JP2008252579A - Node arranged by using wavelength selection switch, and inter-node connection confirming method - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To confirm a physical link connection between nodes arranged by using a wavelength selection switch, without an external optical transmission/reception device. <P>SOLUTION: A node 12 has drop wavelength selection switches 26 and 28, and add wavelength selection switches 27 and 29 respectively on an up link 24 and a down link 25. A port of the drop wavelength selection switch 26 and a port of the add wavelength selection switch 29 are connected to the port of the drop wavelength selection switch 28 and the port of the add wavelength selection switch 27, thereby making the node 12 have a loopback function. A link connection confirmation light from another node is looped back, so that presence/absence of an inter-link fault is determined based on a reception light level. <P>COPYRIGHT: (C)2009,JPO&INPIT

Description

  The present invention relates to a node configured using a wavelength selective switch and a link connectivity confirmation method for confirming physical link connectivity between nodes.

  The physical link connectivity between nodes in the optical network can be confirmed by transmitting light from one end side node of the link to be confirmed and receiving the transmitted light at the other end side node.

  FIG. 9 is a conceptual diagram showing a conventional method for confirming link connectivity between nodes. Here, the simplest two-node network configuration in an optical network is shown. Nodes 91 and 92 are interposed between the client apparatuses A and B. Each node 91, 92 includes an optical cross connect (PXC) and WDM. The connectivity of the physical link between the nodes 91 and 92 can be confirmed by externally attaching optical transceivers C and D to the nodes 91 and 92 and transmitting and receiving light between them. For example, the connectivity of the link between the nodes 91 and 92 can be confirmed by transmitting light from the optical transceiver C on the node 91 side and receiving the light transmitted through the link by the optical transceiver D on the node 92 side. Such link connectivity confirmation methods are described in Non-Patent Documents 1 and 2 below.

Patent Document 1 describes an optical cross-connect and an optical network monitoring system used for quality measurement of unused paths. In this case, a return port is provided in the optical cross-connect, light for quality measurement is transmitted to the unused path, and the light returned by the return port of the optical cross-connect at the end is received, thereby the unused path. Determine whether there is a fault or the contents of the fault.
JP 2006-197095 A IETF RFC4204 Section5 IETF RFC4209 Section2

  In recent optical networks, nodes are configured using wavelength selective switches (WSS). By using a wavelength selective switch as a node, an optical signal of a specific wavelength can be branched (dropped) from the optical network as it is and inserted (added) into the optical network, and an all-optical network without OE conversion can be constructed.

  FIG. 10 is a block diagram showing a conventional node configuration configured using a wavelength selective switch. The node has a drop wavelength selective switch 26 and an add wavelength selective switch 27 on the uplink 24 that transmits the optical signal to the left side in the figure, and a drop wavelength selective switch 28 and an add wavelength on the downlink 25 that transmits the optical signal to the right side in the figure. A selection switch 29 is provided. The drop wavelength selection switches 26 and 28 select a predetermined wavelength optical signal (s) from the WDM signals transmitted through the links 24 and 25, drop them to the outside through appropriate ports, and select the add wavelength. The switches 27 and 29 add a predetermined wavelength optical signal from the outside to the links 24 and 25 via appropriate ports.

  However, the conventional wavelength selective switch has a function of simply dropping or adding light of a predetermined wavelength, and does not have a function of looping back light input through the link. For this reason, in order to confirm the connectivity of the physical link between the nodes configured by using the wavelength selective switch, the optical transmission / reception to each node is performed in the same manner as described in Non-Patent Documents 1 and 2. There is a problem that it is necessary to attach and receive light for link connectivity confirmation between the devices.

  The optical network route monitoring system described in Patent Document 1 monitors the presence or absence of a failure in a link between nodes configured using an optical cross-connect or the content of the failure, and is configured using a wavelength selective switch. It does not confirm the physical connectivity of the links between the nodes.

  An object of the present invention is to solve the above-mentioned problems and to make it possible to confirm physical link connectivity between nodes without the need for an external optical transceiver, a node configured using a wavelength selective switch, The object is to provide a link connectivity confirmation method for confirming physical link connectivity between nodes.

  In order to solve the above problems, a node configured using a wavelength selective switch according to the present invention includes a drop wavelength selective switch and an add wavelength selective switch in each of an uplink and a downlink, and a drop wavelength selection in a downlink. A loopback function is achieved by connecting at least one of a switch port and an uplink add wavelength selection switch port, an uplink drop wavelength selection switch port, or a downlink add wavelength selection switch port. Is the first feature.

