Abstract:
The present invention provides a method and system for the restoration of an optical mesh network subsequent to the simultaneous failing of a large number of network connections due to a transmission failure. The system and method increase the restoration speed of a large number of failed network connections through connection aggregation. The system and method provide that connection aggregation is the logical bundling of a plurality of network connections across a network span. By enabling the bundling of these individual network connections transported over a particular span or spans, a network operator manages the bundle as if it were one network connection. The method and system provide that other network links support these bundled connections when the network segment that a managed bundle is traversing fails.

Description:
FIELD OF THE INVENTION 
     The present invention relates generally to the fields of optical networking and mesh restoration techniques. More specifically, the present invention relates to a method and system for the restoration of an optical mesh network subsequent to the simultaneous failing of a large number of network connections due to a transmission failure. The method and system increase the restoration speed of a large number of failed network connections through connection aggregation. The method and system provide that connection aggregation is the logical bundling of a plurality of network connections across a network span. By enabling the bundling of these individual network connections transported over a particular span or spans, a network operator manages the bundle as if it were one network connection. The method and system provide that other network links support these bundled connections when the network segment that a managed bundle is traversing fails. 
     BACKGROUND OF THE INVENTION 
     The current models of mesh restoration known in the art do not take into account the effect of a large number of connections simultaneously failing because of a transmission failure. Such an incident, although rare, does cause outages that significantly affect a large number of users. 
     The additional traffic growth and bandwidth demands now experienced on optical cross connects in optical networks has created a need for a control plane enhancement in an optical cross connect that allows for traffic growth to continue while maintaining the network performance to end user customers. 
     Thus, what is needed is a method and system that allow a network operator to identify key segments, also called spans, in an optical mesh network where a large number of connections traverse. By enabling the bundling of these individual network connections transported over a particular span or spans, the network operator manages the bundle as if it were one network connection. Additionally, what is needed is a method and system that allow other network links to support these bundled connections when the network segment that a bundle currently is traversing fails. The present invention provides such a method and system. 
     BRIEF SUMMARY OF THE INVENTION 
     In various exemplary embodiments, the present invention provides a method and a system for restoring optical network connections using span-based connection aggregation. 
     In one exemplary embodiment, the present invention provides a method for restoring network connections using span-based connection aggregation. The method includes identifying a network span between a first node and a second node in a mesh network with a plurality of network nodes, wherein a plurality of individual network connections traverse; logically bundling the plurality of individual network connections in the network span together into a bundle, thereby providing a connection aggregation; managing the connection aggregation, comprised of the plurality of individual network connections, as a single network connection over the network span; maintaining a connection mapping, wherein the connection mapping contains information pertaining to the bundle, but not the individual network connections; defining one or more other network spans in the mesh network as a connection aggregation link to accommodate the bundle in the event of a transmission failure, whereby the bundle is subsequently remapped; and restoring the bundle of network connections over one of the one or more other connection aggregation links when network span that the bundle is traversing fails. When during the restoring the bundle of network connections over one of the one or more other connection aggregation links when the network span that the bundle is traversing fails, no other connection aggregation links are available, the method defaults to standard mesh restoration. The network connection between the first node and the second node has a unique call record. The method further includes one of wholly restoring the bundle of network connections as a bundle or wholly not restoring the bundle of network connections as a bundle. The method includes releasing the bundle of network connections individually when the bundle of network connections cannot be wholly restored as a bundle. The method also includes signaling a connection aggregation in the same manner as signaling a standard network connection. Connection aggregation links are optionally determined by off-line simulation. The method further includes the option of reaggregating the bundle of network connections to the original network span connection aggregation once it has been restored. 
