JP2009141391A - Overlay multicast packet communication system - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To obtain an overlay multicast packet communication system enabling efficient overlay multicast communication by suppressing consumption in a communication line having a narrow bandwidth. <P>SOLUTION: The overlay multicast packet communication system is divided into a plurality of subaggregates comprising a group of control units connected without using any narrow-band communication paths based on the width of a physical communication path, where the respective control units are connected by the aggregate of the control units. The control unit in each subaggregate communicatively forms a logical communication path without using the communication path between the subaggregates. A first control unit in charge of distribution transmits a multicast packet to one second control unit selected per subaggregate by unicast. The second control unit duplicates a packet and distributes it to the control unit of a distribution destination belonging to the same subaggregate along the logical communication path. <P>COPYRIGHT: (C)2009,JPO&INPIT

Description

  The present invention relates to an overlay multicast packet communication system that performs multicast packet communication in an overlay network including a narrow band.

  Conventionally, there is a distributed hash table (DHT) technique typified by Non-Patent Document 1 as a method for performing scalable communication between nodes using an overlay network and distributed data. In an overlay network using DHT, a fixed-length ID value is assigned to both the nodes constituting the network and the data arranged therein using a hash function. Each data is distributed and arranged so that the node having the closest ID value manages it.

  When this DHT is used to form an overlay network of a large number of nodes and user terminals and multicast communication is performed on this network, one of the nodes (distribution node) is in charge of packet replication distribution processing. In the distribution node, all nodes to which the participating users connect are managed as distribution information, and packets received from a certain participating user terminal are copied and distributed, and multicast packets are distributed to all participating users.

  As a method other than the DHT technique, for example, Patent Document 1 discloses a multicast communication method that does not require complicated VPN management and can be applied to various tunnel techniques.

“Cord: A Scalable Peer-to-Peer Lookup Service for Internet Applications”, Proc. ACM SIGCOMM, 2001 JP 2002-176436 A

  However, when performing multicast communication using an overlay network configured using the DHT technology, a distribution node is selected based on a node ID that is an output value of a hash function, and the arrangement of participating user terminals and nodes to which the distribution user terminal is connected Is determined independently. For this reason, when a line with a narrow band exists in the communication path from the user terminal to the distribution node, a packet is reciprocally transferred to the distribution node, resulting in band consumption of the line and communication delay. In particular, since downlink packets (packets sent from the distribution node to the user terminal) are duplicated by the distribution node, the influence on the other communication becomes large. As described above, it has been a problem to reduce the burden on a narrow-band communication line that occurs when performing overlay multicast communication.

  In addition, according to the technique of Patent Document 1, there is no mention of a method for performing multicast distribution by transfer path control in consideration of a bandwidth difference in a network in which a bandwidth difference that cannot be ignored exists.

  The present invention has been made in view of the above, and an object of the present invention is to provide an overlay multicast packet communication system capable of suppressing the consumption of a communication line with a narrow band and performing efficient overlay multicast communication.

  In order to solve the above-described problems and achieve the object, the present invention includes a control device connected to each other via a physical communication path, a communication terminal connected to the control device, and a multicast group. And multicast distribution information indicating the relationship between the multicast packet distribution destination control devices are distributed and held in one first control device uniquely determined for each multicast group, and the multicast distribution information is based on the multicast distribution information. In an overlay multicast packet communication system for transferring packets, a plurality of sub-sets each including a plurality of control devices connected without passing through a narrowband communication path based on the width of a physical communication path connecting the control apparatuses. The control device is divided and logically communicated to all control devices belonging to the same subset as its own device. The multicast distribution information added to the first control device is set as the second control device selected for each subset as the control device of the multicast packet distribution destination, The second control device retains relay distribution information indicating a relationship between the multicast group and a control device that belongs to the same subset as itself and to which the communication terminal of the multicast distribution destination is connected. The control device transmits the multicast packet to the second control device by unicast based on the multicast distribution information, and the second control device that receives the packet transmitted by the unicast receives the relay distribution information. The packet is replicated and distributed along the logical communication path to the control device of the distribution destination of the multicast group of the destination indicated by To.

