Folded Clos architecture switching

• US 6,696,917 B1
• Filed: 09/21/2000
• Issued: 02/24/2004
• Est. Priority Date: 09/21/2000
• Status: Expired due to Fees

• Current Assignee: RPX Clearinghouse LLC (RPX Corporation)
• Original Assignee: Nortel Networks Limited (Nortel Networks Corporation)
• Inventors: Vianna, Rudy, Song, Jian J., Heitner, Michael L.
• Primary Examiner(s): Horabik, Michael
• Assistant Examiner(s): BROWN, VERNAL U
• Application Number:
  US09/666,299
• Time in Patent Office: 1,251 Days
• Field of Search: 340/14.2,2.21,2.28,2.25,2.23,2.22 385/17,16,24 379/271,291,292
• US Class Current: 340/2.22
• CPC Class Codes: H04Q 2213/1302 Relay switches
• CPC Class Codes: H04Q 2213/1304 Coordinate switches, crossbar, 4/2 with relays, coupling field
• CPC Class Codes: H04Q 2213/1334 Configuration within the switch
• CPC Class Codes: H04Q 2213/13341 Connections within the switch
• CPC Class Codes: H04Q 3/68 Grouping or interlacing selector groups or stages

Abstract

A novel folded Clos switch apparatus and method therefore for reducing the number of unemployed I/O terminals of a multistage Clos switching network by partitioning a crossbar switch to provide both the first (yth) and last (x−y+1th) stage of a multistage Clos switch where x is the total number of stages in the general case.

Claims

1. A multistage Clos switching apparatus comprising:

a plurality of crossbar switches connected in x stages where x is an odd integer equal to at least 3, the crossbar switches of a yth stage having n inlets and providing n;

2n−

1 fan-out and the crossbar switches of an x−

y+1th stage providing 2n−

1;

n fan-in, where y is an odd integer between 0 and x and wherein the yth stage crossbar switches and the (x+1)th stage crossbar switches are physically combined and together comprise a plurality of (3n−

1)×

(3n−

1) crossbar switches each being partitioned into a (n×

(2n−

1)) portion and a ((2n−

1×

n) portion.

2. A multistage Clos switching apparatus for selectively connecting any one of N input terminals to any one of M output terminals, the switching network comprising:

a plurality of first stage crossbar switches having (3n−

1) inlets and (2n+m−

1) outlets, each first stage crossbar switch arranged and partitioned into an input stage comprising n inlets and at least (2n−

1) outlets, and an output stage comprising at least (n+m−

1) inlets and m outlets; and

a plurality of second stage crossbar switches each having (N/n) inlets and (N/n) outlets, each inlet connected to its corresponding outlet of the input stage and each outlet connected to its corresponding inlet of the output stage.

3. The non-blocking switching apparatus as set forth in claim 2, wherein the plurality of first stage crossbar switches are configured and arranged in (N/n) stages.

4. A multistage Clos switching apparatus for selectively connecting any one of N input terminals to any one of M output terminals, the switching network comprising:

a plurality of first stage crossbar switches having (2m+n−

1) inlets and (3m−

1) outlets, each first stage crossbar switch arranged and partitioned into an input stage comprising n inlets and at least (m+n−

1) outlets, and an output stage comprising at least (2m−

1) inlets and m outlets; and

a plurality of second stage crossbar switches each having (N/n) inlets and (N/n) outlets, each inlet connected to its corresponding outlet of the input stage and each outlet connected to its corresponding inlet of the output stage.

5. A square multistage Clos switching apparatus for selectively connecting any one of N input terminals to any one of N output terminals, the switching network comprising:

a plurality of first stage crossbar switches having (3n−

1) inlets and (3n−

1) outlets, each first stage crossbar switch arranged and partitioned into an input stage comprising n inlets and at least (2n−

1) outlets, and an output stage comprising at least (2n−

1) inlets and m outlets; and

a plurality of second stage crossbar switches each having (N/n) inlets and (N/n) outlets, each inlet connected to its corresponding outlet of the input stage and each outlet connected to its corresponding inlet of the output stage.

6. A method of aggregating a multistage Clos switching apparatus having an input nth stage, output x−

n+1th stage and a middle stage therebetween where x is an odd integer representing the overall number of stages, each stage having a plurality of switches comprising inlets and outlets, the method comprising;

connecting each outlet of each input stage switch into the corresponding inlet terminal of each center stage switch;

connecting each outlet terminal of each center stage switch into the corresponding inlet terminal of each output stage switch;

aggregating each input stage and its corresponding output stage into a single switch device.