Design of a meta-mesh of chain sub-networks

• US 20020071392A1
• Filed: 10/19/2001
• Published: 06/13/2002
• Est. Priority Date: 10/25/2000
• Status: Active Grant

• Current Assignee: Telecommunications Research Laboratories
• Original Assignee: Telecommunications Research Laboratories
• Inventors: Grover, Wayne D., Doucette, John
• Granted Patent: US 7,719,962 B2
• Time in Patent Office: Days
• US Class Current: 370/241
• CPC Class Codes: H04J 14/0206 Express channels arrangements
• CPC Class Codes: H04J 14/0213 Groups of channels or wave bands arrangements
• CPC Class Codes: H04J 14/0217 Multi-degree architectures, e.g. having a connection degree greater than two
• CPC Class Codes: H04J 14/0227 Operation, administration, maintenance or provisioning [OAMP] of WDM networks, e.g. media access, routing or wavelength allocation
• CPC Class Codes: H04J 14/0241 Wavelength allocation for communications one-to-one, e.g. unicasting wavelengths
• CPC Class Codes: H04J 14/0284 WDM mesh architectures
• CPC Class Codes: H04J 14/0291 Shared protection at the optical multiplex section (1:1, n:m)
• CPC Class Codes: H04J 14/0294 Dedicated protection at the optical channel (1+1)
• CPC Class Codes: H04J 14/0295 Shared protection at the optical channel (1:1, n:m)
• CPC Class Codes: H04L 45/04 Interdomain routing, e.g. hierarchical routing
• CPC Class Codes: H04Q 11/0062 Network aspects
• CPC Class Codes: H04Q 2011/0081 Fault tolerance; Redundancy; Recovery; Reconfigurability
• CPC Class Codes: H04Q 2011/0098 Mesh

Abstract

A method to increase the capacity efficiency of span-restorable mesh networking on sparse facility graphs. The new approach views the network as a “meta-mesh of chain sub-networks”. This makes the prospect of WDM mesh networking more economically viable than with previous mesh-based design where the average nodal degree is low. The meta-mesh graph is a homeomorphism of the complete network in which edges are either direct spans or chains of degree-2 nodes. The main advantage is that loop-back type spare capacity is provided only for the working demands that originate or terminate in a chain, not for the entire flow that crosses chains. The latter “express” flows are entirely mesh-protected within the meta-mesh graph which is of higher average degree and hence efficiency for mesh restoration, than the network as a whole. Nodal equipment savings also arise from the grooming of express lightpaths onto the logical chain-bypass span. Only the meta-mesh nodes need optical cross-connect functionality. Other sites use OADMs and/or glassthroughs. The resultant designs comprise a special class of restorable network that is intermediate between pure span restoration and path restoration. Most of the efficiency of path restoration is achieved, but with a span restoration mechanism which is more localized and potentially faster and simpler than path restoration. The concept lends itself to implementation with OADMs having a passive waveband pass-through feature to support the logical chain bypass spans for express lightpaths.

Claims

1. A method of restoring a telecommunications network, in which the network includes plural nodes terminating plural spans, the plural nodes including nodes of degree two and nodes of at least degree three, the method comprising the steps of:

detecting a span failure between a first node of at least degree three and a second node of at least degree three, the first node and second node being connected through a chain of nodes including at least a third node;

looping back local flows from the third node to one of the first node and second node; and

routing express flows flowing through the first node and second node onto spans with spare capacity without looping back all express flows through nodes in the chain of nodes.

2. The method of claim 1 in which the telecommunications network is configured with cross-connect equipment at nodes having degree three or more and add-drop multiplexing equipment at nodes having degree two.

5. A method of planning telecommunication network capacity to accommodate span failures, the method comprising the steps of:

A) calculating required spare capacity in the telecommunications network taking into account the restoration of express flows according to the method of claim 1 or claim 2; and

B) allocating spare capacity in the telecommunications network according to the calculation of step A.

6. The method of claim 5 in which the telecommunications network is configured with cross-connect equipment at nodes having degree three or more and add-drop multiplexing equipment at nodes having degree two.

7. A telecommunications network having spare capacity distributed according to the method of claim 5.

3. A method of restoring a telecommunications network, in which the network includes plural nodes terminating plural spans, the plural nodes including nodes of degree two and nodes of at least degree three, the method comprising the steps of:

detecting a span failure between a first node of at least degree three and a second node of at least degree three, the first node and second node being connected through a chain of nodes including at least a third node of degree two;

looping back local flows from the third node to one of the first node and second node; and

routing express flows flowing through the first node and second node onto spans with spare capacity without looping back all express flows through nodes in the chain of nodes.

4. The method of claim 3 in which the telecommunications network is configured with cross-connect equipment at nodes having degree three or more and add-drop multiplexing equipment at nodes having degree two.

8. A method of distributing spare capacity in a telecommunications network containing nodes, the nodes including at least degree two and degree three nodes, and the telecommunications network containing spans connecting the nodes, the method comprising the steps of:

characterizing, in a computer, the telecommunications network as a network containing nodes of degree three or more; and

assigning spare capacity in the telecommunications network to minimize total cost of the network capacity subject to the constraints that (1) all single span failures are restorable, (2) spare capacity exists to support all restoration flows, (3) all working demands are routed in the telecommunications network; and

(4) the working capacity of the telecommunications network is adequate to route working flows.

9. The method of claim 8 in which characterizing the telecommunications network as a network containing nodes of degree three or more comprises assigning, in a computer, a logical bypass span to each pair of degree three nodes that are connected through a chain of one or more degree two nodes.

10. A telecommunications network having spare capacity distributed according to the method of claim 8.

11. A telecommunications network, comprising:

plural nodes of degree three interconnected by chains of nodes of degree two;

the nodes of degree three incorporating cross-connect equipment; and

the nodes of degree two incorporating add-drop multiplexing equipment.