JP2832591B2 - Simultaneous notification type congestion control method - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a broadcast notification type congestion control system, and more particularly to a broadcast notification type congestion control system used for controlling congestion in an ABR service provided on an ATM network.

[0002]

2. Description of the Related Art Generally, in an ATM network, an ABR (Available Bit Rate) service is provided in which a transmission terminal can control a transmission rate in response to a predetermined congestion notification from the network. Conventionally, this ABR service controls congestion by the following method.

First, a link buffer is provided for each link in a switching node, and the length of a waiting cell queue stored in these link buffers is monitored. Here, when the queue length of the waiting cell accumulated in the link buffer exceeds a predetermined threshold (threshold), it is determined that congestion has occurred only in the cell in which the queue has exceeded the threshold, and E is determined in cell units.
The CN (Explicit Congestion Notification) bit is turned “ON” to notify the receiving terminal of the congestion state.

When the receiving terminal receives the congestion notification, the receiving terminal periodically transmits an RM (Resource Matrix) transmitted from the transmitting terminal.
nagement) cell with a CI (Congestion Indication) bit set to "ON" and return transmission to notify the transmitting terminal of congestion. The transmitting terminal receives the RM cell and reduces (controls) the transmission rate to an adaptive rate, thereby recovering the congestion of the congested link.

[0005]

Therefore, in such a conventional ABR congestion control system, after the waiting cell queue length exceeds a predetermined threshold, the cell passes through the congested link (active connection during information transfer). Only for cells, adaptive congestion control on a cell-by-cell basis is performed. In particular, for other connections constituting the waiting cell queue length, the same congestion control is performed after the arrival of a subsequent cell. Is performed, there is a problem that a cell is dropped (dropped) due to a delay of the congestion notification and a cell retransmission is caused by this.

[0006] Furthermore, the rate is reduced independently (in connection units), not in a coordinated manner in consideration of all connections, but not necessarily in such a way that quick and accurate rate control is performed. There was no problem. The present invention is intended to solve such a problem. In the ABR service, cooperative rate control can be performed for all connections accommodated by a congested link, and congestion control can be performed quickly and accurately. It is an object of the present invention to provide a simultaneous notification type congestion control method capable of performing the above.

[0007]

In order to achieve the above object, a simultaneous notification type congestion control system according to the present invention is provided with a
The TM switching node includes a congestion detection unit that detects the occurrence of congestion on each link by monitoring the state of a link buffer provided for each link, and a transfer status of a connection accommodated in each link (transferring or paused). And a connection information table storing various connection information including (middle) and connection information of each connection accommodated in the congested link from the connection information table according to the congestion notification from the congestion detection unit.
A congestion notifying unit that calculates a new transmission rate in the transmitting terminal of each connection, and simultaneously notifies the transmitting terminals of these new transmission rates by congestion notification. Therefore, in response to the congestion notification from the congestion detection unit, the congestion notification unit reads the connection information of each connection accommodated in the congested link from the connection information table, and adds new information to the transmission terminal of each connection. The transmission rate is calculated and these
A new transmission rate is simultaneously notified to each transmitting terminal by a congestion notification.

The congestion notification unit refers to the connection information table in response to the congestion notification from the congestion detection unit, so that the transfer status of each of the connections accommodated in the congested link indicates that the transfer is in progress. The number of active connections shown is counted, and a value obtained by dividing the available bandwidth in the link by the number of active connections is instructed and notified at the same time as a new transmission rate in the transmitting terminal of each active connection. Therefore, a value obtained by dividing the available bandwidth on the link by the number of active connections is instructed and notified all at once as a new transmission rate in the transmitting terminal of each active connection.

[0009] The congestion notification unit changes a preset minimum guaranteed rate in response to the congestion notification from the congestion detection unit to a new value at the transmitting terminal of each inactive connection that is inactive.
The instruction is notified as the default setting rate. Accordingly, the preset minimum guaranteed rate is instructed and notified as a new initial setting rate in the transmitting terminal of each inactive connection that is inactive.

[0010]

Next, the present invention will be described with reference to the drawings. FIG. 1 is a block diagram showing a simultaneous notification type congestion notification method of an exchange node according to an embodiment of the present invention. In FIG. 1, 1 is a channel identifier unit of a connection accommodated in each link, that is, a connection unit. Monitor cell transfer status (transferring or paused)
Collects and outputs ACR (Allowed Cell Rate) from the transmitting terminal, monitors the waiting cell skew length accumulated in the link buffer of each link, and sends a congestion notification when this exceeds a predetermined threshold. It is a congestion detector that outputs.

