JP2001136175A - Packet switch - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a packet switch that transmits packets from one input module to a plurality of difference output ports. SOLUTION: The one input module outputs the packets simultaneously to a plurality of the output ports through the use of wavelength multiplex processing of optical signals.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a packet switch applied to a packet switching system such as an ATM switch or a router, and more particularly, to a packet switch having a buffer corresponding to an output port on the input side and performing transfer. Regarding the transmission method.

[0002]

2. Description of the Related Art In a conventional packet switch having a virtual output buffer, a buffer corresponding to an output port is arranged at an input port to improve the problem of HOL (Head of Line brocking) of an input buffer type packet switch. It has become.

[0003] This conventional example will be described with reference to FIGS. 8 and 9. FIG. 8 is a block diagram of a conventional packet switch. The destination ports of the packets arriving at the input modules 1-1 to N are read by the destination determination unit 2, and the virtual output buffer 3-1 corresponding to the output port is determined based on the destination.
And transmission control signals for requesting permission of packet transmission from the transmission control units 4-1 to M provided for each virtual output buffer to the contention control units 5-1 to M at the output ports, respectively. From the packets destined for the same output port in the time slot, one packet that is permitted to be transmitted to the output port is selected and a transmission permission signal is transmitted to the transmission control units 4-1 to M of the input modules 1-1 to N. return.

[0004] At this time, if transmission of a plurality of packets in a specific input module is permitted, a packet is selected by the transmission packet selecting unit 16 from the permitted packets and transmitted to the electrical switching fabric 7. And is switched to the output port. As a packet switch using this configuration, a document "McKeown, N .; Izza
rd, M.; Mekkittikul, A.; Ellersick, W.; Horowitz, M.: "AP
acket switch core ”IEEE Micro vol.107 1, PP.26-303,
There is a packet switch as proposed in Tiny Tera Jan.-Feb. 1997.

FIG. 9 is a diagram showing a contention control algorithm of the conventional packet switch shown in FIG. In a certain time slot, an arbitrary plurality of input modules 1-1
When a plurality of packets are present in the virtual output buffers 3-1 to M in the virtual output buffers 3-1 to M, the request signals are transmitted from the transmission control units 4-1 to M in the respective virtual output buffers 3-1 to M. Then, the contention control units 5-1 to M receiving the request signals from the plurality of input modules 1-1 to N perform the contention control and transmit the request signals to the transmission control units 4-1 to M of the input ports that permit the selected transmission. Returns the permission signal. Input module 1-1 that has received a transmission permission signal from a plurality of output ports
The transmission packet selecting unit 16 in the input modules 1-1 to M further selects one transmission packet and transmits the packet to the electrical switching fabric 7.

[0006]

Since such a conventional virtual output buffer type packet switch has a structure in which an electric switch is arranged in a switching fabric, the switching fabric requires one time from one input module. One packet is transmitted to each slot. Therefore, even if there is a packet selected by contention control between packets of different input modules aiming at the same output port in a certain time slot, another packet in the same input module is selected as a transmission packet to a different output port. In such a case, there is a problem that only one of the packets can be transmitted.

The present invention has been made in view of such a background, and an object of the present invention is to provide a packet switch capable of simultaneously transmitting packets to a plurality of different output ports from the same input module. An object of the present invention is to provide a packet switch that can obtain high throughput.

[0008]

SUMMARY OF THE INVENTION The present invention uses wavelength division multiplexing of optical signals by using an optical device instead of a configuration in which an electric switch is arranged in a switching fabric of a conventional virtual output buffer type packet switch. It is characterized in that a packet can be simultaneously output from an input module to a plurality of output ports.

The packet switch of the present invention buffers an electric signal packet in a virtual output buffer corresponding to each output port based on the destination address of the electric signal packet arriving at the input module, and stores the electric signal packet in each virtual output buffer. The signal is converted into an optical signal packet of the assigned optical wavelength and output, and the packet is sent to a means for multiplexing the wavelength and distributing the packet to a predetermined output port for each wavelength. The distributing means distributes the optical signal packet to which each wavelength is allocated to the corresponding output port.
The output port may output the optical signal packet as it is to the optical communication network, or may perform optical-electric conversion for converting the optical signal packet into an electric signal packet and output the packet to the telecommunication network.