  In addition, the node configured using the wavelength selective switch according to the present invention includes one of the ports of the downlink drop wavelength selective switch, one of the ports of the uplink add wavelength selective switch, and the uplink. A second feature is that it has a loopback function by connecting at least one of the ports of the drop wavelength selective switch and one of the ports of the downlink add wavelength selective switch.

  In addition, the node configured using the wavelength selective switch according to the present invention includes a downlink drop wavelength selective switch port, an uplink add wavelength selective switch port, an uplink drop wavelength selective switch port, and a downlink. At least one of the drop wavelength selective switch port and the add wavelength selective switch port of the link is composed of a 1 × 2 switch and a 2 × 1 switch, respectively, and one port of the 1 × 2 switch The third feature is that a loopback function is provided by connecting one port of the 2 × 1 switch.

  Further, according to the present invention, a node configured using a wavelength selective switch is configured such that one port of the 1 × 2 switch and one port of the 2 × 1 switch are N × N switches (N is for a loopback function). The fourth feature is that the connection is made via the number of ports used).

  According to the present invention, there is provided an inter-node link connectivity confirmation method for confirming physical link connectivity between nodes in an optical network. The link connectivity confirmation light is transmitted from the one end side node of the link for which the connectivity is to be confirmed to the other end side node, and the link connectivity confirmation light returned by the loopback function of the other end side node is transmitted. The first characteristic is that the connectivity of the connectivity confirmation target link is confirmed by receiving the light.

  Also, an inter-node link connectivity confirmation method for confirming physical link connectivity between nodes configured using a wavelength selective switch according to the present invention is the above-described one-side node on the control plane. Transmitting a link connectivity confirmation message to the end node, and transmitting a link connectivity confirmation approval message from the other end node to the one end node on the control plane in response to the link connectivity confirmation message. The link connectivity confirmation light is transmitted from the one end side node to the other end side node on the data plane based on the reception of the link connectivity confirmation approval message, and the link is turned back at the other end side node. A step of receiving light for confirming the connectivity, and a light receiving state of the light for confirming the link connectivity received at the one end side node And a point to check the link connectivity between the determined said one end node to the other end node in the second feature a.

  Further, according to the present invention, the inter-node link connectivity confirmation method for confirming the physical link connectivity between nodes configured using the wavelength selective switch, the link connectivity confirmation message realizes a feedback function. The third feature is that it includes port designation information for designating a port to be performed.

  According to the present invention, the physical link connectivity between nodes configured using a wavelength selective switch can be easily confirmed using a loopback function provided to the nodes. According to this loopback function, the link connectivity can be confirmed simply by transmitting / receiving the link connectivity confirmation light at the node on one end side of the link connectivity confirmation target link. Therefore, an optical network system equipped with a link connectivity confirmation function is provided. Can be built economically.

  The present invention will be described below with reference to the drawings. FIG. 1 is a block diagram showing a configuration example of an optical network to which the present invention is applied. The optical network is constructed from a core core network (Transparent core network) 1 and networks 2-6.

  The core network 1 is a network having a long transmission distance, such as transmitting an optical signal between large cities, and its nodes 7 to 11 are configured using optical cross-connects.

  The networks 2 to 6 are networks with short transmission distances connected to the outside of the core net network 1, and the nodes 12 to 22 are configured using wavelength selective switches. The networks 2 to 5 are connected to the core net network 1 via nodes 8 to 11, respectively, and the network 6 is connected to the network 5 via a node 22. The networks 2 to 6 are constructed, for example, as metro rings in metropolitan areas.

  The control plane (Control plane) 23 includes a network operation management device, controls the nodes 7 to 22 based on information collected from the nodes 7 to 22 of the optical networks 1 to 6, and performs path setting. The control plane 23 also collects various control messages for confirming link connectivity and controls the nodes 7-22.

  In the present invention, the nodes 12 to 22 configured using the wavelength selective switch are provided with a loopback function, and the link connectivity can be confirmed using this as a return node.

  FIG. 2 is a block diagram showing a first embodiment of a node according to the present invention. Since the nodes 12 to 21 all have the same configuration, the node 12 will be described as a representative.

  The node 12 has a drop wavelength selection switch 26 and an add wavelength selection switch 27 on the uplink 24 that transmits an optical signal to the left side of the figure, and a drop wavelength selection switch 28 and an add on the downlink 25 that transmits the optical signal to the right side of the figure. A wavelength selective switch 29 is provided. The drop wavelength selective switches 26 and 28 drop a predetermined wavelength optical signal (s) in the WDM signal transmitted through the links 24 and 25 to the outside via an appropriate port, and add wavelength selective switches 27 and 29 Adds an optical signal of a predetermined wavelength from the outside to the links 24 and 25 via appropriate ports.