Reference numeral 2 denotes a connection information table that stores the status of each connection output from the congestion detection unit 1;
Reads the latest information from the connection information table 2 in response to the congestion notification from the congestion detection unit 1, calculates an explicit rate ER (Explicit Rate), and simultaneously broadcasts all connections accommodated by the congested link. Is a congestion notification unit that instructs the transmission rate of each transmitting terminal by notifying congestion.

FIG. 2 is an explanatory view showing a connection information table. FIG. 2A shows a connection table provided in the switching node, and FIG. 2B shows a connection information table. The connection table is used to determine to which link the generated RM cell is to be transmitted when notifying congestion toward the transmitting terminal, and includes a channel identifier (V) indicating each input / output port and each connection.
PI / VCI).

The connection information table 2 stores, for each channel identifier (VPI / VCI) indicating each connection, the ACR collected by the congestion detection unit 1, the minimum guaranteed rate MCR (set by negotiation with the network at the time of connection setup). Minimum Cell R
ate) and an active display indicating the transfer status monitored by the congestion detection unit 1. The active display is, for example, active (= 1) when the number of cells flowing into the connection within a predetermined period T exceeds a predetermined threshold, and inactive (= 0) when the number is equal to or less than the predetermined threshold. It is set by a method such as

Next, the operation of the present invention will be described with reference to FIGS. FIG. 3 is an explanatory diagram showing an operation of ABR congestion control according to the present invention, and FIG. 4 is a flowchart showing an ABR congestion control procedure according to the present invention. In FIG. 3, # 1 to #
3 is a transmitting terminal, # 4 is a receiving terminal, sw1 to 3 are switching nodes disposed between the transmitting terminals # 1 to # 3 and the receiving terminal # 4, and 31 to 33 are transmitting terminals # 1 to # 3. And exchange node s
w1 and w1.

A link 30 connects the switching nodes sw1 and sw2, a link 35 connects the switching nodes sw2 and sw3, and a link 34 connects the switching node sw3 and the receiving terminal # 4, 41-43. Is a congestion notification / congestion regulation transmitted from the switching node sw1 to the transmission terminals # 1 to # 3 based on the simultaneous congestion notification.

Now, it is assumed that the transmitting terminals # 1 to # 3 are transferring cells to the receiving terminal # 4 via the connections VC1 to VC3 of the transmission rates r1 to r3, respectively. Is the link 35
Is housed in The congestion detection unit 1 of the switching node sw2 constantly monitors these connections VC1 to VC3, and the connection information table 2 stores values as shown in FIG.

The transmission rate r3 of terminal # 3 is "0".
In the connection information table 2 of FIG. 2B, the active indications of VC1 and VC2 both indicate "1", that is, active (during cell transfer), whereas the active indication of VC3 indicates "active". “0”, that is, inactive (during sleep), indicates that no cell is transmitted from terminal # 3.

As shown in the flowchart of FIG. 4, in the switching node sw2, the congestion detector 1 constantly compares the waiting cell queue length of the link 35 with a predetermined threshold value.
The occurrence of congestion in the link 35 is monitored (step S1). Here, as shown in FIG.
When the waiting cell queue length 52 of the link buffer 51 of the link 35 shared by the link 3 exceeds the predetermined threshold 53 (step S1: YES), the congestion detection unit 1 sets the link 3
At 5, it is determined that congestion has occurred, and the congestion notification unit 3 is notified of the occurrence of congestion.

In response to this, the congestion notification unit 3 refers to the active display of the connection information table 2 and calculates the number of connections during cell transfer, that is, the number of active connections Nvc (in this case, Nvc = 2) ( Steps S2 to S4). Subsequently, the congestion notification unit 3 calculates the ABR usable bandwidth BW of the link 35 (Step S).
5) By dividing (dividing) this by the number of active connections Nvc, an explicit rate ER (Explicit Rate) to be notified to each terminal during cell transfer is calculated (step S6).

Generally, the bandwidth of this type of link is A
In addition to the BR service, other services provided by the ATM network, such as CBR (Cons
tantBit Rate) V using service and variable communication speed
It is also allocated to BR (Variable Bit Rate) service. Therefore, in step S5, as the ABR usable bandwidth BW of the link 35 in which congestion has occurred, the bandwidth set in advance for the ABR service, or other services such as the CBR service and the VBR service based on the total bandwidth of the link 35 The remaining band amount obtained by subtracting the band amount used in is used.