The distribution means may be realized by a wavelength router, or a star coupler for broadcasting an optical signal packet to an output port is used, and only the optical signal packet of the wavelength representing the output port is used for the output port. A wavelength filter for selection may be provided. Alternatively, an optical bus can be used instead of the star coupler. This optical bus may be of a ring type.

That is, the present invention provides M virtual output buffers in which electric signal packets are stored in correspondence with M output ports, a packet transmission request signal for each virtual output buffer, and a response signal to the request signal. Receiving a packet transmission request signal from the virtual output buffer of each of the N input modules including a transmission control unit for controlling the packet transmission by receiving the packet and the N different input modules aiming at the same destination output port. A packet switch comprising: M contention control units for transmitting a response signal to the transmission control unit in the input module selected by performing contention control.

Here, the feature of the present invention is that an electro-optical converter for converting an electric signal packet output from the virtual output buffer into an optical signal packet having a wavelength assigned to a destination output port, There is a wavelength multiplexing unit that multiplexes M wavelengths output from the optical conversion unit, and a unit that distributes an optical signal packet transmitted from the input module to an output port according to the wavelength.

[0013] The distributing means may be configured to include an N-input M-output wavelength router. In this way, the electrical signal packet buffered in the virtual output buffer is converted into an optical signal packet to which a wavelength is assigned for each destination, and when there are a plurality of packets, the optical signal packet is multiplexed and sent to the wavelength router. As a result, packets can be transferred from the same input module to different output ports in the same time slot.

[0014] The distributing means includes a star coupler for wavelength-multiplexing and transmitting an optical signal packet transmitted from a different one of the input modules to all the output ports, and a wavelength-multiplexed optical signal transmitted from the star coupler. It is also possible to provide a configuration including M wavelength filters that select and transmit only optical signal packets of the wavelength representing the corresponding output port from the signal packets and discard packets of other wavelengths.

Thus, the electric signal packet buffered in the virtual output buffer is converted into an optical signal packet to which a wavelength is assigned for each destination. In the output port, only a specific wavelength representing the output port is selected by the wavelength filter, and packets of other wavelengths can be discarded.

Alternatively, the distributing means includes an optical bus, a coupler for flowing an optical signal packet from each input module to the optical bus, and an optical signal packet of a corresponding wavelength from the wavelength-multiplexed optical signal packet in the optical bus. A configuration including a wavelength filter to be selected may be adopted.

Thus, the electric signal packet buffered in the virtual output buffer is converted into an optical signal packet to which a wavelength is assigned for each destination, and when there are a plurality of packets, wavelength multiplexing is performed and the optical signal packet is transmitted to the optical bus. At the output port, only a specific wavelength representing the output port is selected by the wavelength filter at the output port, and optical signal packets of other wavelengths are not selected. This optical bus can be a ring-type optical bus.

When transmitting a packet to an optical communication network,
When transmitting an optical signal packet as it is and transmitting the packet to a telecommunications network, the optical signal packet may be converted into an electric signal packet and transmitted.

[0019]

DESCRIPTION OF THE PREFERRED EMBODIMENTS (First Embodiment) A first embodiment of the present invention will be described with reference to FIG. FIG. 1 is a block diagram of a packet switch according to the first embodiment of the present invention.

According to the present invention, as shown in FIG. 1, M virtual output buffers 3-1 to M for storing electric signal packets corresponding to M output ports, and each virtual output buffer 3-M.
N input modules 1 comprising transmission control sections 4-1 to M for transmitting packet transmission request signals 1 to M, receiving response signals to the request signals, and controlling packet transmission.
1 to N and virtual output buffers 3-1 to M of N different input modules 1-1 to N aiming at the same destination output port
Control unit 4-1 in the selected input module 1-1 to N which receives the packet transmission request signal from
-M contention control units 5-1 transmitting the response signal to.
~ M.