     In another exemplary embodiment, the present invention provides a system for restoring network connections using span-based connection aggregation. The system includes a means for identifying a network span between a first node and a second node in a mesh network with a plurality of network nodes, wherein a plurality of individual network connections traverse; a means for logically bundling the plurality of individual network connections in the network span together into a bundle, thereby providing a connection aggregation; a means for managing the connection aggregation, comprised of the plurality of individual network connections, as a single network connection over the network span; a means for maintaining a connection mapping, wherein the connection mapping contains information pertaining to the bundle, but not the individual network connections; a means for defining one or more other network spans in the mesh network as a connection aggregation link to accommodate the bundle in the event of a transmission failure, whereby the bundle is subsequently remapped; and a means for restoring the bundle of network connections over one of the one or more other connection aggregation links when network span that the bundle is traversing fails. The system also includes a means for defaulting to a standard mesh restoration when during the restoring the bundle of network connections over one of the one or more other connection aggregation links when the network span that the bundle is traversing fails, no other connection aggregation links are available. In this system, the network connection between the first node and the second node has a unique call record. The system further includes a means for wholly restoring the bundle of network connections as a bundle or for wholly not restoring the bundle of network connections as a bundle. The system further includes a means for releasing the bundle of network connections individually when the bundle of network connections cannot be wholly restored as a bundle. The system further includes a means for signaling a connection aggregation in the same manner as signaling a standard network connection. In this system, the connection aggregation links are determined by off-line simulation. The system further includes a means for reaggregating the bundle of network connections to the original network span connection aggregation once it has been restored. 
     In a further exemplary embodiment, the present invention provides an apparatus for restoring network connections using span-based connection aggregation. The apparatus includes logic configured to identify a network span between a first node and a second node in a mesh network with a plurality of network nodes, wherein a plurality of individual network connections traverse; logic configured to logically bundle the plurality of individual network connections in the network span together into a bundle, thereby providing a connection aggregation; logic configured to manage the connection aggregation, comprised of the plurality of individual network connections, as a single network connection over the network span; logic configured to maintain a connection mapping, wherein the connection mapping contains information pertaining to the bundle, but not the individual network connections; logic configured to define one or more other network spans in the mesh network as a connection aggregation link to accommodate the bundle in the event of a transmission failure, whereby the bundle is subsequently remapped; and logic configured to restore the bundle of network connections over one of the one or more other connection aggregation links when network span that the bundle is traversing fails. The apparatus also includes logic for signaling a connection aggregation in the same manner as signaling a standard network connection. The apparatus further includes logic for one of wholly restoring the bundle of network connections as a bundle or wholly not restoring the bundle of network connections as a bundle. The apparatus further includes logic for releasing the bundle of network connections individually when the bundle of network connections cannot be wholly restored as a bundle. 
     Advantageously, the present invention provides a control plane enhancement in an optical cross connect that allows for traffic growth to continue while maintaining the network performance to end user customers. Significantly, this invention provides a faster restoration of a large number of connections that have failed. Thus, network level scalability is greatly enhanced. 
     There has thus been outlined, rather broadly, the features of the present invention in order that the detailed description that follows may be better understood, and in order that the present contribution to the art may be better appreciated. There are additional features of the invention that will be described and which will form the subject matter of the claims. In this respect, before explaining at least one embodiment of the invention in detail, it is to be understood that the invention is not limited in its application to the details of construction and to the arrangements of the components set forth in the following description or illustrated in the drawings. The invention is capable of other embodiments and of being practiced and carried out in various ways. Also, it is to be understood that the phraseology and terminology employed are for the purpose of description and should not be regarded as limiting. 
     As such, those skilled in the art will appreciate that the conception, upon which this disclosure is based, may readily be utilized as a basis for the designing of other structures, methods, and systems for carrying out the several purposes of the present invention. It is important, therefore, that the claims be regarded as including such equivalent constructions insofar as they do not depart from the spirit and scope of the present invention. 
     Additional aspects and advantages of the present invention will be apparent from the following detailed description of exemplary embodiments which are illustrated in the accompanying drawings. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       The present invention is illustrated and described herein with reference to the various drawings, in which like reference numbers denote like method steps and/or system components, respectively, and in which: 
         FIG. 1  is a schematic diagram illustrating an optical mesh network including a plurality of interconnected optical cross connect nodes, and also illustrating, in particular, a plurality of mesh network span links that have been configured as connection aggregation links for the purpose of treating multiple network connections as one across a network span; 
         FIG. 2  is the schematic diagram illustrating the optical mesh network of  FIG. 1 , further illustrating two exemplary transport signal paths and their routes amongst the various optical cross connect nodes included in the optical mesh network, and further illustrating that the exemplary transport signal paths include transport across both standard mesh network links and connection aggregation links of the present invention; 
         FIG. 3  is the schematic diagram illustrating the optical mesh network of  FIG. 1 , further illustrating a single network link failure between two optical cross connect nodes and the subsequent reroute along the connection aggregation links of the two exemplary transport signal paths illustrated in  FIG. 2  as a result of the network link failure; 
         FIG. 4  is the schematic diagram illustrating the optical mesh network of  FIG. 1 , additionally illustrating a second network link failure between two optical cross connect nodes and the subsequent reroute along the connection aggregation links of the two exemplary transport signal paths illustrated in  FIG. 3  as a result of two network link failures; and 
         FIG. 5  is the schematic diagram illustrating the optical mesh network of  FIG. 1 , further illustrating a third network link failure between two optical cross connects and the subsequent reroute of the two exemplary transport signal paths illustrated in  FIG. 4  as a result of three network link failures. 
