Re-routing traffic in a communications network

• US 9,391,874 B2
• Filed: 07/08/2008
• Issued: 07/12/2016
• Est. Priority Date: 05/12/2008
• Status: Expired due to Fees

• Current Assignee: Telefonaktiebolaget LM Ericsson
• Original Assignee: Telefonaktiebolaget LM Ericsson
• Inventors: Corti, Andrea, Fiorone, Raoul, Martinotti, Riccardo
• Primary Examiner(s): Acolatse, Kodzovi
• Application Number:
  US12/992,269
• Publication Number:
  US 20120020207A1
• Time in Patent Office: 2,926 Days
• Field of Search: 370/225, 709/223, 709/239, 709/252
• US Class Current: 1/1
• CPC Class Codes: H04L 45/02 Topology update or discovery
• CPC Class Codes: H04L 45/22 Alternate routing
• CPC Class Codes: H04L 45/28 using route fault recovery
• CPC Class Codes: H04L 45/48 Routing tree calculation
• CPC Class Codes: H04L 45/488 using root node determination

Abstract

Method of re-routing traffic in a communications network (1) in the event of a fault (3) on a path across the network, the method comprising, determining whether a first node (4), located between the fault and a network ingress node (6), is capable of switching traffic to an alternative path which avoids the fault, and if the first node is determined to be not so capable, then determining whether a second node (8), located upstream of the first node, is capable of switching traffic to an alternative path which avoids the fault.

Claims

1. A method of re-routing traffic in a communications network operating in a hierarchical tree structure where the network traffic is sent from an ingress node to a plurality of egress nodes, wherein the ingress node is a root node of the tree structure and the egress nodes are leaf nodes of the tree structure, and wherein in the event of a fault on a path across the network, the method comprising:

determining, by a first node located between the fault and the ingress node, whether the first node is capable of autonomously switching traffic to an alternative sub-tree;

as a consequence of the first node determining that the first node is unable to switch traffic to an alternative sub-tree, sending, by the first node, a fault notification signal upstream to a second node located upstream of the first node, wherein the second node is not the ingress node;

as a consequence of the first node determining that the first node is able to switch traffic to an alternative sub-tree, determining whether the first node is capable of switching traffic from an initial sub-tree to an alternative sub-tree which avoids the fault; and

as a consequence of the first node is determining that the first node is not capable of switching traffic to an alternative sub-tree which avoids the fault, sending, by the first node, a fault notification signal upstream to the second node, and autonomously determining whether the second node is capable of switching traffic to an alternative sub-tree which avoids the fault,

wherein the communications network is configured to provide an E-tree service to at least part of the nodes of the communications network, wherein the ingress node is a node responsible for distribution of the E-tree service within the communications network and the egress nodes are nodes attached to destinations of the E-tree service.

2. The method as claimed in claim 1, wherein at least one further node determines whether the at least one further node is capable of switching the traffic to an alternative sub-tree in the event that the second node determines that the second node is not so capable.

3. The method as claimed in claim 1, wherein the first node neighbors the fault.

4. The method as claimed in claim 1, wherein the first node determines that the fault has occurred.

5. The method as claimed in claim 1, wherein the second node neighbors the first node.

6. The method as claimed in claim 1, wherein if the first node determines that the first node is able to switch traffic to an alternative sub-tree, then the fault notification signal is not sent to the second node.

7. The method of claim 1, wherein switching traffic to an alternative sub-tree which avoids the fault comprises switching traffic destined for a first leaf node to be sent over a first link to a second leaf node, which in turn causes the traffic to be sent over a second link to the first leaf node.

8. The method of claim 1, wherein each of the first and second nodes comprises a sub-root node of a protected sub-tree.

9. The method of claim 1, wherein each of the egress nodes is attached to a corresponding destination of an E-tree service.

10. A communications network operating in a hierarchical tree structure where the network traffic is sent from an ingress node to a plurality of egress nodes, wherein the ingress node is a root node of the tree structure and the egress nodes are leaf nodes of the tree structure, the communications network comprising:

a plurality of nodes which are connected by respective links to form a tree for traffic across the network, the nodes comprising at least one re-routing node configured to;

determine that a fault has occurred between the re-routing node and a network egress node,

determine if the re-routing node is able to autonomously switch traffic onto an alternative sub-tree,

send a fault notification signal upstream to an upstream node located upstream of the re-routing node as a consequence of the re-routing node determining that the re-routing node is unable to switch traffic to an alternative sub-tree, wherein the upstream node is not the ingress node;

determine whether the re-routing node is capable of switching traffic to an alternative sub-tree which avoids the fault as a consequence of the re-routing node determining that the re-routing node is able to switch traffic to an alternative sub-tree;

send a fault notification signal upstream to the upstream node as a consequence of determining that the re-routing node is not capable of switching traffic to an alternative sub-tree which avoids the fault, and

autonomously determine whether the upstream node is capable of switching traffic to an alternative sub-tree which avoids the fault,

wherein the communications network is configured to provide an E-tree service to at least part of the nodes of the communications network, wherein the ingress node is a node responsible for distribution of the E-tree service within the communications network and the egress nodes are nodes attached to destinations of the E-tree service.

11. The communications network as claimed in claim 10, wherein the at least one re-routing node is configured to switch traffic to at least one alternative subtree.

12. The communications network as claimed in claim 10, wherein the at least one re-routing node is connected to at least three links.

13. The communications network as claimed in claim 10, wherein if the at least one re-routing node determines that the re-routing node is able to switch traffic to an alternative sub-tree, then the re-routing node is configured not to send a fault notification signal is not sent to the second node.

14. The communications network as claimed in claim 10, wherein the communications network is a connection-orientated network.

15. The communications network of claim 10, wherein switching traffic to an alternative sub-tree which avoids the fault comprises switching traffic destined for a first leaf node to be sent over a first link to a second leaf node, which in turn causes the traffic to be sent over a second link to the first leaf node.

16. A first node for use in a communications network operating in a hierarchical tree structure where the network traffic is sent from an ingress node to a plurality of egress nodes, wherein the ingress node is a root node of the tree structure and the egress nodes are leaf nodes of the tree structure, the node comprising:

a plurality of hardware interfaces and a processor collectively configured to;

determine that a fault in the network has occurred;

determine whether the first node is capable of causing traffic to be autonomously switched to an alternative sub-tree,

send a fault notification signal upstream to an upstream node located upstream of the first node as a consequence of determining that the first node is unable to switch traffic to an alternative sub-tree, wherein the upstream node is not the ingress node;

determine whether the first node is capable of switching traffic to an alternative sub-tree which avoids the fault as a consequence of determining that the first node is able to switch traffic to an alternative sub-tree;

send a fault notification signal upstream to the upstream node as a consequence of determining that the first node is not capable of switching traffic to an alternative sub-tree which avoids the fault, and

autonomously determine whether the upstream node is capable of switching traffic to an alternative sub-tree which avoids the fault,

wherein the communications network is configured to provide an E-tree service to at least part of the nodes of the communications network, wherein the ingress node is a node responsible for distribution of the E-tree service within the communications network and the egress nodes are nodes attached to destinations of the E-tree service.

17. The node as claimed in claim 16, wherein if the processor determines that the node is capable of causing traffic to be switched to another sub-tree, then the processor is configured to cause the fault notification signal not to be sent.

18. The first node of claim 16, wherein switching traffic to an alternative sub-tree which avoids the fault comprises switching traffic destined for a first leaf node to be sent over a first link to a second leaf node, which in turn causes the traffic to be sent over a second link to the first leaf node.