JP2828079B2 - RM cell management system - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention relates to an ABR (Ava)
Regarding rate control between end terminals, which is congestion control of the service class (i.e., Bit Rate), in particular, multipoint-to-point (Multi-point-to-point) in which connections from a plurality of destinations are converged to a single destination.
Resource Management (RM) in a point-to-point (ATM) connection
nt) The present invention relates to an RM cell management system that performs cell transfer.

[0002]

2. Description of the Related Art When an ABR class ATM connection is established between user terminals, a data transmitting terminal periodically transmits an RM cell to a data receiving terminal by mixing it with normal data cells.

[0003] The data receiving terminal returns the received RM cell to the data transmitting terminal. An RM cell may be newly created by a data transmission terminal or an ATM switch. The network writes necessary congestion information in the RM cell while being returned to the data transmitting terminal, and the data transmitting terminal that receives it writes the transmission rate ACR (Allowed Cell Rat) based on the information.
e) is adjusted adaptively.

[0004] ATM, which is a deliberation group on ATM communication
FIG. 21 shows the format of the RM cell defined by the forum.

[0005] The first five bytes of the format are P
TI (Payload TypeIdentify)
r) = 110 standard ATM cell header. P
TI = 110 indicates that the cell is an RM cell.

[0006] RM Protocol Identif
ier indicates the identification of the service using the RM cell.
“1” is assigned to the ABR.

[0007] The Message Type includes a DIR element, a BN element, a CI element, a NI element, and an RA element. Each element consists of one bit.

[0008] The DIR element indicates the direction in which the RM cell is flowing. If it is flowing in the same direction as the data cell, "0" is assigned.
The M cells are called forward RM cells. "1" if reversed
, And this direction is called a backward direction, and the RM cell is called a backward RM cell. The data receiving terminal that receives the forward RM cell changes the DIR element to “1” and then replies to the data transmitting terminal.

[0009] The BN element indicates who created the RM cell. “0” indicates that the data is transmitted by the data transmitting terminal, and “1” indicates that the data is transmitted by the data receiving terminal or switch.

[0010] The CI element is used to notify a terminal of the presence of network congestion. When the switch detects congestion,
Alternatively, if the data receiving terminal is an EFCI (Explicit
Forward Congestion Indic
The CI is set when a data cell whose bit is set to “1” has been received so far. If the CI of the received backward RM cell is “1”, the data transmitting terminal must reduce the transmission rate.

[0011] The NI element is used to prevent a data transmitting terminal from increasing its transmission rate. If the NI of the received backward RM cell is "1", the data transmitting terminal does not increase the transmission rate.

The RA element is an area not used by the ATM Forum. Res. Is a spare area.

[0013] The ER is initially set by a data transmission terminal to a maximum transmission rate PCR (Peak Cell Rate).
Is described and flows in the forward direction, but the rate is reduced to a rate permitted by each ATM exchange by a switch on the connection while being returned in the backward direction.

The CCR describes the transmission rate of the data transmitting terminal when the RM cell was transmitted.

The MCR is the minimum transmission rate MCR (Mimi) set for the connection through which the RM cell flows.
mum Cell Rate) is described.

QL and SN are areas not used by the ATM Forum.

Each ATM exchange on the ATM connection manages resources such as whether the backward RM cell passing therethrough is congested and the transfer rate ER (Explicit Rate) that can be transmitted on the ATM exchange. Update information.

Specifically, if it is determined that there is congestion, the CI bit is set to "1". If a function for calculating ER is provided, the smaller value is selected from the result calculated by itself and the value already written in the backward RM cell, and the smaller value is selected in the backward RM cell. Record.

In a multipoint-to-point ATM connection with N data transmitting terminals and one data receiving terminal, the forward R transmitted from each transmitting terminal is used.
The M cells are collected at the ATM switch located at the convergence point of the connection, and all of them are transmitted to one data receiving terminal.

In the conventional RM cell management system, when a backward RM cell from one data receiving terminal arrives at an ATM switch located at the convergence point of a connection, the ATM switch determines which data transmission is performed by the backward RM cell. Since it is not known whether the reply of the forward RM cell transmitted from the terminal is made or not, the data is copied only for all data transmitting terminals and transferred.

