Lossless Connection Failover for Single Devices

• US 20130315253A1
• Filed: 11/15/2012
• Published: 11/28/2013
• Est. Priority Date: 12/06/2011
• Status: Active Grant

• Current Assignee: Avago Technologies International Sales Pte Limited (Broadcom, Inc.)
• Original Assignee: Brocade Communications Systems, Inc. (Broadcom, Inc.)
• Inventors: Sabaa, Amr, Hegland, Ryan, Adiraju, Siva
• Granted Patent: US 9,118,594 B2
• Time in Patent Office: Days
• US Class Current: 370/400
• CPC Class Codes: H04L 47/193 at the transport layer, e.g. TCP related
• CPC Class Codes: H04L 47/27 Evaluation or update of window size, e.g. using information derived from acknowledged [ACK] packets
• CPC Class Codes: H04L 47/33 using forward notification
• CPC Class Codes: H04L 47/40 using split connections
• CPC Class Codes: H04L 69/163 In-band adaptation of TCP data exchange; In-band control procedures

Abstract

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.

Claims

1. A method comprising:

receiving first TCP data at a wide area network (WAN) device from a source;

increasing the TCP window size to the source by the WAN device in conjunction with forwarding the first TCP data to the WAN by the WAN device;

receiving an ACK to the first TCP data from the WAN at the WAN device; and

forwarding the ACK to the first TCP data from the WAN to the source by the WAN device in conjunction with decreasing the TCP window size to the source.

2. The method of claim 1, wherein the increase and decrease in the TCP window size is based on the size of the first TCP data.

3. The method of claim 1, further comprising:

receiving a SYN at the WAN device from the source;

forwarding the SYN to the WAN by the WAN device;

receiving a SYN/ACK from the WAN at the WAN device;

forwarding the received SYN/ACK to the source by the WAN device;

receiving an ACK at the WAN device from the source; and

forwarding the ACK to the WAN by the WAN device,

wherein said operations develop the TCP connection of the first TCP data.

4. The method of claim 3, further comprising:

receiving second TCP data at the WAN device from the source prior to receiving an ACK to the first TCP data;

increasing the TCP window size to the source by the WAN device in conjunction with forwarding the second TCP data to the WAN by the WAN device;

receiving an ACK to the second TCP data from the WAN at the WAN device; and

forwarding the ACK to the second TCP data from the WAN to the source by the WAN device in conjunction with decreasing the TCP window size to the source.

5. The method of claim 4, wherein the increases and decreases in the TCP window size are based on the sizes of the first and second TCP data.

6. A wide area network (WAN) device comprising:

a plurality of network ports for coupling a WAN and to a source of TCP data;

a processor coupled to said plurality of network ports; and

a memory coupled to said processor and storing software which causes said processor to;

increase the TCP window size to the source in conjunction with forwarding first TCP data to the WAN in response to receiving the first TCP data from a source; and

forward an ACK to the first TCP data from the WAN to the source in conjunction with decreasing the TCP window size to the source in response receiving the ACK to the first TCP data from the WAN.

7. The WAN device of claim 6, wherein the increase and decrease in the TCP window size is based on the size of the first TCP data.

8. The WAN device of claim 6, wherein said software further causes said processor to:

forward a SYN to the WAN in response to receiving the SYN from the source;

forward a received SYN/ACK to the source in response to receiving the SYN/ACK from the WAN; and

forward an ACK to the WAN in response to receiving the ACK from the source,

wherein said operations develop the TCP connection of the first TCP data.

9. The WAN device of claim 8, wherein said software further causes said processor to:

increase the TCP window size to the source in conjunction with forwarding the second TCP data to the WAN in response to receiving the second TCP data from the source prior to receiving an ACK to the first TCP data; and

forward the ACK to the second TCP data from the WAN to the source in conjunction with decreasing the TCP window size to the source in response to receiving the ACK to the second TCP data from the WAN.

10. The WAN device of claim 9, wherein the increases and decreases in the TCP window size are based on the sizes of the first and second TCP data.