JPH11234267A - Multicasting method - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a multicasting method with which transfer capability related to the multicasting of an entire network is improved and the transfer quality of multicast frame is improved. SOLUTION: In this method, an edge node 7 placed at the node of an access network 2 and a core network 1 specifies a link identifier for transmission to the access network 2 while referring to a destination core network address described in a core network frame 9 received from the core network 1, extracts a user protocol frame from the core network frame 9 and transmits the user protocol frame to the previously identified transmission link to the access network, while an access node 8 in the access network 2 specifies the list of plural link identifiers for transmission while referring to the link identifier of a cell inputted from the edge node 7, copies the inputted cells and transmits them to the respective previously specified links for transmission one by one. In place of the destination core network address, a destination user protocol address may be referred to as well.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention provides a multicast service required for logically forming the Internet or a broadcast service required for logically forming a MAC bridge network on a wide area frame transfer network. Related to a useful multicast method.

[0002]

2. Description of the Related Art A conventional multicast method will be described with reference to the drawings. FIG. 1 is a diagram showing a network model.
The entire network model is a hybrid network having a configuration in which a user network is connected to a core network via an access network. The user network is a LAN of an arbitrary architecture distributed over a wide area, and performs frame transfer by an arbitrary method in a user site. The core network is a wide-area frame switching network, which encapsulates user protocol packets in a frame format independent of the user protocol, and performs connectionless frame switching on the frames. The access network is positioned as a subscriber accommodation network accommodating the user network in the core network, and transfers a user protocol frame using a semi-permanently set connection.

In FIG. 1, user networks 3, 4, 5, which are distributed over a wide area, are connected to a core network 1 via an access network 2. The core network 1 and the access network 2 are connected via an edge node 7. Further, in the core network 1,
A multicast server 6 serving as a starting point of the multicast frame is installed.
An access node 8 is provided for connecting the user networks 3, 4, and 5 by ATM-VC.

FIG. 2 is a diagram for explaining a conventional multicast method in such a network model.
Part of the core network frame 9 transmitted from the multicast server 6 installed on the core network 1 reaches the edge node 7. Here, the edge node 7 is the access node 8
And individual access links 10, 11, and 12 are set between the user networks 3, 4, and 5, respectively. Then, the edge node 7 transmits the core network frame 9 received from the core network 1 side.
, Refer to the destination core network address described in the header part, and specify the transmission link identifier to a plurality of user networks, and extract the user protocol frame from the payload part of the received core network frame 9, Is copied as many times as the ground.

[0005] Thereafter, the edge node 7 transmits the copied user protocol to the access link for which the transmission link identifier is specified first among the access links 10, 11, and 12 corresponding to the user networks 3, 4, and 5, respectively. The frames 13, 14, and 15 are transmitted, respectively. The user protocol frames 13, 14, and 15 transmitted to the access network 2 are distributed to the specified user networks 3, 4, and 5 according to the access links 10, 11, and 12 set by the access node 8.

As described above, in the conventional multicast method, it is necessary to duplicate a frame at an edge node, and this is performed by software processing according to a normal mounting method. For this reason, the processing load on the edge node becomes heavy, and it tends to become a bottleneck on the transfer route.

[0007]

SUMMARY OF THE INVENTION In view of the above-mentioned problems, an object of the present invention is to make it easier to duplicate a frame by hardware processing, to improve the transfer capability related to multicasting of the entire network, and to improve multicasting. An object of the present invention is to provide a multicast method capable of improving frame transfer quality.

[0008]

According to the present invention, there is provided a multicast method, wherein an edge node located at a connection point between an access network and a core network includes a header of a core network frame received from the core network. The link identifier for transmission to the access network is specified by referring to the destination core network address described in the portion, the user protocol frame is extracted from the payload portion of the core network frame, and the user protocol frame is identified first. Transmit on the transmission link to the access network, the access node in the access network refers to the link identifier of the cell input from the edge node, specifies a list of a plurality of transmission link identifiers, and duplicates the input cell Then, one transmission is performed for each transmission link specified above.

According to another multicast method of the present invention, an edge node located at a connection point between an access network and a core network comprises:
Extract the user protocol frame from the payload portion of the core network frame received from the core network, specify the transmission link identifier to the access network by referring to the destination user protocol address described in the header portion of the user protocol frame, Transmitting the user protocol frame to the previously identified transmission link to the access network, wherein the access node in the access network references the link identifier of the cell input from the edge node and lists a plurality of transmission link identifiers; , The input cell is copied, and transmitted one by one to each transmission link specified earlier.

