JP2000316009A - Method for assigning idle cell with priority in atm-m bus system and branching device used for this method - Google Patents

Abstract

PROBLEM TO BE SOLVED: To ensure communication quality by eliminating a delay of data and its fluctuation where real time performance is a requirement for a voice communication or the like on a congested ATM-M bus. SOLUTION: The method is an assignment control method of idle cells with priority in an ATM-M bus system where a plurality of branching devices 30 are connected in cascade to an M bus 20 in which an outgoing bus 21 connected to an ATM master unit is looped back at a loopback section 32 of a downstream of a branching device 30-2 at the remotest end and becomes an incoming bus 22. Information denoting whether a terminal requires assignment of an idle cell with priority or a terminal which does not require the priority assignment of the idle cell is set to contents of an 'AAL parameter' information element in a 'setup message' that is sent from a terminal 50 contained in a branching device 30 to the ATM master unit (MBU 12) in the case of call transmission, and the MBU 12 assigns a cell 42 specifying a destination of use to a branching device 30-1 holding a terminal 50-1 requiring assignment with priority and transmits it to the branching device 30-1.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention relates to an ATM connected to an ATM main unit.
An ATM multiplexer having a plurality of branching devices connected in cascade to an ATM-M bus through which M cells are transmitted and having a downstream bus turned back downstream of the branching device located farthest from the ATM main unit and connected to an upstream bus. Bus (ATM-M bus)
The present invention relates to a method and apparatus for ensuring communication quality of a cell requiring real time in a system.

[0002]

2. Description of the Related Art Applicants are connected to an ATM main unit and connected to an ATM.
It has a plurality of branching devices connected in cascade to two ATM buses through which M cells are transmitted, and has a downstream bus turned back downstream of the branching device located farthest from the ATM main unit and connected to an upstream bus. A bus system called an ATM-U bus system (Japanese Patent Laid-Open No. 10-210045, etc.) has been proposed. Hereinafter, this bus system is referred to as an ATM-M bus system.

[0003] By the way, NNI (Network Node Interface)
ce) contains the GFC (Generic Flow Control) of the ATM cell.
l: General flow control; 4 bit) is not specified. Therefore, the GFC of the ATM cell is a field that is not used as an end-to-end function but is used only for a UNI (User Network Interface) part.

In the ATM-M bus system, branching devices are connected in tandem as one of the interfaces on the extension side, and only 4 bits of the GFC are allocated as IDs (identifiers) of each branching device only between the branching devices (M bus section). A plurality of terminals accommodated in the branching device are identified by VP (Virtual Path).

[0005] In this ATM-M bus system, an ATM main unit has destination information (ID control information) in a header.
The TM cell is sent out on the down bus. The branching device refers to the header, fetches the information carried in the payload from the cell having the ID addressed to itself, and then sends the empty cell with the destination blank to the downstream side. An empty cell flowing on the downstream bus is turned back at a turning section provided downstream of the branching device at the farthest end, and is transferred toward the main device on the upstream bus.

Hereinafter, the configuration of the ATM-M bus system will be described with reference to FIG. ATM-M bus system
An ATM main unit 10, an ATM bus 20, and a plurality of branching devices 30-1 to 30- connected in cascade to the ATM bus 20.
4 and the terminal 50 (51
To 55).

The ATM main unit 10 has an ATM switch (A
TM-SW) 11 and M-GF accommodated in the switch
A multi-bus interface unit (hereinafter, referred to as MBU) 12 having a C control function, a 25 Mbps interface unit (25MU) 13, a LAN interface unit (LANU) 14, and an N-ISDN basic interface unit (BCO) connected to INS64.
U) 15, a 25 Mbps inter-node interface unit (25 MNU) 16 connected to another node, a three-way conference unit (CNFU) 17, a voice call type conversion unit (VTU) 18, and a central control unit (CC).
U) 19 and the like.

