JP2001244938A - Distributed selective communication control method, node device and distributed selective communication network - Google Patents

Abstract

PROBLEM TO BE SOLVED: To shorten delay time caused by path setting processing and to sup press call setting traffic by efficiently exchanging label information when provid ing a multiaddress distribution service in a distributed selective communication network. SOLUTION: When providing the multiaddress distribution service, the label information identifying broadcasting data is distributed from a transmitting node device to each node device and in a receiving node device, the label information is received. When the device is to participate in the multiaddress distribution service corresponding to that label information, the broadcasting data corresponding to that label information is received by setting to a label extracting part. When the device is not to participate in the multiaddress distribution service corresponding to that label information, that label information is stored without setting to the label extracting part. When the device is participate in the multiaddress distribution service later, the correspondent broadcasting data are received by performing setting to the label extracting part while using the stored label information.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

[0001] The present invention relates to a method for efficiently performing broadcast communication in a network in which there are many senders who want to broadcast information (multicast) and there are many receivers who want to receive the information. The present invention relates to a distribution selection type communication control method, a node device, and a distribution selection type communication network that are frequently performed.

[0002]

2. Description of the Related Art In recent years, the cost of video cameras and personal computers has been reduced and the operability has been improved, so that these devices have been widely used. Also, by interconnecting such devices to a wide area network via the Internet, each individual can distribute information at low cost. Here, the information to be distributed has evolved to be more attractive in combination with recent rapid technological innovation. For example, initially, information distribution using only characters such as e-mail and net news was mainly performed, but with the advent of the WWW browser, distribution of multimedia data such as images, sounds, and moving images has increased. Until now, delivery of storage-type data has been mainly performed, but recently, delivery of immediate-type multimedia data has become possible.

[0003] Such a tendency is expected to be further expanded in the future, and it is considered that it becomes possible to deliver a video of about broadcast quality in an immediate manner. In such a situation, it is expected that the need for a broadcast distribution service for distributing video information and the like to a large number of people will increase.

[0004] At present, methods for broadcasting (multicasting) information to a large number of people include, for example, terrestrial broadcasting and satellite broadcasting using radio, and CATV using optical fibers and coaxial cables. In these systems, it is possible to broadcast information to a very large number of recipients. However, in such a distribution form by broadcasting, it is difficult to completely cope with an unspecified large number of demands because the number of channels to be provided is limited.

On the other hand, in the field of communication, a one-to-one type high-speed communication environment has been prepared by utilizing the broadband property of an optical fiber. The Internet has evolved in this context and has surpassed traditional telephone traffic. However, in the current communication network designed on the assumption of one-to-one connection, there is a problem that the load on the node device and the link increases and the management becomes complicated, so it is difficult to cope with the increase of the broadcast communication. there were.

On the other hand, an optical signal transmitted from a node device is distributed to another node device directly connected via an optical coupler, and is assigned such that the transmission wavelength differs for each node device. There is a distribution-selection type communication network that extracts arbitrary data by wavelength selection in a node device. This has a feature that the copy processing in the node device is unnecessary, and that the traffic in the unit network does not depend on the number of receivers, and the load on the node device and the link load can be reduced and the management complexity can be suppressed. Therefore, it is expected as a communication network suitable for broadcast communication.

In recent years, MPLS (Multi-Protocol L)
The technology called abel Switching) is attracting attention. This is a protocol positioned as an intermediate layer between the data link layer and the network layer, and refers to and exchanges fixed-length labels (identifiers) between transfer nodes to transfer data packets to a destination node. is there. As compared with the conventional Internet technology, advantages are that traffic control can be easily realized, and a new routing protocol can be implemented without changing the conventional routing protocol. However, no one-to-many communication has been optimized.

[0008]

In order to realize a broadcast service such as a current television, a call is promptly and reliably established in a process of participating in the broadcast service such as switching of a television channel. Configuration must be completed. This minimizes path setup delays as much as possible,
In addition, it indicates that it is necessary to minimize the rejection of the call request acceptance as much as possible. It is also desirable that the traffic at the time of setting be small.

