Multiplex communications – Data flow congestion prevention or control – Control of data admission to the network
Reexamination Certificate
1998-06-22
2002-02-05
Ton, Dang (Department: 2732)
Multiplex communications
Data flow congestion prevention or control
Control of data admission to the network
Reexamination Certificate
active
06345039
ABSTRACT:
This invention relates to an Asynchronous Transfer Mode (ATM) traffic controlling apparatus and an ATM traffic controlling method for controlling a traffic of multiplexed multimedia information such as sound, data, image, and so on, which is transmitted in asynchronous transfer mode.
BACKGROUND ART
The ATM has become the focal point of attention as the mainstream technology for a wide area Integrated Service Digital Network or ISDN.
FIG. 28
shows the structure of a cell used for ATM.
A cell
2801
to be used for ATM, a cell header
2802
which contains controlling information of cell
2801
, and cell information
2803
having data information and sound information of cell
2801
are shown in FIG.
28
. For ATM, any information in cell information
2803
, such as sound, data, image, facsimile, etc., is partitioned into a fixed length in cell information
2803
. The cell information
2803
is provided with cell header
2802
which contains logical channel (Virtual Call Indicator (VCI)) information, etc., required for switching cell
2801
. The cell header and the cell information form the cell
2801
. This cell
2801
format enables integrated transmission. Particularly, for a private in-house communication, where sound communication and inter-local area network (LAN) communication are the typical form of data communication, it is expected that the integration of this traffic and the ATM technology will help construct a more efficient transmission network than ever before.
FIG. 29
shows an example of the network configuration of sound/data integrated network using ATM.
In
FIG. 29
, an ATM multiplexed transmitter
2901
, an ATM switched network
2902
, a data ATM terminal
2903
for setting data connection and sending data cells, a sound ATM terminal
2904
for setting sound connection and sending sound cells, a private data traffic ATM line
2905
, a private sound traffic ATM line
2906
, a wide area ATM line
2907
for connecting ATM multiplexed transmitter
2901
and ATM switched network
2902
, a data traffic ATM line terminating unit
2908
, provided in ATM multiplexed transmitter
2901
, to be connected to data ATM terminal
2903
via private data traffic ATM line
2905
, a sound traffic ATM line terminating unit
2909
, provided in ATM multiplexed transmitter
2901
, to be connected to sound ATM terminal
2904
via private sound traffic ATM line
2906
, and a multiplexed transmitting unit
2910
provided in ATM multiplexed transmitter
2901
are illustrated.
Next, the operation is explained.
In ATM multiplexed transmitter
2901
, a cell received by data-system ATM line terminating unit
2908
and a cell received by sound-system ATM line terminating unit
2909
are multiplexed by multiplexed transmitting unit
2910
, and sent to wide area ATM line
2907
.
An efficient use of wide area ATM line
2907
, shown in
FIG. 29
is required for in-house communication. Because about
50
percent of sound communication is normally soundless, sound ATM terminal
2904
transmits sound information (hereinafter called a sound cell) consisting of only sound by private sound traffic ATM line
2906
at every cell forming cycle (a cycle being a time period during which sound is transformed into a cell), and tries not to transmit soundless portion so as to increase line efficiency.
Meanwhile, because real-time is generally in higher demand in sound communication than in data communication, ATM multiplexed transmitter
2901
gives preference to sending sound cells transmitted by sound ATM terminal
2904
to wide area ATM line
2907
. The data information (hereinafter a data cell) transmitted by data ATM terminal
2903
is transmitted to wide area ATM line
2907
using idle time during which no sound cell to be sent exists.
A method of realizing the conventional multiplexed transmitting unit
2910
for sound and data multiplexed transmission in ATM is set forth in
Analysis and Engineering of A Voice/Data Packet Multiplexer
of IEEE Transaction of Communication Vol.41 No. 11, pages 1656 to 1667.
FIG. 30
shows a configuration of the conventional multiplexed transmitting unit
2910
, where, a sound/data identifying unit
3001
for identifying whether a received cell is sound or data, a data cell transmitting buffer
3002
for storing data cells for transmission, a sound cell transmitting buffer
3003
for storing sound cells for transmission, a transmitting circuit
3004
for transmitting sound or data cells, a receiving circuit
3005
for receiving sound or data cells, and a receiving buffer
3006
for storing sound or data cells received by receiving circuit
3005
are depicted.
The operation is explained next.
In
FIG. 30
, sound/data identifying unit
3001
identifies whether or not a cell is a sound cell or a data cell upon its arrival from data traffic ATM line terminating unit
2908
or sound traffic ATM line terminating unit
2909
. A sound cell is stored in sound cell transmitting buffer
3003
and a data cell is stored in data cell transmitting buffer
3002
.
Then, transmitting circuit
3004
reads the sound cell from sound cell transmitting buffer
3003
and transmits into wide area ATM line
2907
. If no sound cell is stored in transmitting buffer
3003
and the data cells are stored in data cell transmitting buffer
3002
, the data cells are read and transmitted into wide area ATM line.
Meanwhile, cells arriving from other terminals by way of wide area ATM line
2907
are received by receiving circuit
3005
and stored in receiving buffer
3006
, and then transmitted to data traffic ATM line terminating unit
2908
or sound traffic ATM line terminating unit
2909
. Sound and data multiplexed transmission is realized in this way by giving preferential transmission to sound cells using separated buffers.
However, when the volume of traffic of sound cells grows heavy, the probability for data cells being kept waiting in the data cell transmitting buffer increases, which may result in buffer overflow destroying part of cells if the capacity of the data cell transmitting buffer is insufficient. On the other hand, in order to suppress the cell disposal rate within an appropriate range in an event of buffer overflow, a large capacity is required for the data cell transmitting buffer.
For the application of ATM to a wide area network data communication such as inter-LAN communication, it is recently become known that communication efficiency gets degraded significantly if the cell disposal rate could not be suppressed. ABR Service Class Quality Assessment by the National Convention for Electronics Information Communication Academy SB-10-5 in 1996, presented with an effective measure using a data terminal capable of adjusting a transmission rate depending on the network load.
FIG. 31
is a diagram showing an adjustment sequence of the transmission rate. It shows the transmission sequence of data ATM terminal
2903
a
in normal mode.
FIG. 32
shows an adjustment sequence of the transmission rate for data ATM terminal
2903
a
in abnormal mode.
FIG. 33
shows the structure of a data traffic control cell (hereinafter an RM cell) format for controlling the data traffic indicated in sequences of
FIGS. 31 and 32
.
In
FIG. 33
, a cell
3301
, a header
3302
indicating the RM cell, information
3303
of cell
3301
, and a transfer rate specified value
3304
included in information
3303
are illustrated.
How to adjust the transmission rate is discussed below with reference to FIG.
31
.
Data ATM terminal
2903
a
on the transmitting side is assumed to have a predetermined number of times (Nrm−1). Nrm indicates the ratio of transmitting RM cells, e.g., the number of cells per RM interval. Each time the predetermined number of times (Nrm−1) of data cells are transmitted, an RM cell (called a forward RM cell) is transmitted once. Data ATM terminal
2903
b
on the receiving side returns a RM cell (called a backward RM cell) to data ATM terminal
2903
a
on the transmitting side. The backward RM cell contains transfer rate specified value
3304
indicated as the valid transmission rate
Leydig , Voit & Mayer, Ltd.
Mitsubishi Denki & Kabushiki Kaisha
Ton Dang
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