Patent Publication Number: US-2022224640-A1

Title: Apparatuses and methods for restoration of a label-switched path in a network

Description:
CROSS-REFERENCE TO RELATED APPLICATIONS 
     The present application claims priority from International Patent Application No PCT/CN2020/078902, filed on Mar. 20, 2020, the disclosure of which is incorporated by reference herein in its entirety. 
    
    
     FIELD OF THE INVENTION 
     The present invention generally relates to the field of communications and, in particular, to restoration of a label-switched path in a network. 
     BACKGROUND 
     In a telecommunication network, nodes and links form a network topology, and the links provide interconnections between the nodes. An automatically switched optical network (ASON) has a dynamic policy-driven control and an automatic management of ASON&#39;s resources and connections. 
     A logical architecture of an ASON may be divided into three planes: a data plane (which may also be referred to as a “transport plane”), a control plane, and a management plane. The data plane has switches responsible for transporting user data via connections. These switches are connected to each other via the links. 
     The control plane is responsible for the resource and connection management within ASON. The control plane usually has a series of optical connection controllers which may provide various functions, such as network topology discovery, signaling, routing, connection set-up and tear-down, connection protection and restoration, traffic engineering, and wavelength assignment. 
     The management plane is responsible for managing the control plane. The management plane manages configurations of the control plane resources, routing areas, transport resources in the control plane and the policies. The management plane may also provide fault management, performance management, as well as accounting and security management functions. 
     A multi-protocol label switching (MPLS) routing technique in a network directs the data from one node to another node by using path labels. The path labels identify paths between two distant nodes, rather than destination points of the data. 
     A generalized multi-protocol label switching (GMPLS) routing technique is based on the MPLS routing technique. The GMPLS technique supports, for example, Layer-2 Switch Capable (L2SC) interface, Time-Division Multiplex (TDM) interface, Lambda Switch Capable (LSC) interface, and Fiber Switch Capable (FSC) interface. In order to support a recovery of a failed network, GMPLS recovery technique uses control plane mechanisms, such as, for example, signaling, routing, and link management mechanisms. 
     A label-switched path (LSP) may be defined as a predetermined path that a packet follows when it is transmitted through an ASON network with GMPLS. In the event of a network failure, all affected LSPs and the data plane need to be restored as soon as possible. Currently used restoration techniques, such as, for example, a Resource ReSerVation Protocol-Traffic Engineering (RSVP-TE), are time- and resource-consuming. 
     SUMMARY 
     An object of the present disclosure is to provide systems, methods and apparatuses, such as nodes, systems for improved restoration of label-switched path (LSP) in networks. In particular, the systems, methods and apparatuses may be implemented in an automatically switched optical network (ASON) with generalized multi-protocol label switching (GMPLS). 
     In accordance with this objective, an aspect of the present disclosure provides a node comprising: a non-transitory storage medium storing instructions; and a processor configured to execute the instructions and, when executing the instructions, configured to: receive a label-switched path (LSP) failure notification; generate a fast-restoration (FR) message comprising: a plurality of forwarding instruction objects (FIOs) having forwarding instructions related to each node of a message forwarding path; and a plurality of label-switched path objects (LSPOs) having a restoration label-switched path (LSP) data for each node of a protection detour path, nodes of the message forwarding path comprising nodes of the protection detour path. The processor is further configured to transmit the FR message to another node of the message forwarding path. 
     In at least one embodiment, the processor is further configured to, prior to generating the FR message, determine each node of the protection detour path and determine each node of the message forwarding path. 
     The processor may be further configured to, prior to generating the FR message: generate the plurality of FIOs; and generate a plurality of LSPOs. 
     The node may further comprise a forwarding instruction database comprising forwarding data; an LSP database comprising restoration LSP data. The processor, when executing the instructions, may be further configured to: access the forwarding instruction database to generate the plurality of FIOs; and access the LSP database to generate the plurality of LSPOs. 
     In accordance with another aspect of the present disclosure, there is provided a node comprising: a non-transitory storage medium storing instructions and a processor configured to execute the instructions and, when executing the instructions, configured to: receive a fast-restoration (FR) message, the FR message comprising: a plurality of FIOs having a first FIO, the first FIO having forwarding instructions of the FR message from the node to another node of a message forwarding path; and a plurality of LSPOs, each LSPO having a restoration LSP data for each node of a protection detour path, nodes of the message forwarding path comprising nodes of the protection detour path. In at least one embodiment, the processor is further configured to generate a modified FR message based on the FR message; and transmit the modified FR message to another node of the message forwarding path based on the first FIO located in the FR message. 
     The processor may be further configured to, after transmitting the modified FR message to another node of the message forwarding path: process the FR message to restore LSPs related to the node based on the restoration LSP data in the plurality of LSPOs. 
     The processor may be further configured to, prior to generating the modified FR message: copy the FR message to a node message storage and, prior to processing the FR message, retrieve the FR message from the node message storage. 
     The processor may be further configured to generate the modified FR message by removing from the FR message the first FIO related to the node. The modified FR message may comprise a modified plurality of FIOs, the modified plurality of FIOs excluding the first FIO. 
     In accordance with another aspect of the present disclosure, there is provided a method comprising: receiving a LSP failure notification indicating a failure in a network; generating, by a node of the network, a FR message comprising: a plurality of FIOs having forwarding instructions for the FR message for each node of a message forwarding path; a plurality of LSPOs having a restoration LSP data for each node of a protection detour path, nodes of the message forwarding path comprising nodes of the protection detour path. In at least one embodiment, the method further comprises transmitting the FR message to a second computing node of the message forwarding path. 
     In at least one embodiment, the method further comprises, prior to generating the FR message, determining each node of a protection detour path and determining each node of a message forwarding path. 
     In accordance with another aspect of the present disclosure, there is provided another method comprising: receiving the FR message by a node of a network, the FR message comprising: a plurality of FIOs having a first FIO, the first FIO having forwarding instructions for the FR message from the node to another node of a message forwarding path; a plurality of LSPOs each LSPO having a restoration LSP data for each node of a protection detour path, nodes of the message forwarding path comprising nodes of the protection detour path. In at least one embodiment, the method further comprises generating a modified FR message based on the FR message; and transmitting the modified FR message to another node of the message forwarding path based on a first FIO located in the FR message. 
