JPH0522333A - Connection control system in asynchronous transfer mode - Google Patents

Abstract

PURPOSE:To provide a traffic convergence function to a VPH even in the asynchronous transfer mode by applying call reception control to plural virtual path links and setting a virtual line based on the result. CONSTITUTION:Upon the receipt of connection information, when subscriber VCH41, 42 connects a call to a VPC (VP connection) 61, the reception control as to whether or not the quality of the call is satisfied based on the capacity of a VPL (VP link) 613 and the operating state is implemented and discriminated. The reception control constitutes a virtual path connection in the asynchronous transmission mode and is applied to a virtual path link in which each assigned capacity is not matched respectively. When control is discriminated to be satisfied, the virtual line is set by the connection function of a connection management equipment 48 in the virtual path connection. Furthermore, the management equipment 48 has a function to manage the operating state of the VPL 613 and a traffic convergence function is provided to a VPH implementing the connection of the VPL 613 and a signal repeater 47 is operated.

Description

Detailed Description of the Invention

[0001]

The present invention relates to an asynchronous transfer mode (A
The present invention relates to a connection control method that constitutes a communication network based on TM.

[0002]

2. Description of the Related Art FIG. 15 is a block diagram showing a conventional network construction method for constructing a communication network by connecting a plurality of exchanges with a line bundle.

In a relatively small-scale network, as shown in FIG. 15 (a), each terminal 1 is accommodated in a subscriber exchange 2, and each subscriber exchange 2 is a path (a bundle of lines, for example, a bundle of 24 lines). A reticulated net connected through 3 is applied. In this network configuration, the path 3 set between the respective subscriber exchanges 2 is used only for carrying the traffic between the two subscriber exchanges 2, so that the use efficiency of the path (line in the path) is low. . Furthermore, as the number of subscriber exchanges 2 increases, the number of paths 3 increases rapidly, complicating network operation and management.

On the other hand, when the number of subscriber exchanges 2 exceeds a predetermined number, a star network via the transit exchange 4 is applied as shown in FIG. 15 (b). Although the transit exchange 4 is required in the star network, since the traffic is converged by the transit exchange 4, the use efficiency of the path 3 between the transit exchanges 4 can be increased, and especially the distance between the transit exchanges 4 is long. In some cases, the network will be economical. In addition, the number of paths to be managed is reduced, which is an advantageous network configuration method in terms of network operation and management.

By the way, the lines constituting a communication channel are usually multiplexed on a physical transmission line (transmission line medium), but in digital transmission, a time division multiplexing system is generally used. The time division multiplexing method includes a method of multiplexing by identifying a position on the time axis and a method of multiplexing by identifying a label. The method of multiplexing by identifying the position on the time axis is time position multiplexing or STM (Synchronou
s Transfer Mode), which assigns a channel to a time position (time slot) in a frame and replaces the time slot to realize an exchange service.

On the other hand, as a label multiplex system, there is a packet multiplex system in which a length of an information field is variable, but recently, an ATM (Asynchronous Transfer Mode, which multiplexes using fixed length packets (cells) is used. Asynchronous transfer mode) has been proposed. In ATM, information is sent out only when information transfer is requested, so intermittent or continuous communication is possible according to the frequency, and it is possible to flexibly cope with any transfer rate from low speed to high speed. Furthermore, since empty cells are inserted when there is no information, cells appear at fixed timings, and the process of identifying the cell head and the exchange process can be performed at high speed by hardware. It is a promising system as a transfer mode for wideband ISDN.

FIG. 16 is a diagram showing an ATM cell structure. In the figure, the cell 11 has a 5-byte header 12 and
It is composed of a 48-byte information field 13. The header 12 further includes a virtual path identification (hereinafter “VPI (virtual path identifier)”) field 14 and a virtual circuit identification (hereinafter “VCI (virtual channel identifier)” field 1
5 and an error correction code and other control information field 16. The VPI field 14 is 12 bits for the intra-network interface and 8 bits for the user-network interface, and the VCI field 15 is 16 bits.
These bits are control information necessary for multiplexing, cell switching, traffic control, etc. This VPI and VCI
Corresponds to the label described above, and the cell can be identified by VPI and VCI.

The node normally analyzes the header 12 by hardware and performs multiplexing, cell switching, and traffic control at high speed. Even in ATM, 1 on the multiplexed transmission line
One specific channel is identified by VPI and VCI, and the node analyzes the VPI and VCI of the cell for each cell to determine the destination route, replaces the new VPI and VCI, and sends the cell to the destination transmission line. Exchange services have been realized. The VPI and VCI are unique within one node.

Here, a channel (cell) identified by VPI + VCI is connected to a virtual circuit (hereinafter, "VC (virtual
Channel) ”), and a channel (cell) identified only by VPI without reference to VCI is a virtual path (hereinafter,“ V ”).
P (virtual path) "). That is, STM
In correspondence with, as shown in FIG.
VP22 is one line, and VP22 is a path that bundles the lines (for example,
It is 24 lines of 1.5 Mbps and is multiplexed on the transmission line (transmission medium) 23. The transmission line 23 may be a physical 100 Mbps transmission line medium or 600 Mbps which is a part of the 2.4 Gbps transmission system.

The nodes in the ATM network have two types of switching (switching) functions, similar to the STM. That is,
In the STM network, there are an exchange that exchanges on a line-by-line basis and a path switching device (cross connector, omitted in FIG. 15) that exchanges (switches) on a path-by-path basis. In the ATM network, VPI + VCI is identified as the equivalent. VC handler for exchanging by VC unit (hereinafter, “VCH”)
Then, only VPI is identified and exchanged (switched) for each VP.
There is a VP handler (hereinafter, “VPH”) that does this.

In the STM switch, lines are switched and connected in the same manner as calls are originated and disappeared, and the VCH is also switched and connected in VC as calls are originated and disappeared. On the other hand, STM
The path switching device does not switch for each call, and the connection state does not change unless the connection pattern is changed even in VPH so that the connection state continues as long as the connection pattern is not changed. That is, the connection state of the VCH changes according to the origination and disappearance of a call, but in the VPH, the connection is made according to the pattern determined by the network design and the like, and in the normal operation method, the connection change occurs only on the order of time. . Also, like the STM, the VCH is provided with a service control function, a charging function, and other high-performance functions.
Is not provided with these functions.

As described above, since the VPH does not perform switching connection for each call, the function is simpler than that of the VCH, and as a result, the cost of the device is lower than that of the VCH. on the other hand,
Although the device cost is high because the VCH is switched and connected for each call, the VP and VC can be used efficiently because of the function of converging traffic.

Now, also in ATM, generally, as shown in FIG.
There are two network construction methods shown in FIG. However, the subscriber exchange 2 is the subscriber VCH 32, the path 3 is the VP 33, and the relay exchange 4 is the relay VCH 34.

[0014]

In the mesh network configuration shown in FIG. 15 (a), since the VP 33 is set between the subscriber VCHs 32, the use efficiency of the VP and VC is low. On the other hand, in the configuration of the star network shown in FIG. 15 (b), the traffic is converged by the relay VCH 34 and the VC (VP) can be used efficiently, but for that purpose, connection control is performed for each call. It is necessary to install an expensive relay VCH. That is, while there is a gain in that the VP and VC can be used efficiently, there is also a loss associated with the installation of an expensive relay VCH, which is a profit or loss, or an economic effect cannot be obtained.

An object of the present invention is to provide a connection control system in an asynchronous transfer mode (ATM) which can construct an economical ATM network.

[0016]

According to a first aspect of the present invention, call admission control is performed for each of a plurality of virtual path links that constitute a virtual path connection in the asynchronous transfer mode and do not necessarily have the same allocated capacity. And a virtual circuit is set in the virtual path connection based on the result.

According to a second aspect of the present invention, in the connection control method in the asynchronous transfer mode according to the first aspect, a transmission line accommodating a plurality of first virtual path links forming a first virtual path connection is provided. It is characterized in that at least one transmission line allocates a common capacity to the first virtual path link and the second virtual path link which constitutes another virtual path connection.

According to the invention described in claim 3, in the connection control method in the asynchronous transfer mode according to claim 2, the call admission control for each virtual path link to which a common capacity is allocated is fixed to each virtual path link. It is characterized in that it is performed on the basis of the minimum capacity of the capacity which has been allocated.

According to a fourth aspect of the invention, in the connection control method in the asynchronous transfer mode according to any one of the first to third aspects, a virtual path except a virtual path link accommodated at least at a virtual path termination point. A connection management device having a function of performing call admission control for a link is provided, and the connection management device manages a virtual circuit setting request within a virtual path connection set between the virtual path termination points. A feature is that call admission control is performed for the virtual path link.

According to a fifth aspect of the present invention, in the connection control method in the asynchronous transfer mode according to any one of the first to third aspects, a virtual path except at least a virtual path link accommodated at a virtual path termination point. A function of performing call admission control for a link is provided in a specific virtual circuit handler, and the virtual circuit handler manages a request for setting a virtual circuit in a virtual path connection set between the virtual path termination points. The call admission control is performed for the virtual path link to be executed.

According to a sixth aspect of the present invention, in the connection control method in the asynchronous transfer mode according to any one of the first to fifth aspects, based on abnormality information from a virtual path handler connecting virtual path links, It is characterized in that the capacity of the virtual path link accommodated in this virtual path handler is changed and call admission control is performed using this capacity.

According to a seventh aspect of the present invention, in the connection control method in the asynchronous transfer mode according to any of the first to sixth aspects, the capacity of the virtual path link is changed based on a time schedule, and the capacity is changed. The feature is that call admission control is performed by using this.

