JP3171569B2 - ATM communication network - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention relates to an ATM (Asynchronou).
s Transfer Mode). In particular, CAC (Connectio
n Admission Control) technology.

[0002]

2. Description of the Related Art In an ATM communication network, communication is performed by setting a connection in a VP (Virtual Path), but the bandwidth of the connection can be flexibly changed according to the traffic situation at that time. Therefore, when the communication terminal requests a connection setting from the originating exchange, the exchange checks the presence or absence of the required bandwidth of the communication terminal with the transit exchange and / or the destination exchange to confirm.
In the transit exchange and / or the exchange on the receiving side, it is necessary to secure the required bandwidth. This control is called CAC. Here, the transmission path refers to a physical path through which an electric signal or an optical signal is transmitted. The VP is a virtual information path set in a plurality of transmission paths. The connection refers to a virtual information path connecting a plurality of communication terminals set in the VP. A route is a route on a transmission path through which this connection passes.

The operation of CAC in a conventional ATM communication network will be described with reference to FIGS. FIG. 9 is a diagram showing the relationship between the communication terminal, the originating and terminating exchanges, and the transit exchange. FIG. 10 is a diagram showing various service classes. FIG. 11 is a diagram for explaining the operation of the conventional CAC. As shown in FIG. 9, the communication terminal TE is accommodated in the originating and terminating exchanges LS. A transit exchange TS is arranged on the transmission path between the exchanges LS.

[0004] A VP is set on a transmission line connecting the originating and terminating exchanges LS, and a plurality of connections are set in the VP. When a plurality of service classes are set according to the priority of cell transfer, as shown in FIG. 10, a band is assigned to each service class in the VP. QoS (Quality of Service) H is the highest priority class, and is a service class permitted to use the entire band of the VP. QoSL is a service class next to QoSH, and is a service class that is permitted to use a band excluding the QoS usage band from the entire VP band. The best effect is a low-priority class, and is a service class that is permitted to use a band obtained by excluding the bands used by QoS and QoSL from the entire band of VP.

[0005] As shown in FIG.
Then, negotiation between the required quality and the required band is performed using a signaling packet. In the example of FIG. 11, QoS (highest priority class) requires 10 Mb / s.

[0006] In the conventional ATM communication network, it is sequentially calculated whether or not connection to the transit exchange TS is possible at 10 Mb / s and QoS. As a result of the calculation, if the band is secured, a signal indicating acknowledgment is sent to the communication terminal TE on the calling side to perform communication (actual information transfer).

[0007]

SUMMARY OF THE INVENTION Such a conventional AT
In the M communication network, when the bandwidth is insufficient, the CAC is performed again after waiting for a response for a long time. That is, conventionally, there are two major problems. (1) WA
In a network with a large RTT (Round Trip Time), such as N, the CAC time is long and it takes time to start communication. (2) When there are many QoS classes, it takes a lot of time to calculate, and this actually limits the number of QoS supports.

[0008] The present invention has been made in such a background, and an AT capable of performing high-speed CAC and performing connection setting appropriately corresponding to the state of the network at that time.
It is intended to provide an M communication network. The present invention relates to a WA
N even if a large network such as N is configured
An object of the present invention is to provide an ATM communication network capable of reducing the time of C. SUMMARY OF THE INVENTION An object of the present invention is to provide an ATM communication network that can reduce the CAC time even when a plurality of service classes are mixed. An object of the present invention is to provide an ATM communication network that can select an optimum route when a plurality of routes exist.

[0009]

SUMMARY OF THE INVENTION According to the present invention, a user is provided with a CA.
When the request for C is not made, the most important feature is that the CAC is virtually performed, and at least the originating exchange accommodating the communication terminal recognizes at least the band where the CAC is currently available.

[0010] The prior art is that when a user requests a CAC, the result can be returned only by the originating exchange accommodating the communication terminal, and the bandwidth available for CAC in each route is periodically changed by the originating exchange accommodating the communication terminal. What the exchange recognizes is different. Another difference is that the CAC time does not increase depending on the size of the WAN and the number of service classes.