     In at least one embodiment, the method further comprises, after transmitting the modified FR message to another node of the message forwarding path: processing the FR message to restore LSPs related to the node based on the restoration LSP data in the plurality of LSPOs. 
     In at least one embodiment, processing of the FR message to restore the LSPs on the node further may comprise establishing at least one cross-connect on a data plane of the node. The method may further comprise copying the FR message to the node message storage prior to generating the modified FR message. Generating the modified FR message may further comprise removing, from the FR message, the first FIO related to the node. 
     In at least one embodiment, each FIO of the plurality of FIOs of the FR message comprises an action flag indicating whether the data of FR message should be processed by each node of the message forwarding path. 
     In at least one embodiment, the FR message may further comprise: a header comprising a FR message length value, a FR message type identifier, and a FR message version identifier. The FR message may further comprise a value of a number of FIOs of the plurality of FIOs; and a value of a number of LSPOs of the plurality of LSPOs. 
     The number of FIOs in the FR message may be equal to a number of the nodes in the message forwarding path. The number of LSPOs may be equal to a number of LSPs to be restored at each node of the protection detour path. 
     Each FIO of the plurality of FIOs of the FR message may comprise: a FIO length value, a FIO type identifier, a forwarding label, and an action flag. Each FIO may further comprise an action flag indicating whether the FR message should be processed by the node. Each LSPO of the plurality of LSPOs of the FR message may comprise: an LSPO length value, an LSPO type identifier, and a restoration LSP data. 
     The node and the other nodes of the protection detour path may operate an optical network, and the number of LSPOs in the FR message may be equal to a number of optical channels of the optical network. 
     Implementations of the present disclosure each have at least one of the above-mentioned objects and/or aspects, but do not necessarily have all of them. It should be understood that some aspects of the present disclosure that have resulted from attempting to attain the above-mentioned object may not satisfy this object and/or may satisfy other objects not specifically recited herein. 
     Additional and/or alternative features, aspects and advantages of implementations of the present disclosure will become apparent from the following description, the accompanying drawings and the appended claims. 
    
    
     
       BRIEF DESCRIPTION OF THE FIGURES 
       Further features and advantages of the present disclosure will become apparent from the following detailed description, taken in combination with the appended drawings, in which: 
         FIG. 1  depicts a portion of a telecommunication network having several nodes which are suitable to implement methods as described herein, in accordance with various embodiment of the present technology; 
         FIG. 2  depicts one node of  FIG. 1 , in accordance with various embodiment of the present technology; 
         FIG. 3  depicts a non-limiting example of a fast-restoration (FR) message, in accordance with various embodiments of the present disclosure; 
         FIG. 4  depicts a non-limiting example of a forwarding instruction object (FIO) of the FR message of  FIG. 3 , in accordance with various embodiments of the present disclosure; 
         FIG. 5  depicts a non-limiting example of a label-switched path object (LSPO) of the FR message of  FIG. 3 , in accordance with various embodiments of the present disclosure; 
         FIG. 6  depicts the FR message before being received by a node and a modified FR message is generated by the node and is transmitted to another node, in accordance with various embodiments of the present disclosure; 
         FIG. 7  depicts a method for network restoration, in accordance with various embodiments of the present disclosure; 
         FIG. 8  depicts another method for network restoration, in accordance with various embodiments of the present disclosure; 
         FIG. 9  depicts a non-limiting example of an optical network, in accordance with various embodiments of the present disclosure; 
         FIG. 10  depicts two non-limiting examples of LSPO, in accordance with various embodiments of the present disclosure; 
         FIG. 11  depicts two alternative non-limiting examples of LSPO, in accordance with various embodiments of the present disclosure; 
         FIG. 12  depicts the optical network of  FIG. 9  showing direct control channels between three nodes, in accordance with various embodiments of the present disclosure; 
         FIG. 13  depicts an example of FIO of the FR message for one node, in accordance with various embodiments of the present disclosure; 
         FIG. 14  depicts the optical network of  FIG. 9  without direct control channels between two nodes, in accordance with various embodiments of the present disclosure; 
         FIG. 15A  depicts a non-limiting example of a first FR message generated by one node of the optical network of  FIG. 9 , in accordance with various embodiments of the present disclosure; 
         FIG. 15B  depicts a non-limiting example of a second FR message generated by another node of the optical network of  FIG. 9 , in accordance with various embodiments of the present disclosure; 
         FIG. 15C  depicts a non-limiting example of a third FR message generated by yet another node of the optical network of  FIG. 9 , in accordance with various embodiments of the present disclosure; and 
         FIG. 15D  depicts a non-limiting example of a fourth FR message generated by yet another node of the optical network of  FIG. 9 , in accordance with various embodiments of the present disclosure. 
     
    
    
     It is to be understood that throughout the appended drawings and corresponding descriptions, like features are identified by like reference characters. Furthermore, it is also to be understood that the drawings and ensuing descriptions are intended for illustrative purposes only and that such disclosures do not provide a limitation on the scope of the claims. 
     DETAILED DESCRIPTION 
     The instant disclosure is directed to address at least some of the deficiencies of the current technology. In particular, the instant disclosure describes apparatuses and methods for an improved restoration of a label-switched path (LSP) in an automatically switched optical network (ASON) with generalized multi-protocol label switching (GMPLS). The ASON with GMPLS is also referred to herein as a “GMPLS network”. 
     As referred to herein, the term “node” refers to a node in a GMPLS network. The node is a hardware element that may be configured to operate by executable instructions, as discussed further below. The node may be, for example, a layer-2 switch, an optical transport networking (OTN) switch or a lambda switch. In the GMPLS network, nodes are connected to each other by links. As referred to herein, the term “link” refers to a hardware that provides connections between the nodes. As referred to herein, the term “number of hops” refers to a number of intermediate devices (such as nodes) through which data passes when it is being transmitted between two nodes of the network. 
     An LSP is a predetermined path that a data packet follows when transmitted through a GMPLS network. The LSP may be also defined as a sequence of nodes (such as, for example, label switch routers) that transmit a packet of data within a GMPLS network. As used herein, the term “working LSP” refers to an LSP that is used during regular operation of GMPLS network. 
