Bi-directional ABR mechanism (decreasing feedback delays)

The ABR mechanism was designed for controlling the traffic flows in ATM networks. The key factor for efficient and stable controlling of traffic control loops is fast transfer of feedback control information from the network back to the traffic source. In ABR mechanism so-called resource management (RM) cells are used for this purpose. The limited number of these control cells is especially noticeable in local area networks with negligible round trip time delays, when lower bit rates (less than 1 Mbit/s) are in question. Bi-directional ABR connections are composed of two independent unidirectional ABR connections each having its own flow of RM cells. Our proposal is to modify existing RM cells in such a way that each RM cell will be able to transfer control information for both directions at the same time. With the use of such modified RM cells and some modifications in network elements, the ABR control loop response time can be substantially reduced for a relatively small price. The number of RM cells in the network and therefore the amount of overhead information remains unchanged.