Method to sustain TCP connection

• US 7,088,698 B1
• Filed: 03/30/2001
• Issued: 08/08/2006
• Est. Priority Date: 04/22/1997
• Status: Expired due to Term

• Current Assignee: Symbol Technologies, LLC (Zebra Technologies Corporation)
• Original Assignee: Symbol Technologies, Inc. (Zebra Technologies Corporation)
• Inventors: Harsch, Thomas B.
• Primary Examiner(s): Nguyen, Chau
• Assistant Examiner(s): Cho, Hong Sol
• Application Number:
  US09/822,104
• Time in Patent Office: 1,957 Days
• Field of Search: 370/328, 370/331, 370/913, 370/338, 370/401, 455/436, 455/422, 455/458, 709/203, 709/228, 709/227
• US Class Current: 370/338
• CPC Class Codes: H04L 69/16 Implementation or adaptation of Internet protocol [IP], of transmission control protocol [TCP] or of user datagram protocol [UDP]
• CPC Class Codes: H04L 69/163 In-band adaptation of TCP data exchange; In-band control procedures
• CPC Class Codes: H04W 52/0241 where no transmission is received, e.g. out of range of the transmitter
• CPC Class Codes: H04W 76/25 Maintenance of established connections
• CPC Class Codes: H04W 84/12 WLAN [Wireless Local Area Networks]
• CPC Class Codes: Y02D 30/00 Reducing energy consumption in communication networks
• CPC Class Codes: Y02D 30/70 in wireless communication networks

Abstract

The present invention relates to network communication systems for managing client/server connections in a wireless environment. In accordance with the invention, a mobile communication unit (i.e., client), deploys keepalive packets at selected times in order to reset a keepidle timer of a server (e.g., host computer). By periodically resetting the keepidle timer a current connection between the mobile communication unit and server can be maintained as long as desired even when the mobile communication unit is in a power suspend mode. When in a power suspend mode, the mobile communication unit can briefly awake long enough to activate its transmitter and send a keepalive packet to the server to maintain the current connection. In this manner, the mobile communication unit can obtain the power savings of being in primarily a power suspend mode, but still prevent the current connection from timing out.

Claims

1. A network device for use in a communication system, the network device having a predetermined period of time during which, if no communication is received from a mobile communication unit, the network device ends an established connection with the mobile communication unit, the network device comprising:

a processor operative to control the network device;

a transceiver coupled to the processor, the transceiver operative to transmit and receive information between the mobile communication unit and the network device upon a connection being established between the mobile communication unit and the network device; and

the processor of the network device periodically receives an unsolicited transparent keepalive packet from the mobile communication unit at predetermined intervals, the keepalive packet serving to reset the predetermined period of time such that the network device does not end the established connection.

2. The network device of claim 1, the predetermined period of time being determined by a keepidle timer.

3. The network device of claim 2, the network device sending a keepalive probe upon expiration of the keepidle timer and ending the connection if a response is not received by the mobile communication unit in a predetermined response period, the keepalive packet acts as a response resetting at least one of the keepidle timer and the predetermined response period.

4. The network device of claim 1, the predetermined period of time comprising the time it takes for a keepidle timer to expire, a keep alive probe to be sent upon expiration of the keepidle timer and a predetermined response time for the mobile communication unit to respond to the keep alive probe to expire.

5. The network device of claim 1, the keepalive packet transmitted from the mobile communication unit to the network device serves solely to reset the predetermined period of time so that the network device does not end the connection.

6. The network device of claim 1, the network device periodically receives the keepalive packet from the mobile communication unit in time intervals which are less then the predetermined time set by the network device.

7. The network device of claim 1, the mobile communication unit and the network device communicate using a TCP protocol.

8. The network device of claim 1, the network device being a host computer.

9. A a communication system that propagates a keepalive packet, the keepalive packet serving to reset a predetermined period of time that a network device ends a connection with a mobile communication unit, the system comprising:

a network device with a connection to a mobile communication unit, the network device at least one of receives and sends a keepalive packet, the keepalive packet comprising;

a preamble field having synchronizing bits for allowing the network device to synchronize to the packet;

a header field following the preamble field;

a source address field holding the address of the mobile communication unit from which the packet originates;

a destination field holding the address of the network device for which the packet is directed;

a sending sequence field relating to the number of bytes of the packet, the sending sequence field comprising a number one less than a sending sequence number expected by the network device;

a last sequence field provided to allow the network device to determine the last sequence number sent by the network device to the mobile communication unit; and

error correction field provided to allow the network device to determine if it has properly received the packet.

10. The keepalive packet of claim 9, the header field containing information of at least one of packet length, packet type and temporary identification of the mobile communication unit.

11. The keepalive packet of claim 9, further comprising a number representative of a random starting number chosen by the mobile communication unit plus the number of bytes of data inside the packet.

12. The keepalive packet of claim 9, the sending sequence field comprising a number one less than a sending sequence number expected by the network device causes the network device to immediately return an acknowledgment packet to the mobile communication unit.

13. The keepalive packet of claim 9, the sending sequence field comprising a number one less than a sending sequence number expected by the network device causes the network device to not advance the sequence number of the network device, such that the synchronization state between the mobile communication unit and the network device is not changed.

14. The keepalive packet of claim 9, the sending sequence field comprising a number equal to the last number stored in a stack of the mobile communication unit plus the number of bytes of the packet.

15. The network device of claim 9, the packet is transmitted using a TCP protocol.

16. A method for maintaining a connection between a network device and a mobile communication unit, comprising:

ending the connection by the network device if no communication is received from the mobile communication unit for a predetermined period of time; and

transmitting an unsolicited keepalive packet from the mobile communication unit to the network device, the keepalive packet serving to reset the predetermined period of time so that the network device does not end the connection and is transparent to the network device.

17. A mobile communication unit for use in a communication system, the communication system including a network device, the network device having a predetermined period of time during which, if no communication is received from the mobile communication unit, the network device ends an established connection with the mobile communication unit, the mobile communication unit comprising:

a processor operative to control the mobile communication unit;

a transmitter coupled to the processor, the transmitter operative to transmit information to the network device upon a connection being established between the mobile communication unit and the network device; and

the processor of the mobile communication unit transmits a transparent, unsolicited keepalive packet to the network device, the keepalive packet serving to reset the predetermined period of time so that the network device does not end the established connection.

18. A communication system comprising:

a mobile client;

a network device adapted to determine if no communication from the mobile client is received for a predetermined period of time during a connection and ending the connection with the mobile client if the predetermined period of time expires prior to the network device receiving communication from the mobile client; and

the mobile client transmits an unsolicited keepalive packet to the network device, the keepalive packet serving to reset the predetermined period of time so that the network device does not end the communication, the keepalive packet transparent to the network device.