Method and apparatus for high-capacity circuit switching with an ATM second stage switch

• US 6,151,325 A
• Filed: 03/31/1997
• Issued: 11/21/2000
• Est. Priority Date: 03/31/1997
• Status: Expired due to Fees

• Current Assignee: Cisco Systems, Inc.
• Original Assignee: Cisco Technology, Inc. (Cisco Systems, Inc.)
• Inventors: Hluchyj, Michael G.
• Primary Examiner(s): MARCELO, MELVIN C
• Application Number:
  US08/828,883
• Time in Patent Office: 1,331 Days
• Field of Search: 370/356, 370/398, 370/399, 370/465, 370/466
• US Class Current: 370/398
• CPC Class Codes: H04L 12/6402 Hybrid switching fabrics

Abstract

A high-capacity multistage switching system includes a second stage ATM switch that interconnects multiple lower-capacity switch modules. The switching system dynamically establishes a connection between the switch ports of two switch modules, using as part of the connection a permanent virtual connection, i.e., a pre-established connection path, through the ATM switch. Each switch module includes one or more switch ports, an ATM interface card and a time-division-multiplexed "TDM" bus that transfers user data between the switch ports and the ATM interface card. A system controller dynamically establishes connections between two given switch ports establishing one or more virtual trunks to transfer the user data between the TDM buses of the switch modules and cell payloads of ATM cells that are directed over the appropriate pre-established connection path through the ATM switch. The system controller then assigns to the connections transmit and receive timeslots on the TDM bus and octets in virtual trunk structures that are associated with the virtual trunks. The ATM card retrieves user data from the transmit timeslots and places the data in the octets of the virtural trunk structures, and then assembles the structures in ATM cells that are directed along the selected connection path. An ATM card that receives an ATM cell disassembles the cell into the constituent virtual trunk structures and retrieves user data from the octets of the structures and places the data on the TDM bus in the receive timeslots.

Claims

1. A multiple stage switching system for use in telecommunications networks, the switching system including:

A. a plurality of switch modules, each switch module including one or more switch ports, an ATM interface card and a time-division-multiplexed "TDM" bus that transfers user data between the switch ports and the ATM interface card;

B. an asynchronous transfer mode "ATM" switch for interconnecting the switch modules, the ATM switch transferring the user data through the switch over pre-established connection paths;

C. a system controller for dynamically establishing connections between the switch ports of the switch modules by establishing for the connections that include a given pair of switch modules one or more virtual trunks to transfer the user data between the TDM buses of the switch modules and cell payloads of ATM cells that are directed over one of the pre-established connection paths in the ATM switch.

2. The multiple stage switching system of claim 1 wherein:

a. the TDM bus transfers the user data in the form of pulse-code-modulation "PCM" samples that are placed on the TDM bus in timeslots;

b. the ATM interface card transfers the user data in the form of ATM cells, with each ATM cell including in a multiple-octet cell payload a plurality of PCM samples; and

c. the system controller establishes a connection by assigning to each switch port involved in the transfer of the user data

i. transmit and receive timeslots on the TDM bus, and

ii. octets in one or more multiple-octet structures associated with the virtual trunks that the system controller established for the transfer of user data between the two switch modules involved in the connection.

3. The multiple stage switching system of claim 2 wherein the ATM interface card assembles in the structures the PCM samples from the transmit timeslots assigned to a connection, and assembles the structures as the octets of the cell payload of the ATM cell that is directed over the connection path associated with the virtual trunk established for the connection.

4. The multiple stage switching system of claim 3 wherein:

the system controller associates each virtual trunk with a VPI/VCI value, and

the ATM interface card assembles virtual trunk structures in the ATM cell that has in a cell header the same VPI/VCI value as is associated with the virtual trunk.

5. The multiple stage switching system of claim 4 wherein the system controller establishes a new virtual trunk for a new connection when the octets in an established virtual trunk are assigned to prior connections, the system controller associating the new virtual trunk with a VPI/VCI that includes the same VPI that is associated with the established virtual trunk.

6. A method for dynamically establishing connections between switch ports in a switching system that includes an asynchronous transfer mode "ATM" switch that uses permanent virtual connections as a second stage, the method including the steps of:

A. assigning transmit and receive timeslots on a time-division-multiplexed "TDM" bus in each of a plurality of switching modules involved in the connection;

B. assigning octets in multiple-octet structures associated with virtual trunks that use as connection paths through the ATM switch the permanent virtual connections.

