JPH05292109A - Connection system for call acommodated in logical path distributingly in cell asynchronous transfer network - Google Patents

Abstract

PURPOSE:To uniformize the cell communication density by sequentially estimating and comparing a percentage delay of each communication path between outgoing and incoming exchange nodes for each call according to a traffic changing time to time in various ways and selecting a communication path with a minimum estimated value so as to connect the call. CONSTITUTION:A path information reader 2 references a path table 3 based on identification information of a called exchange node from an input terminal 1 to read a coordinate of a relay exchange node forming plural communication paths to reach the called exchange node. Based on the coordinate, a load factor reader 4 references a load factor table 5 to read the load factor of a relay node of each communication path. Based on the load factor, a P delay calculation device 6 calculates a delay percentage reaching the called exchange node from its own node for each communication path. A P delay comparison minimum path discrimination device 7 compares delays based on the result of calculation and informs a minimum communication path to a cell exchange use connection table 8. Thus, the cell communication density in an in-network transmission line is uniformized.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a call connection system for accommodating logical paths in a cell asynchronous transfer network for communication in which logical paths are accommodated in a transmission line by statistical multiplexing of cells in an asynchronous transfer mode communication network and calls are connected. ..

[0002]

2. Description of the Related Art In the next-generation BISDN (high-speed broadband integrated service digital network), data transfer by the ATM (asynchronous transfer mode) system is being realized in the next-generation BISDN (high-speed broadband service integrated digital network), in contrast to conventional communication networks constructed for each service. is there.

In this ATM system, a call connection system using a virtual path system in which a plurality of semi-fixed virtual logical paths are selected for each call tends to be adopted (for example, Kenichi Sato, Satoshi Ohta, Ikuo Toisawa: "Construction of Broadband Integrated Transmission Network Using the Concept of Virtual Path", Theological Theory, J72-BI, 11, pp.904-916,
1989-11).

In the virtual path system, only the switching node called an access node is given the right to select a virtual path to perform centralized network management such as traffic monitoring in the network and control of a communication route selection table (routing table). Therefore, it is necessary to immediately search for an adaptive communication path and select or set an appropriate logical path when blockage, failure, or congestion occurs.

[0005]

The traffic in the above-mentioned BISDN has various and dynamic appearances due to the mixture of multiple traffics (multi-call types) brought about by the integrated services. In particular, when the traffic bursts locally in the network due to the concentration of broadband burst signals or the occurrence of failures, call discard due to buffer overflow is prevented, and the percent delay required for cell asynchronous transfer between the originating and terminating switching nodes. (It is a percentage value of delay, and is, for example, Yoichi Sato, Kenichi Sato: "Delay analysis of multi-node queuing system", IEICE, J71-B, 6, pp.669.
-677, 1988-06)), it is required to maintain extremely high reliability.

A distributed network (for example, Ryo Osatake, Hidehiko Tanaka: "Distributed Switching Network", Theological Theory, 51-A, 6, p.
p. 230-237, 1968-06; Ryo Osatake: "On the communication network in the advanced information age", SIJ, 65, 3,
pp. 230-233, 1982-03; Jiro Takase: ”
Path Characteristics of Basic Distributed Switching Networks ", Theological Theory, J74-B-
I, 9, pp. (See 655-665, 1991-09)
It is effective to construct a communication network that has many communication routes between the originating and terminating switching nodes.

According to the present invention, when a rapid traffic increase locally occurs due to the concentration of broadband burst signals in the cell asynchronous transfer communication network or the occurrence of a failure, the cell asynchronous transfer is performed by avoiding the sudden traffic increase region. In order to suppress cell discard and increase in cell delay due to buffer overflow at the relay switching node, the logical paths are always distributed and accommodated in a plurality of communication routes (transmission paths) between the source and destination switching nodes for each call. A call connection method for distributed logical paths in a cell asynchronous transfer network for the purpose of connecting calls so that the cell flow densities of transmission lines in the network are equalized.

[0008]

The above objects of the present invention can be achieved by the means described below.

A plan schematic diagram of one embodiment of a typical cell asynchronous transfer network having a plurality of communication paths between originating and terminating switching nodes is shown in FIG. FIG. 2 is an example of a grid communication network, in which switching nodes are arranged at points where links arranged in a grid intersect.
For a call made at each switching node, if the required transmission line capacity declared by the call can be accepted, the switching node distributes the logical path to the destination switching node for each call and accommodates it in the communication path. And connect the call.

