JPH11127200A - Multicast method - Google Patents

Abstract

PROBLEM TO BE SOLVED: To attain the high scalability to the scale of a network by sending the membership information to the aggregation routers present in the route direction, only when the number of branches where the participant members are present in the free direction has a specific change and confirming the presence or absence of participant members in the free direction for all aggregation routers in each branch to transfer a multicast packet. SOLUTION: When the number of branches where the participant members are present in the free direction is changed to 1 from 0 and vice versa, the membership information are sent to the aggregation routers present in the route direction. Each of these routers periodically acquires the participant state of its subsidiary host to every multicast via a group management protocol and records the acquired participant state on a membership information table. When the number of participant members is changed from 0 to 1, a participant request message is sent to each aggregate router of the route direction via a membership information route. Meanwhile, a removal request message is sent to the aggregate router, when the number of participant members is changed from 1 to 0 respectively.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

[0001] 1. Field of the Invention [0002] The present invention relates to a multicast method in a non-broadcast type network such as an IP network.

[0002] When the members (participating hosts) of a multicast group change with time, in order to construct a multicast tree in a network, it is necessary to determine whether or not the participating hosts for each multicast group are under the control of each router at that time. It is necessary to use membership information that indicates The simplest way to use membership information is by each router flooding its membership information to all routers in the network,
In this method, each router knows where in the network the participating hosts are and creates a multicast tree. However, since the membership information is control information, it is necessary to minimize the amount of membership information exchanged in the network in order to maintain a large link capacity for user information packets.

In the conventional multicast method, one of the following two methods has been adopted as a measure for reducing membership information. That is, in the first method, the network is divided into two layers, a lower layer and an upper layer, and membership information is flooded at each layer, but membership information of the lower layer is aggregated at a boundary router with the upper layer, This is a method for reducing the amount of membership information. In the second method, one representative router is determined in the network, and each router transmits membership information to the representative router. In this method, since the path through which the membership information propagates is limited, the amount of the membership information can be reduced as compared with the case where the membership information is flooded in the network. However, membership information is not aggregated, and membership information from a plurality of routers propagates on the same route.

[0004]

When such a conventional method is used, no major problem occurs when the network scale is small, but as the network scale increases, membership information flowing in the network increases, and There is a problem in that the scalability to the network scale is low because the link capacity that can use packets is compressed. An object of the present invention is to provide a multicast method capable of realizing high scalability on a network scale.

[0005]

In order to achieve the above object, a multicast method according to the present invention provides a multicast router network with a membership information path for propagating membership information under the control of each router into the network. And a packet transfer path for transferring the user packet,
Each of the routers is set in advance in a hierarchical tree shape including a plurality of aggregation routers, which are common branch points in the network, and each router transmits the membership information of the umbrella to the root direction using the membership information route, and The aggregation router on the route manages the branch in which the participating member exists based on the membership information received from the leaf direction, and when the number of branches in which the participating member in the leaf direction changes from 0 to 1, and 1
Only when the status changes from 0 to 0, the membership information is transmitted to the aggregation router in the root direction, and all the aggregation routers on the membership information route recognize whether or not there is a leaf-direction participating member for each branch, and use this information. Multicast packets are transferred on the packet transfer path.

In the present invention, by setting a hierarchical tree including all routers in the network as nodes, and exchanging membership information on this tree, the membership information is transmitted to the network using, for example, flooding. Can solve the inefficiency of receiving the same packet multiple times at each router when it is transmitted to the multicast router. With this configuration, membership information can be significantly aggregated.

[0007] The transfer of user packets involves setting up a multicast tree between a multicast router having a sending host under its umbrella and a multicast router having a receiving member under its umbrella, and delivering user packets on this tree. Meaning, when each multicast router constructs a multicast tree, it is necessary to know from which branch a multicast packet received from which branch should be transferred to which branch. In the present invention, each router forwards a multicast packet received from a branch on the hierarchical tree to only the upper router and the lower router in which the participating members exist, thereby performing packet forwarding to all participating members in the network. it can.

