Independent Relays in Overlays for Reliable Enterprise IP Telephony

Network QoS degradation can significantly impair the ability of networks to satisfy the stringent requirements of real-time applications such as IP telephony. Recently, we proposed a simple and practical overlay technique called ORBIT (overlays providing reliability for better IP telephony) that uses intelligent endpoints and independent relays. In the ORBIT architecture, the endpoints rapidly detect network QoS degradation and find better ";single-hop"; alternate paths (i.e., paths that traverse at most one relay). One key issue for ORBIT and single-hop overlays in general is how many relays to deploy and where to place these relays in the network for adequate protection against QoS problems. In this paper, we concentrate on enterprise networks and evaluate the benefits of random placement of relays. Our simulation study indicates that a small number of relays with respect to the network size is sufficient to achieve a high level of protection.