JPH0918515A - Bandwidth variable communication device - Google Patents

Abstract

(57) Abstract: To control traffic flowing through a transmission line of an ATM network at high speed and flexibly. SOLUTION: In a subscriber exchange 11, empty bandwidths of exchange buffers and transmission lines belonging to respective connections are stored in an empty bandwidth table 101 in advance, and when a bandwidth change request is issued from a terminal device 31. Whether or not to change the band is determined based on the values stored in the empty band table 101.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention is used for transmitting information in an asynchronous transfer mode (hereinafter referred to as "ATM"). In particular, it relates to a dynamic band change type communication network capable of changing the band of a connection connecting between subscribers.

[0002]

2. Description of the Related Art As a transmission service between terminals in an ATM network, a conventional fixed bit rate (CB) has been used.
In addition to an R: Constant Bit Rate (VBR) type service or a variable bit rate (VBR) type service, an ABR (Available Bit Rate) type service is newly noticed. In the ABR type service, each user can control its cell transmission rate based on the ABR protocol, and operates so as to decrease the cell transmission rate when the network is busy and increase the cell transmission rate when the network is idle. . ABR technology is being standardized by the ATM Forum and ITU-TS (Telecommunications Standardization Sector).

FIG. 5 shows an ATM providing an ABR type service.
FIG. 10 is a block diagram showing a conventional variable bandwidth communication device that constitutes a network. In this example, two subscriber exchanges 11 and 14 are connected via a relay transmission line 21, a relay exchange 12, a relay transmission line 22, a relay exchange 13 and a relay transmission line 23, and the subscriber exchange 11 has a terminal device. Three
1. The terminal device 32 is accommodated in the subscriber exchange 14.
The subscriber exchanges 11 and 14 and the transit exchanges 12 and 13 perform switching connection of a virtual channel (VC) which is a logical line, and a "virtual channel handler (VC)
H) ”.

When the terminal devices 31 and 32 want to transfer information such as file transfer, they send a resource management cell (RM cell) to the network and desire to change the band. Subscriber switch 11, transit switch 1
2, 13 and the subscriber exchange 14 read the contents of the RM cell (10 Mb / s in this example), and if the exchange and the relay transmission lines 21 to 23 currently in use have a desired band, the resource thereof is allocated. Secure and transfer the RM cell to the next-stage exchange. The RM cell is a virtual path identifier (VP) used by the terminal device 31 which has transmitted it.
By using another field of the header called PTI number in addition to I) and virtual channel identifier (VCI), the route assigned to the terminal device 31 is automatically transferred.

[0005]

FIG. 6 shows the R in each exchange.
The timing chart of M cell handling is shown. Each of the exchanges, that is, each of the subscriber exchanges 11 and 14 and the transit exchanges 12 and 13 needs to access vacant information of resources and the like, so that it takes some time to transfer the RM cell.

FIG. 7 shows an example of time response to a request from a terminal device. When increasing the bandwidth, it takes a response time to check the empty bandwidth of each transit exchange. This is a delay for the request, which is a service problem. Furthermore, the actual network has a long distance and a large number of transit exchange stages. In this case, there is a problem particularly in response time.

SUMMARY OF THE INVENTION It is an object of the present invention to solve the above problems and provide a high speed and flexible bandwidth variable communication device.

[0008]

The variable bandwidth communication device of the present invention is a device that constitutes an ATM network, and the empty band of the connection is known in advance by the subscriber exchange at the time when there is no band change request. The most important feature is that when a user terminal device requests a band change,
It is characterized in that the subscriber exchange accommodating the terminal device grants or denies permission, and when the permission is given, the terminal device changes the band and sends out the cell, and at the same time reserves the band. is there.

That is, a variable bandwidth communication device equipped with a subscriber switch which connects a transmission line for transmitting information of ATM and a terminal device for transmitting information in a band variably set according to the usage status of this transmission line. In the above, the subscriber exchange shall compare the empty band table that stores information on the usage status of the transmission line with the empty band that is stored in the empty band table when there is a band change request from the accommodated terminal device. And means for deciding whether or not to change the band of the terminal device. The subscriber exchange may include means for monitoring the minimum free bandwidth on the route of the connection by periodically transferring an operation maintenance cell to / from another subscriber exchange connected through the transmission line. Good.

This is different from the conventional technique in that the remaining bandwidth is grasped in advance by the subscriber exchange.