  According to the present invention, a group of control devices connected by a physical communication path having a communication band of a certain width or more is defined as one subset, and the control devices in each subset are communication paths between the subsets. A logical communication path is formed so that communication can be performed without using a multicast packet, and a multicast packet is transmitted by unicast to a predetermined first control device defined for each sub-set. It is possible to obtain an overlay multicast packet communication system capable of suppressing the consumption of a narrow communication line and performing efficient overlay multicast communication.

  Embodiments of an overlay multicast packet communication system according to the present invention will be described below in detail with reference to the drawings. Note that the present invention is not limited to the embodiments.

Embodiment 1.
First, the network configuration of the overlay multicast packet communication system according to the first exemplary embodiment of the present invention will be described. FIG. 1 shows an example of a network configuration of an overlay multicast packet communication system according to the first exemplary embodiment of the present invention.

  In FIG. 1, the overlay multicast packet communication system according to the first embodiment is composed of a control device 1 and a communication terminal 7, and a user connects the communication terminal 7 to the control device 1 installed by an operator to perform multicast packet communication. Do. A logical communication path is set between the control apparatus 1 and another control apparatus 1, and between the control apparatus 1 and the communication terminal 7, and one-way or two-way communication is possible in each communication path. . In packet transfer, a route along this logical communication path can be selected.

  Each control device 1 and communication terminal 7 are assigned to one of the network islands 8. The network island 8 is an area that can be reached from a certain point on the network without using a narrow-band communication path. The communication path connecting the control devices 1 belonging to different network islands 8 is the same network island 8. It has a narrower communication band than the communication path connecting the control devices 1 to which it belongs. A communication channel with a narrow communication band is specifically a communication channel that does not actually provide a high communication speed, as well as a place where a wide band is actually secured, such as an Internet exchange or ISP contact point. Included are places where a wide communication band cannot be secured per communication due to structurally concentrated access or where it is not desirable to apply a load. The division into the network islands 8 is performed by the operator based on the measurement result of the IP layer and the actual communication speed.

  Next, a functional configuration of the control device 1 configuring such a network will be described. FIG. 2 is a diagram showing a configuration of the control device 1 serving as a node constituting the overlay multicast packet communication system according to the first embodiment of the present invention.

  2, the control device 1 includes a control information management unit 2, a database management unit 3, an arithmetic processing unit 4, a transmission processing unit 5, and a reception processing unit 6.

  The control information management unit 2 holds transfer information for packet transfer between devices. The transfer information is information regarding the identification number that is the identification number of the own device 1 and the identification number of the partner control device 1 that can transfer the packet. The identification number is a value obtained by replacing the high-order bits of a fixed-length bit string generated by a hash function from a value unique to the own device 1 with the number of the identification number uniquely assigned to the network island 8 to which the identification number belongs. It is. The transferable counterpart control device 1 is set based on this identification number, and the own device 1 forms a logical communication path with the transferable counterpart control device 1. Each control device 1 forms a logical communication path in this way, thereby forming the network shown in FIG.

  The database management unit 3 holds a database that is distributed on the overlay network. The database is a database of information (hereinafter simply referred to as entries) regarding the identification number of the multicast group to which the user belongs and the identification number of the control apparatus 1 or communication terminal as the transfer destination. The control device 1 holds different types of databases depending on the role of the control device 1 in multicast communication. The control device 1 is divided into three types according to its role: a distribution control device 1x, a relay control device 1y, and a terminal control device 1z. Each role may be combined. The distribution control device 1x is the control device 1 in charge of the distribution function in the multicast group. The relay control device 1y is a control device 1 that duplicates a packet from the distribution control device 1z selected for each network island 8 and distributes the packet to the end control device 1z. The end control device 1z is the control device 1 to which the communication terminals 7 of users belonging to the multicast group are connected.

  FIG. 3 is a diagram illustrating an example of a database. The database shown in this example is a database of entries related to the multicast group and the destination relay control device 1y. Hereinafter, the database of entries whose destination is the relay control device 1y as shown in FIG. 3 is referred to as multicast distribution information, and is distinguished from the databases held by the relay control device 1y and the end control device 1z described later. The multicast distribution information is stored in the database management unit 3 of one of the control devices 1 by a distributed hash. For each multicast group, the control device 1 that holds the multicast distribution information including the entry of the group performs distribution control. Device 1x.

