JP2003244230A - Packet switching device, and data distribution system and monitoring system including the packet switching device - Google Patents

Abstract

(57) [Summary] [Problem] To distribute data only to a required terminal, immediately stop data distribution in response to a distribution stop request from the terminal, and connect a plurality of terminals through the same network interface. The present invention provides a packet switching device that does not inadvertently stop data delivery even when the packet switching is performed. SOLUTION: A plurality of network interfaces 11-1
Has a one-to-one correspondence with the subscription status tables 15-1 to 15-4, and in response to a subscription request from the client, has the MAC address of the client as an entry.
-1 to 4 and manage the number of clients that are constantly receiving and receiving by deleting the MAC address of the corresponding client from the subscription status tables 15-1 to 15-4 in response to the stop request from the client The data distribution is stopped immediately when the number of clients becomes zero.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a packet switching device, a switch, a router, and a distribution system and a monitoring system including the packet switching device, which are mainly used in a packet switching type network using Internet Protocol (IP). .

[0002]

2. Description of the Related Art With the rapid spread of IP networks,
The demand for video distribution over IP is increasing. Multicast technology is often used in order to efficiently deliver high bit rate data such as video to a plurality of destinations. When unicast, which is a communication that uniquely identifies the destination, is used, in order to deliver video to the n destinations, it is necessary to perform n times of transmission, whereas in the case of multicast, Images can be received at n destinations with one communication.

How unicast / multicast is implemented in a switching device will be described below. Figure 4
FIG. 3 is a block diagram showing a configuration of a general exchange device.

In FIG. 4, a switching device 200 comprises a plurality of network interfaces 210 and a switching unit 220 for switching packets between them. When a unicast packet is received by a certain network interface 210, the packet is transferred and output only to the network interface 210 to which the device designated as the destination address is connected.

On the other hand, when a multicast packet is received by a certain network interface 210, the packet must be copied and output to all network interfaces 210 other than the incoming network interface 210.

However, if all the multicast data is always output to all the network interfaces 210, congestion easily occurs in the network.
The limitation of the delivery destination by the MP protocol is generally used.

Version 1 of RFC is RFC1112, Versi
on2 is defined in RFC2236.

The operation in IGMPv1 (Version 1) will be described below. In IGMPv1, "Report" and "Quer
start reception using two types of packets called "y",
Stop.

The client who wants to start reception is Report
The packet notifies the multicast address that it needs, and the switching device (router) starts copying and delivering the packet accordingly.

After that, the Qu sent by the router at regular intervals
In response to the ery packet, the client returns a Report packet. In order to avoid congestion caused by a large number of terminals returning reports at the same time, the report should be returned after a random wait time, and when it is possible to detect that another client has returned the report in the meantime. , You may cancel the return.

When the client wants to stop reception, Qu
Stop returning Report to ery. If no report is returned for multiple queries, the router stops forwarding multicast data to the corresponding network interface.

By such a method, it is possible to send the multicast data only to the necessary network interface.

[0013]

However, in the above-mentioned conventional example, since leaving is detected by the lack of Report for Query, it takes time until the client actually stops receiving and the delivery from the router is stopped. There was a problem that it took time.

In an IGMPv1 router, the normal query is 1
Since it is issued at an interval of about 0 seconds, if you follow the procedure of disconnecting after confirming that Report is not detected twice, data will continue to be delivered for 20 to 30 seconds after the client stops receiving.

In a situation where the receiving client issues a different data distribution request immediately after the reception is completed, a plurality of data are distributed for 20 to 30 seconds, which causes congestion.

In order to avoid this, IGMPv2 (Ver
sion2) newly added Group Specific Query packet and
The Leave Group packet has been added so that the client can explicitly instruct the router to stop reception. As a standard operation, the router that receives the Leave Group sends a Group Specific Query, checks if there are other clients receiving the same data multiple times, and then stops the distribution.

Although the speed has been increased in IGMPv2, confirmation is made from the stop request and the actual distribution is stopped after that, so there is still the possibility that congestion will occur between the request and the stop.

