JP2002009798A - Route control system - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a route control system that can enhance the throughput of an ATM network and efficiently operate network resources of the entire ATM network. SOLUTION: When a present route reaches an overload state, a route with a lighter load than that of the present route is selected as an object of a bypass route, and a load state is estimated on the basis of the frequency of occurrence of congestion in the past in this case. Comparing the consumed quantity of network resources of the present route with the consumed quantity of network resources of the bypass route executes switching from the present route to the bypass route when the difference is within a permissible range.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention is used for route control of a connection between an input edge node and an output edge node of a data transfer network.

[0002]

2. Description of the Related Art Ethernet (registered trademark) LAN
(Local Area Network) and the rapid spread of the Internet, the demand for data communication traffic is increasing. Route data communication traffic to WAN (Wide Area Ne
ATM has attracted attention as a transfer technique in twork). In ATM, fixed-length packets called cells are used as transfer units.

[0003] Transfer control information such as destination information is added to the cell together with the transfer data. Each ATM switch relays the transfer control information based on the transfer control information, thereby making it possible to transfer the ATM.
Transferred over the network. ATM basically employs a connection-type communication system, and data communication traffic within an ATM network is set up in advance between an input edge node and an output edge node of the ATM network, and is transferred over the connection. It is realized by.

At present, in most data communication represented by the Internet, user packet transfer is performed by a best-effort service that does not make a bandwidth reservation in advance. As described above, in the best-effort service, no bandwidth reservation is made, so that when the amount of traffic flowing into the ATM network increases, congestion occurs and cell loss occurs. Since the discarded cells are retransmitted by the terminal,
Once congestion occurs, there is a problem that the throughput is extremely reduced. For this reason, congestion control for avoiding congestion is important in ATM networks that provide best-effort services.

As a conventional congestion control technology, ECN (Expl)
icit Congestion Notification). In this method, when a congestion state is detected in a link, the node notifies the originating terminal of the occurrence of congestion. The terminal receiving the congestion notification lowers the cell transmission rate to release the congestion state and prevent cell discard.

[0006] Best effort traffic is ABR
In the transfer method using the (Available Bit Rate) service, RM (Resource Management) is used for each connection.
t) By performing feedback control of the transmission rate of the terminal using cells, congestion is avoided by avoiding cell discard.

In the conventional congestion avoiding system proposed above, congestion occurring on a route set in advance between edge nodes is only avoided by restricting the amount of traffic flowing into the ATM network. If the set route is not optimal, the increased traffic is concentrated on a specific link, and congestion frequently occurs on that link, while a situation occurs in which a link using almost no resources exists. . In such a situation, it cannot be said that the resources of the entire ATM network are operated efficiently.

As a means for reducing the congestion while increasing the utilization efficiency of the ATM network, a load distribution method by distributing a traffic route through a congested link is effective. Such a method is disclosed in Japanese Patent Application Laid-Open No. 5-292109.
There is a logical path distributed accommodating call connection system in an ATM network disclosed in Japanese Unexamined Patent Publication (Kokai) Publication. This is because, when traffic suddenly rises locally due to burst concentration or failure occurrence in the ATM network, in order to suppress cell discarding and increase in cell delay time in the ATM network, an incoming / outgoing switching node is always provided for each call. In this method, logical paths are accommodated in a plurality of routes between them.

In this method, for each call in the ATM network, a pre-calculated estimated value of the percent delay is compared for each of a plurality of routes of the originating and terminating exchange nodes, and a route (transmission line) for minimizing the estimated value. By storing a logical path in one of them, the logical path is dispersed and accommodated in a transmission line in an ATM network.

In this system, a routing table to the destination switching node is required for each relay node in the ATM network.
Also, for each call, the percent delay of each route between
There is a need for a function that estimates and compares traffic that changes over time and calculates a route that minimizes the percent delay of each route between destination and destination nodes. There is a problem in increasing the size due to the complexity of such a configuration.

In the route control for selecting a route that minimizes the sum of the percent delays in the output (input) buffer of each relay node from routes preset for each call,
Since the selection is not made in consideration of the utilization efficiency of the ATM network resources, there are cases where a route through an extremely large number of relay nodes is selected as compared with the shortest route, and a problem remains from the viewpoint of efficient operation of the ATM network. .

