Fault tolerant network utilizing bi-directional point-to-point communications links between nodes

• US 8,179,787 B2
• Filed: 01/27/2009
• Issued: 05/15/2012
• Est. Priority Date: 01/27/2009
• Status: Active Grant

• Current Assignee: Lutron Technology Company LLC
• Original Assignee: Smsc Holdings Sarl
• Inventors: Knapp, David J.
• Primary Examiner(s): Yao, Kwang B
• Assistant Examiner(s): Tran, Tung Q
• Application Number:
  US12/360,467
• Publication Number:
  US 20100188972A1
• Time in Patent Office: 1,204 Days
• Field of Search: 370216-228, 370242-258
• US Class Current: 370/222
• CPC Class Codes: H04L 12/43 with synchronous transmission, e.g. time division multiplex [TDM], slotted rings
• CPC Class Codes: H04L 12/437 Ring fault isolation or reconfiguration for SDH/SONET ring networks H04J3/085
• CPC Class Codes: H04L 2012/40273 the transportation system being a vehicle
• CPC Class Codes: H04L 45/28 using route fault recovery

Abstract

A data communication system and an associated network node implementation is disclosed that, in certain embodiments, uses single-channel bi-directional communication links between nodes to send frames of data. The network nodes can be connected together in a ring or daisy chain topology with data frames sent in alternating directions through the bi-directional links. Such networks initially configured in a physical ring topology can tolerate single point failures by automatically switching to a logical daisy chain topology.

Claims

1. A method for use in a network node within an interconnected network of nodes, said method comprising:

forwarding data frames received on a first bi-directional port of the network node to a second bi-directional port of the network node for outbound transmission on the second bi-directional port;

forwarding data frames received on the second bi-directional port to the first bi-directional port for outbound transmission on the first bi-directional port, wherein the first and second ports comprise single-channel bi-directional ports;

if a data frame received on a given bi-directional port includes a message addressed to the network node, then inserting a message status symbol into the next data frame transmitted outbound on the given bi-directional port; and

assigning an address for the network node in response to a received data frame which includes an address discovery command, wherein assigning comprises;

incrementing an address conveyed in the address discovery command data frame;

storing the incremented address as the network node address; and

forwarding the address discovery command with the incremented address in the next transmitted data frame.

2. The method as recited in claim 1, wherein the first and second ports each comprise an optical fiber port.

3. The method as recited in claim 1 further comprising synchronizing bit timing of data frames transmitted on one port to bit timing of data frames received on the other port.

4. The method as recited in claim 1 further comprising re-timing transmission of outbound data frames to an internal timing reference of the network node.

6. The method as recited in claim 1 wherein the message status symbol comprises an acknowledge symbol (ACK) if the message was received without errors by the network node, and comprises an error symbol (ERC) if the message was received by the network node but contained one or more errors.

16. The method as recited in claim 1 further comprising:

triggering a network topology reconfiguration after a certain period of inbound inactivity on a previously active port.

20. The method as recited in claim 1 wherein the network node is configured to operate as a timing master node, and wherein the method further comprises:

arbitrating with other devices which are likewise configurable to operate as a timing master node, to determine whether the network node will operate as the timing master node for the network if the other devices are not configured to operate as the timing master node.

21. The method as recited in claim 1 further comprising:

forwarding data frames received on a third bi-directional port of the network node to a fourth bi-directional port of the network node for outbound transmission on the fourth bi-directional port;

forwarding data frames received on the fourth bi-directional port to the third bi-directional port for outbound transmission on the third bi-directional port; and

if a data frame received on one of the first and second bi-directional ports addresses a network node reachable from the third or fourth ports, forwarding the data frame to said third or fourth port.

5. A method for use in a network node within an interconnected network of nodes, said method comprising:

forwarding data frames received on a first bi-directional port of the network node to a second bi-directional port of the network node for outbound transmission on the second bi-directional port;

forwarding data frames received on the second bi-directional port to the first bi-directional port for outbound transmission on the first bi-directional port, wherein the first and second ports comprise single-channel bi-directional ports; and

if a data frame received on a given bi-directional port includes a message addressed to the network node, then inserting a message status symbol into a forwarded data frame received on the other port of the network node, and transmitted outbound on the given bi-directional port.

7. The method as recited in claim 5 further comprising:

inserting, into a data frame received on one port, a new message for outbound transmission of the data frame including the new message on the other port.

8. The method as recited in claim 7 further comprising:

if the new message comprises a broadcast message, inserting the broadcast message into a second data frame received on the other port, for outbound transmission of the second data frame including the broadcast message on the one port.

9. The method as recited in claim 7 further comprising:

arbitrating the relative priority of the new message and any existing message carried by the data frame received on the one port; and

if the new message wins arbitration, inserting the new message into the data frame and preempting the existing message, for outbound transmission of the data frame including the new message on the other port.

10. The method as recited in claim 9 wherein:

the arbitrating is performed bit-serially, and a new priority indicator inserted as soon as the network node wins the arbitration.

11. The method as recited in claim 9 wherein:

if the new message is shorter than the preempted message, padding the new message to the length of the preempted message.

12. The method as recited in claim 9 wherein:

if the preempted message is a broadcast message, inserting a negative acknowledge (NOT ACK) message status symbol in next frame transmitted outbound on the port which received the data frame containing the preempted broadcast message.

13. The method as recited in claim 9 wherein:

if the new message loses arbitration and is not inserted into the data frame, queuing the new message for retransmission in a subsequent data frame and increasing the priority of the new message to increase likelihood of winning a subsequent arbitration.

14. The method as recited in claim 7 further comprising:

if the next data frame received on the other port includes an ACK symbol, removing the ACK symbol from said next data frame before forwarding to the one port; and

if the next data frame received on the other port does not include an ACK symbol, queuing the new message for retransmission in the next available data frame.

15. The method as recited in claim 7 further comprising:

maintaining a table of network node addresses reachable by a data frame transmitted on each respective port; and

sending a message to a destination node only in a data frame transmitted on the corresponding port.

17. The method as recited in claim 7 wherein each data frame comprises an arbitration field, an address field, a data field, a message status field, and a CRC checksum field.

18. The method as recited in claim 17 wherein each data frame further comprises:

a start sequence including a plurality of bit transitions for synchronizing an internal reference clock of the network node receiving the data frame.

19. The method as recited in claim 17 wherein the arbitration field conveys a priority value for indicating the priority of the message included within the data frame, and when such priority value is a predetermined value in its range, for indicating that the data frame is empty and thus does not include a message.