JP3825341B2 - Optical path construction method - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention provides a new optical path necessary for realizing a cooperative operation between a large-capacity optical path network realized by an optical cross-connect device and a service network realized by a Layer 2/3 switch such as an IP router. Regarding the method.
[0002]
[Prior art]
Due to an increase in data communication traffic such as the Internet, the introduction of node devices having a throughput of Tbit / s at present and 10 to 100 Tbit / s or more in the near future is being promoted. As means for realizing a node device having such a large-scale transfer capability, a packet switch (PSC) that processes TCP / IP packets, which are the mainstream communication protocol on the Internet, and an optical path routing process Photonic routers that operate in cooperation with optical switches (LSC: Lambda Switch Capable) [Reference: k. Shimano, A. Imaoka, Y. Takigawa, and K.-l. Sato, in Technical Digest of NFOEC'2001, Vol. .1 p. 5, July.2001. By using this photonic router, a conventional IP network composed of packet switches (PSC) and a high-capacity optical path network composed of optical switches (LSC) (hereinafter referred to as optical networks) are more densely packed. It becomes possible to link.
[0003]
[Problems to be solved by the invention]
However, when such an IP network and an optical network are operated in cooperation using such a node device, a method of newly establishing an autonomous optical path is an important point in effectively utilizing network resources. However, research on the construction of a network in which the lower network (IP network) and the upper network (optical network) both operate dynamically and autonomously distributed and link them together has recently started. However, a method of dynamically establishing a new optical path following packet traffic fluctuation has not been put into practical use.
[0004]
The present invention is to solve the above-described problems, enable a new dynamic optical path according to the packet traffic accommodation request, and an optimal optical path according to the load state of the network. Objective.
[0005]
[Means for Solving the Problems]
In order to solve the above problems, the first invention is an optical path link and a packet switch. When A packet network, and a fiber link and an optical switch accommodating the packet network When Optical network consisting of A new optical path in a multi-layer network consisting of Accommodating specific ground-to-ground packet traffic Is changed according to the priority of two traffic, low priority traffic and high priority traffic. By searching for a route that minimizes the optical path link cost as seen from the packet network, While this is only done when the packet traffic cannot reach the destination on the existing optical path, it searches for a route that minimizes the fiber link cost seen from the optical network for high-priority traffic. This is the first time an optical path is newly established when it is impossible to reach the destination with the existing optical path on the packet traffic route. It is characterized by performing.
[0007]
The second invention is an optical path link and a packet switch. When A packet network, and a fiber link and an optical switch accommodating the packet network When Optical network consisting of A new optical path in a multi-layer network consisting of Accommodating specific ground-to-ground packet traffic The low-priority traffic and the high-priority traffic are changed according to the priority of the two traffics, and for the low-priority traffic, a route that minimizes the optical path link cost seen from the packet network is searched. The optical path is newly established only when the packet traffic cannot reach the destination with the existing optical path within the predetermined number of hops. Minimized fiber link cost from the viewpoint of optical network The new path is established by searching for routes. Pre-defined When it is impossible to reach the destination with existing optical paths within the number of hops First time It is characterized by performing.
[0010]
DETAILED DESCRIPTION OF THE INVENTION
A configuration example of a network system according to an embodiment of the present invention is shown in FIG. This embodiment is composed of a packet network 7 constituted by an optical path link formed by a packet switch 2 and an optical path 4 (4 ′), and an optical network 8 constituted by a fiber link constituted by an optical switch 3 and a fiber 5. This assumes a multi-layer network. The packet network 7 is a packet / cell switch network, and is an IP network in the case of the Internet. In the figure, 4 is the optical path (link) of the path through which the signal actually flows, and 4 'represents the link of the optical path as viewed from the packet network. 6 represents traffic.
[0011]
Such a multi-layer network can be configured by the photonic router 1 (1-1 to 1-4) in which the packet switch 2 and the optical switch 3 are integrally mounted.
[0012]
As shown in FIG. 2, the photonic router 1 includes a packet switch 2 and an optical switch 3, and an integrated control device (GMPLS controller) 10 that integrally manages them. Control signals are exchanged between the integrated control devices 10 of the photonic routers 1 through control signal lines.
[0013]
The optical switch 3 is a 128 × 128 switch, and has an ability to input / output four fiber links multiplexed with 32 wavelengths of optical paths. The transmission speed of each optical path is 2.5 Gbit / s and is terminated at the SONET OC-48 interface.