     A failure of one or more nodes and/or one or more links of a network (which may have many causes) may lead to a network failure. The network failure may affect one or more LSPs and therefore may interrupt or otherwise damage transmission of data between at least two nodes of the network. 
     In order to restore data transmission in the data plane in such failed network, all LSPs that were affected by the network failure need to be restored. Restoring LSPs comprises restoring cross-connections on the data plane of the nodes that were affected by the network failure. Generally, it is desirable that the restoration be accomplished promptly and efficiently. 
     The term “protection LSP” refers to an LSP that is used to transport user traffic in the event of the network failure and when the working LSP is not available. Resource ReSerVation Protocol-Traffic Engineering (RSVP-TE) is a most popular GMPLS signaling protocol. RSVP-TE typically uses a PATH message and an RESV message for the protection LSP setup. However, use of RSVP-TE messages for LSP restoration has limitations. 
     GMPLS network uses an internet protocol (IP)to communicate between different components in the control plane. In the event of a network failure, it may take several seconds for an IP-based signaling communications network to reach a state of routing convergence. The state of routing convergence as referred to herein is a state of nodes of a network where all nodes of the network have the same information about a topology of the network. Until the nodes of the network have the same information about the network&#39;s topology, RSVP-TE messages can be lost, because RSVP-TE messages do not specify how to forward the message from one node to another. If a RSVP-TE message is lost, the network continues to be unrestored until the next RSVP-TE message arrives to all node(s) to complete restoration of the LSP. 
     Furthermore, in order to restore LSPs in the failed network, one RSVP-TE message needs to be transmitted for each protection LSP setup. Therefore, in order to restore transmission of data in N optical channels between one source node and one destination node, N protection LSPs need to be restored. Such N protection LSPs would require N RSVP-TE messages. 
     Moreover, an overall time delay needed to restore all LSPs affected by network failure using RSVP-TE messages may be too long for some applications. Such overall time delay depends on a sum of the overall message processing time and the overall message transmission time of the RSVP-TE messages between the source node and the destination node. 
     The overall message transmission time for 80 RSVP-TE PATH messages with 20 hops over 5 megabits per second (Mbits/s)control channel may be about 3.8 seconds from the source node to the destination node of the protection LSP. In addition, each RSVP-TE PATH message needs to be processed after it has been received by each node of the protection LSP. Each node processes the RSVP-TE PATH message, validates a resource and updates the RSVP-TE PATH “Soft State”. For example, a processing time of RSVP-TE PATH message at one node may be about 15 milliseconds (ms). RSVP-TE PATH message may be transmitted to another node only after the RSVP-TE PATH message has been processed by the current node, therefore delaying the restoration of LSPs. 
     In order to improve consumer and provider experiences, network operators are striving to reduce the overall time delay needed to restore the LSPs that have been affected by a network failure. 
     The apparatuses, systems and methods as described herein permit reducing the time of restoration of LSPs affected by a network failure. The nodes as described herein are configured to generate and process a fast-restoration (FR) message. 
     The FR message as described herein is forwarded with explicit forwarding instructions via a message forwarding path. The explicit forwarding instructions ensure delivery of the FR message to each node along the message forwarding path. 
     A protection detour path may comprise one or more protection LSPs which include the same network nodes. In other words, the protection detour path is a path through the GMPLS network which comprises a sequence of nodes that need to receive and process the FR message in order to restore LSPs. The message forwarding path may be different from the protection detour path. The message forwarding path comprises all nodes of the protection detour path and may also comprise one or more other nodes. 
     One FR message may comprise data that may be used for the restoration of many network LSPs. In other words, a single FR message may comprise data related to many protection LSPs, when such protection LSPs include the same network nodes. 
     The structure of the FR message as described herein permits avoiding a loss of the FR message even in the presence of slow routing convergence. Due to efficient transmission of the FR message by nodes and due to processing of the FR message at the nodes, which is subsequent or simultaneous to the transmission of the FR message, restoration of data transmission in the data plane of the network may be accelerated. 
     After successful restoration of LSPs by using the FR message as described herein, the control plane and the data plane may be synchronized in order to restore the whole network. Such synchronization of the control plane and the data plane may be performed, for example, by the conventional RSVP-TE PATH message. 
       FIG. 1  depicts a portion  100  of a telecommunication network having several nodes which are suitable to implement methods as described herein, in accordance with various embodiment of the present technology. 
     Each one of nodes  111 ,  112 ,  113 ,  114 ,  115  comprises a processor  121  and a non-transitory storage medium  122  storing instructions executable by the processor  121 . 
     A protection detour path  101  comprises nodes  111 ,  112 ,  113 ,  115 . Node  111  may be also referred to as a “source node”  111  of protection detour path  101 . Node  115  may be also referred to as a “destination node” of the protection detour path  101 . The source node  111  is configured to generate a first FR message  300 . In other words, when the instructions are executed by the processor  121  of source node  111 , the processor  121  of source node  111  is configured to generate first FR message  300 . 
     The protection detour path  101  is defined in the data plane. The FR message is transmitted through the control plane of the network. In some embodiments, nodes of the control plane may be different from the data plane. A message forwarding path  103 , located in the control plane, comprises all nodes of the protection detour path  101  and may also comprise additional nodes. 
     In  FIG. 1 , message forwarding path  103 , located in the control plane, comprises nodes  111 ,  112 ,  113 ,  114 , and  115 . In other words, the message forwarding path  103  comprises all nodes of protection detour path  101 , as well as an intermediate node  114  (which may be also referred to as “control plane node”  114 ). The message forwarding path  103  may be also referred to as a “control plane path”  103 . 
     The source node  111  generates a FR message  300  (also referred to herein as a “first message”  300 ). Node  112  receives first FR message  300  and generates a second FR message  602  based on the first FR message  300  as described herein below. Node  113  is configured to generate a third FR message  603  based on the second FR message  602  as described herein below. Node  113  transmits third FR message  603  to node  114 . 
     Control plane node  114  receives and forwards the third FR message  603  without processing it, to node  115 . The control plane node  114  may generate a fourth FR message  604  based on third FR message  603  and then transmit the fourth FR message  604  to node  115 . 
