JP2004363816A - Path control method - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a path control method that realizes proper path selection by taking the quality and characteristics of at least an actual transmission line itself into consideration in addition to existent path control technology. <P>SOLUTION: By this path control method, a path control part 1 selects the shortest path by reference to a link state database 3b according to metrics imparted to respective paths between nodes and determines whether transmission can be performed through the shortest path at speeds requested between the respective nodes according to a link measurement value regarding the transmission line itself to generate a path table 3c regarding the optimum path according to the determination results. <P>COPYRIGHT: (C)2005,JPO&NCIPI

Description

[0001]
TECHNICAL FIELD OF THE INVENTION
The present invention relates generally to a path control method applied to an IP network or the like, and more particularly to a path selection method that considers the quality and transmission characteristics of a transmission path itself that realizes optical transmission faster than conventional transmission.
[0002]
[Prior art]
Today, it is possible to dynamically generate an end-to-end path by establishing a LSP (Label Switched Path) provisioning technique. In such a path, it is being studied to use a transmission technology that is even faster than the conventional one, such as 160 Gbps or 40 Gbps. However, when using such a high-speed transmission technology, not only the problem of deterioration due to signal loss of the transmission line itself, which has been concerned up to now, but also new characteristics due to transmission characteristics and quality in the link of the transmission line itself. Problems can arise. That is, for example, when high-speed transmission of 40 Gbps is performed, a link that can be transmitted and a link that cannot be transmitted may be mixed in the path from the receiving end to the transmitting end. This means that depending on the quality, a situation may occur in which transmission is impossible even if a path is actually established.
[0003]
On the other hand, in the existing route control technology, by using a routing protocol such as OSPF (Open Shortest Path First), a route having a minimum metric cost is determined using a routing table from the receiving end to the transmitting end. A choice has also been made. As such a technique, for example, Patent Literature 1 discloses a technique relating to a variable band adaptive path control method in which a distance parameter is minimized and an economical path can be selected. Further, Patent Literature 2 discloses a technique relating to a route control device and method that provide scalable and multiple quality classes at low cost in a large-scale IP network.
[0004]
[Patent Document 1]
JP-A-7-245626
[Patent Document 2]
JP 2003-46548 A
[Problems to be solved by the invention]
However, with the existing technology using the routing protocol such as OSPF as described above, it is difficult to express the transmission characteristic quality of a link or the like as it is, so that it is not possible to appropriately select a route capable of high-speed transmission. Can not.
[0007]
That is, the technique disclosed in Patent Document 1 only performs path control mainly considering only the electrical transmission path, and does not actually consider the quality and characteristics of the optical transmission path. Even if a path is presented by the method, a situation may occur in which transmission is not actually possible. Furthermore, the technology disclosed in Patent Document 2 is a route selection method that mainly introduces the concept of a quality class in a packet network. However, since the path selection is not performed in consideration of the quality and characteristics of the transmission path itself, the same problem as the technique according to Patent Document 1 described above may occur.
[0008]
SUMMARY OF THE INVENTION The present invention has been made in view of the above problems, and has as its object to select an appropriate path by considering at least the quality and characteristics of the actual transmission path itself in addition to the existing path control technology. It is to realize.
[0009]
[Means for Solving the Problems]
In order to achieve the above object, according to a first aspect of the present invention, a route control unit selects a shortest route based on a metric given to each route between nodes by referring to a link state database, and Based on a link measurement value as an index for measuring its own quality, it determines whether or not transmission is possible on the shortest path for the speed required between each node, and selects an optimal path based on the determination result. A routing control method characterized in that:
[0010]
In the second aspect of the present invention, the route control unit refers to the link state database, selects the shortest route based on the metric given to each route between the nodes, and uses the route control unit as an index for measuring the quality of the transmission route itself. Judge whether or not transmission is possible on the shortest path with respect to the speed required between the nodes based on the service class in which the link measurement values are classified, and select the optimum path based on the judgment result. A route control method characterized by the following is provided.
[0011]
According to a third aspect of the present invention, in the first or second aspect, at least one of transmission loss, return loss, chromatic dispersion, and polarization dispersion is used as the link measurement value. A routing control method is provided.
[0012]
According to a fourth aspect of the present invention, there is provided a route control method according to the first or second aspect, further comprising using a Q value as the link measurement value.
[0013]
According to a fifth aspect of the present invention, in the first to fourth aspects, the link state database further includes information on resource management of the transmission path, and the path control unit performs the resource management. There is provided a route control method further characterized in that an optimal route is selected by making a determination based on information.
