Multiplex communications – Pathfinding or routing – Switching a message which includes an address header
Reexamination Certificate
1999-11-04
2003-12-23
Hsu, Alpus H. (Department: 2665)
Multiplex communications
Pathfinding or routing
Switching a message which includes an address header
C370S395100, C370S422000, C370S428000, C370S461000, C370S463000, C370S474000, C370S535000, C370S536000, C370S537000
Reexamination Certificate
active
06667977
ABSTRACT:
BACKGROUND OF THE INVENTION
This invention relates to an ATM cell multiplexing apparatus and method. More particularly, the invention relates to an ATM cell multiplexing apparatus, which is provided between a terminal and an ATM switch, for assembling data input from multiple terminal lines into ATM cells, time-division multiplexing the ATM cells and transmitting them to an ATM network, and to method of multiplexing ATM cells.
ATM (Asynchronous Transfer Mode) is expected to be a viable technique for realizing multimedia communications and ATM schemes intended for communication of high-speed data especially between computers are being developed. In addition, networks for interworking of existing communications protocols such as voice, HDLC and FR (frame relay) protocols in ATM are being sought in the market, as evidenced by recent ATM Forums. Constructing such a network entails constructing ATM switches as a backbone network. In addition, in order to raise the efficiency of terminal-line accommodation, an ATM cell multiplexer is placed as an intermediate apparatus between an ATM switch and a terminal.
(a) General Placement of ATM Cell Multiplexers
FIG. 14
is an explanatory view illustrating the general placement of ATM cell multiplexers. ATM cell multiplexers
2
1
-
2
n
on the transmitting side assemble data, which has been received from terminals
1
1
-
1
m
, into cells and send the cells to an ATM network
3
(composed of ATM switches
3
a
,
3
b
) via trunk lines
4
. ATM cell multiplexers
6
1
-
6
n
on the receiving side disassemble the ATM cells, which have been received from the ATM network
3
via a trunk line
5
, and send the resulting data to terminals
7
1
-
7
m
. The ATM cell multiplexers
2
1
-
2
n
,
6
1
-
6
n
are capable also of transmitting data in similar fashion in a direction opposite that set forth above.
Exacting traffic control (control of Quality of Service, or QOS) specific to ATM protocols is required with ATM cell multiplexers of the kind mentioned above. Conventional ATM cell multiplexers come equipped with ATM switches in order to carry out such traffic control. However, a drawback with such an arrangement is that ATM switches involve high manufacturing cost. Another shortcoming is complicated software and hardware control and an apparatus that is large in size. For these reasons, an ATM cell multiplexer that does not employ an ATM switch is in demand. However, with schemes that simply multiplex cells, it is necessary to delay cells to avoid collision when cells in a plurality of connections come into contention. Owing to such delay, a simple cell multiplexing scheme cannot be applied when multiplexing and transmitting media that has little tolerance for delay, such as low-speed CBR (Constant Bit Rate) media.
In view of the foregoing, an ATM cell multiplexing apparatus requires a method of multiplexing, efficiently and simply, cells transmitted from multiple CLAD (Cell Assembly and Disassembly) units which assemble data received from terminals into cells and disassemble cells received from trunk lines. To accomplish this, there has been proposed a distributed-CLAD ATM cell multiplexing apparatus by which cells, which are transmitted from multiple internal CLAD units, are statistically multiplexed and transmitted on an ATM bus efficiently and simply.
(b) Proposed ATM Cell Multiplexing Apparatus
FIG. 15
is a block diagram illustrating the proposed ATM cell multiplexing apparatus mentioned above. The apparatus includes an ATM bus scheduler
11
, an ATM bus
12
for sending ATM cells, a plurality of CLADs (cell assembler/disassemblers)
13
0
-
13
5
, a trunk line controller
14
and a backup line controller
15
for backing up the trunk line controller.