FIG. 3 shows the relationship with the incoming route when paying attention to the one outgoing route in each switching node. FIG. 3 is an example of a schematic diagram of a cell exchange adopting an output buffer format, and a circle symbol in the figure is also called a server. The load factor (also called transmission line utilization efficiency) due to the cell signal arriving at the buffer input is measured for each relay switching node in each of the plurality of communication paths between the originating and terminating switching nodes.

This load factor is obtained by dividing the number of cells arriving during an appropriately determined observation time length by the observation time length and multiplying the service time (usually the time length of one cell). A value larger than 0 and smaller than 1 is usually used. When the load factor takes a value of 1 or more, it is usually referred to as a heavy load and means a congestion state that exceeds the capacity of the communication network, which exceeds the range of the problem to be solved by the present invention.

FIG. 4 is a schematic plan view showing one embodiment of M communication paths that can be set up between the originating and terminating switching nodes in FIG.
Table 1 shows an example of a communication path table corresponding to each of the M communication paths.

In Table 1, for each of the M communication paths, the originating switching node is counted as the first node, and the relay switching nodes are sequentially numbered toward the terminating switching node. When the number of relay stages is included, the coordinates (X,
Y) is displayed using the coordinates shown in FIG.

Each switching node in the cell asynchronous transfer communication network measures the load factor for the cell arriving at its own node,
The traffic information notification logical paths notify each other. Each exchange node updates and stores the load factor in the load factor table whenever it receives the notification.

Each switching node in the cell asynchronous transfer communication network can reach the destination switching node from its own node by reading the identification information of the destination switching node from the arrived cell and referring to the communication route table. Know a plurality of communication paths and relay switching nodes forming each communication path.

Each load factor in the relay switching node forming each communication path is read from the load factor table, and the percent delay between the originating and destination switching nodes is estimated by calculation based on the load factor.

The communication path exhibiting the minimum estimated percent delay is determined by comparing the estimated results of the percent delay for each communication path.

The arriving cell is connected to one of the communication paths having the smallest percent delay according to the determination result, and the cell is sent to the destination switching node of the cell.

The cell asynchronous transfer according to claim 1, wherein the connection processing is performed in each relay switching node including the originating switching node up to the destination switching node with respect to the cell having the task of accommodating the logical path. 3. The call connection method for accommodating logical path distribution in a network or the call connection method for accommodating logical path distribution in a cell asynchronous transfer network according to claim 2, which is performed based only on load factors on a plurality of outgoing routes of each relay switching node. The above object of the present invention is achieved by the logical path distributed accommodating call connection system in the cell asynchronous transfer network according to claim 3, which is performed only by the switching node on the originating side when selecting or setting the virtual logical path.

[0020]

For each of a plurality of communication paths from the switching node in the communication network to the destination switching node, the percentage required for cell asynchronous transfer by each communication path based on each load factor in the relay switching node in each communication path. In order to estimate the delay, the following preparations are made in advance.

First, 100 × P percent to be evaluated is selected from the range of 0 <P <1. This value P is
Usually, it is determined based on the specified loss rate of the cell with reference to the allowable discard rate of the cell due to buffer overflow.

Next, the weighting factor α (i, P) for the i-th stage relay switching node counting from the source switching node to the destination switching node in each communication path; i = 1, 2,
3 ,. ． ． , And the weighting coefficient β (1, P) of the first stage. Examples of weighting factors for 99 percent delay (P = 0.99) are listed in Table 2. It should be noted that the values of these weighting factors include the characteristics of the statistical multiplexing method peculiar to the ATM method (for example, Hiroshi Yamada, Hiroshi Saito, Masatoshi Kawaharazaki: "AT
Analysis of Traffic Characteristics in M Network ", NTT, R &
D, 40, 12, pp. 1571-1580, 199
1; Yoichi Sato, Kenji Nakagawa, Naoaki Yamanaka, Kenichi Sato: "AT
CBR path accommodation design method in M network ", IEICE Technical Report, C
The correction value is added or subtracted according to S91-4, 1991-05).

Under the above preparation, a normalized estimated value x _N of 100 × P percent delay between the originating and terminating switching nodes according to the service time is calculated according to the number N of relay switching nodes forming each communication path. Based on the load factor ρ _i at each i-stage relay switching node, calculation is performed by the following formula or formula. However, the relay stage number N includes either the originating exchange node or the terminating exchange node. Which gora is included depends on whether each relay switching node has an output buffer format or an input buffer format.