In order to speed up the delivery stop, some routers have an option called Fast Leave packet,
It is possible to stop immediately after the Leave Group. However, Fast Leave is a Group Specific Qu after receiving the Leave Group.
Since the distribution will be stopped without checking with ery, if multiple clients are receiving the same data under one network interface, one of them will be Leave Gr
There was a problem that when oup was sent, data distribution to the other side was also stopped at the same time.

The present invention has been made to solve the above-mentioned conventional problems, and distributes data only to required terminals, and immediately stops the data distribution in response to a distribution stop request from the terminals. An object of the present invention is to provide a packet switching device that does not cause an unintentional stop of data delivery even when a plurality of terminals are connected through the same network interface.

[0020]

A packet switching apparatus according to the present invention comprises a plurality of network interfaces and a switching unit for receiving packet data from the plurality of network interfaces, selecting a desired network interface, and outputting or discarding the selected network interface. Receiving a multicast join request packet from the exchange unit, and a joining state table corresponding to the network interface on a one-to-one basis,
The configuration includes a joining processing unit that adds a transmission entry to the corresponding joining state table, and a leave processing unit that receives the multicast reception end request packet from the exchange unit and deletes the transmitting entry of the corresponding joining state table.

With such a configuration, it is possible to prevent the congestion of the network by distributing the multicast data only to the required network interface and immediately stopping the distribution when the reception stop request is made. it can.

A data distribution system of the present invention comprises a packet switching device according to claim 1, at least one server for sending multicast data, and at least one client for receiving multicast data. .

With such a configuration, it is possible to avoid network congestion by distributing the data from the server only to the required clients and immediately stopping the data distribution when the distribution is stopped by the client.

Further, the monitoring system of the present invention comprises:
The packet switching device described in 1 above, at least one camera that outputs captured video, the same number of encoders that digitize the video signal from the camera and send it to the network, and decode the digitized video data. Then, at least one decoder for outputting a video signal and as many monitors as the decoder for displaying a video are provided.

With this configuration, it is possible to prevent network congestion even if a camera to be freely monitored is selected on the monitor.

[0026]

BEST MODE FOR CARRYING OUT THE INVENTION Embodiments of the present invention will be described below with reference to the drawings.

(First Embodiment) FIG. 1 is a block diagram showing a configuration of a packet switching apparatus according to a first embodiment of the present invention. In FIG. 1, the packet switching device 10 is
As its internal configuration, a plurality of network interfaces 11-1 to 11-4 for inputting / outputting packets, a switching unit 12 for exchanging packets between network interfaces,
A join processing unit 13 that receives a join request packet and adds an entry to the join state table, and a leave processing unit 15 that receives a leave request packet and deletes an entry from the join state table.
And subscription status tables 15-1 to 15-4 corresponding to the network interfaces.

As the data structure of the joining state table in this embodiment, a set of a multicast address and the MAC address of the receiving terminal is used.

The operation of the packet switching device configured as described above will be described with reference to FIG. First, the joining process will be described.

It is assumed that the multicast data of the multicast address 239.255.0.1 is received from the network interface 11-1. In this case, since there is no client that receives the multicast yet and all the subscription status tables are empty, the multicast data is not exchanged anywhere and is discarded by the exchange unit 12.

Next, the network interface 11-4
Then, it is assumed that a Report packet for the multicast address 239.255.0.1 is input from the receiving terminal with the MAC address 01: 02: 03: 04: 05: 06.

In this case, the joining state table 15-4 contains the multicast address of the multicast data being transmitted.
An entry consisting of the MAC address of the receiving terminal that sent the Report packet is registered. Specifically, 239.255.0.1
-The entry consists of a combination of 01: 02: 03: 04: 05: 06. Input from network interface 11-1
The multicast data addressed to 239.255.0.1 is 239.255.0.1
Since only the network interface in which the entry exists exists, the exchange to the network interface 11-4 is started.

In this state, the network interface
Even if the multicast data addressed to the multicast address 239.255.0.2 is input from 11-2, it is still 239.255.
No exchange occurs because there is no entry for 0.2.

Next, a case where a new reception request is input to the network interface 11-4 will be described.