[0014]
The control signal line is composed of a SONET OC-3 line having a transmission rate of 155 Mbit / s, and the control signal propagating through this line is, for example, OSPF / IS-IS for acquiring the network topology of the photonic router network. Protocol packets, RSVP-TE / CR-LDP protocols for setting / releasing optical paths set between packet switches, and LMP (Link Management Protocol) packets for monitoring failure of each fiber link.
[0015]
Therefore, the integrated control device 10 of each photonic router 1 has a function unit for processing these control signal protocols, a routing processing function unit (OSPF / IS-IS protocol processing function) 20, an optical path setting management function. Unit (RSVP-TE / CR-LDP protocol processing function) 30, optical fiber and link failure management function unit (LMP protocol processing function) 40 of the adjacent node.
[0016]
The routing processing function unit 20 includes a flooding unit 21, a link state database (DB) 22, an extended link state database (DB) 23, a switching capability monitoring unit 24, a route calculation unit 25, And a next hop database (DB) 26.
[0017]
The flooding unit 21 is a functional unit that notifies link state information collected from its own node and other nodes to adjacent nodes. The link state DB 22 and the extended link state DB 23 are databases that hold link information collected from other nodes. The optical state of the optical path link is stored in the link state DB 22, and the fiber link state is stored in the extended link state DB 23. Information is stored.
[0018]
Here, the optical path link state information stored in the link state DB 22 is specifically free information and cost information of an optical path link that connects two packet switches and is accommodated in a fiber link. Further, the fiber link state information stored in the extended link state DB 23 is, specifically, free information and cost information of the fiber link connecting the two optical switches.
[0019]
The switching capability monitoring unit 24 is a functional unit that monitors the switch state of the own node. For example, if the switch of the own node has not only the function of setting the optical path to the optical switch 3, but also the capacity to accommodate the optical path in the packet switch 2, the switching capability of the packet switch / optical switch exists. Is advertised to other nodes.
[0020]
The route calculation unit 25 calculates a transfer route of an optical path (OLSP) set from the link state DB 22 and a logical path (LSP) switched by the packet switch 2 or a packet.
[0021]
The next hop DB 26 is a database in which the result of route calculation is stored, and stores information such as which interface the packet should be transferred to reach each node.
[0022]
The optical path setting management function unit 30 has a path database (DB) 31 in which optical path information is stored, and a path setting deletion function unit 32 for setting / deleting an optical path. The link failure management function unit 40 also monitors a link / adjacent node state database (DB) 41 having state information of optical fibers and adjacent nodes, and detects advertisement information from other nodes to detect link failures. It has a signal processing function unit 42.
[0023]
The above-described routing processing function unit 20 defines link costs for each layer network. That is, the routing processing function unit 20 defines the cost of a fiber link connecting two optical switches and the cost of an optical path link connecting two packet switches and accommodated in the fiber link. Based on these costs, the cost of the optical path accommodated in the fiber link and the transfer cost of the packet traffic accommodated in the optical path link are calculated by the Dijkstra algorithm, and the packet traffic is between the start point and the end point of the traffic. Transfer processing is performed with a route that minimizes the sum of costs, and an optical path is set with a route with the minimum cost in the set start point-end point section.
[0024]
Here, the cost of the fiber link is assigned using values such as the distance of each fiber section, the reciprocal of the capacity of the fiber link (the reciprocal of the number of optical paths that can be accommodated), or the cost required for actual construction. On the other hand, the cost of an optical path link set between two packet switches is calculated by using the reciprocal of the transmission speed of each optical path, or the product of the sum of the fiber link costs for accommodating the optical path and a constant. Assigned. As described above, the cost of the fiber link and the optical path link on the same route is generally defined by different values.
Hereinafter, it relates to the present invention. element Form of implementing technology State and To explain.
[0025]
[Embodiment 1]
In this embodiment, when a request for accommodation of specific ground-to-ground packet traffic occurs in the network as shown in FIG. 1, first, the shortest path (minimum optical path link cost path) viewed from the packet network 7 is searched. When it is possible to reach the destination with the existing optical path, packet traffic is accommodated along the route, and when it is impossible, a new optical path is established.
[0026]
FIG. 3 is a diagram for explaining the first embodiment, and FIG. 4 is a flowchart of the first embodiment.
[0027]
In FIG. 3, each of the photonic routers 1-1 to 1-5 will be described as Node # 1 to Node # 5. The same applies to other embodiments described later. OLSP # 1 is an optical path connecting Node # 1 and Node # 4, OLSP # 2 is an optical path connecting Node # 4 and Node # 5, and OLSP # 3 is an interface between Node # 5 and Node # 3. The connecting optical path, OLSP # 4, is an optical path connecting Node # 1 and Node # 2, and OLSP # 5 is an optical path connecting Node # 1 and Node # 3.