The invention according to claim 8 is the connection control method in the asynchronous transfer mode according to claim 4, wherein when a failure occurs in the connection management device, a predetermined virtual path connection capacity is used to call at the virtual path termination point. It is characterized by performing admission control.

According to a ninth aspect of the present invention, in the connection control method in the asynchronous transfer mode according to any one of the first to ninth aspects, a direct virtual path connection and one or more virtual path links are provided between two nodes. When setting up a detour virtual path connection consisting of, and setting up a virtual circuit between the nodes, first, call admission control is performed on the direct virtual path connection to try to set up the virtual circuit, and the call admission control is performed. Is satisfied, a virtual circuit is set to the direct virtual path connection, and if the call admission control is not satisfied, the detour virtual path connection is selected.

According to a tenth aspect of the present invention, a transmission line accommodating each virtual path link in response to a virtual path connection capacity change request made from a termination point of the virtual path connection configured by a plurality of virtual path links. The call admission control is performed, and the capacity of the virtual path connection is allocated based on the result.

The invention according to claim 11 is that a first virtual path connection composed of a plurality of first virtual path links and a second virtual path composed of one or more second virtual path links. Connection, the two path termination points of the first virtual path connection are a first node and a second node, and the two path termination points of the second virtual path connection are a third node. Node and second
Of the first virtual path link and the second virtual path link
In the asynchronous transfer mode network in which at least one virtual path link that accommodates the virtual path link and the virtual path link of
Call admission control is performed for the virtual path link in the section immediately before the same transmission path that first appears from the node, and the virtual path link in the section from the same transmission path to the second system in the second node. Call admission control is performed on the basis of the result, and a virtual circuit is set in the first virtual path connection based on the result of the call admission control.
Call admission control is performed for the virtual path link in the section immediately before the same transmission path that first appears from the node, and the virtual path link in the section from the same transmission path to the second system in the second node. Call admission control is performed, and a virtual circuit is set in the second virtual path connection based on the result.

[0027]

Although the virtual path (VP) is a general term for a bundle of virtual circuits (VC), the term related to the VP will be described with reference to FIG. 2 for the purpose of explaining the present invention. In FIG. 2, VPHs 83, 84, 85 are arranged between terminal points 81, 82 of a VP connection (hereinafter, “VPC”) 90, and VP links (hereinafter, “VPL”) 86, 87, 8 are arranged.
They are connected to each other via 8, 89. In addition, "x" in each VPH indicates the connection of the VPL. In addition,
The termination points 81 and 82 of the VPC 90 are VCHs, for example.

With VPC 90, each VPL 86-89 is V
It is connected by PH83 to 85 and provides a bundle of channels for carrying cells between the termination points 81 and 82, that is, VP. A permitted usable capacity (bandwidth, for example, 52 Mbps) is allocated to the VPLs 86 to 89. In general, the capacities of the VPLs that make up one VPC are the same, so the capacity of that VPC is equal to the capacities that make up those VPLs.

According to the present invention, the capacity assigned to each VPL is different, or the capacity assigned to a VPL is shared with another VPL in the same transmission path in order to use the VPL and the transmission path efficiently. Is especially assumed.

A VP configured by a plurality of VPLs by allocating a common capacity to a plurality of VPLs accommodated in the same transmission path.
Regarding C, call admission control is performed in each VPL when a VC is set in the VPC, and the VC is set in the VPC based on the result. Note that the call admission control determines whether or not the cell quality (cell loss rate, delay) of the new call and the already-accepted call can satisfy the specified value even if a new call is accepted at the call connection request, This is a control for determining whether or not to accept the call. By performing such call admission control for each VPL,
H can be functionally equivalent to the relay VCH, and the traffic can be converged without using the expensive relay VCH. In other words, the effect of a large amount of traffic can be absorbed, fluctuations in the traffic for a short time and a long time can be absorbed, and the use efficiency of the VPL (VPC) and VC is improved, so that an economical ATM network can be constructed.

When allocating capacities of VPCs composed of a plurality of VPLs by similar means, call admission control is performed on the transmission lines accommodating these VPLs, and capacities are allocated based on the results. To do so. Therefore, the capacity of the VPC can be easily changed, and the use efficiency of the VPC and the transmission path accommodating the VPC is improved, so that an economical ATM network can be constructed.

[0032]

DESCRIPTION OF THE PREFERRED EMBODIMENTS [Explanation of the First Embodiment of the Present Invention] FIG. 1 is a block diagram showing the ATM network configuration of the first embodiment of the present invention.

In the figure, terminal 1 and subscriber VCHs 41-41
44, VPHs 45 and 46 replacing the relay VCH are shown in FIG.
It is similar to the configuration of the star network shown in (b). Subscriber VCH4
1, 42 and the VPH 45 between the transmission lines 71,
72 is arranged, a transmission line 73 is arranged between the VPHs 45 and 46, and transmission lines 74 and 75 are arranged between the VPH 46 and the subscriber VCHs 43 and 44, respectively. Subscriber V
The VPC 61 is set between the CH 41 and the subscriber VCH 43, the VPC 62 is set between the subscriber VCH 41 and the subscriber VCH 44, and the subscriber VCH 42 and the subscriber V
VPC63 is set between CH43 and subscriber VC
A VPC 64 is set between the H 42 and the subscriber VCH 44, a VPC 65 is set between the subscriber VCH 41 and the subscriber VCH 42, and a subscriber VCH 43 and a subscriber VC are set.
A VPC 66 is set between it and H44. Also, VP
C61 is composed of VPLs 61 _{1 to} 61 ₃ , and VPCs 62, 63, 64, 65, 66 are VPLs similarly.
62 _{1 to} 62 ₃ , 63 _{1 to} 63 ₃ , 64 ₁ to 64 ₃ , 6
5 _{1 to} 65 ₂ and 66 _{1 to} 66 ₂ . Further, between the subscriber VCHs 41 to 44 and VPHs 45 and 46 and the connection management device 48, a signal repeater 47 for connecting the common line signaling control lines 51 to 57 is arranged.

[Description of Function of VPH] Here, the functional principle of the VPH 45 (46) will be described with reference to FIG.
In FIG. 3, VPH 45 is a cell switch 101,
It is composed of VPI conversion tables 102 and 103 and control lines 119 and 120 connecting them. The field 104 of the VPI conversion tables 102 and 103 contains the entered V
The PI field is stored, the field 105 is a field that stores an outgoing transmission path number, and the field 106 is a field that stores an outgoing VPI. The VPI conversion table 102 corresponds to the transmission path 71,
The VPI conversion table 103 corresponds to the transmission path 72. Reference numerals 111 to 118 are cells.

When the cell 112 arrives from the transmission line 71,
VPI # 5 in the cell header is read and control line 119
VPI conversion table 10 corresponding to the transmission path 71 via
VPI in field 104 of No. 2 is searched and #
Access address 5. The VPI and the address may be simply associated with each other. The output transmission path number # 3 and the output VPI # 7 are stored in the field of this address, and these are read out and returned to the cell switch 101 via the control line 119. The cell switch 101 is the cell 11
The cell 118 obtained by converting the VPI # 5 of No. 2 into # 7 is sent to the transmission path 73 of the transmission path number # 3. I will omit it here,
In ATM, valid cells arrive asynchronously except for empty cells. Therefore, more accurately, they are sent to the transmission path 73 after passing through the output buffer corresponding to the transmission path. When a cell overflows from the output buffer, the cell is discarded and cell loss occurs. Through such processing, the VPL identified by VPI # 5 on the transmission line 71 and the VPL on the transmission line 73 are identified.
The VPL identified by PI # 7 is connected to form a part of the VPC.

Similarly, the VPL identified by VPI # 8 on the transmission line 71 and the VPL identified by VPI # 3, # 9 on the transmission line 72 are both new VPLs on the transmission line 73.
(VPI of each output is # 4, # 6, # 1)
One VPC will be multiplexed on the transmission path 73. That is, in FIG. 1, VPLs 61 ₁ , 62 ₁ , 63 ₁ ,
64 ₁ VPI # 5, # 8, # 3, # 9, VPL6
1 ₂ , 62 ₂ , 63 ₂ , 64 ₂ VPI # 7, # 4, #
6 and # 1, VPL61 ₁ and VPL6
1 ₂ , VPL62 ₁ and VPL62 ₂ , VPL63 ₁ and V
PL63 ₂ , VPL64 ₁ and VPL64 ₂ are VPH4
5 is connected, and VPC 61, 62, 63,
This means that 64 are multiplexed on the same transmission line 73. Similarly, VPLs are connected one after another at the VPH 46 at the next stage,
Configure each VPC.

It should be noted that in FIG. 3, one input VPL is used.
It is also possible to make a one-to-n connection connecting V.sub.s to multiple outgoing VPLs. In the case of 1-to-n connection, for example, the outgoing transmission line and V
A plurality of fields similar to the fields 105 and 106 for storing the PI are provided at the same address, the transmission line number and the VPI to be branched are stored in the field of the set, and the cell switch duplicates the incoming cell. By adding the specified VPI to the specified transmission path and transmitting the duplicated cell, a 1-to-n connection becomes possible.

