JP4398922B2 - Optical network and edge switch - Google Patents

Description

  The present invention relates to an optical network and an edge switch that connects a layer 2 network through the optical network.

  As a WAN (Wide Area Network) service for enterprises, the use of a wide area Ethernet (registered trademark) service is rapidly increasing, and a large-scale and large-capacity layer 2 network serving as the backbone is a problem.

  In general, in a layer 2 network, STP (Spannig Tree Protocol) is used for path switching at the time of failure. The STP generates a loop-free tree by setting a part of a link that becomes a loop in the topology to a block state (a state in which no packet flows). In addition, this STP can reconfigure a tree when a failure is detected in a switch or a line.

On the other hand, OXC (Optical cros) is a technology for economically increasing the capacity of networks.
GMPLS (Generalized Multi-Protocol Label Switching, see Non-Patent Document 1) that can flexibly control optical paths on an optical network composed of optical switches such as s-Connect (optical cross-connect) is drawing attention. In this GMPLS, IP (Internet Protocol) routing protocol and signaling protocol are used to advertise topology information and resource information in the optical network and to establish and release an optical path.

Here, in order to realize a large capacity of the layer 2 network, a method of applying the optical network using the GMPLS to the core part is also conceivable (see FIG. 6).
FIG. 6 is a diagram illustrating a network configuration of a comparative example. In FIG. 6, the optical network 1 and the layer 2 network 2 are connected by an edge switch 3, and the edge switch 3 shows a state in which an optical path 5 is established with another edge switch via the optical switch 4. .
In such a network configuration, each of the layer 2 networks 2 (2A, 2B) connected to the optical network 1 determines the existence of the optical network 1 by allowing the edge switch 3 to pass the STP transparently in the optical network 1. A tree (communication path) can be generated by STP without being conscious of it.
For example, by using STP transparently in the optical network 1, a tree (path) from the node A of the layer 2 network 2A to the node B of the layer 2 network 2B can be generated.

Eric Mannie (Editor), “Generalized Multi-Protocol Label Switching (GMPLS) architecture”, RFC3945, [online], [searched July 1, 2005], Internet <URL: http://www.ietf.org/ rfc / rfc3945.txt>

However, STP is a mechanism for generating a tree by propagating the information of each switch one after another on the network, so that there is a problem that it takes time to generate the tree as the network scale increases. In addition, there is a problem that the reliability of the network may be lowered because all transfer stops while the tree is being reconfigured.
For example, in the example shown in FIG. 6, when a failure occurs in the layer 2 switch (L2) in the layer 2 network 2A, it is necessary to reconfigure the tree from the node A to the node B. That is, when the scale of the network increases, there is a problem that it takes time until communication is restored, and the reliability of the network may be lowered.

  An object of the present invention is to solve the above-described problems and provide an optical network and an edge switch capable of constructing a highly reliable network even when a large-scale layer 2 network is constructed using STP.

  In order to solve the above-described problem, the present invention provides an STP protocol control unit that determines whether an edge switch of an optical network connecting a layer 2 network is in an active state by STP (Spanning Tree Protocol). According to GMPLS (Generalized Multi-Protocol Label Switching) protocol, (1) To the other edge switch of the optical network, the identification information of its own edge switch and whether or not its own edge switch is in the active state Edge switch information including an Active identifier is transmitted, (2) the edge switch information of the other edge switch is received from the other edge switch, and (3) the edge switch information of the own edge switch and the received Edge switch information of other edge switches A GMPLS protocol control unit that records in the switch database, an edge switch database that indicates an active identifier of the edge switch for each piece of identification information of the edge switch, and an edge switch that is in an active state with reference to the edge switch database And a tree control unit that calculates a tree of communication paths in the optical network and directs establishment of an optical path based on the calculated tree of communication paths.