The cell assembler/disassemblers
13
0
-
13
5
, which are connected to the ATM bus
12
in parallel, assemble data input from corresponding terminal lines
16
0
-
16
5
into ATM cells and send the cells to the ATM bus
12
. Further, the cell assembler/disassemblers
13
0
-
13
5
accept ATM cells from a network via the ATM bus
12
, disassemble the cells and send the resulting data to the corresponding terminal lines. A prescribed service category (CBR, rt-VBR, nrt-VBR, UBR) and an amount of traffic (peak cell rate, sustained cell rate) are provided for each terminal line in advance. The ATM cell multiplexing apparatus performs traffic management conforming to the service category and amount of traffic for every cell assembler/disassembler
13
0
-
13
5
. CBR (Constant Bit Rate) is a constant-speed bit rate service, rt-VBR (real-time Variable Bit Rate) is a real-time variable bit rate service, nrt-VBR (not real-time Variable Bit Rate) is a variable bit rate service that is not real-time, and UBR (Unspecific Bit Rate) is a random bit rate service. The CBR service is set for the terminal line
16
0
, the rt-VBR service for the terminal line
16
1
, the UBR service for the terminal lines
16
2
,
16
5
, and the nrt-VBR service for the terminal lines
16
3
,
16
4
.
The ATM bus scheduler
11
, which is for providing the cell assembler/disassemblers
13
0
-
13
5
an opportunity to transmit cells, controls the sending and receiving of cells performed via the ATM bus
12
. For example, the ATM bus scheduler
11
provides the privilege to transmit to cell assembler/disassemblers allocated to respective ones of N-number of cyclically repeating time slots. A cell assembler/disassembler that has been given the privilege to transmit is thus allowed to send cells to the ATM bus. The trunk line controller
14
time-division multiplexes ATM cells sent to the ATM bus
12
from the cell assembler/disassemblers and transmits these cells to the network via a trunk line
17
1
. In addition, the trunk line controller
14
sends the ATM bus
12
ATM cells from the network. By virtue of this arrangement, the ATM cell multiplexing apparatus implements cell multiplexing and traffic control without being equipped with an ATM switch.
Basically, the ATM bus scheduler
11
controls the ATM bus
12
in the following manner:
(1) In a situation where the plurality of existing cell assembler/disassemblers
13
0
-
13
5
transmit cells to the ATM bus
12
, the ATM bus scheduler
11
performs control so as to avoid contention among transmitted cells on the ATM bus
12
.
(2) The cell assembler/disassemblers
13
0
-
13
5
transmit cells to an ATM switch in accordance with the service categories (CBR, rt-VBR, nrt-VBR, UBR) stipulated by the ATM Forum. The ATM bus scheduler
11
, therefore, grants the cell assembler/disassemblers the privilege to transmit based upon the service categories. A cell assembler/disassembler among the cell assembler/disassemblers
13
0
-
13
5
may transmit cells to the ATM bus
12
only if it has been granted the transmission privilege by the ATM bus scheduler
11
.
(3) In a case where the cell assembler/disassemblers
13
0
-
13
5
transmit cells, the ATM bus scheduler
11
controls cell transmission in conformity with traffic in such a manner that the transmission rate will not exceed a pre-established peak cell rate (PCR) and sustained cell rate (SCR).
(c) Schedule Table
In order to realize (1) to (3) above, the ATM bus scheduler
11
has three schedule tables, namely a main schedule table MST, a first subschedule table SST
1
for nrt-VBR and a second subschedule table SST
2
for UBR, as shown in
FIG. 16
, and performs traffic management, in accordance with the service category and traffic, based upon these tables.
The main schedule table MST establishes the transmission privilege with regard to the cell assembler/disassemblers
13
0
,
13
1
,
13
3
,
13
4
(
FIG. 15
) for the CBR service, rt-VBR service and nrt-VBR service and sets which cell assembler/disassembler is to be granted the transmission privilege in each of the N-number of cyclically repeating time slots TS
1
to TS
N
. The setting of the transmission privilege is performed when a cell assembler/disassembler or trunk line is registered or changed. The transmission privilege is set taking into consideration the service category and traffic (peak c
Fujitsu Limited
Hsu Alpus H.
Katten Muchin Zavis & Rosenman
Stevens Roberta
LandOfFree
ATM cell multiplexing apparatus and method does not yet have a rating. At this time, there are no reviews or comments for this patent.
If you have personal experience with ATM cell multiplexing apparatus and method, we encourage you to share that experience with our LandOfFree.com community. Your opinion is very important and ATM cell multiplexing apparatus and method will most certainly appreciate the feedback.
Profile ID: LFUS-PAI-O-3183087