The application area of this system is connection-type communication in which a call is set up between a calling node and a destination node before performing communication, and a band required for each call is declared to an ATM network before performing communication. It is assumed that

[0013]

When transferring data communication traffic of a best-effort service using an ATM network, a packet is divided into cells by AAL type 5 and semi-permanent between an input edge node and an output edge node. Transfer on the route of the connection that has been set.
In addition, the best-effort service data communication traffic is characterized in that it does not declare in advance the necessary bandwidth and the nature of the traffic to the ATM network at the time of communication. Is difficult to define.

Therefore, it is difficult to set a fixed optimal route in a fixed manner, and for route optimization, it is necessary to change the route according to a change in traffic volume. However, measuring the amount of traffic between edge nodes that changes over time is a very large and complicated process, and it is necessary to calculate the optimal route based on the measured amount of traffic between edge nodes. Is not realistic. In addition, if route switching is executed only depending on the measurement result of the traffic volume at the time when the route switching request is generated, since the traffic situation changes every moment, it is not always possible to realize the optimal route switching. Have difficulty.

It is an object of the present invention to provide a route control system capable of executing route switching while avoiding a route with a high frequency of occurrence of congestion. In the present invention, the congestion occurrence frequency is set to A
It is an object of the present invention to provide a route control system capable of distributing the load by equalizing the entire TM network and improving the throughput of the ATM network. An object of the present invention is to provide a route control system capable of efficiently operating network resources of the entire ATM network.

[0016]

SUMMARY OF THE INVENTION The present invention is a route control system, which is characterized by means for setting up a connection in an ATM network and the past of each link in the ATM network. Means for generating the load state information of each link based on the frequency of occurrence of congestion, wherein the means for making the setting includes the
Based on the load status information of each link in the M network, when there is a detour route whose load is lower than that of the current route and whose difference from the consumption amount of the network resources of the current route is within an allowable range, the current route is determined. There is a means for switching to a detour route.

Here, the consumption amount of the network resource means that, for example, the longer the route distance, the larger the number of relay nodes through which the route goes, so that the consumption amount of the network resource increases. The allowable range is, for example, the consumption of network resources provided for determining that a detour route whose distance is significantly longer than the current route is not appropriate as a detour route. It is a value range, and it is desirable to determine the value appropriately according to the situation of the network.

That is, when the current route is overloaded, a route having a lower load than the current route is selected as a detour route. In the present invention, the load status is estimated based on the past congestion occurrence frequency. I do. Further, if the network resources consumed by the switching to the detour route are out of the allowable range compared to the network resources consumed by the current route, the switching is abandoned.

As described above, since the load situation is estimated based on the past congestion occurrence frequency, it is possible to avoid a situation where traffic is concentrated on a route where congestion is likely to occur. Furthermore, since it is determined whether or not the switching can be performed in consideration of the consumption of the network resources, the network resources of the entire ATM network can be operated efficiently.

The means for generating the load state information sets the consumption of the network resources of the link i (i is a number assigned to each link) to a steady load di, and calculates the congestion observed during the operation of the link i. The fluid load of link i calculated as a monotonic non-decreasing function based on the occurrence frequency Ni is expressed as f (N
means for calculating a link cost f (Ni) * di as i), and each link cost f (Ni) * d of the bypass route
i is added to each link cost f (N
i) means for calculating a value divided by the sum of * di as an index α, wherein a route switching threshold value preset in the ATM network is αH, and the switching means is α <αH
Preferably, a means for switching from the current route to the detour route is included.

This route switching threshold αH is a value set in consideration of the average traffic volume of the ATM network and other various factors, and is set to an appropriate value when the ATM network is constructed or when the ATM network configuration is changed. It is desirable to be done.

