Inferring and Controlling Congestion in CCN via the Pending Interest Table Occupancy

Despite the improvements brought about by content-centric networking's (CCN) in-network caching and interest aggregation, congestion can still take place in such networks due to the dominance of non-reusable content, high cache churn, high delay variations, premature timeouts and interest retransmission. This becomes even more dramatic when multi-path routing is adopted. Identifying that at a given node in CCN, the Pending Interest Table (PIT) occupancy can give a good estimate of the data workload to arrive to the node in the near future, we propose in this paper a novel mechanism to control congestion in CCN based on this idea. Our mechanism uses the average occupancy of the PIT to estimate the anticipated data packet transmission queue length and sends explicit congestion notification signals to the content requesters to reduce their interest sending rates when such anticipated queue size exceeds a threshold. We demonstrate the effectiveness of our proposed mechanism via ns-3 simulation.