Network with a Fast-Switching Optical Core

• US 20080138067A1
• Filed: 12/06/2007
• Published: 06/12/2008
• Est. Priority Date: 12/12/2006
• Status: Active Grant

• Current Assignee: Maged E. Beshai
• Original Assignee: Maged E. Beshai
• Inventors: Beshai, Maged E
• Granted Patent: US 8,050,257 B2
• Time in Patent Office: Days
• US Class Current: 398/45
• CPC Class Codes: H04J 14/0284 WDM mesh architectures
• CPC Class Codes: H04L 49/15 Interconnection of switching modules
• CPC Class Codes: H04L 49/357 Fibre channel switches
• CPC Class Codes: H04Q 11/0005 Switch and router aspects
• CPC Class Codes: H04Q 11/0062 Network aspects
• CPC Class Codes: H04Q 2011/0016 using wavelength multiplexing or demultiplexing
• CPC Class Codes: H04Q 2011/0033 using time division switching
• CPC Class Codes: H04Q 2011/006 Full mesh
• CPC Class Codes: H04Q 2011/0086 Network resource allocation, dimensioning or optimisation
• CPC Class Codes: H04Q 2011/009 Topology aspects
• CPC Class Codes: H04Q 2011/0098 Mesh

Abstract

A high capacity network comprises a plurality of edge nodes with asymmetrical connections to a plurality of switch planes, each switch plane comprising fully meshed fast-switching optical switch units. Upstream wavelength channels from each source edge node connect to different switch planes in a manner which ensures that upstream wavelength channels from any two edge nodes connect to a common switch unit in at most a predefined number, preferably one, of switch planes. Thus, switch units in different switch planes connect to upstream channels from orthogonal subsets of source edge nodes. In contrast, downstream wavelength channels from a switch unit in each switch plane connect to one set of sink edge nodes. In an alternate arrangement, the upstream and downstream asymmetry may be reversed.

Claims

1. A communications network comprising:

a set of switch units arranged in switch planes, each switch plane comprising a subset of said switch units interconnected in a full-mesh structure;

a plurality of source nodes, each source node connecting to a switch unit in each switch plane through at least one upstream channel wherein a first set of source nodes connecting to any switch unit and a second set of source nodes connecting to any other switch unit have a number of common source nodes not exceeding a predefined upper bound; and

a plurality of sink nodes, each sink node connecting to each of selected switch units, one selected switch unit in each switch plane, through at least one downstream channel.

2. The communications network of claim 1 wherein switch units in said subset of switch units are assigned switch-unit identifiers, where said switch-unit identifiers in any switch plane are mirrored in each other switch plane, and wherein said selected switch units have identical switch-unit identifiers within their respective switch planes.

3. The communications network of claim 1 wherein said predefined upper bound equals one so that any pair of source nodes connects at most once to a common switch unit.

4. The communications network of claim 1 wherein said subset of said switch units of said each switch plane comprises collocated switch units.

5. The communications network of claim 4 further comprising, for each switch plane:

a switch-plane controller; and

a configuration controller associated with each switch unit of said each switch plane, said configuration controller receives switch-fabric-configuration instructions from said switch-plane controller.

6. The communications network of claim 5 wherein said switch-plane controller further comprises:

a master time indicator;

a time-locking circuit for receiving time indications from said each source node, and communicating time-locking instructions to a sink node communicatively coupled to said each source node;

and wherein said each source node comprises a slave time indicator associated with said at least one upstream channel, said slave time indicator exchanges time indications with said time-locking circuit for time-locking said each source node to said master time indicator.

7. The communications network of claim 6 wherein:

said each source node sends said time indications to said time-locking circuit of said switch-plane controller during a first reserved time slot, in a predefined slotted time frame, said first reserved time slot being specific to said each source node and said switch-plane controller; and

said time-locking circuit sends said time-locking instructions to a sink node associated with said each source node during a second reserved time slot specific to said each sink node and said switch-plane controller.

