System and method for creating and using unique packet preambles for data communication

• US 7,277,441 B1
• Filed: 03/24/2003
• Issued: 10/02/2007
• Est. Priority Date: 03/24/2003
• Status: Expired due to Fees

• Current Assignee: Cisco Technology, Inc. (Cisco Systems, Inc.)
• Original Assignee: Cisco Technology, Inc. (Cisco Systems, Inc.)
• Inventors: Mukhopadhyay, Snigdhendu S., Rangarajan, Raja
• Primary Examiner(s): Pham; Chi
• Assistant Examiner(s): Chou; Albert T.
• Application Number:
  US10/396,931
• Time in Patent Office: 1,653 Days
• Field of Search: 370/395.3, 370/335, 370/352, 370/343, 370/447, 708/254, 455/456, 375/368
• US Class Current: 370/395.3
• CPC Class Codes: H04L 7/042 Detectors therefor, e.g. correlators, state machines digital correlators in general G06F17/15
• CPC Class Codes: H04M 11/062 using different frequency bands for speech and other data

Abstract

Data communication system is provided that comprises a plurality of switches which each comprise a respective controller. Ports on the switch are connected to any one of a multiplicity of far-end devices. Physical media is used to connect each port to a far-end device. Various physical media may be routed through a common binder which can create electromagnetic interference problems. Each port controller is operable to calculate a unique preamble value to be assigned to each port within the switch. The unique preamble value is calculated using a linear feedback shift register function which can be implemented using convenient matrix multiplication operations on seed values stored within the port controllers.

Claims

1. A method for communicating data comprising the steps of:

identifying a particular port within a head-end switch, the port operable to be coupled to a far-end communication device through physical media and to communicate data between the port and the far-end communication device using the physical media;

generating a unique preamble value to be used as a preamble associated with data packets to be sent from the identified port and to be received by the identified port, the unique preamble value calculated such that other ports within the switch other than the identified port will use different preamble values such that data communications erroneously received by a port that are intended for another port can be differentiated using the unique preamble values assigned to each port, generating the unique preamble value comprising;

calculating a preamble bit string using a linear feedback shift register function performed on a seed value and using a generator value, the linear feedback shift register function is performed by performing a matrix multiplication operation using a generator matrix associated with the generator value.

2. The method of claim 1 wherein the step of generating is performed by a port controller at the switch.

3. The method of claim 1 wherein the seed value is selected using a unique serial number associated with a particular head-end switch such that neighboring head-end switches can independently calculate preamble values and preamble values calculated by such neighboring switches will be unique as to all switches performing such calculations.

4. The method of claim 1 wherein the generator matrix comprises an original generator matrix and wherein the linear feedback shift register function is performed by performing a matrix multiplication of an offset generator matrix by an original seed value to yield an interval seed value where the offset generator matrix is a power of the original generator matrix.

5. The method of claim 4 wherein the interval seed value is multiplied by the original generator matrix at least once to yield a potential preamble value.

6. The method of claim 4 wherein the interval seed value is multiplied by a power of the original generator matrix to yield a next interval seed value associated with a next port.

7. A method for communicating data comprising:

identifying a particular port within a head-end switch, the port operable to be coupled to a far-end communication device through physical media and to communicate data between the port and the far-end communication device using the physical media;

storing a plurality of seed values and a plurality of generator matrices in a port controller associated with the head-end switch, the plurality of generator matrices each comprising a power of the original generator matrix such that the stored seed values and the stored generator matrices may be used by a switch to calculate preamble values for ports associated with that switch; and

generating a unique preamble value to be used as a preamble associated with data packets to be sent from the identified port and to be received by the identified port, the unique preamble value calculated such that other ports within the switch other than the identified port will use different preamble values such that data communications erroneously received by a port that are intended for another port can be differentiated using the unique preamble values assigned to each port, generating the unique preamble value comprising;

calculating a preamble bit string using a linear feedback shift register function performed on a seed value and using a generator value.

8. A method for communicating data comprising:

identifying a particular port within a head-end switch, the port operable to be coupled to a far-end communication device through physical media and to communicate data between the port and the far-end communication device using the physical media;

generating a unique preamble value to be used as a preamble associated with data packets to be sent from the identified port and to be received by the identified port, the unique preamble value calculated such that other ports within the switch other than the identified port will use different preamble values such that data communications erroneously received by a port that are intended for another port can be differentiated using the unique preamble values assigned to each port, generating the unique preamble value comprising;

calculating a preamble bit string using a linear feedback shift register function performed on a seed value and using a generator value; and

checking the preamble bit string against a set of preamble value criteria before using the preamble bit string as a preamble.