Here, a feature of the present invention is that an electro-optical converter converts an electric signal packet output from the virtual output buffer 3-1 to M into an optical signal packet having a wavelength assigned to a destination output port. 6-1 to M, a wavelength multiplexing unit 37 for multiplexing M wavelengths output from the electro-optical conversion units 6-1 to M, and an optical signal packet transmitted from the input module 1-1 to N. And an N-input M-output wavelength router 38 for routing to an output port corresponding to the above.

Next, the operation of the packet switch according to the first embodiment of the present invention will be described. The destination signals of the electric signal packets arriving at the input modules 1-1 to N are read by the destination determining unit 2, and are buffered in the virtual output buffers 3-1 to M corresponding to the output ports based on the read destination addresses. Further, each of the virtual output buffers 3-1 to M has a transmission control unit 4-1 to M. When the electric signal packets are buffered in the virtual output buffers 3-1 to M, transmission is desired. To the contention control units 5-1 to M.

When one request signal arrives at the contention control units 5-1 to M in a certain time slot, the request signals are transmitted to the transmission control units 4-1 to M of the input modules 1-1 to N that transmitted the request signals. Send a signal to allow transmission. A plurality of request signals are sent to the contention control unit 5 in a certain time slot.
When it arrives at -1 to M, the contention control unit 5-1 to M selects an input module to which transmission is permitted, and sends a signal to permit transmission to the transmission control unit 4-1 to M of the input module. . The input modules 1-1 to M transmit the electric signal packets having received the transmission permission signal to the wavelength router 38 as optical signal packets in which the wavelengths representing the corresponding output ports are assigned by the electro-optical converters 6-1 to M, respectively. Send out.

When a transmission permission signal is sent to a plurality of transmission control units 4-1 to M in the input modules 1-1 to M, the optical signals to which the wavelengths are assigned by the electro-optical converters 6-1 to M are transmitted. The signal packet is multiplexed by the wavelength multiplexing unit 37 and sent out to the wavelength router 38 in the same time slot. The wavelength router 38 sends out to the output port corresponding to each wavelength. The optical signal packet assigned to the wavelength sent to the output port is converted into an electric signal packet by the optical-electrical converters 9-1 to M and transmitted to the link. At this time, each of the input modules 1-1 to N
It is assumed that the transmission control units 4-1 to M and the contention control units 5-1 to M are synchronized with each other and different input ports.

FIG. 2 shows the input / output relationship in the configuration of the N × N wavelength router in FIG. FIG.
N × where the number of output ports is larger than the number of input ports in
The input / output relationship in the configuration of the M (M> N) wavelength router is shown.

The configuration of such a wavelength router is described in the document “Takah
ashi, H., Suzuki, S., Kato, K., Nishi, i.,: ”Arrayed-Wave
guide grating for wave length division multi / demul
tiplexer with nanometer resolution ”Electron.Let
t., 1990, 26, pp. 87-88 ".

In the wavelength router, the input port number i (1 ≦ 1)
i ≦ N) and the output port number j (1 ≦ j ≦ M) are uniquely determined. Therefore, by using a wavelength router, one input module can be connected to a plurality of output ports in a certain time slot. Enables packet transmission.

(Second Embodiment) The configuration of a packet switch according to a second embodiment of the present invention will be described with reference to FIG. FIG. 42 is a block diagram of the packet switch according to the second embodiment of the present invention.

In the second embodiment of the present invention, a star coupler 6 for wavelength-multiplexing and transmitting optical signal packets transmitted from different input modules 1-1 to N to all the output ports is provided.
8 and select and transmit only the optical signal packet of the wavelength representing the corresponding output port from the wavelength-multiplexed optical signal packets sent from the star coupler 68, and discard the optical signal packets of other wavelengths. Wavelength filters 69-1 to 69-M.

