JP2006311254A - Network system - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a network system capable of relieving a wavelength path even when a node failure occurs and maintaining communication through the wavelength path with high reliability as the entire network. <P>SOLUTION: An optical network is composed of a plurality of stations. Each station is provided with an optical cross-connector (OXC) 12-1, 12-2 accommodating respective client devices 14-1 to 14-4. At least one station of the plurality of stations is provided with a plurality of optical cross-connectors 12-1, 12-2 to be subjected to a node redundance configuration. An optical switching circuit in the optical cross-connectors 12-1, 12-2 and an optical interface card are subjected to a redundance configuration. A node to be an initiator of a wavelength path automatically searches for a preliminary path that is alternated in a station unit about parts other than an adjacent node and a node just before the last hop when counting a preliminary path route other than a current path route. <P>COPYRIGHT: (C)2007,JPO&INPIT

Description

  The present invention relates to a network system, and more particularly to a network system capable of improving the reliability of a wavelength path in an optical network.

  The optical network is composed of routers, optical cross-connect devices (hereinafter referred to as OXC), wavelength division multiplexing devices (hereinafter referred to as WDM), and the like. FIG. 8 and FIG. 9 show configuration examples of the optical network and each station. Here, the optical network is composed of WDM links (fibers) connecting the stations 1 to 6 and the stations. Each station includes OXC and WDM that accommodate client devices via a router. The client device is a user device or an Ethernet (registered trademark) switch.

  The OXC is a device that switches the direction of light with all light using an optical switch circuit. The optical switch circuit is manufactured using, for example, a MEMS (Micro Electro Mechanical System) technology. The reliability of the OXC is dominated by the reliability of the optical switch circuit. Therefore, in order to increase the reliability of the wavelength path in the optical network, the reliability of the optical switch circuit of the OXC may be increased.

  Non-Patent Document 1 describes that the optical switch circuit in the OXC is made redundant to improve the reliability of the wavelength path in the optical network.

Non-Patent Document 2 describes the use of a passive optical circuit in a selection unit of an optical switch circuit when making the optical switch circuit redundant. The reliability can be improved by making the optical circuit particularly passive.
R. Lingampalli, et al, pp. 2159-2167, NFOEC, 2002. M. Hayashi, et al, IEEE Journal of Lightwave Technology, pp. 356-364, Vol. 21, Feb., 2002.

  According to the prior art, even if a failure occurs in the optical switch circuit provided in the OXC, the wavelength path can be relieved inside the apparatus by switching and using a healthy optical switch circuit. As described above, if the optical switch circuit failure, which is one of the least reliable devices in the apparatus, is remedied, the wavelength path can be remedied in many cases of hardware failure. .

  However, the conventional technology only considers hardware failure of OXC, and does not have a design that considers reliability against software failure.

  OXC is equipped with GMPLS (Generalized MultiProtocol Label Switching) protocol and includes many router-like functional elements such as routing and signaling protocols. Compared to SDH ADM equipment, The software that operates is much more complicated. For this reason, there is a high probability that the software of the OXC node itself will be abnormal, such as a so-called node failure.

  It is desirable to realize a node configuration capable of coping with such a software failure, and to improve reliability not only for a hardware failure but also for a software failure that governs the operation of the node itself.

  An object of the present invention is to provide a network system capable of relieving a wavelength path even when a node failure occurs, and maintaining communication of the wavelength path with high reliability as a whole network.

  In order to solve the above-described problem, the present invention is a network system including an optical cross-connect device that includes a plurality of stations, and each station accommodates a client device. At least one of the plurality of stations includes a plurality of stations. The first feature is that the optical cross-connect device is configured to be node redundant.

  The second feature of the present invention is that a client device accommodated in at least one of the plurality of stations is connected to each of the plurality of optical cross-connect devices.

  The third feature of the present invention is that the optical switch circuit inside the optical cross-connect device has a redundant configuration.

  In addition, the present invention has a fourth feature in that the optical interface card inside the optical cross-connect device has a redundant configuration, and the client device is connected to each of the optical interface cards.