[0014]
In a sixth aspect of the present invention, the link state database further includes a resource management policy for a transmission path, and the path control means integrates a weighting coefficient determined based on the resource management policy into the metric. A route control method is further characterized in that an optimal route is selected based on the result obtained.
[0015]
BEST MODE FOR CARRYING OUT THE INVENTION
Hereinafter, embodiments of the present invention will be described with reference to the drawings.
[0016]
The embodiment of the present invention relates to a path control method applied to an IP network, and realizes path selection in consideration of the transmission path quality of a high-speed optical transmission path itself and its characteristics. More specifically, in the embodiment, when a method such as OSPF is used, a path control related to a high-speed optical transmission path is performed by adding a link transmission characteristic value that is difficult to express by a metric. In this case, the operational efficiency is improved. Further, a service class in which link measurement values relating to the quality and characteristics of the transmission line itself are classified in advance is introduced into the route selection method.
[0017]
Hereinafter, the embodiment will be described in detail based on this.
[0018]
(First Embodiment)
First, FIG. 1 is a conceptual diagram for explaining a route control method according to the first embodiment of the present invention. In the example illustrated in FIG. 1, metrics as illustrated are assigned to the respective routes of the nodes N1 to N6. Therefore, according to a general method such as OSPF, a route that minimizes the metric of each link is selected.
[0019]
That is, in the topology as shown in FIG. 1, for example, when a path is extended from the transmitting node N1 to the receiving node N6, according to a general OSPF method, N1 → N2 → N3 → at which the metric becomes minimum. The route of N6 is selected.
[0020]
However, in the example shown in FIG. 1, the transmission path quality is different from the transmission path that can transmit only X Gbps, the transmission path that can transmit only Y Gbps, and the transmission path that can transmit both X and Y Gbps. Therefore, for example, when there is a transmission request of XGbps, a situation may occur in which the route itself cannot be actually transmitted even if the route itself is selected in the previously selected route of N1 → N2 → N3 → N6. .
[0021]
In the first embodiment, in consideration of link transmission characteristics, any one of N1 → N2 → N5 → N6 or N1 → N4 → N5 → N6 is set as a transmittable path, and a final metric is set based on a metric. Choose a route. In this example, the former is selected. Then, in order to automatically select such a transmissible path, parameters (link measurement values) relating to the transmission quality and characteristics of the optical transmission path itself are added to the path table.
[0022]
More specifically, the following parameters for each link are used as indices for measuring transmission quality.
[0023]
-Fiber Loss value-Return Loss value-Chromatic Dispersion value-Polarization Mode Dispersion value-Q value (ITU-T G.976)
Here, the Q value is derived from the quality, means the quality of the transmission characteristics, and matches the signal-to-noise ratio (S / N) of the electric signal. In particular, it is one of the indexes related to the bit error rate characteristic (BER) after transmission in optical fiber transmission.
[0024]
Specifically, a value (measurement result) already measured for the laid optical fiber is used for route selection. In the first embodiment, first, a transmission loss value, a return loss value, and a chromatic dispersion value are adopted as indices for measuring transmission quality. Second, in addition to the transmission loss value, the return loss value, and the chromatic dispersion value, polarization dispersion is adopted as an index for achieving transmission quality. Third, the Q value is adopted as an index for measuring transmission quality. However, it is not limited to these first to third.
[0025]
FIG. 2 illustrates a configuration example of each of the nodes N1 to N6 that implements the above-described route control method. As shown in FIG. 2, each of the nodes N1 to N6 includes a communication interface (hereinafter, referred to as an I / F) 2 for communicating with another node via a plurality of ports, an LSA 3a described later, a link state database 3b, The storage unit 3 includes a route table 3c and the like, and a route control unit 1 that performs route selection and the like with reference to these tables and databases. The OSPF based on the first embodiment is a routing protocol using a link state algorithm, and each node outputs a message called a link state. The link state includes information such as the state of the link to which each node is connected, the network address of the link, and the cost. Each node that has received the link state grasps the network configuration based on the information. Each node has a link state database 3b that grasps the configuration of all nodes and links. In the first embodiment, although details will be described later, the link state database 3b also includes link measurement values relating to the quality and characteristics of the transmission path itself. Each node creates the shortest path tree and further creates a routing table with reference to the database 3b and the like. In the above-described node configuration, the path control unit 1 plays these roles. The metric means a parameter indicating a distance from the destination.
[0026]
Next, a description will be given of an improved example in which the resource management is further considered in the route control method according to the first embodiment as described above.