That is, the present invention relates to an ATM communication network comprising an originating and terminating exchange for accommodating a communication terminal, and a transit exchange provided on a transmission line connecting the originating and terminating exchanges. Wherein the originating exchange is an ATM communication network having means for receiving a connection setting request from the communication terminal and searching for the presence or absence of the requested band. A feature of the present invention is that the searching means includes means for periodically searching for the presence or absence of a predetermined band regardless of the presence or absence of a connection setting request of the communication terminal. It is preferable that the searching means includes a table for recording a search result.

[0012] Thus, the originating exchange accommodating the communication terminal always recognizes the presence or absence of the band, and can quickly respond to the connection setting request from the communication terminal by the judgment of the originating exchange alone. it can.

[0013] The means for searching for the presence or absence of the predetermined band includes:
Means for inquiring the transit exchange and / or the destination exchange of the presence or absence of a predetermined band.The transit exchange and / or the destination exchange receives the inquiry and determines whether or not the predetermined band is present or not. It is desirable to have a means for responding to the request and a means for securing the band.

However, it is not preferable from the viewpoint of effective use of the network that the bandwidth is secured without actually setting up the connection. It is desirable to provide a timer means for opening the timer.

In response to the connection setting request of the communication terminal, the originating exchange refers to the table without referring to the relay exchange and / or the destination exchange for the presence or absence of a predetermined band, and performs connection setting. It is desirable to have a means for performing this.

The inquiry means includes means for transmitting an inquiry cell, and the transit exchange and the destination exchange compare the value of the band written in this cell with the value of a band that can be secured by the cell. Means for updating the value of the band written in this cell by the value of the band that can be secured when the value of the band that can be secured is smaller than the value of the band that has already been written in this cell. It can also be.

It is preferable that the inquiry means include an inquiry means for each service class set according to the priority of cell transfer.

[0018]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of the present invention will be described with reference to FIGS. FIG. 1 is a diagram showing the overall configuration of an ATM communication network common to the first and second embodiments of the present invention.
FIG. 2 is a block diagram of a main part of an exchange on the calling side common to the first and second embodiments of the present invention. FIG. 3 is a block diagram of a main part of a transit exchange common to the first and second embodiments of the present invention. FIG. 4 is a block diagram of a main part of a receiving-side exchange common to the first and second embodiments of the present invention. Actually, there is no distinction between exchanges and transit exchanges, and they are all configured as nodes that have both configurations, and each time, it is possible to take any position of the originating exchange, the transit exchange, and the destination exchange. Be composed.

According to the present invention, as shown in FIG.
E, and an exchange LS on the outgoing side and the incoming side, which accommodates E, and a relay exchange TS provided on a transmission path connecting the exchanges LS on the outgoing side and the incoming side.
As shown in the figure, the CAC execution unit 10 receives the connection setting request of the communication terminal TE and searches for the presence or absence of the requested band.
Is an ATM communication network provided with.

Here, the feature of the present invention is that C
The AC execution unit 10 includes a periodic CAC request generation unit 2 that periodically searches for the presence / absence of a predetermined band regardless of the presence / absence of a connection setting request of the communication terminal TE. C
The AC execution unit 10 includes a route performance table 1 that records search results.

The periodic CAC request generation unit 2 inquires of the transit exchange TS whether a predetermined band exists or not, and
As shown in FIG. 3, the CAC calculation unit 3 receives the inquiry and responds to the exchange LS whether or not there is a predetermined band.
A virtual CAC band storage unit 4 for securing the band. In addition, as shown in FIG.
C for receiving an inquiry about the presence or absence of a predetermined band from the transit exchange TS and replying to the transit exchange TS about the presence or absence of the predetermined band C
It comprises an AC calculation unit 3 and a virtual CAC band storage unit 4 for securing the band.