  Further, the present invention provides a backup path in which a node other than the adjacent node and the node before the last hop is detoured in units of stations when the node serving as the wavelength path initiator calculates the backup path path in addition to the working path path. The fifth feature is that the search is automatically performed.

  In addition, the present invention has a sixth feature in that when the backup path is automatically searched, SRLGs of the adjacent node and the node before the last hop are not considered.

  In addition, the present invention has a seventh feature in that, when automatically searching for the backup path, prioritization of route search conditions is performed using different SRLG ranges.

  According to the present invention, the stations constituting the network have a plurality of optical cross-connect devices and are configured in a node redundant configuration. Therefore, even when a node software failure, that is, a so-called node failure occurs, a wavelength path is set. Can be rescued. In addition to node failures, the reliability of failures inside optical cross-connect devices is enhanced by the connection configuration from client devices to optical cross-connect devices and the redundant configuration of optical switch circuits and optical interface cards inside optical cross-connect devices. be able to.

  The present invention will be described below with reference to the drawings. FIG. 1 is a block diagram showing the basic configuration of each station in the network system according to the present invention. As shown in the figure, each station has routers 11-1, 11-2, OXCs 12-1, 12-2 that accommodate client devices 14-1 to 14-4 via routers 11-1, 11-2, and Equipped with WDM13-1 to 13-3.

  Here, the OXC node is made redundant (duplex) in order to cope with a node failure. This redundancy may be performed at a particularly problematic station and need not be performed at all stations. The router nodes are also redundant. Then, the devices are connected so that they can be used in appropriate combinations, and the subordinate client devices 14-1 to 14-4 are connected to one of the routers 11-1, 11-2, OXC12-1, 12 -2 and WDM13-1 to 13-3 are used to communicate with the other device via fiber, so that when OXC12-1,12-2 node failure occurs and routers 11-1,11 When a failure occurs in -2, the wavelength path can be relieved as a network.

  For example, as shown in FIGS. 2 to 4, there are various forms of connection from the OXC 12-1, 12-2 to the client devices 14-1 to 14-4 and the internal configuration of the OXC 12-1, 12-2. It can be in the form. In any form, since the OXC node is made redundant, the fault tolerance against the node failure caused by the OXC software failure can be kept high. Which form is adopted may be determined in consideration of the required reliability and the complexity of the configuration.

  FIG. 2 is a block diagram showing the first embodiment. The first form is a configuration in which the optical interface card (denoted as O-O-O in the figure) and the optical switch circuit (denoted as Switch fabric in the figure) of OXC12-1, 12-2 are not made redundant. When a node failure due to one OXC software failure occurs, the wavelength path is relieved by using the other OXC. In this configuration, since the redundancy inside the apparatus is not made as much as possible, the reliability of the single OXC from the hardware side is lowered, but the configuration can be simplified.

  FIG. 3 is a block diagram showing the second embodiment. The second configuration is a configuration in which only the optical switch circuit (Switch fabric) of OXC 12-1 and 12-2 is made redundant. Compared to the first configuration, this configuration makes the internal connection of the device more complex, but it can handle the failure of the optical switch circuit inside the device by itself, so that the reliability of the OXC alone is improved. Can do.

  FIG. 4 is a block diagram showing the third embodiment. In the third embodiment, the optical interface card (O-O-O) is made redundant in addition to the optical switch circuit (Switch fabric) of the OXC 12-1, 12-2. In this configuration, the failure of the optical interface card can be dealt with by the device alone, so that the reliability of the OXC alone can be greatly improved. However, the configuration is complicated such that the interfaces of the routers 11-1 and 11-2 are increased.

  As described above, by making the OXC node redundant and OXC internal redundant, it is possible to improve the reliability in network operation. Hereinafter, network operation will be described by taking the configuration shown in FIG. 5 as an example. In FIG. 5, WDM is omitted for the sake of simplicity. Also, the same or equivalent parts as in FIG.