The above-described MPLS technology is designed on the basis of a one-to-one communication network in which each node is connected in pairs. For this reason, when participating in the broadcast service, it is necessary to exchange and update label information between the transmitting node device and the receiving node device. An increase in traffic becomes a problem. When setting a path, a setting process is required between the transmitting node device and the receiving node device in response to a setting request from a user.
The call request cannot be processed completely, and acceptance rejection is likely to occur.

[0010] The present invention takes advantage of the characteristics of a distribution-selection type communication network for distributing an optical signal transmitted from a node device to a plurality of node devices, efficiently exchanges label information at the time of providing a broadcast distribution service, and It is an object of the present invention to provide a distribution-selection-type communication control method, a node device, and a distribution-selection-type communication network that can reduce the delay time required for the setting process and suppress the call setting traffic.

[0011]

According to the present invention, there is provided a distribution-selection-type communication control method and a node device according to the present invention, in a distribution-selection-type communication network in which an optical signal transmitted from each node device is distributed to a plurality of node devices. Desired data is extracted by referring to the label of the received signal in the label extracting unit of the device. On the other hand, when providing a broadcast service, label information for identifying broadcast data is distributed to each node device from the label information distribution means of the transmitting node device. The label information processing means of the receiving node device receives the label information, sets it in the label extracting unit when participating in the broadcast distribution service corresponding to the label information, and receives the broadcast data corresponding to the label information. I do. On the other hand, if the user does not participate in the broadcast service corresponding to the label information, the label information is stored without performing the setting to the label extracting unit.

Thereafter, when participating in this broadcast service, the label information setting means uses the already stored label information to promptly send the label to the label extracting unit without performing communication with the transmitting node device. Set and receive the corresponding broadcast data.

A distribution-selection type communication network according to the present invention is constructed using such a distribution-selection type communication control method and a node device. Label information for identifying broadcast data is transmitted to all node devices. If the node device receiving the label information sets or accumulates it in the label extracting unit and later participates in the broadcast service,
In this configuration, the receiving node device uses the stored label information without exchanging the label information with the transmitting node device.
As a result, it is possible to reduce the delay time required for the path setting processing when providing the broadcast service and to suppress the call setting traffic.

[0014]

FIG. 1 shows an embodiment of a distribution-selection type communication network according to the present invention. In the figure, each node device 1-1
1 to 1-n are connected to each other via the optical fiber transmission lines 2-1 to 2-n and the optical coupler 3. One or a plurality of user terminals 4 are connected to each node device. Here, assuming that the transmission wavelengths of the respective node devices 1-1 to 1-n are respectively λ1 to λn, the optical signals of the respective wavelengths transmitted from the respective node devices are wavelength-multiplexed by the optical coupler 3 and distributed. , Wavelengths λ1 to λn
Is received. In the present embodiment, a star communication network in which distribution is performed by the optical coupler 3 has been described. However, the same applies when a ring communication network in which each node device is connected to a ring fiber is used, and the network topology is limited. Not something.

In each node device, the optical signals from all the node devices are wavelength-multiplexed and received. Therefore, the optical signals are demultiplexed into optical signals of each wavelength using an optical demultiplexer, and each of them is subjected to opto-electric conversion. Convert to electrical signals. The data converted into the electric signal is input to the label extracting unit, and the desired data is extracted by referring to the label, and other data is discarded. That is,
Each node device fetches all data distributed in the network to the label extracting unit regardless of whether data is required or not.

FIG. 2 shows an example of a label information storage field. Although the present invention does not limit the protocol, here, ATM (Asynchronous Transfer Mode) is used as a layer 2 protocol at the time of broadcast data distribution.
IP (Internet Protocol) is used as the layer 3 protocol, and D is used as the multicast routing protocol.
VMRP (Distance Vector Multicast Routing Protocol)
ol).

