Buffering and prioritization in switches for fast processing table‐miss packets in software‐defined networks

Summary In software‐defined networks, the switch forwards incoming packets according to forwarding rules recorded in the flow entries. When a switch receives a table‐miss packet, meaning no match with any flow entry, it sends this packet as a Packet‐In message to the controller for its further processing. Many Packet‐In messages will cause large overhead and long packet delay. This paper proposes a novel method, Packet‐In Buffering and Prioritization (PIBP), which buffers Packet‐In messages and prioritizes these messages to reduce the number of Packet‐In messages and accelerate their processing, respectively. The concept of PIBP is sending only the first table‐miss packet of each flow to the controller. The other table‐miss packets belonging to the same flow are temporarily stored in the switch. Moreover, these messages have a higher priority. That is, after the packet sent from the controller has been forwarded from the switch, the buffered packets belonging to the same flow are also immediately forwarded. We formally analyze the performance of PIBP with queuing theory. The analytical and simulation results show that PIBP can decrease the average delay of table‐miss packets compared with two typical methods, Priority Queue and Mismatched Packets Table. PIBP can achieve a better performance in comparison with the PQ method, no matter what value of packet arrival rate in each flow and flow arrival rate. When the controller is more congested, PIBP can get larger improvements compared with PQ. On the other hand, PIBP can outperform MPT when the switch does not have enough capacity to process packets soon. Finally, the accuracy of the proposed analytical model for PIBP has been validated through simulation.