This application is a National stage of International Application No. PCT/EP2010/069804, filed Dec. 15, 2010, which is hereby incorporated by reference.
This invention relates to connection-oriented networks, and to recovery of connections in such a network.
In a connection-oriented network with a Generalised Multi-Protocol Label Switching (GMPLS) control plane it is possible to establish a connection, called a Label Switched Path (LSP), between network nodes. It is desirable that a network is resilient to the failure of a span (link) between nodes, or to a node. GMPLS includes signalling extensions which support recovery. Recovery provides a way of detecting a failure on a working path, signalling the occurrence of the failure, and then transferring traffic from the working path LSP to a recovery path.
It is possible to recover an end-to-end Label Switched Path (LSP). This is called end-to-end recovery and is defined in IETF document [RFC4872] “RSVP-TE Extensions in Support of End-to-End Generalized Multi-Protocol Label Switching (GMPLS) Recovery”. It is also possible to recover a part of an end-to-end LSP. This is called segment recovery and is defined in IETF document [RFC4873] “GMPLS Segment Recovery”.
There are two mechanisms by which a failure in the network can be signalled.
A first aspect of the invention provides a method of operating a node in a connection-oriented network in which there is a working path and a segment recovery path for a segment of the working path. The working path has a branch node at an end of the segment where the segment recovery path connects to the working path. The branch node is not located at an end node of the working path, i.e. the branch node is separate from (offset from) an end node of the working path. The method comprises receiving control plane signalling at an end node of the working path from a node along the working path, indicating that a failure has occurred along the working path. The method further comprises determining, from the received control plane signalling, if the failure has occurred outside the segment of the working path. When it is determined that the failure has occurred outside the segment of the working path, the branch node is notified.
A branch node is notified when a failure has occurred outside the segment of the working path for which it is responsible. This allows the branch node to prevent an unnecessary transfer of traffic to the segment recovery path, or to revert an unnecessary transfer of traffic to the segment recovery path, if the transfer has already taken place in response to data plane failure detection signalling. This avoids unnecessary use of the recovery path resources. This is especially advantageous if the recovery path resources are shared by multiple working paths. It can also prevent undesirable network behaviours, such as repeated transfer of traffic between the working path and the recovery path.
Another aspect of the invention provides a method of operating a branch node in a connection-oriented network in which there is a working path and a segment recovery path for a segment of the working path. The branch node is located at an end of the segment where the segment recovery path connects to the working path. The branch node is not located at an end node of the working path. The method comprises requesting to be notified when a failure occurs outside the segment of the working path.
The network can have a Generalised Multi-Protocol Label Switching (GMPLS) or a Multi-Protocol Label Switching (MPLS) control plane. Data plane connections can be packet based or can use any of a range of other data plane technologies such as wavelength division multiplexed traffic (lambda), or time-division multiplexed (TDM) traffic such as Synchronous Digital Hierarchy (SDH). The data plane can be an MPLS or an MPLS-TP data plane. The recovery scheme can also be applied to other connection-oriented technologies such as connection-oriented Ethernet or Provider Backbone Bridging Traffic Engineering (PBB-TE), IEEE 802.1Qay.
The term “failure detection” is intended to include detection of a fault or failure.
The term “recovery” is intended to include “protection”, which typically means that a recovery path is preconfigured in advance of detecting any fault or failure, as well as “restoration”, which typically means that signalling to configure a recovery path occurs after detection of failure.
Further aspects of the invention provide apparatus for implementing any of the described or claimed methods. An aspect of the invention provides apparatus for use at a node of a connection-oriented network in which there is a working path and a segment recovery path for a segment of the working path. The working path has a branch node at an end of the segment where the segment recovery path connects to the working path. The branch node is not located at an end node of the working path. The apparatus comprises a control plane signalling module arranged to receive an indication from a node along the working path that a failure has occurred along the working path. The control plane signalling module is further arranged to determine, from the indication, if the failure has occurred outside the segment of the working path. When it is determined that the failure has occurred outside the segment of the working path, the control plane signalling module is arranged to notify the branch node.
Another aspect of the invention provides apparatus for use at a branch node of a connection-oriented network in which there is a working path and a segment recovery path for a segment of the working path. The branch node is located at an end of the segment where the segment recovery path connects to the working path. The branch node is not located at an end node of the working path. The apparatus comprises a control plane signalling module arranged to send a request for the branch node to be notified when a failure occurs outside the segment of the working path.
The functionality described here can be implemented in hardware, software executed by a processing apparatus, or by a combination of hardware and software. The processing apparatus can comprise a computer, a processor, a state machine, a logic array or any other suitable processing apparatus. The processing apparatus can be a general-purpose processor which executes software to cause the general-purpose processor to perform the required tasks, or the processing apparatus can be dedicated to perform the required functions. Another aspect of the invention provides machine-readable instructions (software) which, when executed by a processor, perform any of the described methods. The machine-readable instructions may be stored on an electronic memory device, hard disk, optical disk or other machine-readable storage medium or non-transitory medium. The machine-readable instructions can be downloaded to the storage medium via a network connection.
