Burst switching in a high capacity network

• US 20020085491A1
• Filed: 12/29/2000
• Published: 07/04/2002
• Est. Priority Date: 12/29/2000
• Status: Active Grant

• Current Assignee: RPX Clearinghouse LLC (RPX Corporation)
• Original Assignee: Notel Networks Ltd (Oclaro (North America), Inc.)
• Inventors: Beshai, Maged E., Vickers, Richard
• Granted Patent: US 6,907,002 B2
• Time in Patent Office: Days
• US Class Current: 370/230
• CPC Class Codes: H04Q 11/0066 Provisions for optical burst or packet networks
• CPC Class Codes: H04Q 11/06 Time-space-time switching
• CPC Class Codes: H04Q 2011/0039 Electrical control
• CPC Class Codes: H04Q 2011/0064 Arbitration, scheduling or medium access control aspects
• CPC Class Codes: H04Q 2011/0088 Signalling aspects
• CPC Class Codes: H04Q 2213/1305 Software aspects
• CPC Class Codes: H04Q 2213/13103 Memory
• CPC Class Codes: H04Q 2213/13106 Microprocessor, CPU
• CPC Class Codes: H04Q 2213/13164 Traffic (registration, measurement,...)
• CPC Class Codes: H04Q 2213/13166 Fault prevention
• CPC Class Codes: H04Q 3/0091 Congestion or overload control

Abstract

At a master controller of a space switch in a node in a data network, a request is received from a source node that requests a connection to be established through the space switch. This request is compared to other such requests so that a schedule may be established for access to the space switch. The schedule is then sent to the source nodes as well as to a slave controller of the space switch. The source nodes send data bursts which are received at the space switch during a short guard time between successive reconfigurations of the space switch. Data bursts are received at the space switch at a precisely determined instant of time that ensures that the space switch has already reconfigured to provide requested paths for the individual bursts. The scheduling is pipelined and performed in a manner that attempts to reduce mismatch intervals of the occupancy states of input and output ports of the space switch. The method thus allows efficient utilization of the data network resources while ensuring virtually no data loss.

Claims

1. A method of controlling a space switch to establish time-varying connections, said method comprising:

receiving a stream of burst transfer requests from a source node, each of said burst transfer requests including parameters specifying a requested connection and a duration for said requested connection;

generating scheduling information for each of said burst transfer requests based on said parameters;

transmitting said scheduling information to said source node; and

transmitting instructions to a slave controller for said space switch, where said instructions are based on said scheduling information and instruct said space switch to establish said requested connection.

2. The method of claim 1 wherein said scheduling information includes an indication of a time at which said space switch will be scheduled to establish said requested connection.

3. A space switch master controller comprising:

a source interface for;

receiving a stream of burst transfer requests from a source node, each of said burst transfer request including parameters specifying a requested connection and a duration for said requested connection;

transmitting scheduling information for each of said burst transfer requests to said source node;

a burst scheduler for generating said scheduling information for each of said burst transfer requests in said stream based on said parameters; and

a slave controller interface for transmitting instructions to a slave controller for said space switch, where said instructions are based on said scheduling information and instruct said space switch to establish said requested connection.

4. A computer readable medium containing computer-executable instructions which, when performed by a processor in a space switch master controller, cause the processor to:

receive a stream of burst transfer requests from a source node, each of said burst transfer requests including parameters specifying a requested connection and a duration for said requested connection;

generate scheduling information for each of said burst transfer requests based on said parameters;

transmit said scheduling information to said source node; and

transmit instructions to a slave controller for said space switch, where said instructions are based on said scheduling information and instruct said space switch to establish said requested connection.

5. A method of generating scheduling information comprising:

determining a next-available input port among a plurality of input ports and a time index at which said next-available input port will become available;

for each burst transfer request of a plurality of burst transfer requests received in relation to said next-available input port, and where each said each burst transfer request includes an identity of a burst and a destination for said burst;

determining, from said destination for said burst, a corresponding output port among a plurality of output ports;

determining a time gap, where said time gap is a difference between;

said time index at which said next-available input port will become available; and

a time index at which said corresponding output port will become available;

selecting one of said plurality of burst transfer requests as a selected burst transfer request, where said selected burst transfer request has a minimum time gap of said plurality of burst transfer requests;

selecting a scheduled time index, where said scheduled time index is one of said time index at which said next-available input port is available and said time index at which said corresponding output port is available; and

transmitting scheduling information for a burst identified by said selected burst transfer request, said scheduling information based on said scheduled time index.