[0008] Such a hierarchical tree in the present invention is:
Of course, it can be set by physically constructing the network in a hierarchical tree shape. Alternatively, if a logical hierarchical tree is set on the network, it can be set for a network having an arbitrary physical topology. It can have the advantage that it can be applied universally.

[0009]

Next, an embodiment of the present invention will be described with reference to the drawings. FIG. 1 is a diagram showing a router network having an arbitrary physical topology. In the figure, 1 to 20 are routers, among which 3, 6, 8, 10, 12, 15, and 18 are aggregation routers that aggregate membership information. 101 to 128 are physical links connecting the routers, and 201 to 208 are areas. Although not shown in this figure, hosts are connected to routers 1 to 20, respectively.

FIG. 2 is a diagram showing a membership information route and a packet transfer route in which the router network of FIG. 1 is logically set in a hierarchical tree shape. 3, 6, 8, 10, 12,
15 and 18 are aggregation routers, 301 to 317 are logical links connecting the routers, and 201 to 208 are areas. Further, FIG.
Is a diagram showing the internal structure of the router, and FIG.
FIG. 5 shows a specific example of the membership information table.
FIG. 402 is a diagram showing a specific example of 402. FIG. 6 is a diagram showing a specific example of the multicast routing table 403, and is a diagram showing a correspondence table between each multicast group and a branch number (port number) in which a participating member exists in the leaf direction.

Next, the operation of the present invention will be described. First, a procedure for creating a membership information route and a packet transfer route between routers in the network will be described. In a router network having an arbitrary physical topology as shown in FIG. 1, some routers are selected as aggregation routers and the network is divided into a plurality of areas. At this time, as shown in FIG. 2, the aggregation router is positioned at the boundary of the area, and the area is not arranged in a ring. In FIG. 2, routers 3, 6, 8, 1
0, 12, 15, and 18 are selected as aggregation routers, and 201 to 2
08 indicates the area.

Subsequently, as shown in FIG. 2, for example, the aggregation router 10 is set as the root of the tree, and the aggregation routers 3, 6, 12 and
Using the 18 as a leaf, the aggregation routers in the network are connected by logical links 301 to 306 to form a hierarchical tree. next,
For this hierarchical tree, logical links 307 to 317 are provided from each router in each area to the aggregation router in the root direction.
To create a logical hierarchical tree that includes all routers in the network as nodes. Finally, an appropriate physical route is assigned to a logical link between the routers. For example, the logical link between the aggregation router 8 and the aggregation router 10 can be physically configured using the link 112 or the link 111 + 113.

The physical hierarchy tree generated by the above procedure is used as a path for membership information and a path for packet transfer. In each router, a port number corresponding to the tree root direction and a port number corresponding to the leaf direction are stored in the tree holding unit 401. The membership information path and the packet transfer path need to be logically the same tree, but may be physically different trees. The branch constituting the membership information path is a unidirectional branch from the leaf direction to the root direction, whereas the branch constituting the packet transfer path is a bidirectional branch. Of the packet transfer paths, the branch used for the actual multicast packet transfer is determined based on the membership information propagated on the membership information path.

Next, a method of propagating membership information in a network and a method of aggregation will be described. Each router in the network is an IG
According to a group management protocol such as MP (Internet Group Management Protocol), the status of participation of the subordinate hosts in each multicast group is periodically acquired, and the multicast group in which the subordinate members are present is recorded in the membership information table 402. I do. When a member participating in a certain multicast group occurs, that is, when the number of participating members changes from 0 to 1, a participation request message is sent when there are no members participating in a certain multicast group, that is, the number of participating members. Is 1
When the number changes from 0 to 0, a leave request message is transmitted to the aggregation router in the route direction through the membership information route.

