JP3085515B2 - Bandwidth variable communication device - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention is used for information transfer in an asynchronous transfer mode (hereinafter referred to as "ATM"). In particular, the present invention relates to a dynamic bandwidth change type communication network capable of changing the bandwidth 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) is 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 has recently been receiving attention. In the ABR type service, each user can control its own cell transmission rate based on the ABR protocol, and operates so as to decrease the cell transmission rate when the network is congested and to increase the cell transmission rate when the network is free. . ABR technology is being standardized by the ATM Forum and the ITU-TS (Telecommunication Standardization Sector), respectively.

FIG. 5 shows an ATM providing an ABR type service.
FIG. 3 is a block diagram illustrating a conventional band variable communication device that forms a network. In this example, two local exchanges 11 and 14 are connected via a transit transmission line 21, a transit exchange 12, a transit transmission line 22, a transit exchange 13 and a transit transmission line 23. 3
1. The subscriber exchange 14 accommodates a terminal device 32.
The local 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 execute a “virtual channel handler (VC)”.
H) ".

[0004] When it is desired to transfer information such as a file transfer, the terminal devices 31 and 32 send a resource management cell (RM cell) to the network and desire to change the band. Subscriber exchange 11, relay exchange 1
2, 13 and the local exchange 14 read the contents of the RM cell (10 Mb / s in this example), and if there is a desired band in the currently used exchange and the relay transmission lines 21 to 23, the resources thereof are allocated. The RM cell is secured and the RM cell is transferred to the next exchange. The RM cell is a virtual path identifier (VP) used by the terminal device 31 that has transmitted the RM cell.
By using another field of the header called a PTI number in addition to I) and the virtual channel identifier (VCI), the route assigned to the terminal device 31 is automatically transferred.

[0005]

FIG. 6 shows the R in each exchange.
4 shows a timing chart of handling of an M cell. Each of the exchanges, that is, each of the local exchanges 11 and 14 and the transit exchanges 12 and 13 needs to access the vacant information of the resources and the like, so that a certain amount of time is required for the transfer of the RM cell.

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

An object of the present invention is to solve such problems and to provide a high-speed and flexible band variable communication device.

[0008]

SUMMARY OF THE INVENTION A variable bandwidth communication apparatus according to the present invention is an apparatus constituting an ATM network, and it is known that an available bandwidth of a connection is previously grasped by a local exchange at a time when there is no bandwidth change request. The most important feature is that when a user terminal device requests a bandwidth change,
Permission or non-permission is given by the subscriber exchange accommodating the terminal device, and when permission is given, the terminal device changes the band and sends out cells, and at the same time, reserves the band. is there.

More specifically, a variable-bandwidth communication apparatus having a subscriber exchange for connecting a transmission line for transmitting information of an ATM and a terminal device for transmitting information in a band variably set according to the use condition of this transmission line. In the above, the subscriber exchange compares the available bandwidth table storing information on the use status of the transmission path with the available bandwidth stored in the available bandwidth table when a bandwidth change request is received from the accommodated terminal device. Means for determining whether or not the terminal device can change the band. The local exchange may include means for monitoring the minimum available bandwidth on the route of the connection by periodically transferring operation and maintenance cells to and from another local exchange connected via the transmission line. Good.

The difference from the prior art is that the remainder of the band is grasped in advance by the local exchange.

[0011]

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

FIG. 2 shows an operation timing chart of this embodiment. When the terminal device 31 issues a bandwidth change request to the network, the local exchange 11 accommodating the terminal device 31 receives the request and determines whether the request can be made. That is, the local exchange 11 transmits the VCI of the request.
, 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 local exchange 11 to the terminal device 31, the terminal device 31 immediately starts cell transfer. Further, the requested RM cell from the terminal device 31 is transferred as it is to the next-stage switch, and each relay switch secures a band.

FIG. 3 shows an empty band check sequence in a normal state without a band change request, and FIG.
This shows the state of grasping the empty band by using. The local exchange 11
A VCI number corresponding to an operation and maintenance cell (Operation and Maintenance Cell, hereinafter referred to as an “OAM cell”) is attached, and the own band is entered and transmitted to the next stage. Each exchange always knows the corresponding transmission path and other available bands. This empty band can be obtained based on observation using a low-pass filter, or may be obtained from the sum of peaks at the time of declaration. In the example shown in FIG. 3, the transit exchange 12 has its free band larger than the band described in the transmitted OAM cell, and thus transfers the OAM cell to the next stage as it is. In addition, the relay exchange 13
Since only the band 20 Mb / s less than the band 30 Mb / s described in the AM cell is free, the content of the OAM cell is rewritten. In this way, the returned cell describes the minimum vacant band in the transit exchanges 12 and 13, the transit transmission lines 21 to 23, and the destination local exchange 14, which is then transmitted to the originating local exchange 11. You can figure out.

Such a free band check is periodically performed, and the local exchange 11 constantly grasps how many Mb / s the VCI band can be variably increased.

[0015]

As described above, according to the present invention, the exchange buffer to which each connection belongs and the empty band of the transmission line are stored in advance in an empty band table provided in the subscriber exchange, and the terminal device requests the band change. In the case where there is an error, the local exchange determines whether or not the change is possible by comparing the value with the value stored in the empty band table, and dynamically changes the band based on the requested band from the terminal device. Therefore, high-speed band change is possible.

[Brief description of the drawings]

FIG. 1 is a block 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 how an intermediate exchange recognizes an empty band.

FIG. 5 is a block diagram showing a conventional band variable 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 local exchange 12, 13 transit exchange 21 to 23 transmission line 31, 32 terminal device 101 idle band table

────────────────────────────────────────────────── ─── Continuation of the front page (56) References JP-A-7-231322 (JP, A) JP-A-5-183579 (JP, A) JP-A-5-268240 (JP, A) European Patent Application Publication 635958 (EP, A2) 1995 IEICE Communications Society Conference B-345 (August 15, 1995) (58) Fields studied (Int. Cl. ⁷ , DB name) H04L 12/28 H04L 12 / 56

Claims (2)

(57) [Claims] 1. A band variable switch comprising a subscriber exchange for connecting a transmission line for transmitting information in an asynchronous transfer mode and a terminal device for transmitting information in a band variably set in accordance with the use condition of the transmission line. In the communication device, the local exchange has an empty band table that stores information on the use state of the transmission line, and when there is a band change request by a resource management cell from an accommodated terminal device, the empty band table By comparing with the stored empty band, it is possible to immediately determine whether the terminal device can change the band.
And return the result to the terminal device.
If applicable, apply the resource management cell.
On the communication route to secure resources on the transmission path
And a transfer unit. 2. The local exchange of the subscriber exchange and a subscriber exchange of a destination.
Comprising one or more transit exchanges on the transmission path between the machine, the transit exchange is transferred resource management
When the current empty band is smaller than the band described in the cell
Overwrites the value and transfers it to the next stage.
Means for transferring the packet to the next stage as it is, wherein the local exchange monitors the minimum vacant band on the route of the connection by periodically transferring an operation / maintenance cell with the destination local exchange. 2. The variable bandwidth communication device according to claim 1, further comprising means.