In addition, a plurality of incoming VPLs can be output to one outgoing VP.
An n: 1 connection to L is also possible. In this case, the same transmission line number may be set in the fields 105 and 106 corresponding to the incoming VPI. For example, in the state of the VPI conversion table 102, VPI # on the transmission path 71 is set.
The VPL identified by 5 and VPI # 7 can be connected to VPI # 7 on the transmission path 73 (transmission path # 3) in a 2: 1 relationship. In the case of n: 1 connection, if the same VCI exists in the input VPL that is the target of n: 1 connection,
Since it becomes impossible to identify the VC at the termination point of the VPC (VPI has the same number in the VPH that is connected to n to 1 and the VCI is also the same), normally, the VCI overlap between the incoming VPLs that should be concentrated. Are often banned. As described above, the VPHs 45 and 46 can be connected to 1 to n and n to 1 in addition to the 1 to 1 connection.

[Description of Call Connection Operation] Next, the call connection operation of the present embodiment will be described with reference to FIG. Here, the terminal 1 accommodated in the subscriber VCH 41 is the subscriber VC
A case where a call is made to the terminal 1 accommodated in H43 will be described.

By the operation similar to that of the STM subscriber switch, the subscriber VCH 41 detects the call from the terminal 1, determines the incoming subscriber VCH 43 from the destination number, and determines the VPC 61 (VPL 61 ₁ ) which is the outgoing route. Determined and its VPC61
Capture the VC in (VPL61 ₁ ). In STM, it will capture the vacant line in the line bundle,
In ATM, a VC of the VCI address space (2 16) is logically set to one VPL and VPC. However, if it is left as it is, the total transfer information amount of the call is VP.
The following control is required because the quality (cell loss rate, delay) is extremely deteriorated by exceeding the capacity of C and VPL.

That is, it is judged whether or not the quality of the already connected call is guaranteed by connecting the call, and it is judged whether or not the call (specifically, setting of VC) is accepted. If it can be accepted, the VC can be captured. This operation is called "call admission control", and various algorithms have been proposed.

For example, the characteristics of an already connected call,
Specifically, it is determined from the transmission characteristics of the cell (peak speed, average speed, etc.) and the declared traffic characteristics of the newly connected call.
A method of defining the maximum number of calls that can be connected to (VPL) may be used. The subscriber VCH 41 determines whether or not the call can be accepted by the VPC 61 based on the traffic status of the VPL 61 ₁ and the declared traffic characteristics of the call. If the call cannot be accepted, the call loss processing is performed. The VCI of this call is determined by selecting from the empty VCIs of the VPC 61. Since VCI is unique in VPC, VPC6
There is no problem even if it overlaps with VCI on 2. At this time, the subscriber VCH 41 performs call admission control based on the capacity and usage of the VPL 61 ₁ , and determines whether or not the call can be admitted.

Next, the subscriber VCH 41 is connected to the control line 51,
The connection management device 4 is connected via the signal repeater 47 and the control line 55.
8 transfers the connection information of the call. Connection management device 48
Has a function of managing the connection status of the VPLs 61 ₂ , 62 ₂ , 63 ₂ , 64 ₂ . Therefore, when the connection management device 48 receives the connection information, the VPC 61 (V
Even if the call is connected to PL61 ₂ ), the call admission control is performed to determine whether or not the quality of the already connected call can be satisfied, and VPL6
Judgment is based on the capacity and usage of 1 ₂ .
It is notified to the subscriber VCH 41 via the control line 55, the signal repeater 47, and the control line 51 whether or not the reception is possible. The subscriber VCH 41 receives this result, and if it is not possible, the call is lost. If possible, the connection information of this call is transferred to the subscriber VCH 43 via the control line 51, the signal repeater 47, and the control line 53. This connection information includes the subscriber VC
It includes the VCI of the call determined by H41, the called number, the declared traffic characteristics of the call, and so on.

Upon receiving this connection information, the subscriber VCH 43 performs call admission control on whether or not the quality of the already connected call can be satisfied even if it is connected to the VPC 61 (VPL 61 ₃ ) of the call, and the VPL 61 ₃ Judge based on capacity, usage, etc. When it is satisfied, the called terminal is identified by the called number to connect to the terminal 1. When the terminal 1 responds, the control line 5 is sent to the calling subscriber VCH 41.
3, a response signal is transmitted via the signal repeater 47 and the control line 51. On the other hand, when the call admission control is not satisfied, the fact that the connection cannot be established is similarly transmitted to the subscriber VCH 41.
The subsequent operation is similar to that of the conventional STM switching network, and therefore the description thereof is omitted. However, when the call ends, the end of the call is terminated via the control line 53, the signal relay 47, and the control line 55. The connection management device 48 updates the connection status of the VPL 61 ₂ managed internally (for example, subtracts 1 from the number of connected calls).

From the above point of view of call admission control,
The subscriber VCH 41 performs call admission control for the VPL 61 ₁ , the connection management device 48 performs call admission control for the VPL 61 ₂ , and the subscriber VCH 43 performs call admission control for the VPL 61 ₃ . It should be noted that with respect to the usable capacity of the VPL 61 ₁ at that time (the difference between the allocated capacity and the capacity required for the already connected call), the VPL 61 ₂ ,
If it is guaranteed that the available capacity of 61 ₃ at that time is the same or large, all can be represented by the call admission control in the subscriber VCH 43.

Here, what is important is that V as described above is used.
PC61 is constituted by connecting three _{VPL61 1, 61 2, 61 3} , and VPL61 _1, 61 _2, 61 ₃
Are different in capacity and their usage is different. According to the conventional usage method, a dedicated capacity is assigned to each VPL that constitutes the VPC as described above, and the usage status and capacity are the same. Therefore, generally, call admission control in the subscriber VCH 41 is performed. Represented by.
However, in the method of the present invention, in order to improve the use efficiency of the VPL and the transmission path, it is considered that the capacity is commonly assigned to a plurality of VPLs in the same transmission path, and the capacity (assignment In this case, the call admission control of each VPL basically needs to be performed at the above-mentioned three places because the situation in which the allocated capacity and the usable capacity at that time are different.

In the above description, VPL 61 ₁ , 6
The call admission control for 1 ₃ is performed by each subscriber VCH 41,
Although this is executed in step 43, the connection management device 48 may perform this in a unified manner. In this case, the subscriber VCH4
1 determines the VCI and then outputs the connection information to the connection management device 48.
To the VPL 61 ₁ , 61 ₂ ,
All call admission control of 61 ₃ will be performed.

Furthermore, the VCI is also managed by the connection management device 48.
It is also possible for the connection management device 48 to determine the VCI. In this case, the subscriber VCH41
When the call is detected, the connection information is transferred to the connection management device 48, and the connection management device 48 causes the VPLs 61 ₁ , 61 ₂ , 61 _3.
Call admission control is performed, and when the call admission is possible in all VPLs, the captured VCI is notified to the subscriber VCH 41.
If the call cannot be accepted, a call loss instruction is given to the subscriber V.
Notify CH41.

In the above description, the subscriber VCH 41
After the VC is captured in step S1, the connection management device 48 is inquired as to whether or not connection is possible, and the subscriber VCH41 receives the result and sends the connection information to the subscriber VCH43 again, but the subscriber VCH41 captures the VC. After that, the connection information sent to the connection management device 48 and the connection information sent to the subscriber VCH 43 may be sent together to the connection management device 48. To this end, if the connection management device 48 determines that the call admission control is not permitted, the call loss instruction is returned to the subscriber VCH 41 as described above, and if possible, the connection information is transferred to the subscriber VCH 43. To configure. In this case, the processing of the connection management device 48 becomes slightly complicated, but the connection time can be shortened. The present invention can be implemented in any of the above embodiments and is not limited to one form thereof.

[Description of Call Admission Control in Connection Management Device 48] Next, call admission control in the connection management device 48 will be described. Upon receiving the connection information from the subscriber VCH 41, the connection management device 48 executes the call admission control for this call. As described above, the call admission control includes call traffic characteristics (peak speed of cell transmission, average speed, etc.), traffic characteristics of already connected calls, and their statistical multiple effects (Kawaharazaki et al., "ATM communication technology"). Trend-Toward High-speed Broadband Systems- ", The Institute of Electronics, Information and Communication Engineers, 71, 8, p.
p.809-814 (sho 63-08)) is also comprehensively judged to judge whether the call can be accepted or not. Here, in order to simplify the explanation, the number of connected calls is less than or equal to the control parameter value. It depends on the method of determining whether or not. In this example, VPL6
1 ₂ , 62 ₂ , 63 ₂ , 64 ₂ control parameters N
_i (i is 1 to 4).

FIG. 4 is a flow chart for explaining the procedure of call admission control of the connection management device 48. In FIG. 4 (a), when receiving the connection information (S1), the control parameter N _i corresponding to VPL, it is accommodated in the same transmission path VP
It is compared with M _i = f (n _i ) determined by the function of the number of calls n _i connected to L (S2). Here, when M _i ≧ N _i ,
When it is determined that the call is not acceptable, the call loss instruction is returned to the subscriber VCH 41 (S3). In other cases, it is determined that the call is acceptable and the subscriber VCH 41 is returned that the call is acceptable, and n 1 is added to _i (S4). As shown in FIG. 4 (b), when the call end is reported (S5), _ni
Is decremented by 1 (S6). As described above, in order to be call loss in the case of can not be accepted, the control parameter N _i is loss probability constant value (e.g., 0.01) below, and the loss rate and the delay constant value of the cell (e.g., 1 / 10 ⁹ 1ms) or less. In addition, the VPL allocation capacity (including the case of being shared with other VPLs) and the capacity of the transmission path 73 corresponding thereto are designed.

