Modular High-Capacity Switch

• US 20110052191A1
• Filed: 11/01/2010
• Published: 03/03/2011
• Est. Priority Date: 08/20/2002
• Status: Active Grant

• Current Assignee: RPX Clearinghouse LLC (RPX Corporation)
• Original Assignee: RPX Clearinghouse LLC (RPX Corporation)
• Inventors: Beshai, Maged E.
• Granted Patent: US 8,792,516 B2
• Time in Patent Office: Days
• US Class Current: 398/52
• CPC Class Codes: H04J 14/08 Time-division multiplex systems
• CPC Class Codes: H04Q 11/0005 Switch and router aspects
• CPC Class Codes: H04Q 11/0071 Provisions for the electrical-optical layer interface
• CPC Class Codes: H04Q 2011/0024 using space switching
• CPC Class Codes: H04Q 2011/0033 using time division switching
• CPC Class Codes: H04Q 2011/0039 Electrical control
• CPC Class Codes: H04Q 2011/005 Arbitration and scheduling
• CPC Class Codes: H04Q 2011/0052 Interconnection of switches

Abstract

A modular optical switch includes a set of optical switch modules connected in a mesh, a master controller for the whole optical node and a switch-module controller for each of the optical switch modules. The optical switch modules receive optical signals from, and transmit optical signals to, edge nodes based on connection requests received from the edge nodes. The master controller acts to select a path, using a simple or compound time-slot matching process, through the mesh of switch modules for each optical signal related to a connection request. Advantageously, the optical switch modules are fast switching, enabling the use of time-sharing schemes such as TDM, and the modular optical core node is made practical by efficient path selection at the master controller. A hybrid modular switch may include both optical and electronic switch modules, a master controller, and a switch-module controller for each of the switch modules.

Claims

1. A method of selecting a path through a modular optical switch comprising:

receiving a request, where said request identifies a requested number of time slots, an inlet port of a first switch module and an outlet port of a second switch module;

responsive to said receiving said request, comparing a state map associated with said inlet port to a state map associated with said outlet port to find a matching time slot that is vacant in both said inlet port and said outlet port;

if said comparing provides said matching time slot, wherein said state maps associated with said respective ports indicate vacancy in said particular time slot, recording said matching time slot in a result record; and

transmitting said result record to a controller of said modular optical switch.

2. The method of claim 1 further comprising repeating said comparing for a subsequent time slot of a first predetermined set of sequential time slots either until said matching time slot has been found or until said state maps associated with each of said first predetermined set of sequential time slots have been compared.

3. The method of claim 1 further comprising:

responsive to said receiving said request, initializing a local index to a value of said requested number of time slots;

where said matching time slot is found, reducing said local index by one; and

generating an indication of successful matching.

4. The method of claim 3 further comprising repeating said comparing, reducing and generating for each of said sequential time slots of said first predetermined set of sequential time slots either until said local index has been reduced to zero or until said state maps associated with each sequential time slot of said first predetermined set of additional time slots have been compared.

5. The method of claim 4 further comprising, where each of said first predetermined set of sequential time slots have been compared and said local index exceeds zero, repeating said comparing, reducing and generating for sequential time slots of a second predetermined set of sequential time slots either until said local index has been reduced to zero or until said state maps associated with each additional time slot of said second predetermined set of sequential time slots have been compared.

6. The method of claim 4 further comprising, where each of said first predetermined set of sequential time slots have been compared and said local index exceeds zero, outputting a request with a requested number of time slots set to a value of said local index.

7. A path selection apparatus comprising:

a plurality of matching units, where each of said plurality of matching units is adapted to;

receive a connection request, where said connection request identifies a requested number of time slots, an inlet port of a first switch module and an outlet port of a second switch module;

responsive to said receiving said time-slot-allocation request, compare a state map, specific to a particular time slot, associated with said inlet port to a state map, specific to said particular time slot, associated with said outlet port to find a matching time slot that is vacant in both said inlet port and said outlet port;

if said comparing provides said matching time slot, wherein said state maps associated with said respective ports indicate vacancy in said particular time slot, record said matching time slot in a result record;

a plurality of result buffers, each of said a plurality of result buffers adapted to receive a result record from an associated one of said plurality of matching units; and

a cyclic selector adapted to select a single result record at a time from each of said plurality of result buffers under control of said cyclic selector.

8. The path selection apparatus of claim 7 wherein each of said plurality of matching units comprises:

a request buffer for receiving said time-slot-allocation request;

a memory adapted to store said state map associated with said inlet port and said state map associated with said outlet port;

a path finding processor adapted to;

receive said connection request from said request buffer;

access said memory; and

perform said comparing to result in a given result record;

and

a selector adapted to;

receive said given result record as a product of said comparing; and

transmit said result record to said associated result buffer.

9. A data structure for simple and compound time-slot matching over a number of time slots to be considered, said data structure for use in a switch module in a modular switch comprising a plurality of switch modules having inlet ports and outlet ports, said data structure comprising:

a first matrix having;

a number of rows equal to a first product of a maximum number of said inlet ports and a maximum number of switch modules; and

a number of columns equal to said number of time slots;

a second matrix having;

a number of rows equal to a second product of a maximum number of said outlet ports and a maximum number of switch modules; and

a number of columns equal to said number of time slots;

a third matrix having;

a number of rows equal to a third product of said maximum number of said inlet ports and a maximum number of time slots to be considered; and

a number of columns equal to a maximum number of said outlet ports;

a fourth matrix having;

a number of rows equal to a fourth product of said maximum number of said outlet ports and a maximum number of time slots to be considered; and

a number of columns equal to said maximum number of inlet ports.

10. The data structure of claim 9 wherein each element in each of said matrices is a 1-bit word indicating an occupancy state.

11. A method of using the data structure of claim 9 for first-order time-slot matching, said method comprising:

finding an entry in a row in said first matrix indicating a vacant occupancy state for an inlet port of a given one of said plurality of switch modules; and

finding an entry in a row in said second matrix indicating a vacant occupancy state for an outlet port of said given one of said plurality of switch modules.

12. A method of using the data structure of claim 9 for second order time-slot matching, said method comprising:

finding an entry in a row in said first matrix indicating a vacant occupancy state for an inlet port of a first one of said plurality of switch modules;

finding an entry in a row in said second matrix indicating a vacant occupancy state for an outlet port of a second one of said plurality of switch modules; and

finding an entry in a row in said third matrix indicating a vacant occupancy state for an inner link to said second one of said plurality of switch modules.

13. A method of using the data structure of claim 9 for third-order time-slot matching, said method comprising:

finding an entry in a row in said first matrix indicating a vacant occupancy state for an inlet port of a first one of said plurality of switch modules;

finding an entry in a row in said second matrix indicating a vacant occupancy state for an outlet port of a second one of said plurality of switch modules;

finding an entry in a row in said third matrix indicating a vacant occupancy state for an inner link to a third one of said plurality of switch modules; and

finding an entry in a row in said fourth matrix indicating a vacant occupancy state for an inner link to said second one of said plurality of switch modules.