When N = 1, x ₁ = β (1, P) [1+ {α (1, P) / 2} ρ _i / (1-ρ _i )]. ． ． ． ． ． If N ≧ 2, then x _N = β (1, P) [1+ {α (1, P) / 2} ρ _i / (1-ρ _i )]

For each call in the network, for each of the plurality of communication paths between the originating and terminating switching nodes, 100 ×
By obtaining the estimated value x _N of P percent delay, comparing them, and accommodating the logical path in one of the communication paths (transmission paths) exhibiting the minimum value, the logical paths are distributed over the transmission paths in the network. A call connection can be accommodated.

[0026]

Embodiments of the present invention will now be described in detail with reference to the drawings.

FIG. 1 is a schematic configuration diagram of an embodiment of a connection table creator for a cell switch in the logical path distributed accommodating call connection system in the cell asynchronous transfer network of the present invention.

According to the first aspect and the second aspect of the present invention, in the logical path distributed accommodating call connection method within the cell asynchronous transfer network, each relay switching node including the originating switching node accommodates the arrived logical path. Refer to the identification information of the required transmission line capacity of the cell signal that is responsible for the task, discard the cell signal if the node cannot accept it, and discard the cell signal if the node can accept it. The identification information signal of the destination switching node is applied to the input terminal 1.

In the call connection system for accommodating logical paths in a cell asynchronous transfer network according to the third aspect of the present invention, when the originating switching node cannot accept the required transmission line capacity of the call, If the call is rejected and the call can be accepted, the identification information signal of the destination switching node is added to the input terminal 1.

The route information reader 2 refers to the route table 3 on the basis of the identification information of the destination switching node, and coordinates of the relay switching node forming a plurality of communication routes that can reach the destination switching node. The information is read and transmitted to the load factor reader 4.

The load factor reader 4 refers to the load factor table 5 on the basis of the coordinate information of the relay switching node of each communication route, reads the load factor at the relay switching node of each communication route, and P
It is transmitted to the delay calculator 6.

The P delay calculator 6 calculates the 100 × P percent delay from the own node to the destination switching node for each communication path based on the load factor of the relay switching node of each communication path. , And transmits the calculation result to the P delay comparison / minimum path determiner 7.

The P delay comparison / minimum path judging unit 7 compares 100 × P percent delays of the respective communication paths, judges the communication path having the minimum value, and selects one communication path among the communication paths for the cell switching system. Notify 8.

In the logical path distribution accommodating call connection system in the cell asynchronous transfer network according to the above-mentioned claim 1 and claim 2, the connection table 8 for the cell exchange shows the outgoing path (transmission path) of the communication path exhibiting this minimum delay. Outgoing route number information for connecting the call to, the identification information of the originating switching node and the identification information of the terminating switching node for identifying this call, and the information regarding the required transmission line capacity are registered. The information on the required transmission line capacity for declaration is provided for the acceptance judgment of the subsequent call.

In the call connection method for accommodating logical paths in the cell asynchronous transfer network according to the third aspect of the present invention, the connection table 8 for the cell exchange is provided with a virtual connection for connecting the call to the virtual logical path of the communication path exhibiting the minimum delay. The logical path identification information and the information about the required transmission line capacity are registered. The information on the required transmission line capacity for declaration is provided for the acceptance judgment of the subsequent call.

In the call connection method for accommodating the logical paths in the cell asynchronous transfer network according to the first and third aspects,
An information signal concerning the load factor in each switching node, which is notified from all the switching nodes in the network, is added to the input terminal 9 and updated and stored in the load factor table 5 at any time.

In the call connection method for accommodating the logical paths in the cell asynchronous transfer network according to the second aspect, an information signal relating to the load factor for the buffer on the outgoing route (transmission route) side is added to the input terminal 9 to load the load factor. It is updated and stored in Table 5 as needed. This output side buffer exists in the own node if each switching node adopts the output buffer format, and exists in the next stage relay switching node if each switching node adopts the input buffer format.

[0038] In the call connection system for accommodating the logical paths in the cell asynchronous transfer network according to the first and third aspects,
The route table 3 stores the coordinate information of the relay switching nodes forming the plurality of communication routes from the own node to the other switching nodes.

