LOSSLESS CONNECTION FAILOVER FOR MIRRORED DEVICES

摘要

The WAN optimization devices delay ACK until the ACK is actually received from the target while opening up the TCP window. When the ACK is received and forwarded, the TCP window is reduced in size. If there are mirrored WAN optimization devices, the original WAN optimization device sends the datagram across the WAN and at the same time sends the datagram to the mirroring WAN optimization device. When the mirroring WAN optimization device ACKs the mirrored datagram, the original WAN optimization device ACKs the host. When the ACK across the WAN is received, the mirroring WAN optimization device gets the ACK forwarded and deletes the mirrored datagram. On a loss of a device, the TCP connection transitions to the mirroring WAN optimization device, which closes the LAN TCP window and transmits all un-ACKed data. Then upon success the mirroring WAN optimization device reopens the LAN TCP window.