Brocade Communications Systems, Inc.

Ryan Hegland

Siva Adiraju

Amr Sabaa

Andy Dooley

Poulo Kuriakose

Hiren Desai

Amar Vutukuru

Isaac Larson

In a network where there are two local area networks (LANs) connected over a wide area network (WAN) by paralleled LAN to WAN devices at each end of the WAN, Transmission Control Protocol (TCP) connections may be requested by a first near end LAN to WAN device and received at a first far end LAN to WAN device but the acknowledgement may be returned to a second far end LAN to WAN device. The second far end LAN to WAN device contacts the first far end LAN to WAN device and the TCP connection is moved to the second far end LAN to WAN device, which provides the acknowledgement to the first near end LAN to WAN device to complete the TCP connection. Similar operations occur during active TCP connection operation but with certain queued data being flushed during the TCP connection transfer.

TCP connection relocation

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.

Lossless connection failover for mirrored devices

A system and method for sharing a WAN TCP tunnel between multiple flows without having head of the line blocking problem is disclosed. When a complete but out of order PDU is stuck behind an incomplete PDU in a TCP tunnel, the complete but out of order PDU is removed from the tunnel. To do that, first the boundaries of the PDUs of the different flows are preserved and the TCP receive window advertisement is increased. The receive window is opened when initially receiving out-of-order data. As out-of-order complete PDUs are pulled out of the receive queue, to address double counting, place holders are used in the receive queue to indicate data that was in the queue. As out-of-order data PDUs are pulled out of the queue the window advertisement is increased. This keeps the sending side from running out of TX window and stopping transmission of new data.

Transmission control protocol window size adjustment for out-of-order protocol data unit removal

Lossless connection failover for single devices

Growing community of inventors

Champlin, MN, United States of America

Ryan Hegland