Bimodal burst switching

• US 7,756,141 B1
• Filed: 09/20/2007
• Issued: 07/13/2010
• Est. Priority Date: 09/20/2007
• Status: Expired due to Fees

• Current Assignee: RPX Clearinghouse LLC (RPX Corporation)
• Original Assignee: Nortel Networks Limited (Nortel Networks Corporation)
• Inventors: Jamoussi, Bilel N., Beshai, Maged E.
• Primary Examiner(s): Ton, Dang T
• Assistant Examiner(s): Zhao, Wei
• Application Number:
  US11/858,373
• Time in Patent Office: 1,027 Days
• Field of Search: 370/400, 709/239
• US Class Current: 370/400
• CPC Class Codes: H04L 47/10 Flow control; Congestion control
• CPC Class Codes: H04Q 11/0066 Provisions for optical burst or packet networks
• CPC Class Codes: H04Q 2011/0064 Arbitration, scheduling or medium access control aspects

Abstract

In a first mode of burst communication in a telecommunication network comprising electronic edge nodes interconnected by bufferless core nodes, data bursts are formulated at the edge nodes, respective burst descriptors are communicated to a controller of a core node, and burst-transfer schedules are sent from the core node to respective edge nodes. In a second mode, each burst-stream is allocated a flow rate and a core node determines burst sizes and schedules burst-transfer permits.

In a bimodal burst-switching network comprising edge nodes interconnected by core nodes, an edge node selects to send to a core node burst-transfer requests according to the first mode, or flow-rate-allocation requests according to the second mode, depending on proximity, storage capacity at the edge node, and delay-tolerance specifications.

Claims

1. A bimodal burst-switching network comprising a plurality of edge nodes each having an edge controller, said plurality of edge nodes connecting to at least one core node where at least one edge node:

determines proximity of the edge node to a selected core node;

selects a first-mode of burst transfer when said proximity is within a predefined proximity threshold; and

selects a second-mode of burst transfer when said proximity is beyond said predefined proximity threshold;

wherein a controller of an outbound port of an edge node determined to be within said predefined proximity threshold from said selected core node;

forms data bursts;

sends descriptors of said data bursts to a core-node controller of said selected core node;

receives burst-transmission schedules from said core-node controller; and

transmits said data bursts to said selected core node according to said burst-transmission schedules.

3. The network of claim 1 wherein said selected core node is a bufferless core node comprising an optical-switching fabric, a core controller, and means for exchanging time-locking measurements with at least one of said plurality of edge nodes, and wherein said proximity is determined as a function of propagation delay and service-quality criteria, where said service-quality criteria include burst-transfer delay.

4. The network of claim 3 wherein said proximity is determined as a function of propagation delay and flow-rate allocation.

5. The network of claim 3 wherein said proximity is determined as a function of propagation delay and storage capacity at said at least one edge node.

6. The network of claim 5 wherein said proximity is determined as the ratio ρ

×

τ

/Λ

where ρ

is an allocated flow-rate for a burst stream, τ

is a round-trip propagation delay between said selected edge node and said selected core node, and Λ

is the total size of an outbound buffer at a respective outbound port of said at least one edge node.

2. A bimodal burst-switching network comprising a plurality of edge nodes each having an edge controller, said plurality of edge nodes connecting to at least one core node where at least one edge node:

determines proximity of the edge node to a selected core node;

selects a first-mode of burst transfer when said proximity is within a predefined proximity threshold; and

selects a second-mode of burst transfer when said proximity is beyond said predefined proximity threshold;

wherein a controller of an outbound port of an edge node not within said predefined proximity threshold from said selected core node;

sends flow-rate allocations to said core-node controller;

receives nominal burst descriptors and nominal-burst-transmission schedules from said core-node controller;

forms data bursts according to said nominal burst descriptors; and

transmits said data bursts to said selected core node according to said burst-transmission schedules.

7. In a network comprising a plurality of independent bufferless core nodes interconnecting a plurality of edge nodes, each of said plurality of edge nodes having an edge-node controller and each of said core node having a core-node controller, a method of bimodal burst scheduling implemented by a first edge node selected from among said edge nodes, the method comprising steps of:

determining a total flow-rate requirement for a connection from said first edge node to at least one destination edge node;

selecting a candidate core node from among said core nodes through which to route the connection;

computing a proximity index of said first edge node with respect to said candidate core node; and

selecting one of burst-transfer modes according to said proximity index

wherein burst transfer according to a first mode of said burst transfer modes comprises steps of;

forming a data burst according to said total flow-rate requirement;

sending burst transfer requests, each specifying a destination edge node and a burst size, to said core controller; and

receiving from a candidate core controller a schedule for burst transmission.

8. The method of claim 7 wherein burst transfer according to a second mode of said burst transfer modes includes steps of:

sending requests for flow-rate-allocations, each request specifying a destination edge node and a flow-rate requirement; and

receiving from said candidate core node burst-transfer permits each specifying a burst-size limit, a destination, and a corresponding transmission time.

9. The method of claim 8 wherein said proximity index is determined as a function of service-quality criteria and a round-trip propagation delay between said first edge node and said candidate core node, said service quality criteria including burst-transfer delay.

10. The method of claim 9 wherein the proximity index is determined as the ratio of the round-trip propagation delay between said first edge node and said candidate core node to a prescribed delay tolerance.

11. The method of claim 10 wherein, when the proximity index does not exceed unity, said first mode is selected.

12. The method of claim 10 wherein, when the proximity index exceeds unity, said second mode is selected.

13. The method of claim 7 further comprising a step of first edge node time locking to said candidate core node, where time locking ensures that a burst transferred from said first edge node is timed to arrive at said candidate core node at an instant of time specified by said selected core node.

14. The method of claim 13 wherein said forming includes a step of aggregating data packets into said data burst of a size at least equal the sum of lengths of said data packets.

15. The method of claim 13 wherein each edge node aggregates data packets into a burst so that the sum of the length of said data packets does not exceed a specified burst-size limit.

16. The method of claim 10 further comprising computing a storage index based on a storage capacity at said first edge node, a flow-rate allocation and said round-trip propagation delay between said first edge node and said candidate core node.

17. The method of claim 16 including a further step of selecting said first mode if said proximity index is less than unity and said storage index is less than a predetermined threshold having a value less than unity.