The ATM-M bus 20 is formed using, for example, a twisted copper wire (UTP5) or an optical fiber cable. The ATM-M bus 20 includes a down bus 21 for sending out ATM cells 40 from the ATM main unit 10 and an up bus 22 for sending out ATM cells 40 to the ATM main unit 10. The downstream bus 21 is connected to the farthest end branching device 30.
-4, and is connected to the upstream bus 22 at a return portion 23 provided on the downstream side.

[0009] The branching device 30 is provided with an M
A dedicated terminal and a general-purpose ATM terminal (for example,
To accommodate 6 ports of 25 Mbps ATM-UNI (terminal interface) to which terminals 50 such as ATM terminal 51, ISDN telephone 52, analog telephone 53, ATM key telephone (ATM-KT) 54, and key telephone existing interface 55) can be connected. It is configured. A maximum of 14 branch devices 30 are connected in cascade to the MBU 12 to form an M bus. The branching device 30 uses, for example, UTP5 as a connection medium on the bus side and UTP3 as a connection medium on the terminal side.
Use

The branching device 30 obtains and manages the VPI / VCI of the user cell for the branching device by signaling,
It has a GFC control for the corresponding user cell, traffic control and monitoring for each terminal port, a fault monitoring function for the M bus and terminal ports, and the like.

The MBU 12 mounted on the ATM main unit 10
Is a unit for controlling the 155 Mbps ATM-M bus 20, and a maximum of three units can be mounted on the ATM main unit 10.

The MBU 12 has an M bus interface (UTP5) function using a 155 Mbps user network interface (UNI) and a general flow control (GF).
C) M-GFC control (general flow control used only within the M bus: management of the M bus) function for managing the flow of the M bus by using the address conversion of ATM cells and ATM-S
A routing function for inserting and removing switching tags for W,
It has an M bus fault monitoring function for monitoring faults on the M bus.

Here, M of the ATM-M bus system is used.
A GFC control (hereinafter, referred to as M-GFC control) protocol used in the bus will be described. The M-GFC control protocol is a bus control protocol realized by hardware (partially software) of the MBU 12 and the branching device 30. Preconditions for realizing the M-GFC control are shown below.

The ID of the branching device 30 is determined by automatic ID allocation performed by the MBU 12.

AT on M bus 20 in branching device 30
The reception of the M cell is taken only from the down bus 21 and the AT
The transmission of the M cell can be set to an empty cell of either the down bus 21 or the up bus 22. However, A
When transmitting a TM cell, an empty cell detected on the upstream bus 22 is used preferentially.

The upper 4 bits of the VP of the ATM cell header are defined as a transmission ID, the lower 4 bits are defined as a port ID (Port ID), the transmission ID specifies the branching device 30, and the port ID indicates the terminal port number of the branching device 30 ( Port number is specified by 1-6).

The MBU 12 in the ATM main unit 10 and the ATM
The GFC / VP / VC of the cell flowing between the SW 11 and between the branching device 30 and the terminal 50 is composed of “0/0 / VC”. (GFC / VP is used only on the M bus 20)

The types of ATM cells managed on the M bus 20 are defined as shown in Table 1 using GFC / VP / VC.

[0019]

[Table 1]

A specific configuration of the MBU 12 will be described with reference to FIG. The MBU 12 includes an M bus loopback control unit 120 and a down bus GFC / VP / VC conversion unit (A
TC♯1) 121-1, GFC / VP / V for upstream bus
C conversion means (ATC # 2) 121-2, AAL5 processing unit 122, M-GFC control / branch device control / tag space control means 1231 to 1235 mounted on PLD
155 Mbps ATM user network interface unit (ATM-UNI) 124, UTP5 interface 125, SOS-GFC recognition means 126
, CPU 127, F-ROM 1281, RAM 1
282.

The M-GFC control / branch device control / tag space control 123 includes a tag space deletion unit 1231, an M-GFC control unit 1232 for a downlink bus, and a GF
C controller 1233 and M-GFC controller for upstream bus 12
34 and a tag space insertion section 1235.