There are various methods for defining M _i and N _i , and the present invention does not limit the method. Assuming that the maximum number of connected calls that the entire capacity of the transmission path 73 has is N, for example, ΣN _i = N and M _i = n _i can be simply set. When this is made to correspond to the STM, there are four paths with the number of lines N _{i in} the transmission line 73 (the total number of lines of the paths is equal to the maximum number of lines accommodated in the transmission line), and the subscriber VCHs 41, 42,
This is equivalent to capturing the line from each path for the four types of calls of the combination of arrival and departure of the subscriber VCHs 43 and 44. In this case, it can be easily inferred from the STM case that the VPL cannot be used efficiently.

On the other hand, when ΣN _i > N, a plurality of VPs
This means that a capacity is commonly assigned to L, and that capacity (resource) is partially shared by a plurality of call types,
Due to the large clustering effect of the traffic theory, VPL (strictly assigned capacity) can be used efficiently.
The most extreme example is when N _i = N and M _i = Σn _i , and the capacity of the transmission path can be shared by all VPLs.
The VPL can be used most efficiently. Setting N _i = N corresponds to assuming that the transmission path 73 is one path in correspondence with the STM and selecting a line in the path as a group. However, when resources are shared, there is a problem that competition between calls occurs, and when the traffic of a specific call type increases, other call types are squeezed. For example, subscriber VCH41
From the subscriber to the subscriber VCH 43, the transmission line 73
Then the number of connections for VPL61 ₂ increased, and the subscriber VCH
It becomes difficult to connect the call from 42 to the subscriber VCH 43.
For this purpose, the degree of sharing is considered as appropriate according to the service quality. To alleviate this competition, STM line reservation or other means can be applied.

In the above description, M _i and N _i are fixed in time, but they can be dynamically changed according to the time zone of day and night, the day of the week, and the season. The change of M _i and N _i may be performed in the connection management device 48 automatically or according to a predetermined manual. Further, when a part of the transmission line 73 becomes a failure and the capacity of the transmission line 73 decreases, failure information is reported from the VPH 45, 46 via the control lines 56, 57. _i
It is also possible to change N _i and N _i . Also, VPH
The cell loss of the VPL in the VPL 61 ₂ , 62 ₂ etc. is monitored at 45 and 46, and when the cell loss rate exceeds a specified value due to cell congestion, the abnormality is notified via the control lines 56 and 57. It is also possible to change M _i and N _i depending on the information. The call admission control in the connection management device 48 can also be applied to the call admission connection in the subscriber VCH 41. That is, VPL 61 ₁ , 62 ₁ , 6
If the control parameter of 5 ₁ is N _i (i is 1 to 3),
The call admission control is the same as the flowchart shown in FIG.
Further, when the maximum number of connected calls that the capacity of the transmission path 71 has is N, it is possible to set ΣN _i = N or ΣN _i > N. In particular, when N _i = N and M _i = Σn _i ,
The capacity of the transmission line 71 is shared by the VPLs 61 ₁ , 62 ₁ and 65 ₁ , and the subscriber VCH 41 to the subscriber VCHs 42, 4 are shared.
A group of calls is selected for the calls to 3, 44, and the same function as that of the relay VCH 34 of FIG. Note that this call admission control can also be performed by the connection management device 48 as described above.

[Explanation in the case where VPC is composed of a larger number of VPLs] In the above description, an example in which there is one VPL in the VPH section in the VPC (for example, VPC 61 has V
Although there is one VPL 61 ₂ between the PH 45 and the VPH 46), the present invention can be applied even when there are VPLs between a plurality of VPHs in the VPC.

FIG. 5 is a block diagram showing an ATM network structure in the case where the VPC is composed of a larger number of VPLs.
In the figure, reference numerals 161 to 163 denote VPH, and reference numeral 164.
˜166 are VPCs, 171 to 177 are transmission lines, 191 to 195 are subscriber VCHs, and 201 to 205 are control lines. Also, the subscriber VCH 191 and the subscriber VC
VPC164 set between H194 and V194 is VPL1
Composed of 64 _{1-164 4.}

Here, VPLs 164 ₂ and 164 ₃ are other VPLs in the same transmission line in which they are accommodated, for example, VPs.
It shares the capacity with the VPL that constitutes C165 and 166. Therefore, from the subscriber VCH 191 to the subscriber VCH
For a call to 194, it is necessary to perform call admission control regarding VPLs 164 _{1 to} 164 ₄ . VPL164 ₁ ,
Although the subscriber VCHs 191 and 194 can also perform call admission control for 164 ₄ , VPLs 164 ₂ and 1
For 64 ₃ , the connection management device 48 needs to perform call admission control. This is because the VPLs 164 ₂ and 164 ₃ are provided with other Vs accommodated in the transmission lines 173 and 175 for call admission control.
Subscriber VCH 191, although PL usage information is required
This is because the use information cannot be grasped in 194. Therefore, the subscriber VCHs 191 and 194 have VPL164.
The call admission control of ₂ 164 ₃ cannot be performed, and other V
The call admission control is performed by the connection management device 48 that is aware of the PL usage information. In this way, even if the VPC is composed of a larger number of VPLs, no restrictions are imposed on the application of the present invention.

[Explanation when there are a plurality of connection management devices] A plurality of connection management devices are installed, and a certain connection management device is in charge of call admission control of VPLs accommodated in VPHs within a certain area.
Another connection management device may be configured to administer call admission control of a VPL accommodated in a VPH in another area.

FIG. 6 is a block diagram showing an ATM network configuration when a plurality of connection management apparatuses are installed. In the figure, reference numerals 221 and 222 are connection management apparatuses, and reference numeral 223.
228 is a subscriber VCH, reference numerals 224 to 227 are VPHs,
Reference numerals 241 to 245 are VPLs constituting the VPC between the subscriber VCHs, reference numerals 251 to 254 are control lines, and reference numerals 501 to 501.
505 is a transmission line. Here, it is assumed that the connection management device 221 controls the VPLs 242 to 243, the connection management device 222 controls the VPL 244, and each VPL performs call admission control.

When a call occurs between the subscriber VCHs 223 and 228, the subscriber VCH 223 performs call admission control of the VPL 241 and controls the control line 251, the signal relay 47, and the control line 25.
The control information is transmitted to the connection management device 221 via the No. 3.
When the connection management device 221 performs the call admission control for the VPLs 242 and 243, the control line 253, the signal relay 47,
The control information is transferred to the connection management device 222 via the control line 254. When the connection management device 222 performs the call admission control for the VPL 244, the control line 254, the signal relay 4
7. Control information is sent to the subscriber VCH 22 via the control line 251.
Transfer to 3. In this case, the connection management device 221 is V
It has information about which connection management device manages the VPL 244 and the subsequent connected to the PL 243. Further, the present invention can be implemented in the same manner even if the connection management devices are arranged in a one-to-one correspondence with each VPH. Note that, basically, since the VPH and the connection management device do not have a direct interface, there is no logical relationship between the VPH and the connection management device.

In the above description, each connection management device 221,
Although 222 has been described as an independent device, its location is not limited as long as its function is realized. That is, even if the connection management function exists independently in the network, another device,
For example, it may be shared by a personal database, a toll-free service, or another network database. It is also possible to merge that function into a particular VCH. An example in which the function is merged into a specific subscriber VCH will be described later.

[Explanation on Failure of Connection Management Device] Since the connection management device is required to have high reliability, a redundant configuration is usually adopted, but measures against failure of the connection management device are also important. . For example, in FIG.
Etc., the capacity allocated to the connection management device 48 at the time of failure is determined in advance, the subscriber VCH 41 performs call admission control based on the allocated capacity, and transfers the connection information directly to the call destination subscriber VCH 43. To configure. Therefore, if the connection management device 48 fails,
Since the traffic cannot be converged by VPH45 and VPH46, the form shown in Fig. 15 (a) is obtained, but the function as an ATM network is maintained and a so-called fail-soft system (network) is used.
Can be configured.

[Explanation of Second Embodiment of the Present Invention] FIG. 7 is a block diagram showing an ATM network configuration of a second embodiment of the present invention. In the figure, reference numerals 261 to 264 are subscriber VCHs,
Reference numerals 271 to 274 are VPH. Reference numerals 281 to 28
A direct VPC 6 corresponds to a direct path (line) in the STM. Reference numerals 291 to 296 are detour VPCs, and S
In TM, it corresponds to a detour path (line). Reference numerals 301 to 3
Reference numeral 07 is a transmission line, and reference numerals 311 to 314 are control lines. The signal repeater 47 and the connection management device 48 are the same.

Direct VPCs 281 to 286 and detour VPCs 291 to between the subscriber VCHs 261 to 264 are mutually connected.
296 is set in a mesh shape. Direct VPC281 ~
Although 286 is also composed of a plurality of VPLs, the description of VPHs and transmission lines existing between VPLs is omitted. In addition, direct V
There is no problem even if the PC routes the same transmission line and the same VPH as the detour VPC. For example, the direct VPC 281 is in parallel with the detour VPC 292 and the same transmission lines 304 and 30.
1, 302, 306 and VPH 271, 272, 273 may be used.

The subscriber VCHs 261 to 264 are direct VPs.
When the capacities of the VPLs forming the Cs 281 to 286 are equal, the value is taken as the capacity of the VPL, and the direct VPC 281
When the capacities of the VPLs forming the ˜286 are different, those minimum values are managed as the capacities of the direct VPLs. Therefore, the subscriber VCHs 261 to 264 are directly connected to the VPC2.
81-286 when setting a VC to the subscriber VCH
The call admission control may be performed only on the basis of the capacity of the direct VPC managed by the VPC and the traffic condition of the call already connected to the direct VPC, and it is not necessary to perform the call admission control for each VPL forming the direct VPC.