[0021]

In the above-described conventional method, the ATM switch located at the convergence point of the connection uses the backward RM cell returned by following the downstream connection from the ATM switch to the data receiving terminal. Forward RM transmitted from any data transmission terminal
In order not to know whether a cell is returned or not, it is necessary to distribute incoming backward RM cells to each data transmitting terminal and return the same, but return exactly the same amount of backward RM cells to all transmitting terminals. Will be.

AT located at convergence point from data transmission terminal
Forward R between each upstream connection to the M exchange
If there is a variation in the transmission amount of M cells, the backward R according to the transmission amount of each forward RM cell
Unless the M cell is returned, rate control between end terminals by the RM cell does not work well.

For example, while the data transmission is suspended and no forward RM cell is transmitted, the backward RM cell is not transmitted.
When the cells are returned and the ACR is getting too large when trying to resume data transmission, it may cause new congestion.

[0024] Further, since all of the backward RM cells to be distributed and returned to each data transmitting terminal are commonly transferred to each data transmitting terminal, over control by receiving a large amount of backward RM cells causes network overload. The congestion state cannot be stabilized.

An object of the present invention is to provide a multipoint-to-
In a point-type ATM connection, an ATM switch located at a convergence point of the connection returns a backward RM cell describing meaningful resource management information according to the forward RM cell arrival amount of each upstream connection, and It is an object of the present invention to provide an RM cell management system capable of performing a rate control immediately according to a state change.

[0026]

According to a first aspect of the present invention, when a forward RM cell arrives at an ATM switch located at a convergence point of a connection, a forward RM cell from an upstream connection is transmitted from the upstream RM cell. A flag was set to indicate cell arrival. This flag is prepared for each upstream connection in the ATM exchange.

When the backward RM cell arrives at the ATM switch located at the convergence point from the convergence downstream, the ATM switch located at the convergence point transfers the backward RM cell to all the upstream connections for which the flag is set. Duplicate and forward to upstream connection. Or,
The upstream connection for transferring the backward RM cell is selected by the rotation priority control between the upstream connections where the flag is set.

The rotation priority control is a method of receiving services equally in a predetermined order. When a service having a priority is received, the operation of transferring the priority to the next one is repeated in a fixed order. .

In the second invention, the forward RM
The counter is incremented when the cell arrives at the ATM switch located at the convergence point, and the counter is decremented when the backward RM cell is transferred toward the upstream connection, for each upstream connection.

When the backward RM cell arrives at the ATM switch located at the convergence point from the downstream of the convergence point, the ATM switch located at the convergence point transfers the backward RM cell to all the upstream connections whose counter value is not zero. Duplicate and forward to upstream connection. Alternatively, the upstream connection for transferring the backward RM cell is selected by the rotation priority control between the upstream connections whose counter value is not zero.

In the third invention, each time a backward RM cell arrives at an ATM switch located at a convergence point from a convergence destination downstream, the backward RM cell is sent to the ATM switch.
The resource management information described in the cell is collected, and the RM cell is discarded only by updating the stored resource management information.

A located at the convergence point from the upstream connection
When the forward RM cell arrives at the TM exchange, its AT is determined based on the accumulated resource management information.
The M exchange normally creates a new backward RM cell that is exactly the same as that returned from the data receiving terminal, and transfers the newly created backward RM to the corresponding upstream connection.

[0033]

FIG. 1 shows an example of the configuration of a multipoint-to-point ATM connection. The number of transmitting terminals is five in total, and five upstream connections are converged to one in the ATM switch # 1. The upstream connection from the transmission terminal # 1 to the ATM switch # 1 is defined as an upstream connection # 1, and the same applies to other upstream connections. The present invention can be applied to a multipoint-to-point ATM connection having any configuration.

Each ATM exchange calculates the ER that can be transmitted on the output link, compares it with the ER described in the backward RM cell sent from the data receiving terminal, and compares the ER described in the backward RM cell. If the ER is smaller than the ER that can be transmitted by the ATM switch, the backward RM cell is transferred to the data transmitting terminal without changing the ER.

If the ER described in the backward RM cell is larger than the ER that can be transmitted by the ATM switch, the ER of the backward RM cell is rewritten to the ER that can be transmitted by the ATM switch, and the backward RM is written. The cell is transferred to the data transmission terminal.

When each ATM exchange detects congestion on an output link, when a backward RM cell, which is a reply of a forward RM cell passing through the output link, arrives, the CI bit is set and the backward RM cell is set. The cell is transferred to the data transmission terminal.