Next, the MBU protocol will be described. The MBU has a "routing table" consisting of an upstream routing table and a downstream routing table.
Is formed. GFC / VP / for downlink bus of MBU12
A conversion table including a downstream routing table is formed in the VC conversion unit (ATC # 1) 121-1.
GFC / VP / VC conversion means for upstream bus (ATC # 2)
121-2, a conversion table including an uplink routing table is formed. The downlink routing table is a table for mutually converting GFC / VP / VC for ATM switch management into GFC (ID) / VP / VC of a call in communication on the M bus. The upstream routing table contains the GFC (ID) / VP / V of the call during communication on the M bus.
6 is a table for mutually converting C into ATM switch management GFC / VP / VC.

These routing tables are managed on the basis of data determined by the CCU with the maximum number of connections (1024) on the M bus 20. Further, these routing tables insert and remove switching tags for ATM switch replacement.

The basic conversion rules and conversion methods using the routing table in the GFC / VP / VC control means 121 are shown in Table 2 and FIG.
A description will be given using the / VC control means (ATC # 2) 121-2. Table 2 (A) shows the conversion on the shared channel for signaling cells, OAM cells and SNMP cells, Table 2 (B) shows the conversion on the user channel for user cells, and Table 2 (C) shows the content of conversion on the user channel for the multicast cell.

[0025]

[Table 2]

As shown in Table 2 (A), in the shared channel for signaling cells, OAM cells, and SNMP cells, GFC / VP
/ VC, the “branch device ID” of the cell on the M bus 22
/ VPI / VCI ”indicating the transmission ID and the port ID
"0 (fixed) /" of the cell between BU12 and ATM-SW11
CPI management VPI (usually "0") / CCU management VC
I ”. On the other hand, in the downstream direction, GFC / VP /
Regarding VC, "0 (fixed) / CCU management VPI (usually" 0 ") / cell of ATM-SW11 → MBU12
The “CCU management VCI” is changed to “VPI / VC indicating“ branch device ID / transmission ID and port ID ”of a downlink cell on the M bus 21.
I ". This routing table is written as initial data when the system is started.

As shown in Table 2 (B), in the user channel for the user cell, G
Regarding FC / VP / VC, the “branch device ID / transmission ID and port I of the cell on the M bus 22”
VPI / VCI indicating D is changed from MBU12 to ATM-S
"0 (fixed) / CCU management VPI of cell between W11
(Usually "0") / CCU management VCI ". On the other hand, in the downlink direction, the GFC / VP / VC
“0 (fixed) / C of cell between M-SW11 → MBU12
CU management VPI (usually "0") / CCU management VC
I "is converted into" VPI / VCI indicating the branch device ID / transmission ID and port ID "of the downstream cell on the M bus 21.

As shown in Table 2 (C), in a user channel intended for a multicast cell, there is no target cell in the uplink direction, and G
ATM / SW11 → MBU for FC / VP / VC
"0 (fixed) / CCU management VPI (usually" 0 ") / CCU management VCI" of the cell between the Twelve 12 cells is "15 / VPI / VC indicating the transmission ID and port ID of the cell on the M bus 21".
I ".

The operation of the GFC / VP / VC conversion means (ATC) 121 provided in the MBU 12 will be described with reference to FIG. Here, the 53-byte ATM cell input from the upstream bus 22 is transmitted to the ATM-SW 11.
Upstream bus GFC / V that converts to 6-byte ATM cells
The P / VC conversion means (ATC # 2) 121-2 is taken as an example.

GFC / VP / VC conversion means 1 for upstream bus
At 21-2, GFC / VP / VC is read from the 53-byte ATM cell 40 input from the M bus 20,
The GFC / VP / VC / switching tag for the output cell obtained by referring to the conversion table (# 2) 121T2 is set in the input cell and the ATM-S is output as a 56-byte output cell.
Transmitted to W11. The input cell has the tag space inserted by the tag space insertion unit 1235.

GFC / VP / VC conversion means 1 for downlink bus
The operation of converting the 56-byte ATM cell from the ATM-SW 11 into the 53-byte ATM cell 40 in 21-1 is performed in substantially the same manner as described above. ATM cell 40
Is sent to the M bus 20.