More specifically, the route control system according to the present invention will be described. An input edge node installed at a boundary between a connection start point and an ATM network, and an input edge node installed at a boundary between the connection end point and the ATM network. An output edge node, a plurality of relay nodes interposed in a transmission path between the input edge node and the output edge node, a load information database for recording load information in the ATM network, and a connection in the network. The relay node comprises: a traffic monitoring unit that monitors a traffic amount flowing into a link to which the relay node is connected; and a traffic monitoring unit that monitors the traffic amount by the traffic monitoring unit. Congestion detection means for detecting congestion of the link, and occurrence of congestion detected by the congestion detection means Congestion information notifying means for notifying the information about the load information database, and a route switching request determining means for determining whether to request a route switching from the information on the occurrence of congestion notified by the congestion information notifying means, The load information database includes: a link load state determining unit that estimates a load state of each link from the received information regarding occurrence of congestion; a unit that records a load state of the link; and a unit in the ATM network recorded according to the request. Means for transmitting link load state information, wherein the path setting device transmits the A
Means for acquiring information relating to the load status of each link in the TM network; and network resources of the current route having a lower load than the current route from the input edge node to the output edge node from the load status information of each link. Optimal route calculation means for selecting a route having a difference from the consumption amount of the permissible range as a detour route, and route switching determination means for determining whether or not switching from the current route to the detour route is possible, The link load state determination means sets the consumption of network resources of the link i (i is a number assigned to each link) as a steady load di, and is monotonic based on the congestion occurrence frequency Ni observed during the operation of the link i. The fluid load of link i calculated as a non-decreasing function is represented by f (N
means for calculating link cost f (Ni) * di as i), and link cost f (N
i) means for calculating, as an index α, a value obtained by dividing the total sum of * di by the total sum of each link cost f (Ni) * di of the current route, and setting a route switching threshold value preset in the ATM network. αH, and the route switching determining means includes means for determining that switching from the current route to the alternative route candidate is possible when α <αH.

It is preferable that the information on the occurrence of congestion is information on the frequency of occurrence of congestion calculated from the history of occurrence of congestion.

The input edge node is provided with the route setting device and the load information database. The input edge node selects a detour route candidate for a connection passing through the input edge node and determines whether or not the route can be switched. It is also possible to provide a configuration provided with means for performing autonomous decentralization.

That is, each relay node monitors the amount of traffic flowing into the link to which the relay node is connected, and when the average inflow speed to the output side link exceeds the output link speed for a certain period of time or more. The congestion that occurs in the network is detected, and a history of occurrence of congestion within a certain period is stored. Further, the congestion occurrence frequency in the cycle is notified to the load information database, and the load state is estimated from the history of the congestion occurrence within a certain period to determine whether or not to request the route switching.

The load information database is connected to each relay node in the ATM network, has information on the topology of all nodes and links in the ATM network, and can record the load state of each link. Each relay node transmits the congestion information of the link connected to its own node to the load information database, and the load state database stores each link in the ATM network from the congestion information transmitted from each relay node in the ATM network. Is estimated. Also, the load state information that has already been recorded is updated based on the link congestion occurrence frequency. Further, according to the request, the topology in the ATM network and the load status information of each link can be transmitted.

The route setting device sets a connection specifying a relay node that passes between the input edge node and the output edge node. The path setting device is connected to the load information database, and the path setting device transmits the A
It acquires information about the topology and load state of the TM network and records the information. Also, based on the information of the load information database, the load is estimated based on the past congestion occurrence frequency from the input edge node to the output edge node, a bypass route is selected, and it is determined whether or not to switch to the selected bypass route. I do.

When the relay node detects a state in which the frequency of occurrence of congestion within a unit time of the link connected to the own node continues to exceed a certain value, the relay node sets a route for a connection passing through the link. A route switching request is transmitted to the setting device.

The route setting device that has received the route switching request first selects a bypass route that bypasses the link in order to distribute the load. At this time, since the load state information based on the past congestion occurrence frequency of each link in the ATM network is taken into consideration, it is possible to prevent traffic from concentrating on a route having a high congestion occurrence frequency. Further, since the current network resource consumption of the current route and the network resource consumption of the detour route are compared and the difference is not deviated from the allowable range, the route switching is executed.
The load can be distributed by effectively using the network resources of the entire network, and the frequency of occurrence of congestion can be reduced. When the congestion is reduced, the cell discard is reduced, so that the throughput of the ATM network is improved.

