Power and data redundancy in a single wiring closet

• US 7,849,351 B2
• Filed: 11/30/2004
• Issued: 12/07/2010
• Est. Priority Date: 10/07/2004
• Status: Active Grant

• Current Assignee: Cisco Technology, Inc. (Cisco Systems, Inc.)
• Original Assignee: Cisco Technology, Inc. (Cisco Systems, Inc.)
• Inventors: Cafiero, Luca, Karam, Roger A.
• Primary Examiner(s): Wilson; Yolanda L
• Application Number:
  US11/000,734
• Publication Number:
  US 20060078093A1
• Time in Patent Office: 2,198 Days
• Field of Search: 716/4, 377/98, 709/224
• US Class Current: 714/4.1
• CPC Class Codes: H04L 1/22 using redundant apparatus to increase reliability
• CPC Class Codes: H04L 12/10 Current supply arrangements
• CPC Class Codes: H04L 41/0604 using filtering, e.g. reduction of information by using priority, element types, position or time

Abstract

Redundancy of data and/or Inline Power in a wired data telecommunications network from a first network device and a second network device configured as power sourcing equipment (PSE) devices and coupled together and to a third network device (such as a PD) via a Y device is provided by providing redundant signaling to/from each of the pair of network devices, and coupling a port of each of the network devices to the Y device and from there to a third port where a third network device such as a PD may be coupled. Because the Y device is essentially passive, communications paths between the PSE devices and the PD are provided for negotiating master/slave status and other status and related information among the respective network devices. Dynamic impedance matching is provided to handle situations where not all devices are plugged in and as a communications technique among the devices.

Claims

1. A method for providing redundancy from a first network device and a second network device through a Y device having a first, second and third port in a wired data telecommunications network having at least two pairs of twisted pair conductors, the Y device configured so that at least two pairs of twisted-pair conductors are connected at each of its first, second and third ports so that first, second and third connectors correspondingly associated with said first, second and third ports have connection contacts connected so that a first connection contact of each of said first, second and third connectors are all connected together, a second connection contact of each of said first, second and third connectors are all connected together, a third connection contact of each of said first, second and third connectors are all connected together, and a fourth connection contact of each of said first, second and third connectors are all connected together, the method comprising:

coupling the first network device configured as power sourcing equipment (PSE) to the first port of the Y device;

coupling the second network device configured as PSE to the second port of the Y device;

coupling a third network device configured as a powered device (PD) to the third port of the Y device;

dynamically adjusting a termination impedance associated with at least one of a wired data telecommunications network termination of the first network device and a wired data telecommunications network termination of the second network device; and

in response to dynamically adjusting the termination impedance associated with the at least one of a wired data telecommunications network termination of the first network device and a wired data telecommunications network termination of the second network device, causing an impedance experienced by the third network device across the wired data telecommunications network and into the Y device to be equal to a characteristic impedance value.

2. The method of claim 1, further comprising:

providing inline power from the first network device to the third network device while the first network device is fully operable.

3. The method of claim 2, further comprising:

providing inline power from the second network device to the third network device when the first network device is not fully operable in at least some respect.

4. The method of claim 1, further comprising:

communicating information between the first network device and the second network device over the wired data telecommunications network.

5. The method of claim 1, wherein:

said communicating utilizes common mode signaling between the first network device and the second network device.

6. The method of claim 1, wherein:

said communicating utilizes impedance modulation signaling between the first network device and the second network device.

7. The method of claim 1, further comprising:

utilizing the dynamically adjusted termination impedance of the first network device to discover that the Y device is coupled to the first network device.

8. The method of claim 1, further comprising:

sending a first test packet from the second network device to the first network device over the wired data telecommunications network;

receiving the first test packet at the first network device and, in response, sending a second test packet from the first network device to the third network device;

receiving the second test packet at the third network device and, in response, sending a third test packet from the third network device to the first network device; and

monitoring the transmission of the third test packet at the second network device.