Hereinafter, the branching device 30 will be described. The branching device 30 has a relay function of reproducing a cell received from the upstream node and transmitting the cell to the downstream node, a function of monitoring the ID (GFC) of a cell flowing on the upstream / downstream bus and capturing a cell addressed to itself, and a terminal using VP. Cell distribution function and ID
A function of transmitting a cell to which (GFC) and VP are added is provided.

The structure of the branching device 30 will be described with reference to FIG. The branching device 30 includes a cell dropping / inserting control unit 31, a cell distribution / multiplexing control unit 32, an ATM user network interface (UNI) 33, and a pulse transformer 3.
4, CPU 35, F-ROM 361, RAM 36
2 and a display unit 37.

The cell add / drop controller 31 refers to the GFC of the ATM cell 40 flowing on the downstream bus 21 of the M bus 20 to branch and take in the ATM cell addressed to itself, and also performs the upstream bus 22 or the downstream bus 22. When an empty cell is found on the bus 21, the ATM cell has a function of loading data and management data from a subordinate terminal into the ATM cell and sending it to the ATM main unit 10.

The cell distribution multiplexing control section 32
It has a function of distributing to the port to which the destination terminal is connected with reference to the VP of the TM cell, and a function of multiplexing data transmitted from the terminal under the control and transmitting the multiplexed data to the cell add / drop controller 31.

The ATM-UNI 33 is connected to the M bus 2 on the upstream side.
155 Mbps upstream A interface with 0
155 Mbps downstream ATM-UNI3 that interfaces TM-UNI33-U with the downstream Mbus
25Mb interfacing 3-D with terminal 50
Terminal-side ATM-UNI33-T with 6 ps ports
There is.

The terminal-side ATM-UNI 33T distributes the ATM cells distributed from the cell distribution multiplexing control unit 32 to the terminal-side pulse transformer 34T connected to each port.

The pulse transformer 34 is connected to the M bus 2 on the upstream side.
0 and a downstream pulse transformer 34-D connected to the M bus on the downstream side.
And six terminal-side pulse transformers 34-T1 to 34-T6 connected to the terminal 50.

The CPU 35 integrates and controls each functional part in the branching device 30.

The F-ROM 361 and the RAM 362 store programs and data necessary for controlling the branching device 30 and the like.

The display unit 37 is composed of LEDs, and displays the operating state of the branching device 30.

The branching device 30 has the following hardware operation outline. The branching device 30 has a function of monitoring cells received on the downstream bus 21 from the upstream node and taking in a cell having an ID addressed to itself (hereinafter, referred to as own ID cell). Further, the branching device 30 has a function of relaying cells other than the own ID cell to the downstream bus 21 to the downstream node as it is. The branching device 30 takes in its own ID cell, determines the terminal port with reference to the VP, and sets the GFC / V
P is cleared to "0", converted to a UNI format, and stored in the corresponding port-addressed transmission buffer.

The branching device 30 determines that the cell received on the down bus 21 from the upstream node is a multicast cell (GFC
= 15), relay to the downstream node as it is,
To multicast to all ports of the branching device 30,
GFC / VP is cleared to "0" and stored in all port-addressed buffers (cell copy).

When there is no transmission data from the branching device 30, the branching device 30 sets the GFC,
VP and VC are all changed to “0” and converted into empty cells,
Send to downstream node.

When there is transmission data from the branching device 30, the branching device 30 determines the GFC,
GFC = ID and VP = port number are set in VP and VC, and transmission data is mounted on the payload and transmitted to the downstream node side.

The branching device 30 is configured to be able to transmit transmission data not only to empty cells on the downstream bus 21 from the upstream node but also to empty cells on the upstream bus 22 from the downstream node. If both the downstream bus from the upstream node and the upstream bus from the downstream node have free space, the upstream node is prioritized. When receiving a multicast cell on the upstream bus 22 from a downstream node, the branching device 30 immediately deletes the received multicast cell as being the farthest end branching device and makes it a free cell.