  The above is the same as FIG. The difference from FIG. 10 is that one port of the drop wavelength selective switch 26 and one port of the add wavelength selective switch 29 are connected, and one port of the drop wavelength selective switch 28 and one of the add wavelength selective switch 27 are connected. By connecting the ports, the loopback function at the node 12 is realized. According to both of these connections, loopback in both the upstream and downstream directions is possible. However, in a ring network or the like, connectivity of all links in the ring can be confirmed by only loopback in one direction. Therefore, only one of the connections may be used.

  In this embodiment, the port (1) of the drop wavelength selective switch 26 and the port (1) of the add wavelength selective switch 29 are connected, the port (1) of the drop wavelength selective switch 28 and the port (1) of the add wavelength selective switch 27 ) Are connected, and these ports are designated as loopback ports.

  The link connectivity confirmation light transmitted on the uplink 24 is dropped via the port (1) of the drop wavelength selective switch 26 and is added to the downlink 25 as it is via the port (1) of the add wavelength selective switch 29. Is done. Thus, a loopback function for looping back the link connectivity confirmation light at the node 12 is realized. Therefore, the link connectivity confirmation light is transmitted from the node on the one end side to check the link connectivity to the node on the other end side, and the link connectivity confirmation light received by the loopback function of the node on the other end is received. By determining the level, link connectivity between nodes can be confirmed. Note that light of a wavelength not used in the link is used as the link connectivity confirmation light.

  FIG. 3 is a block diagram showing a second embodiment of the node according to the present invention. 3, the same or equivalent parts as in FIG. 2 are denoted by the same reference numerals. In the present embodiment, each port of the drop wavelength selective switches 26 and 28 is a 1 × 2 switch, and each port of the add wavelength selective switches 27 and 29 is a 2 × 1 switch. The 1x2 switch has one input port and two output ports (first output port and second output port), and the input port is normally connected to the first output port side, but the second output This switch can be switched to the port side. The 2 × 1 switch has two input ports (first input port and second input port) and one output port. Normally, the first input port is connected to the output port side. It is a switch that can be connected by switching two input ports to output ports. FIG. 3 shows a case where all the ports of the drop wavelength selective switches 26 and 28 are 1 × 2 switches and all the ports of the add wavelength selective switches 27 and 29 are 2 × 1 switches. Some may be 1 × 2 switches or 2 × 1 switches.

  As shown by the broken line in FIG. 3, the drop wavelength selection switch 26 is connected to the second output port of the 1 × 2 switch and the second input port of the 2 × 1 switch of the add wavelength selection switch 29 to select the drop wavelength. The second output port of the 1 × 2 switch of the switch 28 and the second input port of the 2 × 1 switch of the add wavelength selective switch 27 are connected to each other.

  Normally, the drop wavelength selective switches 26 and 28 drop the WDM signal and transmit it in the optical network, and the add wavelength selective switches 27 and 29 add the WDM signal and transmit it in the optical network. When the node 21 is used as the return node of the connectivity check target link, an appropriate 1 × 2 switch and 2 × 1 switch are switched. This realizes a loopback function of dropping link connectivity confirmation light, adding it as it is, and looping back.

  FIG. 4 is a block diagram showing a third embodiment of the node according to the present invention. 4, the same reference numerals are given to the same or equivalent parts as in FIG. This embodiment is the same as FIG. 3 in that each port of the drop wavelength selective switches 26 and 28 is a 1 × 2 switch and each port of the add wavelength selective switches 27 and 29 is a 2 × 1 switch. 2nd output port of 1 × 2 switch of wavelength selective switch 26 and 2nd input port of 2 × 1 switch of add wavelength selective switch 29, 2nd output port of 1 × 2 switch of drop wavelength selective switch 28 and add wavelength selection The second input port of the 2 × 1 switch of the switch 29 is connected via N × N switches 30 and 31, respectively. In the present embodiment, the connection relationship between the drop-side port and the add-side port can be changed by changing the connection of the N × N switches 30 and 31. N is the number of ports used for link connectivity confirmation in the drop wavelength selective switches 26 and 28 and the add wavelength selective switches 27 and 29. The drop wavelength selective switches 26 and 28 and the add wavelength selective switches 27 and 29 It may be the number of all ports that have.

  FIG. 5 is a block diagram showing a fourth embodiment of the node according to the present invention. In the third embodiment, an N × N switch is provided for each set of add and drop, but in this embodiment, one 2N × 2N switch is provided for two sets of add and drop. It is. Functionally the same as the embodiment of FIG.