     
    
    
     DETAILED DESCRIPTION OF THE INVENTION 
     Although the present invention is illustrated and described herein with reference to preferred embodiments and specific examples thereof, it will be readily apparent to those of ordinary skill in the art that other embodiments and examples may perform similar functions and/or achieve like results. All such equivalent embodiments and examples are within the spirit and scope of the present invention and are intended to be covered by the claims that follow. 
     Throughout the specification, the following terms are used. A bundle refers to an aggregated connection bundle. A connection aggregation is one or more network connections that are treated as one connection across a network span. A link is an Optical Signaling &amp; Routing Protocol (OSRP) link. A connection aggregation link is an OSRP link that can support connection aggregation. A connection aggregation protect path is a series of connection aggregation enabled links to be selected from to restore a connection aggregation connection. 
     Connection aggregation within a plurality of mesh network span links  120  ( FIGS. 1-5 ) is used where it is most beneficial to efficient network operation and speedy mesh restoration after transmission failures. For example, connection aggregation needs a high bundling factor. An end-to-end bundle to manage a current network is not suitable to connection aggregation bundling. An objective in implementing span-based connection aggregation and various connection aggregation links  130  ( FIGS. 1-5 ) is to simplify the connection signaling. Another objective in implementing span-based connection aggregation is to provide an enhancement for connection restoration. 
     Referring now to  FIG. 1 , an optical mesh network  100  including a plurality of interconnected optical cross connect nodes  120  is shown. The optical mesh network  100  includes a plurality of interconnected optical cross connect nodes  120 . The optical mesh network  100  further includes a plurality of mesh network span links  120  that have been configured as connection aggregation links  130  for the purpose of treating multiple network connections as one across a network span. 
     Bundle points for connection aggregation links are determined, initialized, and managed by a network user. Optionally, auto-determination of aggregation links is implemented based on predetermined criteria. Auto-determination is, for example, implemented as a Network Management System (NMS) function to specify links  130  between nodes  120 . Links may be used to aggregate existing network connections as well as be used for aggregated connection restoration. 
     Seven connection aggregation links  130 , for example, are initialized in an optical mesh network  100  and are shown in  FIG. 1 . The connection aggregation link  130   cd  includes all network connections between nodes OXC C  120   c  and OXC D  120   d . The connection aggregation link  130   de  includes all network connections between nodes OXC C  120   d  and OXC D  120   e . The connection aggregation link  130   eq  includes all network connections between nodes OXC C  120   e  and OXC D  120   q . The connection aggregation link  130   pq  includes all network connections between nodes OXC C  120   p  and OXC D  120   q . The connection aggregation link  130   dp  includes all network connections between nodes OXC C  120   d  and OXC D  120   p . The connection aggregation link  130   ch  includes all network connections between nodes OXC C  120   c  and OXC D  120   h . The connection aggregation link  130   hp  includes all network connections between nodes OXC C  120   h  and OXC D  120   p.    
     A bundle is, for example, established by the connection aggregation links  130   cd ,  130   de , and  130  eq. OXC C  120   c  and OXC Q  120   q  are thus the end points to this example bundle. The network connections between nodes  120  to be bundled have a special call record reference. Connection mapping is maintained, but no information is stored for an individual connection. Connections are released as a bundle. At the bundle end point nodes, OXC C  120   c  and OXC Q  120   q , for example, the connection is treated as an individual network connection on the incoming and outgoing ends of the bundle. In other words, between OXC C  120   c  and OXC Q  120   q , no individual network connection is used, only reference to the connection aggregation bundle. Such a connection is identified as a separate connection. All existing SNC (Sub Network Connection) behavior is maintained. 
     The network connection on the bundled side, in other words, between OXC C  120   c  and OXC Q  120   q , for example, behaves as a single SNC. A network connection in such a location will not be treated for signaling as a separate network connection. 