Next, the congestion notification unit 3 checks each connection V
The transmission rates are simultaneously notified to the transmission terminals # 1 to # 3 of C1 to VC3 by the RM cells. First, one of the connections VC1 to VC3 accommodated in the link 35 is selected, and an RM cell is generated as a cell for notifying the transmitting terminal of the congestion (step S8).

Subsequently, referring to the active display of the connection information table 2, it is determined whether or not the selected connection is an active connection (step S9). If the selected connection is an active connection (step S9:
YES), the ER calculated in step S6 is set as the transmission rate in the RM cell (step S11), and the RM cell is transmitted to the transmitting terminal corresponding to the connection (step S12).

On the other hand, if the selected connection is an inactive connection (step S9: N
O), by referring to the MCR of the connection information table 2, the value set by negotiation with the network at the time of connection setup is set in the RM cell as the transmission rate (steps S10 and S1).
1), transmitting the RM cell to the transmitting terminal corresponding to the selected connection based on the connection table shown in FIG. 2A (step S12), returning to step S7, and transmitting the RM cell to all the connections. Repeat the process.

As described above, when congestion occurs in the link 35, the congestion detection unit 1 of the switching node sw2 detects the congestion, and the congestion notification unit 3 sends all the connections sharing the congested link 35. VC1 to VC
RM cells for which a predetermined transmission rate is set are simultaneously transmitted as congestion notifications 41 to 43 to the third transmission terminals # 1 to # 3. These congestion notifications (RM cells) 41 to 43
Is received by the transmitting terminals # 1 to # 3 via the link 30, the switching node sw1, and the respective links 31 to 33.

Therefore, among the transmitting terminals, active transmitting terminals # 1 and # 2 determine the number of cells to be transferred thereafter based on the transmission rates stored in these congestion notifications (RM cells) 41 and 42. It controls the transmission rate. Further, the inactive transmission terminal # 3 sets the transmission rate stored in the congestion notification (RM cell) 43, in this case, the minimum guaranteed rate MCR, as the cell inflow amount, that is, the initial set rate ICR (Initial Cell Rate), Based on this value, the transmission rate of cells to be transferred thereafter is controlled.

FIG. 6 is an explanatory diagram showing the variation of the bandwidth used in each connection. The horizontal axis represents the time axis, and the vertical axis represents the bandwidth used per unit time in each connection, that is, the cell transfer rate. For example, when the bandwidth used by each connection accommodated in the link 35 gradually increases and the waiting cell queue length 52 of the link buffer 51 (see FIG. 5) exceeds a predetermined threshold 53 at time T, As described above, the occurrence of congestion is detected, and a congestion notification is transmitted to the transmitting terminal of each connection.

In this case, the connections VC1 and VC2 are active (r1> 0, r2> 0) and the connection VC3 is inactive (r3 = 0: idle). Although only VC2 is subject to congestion regulation, according to the present invention, inactive connection VC3 is also subject to congestion regulation.

As described above, when the occurrence of congestion is detected in the link 35 at the switching node sw2, as shown in FIG. 6, the link 35 including not only the active connections VC1 and VC2 but also the inactive connection VC3 is set. All connections VC1 to VC3 shared
The congestion notifications 41 to 43 for instructing a predetermined transmission rate are simultaneously sent to the transmitting terminals # 1 to # 3, so that cooperative rate control of all connections accommodated by the congested link is performed. And congestion control can be quickly and accurately performed.

For the active connections during cell transfer, a value obtained by dividing the available bandwidth BW by the number of active connections Nvc is indicated simultaneously as the transmission rate of each transmitting terminal. The usable bandwidth BW is fairly and simultaneously allocated among the connections. In addition, the minimum guaranteed rate MCR
To the cell inflow amount, that is, the initial set rate ICR (Initial
Since the setting is instructed as (Cell Rate), it is possible to avoid (protect) congestion that may occur in the future.

In the congestion detection unit 1 of the switching node sw2, when the waiting cell queue length 52 of the link buffer of the link 35 becomes equal to or smaller than the threshold value 53 (step S1: NO), the congestion is detected. It is determined whether or not the transmission terminal # 1 has not been detected (step S13: YES). If the congestion is still being detected (step S13: YES), each of the transmission terminals # 1 to # 1 is determined using a predetermined RM cell, as in the above-described congestion notification processing. #
A predetermined congestion release process for notifying congestion release to all 3 at once is performed (step S14), and the process ends.

