Apparatus for controlling cell transmission timing

Details Apparatus for controlling cell transmission timing Apparatus for controlling cell transmission timing

1998-01-06

2001-06-19

Ton, Dang (Department: 2732)

Multiplex communications

Data flow congestion prevention or control

Control of data admission to the network

C370S395430

Reexamination Certificate

active

06249511

ABSTRACT:

BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to an apparatus for controlling cell transmission timing, for example, in an ATM (Asynchronous Transfer Mode) exchange.
2. Description of Prior Art
As one such exchange, Japanese patent laid-open publication No. 7-327033 has taught a method and apparatus for controlling cell transmission timing.
FIG. 7
depicts the configuration of the cell transmission timing controller (hereinafter, referred to as a shaper) disclosed in the publication. The shaper accommodates a plurality of connections
7
each involving a plurality of cells
8
to be transmitted. To control cell transmission, the shaper incorporates the cell interval managing unit
1
, the cell transmission time managing unit
2
, the cell multiplexing unit
3
, the connection managing unit
4
, and the unit time generating unit
5
, wherein the cell transmission time managing unit
2
includes the cell transmission time table
2
A, the cell interval managing unit
1
includes the cell interval table
1
A, and the cell multiplexing unit
3
includes the cell transmission scheduling table
3
A. The cell transmission time table
2
A stores times at which cells are transmitted. The cell interval table
1
A stores cell intervals between the times at which a cell (hereinafter, referred to as “preceding cell”) is transmitted and the times at which a cell following the preceding cell) (hereinafter, referred to as “following cell”) is transmitted.
To obtain the time at which the following cell will be transmitted, the shaper reads out of the cell interval table
2
A a cell interval with respect to the preceding cell and the following cell. Thereinafter, the shaper adds the read cell interval to the time at which the preceding cell will be transmitted or has been transmitted (hereinafter, referred to as a preceding cell transmission time), thus storing the preceding cell in the cell transmission time managing unit
2
A. In this way, the shaper determines the time at which the following cell will be transmitted (hereinafter, referred to as a following cell transmission time.)
Here, a unit time [seconds/cell] is defined as the period of time which one cell requires for transmission. Assuming that a cell transmission rate of one of the connections
7
is R [cells/second] and that the cell transmission rate of the shaper is P [cells/second], the cell interval in the connection is given as P/R [seconds/cell]. This indicates that a smaller cell transmission rate of a connection permits the cell interval in the connection to be longer, and vice versa.
After reading out the following cell transmission time from the cell transmission time managing table
2
A, the cell transmission time managing unit
2
registers the following cell in the cell transmission scheduling table
3
A in such a fashion that the following cell can be transmitted at the following cell transmission time. Once the following cell transmission time comes, the following cell is permitted to be transmitted.
As described above, if the cell transmission rate of a connection
7
is small, the cell interval in the connection
7
becomes large. Since the following cell transmission time is calculated using the cell interval with respect the preceding cell and the following cell, the large cell interval makes the following cell transmission time large. This forces the cell interval table
1
A, the cell transmission time table
2
A and the cell transmission scheduling table
3
A to be large enough to store such large values.
Herein, assuming that the cell transmission rate or bandwidth of the shaper is 622.08 [Megabits/second], namely, (622.08×10{circumflex over ( )}6)/(8×53) [cells/second] and that the cell transmission rate R of a connection
7
is 10 [cells/second], the cell transmission scheduling table
3
A requires a storage area corresponding to the cell interval more than 146,717 [seconds/cell].
SUMMARY OF THE INVENTION
It is therefore an object of the present invention to provide an apparatus for controlling cell transmission timing, which controls cell transmission in such a manner that a cell transmission rate of each connection to be controlled corresponds to a given transmission rate.
According to the present invention, an apparatus for controlling cell transmission timing, which determines following cell transmission time of transmitting a following cell that follows a preceding cell, uses the preceding cell transmission time of transmitting the preceding cell and a time interval specified by a cell transmission rate of a connection along which the preceding cell and the following cell flow, to register the following cell in a step so as to be transmitted at the following cell transmission time. The apparatus comprises an accommodation circuit accommodating a plurality of connections along which a plurality of cells flow, each of the plurality of connections allocated a cell transmission rate that is represented with a cardinal number, an exponent, and a function of a mantissa. The apparatus also includes a plurality of cell transmission queues each being allocated a bandwidth for transmitting the plurality of cells and temporarily storing the plurality of cells, each of the plurality of cell transmission queues being referred to as a class and having a plurality of steps, each of the plurality of steps being a registered one of the plurality of the cells, the registered cells shifting toward a given step that permits a cell shifted therein to be transmitted. The apparatus further includes a controlling circuit controlling the registering of the cells in one of the plurality of steps in the plurality of queues, using the cardinal number, the exponent, and the function of the mantissa of the connection of the cell.


REFERENCES:
patent: 5313579 (1994-05-01), Chao
patent: 5491691 (1996-02-01), Shtayer et al.
patent: 5517495 (1996-05-01), Lund et al.
patent: 5535201 (1996-07-01), Zheng
patent: 5926458 (1999-07-01), Yin
patent: 7-327033 (1995-12-01), None
Informative Appendix I: Implementation Examples on ABR Service Category, Traffic Management Specification Version, ATM Forum Technical Committee

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