     Nodes  112 ,  113 , and destination node  115  of protection detour path  101  are configured to process, as described herein, FR messages  300  and  602 ,  604 , respectively. In other words, processors  121  of the nodes  112 ,  113 ,  115  of the protection detour path  101  are configured to process FR messages  300 ,  602 ,  604 , respectively, as described below. 
       FIG. 2  depicts source node  111  of  FIG. 1 , in accordance with various embodiment of the present technology. In addition to processor  121  and non-transitory storage medium  122 , source node  111  may also comprise a forwarding instruction database  125  and an LSP database  126 . The forwarding instruction database  125  may comprise message forwarding data, such as forwarding labels. The forwarding label may be, for example, a global label or a local label known to the node at which the label is meant to be processed. The LSP database  126  comprises restoration LSP data, such as, for example, a global path label. 
     In the event of the network failure, source node  111  receives a notice, such as, for example, a LSP failure notification  201 . After source node  111  receives the LSP failure notification  201 , source node  111  generates FR message  300 . 
       FIG. 3  depicts a non-limiting example of FR message  300 , in accordance with various embodiments of the present disclosure. The FR message  300  comprises a FR message header  301 , a list of forwarding instruction objects (FIOs)  320 , and a list of label-switched path objects (LSPOs)  330 . In some embodiments, the list of FIOs  320  may have one element. In some embodiments, the list of LSPOs  330  may have one element. 
     The FR message header  301  comprises: a FR message length value  302 , a FR message type identifier  304 , a FR message version identifier  306 . In some embodiments, FR message length value  302  may occupy two bytes of data. FR message type identifier  304  may indicate a message type. The FR message type identifier  304  may be, for example, “FAST RESTORATION”. Such message type identifier  304  may indicate to the nodes of the protection detour path  101  that FP message  300  needs to be processed by the node&#39;s processor  121  as the FR message as described herein. In some embodiments, FR message length value  301  may precede FR message type identifier  304 . The FR message type identifier  304  may occupy 1 byte. 
     In some embodiments, FR message  300  may also comprise a number (n) of forwarding instruction objects (FIOs)  321 , and a number (m) of restoration LSP objects  331 . 
     The number (n) of FIOs  321  may be defined by the number of nodes FR message  300  needs to be forwarded from when transmitted via message forwarding path  103 , in order to set up the protection detour path  101  and restore LSPs of the network. In other words, the number n of FIO may correspond to a number of nodes in the message forwarding path  103 . 
       FIG. 4  depicts a non-limiting example of the forwarding instruction object (FIO)  400  of the first FR message  300 , in accordance with various embodiments of the present disclosure. The FIO  400  comprises data with forwarding details of the FR message  300  by the nodes in protection detour path  101 . 
     Referring also to  FIGS. 1-3 , a list  320  of FIOs  400  allows the FR message to be forwarded via the nodes of message forwarding path  103  specified in the FR message  300 . “Forwarding of the FR message” or “propagation of the FR message” as referred to herein comprises forwarding of the first, second, third and fourth FR messages  300 ,  602 ,  603 ,  604 , respectively, via the message forwarding path  103 . 
     The protection detour path  101  is specified in FIO  400  by labels. Due to the FIOs, the data comprised in the FR message  300  may be guaranteed to be delivered to and received by each node on the protection detour path  101 . Without forwarding instructions, the FR message would be lost because of slow routing convergence caused by network failures and topology changes. 
     Each FIO  400  comprises a FIO length value  410 , a FIO type identifier  412 , and a forwarding label  414 . In some embodiments, FIO  400  may also have an action flag  416 . 
     The FIO length value  410  indicates a combined length of the information of the FIO  400 . The FIO length value  410  may occupy, for example, two bytes. 
     The FIO type identifier  412  may be, for example, “FORWARDING INSTRUCTION”. The FIO type identifier  412  may occupy, for example, 1 byte. 
     The forwarding label  414  may be, for example, a global label or a local label known to the node that executes the forwarding instructions. The forwarding label  414  may occupy, for example, y bytes, where y is an integer. For example, y may be equal to 8 bytes, including 4 bytes of a node identifier (ID) and 4 bytes of a link ID. 
     An action flag  416  may indicate an action that a current node needs to perform when it receives FR message  300 . For example, the action flag may indicate whether the respective FR message needs to be processed at the current node. For example, an action flag specific to the current node may be a string “Forward”. The string “Forward” may indicate that the received FR message needs to be forwarded by the current node to another node without processing. Alternatively, the action flag specific to the current node may be another string “Copy and Forward”. The string “Copy and Forward” may indicate, for example, that the respective FR message received by the current node needs to be copied by the current node, then forwarded to another node, and then processed by the current node, after the FR message  300  has been forwarded to the another node. The action flag may occupy, for example, 1 byte. 
     In some embodiments, FIO  400  may have no action flag  416 . For example, a default action may be “Copy and Forward” and it may be known to the node that reads FIO  400 . The node that reads FIO  400  may be pre-configured to copy and forward the message if FIO  400  does not have any action flag  416 . 
     As it is depicted in  FIG. 4 , each FIO  400  may occupy (4+y) bytes, where y is the number of bytes of the forwarding label  414 . Referring also to  FIG. 3 , FR message  300  comprises FIOs  400  for each node on the protection detour path  101 . The list  320  of n FIOs may thus occupy n(4+y) bytes in the FR message  300 . 
     In addition to FIOs  400 , FR message  300  also comprises a list  330  of LSPOs as described herein below. 
       FIG. 5  depicts a non-limiting example of a LSPO  500 , in accordance with various embodiments of the present disclosure. LSPO may also be referred to as “LSP-data object”. 
     One LSPO  500  comprises a restoration LSP data for one of nodes  112 ,  113 ,  115  on the protection detour path  101 . Referring also to  FIG. 3 , a single FR message  300  comprises a plurality of protection LSP data objects, such as, for example, LSP global labels. 
     Due to transmission of multiple LSPOs through one protection detour path  101 , protection detour LSPs may be restored using a single FR message  300  signaling for the LSPs which have the same node path. Thus one FR message  300  may be used to set up multiple protection detour LSPs if they are located on one protection detour path  101 . 
     The LSPO  500  comprises an LSPO length value  510 , an LSPO type identifier  512 , and a restoration LSP data  514 . 
