CONGESTION NOTIFICATION IN LEAF AND SPINE NETWORKS

Methods and systems to alleviate congestion in leaf and spine network topologies. Control information may be advertised by spines regarding the leaves to which it is connected. The control information is advertised to other leaf switches connected to the advertising spine. The control information may include a destination leaf ID, an enroute spine ID, an FL flag and an FF flag. The FL flag is a "Flow Learn Flag," that is set by the advertising spine that a leaf switch toward which the spine may be facing congestion above at a first predetermined threshold level. The FF flag is a "Flow Freeze Flag," that is set when all links to the corresponding destination leaf identified are congested, and the congestion level has crossed a second predetermined threshold level.