Pudica: Toward Near-Zero Queuing Delay in Congestion Control for Cloud Gaming

Congestion control (CC) plays a pivotal role in cloud gaming services. However, existing CC methods often cause selfinduced bottleneck queuing. As a result, they may largely delay game frame transmission and undermine the player's gaming experience. We present a new end-to-end CC algorithm named Pudica that strives to achieve near-zero queuing delay and high link utilization while respecting cross-flow fairness. Pudica introduces several judicious approaches to utilize the paced frame to probe the bandwidth utilization ratio (BUR) instead of bandwidth itself. By leveraging BUR estimations, Pudica designs a holistic bitrate adjustment policy to balance low queuing, efficiency, and fairness. We conducted thorough and comprehensive evaluations in real networks. In comparison to baseline methods, Pudica reduces the average and tailed frame delay by 3.1× and 4.9× respectively, and cuts down the stall rate by 10.3×. Meanwhile, it increases the frame bitrate by 12.1%. Pudica has been deployed in a largescale cloud gaming platform, serving millions of players. Sender Router 𝑡 ! 𝑡 " Cross traffic Our flow Probe packet 𝑡 ! in out Sender Receiver Router in out (a) Bursty flow w/o cross traffic (b) Paced flow w/ cross traffic Receiver 𝑡 " Next frame