In response to the congestion release notification from the switching node sw2, among the transmitting terminals, the transmitting terminals # 1 and # 2 of the active connections VC1 and VC2 increase the normal transmission rate provided by the ABR service. Processing is performed. In the transmission terminal # 3 of the inactive connection VC3, a process of returning the initial set rate ICR to a normal value is performed.

[0032]

As described above, the present invention provides an ATM
The switching node includes a congestion detection unit that detects the occurrence of congestion on each link, and a connection information table that stores various types of connection information including the transfer status (transferring or idle) of the connection accommodated in each link. Provided,
In response to the congestion notification from the congestion detection unit, read the connection information of each connection accommodated in the link where the congestion has occurred from the connection information table, calculate a new transmission rate in the transmission terminal of each connection,
Since these new transmission rates are simultaneously notified to each transmitting terminal by the congestion notification, the cooperative rate control of all the connections accommodated by the congested link can be performed, and the congestion control can be performed quickly and accurately. Can be implemented.

Also, the congestion notification unit simultaneously notifies the value obtained by dividing the available bandwidth on the link by the number of active connections as a new transmission rate at the transmitting terminal of each active connection. The available bandwidth can be allocated fairly and simultaneously among all active connections. In addition, since the minimum notification rate set in advance is notified and notified as a new initial setting rate in the transmitting terminal of each inactive connection that is inactive by the convergence notification unit, it is possible to use the inactive connection in the future in any future. It is possible to avoid (protect) congestion that may occur in the system.

[Brief description of the drawings]

FIG. 1 is a block diagram of a simultaneous notification type congestion control system of switching nodes according to an embodiment of the present invention.

FIG. 2 is an explanatory diagram showing a connection control table.

FIG. 3 is an explanatory diagram showing a congestion control operation according to one embodiment of the present invention.

FIG. 4 is a flowchart showing a congestion control procedure according to one embodiment of the present invention.

FIG. 5 is an explanatory diagram showing a congestion detection method.

FIG. 6 is an explanatory diagram showing congestion restriction targets.

[Explanation of symbols]

1. Congestion detection unit 2. Connection information table 3.
Congestion notification unit, # 1 to # 3 ... transmitting terminal, # 4 ... receiving terminal,
sw1 to sw3: switching nodes, 30 to 35: links, 4
1 to 43: Congestion notification.

Continuation of the front page (56) References JP-A-2-257737 (JP, A) JP-A-5-502777 (JP, A) JP-A-4-111646 (JP, A) JP-A-2-224429 (JP) JP-A-2-170646 (JP, A) JP-A-8-18569 (JP, A) JP-A-3-175584 (JP, A) (58) Fields investigated (Int. Cl. ⁶ , DB (Name) H04L 12/28

Claims (3)

(57) [Claims] 1. A broadcast notification type congestion control system used for controlling congestion in an ATM network in which a transmitting terminal and a receiving terminal are connected by a predetermined link via an ATM switching node, wherein: A congestion detection unit that detects the occurrence of congestion on each link by monitoring the state of a link buffer provided for each link, and various types of information including the transfer status (transferring or idle) of the connection accommodated in each link A connection information table storing connection information of each connection, and reading connection information of each connection accommodated in the congested link from the connection information table in response to a congestion notification from the congestion detection unit, and transmitting the connection terminal of each connection. Calculate the new transmission rate at,
A simultaneous notification type congestion control method, comprising: a congestion notification unit for simultaneously notifying each of the transmitting terminals of the new transmission rates by a congestion notification. 2. The congestion control method according to claim 1, wherein the congestion notification unit refers to a connection information table in response to the congestion notification from the congestion detection unit to accommodate the congested link. The number of active connections whose transfer status indicates that the transfer is in progress is counted, and a value obtained by dividing the usable bandwidth on the link by the number of active connections is newly added to the transmission terminal of each active connection. A simultaneous notification type congestion control method characterized by simultaneously giving an instruction as a transmission rate. 3. The simultaneous notification type congestion control method according to claim 1, wherein the congestion notification unit sets a preset minimum guaranteed rate in response to the congestion notification from the congestion detection unit to each of the inactive connections. A simultaneous notification type congestion control method, wherein an instruction is notified as a new initial setting rate in the transmitting terminal of (1).