According to such a configuration, the edge switch links the STP operating in the layer 2 network to which the edge switch is connected with the tree (communication path tree) in the optical network, and establishes an original communication path. Can be generated.
That is, first, each edge switch of the optical network determines whether it is in an active state by STP. Then, the edge switch information including information regarding whether or not it is in the active state is exchanged between the switches constituting the optical network and recorded in the edge switch database. Next, each edge switch refers to the edge switch database, generates a tree connecting the active edge switches in the optical network, and establishes an optical path. Therefore, the STP domain (the range in which switch information propagates) can be limited to each layer 2 network as a whole network while connecting the layer 2 networks.

Also, the edge switch of the present invention uses the standard GMPLS routing protocol such as OSPF (Open Shortest Path First) or IS-IS to obtain information (edge switch information) necessary for calculating a tree in the optical network. (Intermediate System to Intermediate System) is used for transmission and reception. According to such a configuration, it is not necessary to separately install a special protocol in the edge switch for calculating a tree in the optical network.
Note that configurations other than the above-described configuration will be described in detail in an embodiment described later.

  According to the present invention, since the edge switch generates a unique tree in the optical network portion, the STP domain (the range in which switch information propagates) can be limited to the layer 2 network. That is, the influence at the time of failure such as a switch failure can be localized in each layer 2 network. Therefore, even when layer 2 networks are connected to each other and a large-scale network is built nationwide, communication reliability can be improved.

  Hereinafter, the best mode for carrying out the present invention (hereinafter referred to as an embodiment) will be described with reference to the drawings.

FIG. 1 is a diagram showing a network configuration according to an embodiment of the present invention. A network configuration according to an embodiment of the present invention will be described with reference to FIG.
The network of the present embodiment has a configuration in which a plurality of layer 2 networks 2 (2A to 2C) are connected by an optical network 1. The optical network 1 includes an edge switch 3 (3A to 3F) and an optical switch 4 such as an OXC (optical cross connect). The layer 2 network 2 is, for example, an Ethernet (registered trademark) network.

  The edge switch 3 serves to connect the optical network 1 and the layer 2 network 2 and has a switching function in the layer 2 network 2 and an optical path control function. The edge switch 3 includes an arithmetic processing unit such as a CPU (Central Processing Unit), a storage unit such as a RAM (Random Access Memory) and a ROM (Read Only Memory), and the optical network 1 (and the GMPLS control plane 6). An interface that controls data input / output between them, an interface that controls data input / output with the layer 2 network 2, and a switching unit. The arithmetic processing unit operates each protocol described later by executing a program stored in the storage unit.

  The optical switch 4 has a switching function at an optical path or wavelength level, and provides connectivity at the optical layer between the edge switches 3, that is, an optical path.

In the present embodiment, it is assumed that the layer 2 network 2 and the optical network 1 are connected by two edge switches 3 in order to ensure redundancy.
That is, as shown in FIG. 1, the edge switch 3 that connects the layer 2 network 2A and the optical network 1 has two switches, the edge switch 3A (# 1) and the edge switch 3B (# 2).

The two edge switches 3 (3A, 3B) operate the STP in the layer 2 network 2 to generate a communication path (tree), but the layer 2 switch (in FIG. 1) It is assumed that the priority is set higher than that of the symbol L2), and that one of the two is set as an STP root bridge.
That is, in a normal state, the edge switch 3 with the higher priority performs data transfer with the optical network 1, and when a failure or the like occurs, the edge switch 3 with the lower priority has the optical network 1. Data transfer to and from.

The optical network 1 controls establishment and release of an optical path by GMPLS. For this reason, a GMPLS control plane 6 for operating the GMPLS protocol is prepared.
The GMPLS control plane 6 is a network for transmitting and receiving control information of the optical network 1 by the GMPLS protocol. The GMPLS control plane 6 may use a network that is physically separate from the optical network 1, or may use the physically same network and flow the GMPLS protocol as a logically separate network.

  The edge switch 3 and the optical switch 4 in the GMPLS control plane 6 are mounted with a control plane instance for controlling the optical path by operating the GMPLS routing protocol and signaling protocol.

  The control plane instance is stored in the storage unit of the edge switch 3, and the CPU reads the data of the control plane instance from the storage unit and executes it, thereby realizing the GMPLS protocol control unit 102 of FIG. It shall be.