FIG. 21 shows the format of an RM cell defined by the ATM Forum, which is a deliberative body for ATM communication. As described in the related art, the structure is such that resource information such as a transferable rate can be described.

An embodiment of the first invention will be described with reference to FIGS.

In the embodiment of the first invention, each ATM exchange has a flag indicating that a forward RM cell has arrived for each upstream connection. Where A
If no flags are set when a backward RM cell arrives, the TM switch operates to save the smallest of the ERs of the continuously arriving backward RM cells. Similarly, it operates to store the logical sum of the CI bits of the arriving backward RM cells.

FIG. 1 shows the case where the flag is not set (Fl
ag = "0") when the forward RM cell 20 arrives at the ATM switch # 1 from the upstream connection # 1. Arrows indicate the direction in which the data cells flow.

At this time, in the embodiment shown in FIG.
The exchange # 1 sets the flag of the upstream connection # 1 (Flag = "1"), and the forward RM cell 20
To the convergence destination (ATM exchange # 2).

FIG. 3 shows a case where no flag is set in any upstream connection (Flag = "0").
The backward RM cell 30 is transmitted from the receiving terminal side to the ATM.
This is the state when the vehicle has arrived at the exchange # 1.

At this time, in the embodiment shown in FIG.
Exchange # 1 discards the arriving backward RM cell 30 without forwarding it anywhere.

FIG. 5 shows a flag standing (Flag =
“1”) upstream connection (upstream connection # 1, #
3, # 5) when the backward RM cell 30 from the receiving terminal arrives at the ATM exchange # 1.

At this time, in the embodiment shown in FIG.
The exchange # 1 compares the resource management information described in the arriving backward RM cell 30 with the resource management information stored by itself and updates the resource management information in the arriving backward RM cell 30. Standing upstream connections (upstream connections # 1, # 3, #
After copying and transferring the backward RM cell 30 by the amount of 5), the flag is lowered (Flag = "0").

Here, the ATM switch # 1 rewrites the smallest value among the ER calculated by itself, the stored ER, and the ER described in the backward RM cell 30, in the backward RM cell 30, Transfer to upstream destination. When the ATM switch # 1 is congested or when the stored CI information is “1”, the CI bit of the backward RM cell 30 is set and transferred to the upstream destination. After transferring the backward RM cell 30 to the upstream destination, the ATM switch # 1 resets the stored minimum ER to PCR and resets the CI information to "0".

FIG. 7 shows that a flag is set (Flag =
“1”) upstream connection (upstream connection # 1, #
3, # 5) when the backward RM cell 30 from the receiving terminal arrives at the ATM exchange # 1.

At this time, in the embodiment shown in FIG.
The exchange # 1 determines which upstream connection to transfer the arriving backward RM cell 30 to by the rotation priority control between the upstream connections where the flag is set.

That is, in the example of FIG. 7, assuming that services are set to be equally received in the order of # 1 to # 5, the backward RM cell arriving last time has been transferred to the upstream connection # 3. Therefore, as shown in FIG. 8, the backward RM cell 30 arriving this time is transferred to the upstream connection # 5, and the flag is lowered.

An embodiment of the second invention will be described with reference to FIGS.

Next, in the second embodiment of the present invention, each AT
The M exchange is provided with a counter for each upstream connection, which is incremented when a forward RM cell arrives and decremented when a backward RM cell is transferred.

Here, the ATM exchange operates in the backward R
If none of the counters is zero when the M cell arrives, it operates to save the smallest of the ERs of the continuously arriving backward RM cells. Similarly, it operates to store the logical sum of the CI bits of the arriving backward RM cells.

FIG. 9 shows a state when the forward RM cell 20 arrives at the ATM exchange # 1 from the upstream connection # 1.

At this time, in the embodiment shown in FIG.
The M exchange # 1 increments the counter of the upstream connection # 1 (C = 1), and transfers the forward RM cell 20 to the convergence destination (ATM exchange # 2).

FIG. 11 shows that when the counter values of all upstream connections are 0, the backward RM from the convergence destination
This is the state when the cell 30 has arrived.

At this time, in the embodiment shown in FIG.
The M exchange # 1 discards the arriving backward RM cell 30 without transferring it anywhere.

FIG. 13 shows that when the counter values of some upstream connections (upstream connections # 1, # 2, # 4, # 5) are not 0, the backward RM cell 30 from the convergence destination is sent to the ATM switch # 1. It is the state when it arrived.

