Scalable optical-core network

• US 20080075071A1
• Filed: 09/25/2006
• Published: 03/27/2008
• Est. Priority Date: 09/25/2006
• Status: Active Grant

• Current Assignee: RPX Clearinghouse LLC (RPX Corporation)
• Original Assignee: Nortel Networks Limited (Nortel Networks Corporation)
• Inventors: Beshai, Maged E.
• Granted Patent: US 8,428,071 B2
• Time in Patent Office: Days
• US Class Current: 370/386
• CPC Class Codes: H04B 10/27 Arrangements for networking
• CPC Class Codes: H04Q 11/0005 Switch and router aspects
• CPC Class Codes: H04Q 2011/0032 using static wavelength routers (e.g. arrayed waveguide grating router [AWGR] )
• CPC Class Codes: H04Q 2011/0039 Electrical control
• CPC Class Codes: H04Q 2011/0045 Synchronisation
• CPC Class Codes: H04Q 2011/0056 Clos

Abstract

A network comprising a large number of electronic edge nodes interconnected through bufferless optical switch planes so that a signal from any edge node to any other edge node traverses only one switch plane scales to a capacity of hundreds of petabits per second while providing global geographic coverage. Each edge node is time-locked to each optical switch plane to which it connects to enable loss-free time-sharing of the network core despite the absence of buffers in the core. In an alternate implementation, a relatively small number of electronic switch units may be employed in a predominantly-optical core. In addition to scalability and high performance, the simple structure of the network significantly simplifies addressing and routing.

Claims

1. A network comprising:

a plurality of switch planes each comprising a plurality of first switch units interconnected through a plurality of second switch units, each of the first switch units having a switching latency substantially less than a switching latency of each of the second switch units and a dimension substantially less than a dimension of each of the second switch units; and

a plurality of edge nodes each having at least one upstream channel to at least one of the first switch units and at least one downstream channel from at least one of the first switch units.

2. The network of claim 1 wherein each switch plane further comprises:

a switch-plane controller; and

a plurality of switch-unit controllers each in communication with the switch plane controller and a respective one of the first switch units.

3. The network of claim 2 further comprising:

a plurality of master time counters each in communication with a respective one of the switch planes;

for each switch plane, a plurality of master time-locking circuits each in communication with a respective one of the first switch units and in communication with the master time counter of the switch plane, and

for each edge node, a plurality of slave time-locking circuits each in communication with a master time-locking circuit of one of the switch planes.

4. The network of claim 2 wherein each of the first switch units provides a reserved control path from at least one inlet port of the each of the first switch units to a respective switch-unit controller from among the plurality of switch-unit controllers for a duration of at least one time slot in a predefined time frame

5. The network of claim 2 further comprising a global reconfiguration server in communication with one of the edge nodes for receiving condensed traffic data from the plurality of edge nodes.

6. The network of claim 2 further comprising:

an upstream wavelength router for distributing wavelength channels of multiple wavelength-division-multiplexed (WDM) upstream links, from a subset of the edge nodes, among a plurality of WDM links each directed to one of the switch planes; and

a downstream wavelength router for distributing wavelength channels of a plurality of WDM links each originating from one of the switch planes among a plurality of downstream WDM links each directed to one of the edge nodes.

7. The network of claim 1 wherein at least one of the first switch units is an optical switch unit.

8. The network of claim 2 further comprising a scheduler in communication with the switch-plane controller, wherein the scheduler performs first-order time-slot-matching processes to allocate time slots in a predefined time frame for connections completed within the first switch units and the scheduler performs second-order time-slot-matching processes to allocate time slots in the predefined time frame for connections traversing any pair of the first switch units.

9. A network comprising:

a plurality of switch planes, each switch plane comprising a plurality of first switch units interconnected through a switch-plane core, the switch-plane core comprising;

a plurality of second switch units wherein each of the first switch units has a switching latency substantially less than a switching latency of each of the second switch units and a dimension substantially less than a dimension of each of the second switch units;

at least one electronic switch unit having a dimension exceeding the dimension of each of the second switch units; and

a switch-plane controller in communication with a selected one of the at least one electronic switch units; and

a plurality of edge nodes each having at least one upstream channel to at least one of the first switch units and at least one downstream channel from at least one of the first switch units.

10. The network of claim 9 further comprising:

a master time counter in communication with the switch-plane controller;

at least one master time-locking circuit in communication with the master time counter, and

for each of the edge nodes, a plurality of slave time-locking circuits, each slave time-locking circuit in communication with one of the at least one master time-locking circuit.

11. The network of claim 9 further comprising, for each switch plane, a scheduler in communication with the switch-plane controller, wherein the scheduler performs a first-order time-slot-matching process to allocate at least one time slot in a predefined time frame for a connection completed within one of the first switch units, performs a second-order time-slot-matching process to allocate at least one time slot in the predefined time frame for a connection traversing any pair of the first switch units and one of the second switch units, and performs three first-order time-slot-matching processes to allocate at least one time slot in the predefined time frame for a connection traversing any pair of the first switch units and an electronic switch unit from among the at least one electronic switch unit.

12. The network of claim 9 wherein each of the switch planes provides a reserved control path for a duration of a time slot in a predefined time frame from each edge node to the switch-plane controller, the control path traversing a first switch unit and the electronic switch unit.

13. The network of claim 9 further comprising, for each switch plane, a slave controller in communication with each of the second switch units, the slave controller in communication with a global reconfiguration server for receiving configuration-change instructions for at least one of the second switch units.

14. The network of claim 11 wherein the scheduler comprises a plurality of pipelined processing units.

15. A method of switching through a switch plane in a network, the method comprising:

switching signals through a plurality of first switch units;

switching the signals through a plurality of second switch units, each of the first switch units adapted for reconfiguration at a reconfiguration rate greater than a reconfiguration rate of each of the second switch units; and

switching the signals through a plurality of third switch units, each of the third switch units having a reconfiguration rate greater than the reconfiguration rate of each of the second switch units.

16. The method of claim 15 wherein the reconfiguration rates of each of the first switch units and each of the third switch units are at least an order of magnitude greater than the reconfiguration rate of each of the second switch units.

17. The method of claim 15 further comprising a process of periodic reconfiguration of at least one of the second switch units based on configuration-change instructions received from a global reconfiguration server.

18. The method of claim 16 further comprising performing second-order time-slot matching processes to schedule connections for the signals through the first switch units and the third switch units.

19. The method of claim 16 comprising, prior to the switching of signals through the first plurality of switch units, performing a time-alignment of the signals.

20. The method of claim 19 wherein the time-alignment comprises exchanging time indicators between a controller of the switch plane and controllers of sources of the signals.