  Further, the edge switch 3 advertises (transmits) various types of information regarding its own node to other edge switches using OSPF (Open Shortest Path First) or the like for performing path control in GMPLS. Details of the information advertised at this time will be described later.

<Configuration of edge switch>
FIG. 2 is a block diagram showing the function of the edge switch of FIG. The function of the edge switch 3 in FIG. 1 will be described with reference to FIG.
Here, the control system function of the edge switch 3 will be mainly described, and the transfer system function of the edge switch 3 (data received from the layer 2 network 2 is transferred to the optical network 1 or data received from the optical network 1). The function of transferring the data to the layer 2 network 2) will be omitted.

  The edge switch 3 includes an STP protocol control unit 101 that operates STP for the layer 2 network 2 to which the edge switch 3 belongs, a GMPLS protocol control unit 102 that operates GMPLS on the optical network 1 side, and a communication path (tree) in the optical network 1 And a tree control unit 103 for generating a trigger for establishing an optical path belonging to the tree, an edge switch DB (database) 104 for recording the states of all edge switches 3 belonging to the optical network 1, and an optical network 1 side And a tree DB (database) 105 that records the state of the communication path (tree).

  The STP protocol control unit 101, the GMPLS protocol control unit 102, and the tree control unit 103 are realized by the CPU of the edge switch 3 executing a control plane instance and a predetermined program stored in the storage unit. . The edge switch DB 104 and the tree DB 105 are stored in a predetermined area of the storage unit of the edge switch 3.

  In the following description, when the STP protocol control unit 101 transmits / receives data to / from the layer 2 network 2, an input / output interface with the layer 2 network 2 is used, and the GMPLS protocol control unit 102 uses the GMPLS control plane. When transmitting / receiving data to / from 6, an input / output interface with the GMPLS control plane 6 is used.

The STP protocol control unit 101 operates a standard-compliant STP with a layer 2 switch (symbol L2 in FIG. 1) existing in the layer 2 network 2, and generates a tree in the layer 2 network 2.
Here, when the STP protocol control unit 101 determines by STP that its edge switch 3 is the “root bridge” that is the root of the tree, it sets its own Active identifier in the edge switch DB 104 described later to “Yes”. . Details of the edge switch DB 104 will be described later.

The GMPLS protocol control unit 102 operates the GMPLS protocol with the optical switch 4 and other edge switches constituting the optical network 1 to establish and release an optical path.
Further, the following information is advertised to other edge switches as part of the information exchanged in the OSPF (hereinafter referred to as OSPF extended information).
(1) Identification information (RouterID) of own edge switch 3
(2) Identification information (SiteID) of the layer 2 network 2 to which it belongs
(3) Priority of own edge switch 3 in optical network 1 (4) Active identifier indicating whether own edge switch 3 is in an active state (for example, a root bridge) in layer 2 network 2

  In the following description, the above (1) to (4) are collectively referred to as edge switch information. Further, this edge switch information may be advertised as IS-IS (Intermediate System to Intermediate System) extension information that is a routing protocol.

  Further, when receiving the edge switch information advertised from another edge switch, the GMPLS protocol control unit 102 records the edge switch information in the edge switch DB 104 described above.

  The tree control unit 103 refers to the edge switch DB 104 and calculates a tree in the optical network 1. If it is determined that it is necessary to establish an optical path from the edge switch 3 side, the GMPLS protocol control unit 102 is instructed to establish an optical path. The tree calculation method and the trigger for instructing the establishment of the optical path will be described later.

  FIG. 3 is a diagram illustrating the edge switch DB of FIG. The edge switch DB 104 will be described with reference to FIGS. 1 and 2 and FIG. The edge switch DB 104 in FIG. 2 is a database created based on the network configuration in FIG.

The edge switch DB 104 indicates the edge switch information of the edge switch 3 for each piece of identification information (RouterID) of the edge switch 3.
In this edge switch DB 104, “RouterID” denoted by reference numeral 201 is information for identifying the edge switch 3 in the GMPLS control plane 6. This Router ID is used not only for optical path control but also for advertisement of information necessary for generating a tree.