  As shown in FIG. 6, the node 22 of FIG. 1 includes a total of eight wavelength selective switches 26 to 29, 26 'to 29', four on the network 5 side and four on the network 6 side. In this case, the transmission of the WDM signal and the link connectivity confirmation light between the networks 5 and 6 is the same as the conventional optical signal delivery. In this case, the loop-back function at the wavelength selective switches 26 'to 29' on the network 6 side may not be provided.

  FIG. 7 is a flowchart showing an operation in an embodiment of the link connectivity confirmation method according to the present invention. This flowchart is mainly for the start-end node when checking the physical link connectivity between the start-end node and the return node. Shows the operation.

  First, it is checked whether there is a wavelength that can be used for link connectivity confirmation between the start node and the return node (S70). The wavelength used in the network can be found from information collected by the network operation management device of the control plane. The wavelength used for communication between the start node and the return node cannot be used in the link connectivity confirmation.

  If there is no wavelength that can be used for link connectivity confirmation, for example, because it is used for actual communication, the process ends without checking the link connectivity, but there are wavelengths that can be used for link connectivity confirmation. For example, one wavelength is selected from them, and link connectivity confirmation using the wavelength is started (S71). At the same time, from the start to the end of the link connectivity confirmation, the wavelength used in the link connectivity confirmation is made unusable for communication on the link between the start node and the return node. That is, the link between the start node and the return node cannot be used for communication of the wavelength used in the link connectivity confirmation.

  In the link connectivity confirmation, first, a link connectivity confirmation message is transmitted from the start node to the return node on the control plane and a response is requested (S72). The link connectivity confirmation message includes information necessary for performing loopback between the start node and the return node, such as the node IDs of the start node and the return node. 3 to 5, the port confirmation information (port number) is included in the connectivity confirmation message to designate the port for returning the link connectivity confirmation light. When the return node is the embodiment of FIG. 2, the port for returning the link connectivity confirmation light is dedicated, and therefore the port to be looped back is not designated.

  The return node receives the link connectivity confirmation message, and returns a link connectivity confirmation approval message to the start node as a response to the link connectivity confirmation message if a port for returning the link connectivity confirmation light is available. A link connectivity confirmation approval message is also transmitted and received on the control plane. Further, when the return node is the embodiment shown in FIGS. 3 to 5, switching is performed so that the loopback function is realized.

  If the return node cannot use the port for returning the specified link connectivity confirmation light, it returns a link connectivity confirmation disapproval message to the start node as a response to the link connectivity confirmation message.

  The start node determines whether or not a link connectivity confirmation approval message has been received (S73), and when a link connectivity confirmation approval message is received, transmits link connection confirmation light to the return node on the data plane. (S74). This link connectivity confirmation optical signal is an optical signal having the wavelength selected in S61. If the start node does not receive a link connectivity confirmation approval message (link connectivity confirmation disapproval message is received), it sends a link connectivity confirmation end message (S78), and then sends a link connectivity confirmation end approval message. Receive (S79) and end the link connectivity confirmation.

  If there is no failure in the physical link connectivity between the start node and the return node, the return node loops back the link connectivity confirmation light to the start node by the loop back function.

  The start node determines the light reception level of the link connectivity confirmation light looped back by the loopback function at the return node (S75). The light reception level can be determined by comparing the light reception level with a preset threshold value and determining whether the light reception level is equal to or higher than the threshold value.

  If the light reception level of the link connectivity confirmation optical signal is determined to be equal to or greater than the threshold value in S75, the link connectivity between the start node and the return node is normal (no failure) (S76) is less than the threshold value. If it is determined that there is an abnormality (failure present) (S77).

  When confirmation of the physical link connectivity between the start node and the return node is completed as described above, a link connectivity check end message is transmitted from the start node to the return node on the control plane and a response is requested. (S78).

  When the return node receives the link connectivity confirmation end message, it returns a link connectivity confirmation end approval message to the start node on the control plane as a response thereto. Further, in the case of the embodiment shown in FIG. 3 to FIG. 5, the folding node is switched so that the loopback function realized so far is released. When the start node receives the link connectivity confirmation end approval message (S79), it ends the link connectivity confirmation (S80).

  FIG. 8 is a diagram conceptually showing link connectivity confirmation according to the present invention. The optical network 80 has a configuration in which nodes 81 to 88 configured using a wavelength selective switch are connected in a ring shape with a bidirectional transmission path (optical fiber). Here, when the physical link connectivity between the nodes 81 and 85 is confirmed using the node 81 as the start node and the node 85 as the return node, various messages such as the above link connectivity confirmation message are transmitted and received on the control plane. Thus, a loop is formed in which the node 81 is a start node and the node 85 is a folded node.