     The LSPO length value  510  indicates a combined length of the information of the LSPO. The LSPO length value  510  may occupy, for example, two bytes. The LSPO type identifier  512  may be, for example, “LSP-DATA” type. The LSPO type identifier  512  may occupy, for example, one byte. 
     The restoration LSP data  514  may be, for example, a global path label. The restoration LSP data may occupy, for example, x bytes, where x is an integer. For example, the global path label may occupy 4 bytes. In this non-limiting example, each LSPO  500  may occupy 3+x bytes. For example, a global path label may occupy 6 bytes, including 4 bytes of a node ID and 2 bytes of a local LSP index. 
     Referring now to  FIG. 3 , FR message  300  may comprise a value of number m of restoration LSPs  331 , where m is an integer. The number of restoration LSPs  331  may depend on the number of restoration paths (in other terms, protection detour paths). For example, there may be 80 restoration paths for 80 dense wavelength division multiplexing (DWDM) optical channels. For example, the value of number m of restoration LSPs may occupy 1 byte. 
     The list  330  of LSPOs may follow the value of number m of restoration LSPs in the FR message  300 . For example, for an optical network, a number of LSPOs in the FR message may be equal to a number of optical channels of the optical network. 
       FIG. 6  depicts FR message  300  (also referred to herein as the “first FR message  300 ”) before being received by node  112  and a modified FR message  602  (also referred to herein as the “second FR message  602 ”) that has been generated by node  112  based on FR message  300 , in accordance with various embodiments of the present disclosure. 
     In  FIG. 6 , list of FIOs  320  of first FR message  300  comprises a first FIO  401 , a second FIO  402 , and a third FIO  403 . Referring also to  FIGS. 1 and 4 , each FIO  401 ,  402 ,  403  has a structure as described above for FIO  400 , with forwarding instructions specific to nodes  112 ,  113 ,  114 , respectively. 
     After node  112  receives first FR message  300 , its processor  121  reads first FIO  401  located in a first position of a list of FIOs  320 . With reference also to  FIG. 4 , if action flag  416  is present in FIO  400 , and the action flag  416  specifies “Copy and Forward”, the node  112  copies the FR message  300 , for example, to a node message storage  613 . Processor  121  of node  112  then generates second FR message  602  and forwards (transmits) the second FR message  602  to node  113 . Alternatively, if FR message does not have any action flag  416 , node  112  may, by default, copy FR message  300 , generate second FR message  602 , and then forward second FR message  602  to node  113 . 
     Action flag  416  may specify only “forward”, without “copy”. In such embodiments, node  112  does not copy FR message  300 , but generates the second FR message and forwards second FR message to node  113 . 
     The second FR message  602  has all fields of first FR message  300  except for a first FIO  401  that is removed by processor  121  of node  112 . A modified FIO list  322  of the second FR message  602  starts with second FIO  402 , which comprises forwarding instructions that are specific to node  113 . 
     By removing first FIO  401 , node  112  generates second FR message  602  that is shorter than first FR message  300 , which has been received by node  112 . Shorter second FR message  602  allows for faster reading of second FR message  602  at the next node of the protection detour path  101 . The next node, such as, for example, node  113 , when reading the second FR message  602  reads second FIO  402 , which is now located on the first position of the modified FIO list  322 . 
     Node  112  also updates FR message length value  302  in the second FR message  602 . The value of the number of FIOs  321  in second FR message  602  is also updated by node  112  to be (n−1). 
     The FR message  300  is copied by processor  121  of node  112 , and the second FR message  602  is forwarded to the next node  113 . 
     After the second FR message  602  is forwarded to the next node  113  of the protection detour path  101 , first FR message  300  (or a local copy of message FR message  300 ) may be processed by node  112 . Transmission of second FR message  602  before processing of the first FR message  300 , and then subsequent or simultaneous processing of first FR message  300  by node  112  permits reducing time of propagation of the FR message in the protection detour path  101  and therefore shorten the restoration time of the network. 
     Processing of the FR message  300  by node  112  may comprise reading the LSPOs  500  which corresponds to node  112  in the FR message  300 , and using the data of LSPO  500  to establish data path via node  112  by restoring (in other words, establishing) cross connects at node  112 . 
     The cross connects (which may be also referred to as “cross connections”) on each node along the protection detour path  101  may be programmed (set-up) in parallel. In other words, a path between an input port and an output port of each node, which is a sub-segment of the LSP on the node, may be programmed to transmit the FR message approximately simultaneously with processing of the FR message. In yet other words, the processing of the FR message and transmission of the FR message inside the node via cross connect is not sequential. In at least one embodiment, the LSP data received in the FR message by the node comprises instructions how to set-up the cross connects on that node. 
     Each node may process the FR message  300 ,  602 ,  603 ,  604 , respectively, after forwarding the corresponding modified message downstream to the next node of the protection detour path, so that the FR messages  300 ,  602 ,  603 ,  604  may be processed in parallel (non-sequentially) by the nodes of the protection detour path  101 . 
     As described above, the FR message is forwarded via the message forwarding path  103  specified by the forwarding instructions in the FR message  300 , and is delivered to each node that is located on the protection detour path  101 . Despite the slow routing convergence in case of the network failure, forwarding instructions in the FR message  300  help the FR message to follow the message forwarding path  103  and not to be lost. 
     It should be understood that one node may be configured to generate FR message  300  and copy, forward, and process it as described herein. Referring to  FIG. 1 , node  112  may also, in case of a network failure, determine a protection detour path, and generate another FR message based on a plurality of FIOs and a plurality of LSPOs. In other words, any node of a network may be a source node, and may generate the FR message, and may be a source node of a message forwarding path. 
       FIG. 7  depicts a method for network restoration, in accordance with various embodiments of the present disclosure. When describing  FIG. 7 , reference will also be made to  FIGS. 1-6 . 
     The method  700  may be implemented on a source node  111  of the protection detour path  101 . 
     At step  710 , source node  111  receives LSP failure notification  201 . At step  711 , processor  121  of source node  111  may determine each node of the protection detour path  101  and determine each node of the message forwarding path  103 . In some embodiments, source node  111  may send a request to determine each node of the protection detour path  101  and to determine each node of the message forwarding path  103 , and receive such data subsequently. Nodes of the message forwarding path  103  comprise nodes of the protection detour path  101 . 