8. The communications network of claim 5 wherein said switch-plane controller:

connects to at least one control channel from at least one switch unit, of said each switch plane, for receiving upstream control signals from said plurality of source nodes;

connects to at least one control channel to at least one switch unit, of said each switch plane, for transmitting downstream control signals to said plurality of sink nodes;

maintains an inlet-identification array each entry of which corresponds to a time slot in a predefined time frame and contains an identifier of an inlet port of a first switch unit; and

maintains an outlet-identification array each entry of which corresponds to a time slot in a predefined time frame and contains an identifier of an outlet port of a second switch unit.

9. The communications network of claim 8 wherein:

said each source node receives packets of variable sizes from data sources and assembles received packets into data segments of equal sizes;

said source nodes communicate time-division multiplexed data segments to said sink nodes through said plurality of switch planes;

said each source node transmits an upstream control signal to a switch-plane controller of a selected switch plane during a first dedicated time slot in said predefined time frame corresponding to said each source node and said selected switch plane;

said switch-plane controller transmits a downstream control signal to each sink node during a second dedicated time slot, in said predefined time frame, corresponding to said selected switch plane and said each sink node.

10. The communications network of claim 9 wherein said upstream control signal comprises a connection request specifying a destination sink node and a number of time slots within said predefined time frame, and said switch-plane controller:

identifies, using said inlet-identification array, an inlet port of said selected switch plane at which said first upstream signal is received;

identifies, using said outlet-identification array, an outlet port of said switch plane having a downstream channel to said destination sink node;

performs a first-order time-slot-matching process where said inlet port and outlet port reside on a common switch unit, and communicates a result through said outlet port to a sink node connecting to said outlet port; and

performs a second-order time-slot matching process where said inlet port and outlet port reside on different switch units, and communicates a result through said outlet port to a sink node connecting to said outlet port.

11. The communications network of claim 4 wherein at least two of said switch planes are collocated.

12. The communications network of claim 1 further comprising:

a plurality of upstream wavelength routers each connecting a group of source nodes selected from among said plurality of source nodes to each of said switch planes; and

a plurality of downstream wavelength routers each connecting a switch plane to a group of sink nodes selected from among said plurality of sink nodes.

13. The communications network of claim 12 wherein said at least one upstream channel is routed through one of said upstream wavelength routers and a wavelength demultiplexer, and wherein said at least one downstream channel is routed through a wavelength multiplexer and one of said downstream wavelength routers.

14. The communications network of claim 1 wherein at least one switch unit is an optical switch unit.

15. The communications network of claim 1 wherein at least one of said switch units is a latent space switch comprising:

an array of transit memory devices;

a first rotator connecting a plurality of input channels to said array of transit memory devices; and

a second rotator connecting said array of transit memory devices to a plurality of output ports.

16. The communications network of claim 1 wherein each source node from among said plurality of source nodes is integrated with a sink node from among said plurality of sink nodes to form an integrated edge node.

17. A communications network comprising:

a set of switch units arranged in switch planes, each switch plane comprising a subset of said switch units interconnected in a full-mesh structure;

a plurality of source nodes, each source node connecting to a switch unit in each switch plane through at least one upstream channel;

a plurality of sink nodes, each sink node connecting to a switch unit in each switch plane through at least one downstream channel;

wherein a first set of sink nodes connecting to any switch unit and a second set of sink nodes connecting to any other switch unit have a number of common sink nodes not exceeding a predefined upper bound.

18. A communications network comprising:

a set of switch units arranged in switch planes, each switch plane comprising a subset of said switch units interconnected in a full-mesh structure;

a plurality of source nodes;

a plurality of sink nodes;

a plurality of upstream wavelength routers each connecting a first number of source nodes selected from among said plurality of source nodes to a second number of wavelength demultiplexers each wavelength demultiplexer connecting to one of said switch planes; and

a plurality of downstream wavelength routers each connecting a third number of wavelength multiplexers to a fourth number of sink nodes selected from among said plurality of sink nodes, each wavelength multiplexer connecting to one of said switch planes;

wherein each source node connects to a switch unit in each switch plane through at least one upstream channel routed through one of said upstream wavelength routers wherein a first set of source nodes connecting to any switch unit and a second set of source nodes connecting to any other switch unit have a number of common source nodes not exceeding a predefined upper bound.