As described above, in order to maximize the throughput of the entire ATM network, it is necessary to distribute the load concentrated on a specific link to the entire ATM network. The frequency of occurrence of congestion on the same route can be equalized.

That is, if the routes of all the connections passing through the congested link are changed, the load is again biased to the other links. Therefore, in order to achieve load distribution, a connection whose route is to be changed appropriately is selected. It is necessary to adjust the amount of traffic passing through the loaded link to an appropriate value. In the route setting device of the present invention, when the load on the route of the current connection is high, there is a candidate for a detour route with a low load estimated based on past congestion occurrence frequency, and further, the detour route consumes Route switching is performed only when the network resources are within an allowable range compared to the network resources consumed by the current route. When the route switching is determined, a connection is set according to the calculated detour route, and the connection is switched. Such a procedure realizes efficient use of network resources of the entire ATM network and prevention of a sudden shift in traffic due to route change.

As described above, according to the present invention, congestion occurrence information in the ATM network is collected, and A is estimated based on the information.
By using the load state of the entire TM network and optimizing the connection route between the edge nodes, the frequency of occurrence of congestion on each link can be equalized, the load can be distributed, and the throughput of the entire ATM network can be improved. As a result, network resources of the entire ATM network can be operated efficiently.

[0033]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS The configuration of a route control system according to an embodiment of the present invention will be described with reference to FIGS. FIG. 1 is an overall configuration diagram of a route control system according to an embodiment of the present invention. FIG. 2 is a block diagram of a main part of the relay node according to the embodiment of the present invention. FIG. 3 is a block diagram of a main part of the load information database according to the embodiment of the present invention. FIG. 4 is a block diagram of a main part of the route setting device according to the embodiment of the present invention.

According to the present invention, a path setting device 2 for setting a connection in an ATM network 1 and a link load for generating load state information of each link based on a past congestion frequency of each link in the ATM network. A state determination unit 60 is provided, and the route setting device 2
Based on the load status information of each link in the ATM network 1, when there is a detour route having a lower load than the current route and a difference from the consumption of network resources of the current route within an allowable range, the current route is determined. It is characterized by including a route switching judgment unit 21 for switching to the detour route.

The link load state judging section 60 determines whether the link i
The link i calculated as a monotonic non-decreasing function based on the congestion occurrence frequency Ni observed during the operation of the link i, where the consumption of the network resource of (i is a number assigned to each link) is defined as a steady load di. The link cost f (Ni) * di is calculated with the fluid load of f (Ni) as the load of the current route, and the sum of the link costs f (Ni) * di of the alternative route candidates is calculated as the link cost f of the current route. (Ni) * di
Is calculated as an index α, and when a route switching threshold set in advance in the ATM network 1 is αH, the route switching determining unit 21 determines from the current route when α <αH. It is determined that switching to the detour route is executable.

More specifically, the input edge node 3 installed at the boundary between the start point of the connection and the ATM network 1, the terminal point of the connection and the ATM network 1
, An output edge node 4 installed at a boundary between the input edge node 3, a plurality of relay nodes 5 inserted in a transmission path between the input edge node 3 and the output edge node 4, and a load information database for recording load information in the ATM network 1. 6 and a route setting device 2 for setting a connection in the ATM network 1. The relay node 5 includes a monitor 50 for monitoring the amount of traffic flowing into the link to which the relay node 5 is connected. A congestion detection unit 51 for detecting congestion of the link in accordance with the result of monitoring the traffic volume by the monitoring unit 50; and a congestion information notification unit 52 for notifying the load information database 6 of information on the occurrence of congestion detected by the congestion detection unit 51. Route switching for determining whether or not to request the route switching based on the information about the occurrence of congestion notified by the congestion information notifying unit 52. And a calculated determination unit 53, a load information database 6, link estimates the load status of each link from the information on congestion received load status determination section 60
And a link-specific load status information storage unit 61 for recording the load status of the link and transmitting the load status information of each link in the ATM network 1 recorded according to the request. A database 22 for acquiring information on the load state of each link in the ATM network 1 from the load information database 6; and an input edge node 3 to an output edge node 4 based on the load state information of each link.
An optimal route calculation unit 20 that selects a route having a load lower than that of the current route up to the current route and having a difference from the consumption amount of the network resource of the current route within an allowable range as a bypass route,
A link switching state determination unit that determines whether or not the switching from the current route to the detour route can be performed; the link load state determination unit sets the consumption of the network resources of the link i as a steady load di; The link cost f (Ni) * di is calculated as f (Ni), where f (Ni) is the fluid load of link i calculated as a monotonic non-decreasing function based on the congestion occurrence frequency Ni observed during operation of i. A value obtained by dividing the sum of the link costs f (Ni) * di of the candidates by the sum of the link costs f (Ni) * di of the current route is calculated as an index α, and is set in the ATM network 1 in advance. When the route switching threshold value αH is set, the route switching determination unit 21 is to determine that switching from the current route to the detour route is executable when α <αH. The information on the occurrence of congestion is information on the frequency of occurrence of congestion calculated from the history of occurrence of congestion.