The branching device 30 is provided with a terminal receiving buffer for receiving cells from the terminal for 10 cells. SOS only when the counter value of the terminal reception buffer reaches "3"
The cell is transmitted once, and the counter value of the terminal reception buffer is decremented to “2”. MBU1 which received the SOS cell
In step 2, a “branch device-designated reserved vacant cell” is forcibly generated and transmitted onto the down bus 21. As a result, the zone of the terminal reception buffer of the branching device is eliminated. In addition,
When the SOS cell system is not used, it is necessary to provide a buffer for 18 cells or more.

In such an ATM-M bus system, when data is transmitted from the terminal 50 accommodated in the branching device 30, the ATM cell 40 flowing on the M bus 20 is monitored, and when there is an empty cell. The ATM cell is loaded with data and transmitted. When a vacant cell is needed to send data, the branching device 30
An SOS cell requesting an empty cell is transmitted to the upstream bus 22. Upon receiving the SOS cell, the ATM main unit 10 responds to the request by transmitting an ATM cell specifying the use destination to the branching device.

In such a system, when the M bus 20 is congested, the SOS is
When cells are transmitted, there is a possibility that ATM cells cannot be allocated to terminals that require real-time characteristics such as voice, and delay and fluctuations occur in data from terminals that require real-time characteristics, resulting in poor communication quality. There is a fear of lowering.

[0050]

SUMMARY OF THE INVENTION An object of the present invention is to solve the above problems, and more particularly, to a congested AT.
It is another object of the present invention to secure communication quality on the MM bus 20 by eliminating delays and fluctuations in, for example, voice communication (AAL1) or the like that requires real-time properties.

[0051]

SUMMARY OF THE INVENTION In order to solve the above-mentioned problems, the present invention provides a method in which a priority is given to, for example, voice communication (AAL-1), which requires real-time performance, on an M bus. In addition, the communication quality is ensured by reducing the fluctuation.

According to a first aspect of the present invention, a plurality of branching devices are connected to the M bus connected to the ATM main device, with the down bus connected to the ATM main device being turned back downstream of the furthest branch device to be an up bus. In an ATM-M bus system in which ATMs are connected in tandem, the "AAL parameter" in the "call setup message (Set Up)" sent from the terminal accommodated in the branching device to the ATM main device when transmitting to the ATM main device. "Information indicating whether the priority assignment of an empty cell is required or not is required in the content of the information element. An empty cell whose use destination is specified is allocated and transmitted.

The invention according to claim 2 is the ATM-M according to claim 1.
In the priority assignment method of an empty cell in a bus system, priority assignment is performed for a call setup message whose AAL parameter is AAL1.

According to a third aspect of the present invention, there is provided a method for preferentially assigning an empty cell in the ATM-M bus system according to the first or second aspect.
The use destination was specified in P.

According to a fourth aspect of the present invention, there is provided a branching device for use in a method for preferentially allocating ATM cells in an ATM-M bus system according to any one of the first to third aspects, wherein a cell from a terminal is transmitted. A priority buffer and a non-priority buffer to be temporarily stored, and a priority / description describing whether the terminal connected to the terminal port is a terminal that preferentially transmits cells.
A non-priority control table is provided to distribute cells from the terminal to the priority buffer or the non-priority buffer, and to preferentially transmit the cells stored in the priority buffer to the M bus.

[0056]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS The free cell priority control method of the present invention in an ATM-M bus system will be described below with reference to FIG. In the empty cell control method according to the present invention,
In the above ATM-M bus system, the branching device 30
, A priority buffer 381 and a non-priority buffer 382.
And a priority / non-priority control table, and searches the priority / non-priority control table with reference to the VCI value of the cell received at the terminal port, and stores the received cell as a result in the priority buffer 381 or the non-priority It has a function of sorting to the buffer 382. This priority buffer 381
The non-priority buffer 382 and the priority / non-priority control table are provided in the RAM 362 shown in FIG.

The priority / non-priority control table corresponds to different VCI values (1 to 1023) given to terminals accommodated in the branching device connected to the M bus, and
It describes whether the terminal having the CI value is a terminal that communicates with priority data or a terminal that communicates with non-priority data.

