Failure tolerant high density dial router

• US 6,330,221 B1
• Filed: 06/18/1998
• Issued: 12/11/2001
• Est. Priority Date: 06/18/1998
• Status: Expired due to Term

• Current Assignee: Cisco Technology, Inc. (Cisco Systems, Inc.)
• Original Assignee: Cisco Technology, Inc. (Cisco Systems, Inc.)
• Inventors: Gomez, Rafael
• Primary Examiner(s): Kizou, Hassan
• Assistant Examiner(s): TRAN, THIEN D
• Application Number:
  US09/099,877
• Time in Patent Office: 1,272 Days
• Field of Search: 370/216, 370/217, 370/219, 370/221, 370/225
• US Class Current: 370/217
• CPC Class Codes: H04M 3/12 Marking faulty circuits "busy"; Enabling equipment to disengage itself from faulty circuits ; Using redundant circuits; Response of a circuit, apparatus or system to an error
• CPC Class Codes: H04M 7/125 Details of gateway equipment
• CPC Class Codes: H04Q 2213/13003 Constructional details of switching devices
• CPC Class Codes: H04Q 2213/13034 A/D conversion, code compression/expansion
• CPC Class Codes: H04Q 2213/13076 Distributing frame, MDF, cross-connect switch
• CPC Class Codes: H04Q 2213/13167 Redundant apparatus
• CPC Class Codes: H04Q 2213/13196 Connection circuit/link/trunk/junction, bridge, router, gateway
• CPC Class Codes: H04Q 2213/13298 Local loop systems, access network
• CPC Class Codes: H04Q 2213/13389 LAN, internet
• CPC Class Codes: H04Q 3/0045 involving hybrid, i.e. a mixture of public and private, or multi-vendor systems

Abstract

A Fault Tolerant Dial Router (FTDR) includes redundant subsystem resources that operate independently of telephone line interface connections. The redundant resources are switched active when a failure is detected in an activated dial router subsystem. Switching out subsystem failures is fully automated under software control, providing uninterrupted service to users with limited performance loss. The FTDR includes a switching mechanism that selectively switches out the telephone interfaces or other subsystem resources inside the dial router box detected as having failures. The subsystem resources include line framers, controllers and modem modules.

Claims

1. A fault tolerant dial router, comprising:

a primary line interface unit coupled to telephone lines from a telephone network;

a primary conversion subsystem converting calls on the telephone lines into packets;

a router routing the packets on a packet based network; and

a primary cross-connect switch coupled between the primary line interface unit and the primary conversion subsystem that reconnects the primary line interface unit to a secondary conversion subsystem when a failure is detected in the primary subsystem, the primary cross-connect switch also configurable to switch around a failed primary line interface unit while maintaining operation of the primary conversion subsystem connected to the failed primary line interface unit by disconnecting the primary line interface unit from the primary conversion subsystem and connecting a secondary line interface unit to the primary conversion subsystem.

2. A dial router according to claim 1 including a secondary cross-connect switch in a secondary feature card, the secondary cross-connect switch coupled between a secondary line interface unit and a secondary conversion subsystem, the primary cross-connect switch configurable to connect either one of the primary line interface unit and the primary conversion subsystem to the secondary cross-connect switch and the secondary cross-connect switch configurable to connect either one of the secondary line interface unit and secondary conversion subsystem to the primary cross-connect switch.

3. A dial router according to claim 2 wherein the secondary line interface unit is coupled in parallel with the primary line interface unit to the telephone lines, the primary line interface unit automatically deactivated and the secondary line interface unit automatically activated when a failure is detected on the primary line interface unit and the primary and secondary cross-connect switch automatically reconfiguring to connect the secondary line interface to the primary conversion subsystem.

4. A dial router according to claim 1 wherein the primary conversion subsystem includes a framer for framing multiple groups of telephone calls into individual telephone calls and modem modules for converting the individual telephone calls into packets.

5. A dial router according to claim 4 including a DS0 cross-connect switch redirecting individual DS0 calls from individual failed modem modules to individual standby modems and the primary cross-switch comprising a switch redirecting groups of DS1 calls from failed framers or failed banks of modems to secondary framers or secondary banks of modems.