     At step  712 , processor  121  of source node  111  may access the forwarding instruction database and may generate a plurality of FIOs  400 . At step  714 , the node&#39;s processor may access the LSP database and generate a plurality of LSPOs  500 . 
     In some embodiments, the plurality of FIOs  400  and/or the plurality of LSPO  500  may be generated by processor  121  in real time, in response to receiving LSP failure notification  201 . 
     At step  716 , processor  121  of source node  111  generates FR message  300 . As described above, the FR message comprises: a plurality of FIOs having forwarding instructions related to each node of a message forwarding path; and a plurality of LSPOs having a restoration LSP data for each node of the protection detour path. In at least one embodiment, the FR message may further comprise: a header comprising a FR message length value, a FR message type identifier, and a FR message version identifier. The FR message may further comprise a value of a number of FIOs of the plurality of FIOs; and a value of a number of LSPOs of the plurality of LSPOs. 
     In at least one embodiment, each FIO of the plurality of FIOs of the FR message comprises an action flag indicating whether the data of FR message should be processed by each node of the message forwarding path. Each FIO of the plurality of FIOs of the FR message may comprise: a FIO length value, a FIO type identifier, and a forwarding label. The number of FIOs in the FR message may be equal to a number of the nodes in the message forwarding path. 
     The number of LSPOs may be equal to a number of LSPs to be restored at each node of the protection detour path. Each LSPO of the plurality of LSPOs of the FR message may comprise: an LSPO length value, an LSPO type identifier, and a restoration LSP data. 
     At step  718 , processor  121  of source node  111  transmits the FR message  300  to another node of protection detour path  101 . Referring also to  FIG. 1 , for example, source node  111  may transmit FR message  300  to node  112  of protection detour path  101 . 
       FIG. 8  depicts another method  800  for network restoration, in accordance with various embodiments of the present disclosure. When describing  FIG. 8 , reference will also be made to  FIGS. 1-6 . 
     For example, method  800  may be implemented on node  112  of the protection detour path  101 . 
     At step  810 , node  112  receives FR message  300 . 
     At step  812 , FR message  300  may be copied to node message storage  613 . The node message storage may be a temporary memory storage. 
     At step  814 , the processor  121  of node  112  generates modified FR message  601  by removing, from FR message  300 , forwarding label  401  related to node  112 . The modified FR message also has an updated FR message length value and an updated value of a number of FIOs. 
     At step  816 , the modified FR message  602  (also referred to herein as “second message  602 ”) is transmitted to next node  113  of message forwarding path  103 . The modified FR message  602  is transmitted based on the forwarding label related to node  112  and provided in FR message  300 . In other words, the modified FR message is transmitted to another node of a message forwarding path  103  based on the first FIO in the plurality of FIOs related to the node  112  and located in the FR message  300 . 
     At step  818 , FR message  300  may be retrieved from the node message storage and processed at node  112  by processor  121  of node  112 . As described above, the FR message has FIO. The FIO may comprise an action flag indicating whether the FR message should be processed by the node. The FR message is processed to restore LSPs related to the node  112  based on the restoration LSP data in the plurality of LSPOs in the FR message  300 . 
     The processor reads LSP objects, decodes the LSP data and uses the LSP data to set up the cross-connections on the data plane. LSP path may be then established and the updated traffic may flow. 
       FIG. 9  depicts a non-limiting example of an optical network  900 , in accordance with various embodiments of the present disclosure. The optical network  900  has 6 wavelength switching nodes  910   a,    910   b,    910   c,    910   d,    910   e,    910   f.  Each node has transponder ports. For example, nodes  910   b  or  910   d  have ports P 1  and P 2 .  FIG. 9  depicts also links between nodes, for example, link “node  910   b  (L 1 )⇄node  910   d  (L 2 )” connects node  910   b  and node  910   d.    
     For example, two tunnels may be generated using GMPLS RSVP-TE PATH/RESV messages. Referring to  FIG. 9 , Tunnel 1  has a working LSP “LSP 1 ” (depicted with dashed lines) using wavelength w 1 . Tunnel 2  has a working LSP “LSP 2 ” (depicted with dots) using wavelength w 2 . Tunnel 1  and Tunnel 2  use different transponder ports but share the same link on a network side. 
     In  FIG. 9 , a route of working LSP LSP 1  may be expressed as follows: node  910   b  w 1  cross-connect P 1 ×L 1 , node  910   d  w 1  cross-connect L 2 ×P 1 , where P 1  refers to P 1  transponder port of the respective node, L 1  and L 2  are optical link interfaces, and w 1  refers to a cross-connect using first wavelength w 1 . In other words, the expression “node  910   b  w 1  cross-connect P 1 ×L 1 ” refers to a cross-connect P 1 ×L 1  at first wavelength w 1  at node  910   b.  Similarly, the expression “node  910   d  w 1  cross-connect L 2 ×P 1 ” refers to a cross-connect L 2 ×P 1  at first wavelength w 1  at node  910   d.    
     The route of working LSP LSP 2  may be expressed as follows: node  910   b  w 2  cross-connect P 2 ×L 1 , node  910   d  w 2  cross-connect L 2 ×P 2 , where P 2  is P 2  transponder port of the respective node, L 1  and L 2  are optical link interfaces, and w 2  refers to a cross-connect using second wavelength w 2 . 
     In the event of a failure of the link “node  910   b  (L 1 )⇄node  910   d  (L 2 )” of optical network  900 , both Tunnel 1  and Tunnel 2  get affected and need to be restored as soon as possible. 
     Once one or more LSP failure notification, that inform of failure(s) of the working LSP(s), is received by source node  910   b,  the source node  910   b  may retrieve protection LSPs from database, if the protection LSPs have been pre-computed before the failure of the working LSP. Alternatively, the source node  910   b  may determine the protection LSPs. Alternatively, the source node  910   b  may request a Path Computing Engine (PCE) server to determine the protection LSPs in real time. 
     For example, the determined protection detour paths for each wavelength (also referred herein as “protection LSPs”) may be expressed as follows. A route of protection LSP LSP 1  may be: node  910   b  w 1  cross-connect P 1 ×L 2 , node  910   f  w 1  cross-connect L 2 ×L 1 , node  910   d  w 1  cross-connect L 1 ×P 1 . A route of protection LSP LSP 2  may be: node  910   b  w 2  cross-connect P 2 ×L 1 , node  910   f  w 2  cross-connect L 2 ×L 1 , node  910   d  w 2  cross-connect L 1 ×P 2 . 
