technique for fast and efficient survivable optical network design. After reviewing the basic ILP models for optimal design of p-cycles for minumum spare capacity, and for joint optimization of working and spare capacity, we will touch on a number of heuristic alternatives and principles for approaching these and other p-cycle related desaign problems. Time permitting the talk will also review some recent extensions to the p-cycles concept including the protected working capacity envelope (PWCE) concept and ts related design problem, as well as a recent extension of p-cycles into end-to-end path-protecting structures. As fully pre-connected end-to-end path protecting structures the latter form of p-cycles are quite attractive for transparenbt optical networks where on-the-fly transparent cross-connection of optical channels is difficult to do with an assurance of transmission inegrity.