Embodiments of the invention will be described, by way of example only, with reference to the accompanying drawings in which:
At a later time (step 42) a failure occurs in the span between N5 and N7. The working path 10 in
At step 44 nodes N5 and N7 each send control plane signalling 14, indicating the occurrence of failure in span N5-N7, to ingress node N1. Nodes N5 and N7 send the signalling to node N1 because they are nodes of the end-to-end working path 10 and node N1 is the ingress node for the working path 10 and is responsible for activating recovery when a failure occurs in the working path. Ingress node N1 understands that the failure at N5-N7 is outside the segment 11. At step 45 ingress node N1 sends a control plane signalling message to branch node N2. This message informs node N2 that the failure of span N5-N7 is outside the recovery domain of segment. 11. Node N2, upon receiving this message, reverts the segment recovery operation performed at step 43. The message received at step 45 also informs the branch node N2 to lock LSP status until the failure is healed.
At a later time (step 52) a failure occurs in the span between N3 and N4. The working path 10 in
At step 54 nodes N3 and N4 each send control plane signalling 14, indicating the occurrence of failure in span N3-N4, to ingress node N1. Nodes N3 and N4 also each send control plane signalling, indicating the occurrence of failure in span N3-N4, to branch node N2, as previously shown in
In
In the scenarios described above it is assumed that the working path LSP 10 is bi-directional and that data plane failure detection signalling (AIS) 13 propagates in forward and reverse directions from the point of failure. In the bi-directional scenarios, both the ingress node and egress node can have responsibility for activating the recovery path. Similarly, the node at each end of the segment 11 can have responsibility for activating the segment recovery path. For clarity,
Unidirectional Paths
The procedures described above can be applied to uni-directional paths. For a uni-directional LSP in the direction N1-N7, node N5 performs the actions described above for branch node N2 and egress node N7 performs the actions described above for ingress node N1. For a uni-directional LSP in the direction N7-N1, node N2 performs the actions of the branch node described above and node N1 performs the actions of the ingress node described above.
This assumption holds because the branch and merge nodes of a segment can perform the recovery switching procedure and both ends of an LSP (ingress and egress) can trigger recovery or send/request notify messages.
At a later time (step 62) a failure occurs in the span between N1 and N2. The working path 10 in
At step 64 node N1 sends control plane signalling 14, indicating the occurrence of failure in span N1-N2, to node N5 and to egress node N7. Egress node N7 understands that the failure at N1-N2 is outside the segment 11. At step 65 egress node N7 sends a control plane signalling message to node N5. This message informs node N2 that the failure of span N5-N7 is outside the recovery domain of segment 11. Node N5, upon receiving this message, reverts the segment recovery operation performed at step 63. The message received at step 65 also informs node N5 to lock LSP status until the failure is healed.
At a later time (step 72) a failure occurs in the span between N3 and N4. The working path 10 in
At step 74 nodes N3 and N4 each send control plane signalling 14, indicating the occurrence of failure in span N3-N4, to egress node N7. Egress node N7 understands that the failure at N3-N4 is inside the segment 11. Consequently, ingress node N1 allows node N2 to take normal segment recovery operation and no revertive action is necessary.
Signalling Message Format
The behaviour described above can be implemented using RSVP-TE Notify messages. A payload of the message can indicate one of the following:
(i) a branch/merge node wishes to be notified when a failure has occurred outside the recovery domain of the segment. Stated another way, this allows the branch/merge node to request to be notified when it should not reroute traffic to a recovery path.
(ii) an ingress/egress node is notifying a branch/merge node when a failure has occurred outside the recovery domain of the segment. Stated another way, this allows the ingress/egress node to notify the branch/merge node when it should not reroute traffic to a recovery path.
A possible format for the Notify message sent by a branch/merge node [situation (i) above] is as follows:
A possible format for the Notify message sent by an ingress/egress node to a branch/merge node [situation (ii) above] is as follows:
A branch node will send the Notify Message w/NOTIFY_REQUEST obj as soon as the segment recovery LSP has been successfully signalled in the case where the recovery scheme foresees a pre-planned recovery LSP or as soon as the working LSP has been successfully set-up in the case the recovery scheme is full rerouting. A pre-planned recovery is a protection mechanism where the protection path has already been computed or both computed and reserved, Full rerouting is a mechanism where everything is done on-the-fly as soon as a failure is detected (i.e. computation and signalling).
A controller 102 performs monitoring and signalling functions. A data plane fault detection signalling module 103 monitors for faults in the data plane. For example, an ingress node may send Operations, Administration and Management (OAM) packets along the data plane which, for fast protection, are sent at short intervals (typically 3.3 ms). Module may monitor receipt of these packets and raise an alarm if packets are not received in an expected manner (e.g. if three consecutive periodic OAM packets are not received). Module 103 can send signalling, such as an OAM packet carrying an Alarm Indication Signal (AIS), along the data plane to other nodes.