7. The method of claim 6, wherein the method further includes the steps of:

C. transferring user data in the form of pulse-code-modulation "PCM" samples to the transmit timeslots assigned to the connection;

D. transferring the PCM samples from the timeslots assigned to the connection to the octets in the structures that are associated with the virtual trunk assigned to the connection;

E. assembling the structures in a cell payload of an ATM cell; and

F. transferring the cell on the connection path associated with the virtual trunk.

8. The method of claim 7, wherein the method further includes the steps of:

G. disassembling an ATM cell received over the connection into the multiple-octet structures associated with the virtual trunk;

H. transferring PCM samples included in the octets of the structures to the receive timeslots assigned to the connection; and

I. removing the PCM samples from the timeslots assigned to the connection and recovering the user data.

9. An apparatus, comprising:

a first interface which converts information between a first communication protocol and a second communication protocol different from said first communication protocol;

a second interface which converts information between said second communication protocol and a third communication protocol different from said second communication protocol;

a first switch port coupled to said first interface by a pre-established first communication path that carries an ongoing first communication stream which conforms to said first communication protocol and which includes a plurality of selectively assignable portions that can each be selectively populated with user data;

a switching section operatively coupled to each of said first and second interfaces, said switching section having between said first and second interfaces a pre-established second communication path that carries an ongoing second communication stream which conforms to said second communication protocol and which includes a plurality of selectively assignable portions that can each be selectively populated with user data;

a second switch port coupled to said second interface by a pre-established third communication path that carries an ongoing third communication stream which conforms to said third communication protocol and which includes a plurality of selectively assignable portions that can each be selectively populated with user data; and

system control structure operable to dynamically establish a virtual path for user data between said first and second switch ports by selectively assigning to said virtual path respective said portions in each of said first, second and third communication streams.

10. An apparatus according to claim 9, wherein said system control structure is operatively coupled to each of said switch ports and each of said interfaces.

11. An apparatus according to claim 9:

including a third interface which converts information between said second communication protocol and a fourth communication protocol different from said second communication protocol;

including a third switch port coupled to said third interface by a pre-established fourth communication path that carries an ongoing fourth communication stream which conforms to said fourth communication protocol and which includes a plurality of selectively assignable portions that can each be selectively populated with user data;

wherein said switching section has between said first and third interfaces a pre-established fifth communication path that carries an ongoing fifth communication stream which conforms to said second communication protocol and which includes a plurality of selectively assignable portions that can each be selectively populated with user data, and has between said second and third interfaces a pre-established sixth communication path that carries an ongoing sixth communication stream which conforms to said second communication protocol and which includes a plurality of selectively assignable portions that can each be selectively populated with user data; and

wherein said system control structure is operable to dynamically establish a virtual path for user data between said first and third switch ports by selectively assigning thereto respective said portions in each of said first, fourth and fifth communication streams, and to dynamically establish a virtual path for user data between said second and third switch ports by selectively assigning thereto respective said portions in each of said second, fourth and sixth communication streams.

12. An apparatus according to claim 9:

including a third switch port operatively coupled to said first interface by said first communication path;

including a fourth switch port operatively coupled to said second interface by said third communication path; and

wherein said system control structure includes a first network bus controller, a first packet communication bus coupling said first network bus controller to said first interface and to said first and third switch ports, a second network bus controller, a second packet communication bus coupling said second network bus controller to said first interface and to said second and fourth switch ports, a system controller, and a network bus coupling said system controller to each of said first and second network bus controllers.

13. An apparatus according to claim 9, wherein said second communication protocol is an asynchronous transfer mode protocol which uses cells having payloads that include said portions of said second communication stream.

14. An apparatus according to claim 13, wherein said first and third communication protocols are the same, and are a time division multiplexing protocol having a plurality of timeslots which serve as said portions of said first and third communication streams.

15. An apparatus comprising a switch module which includes:

a pre-established first communication path that carries an ongoing first communication stream which conforms to a first communication protocol and which includes a plurality of selectively assignable portions that can each be selectively populated with user data;

a link adapted to operatively couple said switch module to external structure, said link including a pre-established second communication path that carries an ongoing second communication stream which conforms to a second communication protocol and which includes a plurality of selectively assignable portions that can each be selectively populated with user data, said second communication protocol being different from said first communication protocol;

an interface which is coupled to said link and to said first communication path, and which converts information between said first communication protocol and said second communication protocol;

first and second switch ports which are each coupled to said first communication path; and

control structure operable to facilitate dynamic establishment of a virtual path for user data from one of said first and second switch ports through said first and second communication paths and said interface by selectively assigning to said virtual path respective said portions in each of said first and second communication streams.

16. An apparatus according to claim 15, wherein said control structure includes a network bus controller adapted to be coupled to a network bus, and a packet communication bus coupling said network bus controller to said interface and first and second switch ports.