     If bundle restoration is not possible, the network connections are released individually. Restoration of a bundle is either a whole restoration or no restoration. There is no bundle fragmenting in span-based connection aggregation. 
     The originating and terminating nodes do not need to know about connection bundling. Connection bundling easily maps into the OTN layer. Bundling can be implemented on OTN trunks. An OTN trunk restoration may replace the connection aggregation. The restoration of trunks can be designated based on network topology. If no restoration is possible at a connection aggregation, standard mesh restoration is triggered. 
     If an optical cross connect node  120  is a transition node for a bundle connection (for example,  120   d  and  120   e  in the bundle from OXC C  120   c  and OXC Q  120   q , discussed above), the node  120   d  and  120   e  shall treat a network connection as a single connection aggregation (i.e.,  130   cd ,  130   de ,  130   eq ,  130   dp ). A network failure will only affect a single connection aggregation and generate one release per connection aggregation. The connection bundling is user-determined. Connections originating at the node can also use an aggregate connection line. Aggregate connections are attempting in a protection scheme prior to individual connection restoration. 
     If an optical cross connect node  120  is an originating node for a bundle connection (for example,  120   c  and  120   q  in the bundle from OXC C  120   c  and OXC Q  120   q , discussed above), the behavior is the same for the bundle and individual network connections, respectfully. Failure affecting a single network connection on the unbundled side (for example, between  120   q  and  120   g ) does not affect the bundle unless all network connections included in the bundle are released. Individual network connections can be restored based on a failure outside of that bundle. Additions of new connections to the bundle are based upon availability. 
     In one embodiment of the present invention, an initial implementation includes the bundling of only STS-1 SNC&#39;s. The bundle size is to be fixed as either STS-3 or STS-12 channelized. Line side support of bundling is only on OC48 and OC192 lines. Different priority connections are not bundled together. Bundle connection behavior is the same as existing SNC. 
     A network with span-based connection aggregation commences with a generic mesh network with some network connections already existing. Connection aggregation links  130  are implemented upon the generic mesh network. Criteria for determining which links are to be configured as connection aggregation links  130  are: the minimum number of like SNC (based on size and priority); span should be between major nodes as defined by a customer; connection aggregation planning generally also includes restoration; a span should have at least one OSRP link active; and a link is designated by a network management system and connection aggregation enabled. 
     A method for restoring network connections using span-based connection aggregation includes identifying a network span between a first node and a second node in a mesh network with a plurality of network nodes, wherein a plurality of individual network connections traverse. Such a link is then identified as connection aggregation enabled. Any of a re-groom, revert, or restoration triggers the creation of a connection aggregation. The plurality of individual network connections in the network span is logically bundled together into a bundle, thereby providing a connection aggregation. The connection aggregation has a set-up message that includes a time slot mapping for the network connections, ENUM of the connection names, size, source and destination, and Conn Record information. Each node across the connection aggregation path terminates the signaling message and modifies it or allows it to simply pass through. The signaling message will be terminated if there is a connection being terminated on that node or if a connection is being added to the bundle. 
     The method for restoring network connections using span-based connection aggregation further includes managing the connection aggregation that includes the plurality of individual network connections, as a single network connection over the network span; maintaining a connection mapping, wherein the connection mapping contains information pertaining to the bundle, but not the individual network connections; defining one or more other network spans in the mesh network as a connection aggregation link to accommodate the bundle in the event of a transmission failure, whereby the bundle is subsequently remapped; and restoring the bundle of network connections over one of the one or more other connection aggregation links when network span that the bundle is traversing fails. 
     Referring now to  FIG. 2 , an optical mesh network  100  including a plurality of interconnected optical cross connect nodes  120  is shown. The optical mesh network  100  also includes two example transport signal paths  140 ,  150  and their respective transport routes amongst the various optical cross connect nodes  120  included in the optical mesh network  100 . The example transport signal paths  140 ,  150  include transport across both standard mesh network links and the connection aggregation links  130  of the present invention. 
     Transport signal path  140  traverses nodes  120   t ,  120   c ,  120   d ,  120   e ,  120   f , and  120   g . Within this sequence of nodes, links  130   cd  and  130   de  are connection aggregation links. Transport signal path  150  traverses nodes  120   a ,  120   b ,  120   c ,  120   d ,  120   e ,  120   q , and  120 . Within this sequence of nodes, links  130   cd ,  130   de , and  130   eq  are connection aggregation links. 