“SiteID” indicated by reference numeral 202 is identification information of the layer 2 network 2 to which the edge switch 3 belongs. For example, the edge switches 3 (3A, 3B) with Router IDs “# 1” and “# 2” belong to “SiteID = A (layer 2 network 2 (2A))”.
Here, the edge switches 3 (3A, 3B) belonging to the same layer 2 network 2 are in a state in which a tree is configured by STP, and connectivity is always ensured. That is, if a tree connecting the edge switches 3 to the optical network 1 is generated in this state, a loop occurs. Therefore, among the plurality of edge switches 3 (3A, 3B) belonging to the same layer 2 network 2, each edge switch 3 needs to be controlled to include any one in the tree. SiteID is used for control at this time.

  “Priority” indicated by reference numeral 203 indicates the priority of the edge switch 3 in the optical network 1 of the edge switch 3. For example, the priority of the edge switch 3A of “# 1” is “5”, and the priority of the edge switch 3C of “# 3” is “10”. This priority is for calculating the tree of the edge switch 3 in the optical network 1 and selecting the root of the tree. For example, the edge switch 3 having the highest priority value (for example, the edge switch 3C of “# 3”) is selected as a route.

  “Active (Active identifier)” denoted by reference numeral 204 indicates whether or not the edge switch 3 is in an Active state (a state in which data transfer can be performed between the layer 2 network 2 and the optical network 1). For example, the “# 1” edge switch 3A indicates the Active state (Yes), and the “# 2” edge switch 3B indicates that the Edge switch 3B is not in the Active state (No).

  Here, the edge switch 3 having the same SiteID is controlled by the STP protocol control unit 101 so that only one of them is in the Active state (Active identifier = Yes). Then, the tree control unit 103 determines which edge switch 3 is included in the tree of the optical network 1 by referring to the Active identifier. That is, the edge switch 3 in the active state is included in the tree of the optical network 1, but the edge switch 3 that is not in the active state is not included in the tree of the optical network 1.

  In this embodiment, the STP protocol control unit 101 selects a single edge switch 3 in the active state (active identifier = Yes) among the edge switches 3 having the same Site ID. A method of selecting the edge switch 3 serving as a root bridge is used.

  This is because at least if the edge switch 3 is a root bridge, data transfer is possible between the layer 2 network 2 and the optical network 1, and there are a plurality of edge switches 3 in the layer 2 network 2. This is because in the case of connection, there is always one of the root bridges, so that a plurality of edge switches 3 are determined to be in the active state and a loop is not generated.

  Note that the method by which the edge switch 3 having the same SiteID selects the edge switch 3 in the active state is not limited to the method described above. For example, information different from the priority of STP (information such as priority for selecting the edge switch 3 in the active state) may be propagated in the layer 2 network 2.

  FIG. 4 is a diagram illustrating the tree DB of FIG. The tree DB 105 will be described using FIG. 4 with reference to FIGS.

The tree DB 105 is a database that records information on optical paths of trees configured in the optical network 1.
In the “optical path section” denoted by reference numeral 301, RouterIDs of the edge switches 3 at both ends of the optical path are described.
The “initiator” indicated by reference numeral 302 describes the Router ID of the edge switch 3 of the optical path initiator. That is, the RouterID of the edge switch 3 that first transmits signaling for establishing an optical path is described.
In the present embodiment, the edge switch 3 having a lower priority value in the edge switch DB 104 is described as an initiator. However, the edge switch 3 having a higher priority value may be the initiator. Good.
An “optical path ID” denoted by reference numeral 303 is optical path identification information. This is used for GMPLS signaling by the GMPLS protocol control unit 102.

The edge switch 3 is assumed to store a database of optical paths established in the optical network 1 in the storage unit separately from the tree DB 105. In this database, for each optical path ID, detailed information regarding the optical path such as identification information and resource information of the optical switch 4 passing through the optical path is recorded, and when the GMPLS protocol control unit 102 operates the GMPLS protocol. To be referenced.
Further, when the edge switch 3 itself is not at either end of the optical path, nothing is described in the column of the optical path ID of the tree DB 105.