17. An apparatus according to claim 16, wherein said control structure includes a system controller, and a network bus operatively coupling said system controller and said network bus controller.

18. An apparatus according to claim 16, including a plurality of card slots which are each coupled to said packet communication bus and to said first communication path, said first and second switch ports each being a card which is removably inserted into a respective one of said card slots.

19. An apparatus according to claim 15, wherein said second communication protocol is an asynchronous transfer mode protocol which uses cells having payloads that include said portions of said second communication stream.

20. An apparatus according to claim 19, wherein said first communication protocol is a time division multiplexing protocol having a plurality of timeslots which serve as said portions of said second communication stream.

21. A method of controlling communication between first and second switch ports which are coupled through respective pre-established first and second communication paths and through respective first and second interfaces to a switching section which includes a pre-established third communication path between said interfaces, each of said first, second and third communication paths carrying a respective one of first, second and third ongoing communication streams which each conform to a respective one of first, second and third communication protocols, and which each include a plurality of selectively assignable portions that can each be selectively populated with user data, said third communication protocol being different from said first and second communication protocols, and said interfaces each being operable to convert information between said third communication protocol and a respective one of said first and second communication protocols, said method comprising the step of dynamically establishing a virtual path for user data between said first and second switch ports by selectively assigning to said virtual path respective said portions in each of said first, second and third communication streams.

22. A method according to claim 21, including a third switch port which is coupled to said switching section through a fourth pre-established communication path and a third interface, said switching section including a pre-established fifth communication path between said first and third interfaces, and a pre-established sixth communication path between said second and third interfaces, each of said fourth, fifth and sixth communication paths carrying a respective one of fourth, fifth and sixth ongoing communication streams which respectively conform to a fourth communication protocol, said third communication protocol, and said third communication protocol, and which each include a plurality of selectively assignable portions that can each be selectively populated with user data, said third communication protocol being different from said fourth communication protocol, and said third interface being operable to convert information between said third and fourth communication protocols, said method comprising the further steps of dynamically establishing a virtual path for user data between said first and third switch ports by selectively assigning thereto respective said portions in each of said first, fifth and fourth communication streams, and dynamically establishing a virtual path for user data between said second and third switch ports by selectively assigning thereto respective said portions in each of said second, sixth and fourth communication streams.

23. A method according to claim 21, including the step of selecting as said third communication protocol an asynchronous transfer mode protocol which uses cells having payloads that include said portions of said third communication stream.

24. A method according to claim 23, wherein said first and second communication protocols are the same, and are a time division multiplexing protocol having a plurality of timeslots which serve as said portions of said first and second communication streams.

25. A computer readable medium encoded with a computer program operable when executed to control communication between first and second switch ports which are coupled through respective pre-established first and second communication paths and through respective first and second interfaces to a switching section which includes between said interfaces a pre-established third communication path, each of said first, second and third communication paths carrying a respective one of first, second and third ongoing communication streams which each conform to a respective one of first, second and third communication protocols, and which each include a plurality of selectively assignable portions that can each be selectively populated with user data, said third communication protocol being different from said first and second communication protocols, and said interfaces each being operable to convert information between said third communication protocol and a respective one of said first and second communication protocols, said control by said computer program of communication between said first and second switch ports including said computer program being operable when executed to dynamically establish a virtual path for user data between said first and second switch ports by selectively assigning to said virtual path respective said portions in each of said first, second and third communication streams.

26. A computer readable medium according to claim 25, wherein said computer program is further operable when executed to control a third switch port which is coupled to said switching section through a fourth pre-established communication path and a third interface, said switching section including a pre-established fifth communication path between said first and third interfaces, and a pre-established sixth communication path between said second and third interfaces, each of said fourth, fifth and sixth communication paths carrying a respective one of fourth, fifth and sixth ongoing communication streams which respectively conform to a fourth communication protocol, said third communication protocol, and said third communication protocol, and which each include a plurality of selectively assignable portions that can each be selectively populated with user data, said third communication protocol being different from said fourth communication protocol, and said third interface being operable to convert information between said third and fourth communication protocols, said control by said computer program including said computer program being operable when executed to dynamically establish a virtual path for user data between said first and third switch ports by selectively assigning thereto respective said portions in each of said first, fifth and fourth communication streams, and dynamically establishing a virtual path for user data between said second and third switch ports by selectively assigning thereto respective said portions in each of said second, sixth and fourth communication streams.

27. A computer readable medium according to claim 25, wherein said computer program is operable to use for said third communication protocol an asynchronous transfer mode protocol which uses cells having payloads that include said portions of said third communication stream, and is operable to use for each of said first and second communication protocols a time division multiplexing protocol having a plurality of timeslots which serve as said portions of said first and second communication streams.