As another embodiment, the input edge node 3 is provided with a route setting device 2 and a load information database 6 for selecting a detour route candidate for a connection passing through the input edge node 3 and switching the route. It is also possible to adopt a configuration in which the availability determination is performed autonomously and decentralized by the input edge node 3. Hereinafter, embodiments of the present invention will be described in more detail.

As shown in FIG. 1, the ATM network 1 has A
Input edge node 3 which is the starting point of TM connection
And an output edge node 4 which is a terminal point of the connection. A plurality of relay nodes 5 are arranged between the input edge node 3 and the output edge node 4 so as to relay a transfer packet (cell) between the input edge node 3 and the output edge node 4. A semi-permanent connection is previously set between the input edge node 3 and the output edge node 4 in the ATM network 1, and data communication traffic is transferred on this connection.

The load information database 6 monitors the load status of each link in the ATM network 1 and stores the load status information of each link. The route setting device 2 has a connection setting function.

As shown in FIG. 2, each relay node 5 is provided with a congestion detection unit 51, which monitors the traffic volume of the link connected to the own node and determines the average inflow speed to the output side link. It is possible to detect a congestion state that occurs when the output link speed is higher than the output link speed by a certain time or more. When a congestion state is detected, the occurrence of the state is notified to the congestion information notification unit 5.
Notify 2. The congestion information notification unit 52 stores time-series data of the occurrence of a congestion state occurring in the past TM.

FIG. 5 is a diagram for explaining the principle of estimating the load state of each link from the congestion occurrence information. TL is a congestion information transmission cycle. TM is the congestion information storage time width. tc is the current time. tn is the congestion information transmission time. As shown in FIG. 5, the relay node 5 notifies the load information database 6 of the congestion information at a constant interval every TL time. The information to be notified is a value obtained by dividing the frequency of occurrence of congestion occurring in the past TL time by the frequency of congestion occurrence in the past TL time by TL. Other information to be notified includes the source address and congestion information such as the frequency of occurrence of congestion of each link connected to the relay node 5.
Passes this information to the link load state determination unit 60 to estimate the link load state. N is the congestion frequency of each link
If i (where the subscript i is a number assigned to the link), it is determined that an overload state is established when Ni ≧ CH and a low load state is established when Ni ≦ CL.

FIG. 6 is a diagram showing a change in the frequency of occurrence of congestion. The horizontal axis represents time, and the vertical axis represents the frequency of occurrence of congestion. As shown in FIG. 6, the frequency of occurrence of congestion varies with time. Therefore, when the route is selected as a detour route candidate during a time period when no congestion occurs in FIG. 6, according to the related art, the route switching from the current route to the detour route candidate is performed as it is. However, according to the present invention, the load state is estimated based on the past congestion occurrence frequency, so that switching to a route with high congestion occurrence frequency can be avoided.

FIG. 7 is a diagram for explaining a function used for calculating an optimum route. In FIG.
The vertical axis represents the monotone non-decreasing function f (α). As shown in FIG. 7, a function f (α) is used to digitize the load state. The function f (α) has a role of determining the load state from the link congestion occurrence frequency, and 0 <f (0) ≦ 1, f (CL)
= 1 or more monotone non-decreasing function. That is, a value of less than 1 is given to a link in a low load state, and a value of 1 or more is always given to a link in an overload state.