A control plane signalling module 104 receives control plane signalling messages, such as GMPLS RSVP-TE messages, and outputs control plane signalling messages. Advantageously, the control plane signalling messages are RSVP-TE messages of the form previously described. If node 100 is a branch/merge node, module 104 can send a signalling message to an ingress/egress node, indicating that the node wishes to be notified when a failure has occurred outside the recovery domain of the segment. If node 100 is an ingress/egress node, module 104 can send a signalling message to a branch/merge node to notify the branch/merge node when a failure has occurred outside the recovery domain of the segment. If node 100 is an ingress/egress node, module 104 includes decision logic 105. Decision logic 105 determines if, in response to receiving failure detection signalling, the failure is inside or outside a segment of a working path and if there is a need to issue a control plane signalling message to a branch/merge node to prevent or revert recovery.
A store 106 stores data used by the controller 102. This data includes details 107 of LSPs established in the network 5 and a list 108 of branch/merge nodes that have requested to be notified if a failure is internal/external to their segment of a LSP. Data 107 allows the decision logic 105 to determine if a failure is inside a segment or outside a segment where a segment recovery mechanism exists. This allows decision logic 105 to issue a signalling message to a branch/merge node when control plane failure signalling is received.
Shared Recovery
To simplify explanation, the embodiments shown in
Modifications and other embodiments of the disclosed invention will come to mind to one skilled in the art having the benefit of the teachings presented in the foregoing descriptions and the associated drawings. Therefore, it is to be understood that the invention is not to be limited to the specific embodiments disclosed and that modifications and other embodiments are intended to be included within the scope of this disclosure. Although specific terms may be employed herein, they are used in a generic and descriptive sense only and not for purposes of limitation.
Filing Document | Filing Date | Country | Kind | 371c Date |
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PCT/EP2010/069804 | 12/15/2010 | WO | 00 | 10/18/2013 |
Publishing Document | Publishing Date | Country | Kind |
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WO2012/079630 | 6/21/2012 | WO | A |
Number | Name | Date | Kind |
---|---|---|---|
6366556 | Ballintine | Apr 2002 | B1 |
20020129295 | Nishioka | Sep 2002 | A1 |
20030063613 | Carpini | Apr 2003 | A1 |
20050207337 | Oda | Sep 2005 | A1 |
20060274645 | Bradford | Dec 2006 | A1 |
20070183317 | Vasseur | Aug 2007 | A1 |
20070211623 | Nishioka | Sep 2007 | A1 |
20070230358 | Narayanan | Oct 2007 | A1 |
20070280102 | Vasseur | Dec 2007 | A1 |
20080049621 | McGuire et al. | Feb 2008 | A1 |
20090310482 | Asaie et al. | Dec 2009 | A1 |
20090323522 | Deguchi | Dec 2009 | A1 |
20100157813 | Matsuura | Jun 2010 | A1 |
20100238795 | Boutros et al. | Sep 2010 | A1 |
20110038253 | Yabusaki | Feb 2011 | A1 |
20110058501 | Harada | Mar 2011 | A1 |
20110229122 | Castoldi et al. | Sep 2011 | A1 |
20120044800 | Coltro | Feb 2012 | A1 |
20120106948 | Moynihan et al. | May 2012 | A1 |
20120207017 | Ceccarelli et al. | Aug 2012 | A1 |
20130021918 | Fiorone et al. | Jan 2013 | A1 |
Number | Date | Country |
---|---|---|
2010031443 | Mar 2010 | WO |
Entry |
---|
International Search Report, Application No. PCT/EP2010/069804, dated Jul. 5, 2011, 4 pages. |
E. Mannie, “Generalized Multi-Protocol Label Switching (GMPLS) Architecture,” Oct. 2004, 69 pages, Network Working Group, Request for Comments: 3945, The Internet Society. |
J.P. Lang et al., “RSVP-TE Extensions in Support of End-to-End Generalized Multi-Protocol Label Switching (GMPLS) Recovery,” May 2007, 47 pages, Network Working Group, Request for Comments: 4872, The IETF Trust. |
L. Berger et al., “GMPLS Segment Recovery,” May 2007, 25 pages, Network Working Group, Request for Comments: 4873, The IETF Trust. |
Written Opinion, Application No. PCT/EP2010/069804, published Jun. 15, 2013, 6 pages. |
International Preliminary Report on Patentability, Application No. PCT/EP2010/069804, dated Jun. 27, 2013, 8 pages. |
IEEE Std 802.1Qay-2009, IEEE Standard for Local and Metropolitan Area Networks—Virtual Bridged Local Area Networks, Amendment 10: Provider Backbone Bridge Traffic Engineering, The Institute of Electrical and Electronics Engineers, Inc., Aug. 5, 2009, 145 pages. |
Number | Date | Country | |
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20140029416 A1 | Jan 2014 | US |