  The network in this configuration example includes stations A to E. Each station A to E has OXC12-1 and 12-2, 52-1 and 52-2, 53-1 and 53-2, 54-1 and 54-2, 55-1 and 55-2, respectively. The node is made redundant. Assume that each OXC has a redundant configuration. Stations A and C are connected to redundant routers 11-1 and 11-2 and 51-1 and 51-2, respectively. The router is generally accommodated in the station together with the OXC, but here it is shown outside the station. Further, the client apparatuses 14-1 to 14-4 are connected to the routers 11-1 and 11-2, and the client apparatuses 56-1 to 56-4 are connected to the routers 51-1 and 51-2. In the following, the routers 11-1, 11-2, 51-1, 51-2 are assumed to be nodes 1, 2, 3, 4; the node 1 is assumed to be an initiator; and the node 3 is assumed to be a destination.

  For example, when the wavelength path is set in the route from node 1 to station OXC12-1 to station B OXC52-1 to station C OXC53-1 to node 3, OXC12-1,52-1, The internal failure of 53-1 can be handled by the redundant configuration inside those OXCs. Also, for a node failure of OXC12-1,52-1,53-1, a route that bypasses the OXC that caused the node failure, for example, node 1 to OXC12-2 of station A to OXC52-2 of station B This can be dealt with by switching to the detour route from station OXC53-2 to node 3. If it is a node failure of OXC52-1, it is possible to deal with a detour route that passes through OXC54-1 or 54-2 of station D, and the detour route in this case was switched because the node OXC node has a redundant configuration Reliability is also high.

  In the above network operation, if a station itself becomes a failure due to a power failure, disaster, etc., all the OXC nodes housed in the station will be unusable, so the failure cannot be remedied. The case happens.

  In order to cope with such a failure, it is only necessary to automatically search for the working and backup path routes as follows. Note that the backup path is used as a detour route when a failure occurs in a station on the working path route and the like cannot be repaired by redundancy within the OXC and OXC.

  Different SRLG (Shared link risk group) values are assigned to the links such as the nodes 1 to 4, the stations A to E, the apparatuses, and the stations. Nodes, stations, and links may be grouped, and SRLG values may be assigned to each group. Regarding SRLG, draft-ietf-ccamp-gmpls-routing-0.9.txt, IETF describes the standardization. Also, draft-ietf-ccamp-ospf-gmpls-extensions-12.txt describes the bit assignment. According to this, the SRLG value is assigned 32 bits and can take the maximum value 4294967296.

  Node 1, which is the initiator of the wavelength path (LSP), calculates the working and protection path routes so as to pass through routes having different SRLG values, that is, routes having no matching SRLG value. However, since there is no room for selection in the adjacent node (the station A next to the nodes 1 and 2) and the node before the last hop (the station C before the nodes 3 and 4), the SRLG values still match. It is impossible to calculate the working and protection path routes so that there is no such thing.

In order to make this possible, for example, the following method 1 or 2 is adopted.
(Method 1) A method in which the SRLG value is not considered for the adjacent node and the portion of the node before the last hop.
(Method 2) A method for prioritizing route search conditions using different SRLG value ranges. That is, of the 32-bit SRLG values, the values in the ranges A to B are used for the fiber (link), the values in the ranges C to D are used for the nodes, and the values in the ranges E to F are used for the stations. To do. Then, a number that is most easily secured as a different route, for example, a fiber number is given to the fiber. When route calculation is performed, priority is given to the substitution (Diosjoint) property of the part assigned with the young number. Also, if the alternative route cannot be calculated for the part (station) to which E to F are assigned, it is ignored.

  For example, if node 1 to station OXC12-1 to station B OXC52-1 to station C OXC53-1 to node 3 are set as working path routes, node 1 to station A OXC12-1 to station D A backup path route is set from OXC54-1 to OXC53-1 to node 3 of station C. OXC12-1,52-1,53-1 internal failure in the working path route can be handled by the internal redundant configuration of OXC, and OXC52-1 of station B and the failure of station B itself are spare Can be handled by switching to a path route. In this case, the OXC inside the backup path route also has a redundant configuration, and since the node OXC has a redundant configuration in the station D, the reliability when switched to the backup path route is high.