[Description of Call Switching Connection Operation] Next, the call switching connection operation of this embodiment will be described with reference to FIG. Here, a case will be described in which the terminal accommodated in the subscriber VCH 261 makes a call to the terminal accommodated in the subscriber VCH 264.

The subscriber VCH 261 analyzes the called number,
First, the direct VPC 282 is selected, and the call admission control for the direct VPC 282 is performed in order to set the VC in it.
If it can be accepted, the VCI is determined, and the connection information is transferred to the subscriber VCH 264 via the control line 311, the signal repeater 47, and the control line 314, and the subscriber VCH 264.
Connects to the receiving terminal based on the connection information. Subsequent operations are similar to those of the conventional STM switching network, and therefore description thereof will be omitted. The subscriber VCH 264 does not need to perform call admission control because the subscriber VCH 261 directly connects to the direct VPC 2
This is because, if the call admission control of 82 is performed, the call admission control for the VPLs constituting the call admission control is satisfied as described above.

Direct VPC at subscriber VCH 261
If the call admission control of 282 is not satisfied,
Unlike the case of the first embodiment shown in (1), the call is not lost and the call is detoured to the detour VPC 293 connected to the subscriber VCH 264, and an attempt is made to set a VC for this VPC. Detour VPC 29
Unlike the direct VPC 282 and the like, 3 and the like perform call admission control for each VPL that constitutes the detour VPC as described in the first embodiment shown in FIG. This is a detour VPC
Is because the situation of call admission control in the VPLs that compose it is different.

Here, by performing the call admission control in the VPL that constitutes the detour VPC, the VPHs 271 to 274 become equivalent to the relay VCH as described in the first embodiment, and the traffic is converged and the VPL or VPL is converged. Transmission lines 301, 30
2,303,304,307 can be used efficiently. That is, when it corresponds to STM, VPH27
It is equivalent to a network in which transit exchanges are installed at 1 to 274 and designed to carry traffic overflowing from a direct path. It is well known in STM as a theory of a bypass relay network that such a network is economical, and ATM has the same economic effect. As described above, even when the direct VPC and the detour VPC pass through the same transmission line and the same VPH, the direct VPC does not need to be processed by the connection management device 48. Therefore, the direct VPC is the detour VPC. It is more economical and there are reasons to choose a direct VPC first.

If this embodiment is applied to the configuration shown in FIG. 1, for example, a direct VPC is set between the subscriber VCH 41 and the subscriber VCH 43, and a call overflowing from the direct VPC is diverted to the VPC 61. As for the direct VPC, the processing by the connection management device 48 is not required, so that the connection management device 48 can be economically configured as much as the load is lightened. Since the VPL that constitutes the direct VPC set in the transmission path 73 is used only for the calls of the subscriber VCH 41 and the subscriber VCH 43, it is necessary to provide a direct VPC of what capacity. It is necessary to separately consider whether the network is optimal as a whole. Further, in the configuration of the second embodiment shown in FIG. 7, how much capacity the direct VPC 282 has is optimum. As described above, the theory of the detour relay network in STM can be applied to this problem.

By applying the present invention, it is possible to realize a function equivalent to a relay VCH with a VPH that is cheaper than the relay VCH, and to construct an ATM network with high economic efficiency. Incidentally, fault tolerance and a connection management apparatus 48 described in the first embodiment, with respect to measures such as changing the connection management apparatus 48 control parameters received N _i fault information from the VPH, applied to the second embodiment can do. Also, FIG.
In the above, the subscriber VCHs 261 to 264 may be VPC termination points, and may be, for example, relay VCHs.

[Explanation in the case of performing 1-to-n connection by VPH] Although the function of VPH has already been explained in the explanation of FIG. 3, the present invention can be applied to 1-n connection.

FIG. 8 shows a 1-to-n connection in VPH.
It is a block diagram which shows the Example structure. In the figure, symbols
321 to 325 are subscriber VCHs, and 331 to 333 are
VPH, reference numerals 341 to 347 are transmission lines, reference numerals 350 to 3
Reference numeral 53 is a VPC, and reference numerals 511 to 515 are control lines. Well
Also, the VPC 352 makes a one-to-two connection with the VPH 331.
VPL352₁, 352₂, 352₃And V
PL352₁, 352 _Four, 352_FiveComposed of. You
That is, since VPC 352 branches in the middle,
The VPC termination points are the subscriber VCHs 324 and 325.
Become.

In the subscriber VCH 322, the subscriber VC
Calls that simultaneously connect VCs to H324 and 325 (for example, the same
Information communication), the VPC 352 selects and VPL3
52 ₁Call admission control related to
Via the control line 512, the signal repeater 47, and the control line 55
The connection information is transferred to the connection management device 48. Connection management device
48, VPL352₂, 352_FourCall acceptance system
Control, VPL352₂, 352_FourIn both
If it is determined that the call can be accepted, the connection information is
It is added via the control line 55, the signal repeater 47, and the control line 512.
It is returned to the incoming VCH 322. The subscriber VCH322 is
When VCI connection information is received, VCI is determined and control information is added.
Transfer to the incoming VCH 324, 325, and then connect in the same way
Do the work. In this embodiment also, the VPH 331
Traffic is converged similarly to the relay VCH, and VPL35
Two₂(Transmission path 344), VPL 352_Four(Transmission line 34
5) can be used efficiently. With the above explanation
Is a one-to-n connection made only by one VPH331.
However, more than one VPH can have 1-to-n connection at the same time.
The same is true when performed.

[Explanation when n-to-1 Connection is Performed in VPH] FIG. 9 is a block diagram showing the configuration of an embodiment in which n-to-1 connection is performed in VPH.

In the figure, reference numerals 361 to 365 are subscriber VCHs, reference numerals 371 to 372 are VPHs, and reference numerals 381 to 381.
Reference numeral 86 is a transmission line, reference numerals 391 to 393 are VPCs, reference numeral 40
Reference numerals 1 to 405 are control lines. In addition, VPC391,39
2 has a 2: 1 connection with the VPH 371, so VPL 391 ₁ , 391 ₂ , 391 ₃ and VPL ₃ respectively.
It is composed of 92 ₁ , 391 ₂ , and 391 ₃ . That is, the VPCs 391 and 392 are VPH371 and have a 2: 1 V
Since PL is connected, VPL391 ₂ , 391 ₃
Are shared and the right VPC termination point is the same subscriber VCH
It becomes 364.

The reason for doing this is that the subscriber VCH 36
4 between the subscriber VCH 361 and the subscriber VCH 361, 362
This is because C is set, but since the VPH 371 makes a two-to-one connection, the VPH 371 and thereafter can be treated as one VPC for management. For example, subscriber VC
With H364, it is sufficient to manage one VPL 391 ₃ and the connection control becomes simple.

In the subscriber VCH 361, the subscriber VC
When a call to H364 occurs, the subscriber VCH 361 VPs
C391 is selected to perform call admission control for VPL391 ₁ , and control line 403, as described in the above embodiment,
The connection information is transferred to the connection management device 48 via the signal repeater 47 and the control line 55. In the connection management device 48, the VPL
The call admission control for 391 ₂ is performed, and thereafter, the connection operation is similarly performed. Also, from the subscriber VCH 362 to the subscriber VCH
The same is true for connecting a call to 364.

The problem here is how to determine the VCI. That is, in the above-described embodiment, the subscriber VCH3
If 61 determines any free VCI, then V
Since n: 1 connection is made in PH371, VPC39
VCI used in 1 and VC used in VPC392
I may overlap with I, in which case the VPC termination point is the subscriber VCH 364 and the cell from VPC 391 and V
It becomes impossible to identify the cell from the PC 392. To solve this, the connection management device 48 uses the VPC 391 and the VP.
The VCIs in the C392 are managed so that the VCIs used by the VPCs 391 and 392 do not overlap each other.
Assign I. As another method, a method of previously assigning VCIs to the subscriber VCHs 361 and 362 so that they do not overlap (for example, even number and odd number) may be used.
In the above description, the n-to-1 connection is performed only by one VPH 371, but the same is true when the n-to-1 connection is simultaneously performed by a plurality of VPHs.

[Explanation of Third Embodiment of the Present Invention] In the embodiment described above, the VC is set in the VPC.
The present invention can also be applied to VPC capacity setting control. The description of this embodiment will be given with reference to FIG.

Subscriber VCH 191 to subscriber VCH 19
VPC164 is set to 4 and VPL164₁~ 164
_FourAre connected by VPH 161-163 and VPC 164 is
Composed. Here, VPL has already been set and VPH
161 to 163 are VPL164₁~ 164_FourConnection of
(The VPI conversion table 102 in FIG. 3 is assumed to be
Etc. is registered as VPI). In the first embodiment, this
When setting up the VC on the VPC 164,
VPL164₁~ 164_FourCall admission control regarding
However, a certain capacity (bandwidth) is allocated to the VPC 164 in advance.
And the subscriber VCH 191 is free to use within its capacity
There is also a method of using the VPC 164 (setting of VC). This
In the case of,
L164 ₂, 164₃Because the capacity of is secured (this
The operation will be described later), and VPL164 for each call₂，
164₃Connection management device without the need to perform call admission control for
The processing load of 48 can be reduced.

Furthermore, if the capacity of the VPC can be easily changed according to the present invention, the following advantages can be obtained. For example, the capacity of the VPC 164 is allocated to 52 Mbps during the day and 152 Mbps during the night.
Assuming that the capacity of 5 is allocated to 152 Mbps during the daytime and 52 Mbps during the nighttime, since the VPCs 164 and 165 share the transmission paths 173 and 175, the transmission path 17
The transmission capacity of 3,175 can be effectively used.