The ATM cell format includes a header section and a payload section, and the header section includes VPI (virtual path identifier), VCI (virtual channel identifier), PT
(Payload type), CLP (cell loss priority indication),
It consists of HEC (Header Error Control) fields. Label information is described in the VCI field in the ATM header. The usage of other fields is not particularly defined in the present embodiment.

FIG. 3 shows an embodiment of the node device of the present invention. In the figure, an optical signal transmitted from each node device and wavelength-multiplexed by an optical coupler is received by a receiving unit 11 and demultiplexed by an optical demultiplexer 12 into optical signals of wavelengths λ1 to λn.
The optical signals of the respective wavelengths λ1 to λn are
The signals are converted into electric signals by 3-1 to 13-n and input to the label extracting units 14-1 to 14-n. A label to be extracted is set in each label extraction unit under the control of the node control unit 15, and necessary data is extracted and other data is discarded. The data extracted by the label extracting unit is transmitted to the accommodated user terminal via the ATM cell assembling unit 16 and the data transmitting unit 17. The default transfer path described later connects the ATM cell assembling unit 16 and the data transmitting unit 17 via the IP routing unit 18.

The data transmitted from the user terminal is received by the data receiving unit 19 and input to the IP routing unit 18. The IP routing unit 18 includes the node control unit 1
5 and the ATM cell dividing / labeling unit 20 are connected, and the ATM cell dividing / labeling unit 20 generates a transmission signal under the control of the node control unit 15. The database 21 is connected to the node control unit 15. The transmission signal is
The light is converted into an optical signal by the electro-optical converter 22 and transmitted from the transmission unit 23.

FIG. 4 shows logical paths established between node devices. There are three types of logical paths: a control signal transfer path, a default transfer path, and a dedicated path for each flow, and are logically divided by different labels described in the ATM header. The control signal transfer path is a path for transferring a control signal, the dedicated path for each flow is a dedicated path set for each data flow, and the default transfer path is a path for transferring a data flow for which no dedicated path is set. It is.

Here, a method of setting a dedicated path for each flow will be described with reference to the configuration of the node device in FIG. 3 and FIGS. 5 and 6. FIG. 5 shows the flow of a control signal used by a receiving node device that participates in a certain multicast flow from the beginning. FIG. 6 shows the flow of a control signal used by a receiving node device that joins a certain multicast flow later.

The DVMRP flooding packet and the like are transferred to each node device using the default transfer path without setting a dedicated route. The data distributed via the default transfer path is transferred to the accommodated user device via the IP routing unit 18. Here, when it is detected that the transmission of the broadcast data is performed on the default transfer path for a predetermined time or more, or when it is detected that the new IP multicast address is registered in the routing table, the broadcast distribution service is started. Detect as participation.

Upon detecting participation in the broadcast service, the node control unit 15 of the receiving node device transmits a label request message to the transmitting node device shown in FIG.
Note that the label request message, the label notification message, and the response message described below are transferred between the node devices via the control signal transfer path shown in FIG. Upon receiving the label request message, the transmitting node device transfers the label request message to the node control unit 15 via the IP routing unit 18, determines the label information corresponding to the multicast packet, sets the label information in the ATM cell division / label assignment unit 20, A label notification message for notifying the label information is transmitted to all node devices.

In general, in a label switching system, the number of labels that can be assigned is limited.
There is a problem of lack of scalability as the number of flows increases. On the other hand, in the configuration of the distribution-selection communication network of the present invention, the transmitting node device can be identified by the wavelength on the receiving side.
The label value can be determined independently by each transmitting node device, and the label space (the number of labels that can be assigned) becomes a multiple of the normal wavelength. Therefore, the number of labels can be extended.

In the present invention, the label information corresponding to the broadcast data is notified to all the node devices regardless of whether the label information is necessary or unnecessary. Accordingly, in the node device that has received the label information, when participating in the broadcast service corresponding to the label information, the node control unit 15 sets the label information in the label extraction unit 14. Then, the response message is transmitted to the transmitting node, and the setting of the dedicated path for each flow between the transmitting and receiving node devices is completed. Thereafter, this data flow is distributed on a flow-specific dedicated path identified by the label.