Next, the operation of the packet switch according to the second embodiment of the present invention will be described. For the electric signal packets arriving at the input modules 1-1 to N, the destination address of the electric signal packet is read by the destination determining unit 2, and is buffered in the virtual output buffers 3-1 to M corresponding to the output ports based on the read addresses. You. Further, each virtual output buffer 3-
1 to M include transmission control units 4-1 to M, and when the electric signal packets are buffered in the virtual output buffers 3-1 to M, transmit the transmission request signal desired to be transmitted to the contention control unit 5-1. -1 to M. When one transmission request signal arrives at the contention control units 5-1 to M in a certain time slot, the transmission is permitted to the transmission control units 4-1 to M of the input module that transmitted the transmission request signal. Send a signal. A plurality of transmission request signals are sent to the contention control unit 5-
When they arrive at 1 to M, the contention control units 5-1 to M select an input module for which transmission is permitted, and send a signal for permitting transmission to the transmission control units 4-1 to M of the input module.

In the input modules 1-1 to N, the electric signal packets which have received the transmission permission signal are converted into optical signal packets in which the wavelengths representing the output ports corresponding to the respective electro-optical converters 6-1 to M are assigned. Send to coupler 68. When the transmission permission signal is sent to the plurality of transmission control units 4-1 to M in the input modules 1-1 to M, the optical signal packets to which the wavelengths are assigned by the electro-optical converters 6-1 to M are transmitted. The signals are multiplexed by the wavelength multiplexing unit 37 and sent to the star coupler 68 in the same time slot. The star coupler 68 multiplexes wavelengths and broadcasts optical signal packets to all output ports. The wavelength-multiplexed optical signal packet sent to the output port is transmitted to the wavelength filters 69-1 to 69-1.
At M, only the optical signal packet of the corresponding wavelength is taken out, converted into an electric signal packet by an optical-electrical converter and transmitted to the link, and the optical signal packets of the remaining wavelengths are discarded.

As described above, the second embodiment of the present invention makes it possible to transmit a packet from one input module to a plurality of output ports in a certain time slot by using the star coupler 68.

(Third Embodiment) The configuration of a packet switch according to a third embodiment of the present invention will be described with reference to FIG. FIG. 5 is a block diagram of a packet switch according to the third embodiment of the present invention.

The packet switch according to the third embodiment of the present invention shown in FIG. 5 is different from the packet switch shown in FIG.
This is a configuration using an optical bus 78. Transmittable electric signal packets are merged into optical buses 78 using couplers 79-1 to 79-N as optical signal packets to which wavelengths representing output ports are assigned, and only optical signal packets of the corresponding wavelengths are wavelength-filtered 69-1 to 69-2. The signal is selected by M, converted into an electric signal packet by the photoelectric converters 9-1 to M, and transmitted to the link.

(Fourth Embodiment) The configuration of a packet switch according to a fourth embodiment of the present invention will be described with reference to FIG. FIG. 6 is a block diagram of a packet switch according to a fourth embodiment of the present invention.

A packet switch according to a fourth embodiment of the present invention shown in FIG. 6 is different from the packet switch shown in FIG.
This is a configuration using a ring-type optical bus 88. At the output port, only the optical signal packet of the corresponding wavelength is selected by the wavelength filters 69-1 to 69-M, converted into an electric signal packet by an optical-electrical converter, and transmitted to the link.

(Summary of Embodiment) FIG. 7 is a diagram showing a competition control algorithm according to the first to fourth embodiments of the present invention. In a certain time slot, an arbitrary plurality of input modules 1
When a plurality of electric signal packets exist in the virtual output buffers 3-1 to M in -1 to N, the transmission control units 4-1 to M in the respective virtual output buffers 3-1 to M A transmission request signal is transmitted, and a plurality of input modules 1-1 are transmitted.
-N receiving the transmission request signal from N to N
Returns the transmission permission signal to the transmission control units 4-1 to M of the input ports that perform the conflict control and permit the selected transmission. Unlike the case of FIG. 9, the input module receiving the transmission permission signals from the plurality of output ports assigns different wavelengths to the corresponding packets and transmits the packets to the wavelength router 38, the star coupler 68, the optical bus 78, and the ring type optical bus 88. Therefore, it is possible to transmit a plurality of packets from one input module 1-1 to N in one time slot, and it is possible to suppress the average packet delay.