At this time, in the embodiment shown in FIG.
The M exchange # 1 compares the resource management information described in the arriving backward RM cell 30 with the resource management information stored therein, and determines the arriving backward RM cell 30.
Is updated, and the upstream connection (upstream connection # 1, # 2, #
(4, # 5), copy and transfer the backward RM cell 30, and then lower the flag (Flag =
“0”).

Here, the ATM switch # 1 sets the smallest value among the ER calculated by itself, the ER to be stored, and the ER described in the backward RM cell 30 to the backward R.
The data is rewritten in the M cell 30 and transferred to the upstream destination. Also, A
If TM exchange # 1 is congested, or if the stored CI information is “1”, the backward R
The CI bit of the M cell 30 is set and transferred to the upstream destination. After transferring the backward RM cell 30 to the upstream destination,
ATM switch # 1 resets the minimum ER to be stored to PCR and resets the CI information to "0".

FIG. 15 shows that when the counter values of some upstream connections (upstream connections # 1, # 2, # 4, # 5) are not 0, the backward RM cell 30 from the convergence destination is sent to the ATM switch # 1. It is the state when it arrived.

At this time, in the embodiment shown in FIG.
The M exchange # 1 determines to which upstream connection the arriving backward RM cell 30 is transferred by the rotation priority control during the upstream connection whose counter value is not zero.

That is, in the example of FIG. 15, assuming that services are set equally in the order of # 1 to # 5, the backward RM cell arriving last time has been transferred to the upstream connection # 2. Therefore, as shown in FIG. 16, the backward RM cell 30 that has arrived this time is transferred to the upstream connection # 4, and the counter value is reduced by one.

An embodiment of the third invention will be described with reference to FIGS.

Next, in the third embodiment of the present invention, each AT
When a backward RM cell arrives, the M switch operates to save the smallest of the ERs of the continuously arriving backward RM cells. Similarly, it operates to store the logical sum of the CI bits of the arriving backward RM cells.

FIG. 17 shows a state when backward RM cell 30 arrives at ATM switch # 1 from the convergence destination.

At this time, ATM switch # 1 collects the resource management information described in the arrived backward RM cell 30, and updates the resource management information stored therein.
When the update of the resource management information ends, the backward RM cell 30 that has arrived is discarded (FIG. 18).

FIG. 19 shows a state in which the forward RM cell 20 from the upstream connection # 1 has arrived at the ATM exchange # 1.

At this time, the ATM exchange # 1 transfers the forward RM cell 20 that has arrived to the downstream of the convergence destination, and then transmits the backward R RM cell 20 describing the resource management information stored therein.
Create a new M-cell 30 and connect it to the upstream connection #
1 (FIG. 20).

The new backward RM cell may be the same as the forward RM cell with the DIR element changed to "1". Here, the ATM switch # 1 rewrites the smallest value of the ER calculated by itself and the ER stored therein into the backward RM cell and transfers it to the upstream destination.

When the ATM exchange # 1 is congested or when the stored CI information is "1", the CI bit of the backward RM cell is set and transferred to the upstream destination. After transferring the backward RM cell to the upstream destination, ATM switch # 1 sets the minimum ER to be stored to PC
Reset to R, and reset the CI information to “0”.

By operating as described above, the ATM
Since the exchange operates to return the same number of backward RM cells as the arriving forward RM cell, each data transmitting terminal must receive exactly the same number of backward RM cells as the forward RM cell issued by itself. Will be able to

[0072]

According to the present invention as described above,
In a multipoint-to-point type ATM connection, for a forward RM cell arriving at an ATM switch located at a convergence point of the connection, the A
It is possible that the TM exchange returns a backward RM cell describing meaningful resource management information in accordance with the transmission amount of each forward connection of the forward RM cell, and implements rate control immediately according to the state change. It is possible.

[Brief description of the drawings]

FIG. 1 is a state diagram illustrating a processing procedure of an RM cell according to a first embodiment of the present invention.

FIG. 2 is a state diagram illustrating an RM cell processing procedure according to the first embodiment of the present invention.

FIG. 3 is a state diagram illustrating an RM cell processing procedure according to the first embodiment of the present invention.

FIG. 4 is a state diagram illustrating an RM cell processing procedure according to the first embodiment of the present invention.

FIG. 5 is a state diagram illustrating a processing procedure of an RM cell according to the first embodiment of the present invention.