The operation of VPC capacity change control will be described below. When the subscriber VCH 191 requests to change the capacity of the VPC 164 from, for example, 52 Mbps to 152 Mbps, the VPC connection information is transferred to the connection management device 48 via the control line 201, the signal repeater 47, and the control line 55.
When the connection management device 48 receives this connection information, it performs call admission control for the transmission lines 171, 173, 175, 176. The call admission control, the VPL164 ₁ ~164 ₄
It is intended to determine whether it can change to 152Mbps, the cell of another VPL that are accommodated in the same transmission path 171,173,175,176 also this determination by changing the VPL164 ₁ ~164 ₄ to 152Mbps It is based on whether the transmission quality is satisfied. In the call admission control described in the first embodiment, the call admission control is performed on the VPL in order to determine whether the requested capacity of the VC can be set on the VPL. In this case, the capacity of the VPL on the transmission line is set. Call admission control on the transmission path is performed to determine whether the call can be set.

When the call admission control for the transmission lines 171, 173, 175, 176 makes it possible to change to 152 Mbps, the connection management device 48 informs the control line 55, the signal relay 47, and the control that the change can be made. The subscriber VCH 191 is notified via the line 201, and the connection management device 48
The data relating to the allocated capacities of the VPLs 164 _{1 to} 164 ₄ which are managed by the above are updated. Subscriber VCH 191
When the capacity of VPC164 can be changed to 152Mbps,
VPC 164 is optionally used within its capacity. On the other hand, when the call admission control for the transmission lines 171, 173, 175, 176 cannot change to 152 Mbps, that effect or the maximum admissible capacity is set to the subscriber VCH 19
1 and the subscriber VCH 191 uses the capacity of the VPC 164 at the previous value or in the specified capacity range.
It should be noted that the subscriber VCH 191 displays the fact in the connection information and notifies the connection management device 48 of whether or not to use the mode in which the maximum acceptable capacity of the connection management device 48 is allocated to the subscriber VCH.

The capacity of the VPC 164 is changed from 152 Mbps to 52 Mbps
If the subscriber VCH 191 is changed to the control line 20
1, via the signal repeater 47 and the control line 55, the connection management device 48 is notified of the change. When the connection management device 48 receives this notification, the VPL 164 that constitutes the VPC 164
Updates the data related to quota _{1-164 4.}

In the above description, the VPC 164 is changed with respect to day and night traffic fluctuations between the subscriber VCH 191 and the subscriber VCH 194. However, the leased line time when the VPC 164 is provided as a leased line or a VPC of a virtual private network. It can also be applied to switching control of used services.

10 and 11 are flowcharts for explaining the operation of the connection management device 48. In FIG. 10, for example, when the connection management device 48 receives the capacity allocation connection information of the VPC 164 from the subscriber VCH 191 (S31), the VPL _i that constitutes this VPC is extracted (S32). The capacity of the transmission line i accommodating VPL _i is C _Ti
Let C _Q be the capacity required by this VPC, and the transmission path i
Let ΣC _Vij be the total sum of the capacities C _Vij assigned to VPL _j (j includes i) included in ΣC _Vij and compare ΣC _Vij + C _Q with C _Ti for all i (S33).
~ 35). ΣC _Vij + C _Q ≦ C _Ti for all i
If it becomes, it is returned that allocation is possible (S3
6, 37), and the data regarding the allocated capacity of VPL _i is updated (S38).

On the other hand, when ΣC _Vij + C _Q ≦ C _Ti is not satisfied, and a mode for notifying the allocatable capacity =
In the case of 1, the minimum value of the allocation capacity of VPL _i is returned (S39 to 41), and in the case of mode ≠ 1, the fact that allocation is impossible is returned (S42).

The above operation is for increasing the capacity of the VPC, but in the case of decreasing it, the data concerning the allocated capacity of VPL _i is simply updated as shown in FIG. 11 (S51, 52).

[Explanation of First Embodiment when Connection Management Device is Not Used] In the embodiment shown in FIG. 1 and the like, the case where the connection management device 48 performs VPL call admission control has been described.
The present invention can be implemented without using the connection management device 48.

FIG. 12 is a block diagram showing the ATM network configuration of the first embodiment when the connection management device is not used. In the figure, reference numerals 531 to 537 are subscriber VCHs, reference numeral 5
41-543 are VPHs, 551-559 are transmission lines,
Reference numerals 561 to 564 are VPCs, and reference numerals 591 to 597 are control lines. Also, subscriber VCH531 and subscriber VCH
The VPC 561 set between the VPC 561 and the
1 _{1 to} 561 ₃ . Subscriber VCH532
VPC 562 set up between the VCH 536 and the subscriber VCH 536
It is composed of VPL562 ₁ ~562 _4. VPC563 set between the subscriber VCH533 the subscriber VCH536 is composed of VPL563 ₁ ~563 _4. VPC564 set between the subscriber VCH534 the subscriber VCH537 is, VPL564 ₁ ~5
It is composed of 64 ₂ .

Here, from the subscriber VCH 532 to the subscriber V
Call to CH536, subscriber VCH533 to subscriber VC
Calls to H536 and calls in the opposite directions will be described as an example. First, in the subscriber VCH 532, the subscriber V
When a call to CH536 occurs, the subscriber VCH 532 analyzes the destination, selects the VPC 562, and performs the call admission control of the VPL 562 ₁ as described in the above embodiment. If the call admission control cannot be accepted, the call is lost. If the call admission is acceptable, an empty VCI is selected and connection information including a called number and the like is supplied to the control line 593, the signal repeater 47, and the control line 595. To the subscriber VCH 536 via. At subscriber VCH 536, VPL 562 ₂ for this call
Perform call admission control for ～562 _4, returns to that effect as call loss in the case of can not be accepted, the control line 595, a signal repeater 47, subscriber VCH532 via a control line 593. On the other hand, if it can be accepted, the corresponding terminal is called. The subsequent operation is similar to that of the above-described embodiment.

Subscriber VCH 533 to subscriber VCH 53
The same is true for calls to 6. That is, the subscriber VC
The H533 selects the VPC 563, performs call admission control for the VPL 563 ₁ , and if the admission is possible, an empty VC
Select I to display connection information including the called number and other information on the control line 5
92, the signal repeater 47, and the subscriber line V via the control line 595.
Transfer to CH536. The subscriber VCH 536 performs call admission control for the VPLs 563 _{2 to} 563 ₄ for this call, and if the call can be admitted, the corresponding terminal receives the call. The subsequent operation is similar to that of the above-described embodiment.

From the subscriber VCH 536 to the subscriber VC
When a call to H532 occurs, the subscriber VCH 536
Select C562 (VPC can be used from both) and select VP
L562 ₄ ~562 ₂ performs call admission control for the control line 595 the connection information by selecting the VCI of empty if possible receptionist VPC562, signal repeater 47, the control line 59
2 to the subscriber VCH 532. Subscriber VC
In H532, the call admission control for the VPL 562 ₁ for this call is performed, and if the call can be admitted, the call is received at the corresponding terminal. The subsequent operation is similar to that of the above-described embodiment.

In the above description, VPC 561-5
Since 64 is a bidirectional VPC that can be used from both directions, contention of VCI occurs due to the time difference of access timing from both directions. This is also the case with the above-described embodiment, and is an unavoidable problem that occurs when VCIs are independently captured by a plurality of systems. However, it can be solved because the same method can be used as the competition processing in the bidirectional line in the conventional STM. If the VPC is a one-way VPC that is used from one direction, the use efficiency of the VPC is slightly reduced, but the problem of contention is avoided. The present invention is
It can be applied to both unidirectional VPC and bidirectional VPC.

The call admission control in the subscriber VCH 532 is the same as that in the above-mentioned embodiment, so the description thereof will be omitted.
The call admission control performed by the subscriber VCH 536 is slightly different and will be described below.

[0097] in VPL562 ₂ and VPL563 ₂ and allocates a common volume, allocates a common capacity and VPL562 ₃ and VPL563 _3, VPL562 ₄ and VPL56
A common capacity is allocated to 3 ₄ (usually the same capacity in each section, but different capacity may be used). In order to secure this capacity, the used capacity of the VPL is used within the allocated capacity in the call admission control for other VPLs. The subscriber VCH 536 has the smallest capacity among the commonly allocated capacities as data, and performs call admission control based on this data. In order to simplify the explanation, as described in FIG. 1, the call admission control is based on the number of connected calls, and the maximum number N of calls that can be connected to the smallest capacity among the allocated capacities is set as the call admission control parameter. And

At subscriber VCH 536, VPC 56
The number of calls connected to ₂ is managed as n ₁ , and the number of calls connected to VPC 563 is managed as n _{2, and} as described in FIG. 1, if M = n ₁ + n ₂ and M ≧ N, it is not accepted. , In other cases, it is possible to accept. That is, as long as M is less than N, the VC of the next call is set to VPC562 or VPC.
Even if it is set to PC563, the cell quality of all calls including already connected calls is satisfied. Taking VPC562 as an example, for VPL562 ₁ subscriber VCH532
If call admission control is already possible in, cell quality is guaranteed. Also, regarding the VPLs 562 _{2 to} 562 ₄ , the call admission control is performed by the subscriber VCH 536 at the minimum value of the capacity commonly assigned to each VPL, and the fact that the reception is possible guarantees the cell quality in the VPLs 562 _{2 to} 562 ₄ . As a result, the cell quality is guaranteed in all VPLs forming the VPC 562. When the call ends, the VPC set in the VPC 562 or VPC 563 is set.
Since C is released and the subscriber VCH 536 is always involved in the termination of the call, the value of n ₁ or n ₂ can be updated. That is, the subscriber VCH 536 is the VPC 562,
It is possible to completely manage the usage status of the 563.

