JP2741913B2 - Routing control method in ATM communication - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION [Overview] Regarding a routing control method in an asynchronous transfer mode (ATM), a routing control method of an ATM communication which can improve a network throughput without deteriorating the quality of service required for the ATM communication. The ATM communication control unit has a load / variation value storage unit for each route that holds the load added to each of all outgoing routes and load fluctuation information, and is declared by a connection request call. When the attribute parameters are received by the declaration parameter holding means,
The load value and load change newly added to all output paths are calculated by the change value calculating means using the information of the load and change value storage unit for each route, and the load and the change value calculated for each route are calculated by the optimum route selecting means. To select a route in which both numerical values are smaller than each other.

The present invention relates to a routing control method in asynchronous transfer mode (ATM) communication.

In recent years, broadband Integrated Services Digital (ISDN)
ATM (Asynchronous Tra)
nsfer Mode) has been actively researched. Routing control is one of the traffic control methods of ATM communication.

There are two types of routing control, one for use in determining a route when setting up a call, and the other as one of congestion controls, for use in changing a route during congestion. However, a route already set for both purposes is used. Is unfavorable because it causes the cell order to be reversed.
Therefore, routing at the time of call setting that does not require cell order preservation processing is important.

On the other hand, in ATM communication, various traffics with different bearer speeds and burstiness of information, such as voice, data, and moving images, are treated in a unified manner. There is a problem that the service becomes larger and the quality of the required service is reduced.

[Prior Art] In ATM communication, a fixed-length (for example, 64 bits) packet called a cell is inserted into a vacant time slot for transfer, and the effective transfer rate is increased by increasing or decreasing the number of cells. Can be changed. A cell is composed of a header and data, and the header includes information such as a destination.

The network exchanges each cell only by looking at the contents of the header.
Deliver to the other party. In this case, a continuous signal such as a voice or a moving image is also converted into cells and transferred, and the receiving side returns to a continuous signal form again.

In ATM communication, information with various characteristics is transmitted as described above, and information with extremely high communication speed (several tens of MHz like moving images) and information with low speed such as voice are transmitted on the transmission path. They are mixed and transmitted. In this case, in addition to continuously generated information (data communication information), intermittently generated bursty information (such as voice and video information) is present, so that a transmission path for multiplexing and transferring cells is transmitted. Routing control is needed.

In conventional ATM communication, ATM communication itself is a new technology, so it cannot be cited as a routing control method.However, traffic control and congestion control technologies used in conventional circuit switching and synchronous packet switching are not used. It can be used. That is, in the case of circuit switching, it is a method of determining whether or not the line is occupied and selecting an outgoing route. In the case of packet switching, how many packets are currently allocated to the transmission route of the outgoing route. By calculating the coefficient, it is possible to adopt a method of selecting a transfer path having a free space.

[Problems to be Solved by the Invention] As described above, in the ATM communication (the ATM communication network and the switch of the ATM exchange), information of different speeds and characteristics (continuity or burstiness, etc.) is transferred, so that the connection request is transmitted. There is a problem in routing control for selecting which route the generated call (cell) is assigned to.

That is, when a connection request call having a high speed and a high burst property is assigned to a certain route, it depends on the characteristics (burst property and transfer speed) of a plurality of calls that have been transferred up to that point, but the time of occurrence of many cells is different. The overlap (peak) exceeds the transmission capacity (transmission capacity), and in that case, cell discard (cell is discarded without being transferred) occurs. Such cell discard can be avoided by increasing the capacity of a buffer provided in the network, but is not preferable in the case of information requiring real-time characteristics such as voice due to a large delay time.

On the other hand, if routing control is performed so that the maximum peak at which the cell generation time overlaps is always smaller than the transfer capacity of the transmission path, network throughput can be maximized from the viewpoint of efficiently using the common resources in the network. Can not do.

The present invention provides an ATM capable of improving network throughput without deteriorating service quality required for ATM communication.
An object of the present invention is to provide a communication routing control method.

