A Novel Architecture and Flow Control Scheme for Private ATM Networks

Abstract

The primary performance measures used to evaluate any congestion control algorithm applicable to ATM networks are, the utilization achieved and the guaranteed packet loss or the Grade of Service (GOS). In any scheme where the sources are controlled there has to be a compromise between the throughput and the GOS, introduced due to the burstiness of the sources. This trade-off can be reduced by the effective use of buffers along with a fair and adaptive flow control scheme. This paper proposes such a scheme, including a node architecture with an off-line shared buffer. In combination with this architecture a threshold controlled, backward notification flow control algorithm is introduced. The off-line buffer is used to absorb reasonable sized overloads, thus increasing the utilization of resources. Extended overloads generate control messages and are flow controlled, thus avoiding unacceptable degradation in the GOS. Flow control messages are relayed back only if the source is truly violating. Hence the proposed scheme is fair and precludes flooding of the network with control messages and the possibility of oscillation in reporting the network status. The issues surrounding this scheme are discussed and possibilities of further research are presented. A simulation model with some results are provided to support our claims.