The above operation is adapted to the conventional STM.
Then, the subscriber VCH 532 seizes the line in the path (call
Connection information) and transfer connection information to the subscriber VCH 536.
Send and receive at the terminal. However, in STM, the subscriber VC
H536 captures the line again (supports call admission control)
Absent. Also, when the relay VCH is used, the subscriber V
Call admission control is not necessary even for CH536. That is, this
Is different from the conventional connection control method. of course,
VPL562 that constitutes VPC562₁~ 562 _FourThe content of
Same amount and dedicated capacity for each VPL
If they are installed, they will be accommodated in the same transmission line as these VPLs.
Subscriber VCH because there is no influence from other VPLs
If call admission control is performed at 532, a call is made at the subscriber VCH 536.
Admission control is not required. However, in this case VPC5
The required capacity for 62 is fixedly allocated
So, these capacities are subscriber VCH532 and subscriber VCH
Will be used only for 536 calls,
Or the transmission line that accommodates it can be used efficiently
Absent. When STM is supported, the subscriber VCH532 and
A path is set up between the incoming VCH 536 and the line
Only for calls between subscriber VCH 532 and subscriber VCH 536
Equivalent to use.

As described above, the subscriber VCH531
~ 537, VPH 541-5 by call admission control
43 can be made equivalent to the relay VCH, and the traffic can be converged in the VPH. It should be noted that, without using the connection management device described with reference to FIG.
VPL562 ₂ to 562 that configure VPC562 with 36
_The reason why call admission control in ₄ is possible is the subscriber VC
This is because the H536 could have the information connected to the VPCs 562 and 563. Further, in the present invention, as compared with the case where the relay VCH is installed, the subscriber VCHs 532, 5
Although call admission control processing is required when 36 or the like becomes the receiving side, call admission control is originally small in terms of overall call processing and does not overwhelm the call processing of the subscriber VCH 536 or the like. .

[Explanation of the Second Embodiment when the Connection Management Device is not Used] FIG. 13 is a block diagram showing the ATM network configuration of the second embodiment when the connection management device is not used.

In the figure, reference numerals 601 to 604 are subscriber VCHs, reference numeral 605 is VPH, reference numerals 651 to 654 are transmission lines, reference numerals 611 to 616 are VPCs, and reference numerals 661 to 66.
Reference numeral 4 is a control line. Further, the VPC 611 set between the subscriber VCH 601 and the subscriber VCH 603 is a VP.
L611 _{1 to} 611 ₂ . Subscriber VCH
VPC established between 601 and subscriber VCH 604
612 is constituted by VPLs 612 _{1 to} 612 ₂ . The VPC 613 set between the subscriber VCH 601 and the subscriber VCH 602 has VPLs 613 _{1 to} 613 _2.
It is composed of Subscriber VCH 602 and subscriber VCH
The VPC 614 set between the VPC 603 and the
4 _{1-614 2} by constructed. Subscriber VCH 602
615 established between the VCH and the subscriber VCH 604
Is composed of VPL 615 _{1 to} 615 ₂ . The VPC 616 set between the subscriber VCH 603 and the subscriber VCH 604 is composed of VPL 616 _{1 to} 616 ₂ .

The VPL 6 accommodated in the transmission line 651
A transmission line 651 is commonly used for 11 ₁ , 612 ₁ , and 613 _1.
Of the VPL 613 ₁ ,
The capacities of the transmission lines 652 are commonly assigned to 614 ₁ and 615 _1, and the capacities of the transmission lines 653 are commonly assigned to VPL 611 ₂ , 614 ₂ and 616 _1.
The capacity of the transmission line 654 is commonly assigned to 2 ₂ , 615 ₂ , and 616 ₂ . The call admission control of each VPL in the subscriber VCHs 601 to 604 is performed based on the number of connected calls as described above, and the number of calls set in the three VPLs accommodated in the transmission path is set to n ₁ , n _2. , N ₃ , M = n
₁ + n ₂ + n ₃ and the control parameter is the maximum number of calls N that can be connected to the capacity of the transmission line, if M ≧ N, it is rejected as a call loss, and if M <N, it is connectable .

Here, the subscriber VCH 601 to the subscriber V
The connection operation will be described by taking a call to CH 603 as an example. When a call is made on the subscriber VCH 601, V
The PC 611 is selected to perform call admission control in the VPL 611 ₁ . That is, VPL 611 ₁ , 612 ₁ , 61
The number of connected calls of 3 ₁ is n ₁ , n ₂ , n ₃ and M = n ₁ +, respectively.
With n ₂ + n ₃ and N being the maximum number of calls that can be connected to the capacity of the transmission line 651, it is determined from the above relationship whether or not the call can be accepted.
If it can be accepted, a free VCI of the VPC 611 is selected, and the connection information is transferred to the subscriber VCH 603 via the control line 662, the signal repeater 47, and the control line 664, and at the same time n
Update ₁

The subscriber VCH 603 carries out call admission control upon receipt of the connection information. That is, VPL611 ₂ , 6
The number of connected calls of 14 ₂ and 616 ₁ is n ₁ , n ₂ and n, respectively.
₃ , M = n ₁ + n ₂ + n ₃ , and the maximum number of calls connectable to the capacity of the transmission path 653 is N, and it is determined from the above relationship whether or not the call can be accepted. If it can be accepted, the call arrives at the terminal and n ₁ is updated at the same time. The subsequent operation is similar to that of the above-described embodiment.

For example, VPL 611 is provided on the transmission line 651.
₁ , 612 ₁ and 613 ₁ are housed in each VP
L is exclusively used for a call between the subscriber VCHs 602, 603, and 604. However, since the capacity of the transmission line 651 is commonly assigned to each VPL as described above, the transmission line 65 is used.
1 is commonly used for all calls. This is VPH60
5 indicates that it operates as if it were a relay VCH. The same applies to other transmission lines.

[Explanation when the function of the connection management device is implemented in the subscriber VCH] In the above-described embodiment, the connection management device 4 is used.
8 is installed in an independent network, but its location is not limited as long as the function of the connection management device 48 described above is realized.

FIG. 14 is a block diagram showing an ATM network configuration for explaining an embodiment in which the function of the connection management device is installed in a specific subscriber VCH. In the figure, reference numerals 671 to 67
Reference numeral 6 is a subscriber VCH, reference numerals 681 and 682 are VPHs, reference numerals 691 to 697 are transmission lines, and reference numerals 701 to 706 are control lines. Although not shown in the drawing, the subscriber VCH67
It is assumed that a VPC is set in the mesh between 1 to 676 and accommodated in each transmission path. Subscriber VCH
The usage status of the VPL in the transmission path between the VPH 681 and the VPH 682 is managed by each subscriber VCH, and the usage status of the VPL accommodated in the transmission path 694 is managed by the subscriber VCH 674, for example. And

Here, from subscriber VCH 671 to subscriber V
The connection operation will be described by taking a call of CH676 as an example. When a call is made in the subscriber VCH 671, the call admission control is performed on the VPL in the transmission path 691 in which the VPC to the subscriber VCH 676 is accommodated based on the analysis of the called number.
If the reception is possible, the subscriber VCH 671 captures the VCI, and first, the control line 701, the signal repeater 47, and the control line 70.
4 to transfer the connection information to the subscriber VCH 674.
In the subscriber VCH 674, the transmission line 694 is used as described above.
The call admission control is performed for the VPL accommodated in.
Of course, since the capacity is commonly assigned to a plurality of VPLs, call admission control is performed in consideration of the number of connected calls on other VPLs. If it can be accepted, the connection information is sent to the control line 70.
4, the signal repeater 47, the subscriber VC via the control line 706
Transfer to H676 (or return to subscriber VCH 671). The subscriber VCH 676 has a transmission line 697.
The call admission control is performed for the VPL that composes this VPC. If it can be accepted, the call arrives at the terminal, and if it cannot be accepted, the call is lost. Subsequent processing and subscriber VCH6
The operation in the case where the acceptance at 74 is not possible is the same as that of the above-mentioned embodiment.

When the call ends, the subscriber VC
The information will also be reported in H674. Conversely, the subscriber VC
For a call from the H676 to the subscriber VCH 671, call admission control is performed on the VPL accommodated in the transmission line 697 by the subscriber VCH 676, and the connection information is sent to the subscriber VCH 6 1.
74. The call admission control is performed on the VPL that composes this VPC accommodated in the transmission path 694 by the subscriber VCH 674, and if the admission is possible, the connection information is sent to the subscriber VC.
Transfer to H671. The subscriber VCH 671 has a transmission line 69.
Call admission control is also performed for VPLs within 1. As described above, the function of the connection management device 48 shown in the above-described embodiment can be given to a specific subscriber VCH such as the subscriber VCH 674. Therefore, in such a configuration, the connection management device is not needed, and an economical configuration is possible.
This requires a signal transmission / reception function (for example, No. 7 common line signaling method) and a call admission control function for the connection management device as the functions of the connection management device, but these functions are basically subscribers. Subscriber VCH as it is equipped with VCH
However, there is no new function to add.

[Explanation of Relationship between VPH and Connection Control] As described in FIG. 1, FIG. 5, FIG. 12, FIG. 13, etc., the connection control method of the present invention basically includes call admission control. VPH is having no interface.
That is, VPH is an entity that provides VPC,
Connection control is executed only at the VPC termination point and the connection management device (or a device having that function).

