Traffic descriptor mapping and traffic control for frame relay over ATM network

Frame relay (FR) service via an FR interface over a common asynchronous transfer mode (ATM) backbone network requires an FR-to-ATM interworking unit (IWU), the functionality of which directly impacts the engineering of the overall network in terms of the capacity required, quality of service (QoS) expected, and the interference among different types of services being offered on the same platform. In the absence of a traffic shaping function in the equipment at the customer´s location, the issue of policing and bandwidth allocation becomes much more critical. This paper focuses on the issue of FR traffic descriptor mapping, the issue of traffic policing in the frame mode and the cell mode, and the implication on the QoS when the same bandwidth resources are shared by the ATM [cell relay (CR)] and FR virtual connections. Some major conclusions that we draw from the computer simulations are: (1) the performance is somewhat independent of the mode in which traffic policing is implemented; (2) from a cost standpoint it is more advantageous to use the cell mode for traffic policing; (3) the allocation of bandwidth in the multiplexer and the switching fabric is greatly dependent on the type of service interface used since the FR traffic becomes much burstier after frame-to-cell conversion process; and (4) it becomes necessary to provide a traffic shaping function after the conversion process in order to achieve high bandwidth utilization, fair allocation of bandwidth resources, and guaranteed QoS