[0028]
The cost of the optical path link is “10” for OLSP # 1 to OLSP # 4 and “40” for OLSP # 5, respectively.
[0029]
The cost of the fiber link is “50” between Node # 1 and Node # 2, between Node # 2 and Node # 3, between Node # 1 and Node # 4, and between Node # 4 and Node # 5. , Node # 5 and Node # 3 are “20”.
[0030]
For example, if a packet traffic accommodation request is generated between Node # 1 and Node # 3, a route that minimizes the optical path link cost of the existing optical path connecting Node # 1 and Node # 3 is searched. (Step S11). If there is no route to the end node (Node # 3) in the existing optical path, that is, if the cost to the end node is infinite, the process proceeds to step S14. If there is a route, the packet traffic is accommodated in the optical path of the search route, and the packet is transferred (step S13).
[0031]
If there is no optical path that reaches Node # 3, a route that has the lowest cost from Node # 1 to Node # 3 including the fiber link is searched (step S14). If the route is found (step S15), an optical path is newly established in the route, packet traffic is accommodated in the newly established optical path, and the packet is transferred (step S16). If there is no route to the end node (Node # 3) even if the fiber link is included, that is, if the cost to the end node is infinite, the packet transfer is blocked or the packet is discarded (step S17).
[0032]
With the process shown in FIG. 4, the packet traffic is accommodated in the example shown in FIG. That is, as the optical path link from Node # 1 to Node # 3, there are a route of Node # 1- # 4- # 5- # 3 and a route of Node # 1- # 3 (via # 2). The optical path link cost is “30” (sum of the costs of OLSP # 1, # 2, # 3), and the latter optical path link cost is “40” (cost of OLSP # 5). Packet traffic is accommodated in the optical path in the order of Node # 1- # 4- # 5- # 3) and rank 2 (Node # 1- # 3 (via # 2) route). An optical path is newly established when the free space is insufficient.
[0033]
When establishing a new optical path, the following two cases can be set.
Case (a): An optical path is newly established in a section that matches between the grounds of the packet traffic to be accommodated.
Case (b): An optical path is newly established in a section where the cost of the newly installed optical path is minimized, and packet traffic is accommodated in a route using the optical path.
[0034]
In the case of FIG. 3A, the case of the above Case (a): is shown, and an optical path is newly established in the route of Node # 1- # 3 (via # 2).
[0035]
On the other hand, FIG. 3B shows the case (b): where an optical path is newly established between Nodes # 2- # 3, and packet traffic is routed to the route using the optical path. Be contained. That is, the route is Node # 1- # 2- # 3.
[0036]
This method makes it possible to create a new dynamic optical path according to packet traffic accommodation requirements, but even if there is not enough traffic between a specific ground, an optical path can be established autonomously between that ground. The fiber link and optical switch capacity required for the entire network can be reduced.
[0037]
[Embodiment 2]
FIG. 5 is a diagram for explaining the second embodiment, and FIG. 6 is a flowchart of the second embodiment.
[0038]
In the second embodiment, a route search is performed in consideration of the limitation on the number of OLSP hops. Here, when a request for accommodation of packet traffic between specific grounds occurs, the shortest path (minimum optical path link cost path) viewed from the packet network 7 is first searched. When it is possible to reach the destination with the existing optical path with the number of hops within the specified number, packet traffic is accommodated on the route, and when it is impossible, a new optical path is established.
[0039]
In the example of FIG. 5, as in the first embodiment, the minimum optical path link cost route from Node # 1 to Node # 3 is searched, but the route of Node # 1- # 4- # 5- # 3 is Since the number of OLSP hops exceeds the specified number, accommodation of packet traffic is “prohibited”, and the route of Node # 1- # 3 (via # 2) is ranked first. Packet traffic is accommodated in the optical path of the route of this rank 1, and an optical path is newly established when the free capacity of this optical path is insufficient.
[0040]
The flowchart of the second embodiment shown in FIG. 6 (steps S21 to S27) is substantially the same as the flowchart of the first embodiment shown in FIG. 4 (steps S11 to S17), but the route search in steps S22 and S25 is performed. In the determination of the result, when the search route exceeds the limit of the number of OLSP hops, it is different from the first embodiment in that it is regarded as impossible to reach the destination with the existing optical path.
[0041]
In the second embodiment, the number of relay optical paths (that is, relay packet switch nodes) can be suppressed as compared with the first embodiment, and the transfer processing load on the packet switch nodes can be reduced.
[0042]
When a new optical path is established, the following two cases can be set as in the case of (a) and (b) shown in FIG.
