Congestion relieving system in a communication system

• US 5,590,132 A
• Filed: 03/22/1994
• Issued: 12/31/1996
• Est. Priority Date: 02/05/1991
• Status: Expired due to Term

• Current Assignee: Fujitsu Limited
• Original Assignee: Fujitsu Limited
• Inventors: Sekine, Katsumi, Ishibashi, Ryoichi
• Primary Examiner(s): Olms, Douglas W.
• Assistant Examiner(s): Jung, Min
• Application Number:
  US08/216,049
• Time in Patent Office: 1,015 Days
• Field of Search: 370/94.1, 370/94.2, 370/60, 370/60.1, 370/85.9, 370/110.1
• US Class Current: 370/236
• CPC Class Codes: H04L 12/2852 Metropolitan area networks
• CPC Class Codes: H04L 2012/5613 Bus (including DQDB)
• CPC Class Codes: H04L 2012/5629 Admission control
• CPC Class Codes: H04L 2012/5678 Traffic aspects, e.g. arbitration, load balancing, smoothing, buffer management
• CPC Class Codes: H04Q 11/0478 Provisions for broadband connections

Abstract

A congestion relieving system in a communication system includes a local switch (62a) and a customer station including a network terminator (64a) connected to the local switch (62a) and plural data receiving/transmitting units (65) connected to the network terminator (64a) through buses (67D and 67U) conformable to a DQDB protocol. The local switch (62a) includes a congestion relieving signal generating unit for generating a congestion relieving signal when congestion is detected. The congestion relieving signal is inserted, as a request bit, into a request bit area in the cell having a format conformable to the DQDB protocol. The cell is then transmitted from the local switch (62a) through the network terminator (64a) to the data receiving/transmitting units (65), and each data receiving/transmitting unit (65), is restricted, under the DQDB protocol, to transmit data, when the data receiving/transmitting unit (65) receives the request bit.

Claims

1. A communication system for relieving congestion, comprising:

a master device; and

a customer station connected to said master device, wherein

said customer station includes slave devices, each connected in parallel with each other through an up-signal bus and a down-signal bus to said master device, and wherein

said master device includes;

congestion determining means for determining whether or not congestion occurs in the communication system;

congestion relieving signal generating means, operatively connected to said congestion determining means, for generating a congestion relieving signal when the congestion is detected by said congestion determining means; and

cell transmitting means, operatively connected to said congestion relieving signal generating means, for transmitting a cell having a request bit area, where said congestion relieving signal is inserted, as a request bit, into the request bit area in said cell, and said cell being transmitted from said cell transmitting means in said master device, via a down signal bus, to said slave devices, wherein

said customer station monitors the request bit to control transmitting data via the up-signal bus, and wherein said customer station inserts the request bit into the request bit area to indicate that the customer station possesses data to be transmitted.

2. A communication system for relieving congestion, comprising:

a local switch; and

a customer station including a network terminator connected to said local switch and data receiving/transmitting units connected to said network terminator through buses wherein said local switch comprises;

congestion determining means for determining whether the congestion occurs in the communication system;

congestion relieving signal generating means, operatively connected to said congestion determining means, for generating a congestion relieving signal when the congestion is detected by said congestion determining means; and

cell transmitting means, operatively connected to said congestion relieving signal generating means, for transmitting a cell having a request bit area, where said congestion relieving signal is inserted, as a request bit, into a request bit area in said cell, said cell being transmitted from said cell transmitting means in said local switch through said network terminator to said data receiving/transmitting units,

wherein said customer station monitors the request bit to control transmitting data via an up-signal bus,

wherein each of said data receiving/transmitting units, comprises;

request bit transmitting means for transmitting the request bit, when one of said data receiving/transmitting units requests to transmit the data;

busy bit transmitting means for transmitting a busy bit, said busy bit being inserted into a busy bit area in said cell when said one of said data transmitting/receiving units inserts data into said cell, and said busy bit being removed from said cell when said cell is received by a destination;

a request counter having contents, connected to said request bit transmitting means and counting up in response to the request bit transmitted through a down-signal bus from said network terminator to the one of said data receiving/transmitting units and for counting down in response to an inverted busy bit transmitted through an up-signal bus from the one of said data receiving/transmitting units to said network terminator before the one of said data receiving/transmitting units transmits the request bit; and

a down counter, connected to said request counter and loading the contents in said request counter as loaded contents when the one of said data receiving/transmitting units transmits said request bit, and counting down the loaded contents to zero in response to the inverted busy bit transmitted through said down-signal bus from said network terminator to the one of said data receiving/transmitting units, wherein

the one of said data receiving/transmitting units is restricted to transmit data until the loaded contents in said down counter become zero.