9. The method of claim 8, further comprising:

configuring the first network device as a master and the second network device as a slave prior to sending the first test packet.

10. The method of claim 1, further comprising:

communicating information between the first network device and the second network device over a single pair of conductors of the wired data telecommunications network.

11. The method of claim 10, further comprising:

utilizing a single pair identity network to facilitate said communicating.

12. The method of claim 1, further comprising:

communicating information between the first network device and the third network device over a single pair of conductors of the wired data telecommunications network.

13. The method of claim 12, further comprising:

utilizing a single pair identity network to facilitate said communicating.

14. The method of claim 1, further comprising:

sending a communication from the first network device to the second network device, the communication telling the second network device to keep its link up for a period of time regardless of whether data packets are present on the wired data telecommunications network.

15. The method of claim 14, wherein

the communication comprises one of a flag pulse or a packet.

16. The method of claim 1, further comprising:

sending a communication from the first network device to the second network device, the communication telling the second network device to not utilize all four pairs of the wired data telecommunications network for communication for a period of time.

17. The method of claim 16, wherein the period of time ends upon receipt of another communication telling the second network device that it is permitted to use all four pairs for communication.

18. The method of claim 16, wherein

the communication comprises one of a flag pulse or a packet.

19. The method of claim 1, further comprising:

sending a communication from the first network device to the third network device, the communication telling the third network device to keep its link up for a period of time regardless of whether data packets are present on the wired data telecommunications network.

20. The method of claim 19, wherein

the communication comprises one of a flag pulse or a packet.

21. The method of claim 1, further comprising:

sending a communication from the first network device to the third network device, the communication telling the third network device to not utilize all four pairs of the wired data telecommunications network for communication for a period of time.

22. The method of claim 21, wherein the communication comprises one of a flag pulse or a packet.

23. The method of claim 21, wherein the period of time ends upon receipt of another communication telling the third network device that it is permitted to use all four pairs for communication.

24. The method of claim 1, further comprising:

detecting the Y device at one of the first, second and third network devices in response to signals transmitted from that network device onto the wired data telecommunications network; and

causing at least one other device coupled to the wired data telecommunications network to initiate a link integrity check in response to said detecting.

25. The method of claim 1, further comprising:

detecting the second network device at the first network device and, in response, conducting a master-slave negotiation between the first network device and the second network device to select one of the first and second network devices to be master (original master) and the other to be slave.

26. The method of claim 25, wherein:

the master-slave negotiation takes place, at least in part, using pulses over the wired data telecommunications network that are not in the form or Internet Protocol packets.

27. The method of claim 26, further comprising:

monitoring the wired data telecommunications network with the slave; and

detecting a fault in another network device.

28. The method of claim 27, further comprising:

having the slave take over as master in response to said detecting.

29. The method of claim 27, further comprising:

shutting off power to circuitry in the original master in response to said detecting.

30. The method of claim 25, further comprising:

detecting the decoupling of the slave from the Y device; and

responsive to said detecting the decoupling, initiating a link integrity test at the master.

31. The method of claim 25, further comprising:

initiating a communication at the third network device which can be monitored by the slave, the communication requesting the slave to conduct a conversation with the third network device.

32. The method of claim 31, further comprising:

having the master back off for at least a period of time in response to the communication.

33. The method of claim 32, wherein:

the master stops backing off when it detects the end of the conversation.

34. The method of claim 31, further comprising:

sending a communication from the slave to the master in response to the conversation, the communication requesting the master to become a slave.

35. The method of claim 1, further comprising:

detecting the decoupling of the third network device from the Y device;

shutting down inline power provided from the first network device and the second network device in response to said detecting.

36. The method of claim 35, wherein:

said detecting includes using a TDR at the first network device to detect the decoupling.

37. The method of claim 36, wherein:

said detecting further includes communicating with the second network device, said communication causing it to shut down inline power provided from the second network device.

