Methods and systems of preserving client overhead bytes in optical transport network tunneling applications

1. A method of tunneling in an Optical Transport Network (OTN), comprising:

receiving a working signal and a protection signal, wherein the working signal has a working payload and working overhead bytes with working Automatic Protection Switching (APS) switching coordination bytes, the protection signal has a protection payload and protection overhead bytes with protection APS switching coordination bytes, and the working signal or the protection signal is designated as an active signal with an active payload and active overhead bytes;

generating an Optical channel Data Unit (ODU) signal with an ODU signal payload and an overhead segment, wherein the ODU signal payload is the active payload, and the overhead segment has portions of the working overhead bytes and the protection overhead bytes including the working APS switching coordination bytes and the protection APS switching coordination bytes;

transmitting the ODU signal into an Optical Transport Network (OTN) network, wherein the ODU signal is a single signal transported over the OTN network;

receiving the ODU signal from the OTN network;

recreating the working signal based on the active payload in the ODU signal payload and the working overhead bytes in the overhead segment;

recreating the protection signal based on the active payload in the ODU signal payload and the protection overhead bytes in the overhead segment; and

transmitting the recreated working signal and the recreated protection signal.

2. A method according to claim 1 , wherein the working signal and the protection signal are compliant with one of Synchronous Optical Networking (SONET) and Synchronous Digital Hierarchy (SDH).

3. A method according to claim 1 , wherein the working APS switching coordination bytes and the protection APS switching coordination bytes are placed in unused or reserved bytes in the ODU signal overhead segment.

4. A method according to claim 1 , wherein:

the working APS switching coordination bytes comprise K-bytes; and

the protection APS switching coordination comprise K-bytes.

5. A method according to claim 1 , wherein:

the working overhead bytes comprise working APS K bytes;

the protection overhead bytes comprise protection APS K bytes; and

the ODU signal overhead segment comprises the working APS K bytes and the protection APS K bytes.

6. A method according to claim 5 , wherein transmitting the recreated working signal and the recreated protection signal comprises transmitting the working APS K bytes on a working line and transmitting the protection APS K bytes on a protection line.

7. A method according to claim 1 , wherein the steps of receiving a working signal and a protection signal and transmitting the recreated working signal and the recreated protection signal carry APS switching coordination bytes according to an APS 1+1 protocol.

8. A method according to claim 1 , further comprising performing APS, Virtual Line Switching Ring, or Bidirectional Line Switching Ring protection between the working signal and the protection signal through maintaining the APS switching coordination bytes on the single signal in the OTN network.

9. A method according to claim 1 , further comprising:

responsive to a failure on the ODU signal, starting a hold off timer;

sending APS switching-coordination bytes from the active signal; and

at an expiration of the hold off timer and responsive to the OTN network not restoring the ODU signal, sending an alarm indication signal (AIS) on the active signal.

10. A network comprising:

a first node configured to:

receive a working signal and a protection signal each with Automatic Protection Switching (APS) switching coordination bytes;

recognize the working signal or the protection signal as an active signal;

encapsulate the active signal in an Optical channel Data Unit (ODU) signal;

insert the APS switching coordination bytes from the working signal in an overhead segment of the ODU signal;

insert the APS switching coordination bytes from the protection signal in an overhead segment of the ODU signal; and

transmit the ODU signal into an Optical Transport Network (OTN) network, and

a second node configured to:

receive the ODU signal from the OTN network;

recreate the working signal based on the active signal encapsulated in the ODU signal and the APS switching coordination bytes from the working signal inserted in the ODU signal;

recreate the protection signal based on the active signal encapsulated in the ODU signal and the APS switching coordination bytes from the protection signal inserted in the ODU signal;

transmit the recreated working signal and the recreated protection signal;

wherein the ODU signal comprises a single signal transmitted over the OTN network while maintaining both the active signal and the APS switching coordination bytes from the working signal and protection signal therein.

11. A network according to claim 10 , wherein the working signal and the protection signal are compliant with one of Synchronous Optical Networking (SONET) and Synchronous Digital Hierarchy (SDH).

12. A network according to claim 10 , wherein the first node is configured to insert APS switching-coordination bytes from the working signal and the protection signal into unused or reserved bytes in the overhead segment of the ODU signal.

13. A network according to claim 10 , wherein the working signal and the protection signal comprises receiving K-bytes on working and protection lines.

14. A network according to claim 10 , wherein the first and second nodes are together configured to carry the APS switching coordination bytes according to an APS 1+1 protocol.

15. A network according to claim 10 , wherein the first node is configured to transmit the ODU signal as a single signal; and

perform APS, Virtual Line Switching Ring, or Bidirectional Line Switching Ring protection between the working signal and the protection signal through maintaining the APS switching coordination bytes on the single signal in the OTN network.

16. A network according to claim 10 , wherein the second node is configured to, responsive to a failure on the ODU signal, start a hold off timer;

continue to send APS switching-coordination bytes from the active signal; and

at an expiration of the hold off timer and responsive to the ODU signal not being restored by the OTN network, send an alarm indication signal (AIS) on the active signal.

17. A node, with tunneling in Optical Transport Network (OTN), the node comprising:

one or more modules configured to:

receive a working signal and a protection signal, wherein the working signal comprises a working payload and working overhead bytes with working Automatic Protection Switching (APS) switching coordination bytes, the protection signal comprises a protection payload and protection overhead bytes with protection APS switching coordination bytes, and the working signal or the protection signal is designated as an active signal comprising an active payload and active overhead bytes;

generate an Optical channel Data Unit (ODU) signal comprising an ODU signal payload and an overhead segment, the ODU signal payload comprising the active payload, the overhead segment has portions of the working overhead bytes and the protection overhead bytes including the working APS switching coordination bytes and the protection APS switching coordination bytes; and

transmit the ODU signal into an Optical Transport Network (OTN) network, wherein the ODU signal comprises a single signal transported over the OTN network;

wherein the ODU signal is received at another node from the OTN network where the working signal is recreated based on the active payload in the ODU signal payload and the working overhead bytes in the overhead segment, the protection signal is recreated based on the active payload in the ODU signal payload and the protection overhead bytes in the overhead segment, and the recreated working signal and the recreated protection signal are transmitted from the another node.

18. A node according to claim 17 , wherein the working signal and the protection signal are compliant with one of Synchronous Optical Networking (SONET) and Synchronous Digital Hierarchy (SDH).

19. A node according to claim 17 , wherein the node is configured to insert APS switching-coordination bytes from the working signal and the protection signal into unused or reserved bytes in the overhead segment of the ODU signal.

20. A node according to claim 17 , wherein the working signal and the protection signal comprises receiving K-bytes on working and protection lines.

21. A node according to claim 17 , wherein the node and the another node are together configured to carry the APS switching coordination bytes according to an APS 1+1 protocol.