Multiplex communications – Pathfinding or routing – Switching a message which includes an address header
Reexamination Certificate
1997-02-19
2002-12-10
Nguyen, Chau (Department: 2663)
Multiplex communications
Pathfinding or routing
Switching a message which includes an address header
C370S431000, C359S199200
Reexamination Certificate
active
06493350
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention generally relates to a network system for transmitting a signal using a plurality of channels, and a transmission method of the signal therein. More particularly, the present invention relates to a network system which transmits a signal through a plurality of channels and includes a node device for connecting a terminal equipment and the like to the plural channels and in which an interactive transmission is performed between the node devices.
2. Related Background Art
In recent years, study and development have been made with respect to network systems each of which employs a plurality of channels for transmission of a signal, since a high-speed network system, which includes terminal equipments connected thereto, is required, following an increase in speed of processing in each terminal equipment. As the plural channels, channels using different wavelengths are known, for example. As one of them, there has been proposed a multihop type in which transmitted data is relayed and transmitted in a node device interposed on the way from a signal transmitting terminal to a signal receiving or addressed terminal. Such a system is described in Biswanath Mukherjee, “WDM-Based Local Lightwave Networks Part II: Multihop Systems”, IEEE Network July (1992), p. 20-32.
SUMMARY OF THE INVENTION
An object of the present invention is, therefore, is to provide a new network system which performs communication using a plurality of channels.
Prior to the description of the present invention, a reference example will be described to facilitate understanding of the present invention. The following reference example is based on the technology described in Japanese Patent Application No. 6-327496 filed Dec. 28, 1994, and Japanese Patent Application No. 7-325632 filed Dec. 14, 1995 as a Japanese domestic priority-claim declared application based on this Japanese Patent Application No. 6-327496.
FIG. 14
, which consists of
FIGS. 14A and 14B
, illustrates a schematic diagram of a node device connected to a network system. The node device detects an optical signal at a predetermined wavelength which is transmitted on a ring-type wavelength division multiplexed transmission line, transmits a packet to its terminal equipment when the signal is the packet addressed to the terminal equipment connected to this node device concerned, and transmits other packets a packet from its terminal equipment to a next-stage node device by variable wavelength transmission means of a wavelength-circulating type which transmits signals at respective wavelengths. The node device of
FIGS. 14A and 14B
includes a control unit
149
which contains a buffer control unit
164
and a wavelength control unit
165
. The buffer control unit
164
controls the read-out of buffers such that when a packet stored in buffers
141
-
148
is addressed to a sub-transmission line connected to an adjacent node device, the read-out of the packet stored in the buffer is not performed until a transmission wavelength of the variable wavelength transmission unit for transmitting the packet coincides with a reception wavelength of a fixed wavelength reception unit for outputting the packet to a separation-insertion unit connected to the addressed sub-transmission line in the adjacent node device. The wavelength control unit
165
controls the transmission wavelengths of variable wavelength transmission units in accordance with a pattern of a predetermined transmission wavelength control table which will be described later. An optical fiber
1401
is used as an optical wavelength multiplexed transmission line. The optical fiber
1401
serves as a transmission line between a coupler in an upstream adjacent node device and a divider in an adjacent node device on the downstream side. The power divider
1402
divides an optical signal transmitted on the optical fiber
1401
into eight portions and output them to eight fixed wavelength reception units.
The fixed wavelength reception units I
117
, III
118
, V
119
and VII
120
respectively include a fixed-wavelength filter and a photodiode and serve as fixed wavelength reception means. Similarly, the fixed wavelength reception units II
121
, IV
122
, VI
123
and VIII
124
respectively include a fixed-wavelength filter and a photodiode and serve as fixed wavelength reception means. The fixed wavelength reception units I to VIII each receive only a packet which is transmitted as one of optical signals having wavelengths &lgr;
1
to &lgr;
8
. When the photodiode itself has characteristics that this is sensitive only to a predetermined wavelength, no fixed-wavelength filter is needed.
Separation-insertion units I
133
, III
134
, V
135
and VII
136
serve as separation-insertion means, each of which is operative to separate a packet, which is to be transmitted to a sub-transmission line, and a packet, which is to be transmitted to one of the buffer
145
to
148
, out of a packet stream from each of the fixed wavelength reception units
117
to
120
, while it is operative to add a packet from the sub-transmission line to the packet stream from the fixed wavelength reception unit
117
to
120
to the buffers
145
to
148
. Similarly, separation-insertion units II
137
, IV
138
, VI
139
and VIII
140
serve as separation-insertion means.
Buffers II
141
, IV
142
, VI
143
and VIII
144
serve as buffer means to temporarily store the packets from the separation-insertion units
137
to
140
in memory regions corresponding to the respective transmission wavelengths of the variable wavelength transmission units. Similarly, buffers I
145
, III
146
, V
147
and VII
148
serve as buffer means.
Variable wavelength transmission units II
125
, IV
126
, VI
127
and VIII
128
are variable wavelength transmission means, such as tunable laser diodes (TLDs), which convert, under the control of the wavelength control unit
165
, the packets from the buffers into optical signals each having a predetermined wavelength out of wavelengths &lgr;
1
to &lgr;
8
and send them through the coupler
1403
to the optical fiber
1404
used as the optical wavelength division multiplexed transmission line. Similarly, variable wavelength transmission units I
129
, III
130
, V
131
and VII
132
are variable wavelength transmission means, such as tunable laser diodes (TLDs).
In this reference example, the fixed wavelength reception unit I
117
, the separation-insertion unit I
133
, the buffer I
145
and the variable wavelength transmission unit I
129
constitute a set, and a packet received by the fixed wavelength reception unit I
117
is treated in this set but not in other sets. Similarly, the fixed wavelength reception unit II
121
, the separation-insertion unit II
137
, the buffer II
141
and the variable wavelength transmission unit II
125
constitute another set, and the other fixed wavelength reception units, the other separation-insertion units, the other buffers and the other variable wavelength transmission units respectively constitute other sets.
The coupler
1403
multiplexes the optical signals of wavelengths &lgr;
1
to &lgr;
8
which are sent from the eight variable wavelength transmission units, and supplies them to the optical fiber
1404
.
The optical fiber
1404
serves as the transmission line between the coupler in this node device concerned and the divider in a downstream adjacent node device.
Sub-transmission lines I
1405
to VIII
1412
serve as packet transmission lines between the separation-insertion units and terminal equipments. The terminal equipments I
1413
to VIII
1420
are connected to the sub-transmission lines I to VIII, respectively. Each of the terminal equipments receives a packet output from each of the corresponding separation-insertion units, while it generates a packet to be transmitted to another terminal equipment and sends it through each of the sub-transmission lines to each of the separation-insertion units.
FIG. 3
is a block diagram of a network system in which five node
Hojo Kazuhiko
Yamamoto Mitsuru
Canon Kabushiki Kaisha
Fitzpatrick ,Cella, Harper & Scinto
Lee Andy
Nguyen Chau
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