The topology database 62 in the load information database 6 has information on costs di semi-fixedly given to each link, in addition to information on nodes and links in the ATM network 1. The link load state determination unit 60 calculates a cost f (Ni) * di reflecting the link load state. This cost has a value smaller than di when the load is low, and has a value larger than di when the link has a high load. Cost f reflecting the calculated link load state
(Ni) * di is recorded in the load status information storage unit 61 for each link. The load information database 6 includes the relay node 5
Each time it receives congestion information from the server, the link-specific load state information storage unit 61 is updated, and when there is a request for database information from the route setting device 2, the route setting device 2 is notified of the information. When the relay node 5 detects that the average congestion occurrence frequency in the past TM has exceeded the CH, the route setting device 2 performs setting of a connection passing through the corresponding link.
To send a route switching request to. The value αH is notified simultaneously with the request.

FIG. 8 is a flowchart showing an operation from when the route setting device 2 receives the route switching request to when the route switching device 2 determines the route switching. As illustrated in FIG. 8, the route setting device 2 that has received the route switching request calculates a route that bypasses the link, and a method of calculating the bypass route will be specifically described below. The route setting device 2 periodically accesses the load information database 6, acquires the load state information of each link in the ATM network 1, and updates the database 22 of the own node. The optimum route calculation unit 20 uses the database 22
And the cost f reflecting the load state of each link from the input edge node 3 to the output edge node 4 based on the information
A route that minimizes the sum of (Ni) * di is calculated. The calculated detour route is a route in which an overloaded link with high congestion occurrence frequency is bypassed and a low-load link is selected within a range that does not increase the consumption of ATM network resources.

When the calculation of the detour route is completed, the input edge node 3 calculates an index α of the ATM network resource consumed by the detour route in order to determine whether or not to switch the detour route. α is α = (each link cost f (Ni) of the detour route
* Sum of di) / (each link cost f of current route)
(Ni) * di). The input edge node 3 compares the calculated α with αH sent from the relay node 5 and determines the switching of the connection to the calculated detour route when the value is smaller than this value. Upon determining the route switching, the route switching determining unit 21 instructs the route switching unit 7 to switch the route of the connection to the calculated detour route.

By determining the route switching by comparing with such a threshold value αH, the link load on the route of the current connection is particularly high among the connections passing through the link, and the congestion occurrence frequency in the past is low. Only a connection having a bypass route that is small and has a consumption of the network resource within an allowable range compared to the consumption of the network resource of the current route is selected and the route is switched.

For this reason, a connection that must take a route having a high frequency of congestion in the past by bypassing the congested link does not change the route, so that the ATM network resources can be effectively used and the efficient ATM network 1 can be used. Can be operated. By efficiently operating the ATM network 1, it is possible to appropriately balance the load even in a situation where congestion occurs at a plurality of locations.

In this embodiment, the configuration in which one load information database 6 and the route setting device 2 are provided in the ATM network 1 has been described, but the functions of the load information database 6 and the route setting device 2 are provided in each input edge node 3. In each input edge node 3, the connection accommodated by the input edge node 3 may be configured such that the individual input edge nodes 3 execute the route control described in this embodiment autonomously and decentralized.

[0050]

As described above, according to the present invention,
The congestion occurrence information in the ATM network is collected, and the load state of each link of the ATM network estimated based on the information is used to optimize the route of the connection between the edge nodes, so that each link is optimized. The frequency of occurrence of congestion can be made uniform, and the load can be distributed.

That is, the load on the link where congestion frequently occurs due to the concentration of traffic can be distributed to the link where the frequency of occurrence of congestion is low, so that cell discards occurring in the ATM network can be reduced. The throughput of the ATM network can be improved. In this way, network resources of the entire ATM network can be efficiently used.

[Brief description of the drawings]

FIG. 1 is an overall configuration diagram of a route control system according to an embodiment of the present invention.

FIG. 2 is a block diagram of a main part of a configuration of a relay node according to the embodiment of the present invention.

