Determining a state of a network device

1. A processor for determining a state of a first network device in a lighting network, the processor being adapted to:

ascertain a first count value associated with the first network device and a second count value associated with a second network device adapted to pass messages to the first network device;

determine the state of the first network device based on the first count value and the second count value, wherein if the first count value is within a first predetermined range relative to the second count value, the processor determines that the first network device has been inactive,

wherein the first count value is dependent on a change of an incremental property of the first network device since a last reset of the first count value and the second count value is dependent on a change of an incremental property of the second network device since a last reset of the second count value.

2. The processor of claim 1 , wherein:

the first count value is representative of a number of messages or amount of data received by the first network device from the second network device since the last reset of the first count value; and

the second count value is representative of a number of messages or amount of data transmitted by the second network device for the first network device since the last reset of the second count value.

3. The processor of claim 2 , wherein:

if the first count value is within a second predetermined range relative to the second count value, the first network device is determined to be unreachable because it is out of range of the network; and

if the first count value is within a third predetermined range, the first network device is determined to be reachable.

4. The processor of claim 1 , wherein:

the first count value is representative of a time elapsed since the last reset of the first count value; and

the second count value is representative of a time elapsed since the last reset of the second count value.

5. The processor of claim 4 further adapted to:

ascertain a difference value based on a first calculated difference between the second count value measured in response to the second network device transmitting a first message to the first network device and the first count value measured in response to the first network device receiving the first message; and

determine the state of the first network device based on the difference value.

6. The processor of claim 5 further adapted to ascertain a second calculated difference between the second count value measured in response to the second network device transmitting a second, later message to the first network device and the first count value measured in response to the first network device receiving the second message,

wherein the difference value is a difference between the second calculated difference and the first calculated difference.

7. The processor of claim 5 , wherein:

if the difference value is greater than a first predetermined value, the first network device is determined to be a cause of network performance degradation;

if the difference value is less than a second predetermined value, the first network device is determined to be at least partially unable to communicate with the second network device; and

if the difference value is less than or equal to the first predetermined value and greater than or equal to the second predetermined value, the first network device is determined to be operating correctly.

8. The processor of claim 7 , wherein both the first predetermined value and the second predetermined value is zero.

9. A first network device adapted to determine its own state, the first network device comprising a processor according to claim 1 .

10. A network bridge comprising a processor according to claim 1 , wherein the network bridge:

plays the role of the second network device adapted to pass messages to the first network device; and

is adapted to receive the at least the first count value from the first network device.

11. A computer implemented method of determining a state of a first network device in a lighting network, the computer-implemented method comprising:

ascertaining a first count value associated with the first network device and a second count value associated with a second network device adapted to pass messages to the first network device;

determining the state of the first network device based on the first count value and the second count value, wherein if the first count value is within a first predetermined range relative to the second count value, the processor determines that the first network device has been inactive,

wherein the first count value is dependent on a change of an incremental property of the first network device since a last reset of the first count value and the second count value is dependent on a change of an incremental property of the second network device since a last reset of the second count value.

12. The computer implemented method of claim 11 , wherein:

the first count value is representative of a number of messages or amount of data received by the first network device from the second network device since the last reset of the first count value;

the second count value is representative of a number of messages or amount of data transmitted by the second network device for the first network device since the last reset of the second count value;

if the first count value is within a second predetermined range relative to the second count value, the first network device is determined to be unreachable because it is out of range of the network; and

if the first count value is within a third predetermined range, the first network device is determined to be reachable.

13. The computer-implemented method of claim 11 , wherein:

the first count value is representative of a time elapsed since the last reset of the first count value; and

the second count value is representative of a time elapsed since the last reset of the second count value.

14. The computer-implemented method of claim 13 , further comprising:

ascertaining a first calculated difference between the second count value measured in response to the second network device transmitting a first message to the first network device and the first count value measured in response to the first network device receiving the first message;

ascertaining a second calculated difference between the second count value measured in response to the second network device transmitting a second, later message to the first network device and the first count value measured in response to the first network device receiving the second message;

calculating a difference value, the difference value being a difference between the second calculated difference and the first calculated difference; and

determining the state of the first network device based on the difference value.

15. The computer-implemented method of claim 14 , wherein:

if the difference value is greater than a first predetermined value, the first network device is determined to be a cause of network performance degradation;

if the difference value is less than a second predetermined value, the first network device is determined to be at least partially unable to communicate with the second network device; and

if the difference value is less than or equal to the first predetermined value and greater than or equal to the second predetermined value, the first network device is determined to be operating correctly.