  It is also possible to set backup path routes from node 1 to OXC 12-2 of station A to OXC 55-1 of station E to OXC 53-2 of station C to node 3. In this case, a failure inside OXC12-1,52-1,53-1 in the working path route can be handled by a redundant configuration inside those OXCs, and OXC12-1,52- of stations A, B, C The node failure of 1,53-1 and the failure of the station B itself can be dealt with by switching to the backup path route.

  In addition, connections between OXCs can take various forms within the OXC network. Hereinafter, the connection form between OXCs will be described with reference to FIGS. FIG. 6A is a conceptual diagram of a connection form in which the OXC network is divided into A and B planes, in which the redundant OXCs of stations A and B are not connected. Each of the A plane and the B plane includes OXCs of stations other than the stations A and B, and they may have a node redundant configuration. In this way, if the OXC network is divided into the A side and the B side, it is possible to prevent a failure in one side of the OXC from affecting the other side.

  FIGS. 6B and 6C are conceptual diagrams of a form in which redundant OXCs are connected between stations or within the same station. In this connection mode, OXCs redundant in stations A and B are connected between OXCs in stations A and B, so one failure may affect the entire network. It is possible to increase the number of wavelength path relief paths for obstacles.

  FIG. 7 is an explanatory diagram of the effect of the node redundant configuration according to the present invention. (A) shows the reliability when the node configuration is made redundant and the optical switch circuit inside the OXC is made redundant (Fig. 3), (b) shows the reliability when the node configuration is not made redundant, and the horizontal axis shows The reliability [FITs] of the optical switch circuit, and the vertical axis is the outage [second / year] of the wavelength path (time that cannot be serviced in one year).

  The annual outage of the wavelength path is about 160 seconds (Figure 6 (b)) when the node configuration is not made redundant, whereas it is 0.01 seconds or less when the node configuration and the optical switch circuit are made redundant. (FIG. 7 (a)) can be obtained (in FIG. 7 (a), it is shown substantially overlapping the horizontal axis). By making the OXC node redundant, for example, even when the OXC routing process fails, the wavelength path can be bypassed via another OXC to which the client device is connected.

It is a block diagram which shows the basic composition of each station of the network system which concerns on this invention. It is a block diagram which shows the 1st form of the internal structure of OXC. It is a block diagram which shows the 2nd form of the internal structure of OXC. It is a block diagram which shows the 3rd form of the internal structure of OXC. It is a block diagram which shows an example of the network structure to which this invention was applied. It is a figure which shows the connection form between OXC. It is explanatory drawing of the effect by this invention. It is a block diagram which shows the structure of an optical network. It is a block diagram which shows the structure of each station.

Explanation of symbols

11-1,11-2,51-1,51-2 ・ ・ ・ Router, 12-1,12-2,52-1,52-2,53-1,53-2,54-1,54- 2,55-1,55-2 ・ ・ ・ Optical cross-connect equipment (OXC), 13-1 to 13-3 ・ ・ ・ Wavelength division multiplexing equipment (WDM), 14-11 to 14-4,56-1〜 56-4 ・ ・ ・ Client device,

Claims (7)

In a network system comprising an optical cross-connect device that is composed of a plurality of stations and each station accommodates a client device,
A network system, wherein at least one of the plurality of stations includes a plurality of optical cross-connect devices and is configured in a node redundant manner. 2. The network system according to claim 1, wherein a client device accommodated in at least one of the plurality of stations is connected to each of the plurality of optical cross-connect devices. The network system according to claim 1, wherein the optical switch circuit inside the optical cross-connect device has a redundant configuration. 4. The network system according to claim 3, wherein the optical interface card in the optical cross-connect device has a redundant configuration, and the client device is connected to each of the optical interface cards. When calculating the backup path route in addition to the working path route, the node that is the initiator of the wavelength path automatically searches for a backup path that is detoured for each station, except for the adjacent node and the node before the last hop. The network system according to claim 1, wherein the network system is characterized in that: 6. The network system according to claim 5, wherein when automatically searching for the backup path, SRLGs of an adjacent node and a node before the last hop are not considered. 6. The network system according to claim 5, wherein when the backup path is automatically searched, the route search condition is prioritized by using the SRLG range properly.

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