[0027]
In the example of FIG. 1, if there is a transmission path capable of transmitting both X Gbps and Y Gbps in response to a transmission request of X Gbps, and if resource management is not performed, which transmission path is Since it is not managed whether it is used, it may affect the route selection. For example, when X Gbps transmission is desired to be performed, a situation may occur in which the transmission path capable of X Gbps transmission has been exhausted and cannot be used.
[0028]
In order to avoid such a situation, in this improved example, a resource management policy for arranging resources is set, and path control is performed in consideration of the policy.
[0029]
The following can be adopted as an example of the resource management policy. That is, first, an X Gbps transmission request uses an X Gbps transmission path first, a second Y Gbps transmission request uses a Y Gbps transmission path first, and third, the resources of each transmission path are exhausted. In this case, a transmission path capable of transmitting both X and Y Gbps is used. However, the resource management policy can be set freely.
[0030]
In the example of FIG. 1, when there is a transmission request of YGbps, first, N1 → N4 → N2 → N5 → N6 with the minimum metric is selected. However, when the resource management policy is set as in the improved example, the link that can transmit YGbps is selected first, and N1 → N4 → N2 → N3 → N6 is selected.
[0031]
When such a resource management policy is set, weighting is dynamically performed in accordance with the policy, that is, a resource policy parameter (RPP: Resource Policy Parameter) is set. In FIG. 1, when a resource management policy of using a YGbps transmission line is set first in a YGbps transmission request, a weight for the YGbps transmission line is added to a metric (cost value). You.
[0032]
In this case, the metric of the route of N2 → N5 → N6 is 2 + 2 = 4, and the metric of N2 → N3 → N6 is 2 + 3 = 5, but since RPP = 0.5, 5 × 0.5 = 2. 5 and finally, the path of N2 → N2 → N6 is selected first. The PPP is dynamically given according to the policy.
[0033]
Here, in the topology as shown in FIG. 3, the RPP can be set in N1 → N2 → N4 → N5 and N1 → N3 → N4.
[0034]
In this case, the RPP is added to the total metric of the transmission path to calculate a final value. That is, (2 + 3 + 4) × 0.5 = 4.5 for N1 → N2 → N4 → N5, and (2 + 2) × 0.4 + 4 = 5.6 for the latter.
[0035]
By the way, in order to provide the route in which the optimum LSP is selected, it is necessary to share the link measurement value in each transmission path between the nodes. For this purpose, information such as a distance between adjacent nodes, an interface of the device, a link measurement value indicating the transmission quality and characteristics of the transmission path itself, and a resource management policy are shared.
[0036]
More specifically, in the first embodiment, the link measurement value and the resource management policy are also advertised to the LSA using the link-state advertisement (LSA) of the OSPF. Advertisement of the link measurement value in this way increases the flexibility of path selection in consideration of the quality and characteristics of the transmission path itself.
[0037]
Here, the LSA refers to information for grasping the link topology of the network. In order to share the routing table information, a link state database indicating the topology between the links is used. For example, in the first embodiment, the link measurement values related to the quality and characteristics of the transmission path itself and the resource management policy information are stored in the link state database of the storage unit 3.
[0038]
Now, as shown in FIG. 4, assuming that a metric and a link measurement value (shown in parentheses beside the number indicating the metric in the figure) of each route are assigned, the LSA is calculated as shown in FIG. The contents are as shown in the following. That is, for a path linking two nodes, the I / F port, metric, link measurement value, and RPP of each node are stored in association with each other as shown in the figure.
[0039]
More specifically, in the example shown in FIG. 5, the I / F port of the node N1 is 1-A, the I / F port of the node N2 is 2-B, the metric of the route between them is 1, and the link is The measured value is α, and RPP is not set. Then, a link state database is created based on the LSA exchanged between the nodes.
[0040]
An example of the link state database created in this way is shown in FIG. That is, in the example of FIG. 6, the port, the metric, and the link measurement value (or a service class described later) of the I / F of each path are associated with the path between the transmission destination node and the transmission source node. Is remembered. For example, as for the path between the nodes N1 and N2, the I / F of the node N1 is 2-B, the I / F port of the node N2 is 1-A, the metric is 1, and the link measurement value is α. It can be seen from the database.
[0041]
The procedure for creating a route table using such a link state database is as follows. That is, first, a shortest path tree based on a metric is created using OSPF with reference to the link state database. Next, the link measurement value (or the service class described later) in the database is confirmed, and it is determined whether transmission is possible at the requested speed between the nodes. Note that a path that is not applied to the link measurement value (or a service class described later) is deleted. When the RPP is set, the value of the RPP is added to the metric of each path. Thus, the shortest path tree is created again using the OSPF based on the metric. The finally constructed path tree becomes a path table.