Further, the virtual CAC band storage unit 4 includes a timer 5 for releasing the band secured after a predetermined time.

In response to the connection setting request from the communication terminal TE, the originating exchange LS refers to the route performance table 1 without reconfirming the presence or absence of the predetermined band of the relay exchange TS. 11 is provided.

In the second embodiment of the present invention, the periodic CAC request generator 2 of the originating exchange LS sends an inquiry cell, and the CAC calculator 3 of the transit exchange TS and the destination exchange LS Comparing the value of the band written in this cell with the value of the band that can be secured by itself, and if the value of the band that can be secured is smaller than the value of the band that has already been written in this cell, the self is secured The value of the band written in the cell is updated according to the value of the band that can be obtained.

In the first and second embodiments of the present invention,
The periodic CAC request generator 2 makes an inquiry for each service class set according to the priority of cell transfer.

[0026]

【Example】

(First Embodiment) A first embodiment of the present invention will be described with reference to FIGS. 1 to 4 are as described above. FIG. 5 is a sequence diagram showing the operation of the virtual CAC performed periodically according to the first embodiment of the present invention. In the VP set in the transmission path between the two exchanges LS on the calling side and the destination side that accommodate the communication terminal TE, a virtual CAC is periodically transmitted from the exchange LS.
Is performed. It is virtually considered that a setup of a QoS connection at 10 Mb / s is required, and the node on the VP calculates the CAC.

In the example shown in FIG. 5, 100 Mb / s, QoSH
Has been requested but has been rejected.
Requested Mb / s, QoSH and succeeded in virtual CAC. Therefore, route performance table 1
, QoSH and 10 Mb / s are recorded as route A. In other words, at this time, QoS 10
An empty band of Mb / s or more exists.

The originating exchange LS periodically transmits a virtual C
Periodic CAC request generator 2 for generating AC on the route
And a route performance table 1 for storing service classes (QoS), routes and bands that can be CAC as a result.

The relay exchange TS and the destination exchange LS
Is the CAC of the requested virtual connection in the CAC calculation unit 3.
A virtual CAC band storage unit 4 for performing C and storing a result of the virtual CAC and a timer 5 are provided. When the CAC is performed, the virtual CAC band is held even if there is no actual communication traffic. However, when a certain time elapses by the timer, the band is released. Further, as the CAC method, the flow rate at which traffic actually flows may be observed. In this case, there is no need to secure a band, so that there is no influence of the virtual CAC.

If there are a plurality of routes between the originating and terminating exchanges LS, the available CAC band is known for each route. Therefore, it is possible to perform communication using an optimal route.

(Second Embodiment) A second embodiment of the present invention will be described with reference to FIG. FIG. 6 is a sequence diagram showing the operation of the virtual CAC performed periodically according to the second embodiment of the present invention.
In the second embodiment of the present invention, a performance check cell is periodically transmitted to the route, and each node puts the performance check cell on the cell in a form overwriting the available capacity for each QoS. Overwriting means rewriting and transmitting the smaller of the band in the cell and its own free space. As a result, the minimum remaining bandwidth on the route is recorded in this cell. In FIG. 5, route A is finally
10Mb / s for QoS and 5M for QoSL
It can be seen that an empty band of b / s exists. In each of the relay exchanges TS and the destination exchange LS, a vacant band written in the performance check cell is secured by the timer 5 for a certain period of time.

(Summary of Embodiment) FIG. 7 is a diagram showing each service class and its available bandwidth. FIG. 8 is a sequence diagram showing an operation of receiving a connection setting request according to the present invention.
Assuming that QoS is the highest priority service class as shown in FIG. 7 and that the QoS class and the best effect are in order, the empty band that can be used by QoS and the empty band that can be used by QoSL are as shown in FIG. The actual user communication is already performed by the originating exchange L which accommodates the communication terminal TE.
Since S knows the available bandwidth of the QoS of the route, as shown in FIG. 8, the originating exchange LS does not need to inquire the relay exchange LS of the presence / absence of the required bandwidth, and can respond at high speed. . In this way, high speed CA
C can be performed, and an optimal route can be instantaneously selected from a plurality of routes.