The header of the ATM cell 40 describes an ATM adaptation layer (AAL) parameter information element. This AAL parameter indicates the required end-to-end meaningful AAL parameter value for the AAL procedure used for the call. This includes parameters for all AAL sublayers that can be selected by the user. The contents of this information element are transparent to the net, except in the case of interworking. The maximum length of this information element is 21 octets.

The AAL parameter information element is, for example, 1
Octet information element identifier, 1-bit extension,
2 bit coding standard, 1 bit flag and 1
An information element operation instruction field including a reserved bit and a three-bit information element operation content, and a 2-octet A
It has an Al parameter content length and one octet AAL type.

The AAL type is AAL for voice when "00000000" and AA when "00000001".
L type 1 is AAL type 2 when "0000001", AAL type 3 or AAL type 4 when "00000011", and AA when "00000100".
User defined AAL when L5 is "00010000"
, And reserved at other times.

The setting and cancellation of whether the terminal is a terminal that communicates with priority data or a terminal that communicates with non-priority data as described in the priority / non-priority control table will be described with reference to FIG. FIG. 2A illustrates a priority / non-priority information setting sequence, and FIG. 2B illustrates a set priority / non-priority information release sequence. The above setting is performed for each VCI as follows, for example. When a calling operation is performed at the terminal 50 under the branching device 30, a call setup message (SetUP) describing in an information element whether or not the terminal 50 itself is a terminal for real-time communication is sent to the ATM.
It is sent to the CCU 19 of the main unit (S1).

CCU 19 receiving “Set Up”
Returns "Call Proc" to the terminal 50 (S2).

The CCU 19 analyzes the contents of the information element "Set Up" and assigns whether the data of the terminal is priority data or non-priority data (S3).

The priority / non-priority assignment result is instructed to the MBU 12 with the channel setting command (ch setting COM) (S4).

The MBU 12 receives the “ch setting CO”
The priority / non-priority information is extracted from the “M” and is loaded in the “priority channel request” and the content is instructed to the branching device 30 (S
5).

The branching device 30 sets the priority / non-priority control table (S6). In this way, the priority / non-priority control information of the subordinate terminal is set in the priority / non-priority control table in the branching device 30.

The cancellation of such setting contents can be performed as shown in FIG.
Is performed according to the flow shown in FIG. When the terminal 50 performs the disconnection operation after the communication in a state where the priority data is set is terminated, the terminal 50 issues a “Release” message to the CCU 19 of the ATM main unit.
An e ″ signal is sent (S11).

The CCU 19 issues a channel release command (c
h Open COM) and instruct MBU 12 (S1)
2).

The MBU 12 receives the “ch release CO
From M ″, the branching device 30 is instructed to put the designated channel non-priority on the priority channel request (priority channel request) (S13).

The branching device 30 sets the non-priority of the terminal in the priority / non-priority control table and releases the priority information (S14). In this way, in the priority / non-priority control table in the branching device 30, priority information is set only for the terminal that is communicating and has priority.

At the time of transmission from the terminal 50, the ATM main unit 10
"Call setup message (Set
Based on the content of the “AAL parameter” information element in “Up)”, the CCU 19 of the MBU 12 allocates the data as follows: When the AAL parameter is AAL1, the data is assigned to the priority buffer and the AAL parameter is set to AAL2 to AAL5. In this case, the data is distributed to the non-priority buffer as non-priority data.

When the branching device 30 receives a vacant cell on the down bus 21 or the up bus 22 of the M bus 20, it takes out data from the priority buffer or the non-priority buffer, mounts the data in the vacant cell, and loads the data into the M bus. 20. At this time, the data stored in the priority buffer is mounted on an empty cell, and the data stored in the non-priority buffer can be transmitted to the M bus 20 only when the priority buffer is empty.

By doing so, the branching device 3
On 0, priority data such as audio data stored in the priority buffer can be transmitted onto the M bus 20 without delay.

