Transporting synchronization channel information across a packet network

• US 7,627,004 B2
• Filed: 05/26/2005
• Issued: 12/01/2009
• Est. Priority Date: 05/26/2005
• Status: Active Grant

• Current Assignee: Cisco Technology, Inc. (Cisco Systems, Inc.)
• Original Assignee: Cisco Technology, Inc. (Cisco Systems, Inc.)
• Inventors: Ogagan, George O., Mekala, Anantha R.
• Primary Examiner(s): Shah; Chirag G
• Assistant Examiner(s): SMITH, JOSHUA Y
• Application Number:
  US11/138,599
• Publication Number:
  US 20060268832A1
• Time in Patent Office: 1,650 Days
• Field of Search: 370/352, 370/353, 370/354, 370/401, 370/466, 370/314, 370/321, 370/324, 370/326, 370/337, 370/347, 370/350, 370/467, 370/509, 370510-514
• US Class Current: 370/509
• CPC Class Codes: H04J 3/14 Monitoring arrangements for SDH/SONET rings H04J3/085
• CPC Class Codes: H04J 3/1623 Plesiochronous digital hierarchy [PDH]
• CPC Class Codes: H04L 12/4633 Interconnection of networks using encapsulation techniques, e.g. tunneling
• CPC Class Codes: H04L 49/90 Buffering arrangements
• CPC Class Codes: H04L 49/9042 Separate storage for different parts of the packet, e.g. header and payload
• CPC Class Codes: H04Q 3/0045 involving hybrid, i.e. a mixture of public and private, or multi-vendor systems

Abstract

A technique for preserving information contained in a synchronization channel of a Time Division Multiplexing (TDM) frame across a packet network. Information contained in the synchronization channel of TDM frames is transferred over the packet network by a first gateway device that received the TDM frames. A second gateway device receives the synchronization channel information and places the information in one or more TDM frames. The TDM frames are transferred onto the TDM network.

Claims

1. A method for preserving information contained in time division multiplexing (TDM) frames received from a TDM network, the information preserved in packets transmitted across a packet network, the method comprising:

receiving a plurality of TDM frames, each TDM frame having a synchronization channel, the synchronization channels alternating, over at least three TDM frames, between carrying a frame alignment signal portion having a synchronization pattern used to locally synchronize transfer of the TDM frames and a non-frame alignment signal portion containing other information that is not TDM frame synchronization information;

extracting the other information contained in the non-frame alignment portion of the synchronization channels, the extracted other information representing information other than synchronization information;

placing the extracted other information into a non-synchronization information portion of an outgoing packet; and

transmitting the outgoing packet onto the packet network.

2. A method as defined in claim 1 wherein the packet is an Asynchronous Transfer Mode (ATM) Adaptation Layer 2 (AAL2) packet.

3. A method as defined in claim 1 further comprising:

(a) generating a cyclic redundancy check (CRC) for the packet; and

(b) placing the CRC into the packet.

4. A method as defined in claim 1 further comprising:

(a) generating a flag that indicates when the extracted other information from the synchronization channel are present in the packet; and

(b) placing the flag into the packet.

5. A method as defined in claim 1 wherein the extracted other information is transferred onto the packet network after an amount of the extracted other information has been placed in a buffer.

6. A method as defined in claim 1 wherein the extracted other information is transferred onto the packet network after a predetermined amount of time has elapsed.

7. A method as defined in claim 1 wherein the TDM frame is an E1 frame.

15. A method as defined in claim 1 wherein the extracted other information is payload data.

16. A method as defined in claim 1 wherein the extracted other information are SA bits.

17. A method as defined in claim 1 wherein the extracted other information are from a non-Frame Alignment Signal (non-FAS) portion of the TDM frame.

18. A method as defined in claim 1 wherein the extracted other information are encoded High level Data Link Control (HDLC) frames.