It is assumed that the report packet for the multicast address 239.255.0.1 is input to the network interface 11-4 from the receiving terminal having the MAC address 11: 12: 13: 14: 15: 16. In this case, the multicast address 239.
255.0.1 data already network interface 11-
Since it is being exchanged with 4, only an entry is added to the subscription state table 15-4. As a result, the subscription state table 15-4 has two entries of 239.255.0.1-01: 02: 03: 04: 05: 06 and 239.255.0.1-11: 12: 13: 14: 15: 16. Becomes

Next, the network interface 11-4
The case where a reception request for a different cast address is input will be described.

When a Report packet for the multicast address 239.255.0.2 is input from the MAC address 21: 22: 23: 24: 25: 26 to the network interface 11-4,
239.255.0.2-21:22 for subscription status table 15-4:
At the same time as the entry having the content of 23: 24: 25: 26 is added, the exchange of the multicast data addressed to 239.255.0.2 from the network interface 11-2 to the network interface 11-4 is started. As a result, the subscription status table 15-4 shows 239.255.0.1-01: 02: 03: 04: 05: 06, 239.255.0.1-11: 12: 13: 14: 15: 16, 239.255.0.2-21:22. There are 3 entries of: 23: 24: 25: 26.

Next, the leaving process will be described.

It is assumed that a LeaveGroup packet is input to the network interface 11-4, which has already been exchanged.

In this case, the entry consisting of the multicast address being exchanged and the MAC address of the receiving terminal which has sent the Leave Group packet is deleted from the joining state table. When there is no entry for the multicast data being exchanged as a result of the deletion, it is determined that there is no other party to receive in the network interface 11-4, and the exchange is stopped. When the same multicast entry is registered more than once, the exchange is continued because the entry remains after the deletion is executed.

First, the network interface 11-4
Then, it is assumed that a Leave Group packet for the multicast address 239.255.0.2 is input from the receiving terminal with the MAC address 21: 22: 23: 24: 25: 26. In this case, the entry of 239.255.0.2-21: 22: 23: 24: 25: 26 is deleted from the subscription state table 15-4. As a result of the deletion, there is no entry related to the multicast address 239.255.0.2 in the joining state table 15-4, so that the exchange of the data addressed to 239.255.0.2 to the network interface 11-4 is stopped. The contents of the subscription status table 15-4 at this point are two entries of 239.255.0.1-01: 02: 03: 04: 05: 06, 239.255.0.1-11: 12: 13: 14: 15: 16. It becomes a state that exists.

Next, the network interface 11-4
Then, it is assumed that a Leave Group packet for the multicast address 239.255.0.1 is input from the receiving terminal with the MAC address 11: 12: 13: 14: 15: 16. In this case, the entry of 239.255.0.1-11: 12: 13: 14: 15: 16 is deleted from the subscription state table 15-4. The state of the joining state table 15-4 after execution of deletion is a state in which there is one entry of 239.255.0.1-01: 02: 03: 04: 05: 06. In this case, since the entry for the multicast address 239.255.0.1 exists even after the deletion is executed, the exchange of the data addressed to 239.255.0.1 to the network interface 11-4 is continued.

When a Leave Group packet for the multicast address 239.255.0.1 is input from the receiving terminal with the MAC address 01: 02: 03: 04: 05: 06, the multicast address 239.255.0.1 for the network interface 11-4 is addressed. Data exchange is stopped.

(Second Embodiment) The second embodiment of the present invention will be described below.
Embodiments will be described with reference to the drawings.
FIG. 2 is a block diagram showing the configuration of the data distribution system according to the second embodiment of the present invention.

In FIG. 2, the data distribution system of the present invention comprises a packet switching device 20, external networks 21-1 to 21-4 to which each network interface is connected, and a server 22 for sending multicast data to the network.
And a client 23-1 that receives the multicast data
It consists of ~ 4 and.

The operation of the data distribution system configured as above will be described. Multiple multicast data is always sent from the server 22, and each client 23-1 to 23-4 receives the data as needed, but at the beginning, all the clients are in a state of receiving nothing. And

The plurality of multicast data sent from the server 22 are received by the packet switching device 20 through the network 21-1. However, at the moment there is no client to receive the multicast data,
Since all the subscription state tables 15-1 to 4 (see FIG. 1) are empty, the multicast data is not exchanged anywhere and is discarded by the exchanging unit 12 (see FIG. 1).