38. The method of claim 1, further comprising:

detecting a zero inline power current draw from the third network device at the first network device;

communicating the detection of zero current draw from the first network device to the second network device;

detecting a zero inline current draw from the third network device at the second network device;

communicating the detection of zero current draw from the second network device to the first network device; and

shutting down inline power provided from the first network device and the second network device in response to at least said detecting and communicating.

39. The method of claim 1, further comprising:

tuning the dynamically adjusted termination impedance to reduce ISI (inter symbol interference) received at one of the network devices.

40. The method of claim 1, further comprising:

signaling from the third network device to the first network device and the second network device a requirement that redundancy is required for at least a period of time.

41. The method of claim 1, further comprising:

providing a different single pair identity network across each pair of conductors of the Y device.

42. The method of claim 41, further comprising:

providing another single pair identity network on each pair of conductors coupled to the third network device.

43. The method of claim 1, further comprising:

detecting the presence of the Y device with the first network device.

44. The method of claim 43, wherein said detecting detects the Y device by sensing a single-pair identity network associated with a pair of the Y device.

45. The method of claim 43, wherein said detecting detects the Y device by sensing an impedance signature of the Y device.

46. The method of claim 1, further comprising:

securing the connection between the Y device and at least the coupled first and second network devices, said securing comprising at least one of;

(1) verifying the total cable length between the first network device and the second network device;

(2) providing a password-based security to verify that both the first network device and the second network device are permitted to be coupled together; and

(3) performing a link integrity test from each of the first network device and the second network device.

47. The method of claim 1, further comprising:

having one of the first network device and the second network device conduct a first link integrity test; and

having the other of the first network device and the second network device conduct a second link integrity test after completion of the first link integrity test.

48. The method of claim 47, further comprising:

selecting one of the first network device and the second network device to be a master network device; and

selecting the other of the first network device and the second network device to be a slave network device.

49. The method of claim 48, wherein said selecting one is based upon relative available inline power resources of the first network device and the second network device.

50. The method of claim 48, wherein said selecting one is based upon manual input of a user.

51. The method of claim 48, wherein said selecting one is based upon configured software/firmware.

52. The method of claim 1, further comprising:

implementing a back off algorithm at the first network device to not search for inline power via the connected Y device for a period of time selected by the back off algorithm.

53. The method of claim 52, further comprising:

detecting at the first network device, after the period of time selected by the back off algorithm, the presence of inline power via the connected Y device, the inline power being regular inline power, an inline power discovery signal, or an inline power classification signal.

54. The method of claim 53, wherein:

if said detecting detects inline power and if the detected inline power is an inline power discovery signal or an inline power classification signal, the first network device continues to back off, and if the detected inline power is regular inline power the first network conducts a communication with the second network device in order to negotiate the application of regular inline power from the first network device.

55. The method of claim 53, wherein:

if said detecting detects inline power and if the detected inline power is an inline power discovery signal or an inline power classification signal, the first network device monitors the conductors and waits until inline power is applied by the second network device and then conducts a communication with the second network device in order to negotiate the application of regular inline power from the first network device.

56. The method of claim 53, wherein:

if said detecting detects inline power and if the detected inline power is an inline power discovery signal or an inline power classification signal, the first network device monitors the conductors and waits until inline power is applied by the second network device and then initiates inline power discovery and classification on its own behalf.

57. The method of claim 1, further comprising:

detecting an event that eliminates redundancy between the third network device and the first and second network devices.

58. The method of claim 57, wherein the event includes a high bit error rate between the third network device and one or both of the first and second network devices.

59. The method of claim 57, wherein the event includes detecting a link down on one or both of the links between the third network device and the first and second network devices.

60. The method of claim 57, wherein the event includes detecting a system malfunction in one or more of the first, second and third network devices.

61. The method of claim 57, wherein the event includes detecting a drop in available inline power over one or both of the links between the third network device and the first and second network devices.

