Network-on-Chip (NoC) architectures are emerged as a promising solution to the lack of scalability in Multi-Processor Systems-on-Chips (MPSoCs). With the explosive growth in the usage of multimedia applications, it is expected that NoC serves as a multimedia server supporting multi-class services. This paper addresses rate control problem for applications with scalable multimedia services in Network-on-Chip architectures. Scalable multimedia applications are relying on multi-class services which use layered encoding schemes. We formulate the rate control for multimedia with multi-class services using the optimization approach. This allows us to devise an iterative rate control algorithm as the solution to the optimization problem. The rate control algorithm can be implemented using a controller with low computational overhead. The validity of the obtained expressions is demonstrated by comparing results predicted by the analytical model against those attained through extensive simulation experiments.