In the join request message and the leave request message, the identifier of the multicast group is described. Based on the join request message and the leave request message received from the leaf direction of the membership information route, the aggregation router determines whether the participating members for each multicast group are under the umbrella of the router located in the leaf direction of the membership information route. Whether or not the branch is present is managed for each branch, and the port corresponding to the branch where the participating member exists is recorded in the multicast routing table 403. In the aggregating router, in the leaf direction through all branches, a join request message is generated when a member participating in a certain multicast group is generated for the first time, and a leave request message is generated when there are no members participating in a certain multicast group. Each is sent to the next aggregation router in the route direction.

By repeating the above procedure at the aggregation routers at each stage, the membership information is aggregated at each aggregation router, while the membership information is propagated to the aggregation router 10 which is the root of the tree. , The presence / absence of members participating in each multicast group for each branch direction is grasped and held in the multicast routing table 402 therein.

Next, a multicast packet transfer method will be described. When a router other than the aggregation router receives the multicast packet from the subordinate host, the router refers to the tree holding unit 401 and transfers the packet to the aggregation router in the root direction.

A router other than the aggregation router is a leaf,
When a multicast packet is received from the root direction, it refers to the membership information table 402, and when there is a participating member under the umbrella, it forwards the packet toward the umbrella host. When a non-leaf router other than the aggregation router receives a multicast packet from the leaf direction, the router refers to the tree holding unit 401 and forwards the packet to a port in the root direction. When a multicast packet is received from the root direction, the packet is transferred to the port in the leaf direction with reference to the tree holding unit 401.

When the aggregation router receives a multicast packet from a leaf direction or from a host under the umbrella, the aggregation router refers to the tree holding unit 401, the membership information table 402, and the multicast routing table 403, and joins a port other than the port that received the multicast packet. If there is a participating member in the leaf where the member exists, in the root direction, or in the subordinate, the packet transfer is performed in the direction of the subordinate host.

When the aggregation router receives a multicast packet from the root direction, the aggregation router refers to the membership information table 402 and the multicast routing table 403, and if there is a participating member in all leaf directions in which the participating member exists and the affiliated member, the affiliated router is affiliated. Forwards the packet toward the host. In this way, a multicast packet can be transferred to all participating hosts in the network.

[0021]

When the conventional multicast method is used, membership information propagated in the network increases as the network scale increases, and the link capacity that can be used by user packets is reduced, so that the scalability with respect to the network scale decreases. According to the present invention, routers for collecting membership information are hierarchically arranged in a network, and the number of hierarchical levels is adjusted according to the network scale, thereby realizing high scalability for the network scale. can do.

[Brief description of the drawings]

FIG. 1 is a diagram showing a router network having an arbitrary physical topology.

FIG. 2 is a diagram showing a membership information route and a packet transfer route in which the router network of FIG. 1 is logically set in a hierarchical tree shape.

FIG. 3 is a diagram showing an internal structure of a router.

FIG. 4 is a diagram showing a specific example of a tree holding unit.

FIG. 5 is a diagram showing a specific example of a membership information table.

FIG. 6 is a diagram showing a specific example of a multicast routing table 403.

[Explanation of symbols]

 1-20 Router 101-128 Physical link connecting routers 201-208 Area 301-317 Logical link connecting routers 401 Tree holding unit 402 Membership information table 403 Multicast routing table 405-407 Control signal line

Claims (1)

[Claims] 1. A multicast router network is provided with a membership information path for propagating membership information belonging to each router into the network and a packet transfer path for transferring user packets within the network. Each of the routers is configured in advance in a hierarchical tree that includes a plurality of aggregation routers, which are branch points of each other. The router manages the branches where the participating members exist based on the membership information received from the leaf direction, and the number of branches where the participating members exist in the leaf direction is 0.
Only when the status changes from 1 to 1 and when the status changes from 1 to 0, the membership information is transmitted to the aggregation router in the root direction. A multicast method comprising: recognizing a multicast packet and using the information to transfer a multicast packet on a packet transfer path.