FIG. 3 is a block diagram of a main part of a load information database according to the embodiment of the present invention.

FIG. 4 is a block diagram of a main part of the route setting device according to the embodiment of the present invention.

FIG. 5 is a diagram for explaining a principle of estimating a load state of each link from congestion occurrence information.

FIG. 6 is a diagram showing a change in a congestion occurrence frequency.

FIG. 7 is a diagram for explaining a function used for calculating an optimum route.

FIG. 8 is a flowchart showing an operation from when the route setting device receives a route switching request until when the route setting device determines route switching;

[Explanation of symbols]

 Reference Signs List 1 ATM network 2 Route setting device 3 Input edge node 4 Output edge node 5 Relay node 6 Load information database 7 Route switching unit 20 Optimal route calculation unit 21 Route switching judgment unit 22 Database 50 Monitor unit 51 Congestion detection unit 52 Congestion information notification unit 53 Route switching request determination unit 60 Link load status determination unit 61 Load status information storage unit for each link 62 Topology database

────────────────────────────────────────────────── ───

[Procedure amendment]

[Submission date] October 12, 2001 (2001.10.
12)

[Procedure amendment 1]

[Document name to be amended] Statement

[Correction target item name] Claim 3

[Correction method] Change

[Correction contents]

[Procedure amendment 2]

[Document name to be amended] Statement

[Correction target item name] 0022

[Correction method] Change

[Correction contents]

More specifically, the route control system according to the present invention will be described. An input edge node installed at a boundary between a connection start point and an ATM network, and an input edge node installed at a boundary between the connection end point and the ATM network. Output node, a plurality of relay nodes interposed in a transmission line between the input edge node and the output edge node, a load information database for recording load information in the ATM network, and a connection in the network . The relay node comprises: a traffic monitoring unit that monitors a traffic amount flowing into a link to which the relay node is connected; and a traffic monitoring unit that monitors the traffic amount by the traffic monitoring unit. Congestion detection means for detecting congestion of the link, and occurrence of congestion detected by the congestion detection means Congestion information notifying means for notifying the information about the load information database, and a route switching request determining means for determining whether to request a route switching from the information on the occurrence of congestion notified by the congestion information notifying means, The load information database includes: a link load state determining unit that estimates a load state of each link from the received information regarding occurrence of congestion; a unit that records a load state of the link; and a unit in the ATM network recorded according to the request. Means for transmitting link load state information, wherein the path setting device transmits the A
Means for acquiring information relating to the load status of each link in the TM network; and network resources of the current route having a lower load than the current route from the input edge node to the output edge node from the load status information of each link. Optimal route calculation means for selecting a route having a difference from the consumption amount of the permissible range as a detour route, and route switching determination means for determining whether or not switching from the current route to the detour route is possible, The link load state determination means sets the consumption of network resources of the link i (i is a number assigned to each link) as a steady load di, and is monotonic based on the congestion occurrence frequency Ni observed during the operation of the link i. The fluid load of link i calculated as a non-decreasing function is represented by f (N
means for calculating link cost f (Ni) * di as i), and link cost f (N
i) means for calculating, as an index α, a value obtained by dividing the total sum of * di by the total sum of each link cost f (Ni) * di of the current route, and setting a route switching threshold value preset in the ATM network. αH, and the route switching determining means includes means for determining that switching from the current route to the alternative route candidate is possible when α <αH.

[Procedure amendment 3]

[Document name to be amended] Statement

[Correction target item name] 0044

[Correction method] Change

[Correction contents]

The topology database 62 in the load information database 6 has information on costs di semi-fixedly given to each link, in addition to information on nodes and links in the ATM network 1. The link load state determination unit 60 calculates a cost f (Ni) * di reflecting the link load state. This cost has a value smaller than di when the load is low, and has a value larger than di when the link has a high load. Cost f reflecting the calculated link load state
(Ni) * di is recorded in the load status information storage unit 61 for each link. The load information database 6 includes the relay node 5
Each time it receives congestion information from the server, the link-specific load state information storage unit 61 is updated, and when there is a request for database information from the route setting device 2, the route setting device 2 is notified of the information. When the relay node 5 detects that the average congestion occurrence frequency in the past TM has exceeded the CH, the route setting device 2 performs setting of a connection passing through the corresponding link.
To send a route switching request to. The value αH is notified simultaneously with the request.