<Operation of edge switch>
FIG. 5 is a flowchart for explaining the operation of the edge switch of FIG. The operation of the edge switch 3 will be described using FIG. 5 with reference to FIGS. The network configuration here is as shown in FIG. Hereinafter, the operation of the edge switch 3A in FIG. 1 will be mainly described.

  First, a tree is generated by STP in the layer 2 network 2A to which the edge switch 3A belongs, and a root bridge is selected (S501). Here, it is assumed that the edge switch 3A is selected as the root bridge.

  In the layer 2 network 2A, which edge switch 3 is used as the root bridge is determined by the layer 2 network 2A administrator or the like by setting the bridge priority value of the edge switch 3 and setting the bridge ID value for each layer. This is possible by setting the lowest value among the two switches.

  The GMPLS protocol control unit 102 of the edge switch 3A reads the edge switch information of the edge switch 3A stored in the edge switch DB 104. Then, in the GMPLS control plane 6, the edge switch information (RouterID, SiteID, priority, Active identifier) of the edge switch 3A is advertised (transmitted) to all other edge switches 3 using the OSPF extension information (S502).

For example, the GMPLS protocol control unit 102 of the edge switch 3A advertises edge switch information “RouterID = # 1, SiteID = A, priority = 5, Active identifier = Yes” to the edge switches 3C and 3E. Further, although the description is omitted here, the same advertisement is also performed on the edge switches 3B, 3D, 3F (see FIG. 1).
Note that the edge switch information of the edge switch 3A in the edge switch DB 104 is input in advance via the input / output interface by an administrator of the edge switch 3A or the like.

  Subsequently, the GMPLS protocol control unit 102 of the edge switch 3A receives edge switch information from another edge switch 3 (S503).

  For example, edge switch information “RouterID = # 3, SiteID = B, priority = 10, Active identifier = Yes” from the edge switch 3C, and “RouterID = # 5, SiteID = C, priority = 5” from the edge switch 3E. , Active identifier = Yes ”is received. Although not described here, the edge switch information is similarly received from the edge switches 3B, 3D, and 3F (Active identifier = No edge switch 3). At this time, the received edge switch information is also advertised by the OSPF extension information.

  Next, the GMPLS protocol control unit 102 of the edge switch 3A records the received edge switch information in the edge switch DB 104 (S504).

  Subsequently, the tree control unit 103 of the edge switch 3A refers to the edge switch DB 104, calculates a tree, and records the result in the tree DB 105 (S505).

  For example, the tree control unit 103 refers to the edge switch DB 104 in FIG. 3 and calculates a tree as follows.

  First, the tree control unit 103 searches the edge switch DB 104 for the edge switch 3 whose Active identifier is “Yes (Active state)”. Here, the edge switch 3A (# 1), the edge switch 3C (# 3), and the edge switch 3E (# 5) are searched.

  Next, when the priority of the edge switch 3 (3A, 3C, 3E) in the edge switch DB 104 is seen, it can be seen that the priority of the edge switch 3C (# 3) is the highest. Therefore, the edge switch 3C (# 3) is determined to be the root of the tree in the optical network 1. That is, the tree control unit 103 selects the edge switch 3 in the active state and high priority as the root in the edge switch DB 104.

  Then, the tree control unit 103 calculates a tree including the edge switches 3A and 3E in the other active state with the edge switch 3C as a root, and records information on the optical paths constituting the tree in the tree DB 105.

Note that the edge switch 3 serving as the initiator of the optical path selects, for example, the edge switch 3 having the lower priority among the edge switches 3 serving as both ends of the optical path. For example, when the optical path 5 is established between the edge switch 3A (# 1) and the edge switch 3C (# 3), the edge switch 3A (# 1) has a lower priority in the edge switch DB104. Therefore, this edge switch 3A (# 1) is selected as an initiator.
As an algorithm for the tree control unit 103 to calculate a tree, for example, a Dijkstra algorithm used for OSPF path calculation can be applied, but the present invention is not limited to this.

