Stability of Virtual Network Topology Control for Overlay Routing Services

Initiating a discussion on the stability provided by Virtual Network Topology (VNT) control for overlay networks that are able to provide dynamic routing updates, this paper finds that the dynamics of such routing on overlay networks causes high fluctuation in the traffic demand matrix. This causes VNT control instability and considers the need for three extensions?hysteresis, two-state utilization hysteresis, and filtering, to VNT control. Overlay networks have the ability to provide new functionalities and enhance network performance. They do this by ensuring that routing is managed at the application layer. Although, this paper suggests, this approach may result in degradations of underlying networks because the overlay networks tend to take over. Simulation results in the paper show that while hysteresis mechanism enhances stability of a network, it cannot always improve network performance. This paper attempts to extend the hysteresis mechanism and shows that it can enhance network stability along with performance. This extension would need a lot of time before VNT is able to arrive at a stable state. For fast convergence, this paper uses a filtering method for VNT control. The paper also discusses a Wavelength Division Multiplexing (WDM) network that provides a flexible network infrastructure. It uses the wavelength-routing capability where optical transport channels or lightpaths are established between nodes via optical cross-connects (OXCs). This paper also discusses how the dynamics of overlay routing result in high fluctuations in traffic demand.