A flow control sender includes an ingress port with one or more Class Groups (CG) defined including a shared buffer pool, a shared counter per ingress port per CG tracking an amount of the shared buffer pool utilized by each CG, an ingress port utilization counter per ingress port tracking an amount of the shared buffer pool utilized by the ingress port, and a controller computing a dynamic threshold for each CG, comparing the dynamic threshold of each CG with the ingress port utilization counter, and determining a particular CG experiencing congestion when the ingress port utilization counter is greater than the dynamic threshold for the particular CG. A flow control receiver ceases transmission of data packets to the particular CG experiencing congestion and allows transmission of the data packets corresponding to other CGs.