6. A dial router according to claim 1 including multiple feature cards each having a cross-connect switch connected between a line interface unit and a conversion subsystem, the cross-connect switches in the feature cards all connected together for connecting the line interface unit in any feature card to the conversion subsystem in any other feature cards.

7. A dial router according to claim 6 wherein at least one of the feature cards receives and converts between channelized T1 telephone calls and network IP packets and at least one of the feature cards converts between channelized T3 telephone calls and network IP packets.

8. A dial router according to claim 6 including a processor on each feature card that monitors for failures and a central controller that reconfigures the cross-connect switches on each feature card according to the monitored failures.

9. A dial router according to claim 1 wherein the primary line interface unit includes multiple line interface modules each connected to a separate T1 telephone line.

10. A cross-connect switch for reconfiguring different functional elements in a dial router, comprising:

a first interface coupled to a telephone line interface unit that receives telephone line signals;

a second interface coupled to a framer that frames the telephone line signals into individual telephone calls;

a third interface coupled to another framer in the dial router and to another telephone line interface unit;

the first interface disconnecting the telephone line interface unit from the framer unit and the third interface then automatically connecting the other telephone line interface unit to the framer when the telephone line interface unit fails.

11. A cross-connect switch according to claim 10 including:

a first multiplexer selectively coupling inputs from either one of the second and third interface to the first interface;

a second multiplexer selectively coupling inputs from either one of the first or third interface to the second interface, and

a third multiplexer selectively coupling inputs from either one of the first and second interface to the third interface.

12. A cross-connect switch according to claim 11 including a configuration register that configures which interface is output from each multiplexer.

14. A method according to claim 12 including reconfiguring the concentrator to reconfigure the telephone data stream around individual failed modem modules in the subsystem while remaining modem modules convert the telephone calls into digital packets.

15. A method according to claim 14 including reconfiguring the concentrator to reconnect the telephone data stream around an entire bank of modem units or around a framer in the subsystem identified as causing call failures while the line interface unit continues to receive calls from the telephone network.

13. A method for increasing fault tolerance in a telephone line concentrator, comprising:

activating line interface units for receiving telephone call data streams from a telephone network;

activating subsystems for separating the data streams on the telephone lines into separate telephone channels and extracting digital data from the channels;

converting the digital data into packets and routing the digital packets on a packet based network;

monitoring the line interface units and subsystems for failures; and

automatically reconfiguring the concentrator to reconnect telephone signals around any one of the monitored line interface units and subsystems having a detected failure while keeping any remaining operating line interface units and operating subsystems available for continued processing of the telephone call data stream by disconnecting a failed one of the line interface units from an operating one of the subsystems and reconnecting the operating one of the subsystems to a different one of the operating line interface units.

16. A computer-readable medium containing software for handling fault tolerance in a telephone line concentrator, comprising:

code for activating line interface units for receiving telephone call data streams from a telephone network;

code for activating subsystems for separating the data streams on the telephone lines into separate telephone channels and extracting digital data from the channels;

code for converting the digital data into packets and routing the digital packets on a packet based network;

code for monitoring the line interface units and subsystems for failures; and

code for automatically reconfiguring the concentrator to reconnect telephone signals around any one of the monitored line interface units and subsystems having a detected failure while keeping any remaining operating interface units and subsystems available for continued processing of the telephone call data stream by disconnecting a failed one of the line interface units from an operating one of the subsystems and reconnecting the operating one of the subsystems to a different one of the operating line interface units.

17. A computer-readable medium according to claim 16 including code for reconfiguring the concentrator to reconfigure the telephone data stream around individual failed modem modules in the subsystem while remaining modem modules convert the telephone calls into digital packets.

18. A computer-readable medium according to claim 17 including code for reconfiguring the concentrator to reconnect the telephone data stream around an entire bank of modem units or around a framer in the subsystem identified as causing call failures while the line interface unit continues to receive calls from the telephone network.