9. The method of claim 8 wherein the preamble value criteria comprise that the preamble must be 24 bits in length.

10. The method of claim 8 wherein the preamble value criteria comprise that the preamble must consist of twelve logical ones and twelve logical zeros.

11. The method of claim 8 wherein the preamble value criteria comprise that the preamble must have either twelve, thirteen, fourteen, or fifteen logical transitions.

12. A data communication switch, comprising:

a plurality of ports operable to identifying a particular port within a head-end switch, the port operable to be coupled to a far-end communication device through physical media and to communicate data between the port and the far-end communication device using the physical media;

a port controller coupled to and controlling at least some of the plurality of ports and operable to;

store a plurality of seed values and a plurality of generator matrices, the plurality of generator matrices each comprising a power of the original generator matrix such that the stored seed values and the stored generator matrices may be used by the port controller to calculate preamble values for ports associated with the port controller; and

generate a unique preamble value to be used as a preamble associated with data packets to be sent from the identified port and to be received by the identified port, the unique preamble value calculated such that other ports within the switch other than the identified port will use different preamble values such that data communications erroneously received by a port that are intended for another port can be differentiated using the unique preamble values assigned to each port.

13. The data communication switch of claim 12 and further comprising a memory for storing a serial number associated with the switch, the port controller operable to access the memory and retrieve at least a portion of the serial number.

14. The data communication switch of claim 12 wherein a seed value is selected using a unique serial number associated with a particular head-end switch such that neighboring head-end switches can independently calculate preamble values and preamble values calculated by such neighboring switches will be unique as to all switches performing such calculations.

15. A data communication switch, comprising:

a plurality of ports operable to identifying a particular port within a head-end switch, the port operable to be coupled to a far-end communication device through physical media and to communicate data between the port and the far-end communication device using the physical media;

a port controller coupled to and controlling at least some of the plurality of ports and operable to generate a unique preamble value to be used as a preamble associated with data packets to be sent from the identified port and to be received by the identified port, the unique preamble value calculated such that other ports within the switch other than the identified port will use different preamble values such that data communications erroneously received by a port that are intended for another port can be differentiated using the unique preamble values assigned to each port, the port controller operable to generate a unique preamble value by calculating a preamble bit string using a linear feedback shift register function performed on a seed value and using a generator value, the linear feedback shift register function performed by performing a matrix multiplication operation using a generator matrix associated with the generator value.

16. A system for communicating data, comprising:

means for identifying a particular port within a head-end switch, the port operable to be coupled to a far-end communication device through physical media and to communicate data between the port and the far-end communication device using the physical media;

means for generating a unique preamble value to be used as a preamble associated with data packets to be sent from the identified port and to be received by the identified port, the unique preamble value calculated such that other ports within the switch other than the identified port will use different preamble values such that data communications erroneously received by a port that are intended for another port can be differentiated using the unique preamble values assigned to each port, the means for generating a unique preamble value comprising;

a means for calculating a preamble bit string using a linear feedback shift register function performed on a seed value and using a generator value, the linear feedback shift register function performed by performing a matrix multiplication operation using a generator matrix associated with the generator value.

17. The system of claim 16 wherein the seed value is selected using a unique serial number associated with a particular head-end switch such that neighboring head-end switches can independently calculate preamble values and preamble values calculated by such neighboring switches will be unique as to all switches performing such calculations.

18. The system of claim 16 wherein the generator matrix comprises an original generator matrix and wherein the linear feedback shift register function is performed by performing a matrix multiplication of an offset generator matrix by an original seed value to yield an interval seed value where the offset generator matrix is a power of the original generator matrix.

19. The system of claim 16 and further comprising means for checking the preamble bit string against a set of preamble value criteria before using the preamble bit string as a preamble.

20. A system for communicating data, comprising:

means for identifying a particular port within a head-end switch, the port operable to be coupled to a far-end communication device through physical media and to communicate data between the port and the far-end communication device using the physical media;

a means for storing a plurality of seed values and a plurality of generator matrices in a port controller associated with a head-end switch, the plurality of generator matrices each comprising a power of the original generator matrix such that the stored seed values and the stored generator matrices may be used by a switch to calculate preamble values for ports associated with that switch; and

means for generating a unique preamble value to be used as a preamble associated with data packets to be sent from the identified port and to be received by the identified port, the unique preamble value calculated such that other ports within the switch other than the identified port will use different preamble values such that data communications erroneously received by a port that are intended for another port can be differentiated using the unique preamble values assigned to each port, the means for generating a unique preamble value comprising;

a means for calculating a preamble bit string using a linear feedback shift register function performed on a seed value and using a generator value.