Proxy Server Packet Acknowledgment for QUIC Congestion Control

The proxy server performs preliminary acknowledgment by sending ACK frames to the sender before the packet is actually delivered to the receiving device. This preliminary action allows the sender to continue transmitting packets without waiting for actual delivery confirmation, thereby maintaining high network throughput while the proxy retains packets for later delivery, resolving the contradiction between reliability and productivity.

The proxy server acts as an intermediary between the sender and receiving device, buffering packets temporarily to enable effective congestion control. By decoupling the acknowledgment timing from actual delivery timing, the proxy allows congestion control to function properly based on buffered packet management while maintaining the illusion of continuous delivery to the sender, thus balancing congestion control effectiveness with acceptable delivery time.

The proxy server implements beforehand cushioning by maintaining a buffer of acknowledged but undelivered packets. This buffer acts as a safety cushion that allows the system to tolerate proxy failures or delays without causing actual packet loss, since the sender has already been notified of delivery and can retransmit only if necessary, thus protecting sender productivity while maintaining reliability.