     Protection LSP LSP 1   931  and protection LSP LSP 2   932  share the same nodes  910   b,    910   f  and  910   d.  Therefore, data related to two protection detour paths (protection LSP LSP 1  and protection LSP LSP 2 ), such as restoration LSP data for each node  910   f,    910   d  of the protection LSPs LSP 1   931 , LSP 2   932  may be grouped in a single FR message  300 , as described above. 
     The source node  910   b  determines a message forwarding path of the FR message  300  based on the protection LSP LSP 1  and protection LSP LSP 2  in order to avoid any loss of the FR message  300  due to the link failure, and in order to ensure that all cross-connects are generated successfully on the nodes along the protection detour paths. 
     It should be understood that the message forwarding path may be different from protection LSP LSP 1  and protection LSP LSP 2 . 
       FIG. 10  depicts examples of LSPOs that may be encoded for protection LSPs LSP 1  and LSP 2 , in accordance with various embodiments of the present disclosure.  FIG. 11  depicts alternative examples of LSPOs that may be encoded for protection LSPs LSP 1  and LSP 2 , in accordance with various embodiments of the present disclosure. 
     If the two protection LSP cross-connects were not yet sent to or preconfigured on node  910   d  and node  910   f,  the FR message sent from the source node  910   b  may provide LSPOs  1001 ,  1002  depicted in  FIG. 10  for the cross-connects of node  910   d  and node  910   f.    
     Alternatively, the two protection LSPs may be pre-computed and protection LSP cross-connects may be sent to and preconfigured on node  910   d  and node  910   f  before the failure of the link “node  910   b  (L 1 )⇄node  910   d  (L 2 )”. If the two protection LSPs have been pre-computed, FR message sent from source node  910   b  may comprise protection LSP global identifiers (ID), instead of various fields  1003  of LSPOs  1001 ,  1002  depicted in  FIG. 10 .  FIG. 11  depicts alternative LSPOs  1101 ,  1102  with protection LSP global IDs  1103 ,  1104 . 
       FIG. 12  depicts the optical network  900 , with enabled optical supervisory channels (OSCs) and direct control channels between nodes  910   b  and  910   f,  and between node  910   f  and  910   d.  There are direct control channels between node  910   b  (control interface c 2 ) and node  910   f  (control interface c 2 ), and between node  910   f  (control interface c 1 ) and node  910   d  (control interface c 2 ). Signaling messages in the control plane may be sent over the OSC channels. 
     In  FIG. 12 , there is no failure of protection LSPs between nodes  910   b  and  910   f,  and between  910   f  and  910   d.  Therefore, forwarding of first FR message  300  in the control plane of network  900  follows the same path as the protection LSPs. 
     There is only one intermediate node  910   f  on the message forwarding path  1250 . Therefore, first FR message  300  generated by node  910   b  has only one FIO. 
       FIG. 13  depicts an example of FIO  1300  of FR message  300  for node  910   f,  in accordance with various embodiments of the present disclosure. The first FR message  300  is generated by source node  910   b  and transmitted to node  910   f.  After receiving the first FR message  300 , node  910   f  copies the first FR message  300  and generates a second FR message  602 . 
     The second FR message  602 , as described above, has the same fields as the first FR message  300  except for the FIO  1300 . In other terms, to generate the second FR message, node  910   f  removes the FIO  1300  from the first FR message  300 . 
     The node  910   f  forwards the second FR message  602  to node  910   d,  which is the last node of the message forwarding path  1250 . After the second FR message  602  has been forwarded from node  910   f  to  910   d,  node  910   f  decodes the first FR message  300 . To decode the first FR message  300 , node  910   f  extracts the LSP data such as LSP fields  1003  or LSP global IDs  1103 ,  1104  depicted in  FIGS. 10-11 . Node  910   f  then programs the cross-connects between link L 2  and link L 1  for wavelengths w 1  and w 2 . 
       FIG. 14  depicts the optical network  900  with OSCs enabled and no direct control channels between node  910   b  and  910   f.  For example, the control plane signaling messages may be sent over the OSC channels. Since there is no direct control channels between node  910   b  and  910   f  of the protection LSP route, node  910   b  routing table shows that the control interface cl may be used for message forwarding to node  910   f  through node  910   d.  For example, this may be the shortest path between node  910   b  and node  910   d  in network  900 . However, if the link between node  910   b  and node  910   d  fails, then the control interface cl of node  910   b  should not be used. If the control interface c 1  would be used, any transmitted message would be lost. 
     Therefore, in the event of the failure of the link between node  910   b  and node  910   d,  as depicted in  FIG. 14 , node  910   b  determines another viable path towards node  910   d.  For example, such viable path, which may be used for FR message transmission towards node  910   d,  may be forwarding path  1410  depicted in  FIG. 14 : node  910   b  (through control interface c 3 ) to node  910   a  (through control interface c 1 ) to node  910   c  (through control interface c 1 ) to node  910   f  (through control interface c 3 ) to node  910   d.    
       FIG. 15A  depicts a non-limiting example of a first FR message  1500   b  generated by node  910   b  of network  900 , in accordance with various embodiments of the present disclosure. 
     Since there are 3 intermediate nodes  910   a,    910   c,    910   f  on the forwarding path  1410 , FR message  1500   b  has three FIOs  1520   a,    1520   c,    1520   f  (referred to as “INSTRUCTION” in FR message  1500   b ). The three FIOs  1520   a,    1520   c,    1520   f  may be generated by the source node  910   b.    
     The first two FIOs  1520   a,    1520   c  have fields with action flags indicating “Forwarding” for nodes  910   a  and  910   c,  because nodes  910   a  and  910   c  are not on the protection detour path  1420  (also referred to as “Protection LSP route”). A third FIO  1520   f  has the action flag indicating “Copy+Forwarding” for node  910   f,  because node  910   f  is located on the protection detour path  1420 , which only includes, in this non-limiting example, nodes  910   b,    910   f,  and  910   d.    