At this time, when the output port is linked to the optical communication network, the optical signal packet is transmitted to the optical communication network as it is, and when the output port is linked to the telecommunication network, the optical signal packet is transmitted. The packet is converted into an electric signal packet and transmitted to a telecommunication network.

[0039]

As described above, according to the present invention,
Packets can be transmitted from the same input module to a plurality of different output ports. Thereby, a high throughput can be obtained.

[Brief description of the drawings]

FIG. 1 is a block diagram of a packet switch according to a first embodiment of the present invention.

FIG. 2 is a diagram showing an input / output relationship in a configuration of an N × N wavelength router.

FIG. 3 shows that N × the number of output ports is larger than the number of input ports.
The figure which shows the input-output relationship in the structure of the wavelength router of M (M> N).

FIG. 4 is a block diagram of a packet switch according to a second embodiment of the present invention.

FIG. 5 is a block diagram of a packet switch according to a third embodiment of the present invention.

FIG. 6 is a block diagram of a packet switch according to a fourth embodiment of the present invention.

FIG. 7 is a diagram showing a contention control algorithm of the packet switch according to the first to fourth embodiments of the present invention.

FIG. 8 is a block diagram of a conventional packet switch.

FIG. 9 is a diagram showing a contention control algorithm of a conventional packet switch.

[Explanation of symbols]

 1-1 to N input module 2 destination determination unit 3-1 to M virtual output buffer 4-1 to M transmission control unit 5-1 to M competition control unit 6-1 to M electro-optical conversion unit 7 electric switching fabric 9- 1 to M photoelectric conversion unit 16 transmission packet selection unit 37 wavelength multiplexing unit 38 wavelength router 68 star coupler 69-1 to M wavelength filter 78 optical bus 79-1 to N coupler 88 ring type optical bus

 ────────────────────────────────────────────────── ─── Continuing on the front page (72) Inventor Keishi Habara 2-3-1 Otemachi, Chiyoda-ku, Tokyo F-term in Nippon Telegraph and Telephone Corporation (reference) 5K002 BA04 BA05 BA06 DA02 DA05 DA10 DA11 DA12 FA01 5K030 HA08 KA03 KX12 KX20 LA17 LC14

Claims (5)

[Claims] 1. An M number of virtual output buffers in which electric signal packets are stored corresponding to the M output ports, a packet transmission request signal of each virtual output buffer is transmitted, and a response signal to the request signal is received. N input modules each including a transmission control unit for controlling packet transmission, and a packet transmission request signal from the virtual output buffer of each of the N different input modules aiming at the same destination output port. A packet switch comprising: M contention control units for transmitting a response signal to the transmission control unit in the selected input module; wherein the electric signal packet output from the virtual output buffer is assigned to a destination output port. And an M-wavelength output from the electro-optical converter. A packet switch comprising: a wavelength multiplexing unit; and a unit that distributes an optical signal packet transmitted from the input module to an output port according to a wavelength. 2. The packet switch according to claim 1, wherein said distribution means comprises an N-input M-output wavelength router. 3. A star coupler for wavelength multiplexing optical signal packets transmitted from different input modules to all the output ports for transmission, and a wavelength multiplexed light transmitted from the star coupler. 2. The packet switch according to claim 1, further comprising: M wavelength filters for selecting and transmitting only optical signal packets having a wavelength representing the corresponding output port from the signal packets and discarding optical signal packets having other wavelengths. 4. An optical bus, an optical bus, a coupler for flowing an optical signal packet from each input module to the optical bus, and an optical signal packet of a corresponding wavelength from the wavelength multiplexed optical signal packet in the optical bus. 2. The packet switch according to claim 1, further comprising a wavelength filter to be selected. 5. The packet switch according to claim 4, wherein said optical bus is a ring type optical bus.