According to the multicast method of the present invention, the edge node does not need to copy the frame, but simply performs the unicast transfer. Therefore, the edge node hardly becomes a bottleneck. In addition, the frame is copied on a cell basis at the access network node.
Since the cell duplication function is usually performed by hardware processing, even if the access network node is in charge of the frame duplication processing,
This is unlikely to be a bottleneck.

[0011]

Next, an embodiment of the present invention will be described with reference to the drawings. FIG. 3 is a diagram for explaining the multicast method of the present invention. Part of the core network frame 9 transmitted from the multicast server 6 installed on the core network 1 reaches the edge node 7. Here, the edge node 7
Using the access node 8, an access link 20 for multicast is set between the user networks 3, 4, and 5. Accordingly, the edge node 7 extracts a user protocol frame from the core network frame 9 received from the core network 1 side, divides the user protocol frame into ATM cells, and performs unicast transfer to the access link 20.

The user protocol frame transmitted to the access network 2 is divided into cells, and an appropriate user network 3, 4,
5 distributed. That is, the ATM cells that have arrived at the access node 8 from the edge node 7 are copied in the access node 8 in cell units and distributed to the user networks 3, 4, and 5. As a result, the user protocol frame transmitted from the edge node 7 is duplicated in the access node 8 into a plurality of user protocol frames 13, 14, and 15 and distributed to the user networks 3, 4, and 5.

FIG. 4 is a diagram showing an embodiment of the edge node 7. The core network address extracting unit 71 receives the core network frame from the core network 1, extracts the core network address, transfers the core network frame to the user protocol frame extracting unit 72, and simultaneously extracts the extracted destination core network address into the frame. The data is transferred to the transfer table search unit 73. The user protocol frame extraction unit 72 extracts a user protocol frame from the received core network frame, and transfers this to the cell generation unit 75. The frame transfer table search unit 73 specifies a link identifier using the frame transfer table 74 from the transferred core network address. Frame forwarding table
74 defines the correspondence between the destination core network address and the access network link identifier. The frame transfer table search unit 73 uses the obtained link identifier as a link identifier for transmission to the access network from which the frame is to be output, and transfers this to the cell generation unit 75.

The cell generator 75 divides the user protocol frame transmitted from the user protocol frame extractor 72 into ATM cells, and then converts the VPI / V of the cell header.
In the CI area, a value reflecting the transmission link identifier sent from the frame transfer table search unit 73 is described.
Typically, the value of the access network link identifier is described as it is. Thereafter, the cell-divided frame is stored in the access network 2
Transfer to That is, a transmission access link to the access network 2 corresponding to the access network link identifier specified earlier.
On 20, a cell-divided user protocol frame will be transmitted. The user protocol frame divided into cells and transmitted to the access network 2 is copied in the access node 8 and distributed to an appropriate user network according to an access link set by the access node 8.

FIG. 5 is a diagram showing another embodiment of the edge node 7. In FIG. The user protocol frame extractor 72 receives the core network frame from the core network 1, extracts the user protocol frame, and transfers the user protocol frame to the user protocol address extractor 76. The user protocol address extraction unit 76 extracts a user protocol address from the received user protocol frame, transfers the original user protocol frame to the cell generation unit 75, and simultaneously extracts the extracted destination user protocol address into the frame transfer table search unit. Transfer to 73. The frame transfer table search unit 73 specifies a link identifier from the transferred user protocol address using the frame transfer table 74. The frame transfer table 74 defines the correspondence between the destination user protocol address and the access network link identifier. The frame transfer table search unit 73 uses the obtained link identifier as a link identifier for transmission to the access network from which the frame is to be output, and transfers this to the cell generation unit 75.

The cell generation unit 75 divides the user protocol frame transmitted from the user protocol address extraction unit 76 into ATM cells, and then converts the VPI / V of the cell header.
In the CI area, a value reflecting the transmission link identifier sent from the frame transfer table search unit 73 is described.
Typically, the value of the access network link identifier is described as it is. Thereafter, the cell-divided frame is stored in the access network 2
Transfer to That is, a transmission access link to the access network 2 corresponding to the access network link identifier specified earlier.
On 20, a cell-divided user protocol frame will be transmitted. The user protocol frame divided into cells and transmitted to the access network 2 is copied in the access node 8 and distributed to an appropriate user network according to an access link set by the access node 8.