The ATM-M to which the present invention is applied
In the bus system, a maximum of 14 branching devices 30 can be connected, and they operate asynchronously. So there is one
Even if one branch device preferentially assigns priority data from a subordinate terminal to a vacant cell by the above-described method, the load of a cell assigned non-preferentially by another branch device increases. There is a possibility that the chance of obtaining a cell is reduced and the real-time property is impaired.

The priority / non-priority assignment control with the other branching device 30 will be described below. In such a case, ATM
If the SOS control in the -M bus system is performed only for the data from the priority buffer of each branch device, priority / non-priority assignment control between the branch devices can be performed.

In this control method, the priority of each data on the M bus 20 is as follows. It is also assumed that the cells stored in the priority buffers (hereinafter, referred to as priority cells) have higher priority than the cells stored in the non-priority buffers (hereinafter, referred to as non-priority cells) between the branching devices. The priority cells are the same among the respective branching devices. The non-priority cells are the same between the respective branching devices.

[0086] The ATM-
An example of priority / non-priority assignment control in the M bus system will be described with reference to FIG. Terminal 50-1 is a branching device 3
When communication is being performed from A-1 to AAL1 from the terminal 50-2 under the branching device 30-2, AAL1
It is assumed that AAL5 data in an amount that erodes communication is transmitted using SOS cells. In this case, the transmission data of the priority cell from the branch device 30-1 is blocked by the data from the branch device 30-2 and accumulates in the priority buffer 381-1.

When the accumulated amount of the priority buffer 381-1 in the branching device 30-1 becomes a certain value or more, the branching device 30-1 sends the SOS cell 41 to the MBU 12.

When receiving the SOS cell 41 from the branching device 30-1, the MBU 12 refers to the priority / non-priority control table and, when the SOS cell 41 is the priority data, changes the transmittable cell 42 to the M bus 20. To the downstream bus 21. That is, the transmittable cell 2 is a cell that specifies the branching device 30-2 as the destination and the branching device 30-1 as the branching device that can use the cell. For example, when transmitting the ATM cell 40 addressed to the branching device 30-2, the MBU 12 transmits the transmittable cell 42 specifying the branching device 30-1.

When the branching device 30-1 receives the transmittable cell 42 from the upstream side of the downstream bus 21 and detects that the cell is not its own ID cell by referring to the header, the branching device 30-1 relays the cell to the downstream side as it is.

The branching device 30-2 that has received the transmittable cell 42 from the upstream side of the downstream bus 21 refers to the header and takes in the payload when the cell is its own ID cell.

When the branching device 30-2 refers to the header and detects that the designated branching device is not itself, it clears the destination ID (branching device ID),
The cell from the terminal 50-2 is transmitted to the downstream side as an empty cell without being mounted.

The transmittable cell 42 is turned back at the turn-back portion 23 at the farthest end and flows through the upstream bus 22.

The branching device 30-2, which has received the empty cell (sendable cell) 42 on the downstream side of the upstream bus 22, recognizes that the cell is a sendable cell that cannot be used by itself by referring to the header and, as it is, the upstream side. Relay to

When the branching device 30-1 receives an empty cell (sendable cell) 42 on the downstream side of the upstream bus 22,
It is determined by referring to the header whether the cell is a vacant cell that can be used by itself, and if the cell is a transmittable cell 42 that can be used by itself, the terminal 5 stored in the priority buffer 381-1
The data from 0-1 is loaded and sent out to the MBU 12 on the upstream bus 22.

As described above, the empty cell is preferentially allocated to the priority cell from the branching device 30-1.
0-2 cannot send the SOS cell 41, so that the terminal 50-1 under the control of the branching device 30-1 can perform real-time communication without deteriorating the communication quality. Non-priority cells transmitted from the terminal 50-2 under the control of the branching device 30-2 are accumulated in the non-priority buffer 382-2, and wait for an empty cell on the M bus 20.

In this way, even between a plurality of branching devices,
The priority of the priority cell can be made higher than the non-priority cell, and the transmission of the non-priority cell from the branching device 30-2 can be suppressed, and the priority cell can be transmitted from the branching device 30-1. .