[Means for Solving the Problems] FIG. 1 is a diagram illustrating the basic configuration of the present invention, and FIG. 2 is a diagram illustrating the principle of the present invention.

In FIG. 1, 10 is a communication control unit, 11 is a report parameter holding unit, 12 is a load / variation value calculation unit, 13 is an optimal route selection unit, 14 is a load / variation value storage unit for each route, 15 is a temporary memory, Reference numeral 16 denotes a route switching unit.

The present invention is configured so that the information of the connection request call is provided with the attribute parameter included in the call as the report information, and the control device of the ATM communication obtains the load and the variation rate in the attribute parameter of the report information, and outputs each information. Calculate each numerical value when the call is newly added to the data of the current load and the fluctuation rate of the route, and select the route having the smallest numerical value and control the transfer of the call. Things.

[Operation] Before explaining the operation of FIG. 1, the principle of the present invention will be described with reference to FIG.

FIG. 2A shows a burst traffic model. This is shown in order to consider the maximization of the network throughput by the multiplexing characteristics of the burst traffic. Α ^{-1 in the} figure
(= 1 / α) is the average burst duration, β ⁻¹ (= 1 / β) is the average burst generation interval time, T is the celling time, and Nc (= α)
⁻¹ / T) represents the average number of cells generated during the burst duration.

FIG. 2B shows how the traffic load on the transmission line changes with time when such burst cells and continuous cells are multiplexed and transmitted. As described above, the load fluctuates due to the burst data, and if the amplitude of the fluctuation is large, a situation where the transmission capacity is exceeded (cell discarding occurs) occurs.

Therefore, a multiplexing characteristic is obtained by using a square variation coefficient (indicated by SVC) of a cell generation interval as an index indicating the degree of burst of such burst traffic. This coefficient of variance is defined as the variance / (square of the mean)
Indicates the ratio of fluctuation to the average, and is represented by, for example, the following equation.

This square variation coefficient SVC and burst characteristics are shown in Fig. 2C.
And the burst parameter γ = β ⁻¹ / α ⁻¹
It can be seen that the larger the ratio is, and the larger the Nc, the larger the square variation coefficient. The cell discard rate increases as the coefficient of variation increases and as the average number of generated cells increases.

Thus, it can be seen that in order to maximize the network throughput, it is necessary to balance at least the cell load (the number of generated cells) of each route. But AT
In M communication, since various calls with different bands and burst characteristics are handled, maximization cannot be realized only by balancing the cell load (the number of generated cells). Therefore, in the present invention, calls are allocated so that the variation coefficient of each route is also balanced.

Together with these, in the present invention, the principle of routing control is to balance the cell load and the coefficient of variation of cell generation in each route.

Next, the operation of FIG. 1 will be described. The basic configuration of FIG. 1 is not limited to the routing control method of the transmission line connecting the exchanges constituting the ATM communication network, but also to the switches constituting the ATM exchange. This is a configuration that is also applied to a link routing control method in (including a case where it is configured in a plurality of stages).

A connection request call from a terminal or a transmission path firstly (at the time of occurrence of the request) declares attribute parameters of its own call. This attribute parameter includes peak bandwidth (highest transfer rate
V _P ), average burst duration (α ^-1 ), average burst interval time (β ^-1 ), average number of cells generated during burst duration (Nc), or average load (a) The information of the variation coefficient (same as the above-mentioned square variation coefficient SVC) is used.

The average load is given by, for example, the following equation, and _VT is the maximum bandwidth (speed) of the transmission path.

The above-mentioned report parameters are stored in the report parameter storing means 11 of the communication control unit 10 of the ATM. The report parameters are then supplied to the load / variation value calculation means 12, and the current load and variation values for each route are extracted from the load / variation value storage unit 14 for each route. Calculate the load (average load) and the fluctuation value (corresponding to the square variation coefficient in FIG. 2) that occur in each route when is connected. That is, the load (average load) due to the connection request call is obtained by the above equation (1), and the fluctuation value is obtained by the above equation (2). This calculation is performed for all possible routes, and the result is stored in the temporary memory 15.