[0042]
Next, an improved example in which the concept of a service class is further introduced in the route control method according to the first embodiment as described above will be described.
[0043]
The service class is a class in which conditions that can be actually transmitted, that is, link measurement values are classified into levels. For example, an optical fiber capable of transmitting XGbps requires that some of the above-mentioned parameter conditions of the link measurement values be cleared, but a service class can determine such a condition. Has defined. In this improved example, by introducing a service class divided into levels for each link in this way, when selecting a route, it is possible to immediately determine which transmission speed can be actually transmitted on the transmission path. It becomes possible to grasp.
[0044]
Here, an example of a service class table in which a service class is defined will be described with reference to FIGS. 7 and 8. First, in the example of FIG. 7, a service class is defined by using a transmission loss value, a return loss value, and a chromatic dispersion value of each link as first to third parameters as indices for measuring the quality of the transmission line itself. Things. In this example, the service class SC1 has the best transmission characteristics of XGbps. In the service class SC5, the transmission line has a possibility that transmission may not be possible in some cases. However, it is not a transmission line that cannot be reliably transmitted, but a transmission line that is inferior in judgment based on measured values. Is shown. The above parameter is an example, and it goes without saying that a polarization dispersion value may be further added as a fourth parameter.
[0045]
On the other hand, the example of FIG. 8 defines a service class using a Q value (ITU-T G.976) as a parameter as an index for achieving transmission quality. In this example, the service class that can transmit YGbps and has the best condition is SC1. The service class SC4 indicates that transmission is possible, but from the result of the Q value, transmission may be impossible in some cases. By referring to these service class tables, dynamic route selection according to various service classes becomes possible.
[0046]
(Second embodiment)
In the second embodiment, a transmission loss value, a return loss value, a chromatic dispersion value, and a polarization dispersion value are adopted as link measurement values for measuring the quality of the transmission path itself.
[0047]
Now, in the topology shown in FIG. 9, it is assumed that, as a route selection for setting up an LSP from the node N1 to the node N3, a route is selected in consideration of the best transmission characteristics as an LSP capable of transmitting XGbps.
[0048]
FIG. 10 illustrates an LSA related to a path between the node N1 and the node N2. In this LSA, the port of the I / F of the node N1 is A, the port of the I / F of the node N2 is B, the metric is 1, and the link measurement value is a separate table. (N1 → N2 → N3) is defined.
[0049]
FIG. 11 shows link measurement values between nodes in the second embodiment.
[0050]
That is, in the table of FIG. 11, the link measurement values (transmission loss value, return loss value, chromatic dispersion value, polarization dispersion value) between the nodes and the metrics are defined.
[0051]
The contents of the link state database created by exchanging such LSAs between nodes are shown in FIG. 12, for example.
[0052]
Hereinafter, the procedure of the route control method according to the second embodiment will be described in detail with reference to the flowchart in FIG. First, a route from N1 to N3 is selected based on the LSA metric (step S1). Then, SC1 is applied as a suitable service class with reference to the service class table of FIG. 7 (step S2). In this example, from the link measurement values, the path from N1 to N3 does not correspond to the service class SC1, and as a result, the paths from N1 to N2 and N2 to N3 are selected. Subsequently, the cost calculation is performed again according to the resource management policy (step S3). Then, based on the service class and the resource management policy based on the link measurement value, a table indicating a route, that is, a path tree is created (step S4). Finally, the route is selected as N1 → N2 → N3 (step S5).
[0053]
(Third embodiment)
In the third embodiment, a Q value is adopted as a link measurement value for transmission path quality. Here, too, in the topology shown in FIG. 9, it is assumed that, as a route selection for setting up an LSP from node N1 to node N3, a route is selected in consideration of the best transmission characteristics as an LSP capable of transmitting XGbps. In the third embodiment, path control is performed based on the Q value, which determines whether or not XGbps transmission is possible.
[0054]
Here, the LSA related to the route between the node N1 and the node N2 is shown in FIG. In this LSA, the port of the I / F of the node N1 is A, the port of the I / F of the node N2 is B, the metric is 1, and the link measurement value is a separate table. It is defined that there is. FIG. 15 shows a link measurement value between each node in the third embodiment. That is, in this table, the Q value and the like are defined as the link measurement values between the nodes.
[0055]
The contents of the link state database created by exchanging such LSAs between nodes are, for example, as shown in FIG.
[0056]
Hereinafter, the route control method will be described with reference to the flowchart in FIG.
