RADIC-TCP: High-speed protocol applied for virtual private WAN

TCP communication has the feature that decreases the throughput over a virtual private WAN between global offices, which has larger delay and causes packet loss at higher frequency than LAN. This paper proposes a high-speed original TCP applied for a virtual private WAN: RADIC-TCP (RTT — And — Discard — Independent Congestion control TCP). RADIC-TCP comprises of following three features: the bandwidth control using token size to limit the size of send data by each constant interval of time independent of RTT, rapid retransmission of all discontinuous loss segments using one time NACK and congestion control based on change rate of packet loss ratio. By using these three techniques, RADIC-TCP achieves large throughput communication independent of RTT and packet loss ratio over a virtual private WAN. We implemented the proxy applying RADIC-TCP for a normal PC, and evaluated the throughput of RADIC-TCP in an experimental environment. In the experimentation to emulate a general WAN (100 Mbps, 200 ms RTT, 0.1 % loss), the file transmission of single FTP user over RADIC-TCP achieves 93 Mbps throughput equal to 25 times of the throughput over CUBIC-TCP, when send/receive buffer size is set to 16 Mbytes. When using RADIC-TCP with other conventional TCP communications, the bandwidth allocated for RADIC-TCP can be controlled under a pre-set threshold to protect other conventional TCP communications. When the bandwidth allocated for RADIC-TCP is limited up to 10Mbps, the file transmissions of 50 FTP users were completed at the same time by dividing the 10Mbps bandwidth fairly, while saving the bandwidth of 90 Mbps for other conventional TCP communications.