[0033]

As described above, according to the present invention,
High-speed CAC can be performed, and connection setting appropriately corresponding to the state of the network at that time can be performed. Also, WAN
CAC even when a large-scale network such as
Time can be shortened. Further, even when a plurality of service classes coexist, the CAC time can be reduced. Further, when there are a plurality of routes, an optimal route can be selected.

[Brief description of the drawings]

FIG. 1 is a diagram showing an overall configuration of an ATM communication network common to first and second embodiments of the present invention.

FIG. 2 is a block diagram of a main part of an exchange on a calling side common to the first and second embodiments of the present invention.

FIG. 3 is a block diagram of a main part of a transit exchange common to the first and second embodiments of the present invention.

FIG. 4 is a block diagram of a main part of a destination-side exchange common to the first and second embodiments of the present invention;

FIG. 5 is a sequence diagram showing an operation of a virtual CAC performed periodically according to the first embodiment of the present invention.

FIG. 6 shows a virtual CA periodically performed according to the second embodiment of the present invention.
FIG. 4 is a sequence diagram showing the operation of C.

FIG. 7 is a diagram showing each service class and its available bandwidth.

FIG. 8 is a sequence diagram showing an operation of accepting a connection setting request according to the present invention.

FIG. 9 is a diagram showing a relationship among a communication terminal, an exchange, and a transit exchange.

FIG. 10 is a diagram showing various service classes.

FIG. 11 is a diagram for explaining the operation of a conventional CAC.

[Explanation of symbols]

 Reference Signs List 1 route performance table 2 periodic CAC request generation unit 3 CAC calculation unit 4 virtual CAC band storage unit 5 timer LS exchange TS relay exchange TE communication terminal

──────────────────────────────────────────────────続 き Continued on the front page (58) Field surveyed (Int.Cl. ⁷ , DB name) H04L 12/28

Claims (7)

(57) [Claims] 1. An exchange between a calling side and a called side accommodating a communication terminal.
Transmission line that connects the exchange and the exchanges on the originating and terminating sides.
And a relay exchange provided on the upper side, wherein the exchange on the calling side is provided.
Receives the connection setting request of the communication terminal,
ATM communication network equipped with means for searching for the presence or absence of the required bandwidth
The search means may include a connection setting of the communication terminal.
Search for the presence or absence of the specified band periodically regardless of the presence or absence of
MeansSee A predetermined band in the transit exchange and / or the destination exchange
Including means to secure An ATM communication network, characterized in that: 2. The ATM communication network according to claim 1, wherein said search means includes a table for recording a search result. 3. The means for searching for the presence / absence of a predetermined band includes means for inquiring the transit exchange and / or the destination exchange of presence / absence of a predetermined band, wherein the transit exchange and / or the destination exchange are And means for receiving the inquiry and responding to the originating exchange as to whether or not there is a predetermined band, and means for securing the band.
Or the ATM communication network according to 2. 4. The system according to claim 3, wherein said securing means comprises a timer means for releasing said bandwidth secured after a predetermined time.
An ATM communication network as described. 5. The exchange of the originating side refers to the table without re-inquiring the relay exchange and / or the exchange of the destination side for the presence or absence of a predetermined band in response to a connection setting request of the communication terminal. 4. The ATM communication network according to claim 3, further comprising a setting unit. 6. The inquiring means includes an inquiring cell transmitting means, wherein the transit exchange and the destination exchange have a value of a band written in the cell and a value of a band which can be secured by the cell. Means for updating the value of the band written in this cell by the value of the band that can be secured by itself when the value of the band that can be secured is smaller than the value of the band already written in this cell. The ATM communication network according to claim 3, further comprising: 7. The AT according to claim 3, wherein said inquiry means includes an inquiry means for each service class set according to a priority of cell transfer.
M communication network.