When the calculation of the load and the fluctuation value for each route is completed, the optimum route selection means 13 next looks at the calculation result stored in the temporary memory 15 and selects the route having the least load and the fluctuation value. In this case, the selection method can be arbitrarily selected, but a method of examining one of the load and the fluctuation value and selecting the route having the smallest value may be used.

When the optimal route is selected, the information is sent to the route switching unit.
The connection request cell is supplied to 16 to switch and connect the cell of the connection request call to the selected outgoing route.

As described above, in the present invention, with respect to the current load and fluctuation value of each route, calculation is performed for each candidate route based on the load and fluctuation value which are the parameter information declared from the connection request call, and the result is calculated. By selecting the route having the smallest load and the fluctuation value from among the above, the load and the fluctuation between the routes can be made uniform, and the throughput in the ATM communication can be improved.

[Embodiment] FIG. 3 is a control flow chart of a call connection request of the embodiment, FIG. 4 is a control flow chart of a call termination request of the embodiment, and FIG.
FIG. 6 is a configuration diagram of an ATM switch according to the embodiment, FIG. 7 is a configuration diagram of an ATM switch according to the embodiment, and FIG. 8 is a configuration of a database used for the ATM communication network / switch of the embodiment. FIG. 9 is a configuration diagram of a database used in the embodiment of the ATM switch.

The control flow of the call connection request shown in FIG. 3 and the control flow of the call termination request shown in FIG. 4 correspond to the configuration (ATM communication network, ATM exchange and ATM switch) of each embodiment shown in FIGS. Of the control device. FIG. 8 (ATM communication network routing control and A
It is stored as a database having the contents shown in FIG. 9 (routing control of the TM exchange) or FIG. 9 (routing control of the ATM switch), and is stored in the database shown in the configuration of each embodiment of FIGS.

Referring to the call connection request control flow of the embodiment shown in FIG. 3, when performing ATM communication from the terminal side, a call connection request and information on a call attribute parameter declaration are transmitted to the ATM communication network (step 30). This is accepted by the communication network (step
31) and in the control device, using the report parameters and the load and load variation information of each data route of the database,
The newly added load and load fluctuation are calculated for all outgoing routes (step 32).

 An example of this calculation will be specifically described.

Call i is the time of the call, V _P (peak bandwidth), alpha ^-1 (average burst duration), when filing beta ^-1 (average burst generation interval time), the first view, described above for FIG. 2 ( " Action), and calculates the average load a _i and the variation SCV _i of the call i by the equations (1) and (2). Next, the sum A _{i−1, j} of the average load and the sum C of the variation of the calls already accepted for each route
_{i−1, j is obtained} by the following equation. However, it is assumed that i-1 calls are accepted for route j.

The sum of the average load and the sum of the variations are referred to as _ai and SCV _i , respectively.
Can be added to determine the load and fluctuation when the call for which the connection request has been made is connected to the route. In addition,
When the information on the average load and the fluctuation is included as the report information from the terminal, the above calculation is performed using the information. The calculation result of each outgoing route obtained in this way is stored in a memory (not shown) included in the control device.

Next, the load of each route obtained as a result of the calculation and the value of the variation are compared, and an outgoing route having a uniform load and a minimum load variation is selected (step 33). That is, the sum A _{i−1, j} + a _i of the average load of each route and the sum C _{i−1, j of the} fluctuations
Find the route j that minimizes + SCV _i .

When an outgoing route is selected, the database (subscriber information and outgoing route information) is updated with the report parameters of the connection request call.

Subsequently, communication path control is performed to connect the call of the connection request to the selected outgoing route (step 35).

Next, a control flow of a call termination request in the embodiment shown in FIG. 4 will be described.