3. A communication system as claimed in claim 2, wherein said cell is an ATM cell.

4. A communication system as claimed in claim 3, wherein said data receiving/transmitting units are terminal equipment having interfaces adapted to the ATM cell.

5. A communication system as claimed in claim 2, wherein said communication system is a broadband ISDN.

6. A communication system as claimed in claim 2, wherein said data receiving/transmitting units are terminal adapters having interfaces adapted to the ATM cell.

7. A communication system for relieving congestion, comprising:

a local switch;

a customer station including a network terminator connected to said local switch and data receiving/transmitting units connected to said network terminator through buses wherein said local switch comprises;

congestion determining means for determining whether the congestion occurs in the communication system,

congestion relieving signal generating means, operatively connected to said congestion determining means, for generating a congestion relieving signal when the congestion is detected by said congestion determining means, and

cell transmitting means, operatively connected to said congestion relieving signal generating means, for transmitting a cell having a request bit area, where said congestion relieving signal is inserted, as a request bit, into a request bit area in said cell, said cell being transmitted from said cell transmitting means in said local switch through said network terminator to said data receiving/transmitting units,

wherein said customer station monitors the request bit to control transmitting data via an up-signal bus; and

an exchange connected to said local switch generating congestion relieving requests identifying a ratio of cells to be restricted,

wherein said local switch further comprises congestion control means for generating the congestion relieving request identifying the ratio of the cells to be restricted when the congestion occurs in said communication system, and

wherein said congestion determining means comprises selecting means for selecting a maximum ratio among the ratio included in each of the congestion relieving requests received from said exchange and said congestion control means in said local switch, and said cell transmitting means in said local switch comprises inserting means for inserting said congestion relieving signal into the cells with the maximum ratio.

8. A congestion relieving system for relieving congestion, comprising:

a local switch; and

a customer station including a network terminator connected to said local switch and data receiving/transmitting units connected to said network terminator through buses wherein said local switch comprises;

congestion determining means for determining whether the congestion occurs in the communication system;

congestion relieving signal generating means, operatively connected to said congestion determining means, for generating a congestion relieving signal when the congestion is detected by said congestion determining means; and

cell transmitting means, operatively connected to said congestion relieving signal generating means, for transmitting a cell having a request bit area, where said congestion relieving signal is inserted, as a request bit, into a request bit area in said cell, said cell being transmitted from said cell transmitting means in said local switch through said network terminator to said data receiving/transmitting units,

wherein said customer station monitors the request bit to control transmitting data via an up-signal bus,

wherein said buses include a down-signal bus transmitting the cell from said local switch and an up-signal bus, said down signal bus sequentially, connected to said data receiving/transmitting units, and connected to said up-signal bus, the cell transmitted by said down-signal bus being used as an empty cell in the up-signal bus.

9. A method for transmitting a first cell having a request bit from a local switch to a customer station by way of a down-signal bus and for receiving a second cell from the customer station by way of an up-signal bus, comprising the steps of:

generating a cell restriction signal when the customer station is to be restricted from sending the second cell;

inserting the cell restriction signal as the request bit in the first cell;

transmitting the first cell to the customer station;

monitoring the request bit to control sending the second cell onto the up-signal bus; and

inserting the request bit into the first cell to indicate that the customer station possesses data to be sent on the second cell.

10. A communication system for transmitting a first cell having a request bit from said communication system to a customer station via a down-signal bus and for receiving a second cell from the customer station via an up-signal bus, said communication system comprising:

congestion relieving means for generating a cell restriction signal, when the customer station is restricted from sending the second cell; and

cell transmitting means, operatively connected to said congestion relieving means, for inserting the cell restriction signal as the request bit in the first cell and for transmitting the first cell to the customer station, wherein the customer station receives the first cell and checks the request bit to determine whether to transmit the second cell to said communication system via the up-signal bus, and wherein the customer station inserts the request bit into the first cell to indicate that the customer station possesses data to transmitted on the second cell.