19. A method as defined in claim 1 farther comprising:

delaying the step of transmitting the outgoing packet until observing a pattern change in the non-frame alignment signal portion of the synchronization channel of successive received frames.

20. A method as defined in claim 1 further comprising:

delaying the step of transmitting the outgoing packet until after a predetermined period of time has elapsed.

21. A method as defined in claim 18 further comprising:

receiving the HDLC frames from the packet network;

extracting the other information from the HDLC frames;

placing the other information in a payload portion of a service specific transmission error detection (SSTLD) frame; and

transmitting the SSTED frame to a destination via the packet network.

22. The method as defined in claim 21 further comprising:

generating a cyclic redundancy check (CRC) of the SSTED from at a destination;

discarding the received frame in an event the CRC fails; and

otherwise extracting the other information from the payload portion of the SSTED frame.

8. An apparatus for preserving information contained in time division multiplexing (TDM) frames received from a TDM network, the information preserved in packets transmitted across a packet network, the apparatus comprising:

a TDM interface configured to receive a of TDM frames, each TDM frame having a synchronization channel, the synchronization channels alternating, over at least three TDM frames, between carrying a frame alignment signal portion having a synchronization pattern used to locally synchronize transfer of TDM frames and a non-frame alignment signal portion containing other information that is not TDM frame synchronization information;

an extractor configured to extract the other information contained in the non-frame alignment portion of the synchronization channels, the extracted other information representing other than synchronization information; and

an encapsulator configured to;

(a) place the extracted other information into a packet, and

(b) forward the packet onto the packet network.

9. An apparatus as defined in claim 8 further comprising:

a buffer accessible to the encapsulator and configured to store the extracted other information.

10. An apparatus as defined in claim 9 wherein the packet is forwarded after a predetermined amount of the extracted other information has been stored in the buffer.

11. An apparatus as defined in claim 8 wherein the packet is forwarded after a predetermined period of time has elapsed.

12. An apparatus for transferring information contained in time division multiplexing (TDM) frames onto a packet network, the apparatus comprising:

means for receiving a plurality of TDM frames, each TDM frame having a synchronization channel, the synchronization channels alternating, over at least three TDM frames, between carrying a frame alignment signal portion having a synchronization pattern used to locally synchronize transfer of TDM frames and a non-frame alignment signal portion containing other information that is not TDM frame synchronization information;

means for extracting the other information contained in the non-frame alignment portion of the synchronization channels, the extracted other information representing information other than synchronization information;

means for placing the extracted other information into a packet; and

means for forwarding the packet onto the packet network.

13. A system for preserving data information contained in time division multiplexing (TDM) frames received from a TDM network in packets transmitted across a packet network, the system comprising:

a first node configured to;

(a) receive a plurality of TDM frames, each TDM frame having a synchronization channel, the synchronization channels alternating, over at least three TDM frames, between carrying a frame alignment signal portion having a synchronization pattern used to locally synchronize transfer of TDM frames and a non-frame alignment signal portion containing other information that is not TDM frame synchronization information;

(b) extract other information contained in the non-frame alignment portion of the synchronization channels, the extracted other information representing information other than synchronization information;

(c) place the extracted other information into a packet, and

(d) forward the packet onto the packet network; and

a second node configured to;

(a) receive the packet,

(b) extract the other information from the packet, and

(c) place the extracted data other information into a synchronization

channel of a second TDM frame.

14. A computer-readable medium comprising computer-executable instructions executed by a computer for:

receiving a plurality of time division multiplexing (TDM) frames, each TDM frame having a synchronization channel, the synchronization channels alternating, over at least three TDM frames, between carrying a frame alignment signal portion having a synchronization pattern used to locally synchronize transfer of TDM frames and a non-frame alignment signal portion containing other information that is not TDM frame synchronization information;

extracting the other information contained in the non-frame alignment portion of the synchronization channels, the extracted other information representing information other than synchronization information;

placing the extracted other information into a packet; and

forwarding the packet onto a packet network.