Lossless connection failover for single devices

• US 9,118,594 B2
• Filed: 11/15/2012
• Issued: 08/25/2015
• Est. Priority Date: 12/06/2011
• Status: Expired due to Fees

• Current Assignee: Avago Technologies International Sales Pte Limited (Broadcom, Inc.)
• Original Assignee: Brocade Communications Systems, Inc. (Broadcom, Inc.)
• Inventors: Hegland, Ryan, Sabaa, Amr, Adiraju, Siva
• Primary Examiner(s): Lai, Andrew
• Assistant Examiner(s): HENSON, JAMAAL R
• Application Number:
  US13/677,929
• Publication Number:
  US 20130315253A1
• Time in Patent Office: 1,013 Days
• Field of Search: 370/326, 370/400, 370/389, 709/203
• US Class Current: 1/1
• 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 transmission control protocol (TCP) data at a wide area network (WAN) device from a source device;

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

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

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

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 device;

forwarding the SYN to the destination device of the WAN by the WAN device;

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

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

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

forwarding the ACK to the destination device of 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 device prior to receiving an ACK to the first TCP data;

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

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

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

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 to a WAN and to a source device of transmission control protocol (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 device in conjunction with forwarding first TCP data to the destination device of the WAN in response to receiving the first TCP data from the source device; and

forward an ACK to the first TCP data from the destination device of the WAN to the source device in conjunction with decreasing the TCP window size to the source device in response to receiving the ACK to the first TCP data from the destination device of 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 destination device of the WAN in response to receiving the SYN from the source device;

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

forward an ACK to the destination device of the WAN in response to receiving the ACK from the source device, 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 device in conjunction with forwarding the second TCP data to the destination device of the WAN in response to receiving the second TCP data from the source device prior to receiving an ACK to the first TCP data; and

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