The Internet faces well-known challenges in realizing modifications to the core architecture. To help overcome these limitations, the use of network virtualization has been proposed. Network virtualization enables the deployment of novel network architectures and services on existing Internet infrastructure. Virtual networks run over physical networks and use Internet paths and protocols as essentially a link layer in the virtual network. Virtual networks can also share the resources in the physical substrate. Effective use of the underlying substrate network requires intelligent placement of virtual networks so that underlying resources do not incur over-subscription. Because virtual networks can come and go over time, and underlying networks can experience their own dynamic changes, virtual networks need to be migrated---re-mapped to the physical network during active operation---to maintain good performance. While virtual network placement, and to a lesser extent migration, has been studied in the past, little attention has been devoted to designing, deploying, and evaluating migration mechanisms for virtual networks. In this dissertation, we design virtual network migration mechanisms for different substrate platforms and further design a system to mitigate the effects of virtual network migration. In particular this dissertation makes the following contributions: 1. With the goal of minimizing the disruption during a virtual network migration, we design three algorithms for scheduling the sequence of virtual router moves that takes a virtual network from its original placement to its new placement. 2. We design and implement a controller-based architecture for virtual network migration on PlanetLab. This work explores the challenges in implementing virtual network migration on real infrastructure. Recommendations are given for infrastructure that support virtual network migration. 3. We propose and implement a mechanism to mitigate the performance degradation resulting from virtual network migration through transport and application layer collaboration. We utilize a centralized controller to notify the end-systems or the gateways about the time of the virtual network migration such that we prevent packet loss to the application traffic of the end-systems.

This paper analyses the role of the spatial structure of migrant networks in the location decision of migrants to the European Union at the regional level. Using a random parameters logit specification, a significant positive effect of migrant networks in neighbouring regions on migrants' location decisions is found. Although this spatial spillover effect is smaller than the effect of networks in the host regions, omitting to control for this spatial dependence results in a 40% overestimation of the effect of regional migrant networks on the location decision of newly arriving migrants.

By 2020 there will be 50 billion connected devices over the Internet. With the fast-increasing data traffic demand in both fixed and mobile networks, network operators need to migrate networks towards next generation solutions. The network migration requires the enormous investment in equipment and infrastructure, while the revenues are not expected to grow significantly. Therefore, one of the main challenges for network operators is to find out a proper cost-effective optical network solution that can match future high capacity demand and flexibly support multiple network services on a common network infrastructure. The first part of the thesis addresses the Active Optical Network (AON) and its migration strategies towards Next Generation Optical Access (NGOA) solutions. Several migration strategies are proposed from the perspective of network topology, data plane and control plane. A general methodology for Techno-Economic analysis has been developed and applied to the Total Cost of Ownership (TCO) calculation of different NGOA solutions. The thesis provides a complete cost evaluation of AON migration paths, which can be used by network operators to assess the economic feasibility of network migration. A converged Optical Transport Network (OTN) that can serve both fixed and mobile network services is beneficial from the cost-saving perspective. However, the different types of services, require different network performance. The second part of the thesis focuses on the investigation of the converged OTN that can be flexibly and timely adjusted to satisfy varying service conditions. A programmable OTN featured with Wavelength Division Multiplexing (WDM) in the data plane and Software Defined Networking (SDN) in control plane has been proposed. To demonstrate the benefits of the converged OTN, the thesis also provides a multi-domain orchestration architecture for the multiple network services.  The resource orchestration, across three network domains: OTN, mobile network and cloud, enables agile service creation and optimized resource allocation among the multiple domains. / <p>QC 20170512</p>