When a termination request is transmitted from the terminal (step 40), the network receives the termination request (step 41). Subsequently, the call for the termination request is searched from the subscriber information in the database (step 42), and when detected, the load and load fluctuation are calculated by terminating the call based on the declared parameters of the terminating subscriber (step 42). Step 43). In this case, the value of the subscriber is removed from the data on which the calculation of the load and the load fluctuation is based, and the calculation is performed only with the data of the other currently connected calls.

When the calculation result is obtained, the outgoing route information (stored in the database) is updated based on the calculation result (step 44). Subsequently, the subscriber whose call is to be terminated is deleted from the subscriber information (stored in the database) (step 45).

Next, the configuration of the ATM communication network shown in FIG. 5 will be described. In FIG. 5, reference numerals 50 to 52 denote telephone terminals, data terminals, image terminals, and the like installed on the terminal side. The network termination device 53 connects to the ATM communication network. The ATM communication network is connected to a plurality of ATM exchanges 54 via a transmission path, and performs cell transfer. Each ATM switch has 5 databases
5 is provided to store subscriber information (parameter information declared from the terminal) and outgoing route information according to the present invention.

FIG. 6 is a block diagram of the ATM switch of the embodiment, in which the line from the network terminating device 60 accommodating the terminals of each subscriber is connected to the multiplexer (indicated by MUX) 61 of the switch and multiplexed. The data is input to the ATM switch 63, switched and connected, and output to the destination terminal or the outgoing route to the exchange. 62 is a signal processor (indicated by SIG), 64 is a call controller (indicated by LPR) that controls an ATM switch 63, 65 is a call processor (indicated by CPR) that performs routing control according to the present invention, and 66 is 5 is a database storing subscriber information and outgoing route information used for routing control according to the present invention.

ATM communication network and ATM shown in FIG. 5 and FIG.
FIG. 8 shows the configuration of the database used in the routing control of the exchange.

A in FIG. 8 is subscriber information, which stores various types of information on accepted calls (connected calls) in response to a call connection request from each subscriber. That is, as shown in the figure, it is composed of a subscriber line number (indicated by NO), a call number, an outgoing route number, and each value representing a characteristic of a peak band, an average band, and a burst as a report parameter value. Here, information of all the subscribers who originated the accepted call is stored, and is deleted when the call is terminated.

Outgoing route information is shown in B. of FIG. 8, and for each outgoing route, the outgoing route number (indicated by NO), the outgoing route load,
Each piece of information on the load variation of the outgoing route is stored for all outgoing routes.

FIG. 7 shows a configuration diagram of the ATM switch of the embodiment. This A
The TM switch is a specific configuration example of the ATM switch in the exchange shown in FIG.

The ATM switch in FIG. 7 has a multi-stage switch configuration,
In the figure, 70 is a multiplexer MUX, 71 is a first stage switch, 72 is a primary link, 73 is an intermediate switch, 74 is a secondary link, 75 is a last stage switch, 79 is a link information database, 80 is subscriber information And 76 to 78 in FIG.
The same thing as 62 (SIG), 64 (LPR), and 65 (CPR) is also shown.

In the case of the ATM switch shown in FIG. 7, the input connection request call is output from the first-stage switch 71 via the primary link 72, the intermediate switch 73, the secondary link 74, and the final-stage switch 75 to the outgoing route.

The switch control is executed under the control of the call path control device (LPR) 77, and the call processing device (CPR) controls the routing control as to which of the primary link 72 and the secondary link 74 is connected to the outgoing route. Perform at 78. Call processing device 7
8 is provided with a database 79 of link information and a database 80 of subscriber information, and the processing according to the control flow shown in FIGS. 3 and 4 is performed.

FIG. 9 shows the configuration of a database used in the embodiment of the ATM switch.

9A shows a database of subscriber information.
In response to a call connection request from each subscriber, various types of information on the accepted call (connected call) are stored. The contents are the same as those in FIG.