Next, the client 23-1 starts receiving the first multicast data. Then, a Report packet indicating a reception start request is transmitted from the client 23-1, and reaches the packet switching device 20 via the network 21-2. Report packet is sent from the network 21-2 to the switching unit.
12 (see FIG. 1) transfers to the joining processing unit 13 (see FIG. 1), which joins the network 21-2.
The MAC address of the client is registered in the subscription state table 15-2 (see FIG. 1) corresponding to the.

Then, the multicast data from the server 22 is sent to the exchange unit 12 (see FIG. 1) in the joining state table 15-2.
By checking (see FIG. 1), it becomes clear that the client 23-1 exists in the network 21-2. Therefore, the packet switching device 20 switches to the network 21-2, and the client 23-1 passes through the network 21-2. Delivered to 1.

Next, the operation when the client 23-1 makes a distribution stop request will be described.

The client 23-1 sends a Leave Group packet at the same time when the reception is completed. The Leave Group packet is input to the packet switching device 20 via the network 21-2. The packet switching device 20 receives the input Leave Gr
Corresponding subscription status table 15-2 based on oup packet
The MAC address of the client 23-1 is deleted from (see FIG. 1). At this point, the exchange unit 12 (see FIG. 1) can determine that there is no client requesting reception of the multicast data sent from the server 22 by checking the subscription state table 15-2.
The packet exchange by (see FIG. 1) is stopped, and the switching unit 12
(See FIG. 1). As a result, the distribution of the multicast data to the clients will be stopped immediately after the reception is stopped.

Next, a case where a plurality of clients are connected under one network interface will be described.

The multicast data from the server 22 is
Initially, since there is no entry in each of the subscription status tables 15-1 to 4 (see FIG. 1), it is not output anywhere and the exchange unit
It is discarded at 12 (see Figure 1).

When a plurality of clients 23-3 and 23-4 connected to the network 21-4 make a multicast data reception request, a Report packet is input to the packet switching device 20 and the subscription state table 15-4 (see FIG. 1), the MAC addresses of the clients 23-3 and 23-4 are registered, and the exchange of multicast data to the network 21-4 is started.

Next, when only the client 23-3 stops receiving, the Leave Group packet from the client 23-3 is processed, and the MAC address of the client 23-3 is deleted from the subscription state table. However, since the MAC address of the client 23-4 is still registered at this point, the multicast data from the server 22 continues to be delivered to the client 23-4 via the network 21-4.

After that, when the client 23-4 stops receiving, the joining state table 15-4 (see FIG. 1) becomes empty, so that the exchange of multicast data to the network 21-4 is stopped.

As described above, in the data delivery system of this embodiment, even if a plurality of clients are connected to one network interface and each of them independently selects the received data, only the necessary data is delivered. However, unnecessary data can be stopped immediately when it is no longer needed.

(Third Embodiment) The third embodiment of the present invention will be described below.
Embodiments will be described with reference to the drawings.
FIG. 3 is a block diagram showing the configuration of the monitoring system according to the third embodiment of the present invention.

In FIG. 3, the monitoring system of the present invention comprises a packet switching device 30 and an external network 31-1 connected to each network interface of the packet switching device 30.
~ 4, cameras 32-1 and 32-2 that send the digitized video data to the network by multicast, and display terminals (monitors) 33-1 to 3-3 that decode and display the digitized video data. It consists of Note that FIG.
Although not shown in the figure, the same number of encoders as the cameras that digitize the video signals from the cameras 32-1 and 32-2 and send them to the network, and decode the digitized video data to output the video signals Each has a decoder.

The operation of the monitoring system of the present invention configured as described above will be described below. In FIG. 3, cameras 32-1 and 32-- connected to the external networks 31-1 and 2-2
2 digitizes the captured image by an encoder (not shown) and transmits it to the external networks 31-1 and 31-2. Although it is assumed here that MPEG2-compressed video is used, it is also possible to compress video data using a format such as DV, MPEG4, Motion-JPEG, or the like.

In transmitting to the networks 31-1 and 31-2, the cameras 32-1 and 32-2 perform multicast transmission using different multicast addresses. this is,
Video from the same camera on multiple display terminals (monitors) 33-1 to 3-3
This is to enable viewing (monitoring) with.