Continuation of the front page (72) Inventor Naoaki Yamanaka 2-3-1 Otemachi, Chiyoda-ku, Tokyo Nippon Telegraph and Telephone Corporation (72) Inventor Michihiro Aoki 2-3-1 Otemachi, Chiyoda-ku, Tokyo Date Within the Telegraph and Telephone Corporation (72) Atsushi Nishikido 2-3-1, Otemachi, Chiyoda-ku, Tokyo F-term within the Telegraph and Telephone Corporation (reference) 5K030 GA13 HA10 HC06 LB07 LB08 MB09 MC07

Claims (5)

[Claims] 1. An asynchronous transfer mode (hereinafter referred to as Asynchronous transfer mode).
Means for setting a connection in the network (Transfer Mode: ATM), and means for generating load state information of each link based on the past congestion frequency of each link in the ATM network. Means for performing, according to the route switching request, a load lower than the current route based on the load state information of each link in the ATM network and a difference between the current route and the consumption amount of network resources within an allowable range. A route control system comprising means for switching a current route to a detour route when a detour route exists. 2. The means for generating the load state information sets the consumption of network resources of a link i (i is a number assigned to each link) to a steady load di, and observes the consumption during the operation of the link i. The fluid load on link i calculated as a monotonic non-decreasing function based on the congestion occurrence frequency Ni
Means for calculating a link cost f (Ni) * di as (Ni); and summing the link costs f (Ni) * di of the detour route with each link cost f (Ni) * d of the current route.
means for calculating a value divided by the sum of i as an index α, and a route switching threshold value preset in the ATM network is set to αH. The switching means converts the current route from the current route when α <αH. 2. The route control system according to claim 1, further comprising means for switching to a detour route. 3. An input edge node installed at a boundary between a connection start point and an ATM network, an output edge node installed at a boundary between the connection end point and the ATM network, and an input edge node. A plurality of relay nodes inserted in a transmission path with the output edge node, a load information database for recording load information in the ATM network, and a path setting device for setting a connection in the network. A relay node, a traffic monitoring unit that monitors a traffic amount flowing into a link to which the relay node is connected; a congestion detection unit that detects congestion of the link according to a result of monitoring the traffic amount by the traffic monitoring unit; Notifying the load information database of information on occurrence of congestion detected by the congestion detection means A congestion information notifying unit; and a route switching request determining unit for determining whether to request a route switching based on the information on the occurrence of congestion notified by the congestion information notifying unit. Link load state determining means for estimating the load state of each link from information relating to the link, means for recording the load state of the link, means for transmitting the load state information of each link in the ATM network recorded according to the request. The path setting device comprises: means for acquiring information on the load status of each link in the ATM network from the load information database; and from the input edge node to the output edge node from the load status information of each link. Load is lower than the current route of the current route, and the difference from the consumption of network resources of the current route is within the allowable range. Route calculation means for selecting a route to be taken as a detour route; and route switching judgment means for judging whether or not switching from the current route to the detour route is possible. Is the number of network resources of each link) as the steady load di, and the flow of the link i calculated as a monotone non-decreasing function based on the congestion occurrence frequency Ni observed during the operation of the link i Load
Means for calculating a link cost f (Ni) * di as (Ni); and summing the link costs f (Ni) * di of the detour route with each link cost f (Ni) * d of the current route.
means for calculating a value obtained by dividing the sum of i as an index α, a route switching threshold value preset for the ATM network being αH, and the route switching judging means comprising: A route control system including means for judging that execution of switching from the first route to the detour route is possible. 4. The route control system according to claim 3, wherein the information on occurrence of congestion is information on a frequency of occurrence of congestion calculated from a history of occurrence of congestion. 5. The input edge node is provided with the route setting device and the load information database. The input edge node selects a detour route candidate for a connection passing through the input edge node and determines whether or not the route can be switched. 4. The route control system according to claim 3, further comprising means for performing autonomous decentralization in the route.