FIG. 9B stores information on the link number, the load, and the load variation for all of the primary link 72 and the secondary link 74 of the ATM switch. AT shown in Fig. 7
In the routing control of the M switch, in step 33 of the control flow shown in FIG. 3, an outgoing route having a uniform load and a minimum load variation is selected, but matching between the primary link and the secondary link (connection of both links) Is possible)
It is necessary to make a decision to take

When the primary link and the secondary link with the minimum load and fluctuation are matched, the call processing device 78
A control signal is output to the call path control device 77, the first-stage switch to which the call for which the connection request was made is connected and the respective switches 71, 73 and to connect the selected primary link and secondary link and outgoing route Drive one of each of the 75.

[Effects of the Invention] According to the present invention, the cell discard rate in the entire ATM communication network can be reduced, so that the network throughput can be improved. Further, the cell discard rate in the ATM switch and the ATM switch can be reduced, and the delay can be reduced.

That is, the smaller the load, the smaller the cell discard rate,
This is because the smaller the fluctuation, the smaller the cell discard rate.

[Brief description of the drawings]

FIG. 1 is a basic configuration diagram of the present invention, FIG. 2 is a diagram for explaining the principle of the present invention, FIG. 3 is a control flow diagram of a connection request call in the embodiment, and FIG. 4 is a control flow of a termination request in the embodiment. FIG. 5, FIG. 5 is a configuration diagram of an ATM communication network of the embodiment, FIG. 6 is a configuration diagram of an ATM switch of the embodiment, FIG. 7 is a configuration diagram of an ATM switch of the embodiment, FIG.
FIG. 9 is a configuration diagram of a database used for the ATM communication network / switch of the embodiment, and FIG. 9 is a configuration diagram of a database used for the embodiment of the ATM switch. In FIG. 1, 10: communication control unit 11: report parameter holding unit 12: load / variation value calculation unit 13: optimal route selection unit 14: load / variation value storage unit for each route 15: temporary memory 16: route switching unit

 ────────────────────────────────────────────────── ─── Continuation of the front page (56) References JP-A-3-70331 (JP, A) JP-A-2-27847 (JP, A) JP-A-2-2688537 (JP, A) IEICE Technology Research report, IN 88-64 Proceedings of the IEICE Autumn National Convention, B-159 (1989-8-15)

Claims (3)

(57) [Claims] In a routing control method in asynchronous communication mode (ATM) communication, a call connection request information includes an attribute parameter related to a load and a load change of the call as report information, and an ATM communication control unit (10). Is the load added to each of all outgoing routes and the load for each route that holds the load fluctuation information.
A variable value storage unit (14), and when the attribute parameter declared by the connection request call is received by the report parameter holding unit (11), the load / variation value calculation unit (12) loads the load / variable value by route.
Using the information in the fluctuation value storage unit (14), newly added loads and load fluctuations are calculated for all output paths, and the calculated load and fluctuation value for each route are compared by the optimum route selection means (13). A routing control method in ATM communication, characterized in that a route having both small numbers is selected. In a routing control method in an ATM communication network in which a plurality of ATM exchanges are connected by a transmission line, a call attribute parameter is notified from the transmission line to the ATM communication network at the time of a call connection request, and a control device for the ATM communication network is provided. Comprises a database storing the load and load fluctuation information added to each of all outgoing routes of each ATM exchange constituting the communication network, and the control device, when there is the connection request call, its attribute parameters and the Using the information in the database, calculate the newly added load and load fluctuation information for each data route, select the route that minimizes the load fluctuation at the same time as equalizing the load on each outgoing route and notify the corresponding ATM switch A routing control method in an ATM communication network. 3. A routing control method in an asynchronous transfer mode (ATM) exchange, wherein a subscriber terminal sets a call attribute parameter to an ATM upon a call connection request.
Notifying the exchange, the control device of the ATM exchange includes a database that stores the load applied to each of all the links of each ATM switch and load fluctuation information, and the control device, upon receiving the connection request call, Using the attribute parameters and the information of the database, a load to be newly added and load fluctuation information are calculated for each link, and the load of each outgoing route is equalized, and at the same time, a route that minimizes the load fluctuation is selected and exchange control is performed. AT characterized by performing
Routing control method in M switch.