  Thereafter, the link connectivity confirmation light is transmitted from the node 81 to the node 85, and the link connectivity confirmation light looped back at the node 85 is received by the node 81. Then, based on the light reception level of the link connectivity confirmation light received at the node 81, the presence / absence of a failure in the link between the nodes 81 and 85 is determined. By performing inter-link connectivity confirmation as described above by sequentially changing the nodes, it is possible to identify the location where the failure has occurred. Such link connectivity confirmation is not limited to between nodes in one network, but can be performed between nodes across a plurality of networks.

  Although the embodiment has been described above, the present invention is not limited to the above-described embodiment, and can be variously modified. For example, in the above embodiment, the light receiving bell of the light that has been looped back is determined to check whether there is a link failure. However, if a plurality of wavelengths are used for the link connectivity confirmation light, together with the link failure for the wavelength Link characteristics can be examined. The present invention is also applicable to a wavelength cross-connect device configured using a wavelength selective switch.

It is a block diagram which shows the structural example of the optical network to which this invention is applied. It is a block diagram which shows 1st Embodiment of the node which concerns on this invention. It is a block diagram which shows 2nd Embodiment of the node which concerns on this invention. It is a block diagram which shows 3rd Embodiment of the node which concerns on this invention. It is a block diagram which shows 4th Embodiment of the node which concerns on this invention. It is a block diagram which shows the structure of the node provided with eight wavelength selection switches. It is a flowchart which shows the operation | movement in one Embodiment of the link connectivity confirmation method which concerns on this invention. It is a figure which shows notionally the link connectivity confirmation by this invention. It is a conceptual diagram which shows the link connectivity confirmation method between the conventional nodes. It is a block diagram which shows the conventional node structure comprised using the wavelength selective switch.

Explanation of symbols

1-6 ... Optical network, 7-22,81-88,91,92 ... Node, 23 ... Control plane, 24,25 ... Link, 26-29, 26'-29 ' ..Wavelength selective switch, 30, 31 ... NxN switch, 32 ... 2Nx2N switch, A, B ... Client device, C, D ... Optical transceiver

Claims (7)

In a node configured with a wavelength selective switch,
A drop wavelength selection switch and an add wavelength selection switch are provided for each of the uplink and downlink,
By connecting at least one of a downlink drop wavelength selection switch port and an uplink add wavelength selection switch port, an uplink drop wavelength selection switch port, and a downlink add wavelength selection switch port, A node characterized by having a loopback function.   One of the ports of the downlink drop wavelength selection switch and one of the ports of the uplink add wavelength selection switch, one of the ports of the uplink drop wavelength selection switch, and the port of the downlink add wavelength selection switch The node according to claim 1, wherein at least one of them has a loopback function by being connected.   Downlink drop wavelength selection switch port and uplink add wavelength selection switch port, uplink drop wavelength selection switch port and downlink add wavelength selection switch port, at least one drop wavelength selection switch port And add wavelength selective switch ports are composed of 1 × 2 switch and 2 × 1 switch, respectively, and one port of the 1 × 2 switch and one port of the 2 × 1 switch are connected to each other. The node of claim 1, comprising:   The one port of the 1 × 2 switch and one port of the 2 × 1 switch are connected via an N × N switch (N is the number of ports used for the loopback function). The node according to 3. In the inter-node link connectivity confirmation method for confirming physical link connectivity between nodes in an optical network,
An optical network is configured by the nodes according to any one of claims 1 to 4, wherein link connectivity confirmation light is transmitted from one end side node of the connectivity check target link to the other end side node, and the other end side. An inter-node link connectivity confirmation method comprising: confirming connectivity of a link for which connectivity is to be confirmed by receiving link connectivity confirmation light returned by a loopback function of the node. Sending a link connectivity confirmation message from the one end side node to the other end side node on the control plane;
Transmitting a link connectivity confirmation approval message from the other end side node to the one end side node on the control plane in response to the link connectivity confirmation message;
Link connectivity confirmation light is transmitted from the one end side node to the other end side node on the data plane based on the reception of the link connectivity confirmation approval message, and is returned at the other end side node. Receiving a confirmation light;
6. The link connectivity confirmation light received at the one end side node is determined to check the link connectivity between the one end side node and the other end side node. The link connectivity confirmation method described.   The node is configured by the node according to claim 3 or 4, and the link connectivity confirmation message includes port designation information for designating a port for realizing a feedback function. Link connectivity confirmation method.

Images