NBBS PATH SELECTION FRAMEWORK

This paper describes the path selection function in Networking BroadBa nd Services (NBBS), which is ISM's architecture for high-speed, multim edia networks. The distinguishing feature of a multimedia network is i ts ability to integrate different applications with different traffic characteristics and service requirements in the network, such as voice , video, and data. In order to meet their service requirements, it is necessary for the network to provide unique qualify-of-service (QOS) g uarantees to each application. QOS guarantees, specified as multiple e nd-to-end performance objectives, translate into path and link constra ints in the shortest path routing problem. For a general cost function , shortest path routing subject to path constraints is known to be a n onpolynomial(NP-) complete problem. The NBBS path selection algorithm, a heuristic solution based on the Bellman-Ford algorithm, has a polyn omial order of complexity. The algorithm finds a minimum hop path sati sfying an end-to-end delay (or delay variation) constraint, that in mo st cases also optimizes a load balancing function. To reduce the numbe r of path constraints, other QOS requirements such as packet loss rati o are implemented as a link constraint. The notion of primary and seco ndary links is used to minimize the long-term overall call blocking pr obability by dynamically limiting the hop count of a given path. The p ath selection algorithm developed for point-to-point connections is de scribed first, followed by its extension to the case of point-to-multi point connections.