In the call connection method for accommodating logical paths in a cell asynchronous transfer network according to the second aspect of the present invention, the route table 3 shows that the outgoing routes of a plurality of communication routes from the own node to each of the other switching nodes. (Transmission path) number information is stored as a substitute for the coordinate information.

[0040]

As described above in detail, according to the present invention, in the cell asynchronous transfer communication network having a plurality of communication paths between the originating and terminating switching nodes, each communication between the originating and terminating switching nodes for each call. Since the percent delay of the route is sequentially estimated and compared with respect to the traffic which changes variously from moment to moment, and the communication route with the smallest estimated value is selected to connect the call,
Logical paths are distributed and accommodated in communication paths (transmission paths),
While the cell flow density of each transmission line in the network is equalized,
Depending on the selected communication path, the percent delay required for cell asynchronous transfer between the originating and terminating switching nodes approaches the minimum, and the buffer capacity of each relay switching node is set to be substantially equal to FIFO (First in first out).
When adopting the service discipline described in (1), cell discard due to buffer overflow can be suppressed.

[Brief description of drawings]

FIG. 1 is a schematic diagram showing an embodiment of a connection table creator for a cell exchange according to the present invention.

FIG. 2 is a schematic plan view showing an embodiment of a cell asynchronous transfer network having a plurality of communication paths between originating and terminating switching nodes according to the present invention.

FIG. 3 is a schematic diagram showing an embodiment of a switching node when paying attention to one outgoing route of the switching node in the present invention.

FIG. 4 is a schematic plan view showing one embodiment of M communication paths that can be set between the originating and terminating switching nodes in the present invention.

[Explanation of symbols]

 1 Identification information signal input terminal 2 Path information reader 3 Path table 4 Load factor reader 5 Load factor table 6 P delay calculator 7 P delay comparison / minimum route determiner 8 Cell switch connection table 9 Load factor information signal Input terminal

[Table 1]

[Table 2]

Claims (3)

[Claims] 1. A call originating in a communication network in which data is asynchronously transferred by using a cell (fixed length block with header) signal having at least identification information of the terminating exchange node, reaches the terminating exchange node of the call. One of a plurality of possible communication paths, which is responsible for accommodating the logical path for the call connection, at least the identification information of the originating switching node of the call and the identification information of the destination switching node, and the call is declared. In the method of asynchronously transferring a cell signal having identification information about the required transmission line capacity toward the destination switching node of the call, at each relay switching node including the originating switching node through which the cell signal passes, the cell signal Among the plurality of communication paths that can reach the destination switching node from each relay switching node, the relays through which the communication paths can pass for the plurality of communication paths that can receive the declared required transmission path capacity The delay (in-system time) is estimated for each communication path based on the load factor related to the cell in the exchange node, the estimated values are compared, and the identification is made to one of the communication paths having the smallest estimated value. The call is connected after accommodating the logical path by gradually repeating the procedure of registering information and connecting the cell signal to the communication path until the cell signal reaches the destination switching node. A call connection method that accommodates distributed logical paths in a cell asynchronous transfer network. 2. A method of asynchronously transferring a cell signal, which is responsible for accommodating a logical path for call connection, to a destination switching node of the call in response to a call in the communication network. The relay switching node including the originating switching node through which the signal passes can accept the declaration required transmission path capacity among a plurality of communication paths through which the cell signal can reach from the relay switching node to the destination switching node. For the plurality of communication paths,
The load factors relating to the cells of the respective egress route (transmission route) side buffers of the respective relay switching nodes are respectively compared, and the identification information is registered in one of the communication routes having the smallest load factor and the cells are 2. The cell asynchronous transfer network according to claim 1, wherein the call is connected after accommodating the logical path by gradually repeating a procedure for connecting a signal until the cell signal reaches the destination switching node. Internal logical path distributed accommodation call connection method. 3. For a call originating in the communication network, a virtual logical path is preset in each of a plurality of communication paths between a call-originating exchange node and a call-originating exchange node of the call. In the method of selecting one, regarding a plurality of the communication paths capable of accepting the required transmission path capacity declared by the call among the plurality of communication paths, the load on the cell in each relay switching node through which the communication path passes A delay is estimated for each of the communication routes based on a rate, the estimated values are compared, and the identification information of the call and the required transmission are transmitted to one of the communication routes having the smallest estimated value. 2. The logical path in the cell asynchronous transfer network according to claim 1, wherein the call is connected after accommodating the virtual logical path as a logical path for the call connection by registering identification information regarding the path capacity. Distributed accommodation call connection method.