When the tree control unit 103 finishes calculating the tree, the tree control unit 103 refers to the tree DB 105 to determine whether or not there is an optical path for which its own edge switch 3A (# 1) is to be an initiator (S506). Here, when it is determined that the edge switch 3A (# 1) has an optical path to be an initiator (Yes in S506), the tree control unit 103 sends a GMPLS protocol control unit 102 to the other end of the optical path. GMPLS signaling is transmitted to a certain edge switch 3 (for example, edge switch 3C (# 3)) (S507). Then, the edge switch 3A (# 1) establishes the optical path 5 (see FIG. 1) with the counterpart edge switch 3 (for example, the edge switch 3C (# 3)) (S508).
If it is determined in S506 that there is no optical path that should be the initiator on the edge switch 3A (# 1) side (No in S506), the process is terminated.

  Although not described here, the same processing is performed in all the edge switches 3 (3B to 3F) constituting the optical network 1, and a tree in the optical network 1 is generated.

<Tree reconstruction procedure>
Next, a procedure for reconfiguring a tree in the optical network 1 accompanying the failure of the edge switch 3 will be described. For example, when a failure occurs in the edge switch 3A (# 1), the tree is reconfigured by STP in the layer 2 network 2A. Here, since the edge switch 3B (# 2) has the highest priority after the edge switch 3A (# 1), the edge switch 3B (# 2) becomes a root bridge. That is, the edge switch 3B (# 2) recognizes the reconstructed tree by the STP protocol control unit 101 and knows that it has become a root bridge.

  In response to this, the STP protocol control unit 101 of the edge switch 3B (# 2) rewrites the Active identifier of its edge switch information in the edge switch DB 104 (see FIG. 3) to “Yes”. Similarly to S502 in FIG. 5, the edge extension information is advertised by using the OSPF extension in the optical network 1 to notify that the device is in the active state. Thereafter, the edge switch 3B reconfigures the tree in accordance with the procedure from S503 described above.

  Also, when the edge switches 3C to 3F receive edge switch information indicating that the edge switch 3B (# 2) is in the active state, the edge switches 3C to 3F reconfigure the tree and generate optical paths at necessary locations. For example, an optical path established between the edge switch 3A (# 1) and the edge switch 3C (# 3) is changed to an optical path connecting the edge switch 3B (# 2) and the edge switch 3C (# 3). change. In this way, each edge switch 3 can reconfigure the tree in the optical network 1 even when a failure occurs in the edge switch 3.

  According to such a configuration, since the edge switch 3 generates a unique tree in the optical network 1, the STP domain can be limited to the layer 2 network. That is, the influence of a failure of the layer 2 switch and the like can be localized in each layer 2 network 2. Therefore, even when a plurality of layer 2 networks 2 are connected to construct a nationwide large-scale network, communication reliability can be improved.

  Further, since OSPF extended information and IS-IS extended information are used for advertising edge switch information, it is not necessary for each edge switch 3 to implement a special protocol for advertising edge switch information.

  The edge switch 3 according to the present embodiment can be realized by a program that causes the CPU to execute the processing as described above, and the program is stored in a computer-readable storage medium (CD-ROM or the like) and provided. Is possible. It is also possible to provide the program through a network such as the Internet.

In the above-described embodiment, each edge switch 3 configuring the optical network 1 holds the edge switch DB 104 indicating the active state of each edge switch 3, and generates a tree. However, the present invention is not limited to this. Not.
For example, a management server that manages each edge switch 3 and optical switch 4 is installed on the GMPLS control plane 6, and the edge switch information of each edge switch is acquired by this management server to generate a tree. Good. Other modifications can be made without departing from the spirit of the present invention.