Video data obtained from each of the cameras 32-1 and 32-2 is encoded by an encoder (not shown) and input to the packet switching device 30 via the networks 31-1 and 2-2. Since the state tables 15-1 to 15-4 (see FIG. 1) are empty, the multicast data is not exchanged anywhere and is discarded by the exchange unit 12 (see FIG. 1).

Next, a case where the display terminals (monitors) 33-1 to 3-3 request viewing (monitoring) will be described below.

When the display terminal 33-1 makes a viewing request to the camera 32-1, the display terminal 33-1 sends a Report packet to the multicast address used by the camera 32-1. The packet switching device 30 analyzes the Report packet,
An entry consisting of the multicast address used by the camera 32-1 and the MAC address of the display terminal 33-1 is added to the joining state table 15-3 (see FIG. 1), and the video data network 31-3 of the camera 32-1 is added. To start the exchange.

Next, the display terminal 33-2 similarly displays the camera 32-1.
Entry is added to the joining state table 15-4 (see FIG. 1) corresponding to the network 31-4, and the exchange of the image of the camera 32-1 to the network 31-4 is started.

Further, the display terminal 33-3 is the same as the camera 32.
-1 is requested, an entry is added to the subscription state table 15-4 (see FIG. 1) corresponding to the network 31-4, but the image of the camera 32-1 has already been exchanged with the network 31-4. Therefore, the operating state is not changed.

Next, a process when the display terminals (monitors) 33-1 to 3-3 stop viewing and leave the viewing will be described below.

Since the display terminal 33-1 is the only display terminal requesting the image of the camera 32-1 in the network 31-3, the display terminal 33-1 stops viewing and the display terminal 33-1 is displayed. From Leav
The exchange is stopped as soon as the eGroup packet is sent.

Next, when the display terminal exchanged with the network 31-4 stops viewing and leaves the viewing, there are two display terminals receiving the same image from the camera 32-1, that is, the display terminals. Since 33-2 and the display terminal 33-3 exist,
Network 3 for sending the first Leave Group packet
The video transmission to 1-4 is not stopped, but the exchange to the network 31-4 is stopped by the transmission of the second Leave Group packet.

[0070]

As is apparent from the above description, according to the present invention, since data distribution is immediately stopped in response to a reception stop request on the terminal side, unnecessary data does not flow to the network and network congestion occurs. It has an effect that it can be prevented.

[Brief description of drawings]

FIG. 1 is a block diagram showing a configuration of a packet switching device according to a first embodiment of the present invention.

FIG. 2 is a block diagram showing a configuration of a data distribution system according to a second embodiment of the present invention.

FIG. 3 is a block diagram showing a configuration of a monitoring system according to a third embodiment of the present invention.

FIG. 4 is a block diagram showing a configuration of a conventional packet switching device.

[Explanation of symbols]

10, 20, 30 Packet switching equipment 11-1 to 11-4 Network interface 12 Exchange section 13 Subscription processing unit 14 Detachment processing unit 15-1 to 15-4 Subscription status table 21-1 to 21-4 Network 22 servers 23-1 to 23-4 Client 31-1 to 31-4 Network 32-1 to 32-2 camera 33-1 to 33-3 Display terminal 200 packet switching equipment 210 network interface 220 Exchange 260 network

Claims (3)

[Claims] 1. A plurality of network interfaces,
A switching unit that receives packet data from the plurality of network interfaces, selects a desired network interface and outputs or discards it, a subscription state table that corresponds to the network interfaces in a one-to-one correspondence, and a multicast subscription from the switching unit. A joining processing unit that receives the request packet and adds a transmission entry to the corresponding joining state table, and a leave processing unit that receives the multicast reception end request packet from the exchanging unit and deletes the transmitting entry of the corresponding joining state table. A packet switching device comprising: 2. The packet switching device according to claim 1,
A data distribution system comprising: at least one server that sends out multicast data; and at least one client that receives the multicast data. 3. The packet switching device according to claim 1,
At least one camera that outputs the captured video, as many encoders as the cameras that digitize the video signal from the camera and send it to the network, and at least output the video signal by decoding the digitized video data. A surveillance system comprising one decoder and the same number of monitors as the decoders for displaying video.