In the node device participating in the broadcast service, the data extracted by referring to the label described in the header by the label extracting unit 14 is sent to the ATM cell assembling unit 16, where it is converted into an IP packet. It is configured and transferred directly to the data transmission unit 17.

On the other hand, a node device that does not participate in the broadcast service does not set the notified label information in the label extracting unit 14 and discards the received data. Here, the node control unit 15 of the node device that does not need the label information,
This label information is stored in the database 21. Thereby, when participating in the broadcast distribution service later, even if the label request message is not transmitted to the transmitting node device to acquire the label information, as shown in FIG. It is sufficient to inquire the label information and set the read label information in the corresponding label extracting unit 14. Thereby, the setting of the dedicated path for each flow between the transmitting and receiving node devices is completed.

As described above, according to the present invention, even when participating in the broadcast service later, it is possible to acquire label information for participating in the broadcast service without exchanging messages with the transmitting node device. It is possible to reduce the delay time required for the path setting processing and suppress the call setting traffic. Further, since the number of setting processes is also reduced, it is possible to suppress an increase in path setting delay time due to concentration of setting requests.

FIG. 7 shows the calculation results of the average label request message occurrence count and the path setting delay time. The calculation model is shown below. In the configuration of the distribution selection type communication network of FIG.
Assuming that an equal number of multicast flows are transmitted from each node device, the distribution of the number of participants in each flow is equal, and a Poisson distribution with an average of n is used. Also, it is assumed that the flow is received with equal probability in all node devices. Here, the path setting delay is calculated by dividing the ATM cell division /
The label request message depends on only the setting delay in the label assigning section 20 and the label extracting section 14, and the label request message is
It was assumed to be processed by FO. This setting waiting system is modeled by M / D / 1, and the setting processing time is 30 [msec].
And The number of node devices was 10.

Under such a model, a configuration based on the distribution-selection type communication network according to the present invention was compared with a conventional configuration for transmitting a label request / notification message by a unicast method in a one-to-one connection network. . FIG.
Then, the average number of flow participants n was used as a parameter (n =
10, 50). It can be seen that when the number of participants n is small, the configuration of the present invention can significantly reduce the path setting delay time for more reception requests as compared with the conventional configuration. The reason will be described with reference to FIGS.

FIG. 8 shows a case where only one receiving terminal for a certain multicast flow exists in each receiving node. In the case of the configuration of the present invention in which the transmitting and receiving nodes are connected via the optical coupler 3, as described with reference to the sequences of FIGS. On the other hand, in the conventional configuration in which the transmitting and receiving nodes are connected by each link, setting work at the transmitting node is required for each link, so the setting request for the transmitting node increases according to the number of receiving nodes, and as a result, the path setting is performed. Delay time increases. This corresponds to the calculation result when the average number of participants n is 10 in FIG.

FIG. 9 shows a case where two or more receiving terminals for a certain multicast flow exist in each receiving node. It is assumed that, from the case of FIG. 8, when the number of participants per receiving node to the flow increases, the result becomes as shown in FIG. For a newly joining receiving terminal, since a dedicated path for each flow between the transmitting and receiving nodes has already been set, only setting of the connected receiving node is sufficient. For this reason, as the number of receiving terminals for a certain flow per receiving node increases, the number of times set in the transmitting node in the case of the conventional configuration approaches that of the configuration of the present invention. For this reason, the path setting delay time characteristic of the conventional configuration gradually approaches the characteristic of the present invention configuration. This corresponds to the calculation result when the average number of participants n is 50 in FIG.

Therefore, it can be said that the distribution-selection type communication network of the present invention functions effectively in an environment where there are many multicast flows having a relatively small number of participants.

[0034]

As described above, according to the present invention, a distribution-selection type communication network for connecting a transmitting node device and a plurality of receiving node devices is formed. One setting is sufficient for the distribution service.

