Unicast and Multicast QoS Routing with Soft-Constraint Logic Programming
We present a formal model to represent and solve the unicast/multicast routing problem in networks with quality-of-service (QoS) requirements. To attain this, first we translate the network adapting it to a weighted graph (unicast) or and-or graph (multicast), where the weight on a connector corresponds to the multidimensional cost of sending a packet on the related network link: each component of the weights vector represents a different QoS metric value (e. g., bandwidth). The second step consists in writing this graph as a program in soft-constraint logic programming (SCLP): the engine of this framework is then able to find the best paths/trees by optimizing their costs and solving the constraints imposed on them (e. g. delay <= 40 ms), thus finding a solution to QoS routing problems. C-semiring structures are a convenient tool to model QoS metrics. At last, we provide an implementation of the framework over scale-free networks and we suggest how the performance can be improved. The article highlights the expressivity of SCLP.
routing constraints languages measurement theory soft constraints preferences quality of service (qos) constraint logic programming (clp)