[0088]

As described above, according to the present invention, even on the congested ATM-M bus 20, there is no need to delay and fluctuate, for example, voice communication (AAL1) or the like which requires real-time performance. Quality can be ensured.

[Brief description of the drawings]

FIG. 1 is a diagram illustrating priority assignment of empty cells according to the present invention.

FIG. 2 is a sequence diagram illustrating information setting and canceling of a priority / non-priority control table.

FIG. 3 is a block diagram illustrating an outline of a configuration of an ATM-M bus system to which the present invention is applied;

FIG. 4 is a block diagram illustrating a configuration of an MBU.

FIG. 5 is a flowchart illustrating the operation of a GFC / VP / VC conversion unit.

FIG. 6 is a block diagram illustrating a configuration of a branching device.

[Explanation of symbols]

Reference Signs List 10 ATM main unit 11 ATM switch 12 M bus interface (MBU) 122 M bus loopback control unit 121 GFC / VP / VC conversion unit 122 AAL5 processing unit 123 MGF control / branch control cell transmission / reception / tag space control unit 1231 Tag space deletion Means 1232 M-GFC control means for downlink bus 1233 M-GFC control means for empty cell 1234 M-GFC control means for uplink cell 1235 Tag space insertion means 124 ATM-UNI 125 UTP5 interface 126 SOS-GFC recognition means 127 CPU 1281 F −ROM 1282 RAM 13 25 Mbps interface unit 14 LAN interface unit 15 ISDN basic interface unit 16 25 Mbps interface between nodes Unit 17 Three-way conference unit 18 Voice call type conversion unit 19 Central control unit (CCU) 20 M bus 21 Down bus 22 Up bus 23 Turnback unit 30 Branch device 31 Cell branch / insert control unit 32 Cell distribution / multiplex control unit 33 ATM-UNI 34 pulse transformer 35 CPU 361 F-ROM 362 RAM 37 display unit 40 ATM cell 41 SOS cell 42 transmittable cell 50 terminal 51 ATM terminal 52 ISDN telephone 53 analog telephone 54 ATM button telephone 55 key telephone interface

Continued on the front page (72) Inventor Junji Asakura 3-19-2 Nishi-Shinjuku, Shinjuku-ku, Tokyo F-term (reference) in Nippon Telegraph and Telephone Corporation 5K030 GA02 HA10 HB01 HB09 HB21 HC15 JA01 JL08 KA03 KA04 LB02 LC06 LE05 5K031 AA03 BA05 BA06 CB01 DA02 DA05 DB03

Claims (4)

[Claims] 1. A downstream bus connected to an ATM main unit is turned back downstream of a farthest branch device to become an upstream bus, and
In a method of preferentially allocating an empty cell in an ATM-M bus system in which a plurality of branching devices are cascade-connected to an M bus connected to a TM main unit, a message sent when a terminal accommodated in the branching unit transmits a signal to the ATM main unit is transmitted. A call setting message (SetUp) "includes information indicating whether priority allocation of empty cells is required or not in the content of the" AAL parameter "information element. A method for preferentially allocating an empty cell in an ATM-M bus system, wherein an empty cell whose use is specified is allocated and transmitted to a branch device accommodating a terminal that desires priority allocation. 2. The method according to claim 1, wherein priority is assigned to a call setup message whose AAL parameter is AAL1. 3. The cell whose use is specified is identified by a VP in the header.
3. A method according to claim 1, wherein a use destination is designated in the ATM-M bus system. 4. A branching device for use in a method for preferentially allocating ATM cells in an ATM-M bus system according to any one of claims 1 to 3, wherein the branching device temporarily stores cells from a terminal. A buffer and a non-priority buffer, and a priority / non-priority control table that describes whether the terminal connected to the terminal port is a terminal that sends cells preferentially, and stores cells from the terminal in the priority buffer or non-priority control table. A branching device that distributes cells stored in the priority buffer to the M bus while distributing the cells to the priority buffer.