Further, when providing a broadcast distribution service, label information for identifying broadcast data is distributed to all the node devices, and the node device that has received the label information sets the label extraction unit. If the receiving node device participates in the broadcast service later, it can use the stored label information without exchanging the label information with the transmitting node device. This allows
It is possible to reduce the delay time required for the path setting process when providing the broadcast service and to suppress the call setting traffic. Also, since the number of setting processes is reduced,
It is possible to suppress an increase in path setting delay time due to concentration of setting requests.

[Brief description of the drawings]

FIG. 1 is a diagram showing an embodiment of a distribution-selection type communication network of the present invention.

FIG. 2 is a diagram showing an example of a label information storage field.

FIG. 3 is a block diagram showing an embodiment of the node device of the present invention.

FIG. 4 is a diagram showing logical paths set between node devices.

FIG. 5 is a diagram showing a flow of a control signal used by a receiving node device which participates in a certain multicast flow from the beginning.

FIG. 6 is a diagram showing a flow of a control signal used by a receiving node device that later joins a certain multicast flow.

FIG. 7 is a diagram showing a calculation result of an average label request message occurrence count and a path setting delay time.

FIG. 8 is a diagram showing a case where there is only one receiving terminal for a certain multicast flow in each receiving node.

FIG. 9 is a diagram showing a case where two or more receiving terminals for a certain multicast flow exist in each receiving node.

[Explanation of symbols]

 Reference Signs List 1 node device 2 optical fiber transmission line 3 optical coupler 4 user terminal 11 receiving unit 12 optical demultiplexer 13 photoelectric converter 14 label extracting unit 15 node control unit 16 ATM cell assembling unit 17 data transmitting unit 18 IP routing unit 19 data Receiving unit 20 ATM cell dividing / labeling unit 21 Database 22 Electro-optical converter 23 Transmitting unit

Claims (4)

[Claims] An optical signal of each wavelength transmitted from each node device is wavelength-division multiplexed and distributed to a plurality of node devices, and a label extracting unit of a receiving node device of a distribution-selection type communication network that receives a wavelength-selective signal. In a distribution-selection-type communication control method for extracting desired data by referring to a label of a received signal, when providing a broadcast distribution service, label information for identifying broadcast data from a transmitting node device is transmitted to each node. Distributed to the device, the receiving node device receives the label information, and when participating in a broadcast distribution service corresponding to the label information, sets the label extracting unit and broadcast data corresponding to the label information. When receiving and not participating in the broadcast distribution service corresponding to the label information, the label information is stored without setting to the label extracting unit, and the broadcast distribution service is later described. A distribution selection type communication control method characterized in that when participating in a communication, setting is made to a label extraction unit using label information already stored, and corresponding broadcast data is received. 2. The distribution-selection-type communication control method according to claim 1, wherein the receiving node device detects the participation in a broadcast service from data distributed via a default transfer path. Transmitting a label request message to a node device; and receiving the label request message, the transmitting node device distributes label information corresponding to the broadcast data to each node device. Communication control method. 3. A node device of a distribution-selection type communication network in which an optical signal of each wavelength transmitted from each node device is wavelength-division multiplexed and distributed to a plurality of node devices, and a wavelength-selective node device receives the label of a received signal. A label extracting unit for extracting desired data by referring to the label information; label information distributing means for distributing label information for identifying broadcast data to be transmitted to each node device; It is determined whether or not to participate in the broadcast distribution service corresponding to the above, and when participating in this broadcast distribution service, the label information is set in the label extracting unit, and when not participating in this broadcast distribution service, A label information processing means for storing the label information; and a label information stored in the label information processing means, when participating in the broadcast service later. Node device characterized by comprising a label information setting means for setting the Le extractor. 4. Using the node device according to claim 3, and using the distribution-selection type communication control method according to claim 1 or 2, assigning label information for identifying broadcast data to all node devices. And the node device that has received the label information sets or accumulates it in the label extraction unit,
A distribution-selection type communication network characterized in that, when participating in the broadcast service later, the receiving node device uses the stored label information without exchanging the label information with the transmitting node device. .