FIG. 6 is a diagram showing an embodiment of the access node 8. Upon receiving a cell from the ATM access network 2, the input link identifier extraction unit 81 receives the VPI / VC of the cell header.
The input link identifier is extracted with reference to the I area. The original cell is transferred to the cell copy unit 82, and the extracted input link identifier is transferred to the cell copy transfer table search unit 83. The cell copy transfer table search unit 83 specifies an output link identifier from the transferred user protocol address using the cell copy transfer table 84. Cell replication forwarding table
In 84, the correspondence between the input link identifier and the output link identifier list is defined.

The cell copy transfer table search unit 83 calculates the number of link identifiers from the transferred list of output link identifiers, notifies the cell copy unit 82 of the number, and converts the obtained list of output link identifiers into a plurality of cells. Transfer to the output unit 85. The cell duplication unit 82 duplicates the cell transferred from the input link identifier extraction unit 81 based on the number of link identifiers notified from the cell duplication transfer table 84, and outputs the obtained plural cells to the plural cell output unit. Transfer to 85. The multiple cell output unit 85 extracts individual link identifiers from the list of output link identifiers input from the cell replication transfer table search unit 83, and outputs each of the VPI / VPI of the header of the cell transferred from the cell replication unit 82. Describe in the VCI area. The cell in which the VPI / VCI of the cell header is rewritten is the ATM
It is sent to the access network 2.

In this case, a different link identifier is assigned to each cell, and as a result, the user protocol frame transferred by dividing the cell from the edge node 7 is distributed to an appropriate user network.

[0020]

According to the multicast method of the present invention, the frame is copied in the access node on a cell-by-cell basis, but this is processed by hardware processing according to the normal access node mounting method. You.
Therefore, the access node hardly becomes a bottleneck on the transfer route. In addition, since the edge node itself does not duplicate a frame, it is unlikely to become a bottleneck. As a result, the multicast transfer capability of the entire network can be improved.

[Brief description of the drawings]

FIG. 1 is a diagram showing a network model.

FIG. 2 is a diagram illustrating a conventional multicast method.

FIG. 3 is a diagram illustrating a multicast method of the present invention.

FIG. 4 is a diagram showing an embodiment of an edge node.

FIG. 5 is a diagram showing another embodiment of an edge node.

FIG. 6 is a diagram illustrating an embodiment of an access node.

[Explanation of symbols]

 Reference Signs List 1 core network 2 access network 3, 4, 5 user network 6 multicast server 7 edge node 8 access node 9 core network frame 10, 11, 12 access link 20 access link 71 core network address extractor 72 user protocol frame extractor 73 frame Transfer table search unit 74 frame transfer table 75 cell generation unit 76 user protocol address extraction unit 81 input link identifier extraction unit 82 cell duplication unit 83 cell duplication transfer table search unit 84 cell duplication transfer table 85 multiple cell output unit

 ──────────────────────────────────────────────────の Continued on the front page (72) Inventor Hiroyuki Hara 3-19-2 Nishi Shinjuku, Shinjuku-ku, Tokyo Nippon Telegraph and Telephone Corporation

Claims (2)

[Claims] 1. A multicast server in a core network in a computer communication network in which a user network distributed over a wide area is accommodated in a core network which is a wide area connectionless frame transfer network via an access network which is a connection type cell transfer network. In the multicast method performed starting from the starting point, the edge node located at the connection point between the access network and the core network refers to the destination core network address described in the core network frame received from the core network and transmits the packet to the access network. Identifying a trusted link identifier, extracting a user protocol frame from the core network frame, transmitting the user protocol frame to a transmission link to the previously identified access network, wherein an access node in the access network is Refers to the link identifier of the entered cell and re-executes multiple transmission link identifiers. A multicast method comprising identifying a list, copying an input cell, and transmitting the duplicated cell to each of the transmission links specified above. 2. A multicast server in a core network in a computer communication network in which a user network distributed over a wide area is accommodated in a core network which is a wide area connectionless frame transfer network via an access network which is a connection type cell transfer network. In the multicast method performed from the starting point, an edge node located at a connection point between the access network and the core network extracts a user protocol frame from a core network frame received from the core network, and outputs a destination described in the user protocol frame. A link identifier for transmission to the access network is specified by referring to the user protocol address, and the user protocol frame is transmitted on the transmission link to the previously identified access network. Multiple transmissions are performed by referring to the link identifier of the entered cell. A multicast method comprising: specifying a list of trusted link identifiers; copying an input cell; and transmitting the copied cells one by one to each transmission link specified above.