     Referring now to  FIG. 3 , an optical mesh network  100  including a plurality of interconnected optical cross connects  120  is shown. The optical mesh network  100  also includes also includes two example transport signal paths  140 ,  150  and their respective transport routes amongst the various optical cross connect nodes  120  included in the optical mesh network  100 . The example transport signal paths  140 ,  150  include transport across both standard mesh network links and the connection aggregation links  130  of the present invention. Illustrated in the optical mesh network  100  is a single network link failure  110  between two optical cross connect nodes  120   d ,  120   e . Transport signal paths  140 ,  150  are subsequently rerouted along the connection aggregation links  130  as a result of the network link failure. 
     Based on the connection aggregation rerouting, transport signal path  140  traverses nodes  120   t ,  120   c ,  120   d ,  120   p ,  120   q ,  120   e ,  120   f , and  120   g . Within this sequence of nodes, links  130   cd ,  130   dp ,  130   pq , and  130   eq  are connection aggregation links. Based on the connection aggregation rerouting, transport signal path  150  traverses nodes  120   a ,  120   b ,  120   c ,  120   d ,  120   p ,  120   q , and  120 . Within this sequence of nodes, links  130   cd ,  130   dp , and  130   pq  are connection aggregation links. 
     Referring now to  FIG. 4 , an optical mesh network  100  including a plurality of interconnected optical cross connects is shown. The optical mesh network  100  also includes also includes two example transport signal paths  140 ,  150  and their respective transport routes amongst the various optical cross connect nodes  120  included in the optical mesh network  100 . The example transport signal paths  140 ,  150  include transport across both standard mesh network links and the connection aggregation links  130  of the present invention. Illustrated in the optical mesh network  100  are two network link failures  110 ,  112  ( 110  between two optical cross connect nodes  120   d ,  120   e , and  112  between two optical cross connect nodes  120   c ,  120   d ). Transport signal paths  140 ,  150  are subsequently rerouted along the connection aggregation links  130  as a result of the two network link failures  110 ,  112 . 
     Based on the connection aggregation rerouting, transport signal path  140  traverses nodes  120   t ,  120   c ,  120   h ,  120   p ,  120   q ,  120   e ,  120   f , and  120   g . Within this sequence of nodes, links  130   ch ,  130   hp ,  130   pq , and  130   eq  are connection aggregation links. Based on the connection aggregation rerouting, transport signal path  150  traverses nodes  120   a ,  120   b ,  120   c ,  120   h ,  120   p ,  120   q , and  120 . Within this sequence of nodes, links  130   ch ,  130   hp , and  130   pq  are connection aggregation links. 
     Referring now to  FIG. 5 , an optical mesh network  100  including a plurality of interconnected optical cross connects is shown. The optical mesh network  100  also includes also includes two example transport signal paths  140 ,  150  and their respective transport routes amongst the various optical cross connect nodes  120  included in the optical mesh network  100 . The example transport signal paths  140 ,  150  include transport across both standard mesh network links and the connection aggregation links  130  of the present invention. Illustrated in the optical mesh network  100  are three network link failures  110 ,  112 ,  114  ( 110  between two optical cross connect nodes  120   d ,  120   e ;  112  between two optical cross connect nodes  120   c ,  120   d ; and  114  between two optical cross connect nodes  120   b ,  120   c ). Transport signal paths  140 ,  150  are subsequently rerouted along the connection aggregation links  130  as a result of the three network link failures  110 ,  112 ,  114 . 
     Based on the connection aggregation rerouting, transport signal path  140  traverses nodes  120   t ,  120   c ,  120   h ,  120   p ,  120   q , and  120   g . Within this sequence of nodes, links  130   ch ,  130   hp ,  130   pq , and  130   eq  are connection aggregation links. Based on the connection aggregation rerouting, transport signal path  150  traverses nodes  120   a ,  120   b ,  120   h ,  120   p ,  120   q , and  120 . Within this sequence of nodes, links  130   hp  and  130   pq  are connection aggregation links. 
     Although the present invention has been illustrated and described herein with reference to preferred embodiments and specific examples thereof, it will be readily apparent to those of ordinary skill in the art that other embodiments and examples can perform similar functions and/or achieve like results. All such equivalent embodiments and examples are within the spirit and scope of the invention and are intended to be covered by the following claims.