19. The communications network of claim 18 wherein each sink node in said plurality of sink nodes is paired with a source node from among said plurality of source nodes, wherein switch units in said subset of switch units in each switch plane are assigned switch-unit identifiers, where said switch-unit identifiers in any switch plane are repeated in each other switch plane, and wherein each sink node has at a downstream channel from each of switch units of identical switch-unit identifiers.

20. The communications network of claim 18 wherein each sink node has at least one downstream channel routed through one of said downstream wavelength routers from at least one switch unit in each switch plane.

21. The communications network of claim 20 wherein each sink node in said plurality of sink nodes is paired with a source node from among said plurality of source nodes to form a source-sink node pair, and said source-sink node pair connects to a same switch unit in each of said switch planes.

22. A communications network comprising:

a set of switch units arranged in Π

>

1 switch planes indexed as 0 to (Π

−

1), each switch plane comprising a subset of G>

1 switch units interconnected in a full-mesh structure, G being a prime number, and switch units of each switch plane are indexed as 0 to (G−

1); and

a plurality of edge nodes arranged into G edge-node groups each edge-node group comprising at most Q>

1 edge nodes, and an edge node within an edge-node group γ

, 0≦

γ

<

G, is indexed as (j, γ

), 0≦

j<

Q<

G;

wherein a switch unit of index k, 0≦

k<

G, in switch plane p, 0≦

p<

Π

, has at least one upstream channel from each of at most Q edge nodes of indices j and γ

=(k+p+j×

p)_{modulo G}, 0≦

j<

Q, and at least one downstream channel to each of at most Q edge nodes of indices j and γ

=k, 0≦

j<

Q;

thereby a subset of source nodes connecting to each switch unit is orthogonal to a subset of source nodes connecting to each other switch unit in said set of switch units and a subset of sink nodes connecting to each switch unit in each switch plane connects to a single switch unit in each other switch plane.

23. A communications network comprising:

a plurality of edge nodes grouped into G>

1 edge-node groups, G being a prime number, each edge-node group comprising at most Q>

1 edge nodes, and edge nodes within an edge-node group γ

, 0≦

γ

<

G, are indexed as (j, γ

), 0≦

j<

Q; and

a set of switch units arranged in Π

>

1 switch planes indexed as 0 to (Π

−

1), each switch plane comprising a subset of G switch units interconnected in a full-mesh structure and switch units of each switch plane are indexed as 0 to (G−

1);

wherein an edge node of index (j, γ

), 0≦

j<

Q<

G, 0≦

γ

<

G, has at least one upstream channel to a switch unit of index ((G−

1−

j)p+γ

)_{modulo G}, in each switch plane p, 0≦

p<

Π

, and at least one downstream channel from a switch unit of index γ

in each switch plane p, 0≦

p<

Π

,

thereby a subset of source nodes connecting to each switch unit is orthogonal to a subset of source nodes connecting to each other switch unit in said set of switch units and a subset of sink nodes connecting to each switch unit in each switch plane connects to a single switch unit in each other switch plane.

24. The communications network of claim 23 wherein each switch unit in each switch plane has N provisioned dual ports, N>

2, including Q outer dual ports communicatively coupled to one of said edge-node groups and (G−

1) inner dual ports connecting to other switch units of said each switch plane, wherein the value of G is selected as a prime number not exceeding (N×

η

/(η

+1))+1, and the value of Q is determined as Q≦

└

(G−

1)/η

┘

, where η

is a predefined minimum expansion factor and └

y┘

denotes an integer part of a real number y.

25. The communications network of claim 24 wherein said plurality of edge nodes exchanges data segments through said Π

>

1 switch planes, said data segments being time-multiplexed in a cyclic time frame having a predefined number of time slots.