Some aspects of traffic management in frame relay networks

Frame relay is a high speed packet switching technology which has evolved as part of narrowband ISDN. The maximum link access speed is 2 Mbps, as in primary rate ISDN, and the access protocol is LAPD-based. Multiplexing of logical channels is therefore a layer 2 function which obviates the need for any layer 3 processing at network nodes. In addition, when frame relay is compared with X.25, only a sub-set of layer 2 functions are implemented in the network. The paper has proposed a call classification scheme which is considered to be appropriate for frame relay networks, and suggested how nodes which deal with such a traffic mix may be managed. A service mechanism has been proposed and a new congestion notification and recovery scheme which discards out-of-sequence frames in the network has been explained. The technique uses Recovery and Recovery Needed flags in frames and node switch tables, respectively. Further study of this new strategy is needed, but independently organised tests have indicated that it allows a node to maintain maximum throughput for a range of overload conditions