[0057]
First, N1 → N3 is selected based on the metric (step S11). Next, a determination is made based on the Q value as a parameter for achieving transmission path quality. For that purpose, SC1 of the service class table in FIG. 8 is applied. The path from N1 to N3 does not apply from the link measurement value, and N1 to N2 and N2 to N3 are selected (step S12). In this example, since no resource management policy is set, a metric is applied (step S13), and since N1 → N3 does not apply based on the service class, a table indicating a route, that is, a path tree is created. (Step S14). Finally, the route N1 → N2 → N3 is selected (step S15).
[0058]
As described above, according to the embodiment of the present invention, in addition to the existing path control technology, it is possible to select a path in consideration of a link measurement value related to actual transmission path quality and resource management. Further, in the embodiment, transmission control in consideration of the optimal transmission conditions on the transmission path can be realized by the service class classified for each level of the link measurement value. In addition, in the embodiment, since the time for checking whether or not transmission is possible, which has been an additional work when evaluating a transmission path, which is conventionally performed, is no longer required when selecting a path, the operation efficiency of the path selection is reduced. It is greatly improved.
[0059]
The embodiments of the present invention have been described above. However, the present invention is not limited to the embodiments, and it is a matter of course that various improvements and modifications can be made without departing from the gist of the present invention. For example, the present invention also includes a path control device that realizes the above-described path control method, a path control program, and a recording medium that records the path control program.
[0060]
【The invention's effect】
As described in detail above, according to the present invention, in addition to the existing path control technology, a path control method that realizes appropriate path selection by considering at least the quality and characteristics of an actual transmission path itself is provided. can do.
[Brief description of the drawings]
FIG. 1 is a conceptual diagram for describing a route control method according to a first embodiment.
FIG. 2 is a diagram illustrating a configuration example for realizing a route control method according to the first embodiment;
FIG. 3 is a diagram illustrating a resource policy parameter assigned to a path between nodes in the first embodiment.
FIG. 4 is a diagram illustrating a metric and a link measurement value of each route added in the route control method according to the first embodiment.
FIG. 5 is a diagram illustrating an example of an LSA employed in the route control method according to the first embodiment;
FIG. 6 is a diagram illustrating an example of a link state database employed in the route control method according to the first embodiment.
FIG. 7 is a diagram illustrating an example of a service class table employed in the route control method according to the first embodiment;
FIG. 8 is a diagram illustrating an example of a service class table employed in the route control method according to the first embodiment.
FIG. 9 is a diagram illustrating a topology for describing a route control method according to the second and third embodiments.
FIG. 10 is a diagram illustrating an example of an LSA employed in the route control method according to the second embodiment;
FIG. 11 is a diagram illustrating link measurement values between nodes according to the second embodiment.
FIG. 12 is a diagram illustrating an example of a link state database used in the route control methods according to the second and third embodiments.
FIG. 13 is a flowchart illustrating a procedure of a route control method according to the second embodiment.
FIG. 14 is a diagram illustrating an example of an LSA employed in the route control method according to the third embodiment.
FIG. 15 is a diagram illustrating link measurement values between nodes according to the third embodiment.
FIG. 16 is a flowchart illustrating a procedure of a route control method according to the third embodiment.
[Explanation of symbols]
N1 to N6: nodes, 1: path control unit, 2: communication interface, 3: storage unit.

Claims (6)

By the route control means,
Referring to the link state database, select the shortest path based on the metric given to each path between the nodes,
Based on the link measurement value as an index for measuring the quality of the transmission path itself, it is determined whether or not transmission is possible on the shortest path for the speed required between the nodes, and the optimum path is determined based on the determination result. Select the
A route control method characterized by the above-mentioned. By the route control means,
Referring to the link state database, select the shortest path based on the metric given to each path between the nodes,
Based on a service class that classifies a link measurement value as an index for measuring the quality of the transmission path itself, it is determined whether or not transmission is possible on the shortest path for the speed required between the nodes based on the service class. Choose the best route based on
A route control method characterized by the above-mentioned. 3. The route control method according to claim 1, further comprising using at least one of transmission loss, return loss, chromatic dispersion, and polarization dispersion as the link measurement value. The route control method according to claim 1, further comprising using a Q value as the link measurement value. The link state database further includes information on resource management of the transmission path, and the path control means further updates the selection of the optimum path by making a determination based on the information on the resource management. The route control method according to claim 1, wherein: The link state database further includes a resource management policy for the transmission path, and the path control means selects an optimal path based on a result obtained by multiplying the metric by a weighting coefficient determined based on the resource management policy. 5. The route control method according to claim 1, further comprising:

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