Case (a): An optical path is newly established in a section that matches between the grounds of the packet traffic to be accommodated.
Case (b): An optical path is newly established in a section in which the cost of the newly installed optical path is minimized within a range satisfying the prescribed number of relay optical paths (that is, relay packet switch nodes), and the optical path is used. Contain packet traffic in the route.
[0043]
[Embodiment 3]
FIG. 7 is a diagram for explaining the third embodiment, and FIG. 8 is a flowchart of the third embodiment.
[0044]
In the third embodiment, when a request for accommodation of specific ground-to-ground packet traffic occurs, the shortest path (minimum fiber link cost path) viewed from the optical network 8 is first searched. This is different from the first embodiment in which the shortest path (minimum optical path link cost path) viewed from the packet network 7 is searched. The optical path is newly established only when it is impossible to reach the destination with the existing optical path on this route.
[0045]
This will be described with reference to the flowchart shown in FIG. For example, if a packet traffic accommodation request is generated between Node # 1 and Node # 3, a route that minimizes the fiber link cost of the existing optical path connecting Node # 1 and Node # 3 is searched (step S31). If there is no route to the end node (Node # 3) with the existing fiber, that is, if the fiber link cost to the end node is infinite, the process proceeds to step S36.
[0046]
If there is a route, it is determined whether there is an existing optical path corresponding to the search route (step S33). If there is an optical path, packet traffic is accommodated in the optical path, and the packet is transferred by the search route. (Step S34). If there is no existing optical path corresponding to the search route, an optical path is newly established in the shortage section of the optical path, packet traffic is accommodated in the optical path, and the packet is transferred (step S35).
[0047]
If there is no fiber link that can reach the end node, the route is searched including the existing optical path link (step S36). As a result, if it is impossible to reach the end node (step S37), the process proceeds to step S39. If there is a route that can reach the end node, the packet is transferred through the search route (step S38). At this time, if there is a shortage section of the optical path on the search route, a new optical path is established in that section. If any route cannot reach the end point, the packet transfer block or the packet is discarded (step S39).
[0048]
With the processing shown in FIG. 8, the packet traffic is accommodated with the priority shown in FIG.
[0049]
In this third embodiment, the route (path) accommodating packet traffic matches the minimum fiber ring cost path compared to the first and second embodiments, so that waste of optical network resources can be reduced. It becomes possible.
[0050]
When a new optical path is established, the following two cases can be set as in the case of (a) and (b) shown in FIG.
Case (a): An optical path is newly established in a section that matches between the grounds of the packet traffic to be accommodated.
Case (b): An optical path is newly established in a section that minimizes the cost of the newly installed optical path, and packet traffic is accommodated in a route using the optical path.
[0051]
[Embodiment 4]
FIG. 9 is a diagram for explaining the fourth embodiment, and FIG. 10 is a flowchart of the fourth embodiment.
[0052]
In the fourth embodiment, when a request for accommodation of specific ground-to-ground packet traffic occurs, the shortest path (minimum fiber link cost path) viewed from the optical network 8 is first searched. When it is possible to reach the destination with existing optical paths with the number of hops within the specified number, packet traffic is accommodated in the existing optical paths on this route, and when this is not possible, a new optical path is established. .
[0053]
The flowchart (steps S41 to S49) of the fourth embodiment shown in FIG. 10 is substantially the same as the flowchart (steps S31 to S39) of the third embodiment shown in FIG. 8, but the light corresponding to the search route in step S43. The difference is that the limitation on the number of OLSP hops is taken into account in determining the presence or absence of a path. Further, in the determination in step S47, when the search route searched in step S46 exceeds the limit on the number of OLSP hops, it is determined that there is no route that can accommodate packet traffic.
[0054]
In the fourth embodiment, the number of relay optical paths (that is, relay packet switch nodes) can be reduced as compared with the third embodiment, and the transfer processing load on the packet switch nodes can be reduced.
[0055]
When establishing a new optical path, the following two cases can be set.
Case (a): An optical path is newly established in a section that matches between the grounds of the packet traffic to be accommodated.
Case (b): An optical path is newly established in a section in which the cost of the newly installed optical path is minimized within a range satisfying the prescribed number of relay optical paths (that is, relay packet switch nodes), and the optical path is used. Contain packet traffic in the route.
[0056]
[Embodiment 5]
FIG. 11 is a diagram for explaining the fifth embodiment, and FIG. 12 is a flowchart of the fifth embodiment.
[0057]
In the fifth embodiment, when a request for accommodation of a specific ground-to-ground packet traffic occurs, an optical path that matches the ground of the traffic is newly established. This will be described with reference to FIGS. 11 and 12.