It is a figure which shows the network structure of one Embodiment of this invention. It is the block diagram which expanded and showed the function of the edge switch of FIG. It is the figure which illustrated edge switch DB of FIG. It is the figure which illustrated tree DB of FIG. 3 is a flowchart for explaining the operation of the edge switch of FIG. 2. It is a figure which shows the network structure of a comparative example.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Optical network 2 (2A, 2B) Layer 2 network 3 (3A-3F) Edge switch 4 Optical switch 5 Optical path 6 GMPLS control plane 101 STP protocol control part 102 GMPLS protocol control part 104 Edge switch DB
105 Tree DB

Claims (10)

An optical network comprising a plurality of edge switches for connecting a layer 2 network to an optical network,
The edge switch is
An STP protocol controller that generates a tree of communication paths in the layer 2 network by STP (Spanning Tree Protocol) and determines whether or not its own edge switch is in an active state;
According to the GMPLS (Generalized Multi-Protocol Label Switching) protocol, (1) to the other edge switch in the optical network, the identification information of the own edge switch, and the Active identifier indicating whether the own edge switch is in the Active state, Send edge switch information including
(2) receiving edge switch information of the other edge switch from the other edge switch;
(3) a GMPLS protocol control unit that records edge switch information of the edge switch of the own device and edge switch information of the received other edge switch in an edge switch database;
An edge switch database indicating an active identifier of the edge switch for each piece of identification information of the edge switch;
Referring to the edge switch database, calculate a tree of communication paths in the optical network including the edge switch in the active state, and instruct the GMPLS protocol control unit to establish an optical path based on the calculated tree. A tree control;
An optical network comprising: The edge switch information includes a priority of the edge switch in the optical network,
2. The tree control unit according to claim 1, wherein the tree control unit calculates a communication path tree in the optical network with an edge switch having an active state and a highest priority as a root by referring to the edge switch database. Optical network as described in. The edge switch information includes a priority of the edge switch in the optical network,
The tree control unit refers to the edge switch database, the edge switch is active, and the priority of the edge switch is higher than the priorities of other edge switches connected by the optical path. 3. The optical network according to claim 1, wherein when the degree is low, the GMPLS protocol control unit is instructed to establish an optical path with the other edge switch.   The GMPLS protocol control unit transmits the edge switch information as extended information of OSPF (Open Shortest Path First) or extended information of IS-IS (Intermediate System to Intermediate System). Item 4. The optical network according to any one of Items 3 to 3.   The optical network according to any one of claims 1 to 4, wherein the active state is that the edge switch is a root bridge in a layer 2 network to which the edge switch belongs. An edge switch that connects a layer 2 network to an optical network,
An STP protocol controller that generates a tree of communication paths in the layer 2 network by STP (Spanning Tree Protocol) and determines whether or not its own edge switch is in an active state;
According to the GMPLS (Generalized Multi-Protocol Label Switching) protocol, (1) to the other edge switch in the optical network, the identification information of the own edge switch, and the Active identifier indicating whether the own edge switch is in the Active state, Send edge switch information including
(2) receiving edge switch information of the other edge switch from the other edge switch;
(3) a GMPLS protocol control unit that records edge switch information of the edge switch of the own device and edge switch information of the received other edge switch in an edge switch database;
An edge switch database indicating an active identifier of the edge switch for each piece of identification information of the edge switch;
Referring to the edge switch database, calculate a tree of communication paths in the optical network including the edge switch in the active state, and establish the optical path based on the calculated tree of communication paths by the GMPLS protocol control unit An edge switch comprising: a tree control unit that instructs The edge switch information includes a priority of the edge switch in the optical network,
7. The tree control unit calculates a communication path tree in the optical network by referring to the edge switch database and using an edge switch having an active state and a highest priority as a root. Edge switch as described in. The edge switch information includes a priority of the edge switch in the optical network,
The tree control unit refers to the edge switch database, the edge switch is active, and the priority of the edge switch is higher than the priorities of other edge switches connected by the optical path. The edge switch according to claim 6 or 7, wherein when the degree is low, the GMPLS protocol control unit is instructed to establish an optical path with the other edge switch.   7. The GMPLS protocol control unit transmits the edge switch information as extended information of OSPF (Open Shortest Path First) or extended information of IS-IS (Intermediate System to Intermediate System). Item 9. The edge switch according to any one of Items 8.   The edge switch according to any one of claims 6 to 9, wherein the active state is that the edge switch is a root bridge in a layer 2 network to which the edge switch belongs.

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