A Scalable Bandwidth Management Architecture for Supporting VoIP Applications Using Bandwidth Broker

Voice over IP (VoIP) is a promising service of the future Internet. It could provide users with new features in a costeffective way. However, such a service poses, as other realtime applications do, new challenges on the ways of provisioning and engineering the networks. On the data plane (i.e., packet forwarding plane), sufficient resources need to be deployed and adequate mechanisms need to be employed at each router. For this purpose, over the last decade or so, plenty of scheduling algorithms have been proposed and studied (see, for example, [2, 5] and the references therein). On the other hand, on the control plane, scalable and efficient network resource allocation and management schemes must be employed in order to provide quality of service guarantees to satisfy the diverse service requirements of different networking applications, like VoIP. Because of the communication, storage, and processing overhead imposed on a network’s core routers by the distributed bandwidth allocation and management schemes (e.g., RSVP), a centralized model based on the notion of Bandwidth Broker [1] was proposed in the IETF DiffServ framework for bandwidth management. Using a centralized bandwidth broker, core routers of a network are relieved from the control plane tasks for allocating network resources and managing QoS states, thereby achieving a simpler and more efficient packet forwarding data plane. However, the centralized bandwidth broker model for QoS control and management also introduces its own scalability issue [3] , in particular, the ability of the bandwidth broker to handle large volumes of flows as the network system scales. For example, to support VoIP applications, it may be necessary to conduct dynamic QoS control and management such as admission control and/or resource provisioning at the time scale of flow arrival and departure. In these circumstances, an inappropriately centralized bandwidth broker system can become a potential bottleneck, limiting the number of flows that can be accommodated into the network system, while the network system itself is still under-loaded. In this paper, based on a path-oriented quota-based bandwidth allocation algorithm introduced in [4], we present a scalable bandwidth allocation and management scheme for supporting VoIP applications. In the path-oriented quotabased algorithm, network resources are represented in the bandwidth broker in two levels: a path QoS state database representing the path-level QoS states and a link QoS state database representing the link-level QoS states of a network domain. Moreover, bandwidth is allocated to paths in units of quota (which is much larger than a typical flow bandwidth request) instead of on a per-flow basis. By such a quota based chunk bandwidth allocation scheme, most of the flow requests can be handled at the path level without consulting the more time-consuming link level resource management module, therefore improving upon the scalability of the centralized bandwidth broker.