Multiplex communications – Data flow congestion prevention or control – Flow control of data transmission through a network
Reissue Patent
1997-02-27
2001-11-06
Ton, Dang (Department: 2661)
Multiplex communications
Data flow congestion prevention or control
Flow control of data transmission through a network
C370S399000
Reissue Patent
active
RE037435
ABSTRACT:
BACKGROUND OF THE INVENTION
This invention pertains to a supervision control system for supervising the inflow of cells to an ATM switching system.
The ATM switching system switches cells having fifty-four (54) bytes split from various data, such as voice data, image data and other numerical data, and transmits in a multiplexed form the various data at different transmission speed. Of the fifty-four (54) bytes in a cell, forty-eight (48) bytes form an information field and six (6) bytes form a header part. Of the four (4) bytes, i.e. thirty-two (32) bits, in the header part excluding two (2) bytes forming a tag, twenty-eight (28) bits indicate a VPI/VCI (virtual path identifier/virtual channel identifier), two (2) bits indicate a PT (payload type), one (1) indicates a CLP (cell loss priority) and one (1) bit is for a RES (reserve).
A buffer in a multiplexer for these cells can experience an overflow when an unexpected number of cells flow in. Since overflowing cells are discarded, the communications quality is deteriorated. Although such a problem can be avoided by using a buffer having a larger capacity, a larger delay results, which is critical in transmitting voice data, image data, and so forth.
Therefore, a buffer is required in which the occurrence of an overflow and its effect are minimized.
DESCRIPTION OF THE RELATED ART
FIG. 1
is a block diagram of an ATM switching system.
As shown in
FIG. 1
, a plurality of terminals (TE)
10
are connected through respective terminal adapters (TA)
9
to one of plural network terminators (NT)
8
in an ATM switching system.
The network terminators (NT)
8
are connected through respective interoffice trunks
6
to one (1) of plural broadband remote switching units (BRSU)
7
.
The broadband remote switching units (BRSU)
7
are connected to one (1) of a plurality of central offices (CO)
5
.
The interoffice trunks
6
interconnect the central offices (CO)
5
. The interoffice trunks
6
and subscriber lines are high speed transmission paths, such as an optical transmission path e.g. comprising a SONET (Synchronous Optical Network), having bands of one hundred fifty-five mega-herts (155 MHz), six hundred twenty-two mega-herts (622 MHz) or higher.
FIG. 2
shows a cell configuration.
As described earlier, voice data, image data, numerical data, etc. from the terminals (TE)
10
are split into cells having fifty-four (54) bytes. Because one (1) word is defined to comprise two (2) bytes, a cell has twenty-seven (27) words. As shown in
FIG. 2
, of the fifty-four (54) bytes in a cell, forty-eight (48) bytes form an information field and six (6) bytes form a header part. Of the six (6) bytes, i.e. forty-eight (48) bits, in the header part, two (2) bytes, i.e. sixteen (16) bits, form a tag, twenty-eight (28) bits indicate a VPI/VCI (virtual path identifier/virtual channel identifier), two (2) bits indicate a PT (payload type), one (1) bit indicates a CLP (cell loss priority) and one (1) bit is for a RES (reserve).
The network terminators (NT)
8
send the cells to the broadband remote switching unit (BRSU)
7
.
The terminal adapters (TA)
9
receive cells from corresponding terminals (TE)
10
through the network terminators (NT)
8
and send the decelled voice data, image data, numerical data, etc. to the terminals (TE)
10
.
FIG. 3
is a block diagram of one (1) of the broadband remote switching units (BRSU)
7
.
A multiplexer/demultiplexer (MDX)
12
multiplexes cells asynchronously inputted from subscribers through a buffer and transmitted over a plurality of subscriber line trunks
11
, which are connected to respective subscriber lines. A concentrator switch (CSW)
13
switches the multiplexed cells. A multiplexer/demultiplexer (MDX)
14
demultiplexes the switched cells over to an appropriate one (for the predetermined central office) of a plurality of interoffice trunks
15
, which form interoffice cell transmission paths.
The multiplexer/demultiplexer (MDX)
14
multiplexes cells asynchronously inputted from correspondent subscribers through a buffer and transmitted over the interoffice trunks
15
. The concentrator switch (CSW)
13
switches the multiplexed cells. The multiplexer/demultiplexer (MDX)
12
demultiplexes the switched cells over to an appropriate one (for the predetermined subscriber) of a plurality of subscriber line trunks
11
.
A local processor interface (LPIF)
16
connects a local processor (LPR)
17
with the concentrator switch (CSW)
13
and multiplexers/demultiplexers (MDXs)
12
and
14
.
When a larger number of cells flow into the multiplexer/demultiplexer (MDX)
12
, its buffer causes some cells to overflow. Therefore, a virtual path is set at a call-up by having a subscriber declare his cell transmission band and by judging whether or not the cells can be multiplexed in the declared band.
In this case, if this subscriber sends cells over the declared band, cells from other subscribers who share the same buffer with this subscriber are also discarded.
That is, if any subscriber sends cells over the declared band, a large ill-effect occurs such that cells from other subscribers are also discarded.
SUMMARY OF THE INVENTION
This invention pertains to a supervision control system for supervising the inflow of cells to an ATM switching system.
It aims at avoiding a congestion state caused by a cell inflow over a band declared by a subscriber.
It configures a supervision control apparatus for an ATM (Asynchronous Transmission Mode) cell switching system comprising a supervisor and a multiplexer. The supervisor further comprises a cell counter and a judge. The cell counter counts cells transmitted from a subscriber in a predetermined duration unit. The judge attaches a sign to the cells when the value counted by the cell counter exceeds a predetermined value. The multiplexer discards the cells to which the sign is attached when a buffer does not have enough capacity during a cell multiplexation.
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The Institute of Electronics, Information and Communication Engineers, K. Asatani, et al, vol. J72-B-I, No. 11, pp. 886-
Aihara Naoki
Aso Yasuhiro
Kakuma Satoshi
Murayama Masami
Yoshimura Shuji
Fujitsu Limited
Staas & Halsey , LLP
Ton Dang
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