6. The method of claim 5 wherein said determining said next-available input port comprises scanning a time calendar until an input port identifier is detected in a time slot, said calendar having a plurality of time slots, where each time slot corresponds to a predefined time interval.

7. The method of claim 6 wherein said determining said time gap comprises reading said time index at which said corresponding output port is available from an element in an array, where said element is associated with said corresponding output port.

8. The method of claim 7 further comprising:

determining, from said selected burst transfer request, a transfer-time for said burst;

adding said transfer-time to said scheduled time index to result in a finishing time index; and

writing said input port identifier in a time slot corresponding to said finishing time index.

9. The method of claim 8 further comprising writing a null identifier in a time slot corresponding to said scheduled time index.

10. The method of claim 9 further comprising writing said finishing time index to said element in said array.

11. The method of claim 10 wherein said array is one of a plurality of arrays and said writing said finishing time index comprises writing said finishing time index to the element that is associated with said corresponding output port in each of said plurality of arrays.

12. The method of claim 11 wherein said writing in each of said plurality of arrays is performed in parallel.

13. The method of claim 10 wherein said time index at which said corresponding output port is available is selected as said scheduled time index.

14. The method of claim 10 wherein a calendar time slot index at which said input port identifier is detected is selected as said scheduled time index.

15. The method of claim 6 wherein said input port identifier is detected only if included in a predetermined group of input port identifiers.

16. The method of claim 15 wherein burst transfer requests are organized by groups of output ports and said determining said time gap is limited to include only chose burst transfer requests corresponding to a group of said plurality of output ports.

20. The core node of claim 19 further comprising a master controller for said space switch, for:

receiving a stream of burst transfer requests from a source node, each of said burst transfer requests including parameters specifying a requested connection and a duration for said requested connection;

generating scheduling information for each said burst transfer request based on said parameters;

transmitting said scheduling information to said source node; and

transmitting said instructions to said slave controller for said space switch, where said instructions are based on said scheduling information.

17. A burst scheduler comprising a processor operable to:

determine a next-available input port among a plurality of input ports and a time index at which said next-available input port will become available;

for each burst transfer request of a plurality of burst transfer requests received in relation to said next-available input port, and where each said each burst transfer request includes an identity of a burst and a destination for said burst;

determine, from said destination for said burst, a corresponding output port among a plurality of output ports;

determine a time gap, where said time gap is a difference between;

said time index at which said next-available input port will become available; and

a time index at which said corresponding output port will become available;

select one of said plurality of burst transfer requests as a selected burst transfer request, where said selected burst transfer request has a minimum time gap of said plurality of burst transfer requests;

select a scheduled time index, where said scheduled time index is one of said time index at which said next-available input port is available and said time index at which said corresponding output port is available; and

generate scheduling information for a burst identified by said selected burst transfer request, said scheduling information based on said scheduled time index.

18. A computer readable medium containing computer-executable instructions which, when performed by a processor in a burst scheduler, cause the processor to:

determine a next-available input port among a plurality of input ports and a time index at which said next-available input port will become available;

for each burst transfer request of a plurality of burst transfer requests received in relation to said next-available input port, and where each said each burst transfer request includes an identity of a burst and a destination for said burst;

determine, from said destination for said burst, a corresponding output port among a plurality of output ports;

determine a time gap, where said time gap is a difference between;

said time index at which said next-available input port will become available; and

a time index at which said corresponding output port will become available;

select one of said plurality of burst transfer requests as a selected burst transfer request, where said selected burst transfer request has a minimum time gap of said plurality of burst transfer requests;

select a scheduled time index, where said scheduled time index is one of said time index at which said next-available input port is available and said time index at which said corresponding output port is available; and

generate scheduling information for a burst identified by said selected burst transfer request, said scheduling information based on said scheduled time index.

19. A core node in a data network comprising:

a space switch;

a plurality of input ports;

a plurality of output ports; and

a slave controller for said space switch for receiving instructions from a master controller of said space switch, said instructions including specifications of temporary connections to establish between said plurality of input ports and said plurality of output ports and indications of timing with which to establish said connections.

21. A data network comprising:

a plurality of edge nodes;

a plurality of core nodes, each core node of said plurality of core nodes including a space switch; and

a master controller for one said space switch in one said core node for;

receiving a stream of burst transfer requests from one of said plurality of edge nodes, each of said burst transfer requests including parameters specifying a requested connection and a duration for said requested connection;

generating scheduling information for each of said burst transfer requests based on said parameters;

transmitting said scheduling information to said one of said plurality of edge nodes; and

transmitting said instructions to a slave controller for said one said space switch, where said instructions are based on said scheduling information.