FIG. 6 is a state diagram illustrating a processing procedure of an RM cell according to the first embodiment of the present invention.

FIG. 7 is a state diagram illustrating a processing procedure of an RM cell according to the first embodiment of the present invention.

FIG. 8 is a state diagram illustrating a processing procedure of an RM cell according to the first embodiment of the present invention.

FIG. 9 is a state diagram illustrating a processing procedure of an RM cell according to the second embodiment of the present invention.

FIG. 10 is a state diagram illustrating a processing procedure of an RM cell according to the second embodiment of the present invention.

FIG. 11 is a state diagram illustrating a processing procedure of an RM cell according to the second embodiment of the present invention.

FIG. 12 is a state diagram illustrating a processing procedure of an RM cell according to the second embodiment of the present invention.

FIG. 13 is a state diagram illustrating a processing procedure of an RM cell according to the second embodiment of the present invention.

FIG. 14 is a state diagram illustrating a processing procedure of an RM cell according to the second embodiment of the present invention.

FIG. 15 is a state diagram illustrating a processing procedure of an RM cell according to the second embodiment of the present invention.

FIG. 16 is a state diagram illustrating a processing procedure of an RM cell according to the second embodiment of the present invention.

FIG. 17 is a state diagram illustrating a processing procedure of an RM cell according to the third embodiment of the present invention.

FIG. 18 is a state diagram illustrating a procedure of processing an RM cell according to the third embodiment of the present invention.

FIG. 19 is a state diagram illustrating a processing procedure of an RM cell according to the third embodiment of the present invention.

FIG. 20 is a state diagram illustrating a processing procedure of an RM cell according to the third embodiment of the present invention.

FIG. 21 is an internal structure of an RM cell defined in the ATM forum.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 10 Sending terminal 11 Receiving terminal 12 ATM exchange 20 Forward RM cell 30 Backward RM cell

Claims (7)

(57) [Claims] 1. ABR (Available Bit R)
a) Multipoint-to-Point AT for rate control between end terminals, which is congestion control of service class
RM (Resource Ma) in M connection
In an RM cell management system that performs cell transfer processing, an ATM switch located at a convergence point of a connection sets a flag indicating reception from the upstream when a forward RM cell arrives from the upstream. R
M cell management system. 2. The RM cell management system according to claim 1, wherein the ATM switch located at the convergence point of the connection, when a backward RM cell arrives from the downstream of the convergence destination, goes to all upstreams where the flag is set. Backward R toward
An RM cell management system, wherein, after transferring M cells, all the flags are set down. 3. The RM cell management system according to claim 1, wherein the ATM switch located at the convergence point of the connection, when a backward RM cell arrives from the downstream of the convergence destination, between the upstream where the flag stands. With rotation priority control,
An RM cell management system, wherein an upstream for transferring an arrived backward RM cell is selected, and only the selected upstream flag is lowered. 4. An ABR (Available Bit R)
a) Multipoint-to-Point AT for rate control between end terminals, which is congestion control of service class
RM (Resource Ma) in M connection
In an RM cell management system that performs cell transfer processing, the ATM switch located at the convergence point of the connection increases the counter when the forward RM cell arrives and increases the counter that decrements when the backward RM cell is transferred. An RM cell management system comprising: 5. The RM cell management system according to claim 4, wherein when the backward RM cell arrives from the downstream of the convergence destination, the backward RM cell is transferred to all the upstreams in which the counter value is not zero. An RM cell management system, wherein the counter is decremented. 6. The RM cell management system according to claim 4, wherein when the backward RM cell arrives from the downstream of the convergence destination, the backward RM cell arriving by the rotation priority control between the upstream where the counter value is not zero is determined. An RM cell management system, wherein an upstream to be transferred is selected, and the counter of the selected upstream is decremented. 7. An ABR (Available Bit R)
a) Multipoint-to-Point AT for rate control between end terminals, which is congestion control of service class
RM that performs RM cell transfer processing in M connection
In the cell management system, the ATM exchange located at the convergence point of the connection collects and updates the resource management information described every time a backward RM cell arrives from the convergence downstream, discards the RM cell, and discards the RM cell from the upstream. When a forward RM cell arrives, a new backward RM cell is created based on the resource management information collected and updated up to that time, and the backward RM cell is forwarded to a corresponding upstream RM cell. Management system.