62. The method of claim 57, further comprising:

responding to said detecting by initiating a communication to a network control point, the communication describing the event.

63. The method of claim 57, further comprising:

responding to said detecting by initiating a communication to at least one of the first, second and third network devices, the communication describing the event.

64. The method of claim 63, further comprising:

taking at least one action to reconfigure at least one of the first, second and third network devices in response to said detecting.

65. The method of claim 1:

wherein the Y device includes four (4) pairs of conductors; and

wherein the two (2) of the four pairs of conductors are each shorted to the first, second, and third ports of the Y device.

66. The method of claim 65:

wherein a first pair of conductors of the four (4) pairs of conductors is short circuited to the first, second, and third ports of the Y device;

wherein a second pair of conductors of the four (4) pairs of conductors is short circuited to the first, second, and third ports of the Y device;

wherein a third pair of conductors of the four (4) pairs of conductors is a direct link between the first and second ports of the Y device and is isolated from the third port of the Y device; and

wherein a fourth pair of conductors of the four (4) pairs of conductors is a direct link between the first and second ports of the Y device and is isolated from the third port of the Y device.

67. The method of claim 65:

wherein a first pair of conductors of the four (4) pairs of conductors is short circuited to the first, second, and third ports of the Y device;

wherein a second pair of conductors of the four (4) pairs of conductors is short circuited to the first, second, and third ports of the Y device;

wherein a third pair of conductors of the four (4) pairs of conductors connects to the first and second ports of the Y device via a first winding of a first center tapped transformer and connects to the third port of the Y device via a second winding of the first center tapped transformer; and

wherein a fourth pair of conductors of the four (4) pairs of conductors connects to the first and second ports of the Y device via a first winding of a second center tapped transformer and connects to the third port of the Y device via a second winding of the second center tapped transformer.

68. The method of claim 65:

wherein a first pair of conductors of the four (4) pairs of conductors is short circuited to the first, second, and third ports of the Y device;

wherein a second pair of conductors of the four (4) pairs of conductors is short circuited to the first, second, and third ports of the Y device;

wherein a third pair of conductors of the four (4) pairs of conductors (i) connects to the first port of the Y device via a first winding of a primary side of a first center tapped transformer, (ii) connects to the second port of the Y device via a second winding of the primary side of the first center tapped transformer, and (iii) connects to the third port of the Y device via a third winding of a secondary side of the first center tapped transformer; and

wherein a fourth pair of conductors of the four (4) pairs of conductors (i) connects to the first port of the Y device via a first winding of a primary side of a second center tapped transformer, (ii) connects to the second port of the Y device via a second winding of the primary side of the second center tapped transformer, and (iii) connects to the third port of the Y device via a third winding of a secondary side of the second center tapped transformer.

69. The method of claim 65:

wherein a first pair of conductors of the four (4) pairs of conductors is short circuited to the first, second, and third ports of the Y device;

wherein a second pair of conductors of the four (4) pairs of conductors is short circuited to the first, second, and third ports of the Y device;

wherein a third pair of conductors of the four (4) pairs of conductors is a direct link between the first and second ports of the Y device and is isolated from the third port of the Y device; and

wherein a fourth pair of conductors of the four (4) pairs of conductors is (i) a direct link between the first and third ports of the Y device and is isolated from the second port of the Y device, and (ii) a direct link between the second and third ports of the Y device and is isolated from the first port of the Y device.

70. The method of claim 1, wherein the characteristic impedance value is associated with an impedance value of a cable coupling the third network device to the third port of the Y device.

71. Network equipment for providing redundancy in a wired data telecommunications network, the equipment comprising:

a first network device configured as PSE;

a second network device configured as PSE, the first and the second network device providing redundant signals;

a Y device having a first port coupled to the first network device, a second port coupled to the second network device and a third port for coupling to a third network device, the Y device including at least two pairs of twisted pair conductors coupled to each of its three ports; and

a dynamic termination impedance circuit associated with at least one of the first network device and the second network device, dynamic adjusting of a termination impedance associated with the dynamic termination impedance circuit of at least one of the first network device and the second network device configured to cause an impedance experienced by the third network device across the wired data telecommunications network and into the Y device to be equal to a characteristic impedance value.

