The proposed congestion notification strategy for SMDS networks presented in this paper is based on explicit notification, which uses control messages to inform other network elements of congestion. Network elements respond to explicit notifications by matching the traffic entering the network to the network loading. For an effective congestion management strategy, the notifications should carry sufficient information about the congested resource so that the notified switching systems (SSs) may reduce traffic towards the congested SS. Since the internal architecture of an SS is not visible to other SSs in the network, the congestion notification mechanism maps the SS resource congestion to path congestion, identified by open interfaces such as the inter-SS, intercarrier, and customer-to-network interfaces, which are visible to all SSs in the network.>