     In at least one non-limiting example, protection LSP routes may have been pre-computed for each link failure, and may be stored only at source node  910   b  for each tunnel. In such an example, upon receiving two network failure notifications indicating failure of working LSPs for two wavelengths w 1  and w 2 , source node  910   b  may retrieve two protection LSPs from LSP database  126 . Each one of two protection LSPs corresponds to a specific wavelength w 1  or w 2 . In the non-limiting example of network  900 , the protection LSPs for two wavelengths w 1  and w 2  share the same nodes  910   b,    910   f,    910   d,  and the two protection LSPs may be grouped in a single FR message  1500   b,  as described above. 
       FIG. 15B  depicts a non-limiting example of a second FR message  1500   a  generated by node  910   a  of network  900 , in accordance with various embodiments of the present disclosure.  FIG. 15C  depicts a non-limiting example of a third FR message  1500   c  generated by node  910   c  of network  900 , in accordance with various embodiments of the present disclosure.  FIG. 15D  depicts a non-limiting example of a fourth FR message  1500   f  generated by node  910   f  of network  900 , in accordance with various embodiments of the present disclosure. 
     After the FR message  1500   b  is sent out by node  910   b  to node  910   a,  node  910   b  may delete two old cross-connects: P 1 ×L 1  cross-connect using wavelength w 1 , and P 2 ×L 1  cross-connect using wavelength w 2 . Node  910   b  may then generate two new cross-connects: P 1 ×L 2  cross-connect using wavelength w 1 , and P 2 ×L 2  cross-connect using wavelength w 2 . 
     After two new cross-connects have been generated, node  910   b  may start a timer. The timer may count a delay of, for example, 5 seconds. After the timer times out (assuming the protection paths have been set up and data traffic is flowing), node  910   b  may send RSVP-TE PATH messages along the protection paths to synchronize control plane/RSVP soft states with the data plane. 
     Upon receiving of the FR message  1500   b  from node  910   b,  node  910   a  decodes the message and reads the first FIO  1520   a  in the list of FIOs (INSTRUCTION objects). The first FIO  1520   a  has an action flag indicating “Forwarding” and a forwarding label value “Outgoing Local Interface C 1 ”. In at least one non-limiting embodiment, the action flag “Forwarding” may indicate that node  910   a  does not need to copy and process message in order to replace cross-connects thereon. Node  910   a  removes the first FIO  1520   a  from the message body, updates the value of “Number of Instructions” field to have a value of “2” instead of “3”, and updates the value of “Length” field (of the FR message) to be “96” instead of “104”. Node  910   a  may thus generate a modified second FR message  1500   a  and then may send the second FR message  1500   a  out from a local control interface C 1  of node  910   a  to node  910   c.    
     Upon receiving of the second FR message  1500   a  from node  910   a,  node  910   c  decodes the second FR message  1500   a  and reads the first FIO in the list of FIOs. The first FIO in the list of FIOs of the second FR message  1500   a  is a second FIO  1520   c.  The value of the action flag field of second FIO  1520   c  is “Forwarding”. The value of a “forwarding label” field of second FIO  1520   c  is “Outgoing Local Interface C 1 ”. 
     The action flag value of second FIO  1520   c  “Forwarding” may indicate that node  910   a  does not need to copy and process message further (for example, for provisioning cross-connects). In such example, node  910   c  removes second FIO  1520   c  from the second FR message  1500   a,  updates the value of “Number of Instructions” field to be “1” instead of “2”, and updates the value of “Length” field to be 88 instead of 96. Node  910   c  thus generates a third FR message  1500   c  and sends the third FR message  1500   a  out from its local control interface C 1 . 
     Upon receiving the third FR message  1500   c  from node  910   c,  node  910   f  decodes the third FR message  1500   c  and reads the top FIO in the list of FIOs of third FR message  1500   c:  the third FIO  1520   f.  In  FIG. 15C , the third FIO  1520   f  has an action flag field indicating “Copy+Forwarding”. The value of the forwarding label is “Outgoing Local Interface C 3 ”. 
     In this non-limiting example, the action flag value of “Copy+Forwarding” of third FIO  1520   f  may indicate that node  910   f  needs to copy and process the third FR message  1500   c  further in order to restore cross-connects at the data plane. After the third FR message  1500   c  is copied, node  910   f  removes the third FIO  1520   f.  Node  910   f  may also remove data relative to two cross-connects for node  910   f  from the third FR message  1500   c.  Node  910   f  also updates the value of “Number of Instructions” field to be 0 instead of 1, and updates the value of “Length” field to be 56 instead of 88. Node  910   f  may thus generate a fourth FR message  1500   f  depicted in  FIG. 15D . Node  910   f  then sends the generated fourth FR message  1500   f  to node  910   d  out from its local control interface C 3 . 
     After the fourth FR  1500   f  message is sent out to node  910   d,  node  910   f  validates the resource availability and generates two cross-connects on the data plane of node  910   f.  Based on the data received in the third FR message  1500   c,  node  910  may generate two cross-connects: (1) node  910   f  w 1  cross-connect L 2 ×L 1 , which refers to a cross-connect between links L 2  and L 1  using first wavelength w 1 , and (2) node  910   f  w 2  cross-connect L 2 ×L 1 , which refers to a cross-connect between links L 2  and L 1  using second wavelength w 2 . 
     After receiving the fourth FR message  910   f  from node  910   f,  node  910   d  decodes the message and determines that there is no FIO in the fourth FR message  910   f.  Absence of FIO indicates that there is no need to send an outgoing FR message from node  910   d,  because node  910   d  is a destination node of the protection detour path. 
     The received fourth FR message  1500   f  is then processed by node  910   d.  Based FR message  1500   f,  node  910   d  may validate the resource availability and delete two old cross-connects L 2 ×P 1  (with wavelength w 1 ) and L 2 ×P 2  (with wavelength w 2 ). Based on FR message  1500   f,  node  910   d  then generates two new cross-connects L 1 ×P 1  (with wavelength w 1 ) and L 1 ×P 2  (with wavelength w 2 ). 
     Although the present invention has been described with reference to specific features and embodiments thereof, it is evident that various modifications and combinations can be made thereto without departing from the invention. The specification and drawings are, accordingly, to be regarded simply as an illustration of the invention as defined by the appended claims, and are contemplated to cover any and all modifications, variations, combinations or equivalents that fall within the scope of the present invention.