[0058]
For example, in FIG. 11, if a packet traffic accommodation request is generated between Node # 1 and Node # 3, a route that minimizes the fiber link cost connecting Node # 1 and Node # 3 is searched ( Step S51). If there is no route to the end node (Node # 3) in the fiber link, that is, if the cost to the end node is infinite, the process proceeds to step S54. If there is a route, an optical path is newly established on the fiber link of the search route (rank 1 in FIG. 11), and the packet traffic is accommodated and the packet is transferred (step S53).
[0059]
If there is no fiber link that reaches Node # 3, a route that has the lowest cost from Node # 1 to Node # 3 including the existing optical path link is searched (step S54). At this time, the limitation on the number of OLSP hops is considered as necessary. If a route reaching Node # 3 is found (step S55), the packet is transferred along the route (step S56). If the route to the end node (Node # 3) is not found even if the existing optical path link is included, the packet transfer is blocked or the packet is discarded (step S57).
[0060]
In the fifth embodiment, unlike the first to fourth embodiments described above, there is a high probability that the path accommodating the packet traffic matches the shortest path on the fiber link. In addition, since the packet switch handles only traffic that terminates at its own node, the transfer processing load can be greatly reduced.
[0061]
In addition, the fifth embodiment may be modified to allow a case where the limit on the number of OLSP hops imposed in step S55 is other than one. As a result, even if the network is congested and a new optical path is established and packet traffic cannot be transferred with OLSP / one hop, it is possible to guarantee the accommodation of the traffic, which increases the revenue for the communication carrier.
[0062]
It should be noted that these Embodiments 1 to 5 can be implemented by combining several according to the network state and the service class of the packet traffic to be accommodated.
[0063]
For example, as a combination of embodiments, a combination in which the fifth embodiment is applied to high-priority class traffic and the first embodiment is applied to low-priority class traffic.
[0064]
【The invention's effect】
As described above, according to the present invention, it is possible to newly establish a dynamic optical path according to a request for accommodating packet traffic, and it is possible to newly establish an optimum optical path according to the load state of the network.
[Brief description of the drawings]
FIG. 1 is a diagram illustrating a configuration example of a network system according to an embodiment of the present invention.
FIG. 2 is a diagram illustrating an example of a photonic router used in the present embodiment.
FIG. 3 is a diagram illustrating Embodiment 1;
FIG. 4 is a flowchart according to the first embodiment.
5 is a diagram illustrating Embodiment 2. FIG.
FIG. 6 is a flowchart of the second embodiment.
7 is a diagram illustrating Embodiment 3. FIG.
FIG. 8 is a flowchart of the third embodiment.
FIG. 9 is a diagram illustrating Embodiment 4;
FIG. 10 is a flowchart according to the fourth embodiment.
FIG. 11 is a diagram for explaining a fifth embodiment;
FIG. 12 is a flowchart according to the fifth embodiment.
[Explanation of symbols]
1-1 to 1-4 Photonic router
2 Packet switch
3 Optical switch
4,4 'optical path
5 Fiber
6 Traffic
7 Packet network
8 Optical network

Claims (2)

A method for newly establishing an optical path in a multi-layer network including a packet network composed of an optical path link and a packet switch, and an optical network accommodating the packet network and composed of a fiber link and an optical switch,
The accommodation of specific ground-to-ground packet traffic is changed according to the priority of two traffic , low priority traffic and high priority traffic,
For low-priority traffic, search for a route that minimizes the optical path link cost seen from the packet network.
The optical path is newly established only when the packet traffic cannot reach the destination on the existing optical path.
For high-priority traffic, search for a route that minimizes the fiber link cost seen from the optical network.
An optical path establishment method, which is performed for the first time when it is impossible to reach a destination with an existing optical path on the packet traffic route . A method for newly establishing an optical path in a multi-layer network including a packet network composed of an optical path link and a packet switch, and an optical network accommodating the packet network and composed of a fiber link and an optical switch,
The accommodation of specific ground-to-ground packet traffic is changed according to the priority of two traffic , low priority traffic and high priority traffic,
For low-priority traffic, a route that minimizes the optical path link cost seen from the packet network is searched. The optical path is newly established when the packet traffic is within the pre-defined number of hops. While it is only done when it is impossible to reach the destination with a pass,
For high-priority traffic, the path that minimizes the fiber link cost seen from the optical network is searched, and the new optical path is established by setting the existing optical path within the specified number of hops for the accommodated packet traffic. light path new method which is characterized for the first time do it in case it is not possible to reach the destination in.

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