72. The equipment of claim 71, further comprising:

circuitry for communicating information between the first network device and the second network device over the wired data telecommunications network.

73. The equipment of claim 71, wherein:

said communicating utilizes common mode signaling between the first network device and the second network device.

74. The equipment of claim 71, wherein:

said communicating utilizes impedance modulation signaling between the first network device and the second network device.

75. The equipment of claim 71, wherein:

the dynamic termination impedance circuit of the first network device is adapted to discover that the Y device is coupled to the first network device.

76. The equipment of claim 71, further comprising:

means for sending a first test, status or control packet from the second network device to the first network device over the wired data telecommunications network;

means for receiving the first test, status or control packet at the first network device;

means responsive to said means for receiving the first test packet for sending a second test packet from the first network device to the third network device;

means for receiving the second test packet at the third network device;

means responsive to said means for receiving the second test packet for sending a third test packet from the third network device to the first network device; and

means for monitoring the transmission of the third test packet at the second network device.

77. The equipment of claim 76, further comprising:

means for configuring the first network device as a master and the second network device as a slave prior to sending the first test packet.

78. The equipment of claim 71, further comprising:

means for communicating information between the first network device and the second network device over a single pair of conductors of the wired data telecommunications network.

79. The equipment of claim 71, further comprising:

means for communicating information between the first network device and the third network device over a single pair of conductors of the wired data telecommunications network.

80. The equipment of claim 78, further comprising:

means for utilizing a single pair identity network to facilitate said communicating.

81. The equipment of claim 79, further comprising:

means for utilizing a single pair identity network to facilitate said communicating.

82. The equipment of claim 71, further comprising:

means for sending a communication from the first network device to the second network device, the communication telling the second network device to keep its link up for a period of time regardless of whether data packets are present on the wired data telecommunications network.

83. The equipment of claim 82, wherein

the communication comprises one of a flag pulse or a packet.

84. The equipment of claim 71, further comprising:

means for sending a communication from the first network device to the second network device, the communication telling the second network device to not utilize all four pairs of the wired data telecommunications network for communication for a period of time.

85. The equipment of claim 84, wherein

the communication comprises one of a flag pulse or a packet.

86. The equipment of claim 84, wherein the period of time ends upon receipt of another communication telling the second network device that it is permitted to use all four pairs for communication.

87. The equipment of claim 71, further comprising:

means for sending a communication from the first network device to the third network device, the communication telling the third network device to keep its link up for a period of time regardless of whether data packets are present on the wired data telecommunications network.

88. The equipment of claim 71, further comprising:

means for sending a communication from the first network device to the third network device, the communication telling the third network device to not utilize all four pairs of the wired data telecommunications network for communication for a period of time.

89. The equipment of claim 88, wherein

the communication comprises one of a flag pulse or a packet.

90. The equipment of claim 88, wherein the period of time ends upon receipt of another communication telling the third network device that it is permitted to use all four pairs for communication.

91. The equipment of claim 71, further comprising:

means for detecting the Y device at one of the first, second and third network devices in response to signals transmitted from the that network device onto the wired data telecommunications network; and

means responsive to said means for detecting for causing at least one other device coupled to the wired data telecommunications network to initiate a link integrity check.

92. The equipment of claim 71, further comprising:

means for detecting the second network device at the first network device and, in response, conducting a master-slave negotiation between the first network device and the second network device to select one of the first and second network devices to be master (original master) and the other to be slave.

93. The equipment of claim 92, further comprising:

means for detecting the decoupling of the slave from the Y device; and

means responsive to said means for detecting the decoupling, for initiating a link integrity test at the master.

