Methods and systems for carrying synchronization over Ethernet and optical transport network

• US 20080151941A1
• Filed: 12/26/2006
• Published: 06/26/2008
• Est. Priority Date: 12/26/2006
• Status: Active Grant

• Current Assignee: Ciena Corporation
• Original Assignee: Ciena Corporation
• Inventors: Ghodrat, Morteza, Duncan, Ian H., Gazier, Michael A.
• Granted Patent: US 8,059,685 B2
• Time in Patent Office: Days
• US Class Current: 370/503
• CPC Class Codes: H04J 2203/0085 Support of Ethernet
• CPC Class Codes: H04J 3/0658 Clock or time synchronisation among packet nodes
• CPC Class Codes: H04J 3/1658 carrying packets or ATM cells; H04J3/1664 takes precedence for payloads with different packet types
• CPC Class Codes: H04L 7/08 the synchronisation signals recurring cyclically

Abstract

The present invention reserves special Ethernet timing packets to mark timing within Ethernet and OTN, and secondarily creates frames within the Ethernet stream through the timing marker packets. The result is standard Ethernet with timing capability that can be transported over standard Ethernet links and/or within OTN. This timing capability can be utilized to carry synchronization over asynchronous Ethernet and OTN streams. Advantageously, enabling Ethernet and OTN to carry synchronous information will de-risk switching from SONET/SDH to Ethernet and/or OTN for service providers. The present invention also includes frame decomposition of the Ethernet stream. Ethernet packets are broken into fixed bandwidth and excess bandwidth. The fixed bandwidth is subdivided into fixed (negotiated) flits, with each flit corresponding to a specific user or combination of users like a private tunnel. This offers service providers a method to provide deterministic and more secure bandwidth over Ethernet to multiple clients.

Claims

1. A method for carrying synchronization over Ethernet, the method comprising the steps of:

receiving a clock source;

inserting a timing marker into an Ethernet stream responsive to an input from the clock source;

transmitting the Ethernet stream; and

repeating the receiving, inserting, and transmitting steps.

2. The method of claim 1, further comprising the steps of:

receiving the Ethernet stream;

extracting the timing marker from the Ethernet stream;

establishing a timing reference signal responsive to the frequency between timing markers; and

repeating the receiving, extracting, and establishing steps.

3. The method of claim 2, wherein the method is performed by any of an Ethernet switch, a multi-service switch, a computer, a router, and an Optical Transport Network switch.

4. The method of claim 2, wherein the inserting and extracting steps are done as the highest priority.

5. The method of claim 1, wherein the clock source is configured to give an input at 8 kHz.

6. The method of claim 1, wherein the clock source is configured to give an input at a user-defined frequency.

7. The method of claim 2, wherein the timing markers, a specific number of bytes per frame, or a specific character or sequence provide a decomposition of the Ethernet stream into frames comprising a fixed bandwidth and an excess bandwidth.

8. The method of claim 7, wherein the fixed bandwidth is subdivided into fixed (negotiated) flits, wherein the fixed (negotiated) flits each correspond to an end user.

9. The method of claim 8, wherein the excess bandwidth is dynamically allocated to individual flits on an as-needed basis.

10. The method of claim 8, wherein the excess bandwidth is allocated using the dynamic bandwidth allocation method.

11. The method of claim 2, wherein the timing marker is carried out-of-band marked with a special 8 b/10 b symbol.

12. The method of claim 2, wherein the Ethernet stream is carried over Optical Transport Network.

13. A method for carrying synchronization over Optical Transport Network, the method comprising the steps of:

receiving a clock source;

inserting a timing marker into the header of an Optical Transport Network frame responsive to an input from the clock source;

transmitting Optical Transport Network frame; and

repeating the receiving, inserting, and transmitting steps.

14. The method of claim 13, further comprising the steps of:

receiving the Optical Transport Network frame;

extracting the timing marker from the Optical Transport Network frame;

establishing a timing reference signal responsive to the frequency between timing markers; and

repeating the receiving, extracting, and establishing steps.

15. The method of claim 14, wherein the clock source is configured to give an input at 8 kHz.

16. The method of claim 14, wherein the clock source is configured to give an input at a user-defined frequency.

17. A network element capable of synchronization, comprising:

a clock source;

a plurality of inter-node links each connected to either a de-multiplexer or a multiplexer, wherein the de-multiplexer is configured to de-multiplex packets from each of the plurality of inter-node links, and the multiplexer is configured to multiplex packets to each of the plurality of inter-node links;

one or more buffer/queues configured to receive, store, and send packets to the de-multiplexer/multiplexer;

timing marker packets sent to one of the one or more buffer/queues responsive to an input from the clock source, and the timing marker packet is inserted by the multiplexer at the highest priority; and

a timing reference signal derived from the frequency between extracted timing marker packets, wherein the extracted timing marker packets are extracted from the de-multiplexer at the highest priority.

18. The network element of claim 17, wherein a network comprises a plurality of network elements capable of synchronization with each of the plurality of network elements'"'"' plurality of inter-node links connected to form the network.

19. The network element of claim 18, wherein the network further comprises one or more network elements without synchronization.

20. The network element of claim 19, wherein the network elements comprise any of Ethernet switches, multi-service switches, computers, routers, Optical Transport Network switches.