[0011]

1 is a block diagram showing a variable band communication apparatus according to an embodiment of the present invention. The device of this embodiment constitutes an ATM network, and relay transmission lines 21 to 23 which form a transmission line for transmitting ATM information, relay exchanges 12 and 13 arranged on this transmission line, and usage conditions of the transmission line. A terminal device 31 that transmits information at a transmission rate that is variably set and a terminal device 32 that receives the information.
And subscriber exchanges 11 and 14 for accommodating the terminal devices 31 and 32 and connecting to the transmission lines, respectively. The subscriber exchange 11 is provided with an empty band table 101 for storing information on the usage status of the transmission path (shown outside the subscriber exchange 11 in the figure), and when there is a band change request from the accommodated terminal device 31. By comparing with the empty band stored in the empty band table 101, it is possible to determine whether or not the band of the terminal device 11 can be changed. The empty band table 101 stores and manages, for each VCI, the empty band of the exchange buffer and the transmission path to which the connection belongs.

FIG. 2 shows an operation timing chart of this embodiment. When the terminal device 31 issues a band change request to the network, the subscriber exchange 11 that accommodates the terminal device 31 receives the request and determines whether or not the request can be made. That is, the subscriber exchange 11 requests the VCI of the request.
Regarding the above, the requested bandwidth is compared with the contents of the empty bandwidth table 101, and if the request is less than the empty bandwidth, the transfer is permitted, and the request exceeding the empty bandwidth is not permitted. When the request permission is returned from the subscriber exchange 11 to the terminal device 31, the terminal device 31 immediately starts the cell transfer. Further, the requested RM cell from the terminal device 31 is transferred as it is to the next-stage exchange, and each transit exchange secures the band.

FIG. 3 shows an empty band check sequence in a normal state where there is no band change request, and FIG. 4 is a repeater exchange 12.
Fig. 3 shows a state of grasping an empty band by. The subscriber exchange 11
A VCI number corresponding to an operation and maintenance cell (hereinafter referred to as "OAM cell") is attached, an empty band is filled in, and the cell is sent to the next stage. Each exchange always keeps track of the corresponding transmission line and other empty bands. This empty band can be obtained based on observation using a low-pass filter, or may be obtained by the sum of peaks at the time of declaration. In the example shown in FIG. 3, the repeater exchange 12 transfers the OAM cell as it is to the next stage because its own empty band is larger than the band described in the transmitted OAM cell. In addition, the relay exchange 13
Since the band 20 Mb / s less than the band 30 Mb / s described in the AM cell is available, the content of the OAM cell is rewritten. In this way, the minimum empty band in the relay exchanges 12 and 13, the relay transmission lines 21 to 23 and the terminating side subscriber exchange 14 is described in the folded cell, and the minimum free band in the originating side subscriber exchange 11 You can figure it out.

[0014] Such an empty band check is carried out periodically to grasp how many Mb / s the VCI band can be variably increased in the subscriber exchange 11 at all times.

[0015]

As described above, according to the present invention, the empty band of the exchange buffer to which each connection belongs and the empty band of the transmission line are stored in advance in the empty band table provided in the subscriber exchange, and the band change request is sent from the terminal device. If there is, the subscriber exchange determines whether or not the change is possible by comparing it with the value stored in the empty band table, and dynamically changes the band based on the requested band from the terminal device. Therefore, the band can be changed at high speed.

[Brief description of the drawings]

FIG. 1 is a block configuration diagram showing a variable band communication device according to an embodiment of the present invention.

FIG. 2 is an operation timing chart.

FIG. 3 is a diagram showing an empty band check sequence.

FIG. 4 is a diagram for explaining the grasp of an empty band by a transit exchange.

FIG. 5 is a block diagram showing a conventional variable bandwidth communication device.

FIG. 6 is a timing chart of RM cell handling in each exchange.

FIG. 7 is a diagram showing an example of a time response to a request from a terminal device.

[Explanation of symbols]

 11, 14 Subscriber switch 12, 13 Relay switch 21-23 Transmission line 31, 32 Terminal device 101 Empty band table

Claims (2)

[Claims] 1. A variable bandwidth comprising a subscriber switch for connecting a transmission line for transmitting information in an asynchronous transfer mode and a terminal device for transmitting information in a band which is variably set according to the usage status of the transmission line. In the communication device, the subscriber exchange stores an empty band table that stores information about the usage status of the transmission path, and an empty band table that is stored in the empty band table when a accommodated terminal device requests a band change. A variable bandwidth communication device, comprising means for determining whether or not the bandwidth of the terminal device can be changed by comparing with the bandwidth. 2. The subscriber switching system periodically transfers an operation and maintenance cell with another subscriber switching system connected via the transmission line to thereby set a minimum empty band on the route of the connection. 2. The bandwidth variable communication device according to claim 1, further comprising monitoring means.