[Supplementary Explanation of VPC Termination Point] As described above, the VPC between the subscriber VCHs has been described as shown in FIG. 1 and FIG. , For example, between relay VCH, subscriber VCH and relay VCH
The present invention can be widely applied to a private network, or between a subscriber premise device and a subscriber VCH, a concentrating system in a subscriber network, a LAN or WAN of a private network, and a leased line network.

[Supplementary Explanation of Performing Call Admission Control for Each VPL] Above, as shown in FIGS. 1 and 5, the capacity is commonly assigned to a plurality of VPLs accommodated in the same transmission path. In this case, it is significant to perform call admission control for each VPL, but it is also effective when a capacity is exclusively assigned to the VPL and the capacities are not all the same. That is, by performing call admission control for each VPL, each VPL except the VPL directly connected to the VPL termination point at the VPC termination point of the subscriber VCH or the like.
It is not necessary to manage the capacity of each VPL (for example, to grasp the minimum capacity of each VPL). Further, even if the capacity of each VPL changes due to a failure of the transmission line or other factors, it is not necessary to take any part in the change at the VPC termination point such as the subscriber VCH.

[0114]

As described above, according to the present invention, the VP is controlled by the function (connection management device) for managing the usage status of the VPL.
H can have a traffic convergence function, and VPL
The VPH that makes the connection can be equivalently used as the relay VCH.

Further, according to the present invention, VPH can be equivalently used as a relay VCH by controlling the connection of only the VPC termination point, depending on the application field, without using the connection management device.

Therefore, the relay VCH which is more expensive than the cost of the VPH + connection management device or the cost of the VPH.
Without using, it is possible to obtain traffic convergence, traffic fluctuation absorption, and cell statistical multiplexing effects. That is, an economical ATM network can be constructed.

Further, the capacity of the VPC can be easily changed, and as a result, the transmission line accommodating the VPC can be efficiently used, and from this point, it is economical.
A TM network can be constructed.

[Brief description of drawings]

FIG. 1 is a block diagram showing an ATM network configuration of a first embodiment of the present invention.

FIG. 2 is a diagram showing a relationship between VPC and VPL.

FIG. 3 is a diagram illustrating a functional principle of VPH.

FIG. 4 is a flowchart illustrating a procedure of call admission control of the connection management device.

FIG. 5 is a block diagram showing an ATM network configuration when a VPC is composed of a larger number of VPLs.

FIG. 6 is a block diagram showing an ATM network configuration when a plurality of connection management apparatuses are installed.

FIG. 7 is a block diagram showing an ATM network configuration of a second embodiment of the present invention.

FIG. 8 is a block diagram showing a configuration of an embodiment for performing 1-to-n connection in VPH.

FIG. 9 is a block diagram showing a configuration of an embodiment for performing n-to-1 connection in VPH.

FIG. 10 is a flowchart illustrating an operation of the connection management device.

FIG. 11 is a flowchart illustrating an operation of the connection management device.

FIG. 12 is a block diagram showing an ATM network configuration of a first embodiment when a connection management device is not used.

FIG. 13 is a block diagram showing an ATM network configuration of a second embodiment when a connection management device is not used.

FIG. 14 is a block diagram showing an ATM network configuration for explaining an embodiment in which the function of the connection management device is installed in a specific subscriber VCH.

FIG. 15 is a block diagram showing a conventional network configuration method for configuring a communication network by connecting a plurality of exchanges with a line bundle.

FIG. 16 is a diagram showing an ATM cell structure.

FIG. 17 is a diagram showing a relationship between VC, VP and a transmission line.

[Explanation of symbols]

1 Terminal 2 (32) Subscriber switch (subscriber VC handler (subscriber VCH)) 3 (33) Path (VP) 4 (34) Relay switch (relay VC handler (relay VC)
H)) 11 cell 12 header 13 information field 14 virtual path identification (VPI) field 15 virtual circuit identification (VCI) field 16 control information field 21 VC 22 VP 23 transmission path 41-44, 191-195 subscriber VCH 45, 46 , 161 to 163 VPH 47 Signal relay 48 Connection management devices 51 to 57, 201 to 205 Control lines 61 to 66, 164 to 166 VP connection (VP
C) 61 _{1 to} 61 ₃ , 62 _{1 to} 62 ₃ , 63 _{1 to} 63 ₃ , 6
4 ₁ to 64 ₃ , 65 _{1 to} 65 ₂ , 66 _{1 to} 66 ₂ , 16
4 ₁ to 164 ₄ VP link (VPL) 71~75,171~177 transmission path 81 and 82 VPC end points 83 to 85 VPH 86 to 89 VP link (VPL) 90 VPC 101 cell switch 102 and 103 VPI conversion table 104 ~ 106 fields 111-118 cells 223,228,261-264,321-325,3
61-365,531,537,601-604,67
1-676 Subscriber VCH 224-227, 271-274, 331-333, 3
71,372,541-543,605,681,68
2 VPH 241 to 245 VP link (VPL) 251 to 254, 311 to 314, 401 to 405, 5
11-515, 591-597, 661-664, 70
1-706 Control line 281-286 Direct VPC 291-296 Detour VPC 301-307,341-347,381-386,5
01-505,551-559,651-654,69
1 to 697 Transmission lines 351 to 353, 391 to 393, 561 to 564, 6
_{11~616 VPC 352 1 ~352 5, 391} 1 ~391 3, 392 1,
561 _{1 to} 561 ₃ , 562 _{1 to} 562 ₄ , 563 ₁ to
563 ₄ , 564 _{1 to} 564 ₃ , 611 _{1 to} 611 ₂ ,
612 _{1 to} 612 ₂ , 613 _{1 to} 613 ₂ , 614 ₁ to
614 ₂ , 615 _{1 to} 615 ₂ , 616 _{1 to} 616 ₂
VP link (VPL)

Claims (11)

[Claims] 1. A call admission control is performed for each of a plurality of virtual path links that make up a virtual path connection in the asynchronous transfer mode and the allocated capacities do not necessarily match, and based on the result, the virtual path connection is set in the virtual path connection. A connection control method in an asynchronous transfer mode characterized by setting a virtual line. 2. The first virtual path link and another virtual path connection are provided in at least one of the transmission paths accommodating a plurality of first virtual path links forming the first virtual path connection. The connection control method in the asynchronous transfer mode according to claim 1, wherein a common capacity is allocated to the second virtual path link that constitutes it. 3. The call admission control for each virtual path link to which a common capacity is allocated is performed based on the minimum capacity among the capacities fixedly allocated to each virtual path link. The connection control method in the asynchronous transfer mode according to claim 2. 4. A connection management device having a function of performing call admission control for a virtual path link other than a virtual path link accommodated at least at a virtual path termination point, and a virtual connection set between the virtual path termination points. 4. Asynchronous transfer according to claim 1, wherein call admission control is performed for a virtual path link managed by the connection management device in response to a request for setting a virtual circuit in a path connection. Connection control method in mode. 5. A specific virtual circuit handler is provided with a function of performing call admission control for virtual path links excluding virtual path links accommodated at least at the virtual path termination points, and is set between the virtual path termination points. 4. The asynchronous according to claim 1, wherein call admission control is performed for a virtual path link managed by the virtual circuit handler in response to a request for setting a virtual circuit in a virtual path connection. Connection control method in transfer mode. 6. The capacity of a virtual path link accommodated in this virtual path handler is changed based on abnormality information from the virtual path handler connecting the virtual path link, and call admission control is performed using this capacity. Claim 1 characterized by the above-mentioned.
The connection control method in the asynchronous transfer mode according to claim 5. 7. The asynchronous transfer mode according to claim 1, wherein the capacity of the virtual path link is changed based on a time schedule, and the call admission control is performed using this capacity. Connection control method in. 8. The connection control method in the asynchronous transfer mode according to claim 4, wherein when the connection management device fails, call admission control is performed at a virtual path termination point using a predetermined virtual path connection capacity. . 9. When a direct virtual path connection and a detour virtual path connection composed of one or more virtual path links are set between two nodes and a virtual circuit is set between the nodes, first, the direct virtual path connection is set. When the call admission control is performed on the connection and the setting of the virtual line is tried, and when the call admission control is satisfied, the virtual line is set to the direct virtual path connection, and the call admission control is not satisfied. 9. The connection control method in the asynchronous transfer mode according to claim 1, wherein the detour virtual path connection is selected as the destination. 10. A call admission control in a transmission line accommodating each virtual path link is performed in response to a virtual path connection capacity change request made from a termination point of the virtual path connection configured by a plurality of virtual path links, A connection control method in an asynchronous transfer mode, wherein the capacity of the virtual path connection is allocated based on the result. 11. A first virtual path connection composed of a plurality of first virtual path links and a second virtual path connection composed of one or more second virtual path links are set, and The two path termination points of the first virtual path connection are a first node and a second node, respectively, and the two path termination points of the second virtual path connection are a third node and a second node, respectively. And in the asynchronous transfer mode network in which the first virtual path link and the second virtual path link are accommodated in the same transmission line and at least one virtual path link sharing the capacity exists, Node performs call admission control for a virtual path link in a section up to immediately before the same transmission path that first appears from the first node, and the second node moves from the same transmission path to the front. Call admission control is performed for the virtual path link up to the second system, a virtual circuit is set for the first virtual path connection based on the result, and the virtual circuit is set for the first node from the third node for the first time. Call admission control is performed for virtual path links in the section up to immediately before the same transmission line that appears, and call admission control is performed for virtual path links in the section from the same transmission path to the second system at the second node. And a virtual circuit is set in the second virtual path connection based on the result of the above.