94. The equipment of claim 71, further comprising:

means for initiating a communication at the third network device which can be monitored by the slave, the communication requesting the slave to conduct a conversation with the third network device.

95. The equipment of claim 94, further comprising:

means for sending a communication from the slave to the master in response to the conversation, the communication requesting the master to become a slave.

96. The equipment of claim 71, further comprising:

means for tuning the dynamic termination impedance to reduce ISI (inter symbol interference) received at one of the network devices.

97. The equipment of claim 71, further comprising:

means for signaling from the third network device to the first network device and the second network device a requirement that redundancy is required for at least a period of time.

98. The equipment of claim 71, further comprising:

means for providing a different single pair identity network across each pair of conductors of the Y device.

99. The equipment of claim 71:

wherein the Y device includes four (4) pairs of conductors; and

wherein the two (2) of the four pairs of conductors are each shorted to the first, second, and third ports of the Y device.

100. The equipment of claim 99:

wherein a first pair of conductors of the four (4) pairs of conductors is short circuited to the first, second, and third ports of the Y device;

wherein a second pair of conductors of the four (4) pairs of conductors is short circuited to the first, second, and third ports of the Y device;

wherein a third pair of conductors of the four (4) pairs of conductors is a direct link between the first and second ports of the Y device and is isolated from the third port of the Y device; and

wherein a fourth pair of conductors of the four (4) pairs of conductors is a direct link between the first and second ports of the Y device and is isolated from the third port of the Y device.

101. The equipment of claim 99:

wherein a first pair of conductors of the four (4) pairs of conductors is short circuited to the first, second, and third ports of the Y device;

wherein a second pair of conductors of the four (4) pairs of conductors is short circuited to the first, second, and third ports of the Y device;

wherein a third pair of conductors of the four (4) pairs of conductors connects to the first and second ports of the Y device via a first winding of a first center tapped transformer and connects to the third port of the Y device via a second winding of the first center tapped transformer; and

wherein a fourth pair of conductors of the four (4) pairs of conductors connects to the first and second ports of the Y device via a first winding of a second center tapped transformer and connects to the third port of the Y device via a second winding of the second center tapped transformer.

102. The equipment of claim 99:

wherein a first pair of conductors of the four (4) pairs of conductors is short circuited to the first, second, and third ports of the Y device;

wherein a second pair of conductors of the four (4) pairs of conductors is short circuited to the first, second, and third ports of the Y device;

wherein a third pair of conductors of the four (4) pairs of conductors (i) connects to the first port of the Y device via a first winding of a primary side of a first center tapped transformer, (ii) connects to the second port of the Y device via a second winding of the primary side of the first center tapped transformer, and (iii) connects to the third port of the Y device via a third winding of a secondary side of the first center tapped transformer; and

wherein a fourth pair of conductors of the four (4) pairs of conductors (i) connects to the first port of the Y device via a first winding of a primary side of a second center tapped transformer, (ii) connects to the second port of the Y device via a second winding of the primary side of the second center tapped transformer, and (iii) connects to the third port of the Y device via a third winding of a secondary side of the second center tapped transformer.

103. The equipment of claim 99:

wherein a first pair of conductors of the four (4) pairs of conductors is short circuited to the first, second, and third ports of the Y device;

wherein a second pair of conductors of the four (4) pairs of conductors is short circuited to the first, second, and third ports of the Y device;

wherein a third pair of conductors of the four (4) pairs of conductors is a direct link between the first and second ports of the Y device and is isolated from the third port of the Y device; and

wherein a fourth pair of conductors of the four (4) pairs of conductors is (i) a direct link between the first and third ports of the Y device and is isolated from the second port of the Y device, and (ii) a direct link between the second and third ports of the Y device and is isolated from the first port of the Y device.

104. The equipment of claim 71, wherein the characteristic impedance value is associated with an impedance value of a cable coupling the third network device to the third port of the Y device.