  The relay control device 1y duplicates the packet transmitted from the distribution control device 1x by the number of terminal control devices 1z to which the communication terminals 7 belonging to the same network island 8 and participating in the multicast group are connected, The terminal control device 1z is transferred as a destination along a logical communication path. In order to transfer the packet in this way, the database management unit 3 of the relay control apparatus 1y identifies the end control apparatus 1z instead of the relay control apparatus 1y as a copy distribution destination of the packet of each entry in the database of FIG. A database with numbers is maintained.

  In the database of the terminal control device 1z, the communication terminals 7 connected to the own device 1z and participating in the multicast group as a copy distribution destination of the packet of each entry in the database of FIG. 3 instead of the relay control device 1y. The identification number is marked.

  The transmission processing unit 5 and the reception processing unit 6 communicate with an external network.

  The arithmetic processing unit 4 connects the control information management unit 2, the database management unit 3, the transmission processing unit 5 and the reception processing unit 6 and analyzes the data arriving from the reception processing unit 6. If this is a network control request, For example, if it is a database acquisition request to the control information processing unit 2, the transmission processing unit 5 refers to the control information processing unit 2 if referring to the control information processing unit 2 if it is data to be transferred to the other control device 1. Transfer to external network.

  Next, an operation of transferring a multicast packet in the overlay multicast packet communication system according to the first embodiment will be described. FIG. 4 is a diagram for explaining a multicast packet distribution route in the overlay multicast packet communication system according to the first embodiment.

  In FIG. 4, the control device 1 that has received a multicast packet from any one of the communication terminals 7 transfers the packet to the relay control device 1 y using a logical communication path, and the relay control device 1 y controls distribution of the packet. Transfer to device 1x. The distribution control device 1x refers to the multicast distribution information stored in the database management unit 3 and searches for an entry corresponding to the multicast group identification number. Packets are duplicated by the number of distributions specified in the entry, and each packet is transmitted unicast to the distribution destination relay control device 1y group. Next, the relay control device 1y refers to the database held in the database management unit 3, searches for an entry corresponding to the multicast group identification number, duplicates the packet received by unicast from the distribution control device 1x, Each of the terminal control devices 1z is transmitted by unicast. The terminal control device 1z that has received the packet refers to the database of the database management unit 3 of the own device 1z, searches for an entry corresponding to the multicast group identification number, transmits the packet to the communication terminal 7 that is the destination, and Terminal 7 receives the multicast packet.

  As described above, in the multicast packet communication according to the first embodiment, a packet is transmitted by unicast to the relay control device 1y of each network island 8, and the relay control device 1y duplicates the packet to transmit the same network island 8 Is transmitted to the terminal control device 1z belonging to. Incidentally, when performing multicast packet communication in an overlay network constructed only based on a general DHT technology such as Non-Patent Document 1, the relay control device 1y as shown in the configuration according to the first embodiment is not provided. Therefore, as shown in FIG. 5, the control device in charge of distribution (corresponding to the distribution control device 1x in the first embodiment) is connected to the control device (corresponding to the terminal control device 1z) to which the receiving communication terminal is connected. The packet is copied and transmitted by the number of control devices of the transmission destination. As can be seen from the above, according to the communication method of multicast packet communication according to the first embodiment, the number of packets passing through the narrowband communication path between the network islands 8 can be reduced.

  Next, the operation of the overlay multicast packet communication system according to Embodiment 1 when a certain user communication terminal 7 joins a certain multicast group will be described. FIG. 6 is a flowchart for explaining the join processing operation for joining a certain multicast group with the communication terminal 7.

  In FIG. 6, when a multicast packet participation request message is transmitted to the terminal control device 1z to which the communication terminal 7 is connected (step S1), the arithmetic processing unit 4 of the terminal control device 1z sends to the database management unit 3 of the own device 1z. By referring to the stored database and searching for the entry of the multicast group for which the participation request has been made, it is determined whether or not the packet of the multicast group is distributed to another communication terminal 7 connected to the own apparatus 1z. (Step S2). If the packet has already been delivered to another communication terminal 7 (Yes in step S2), there is a route for delivering the packet to the own device 1z, so that the own device is duplicated and delivered to the communication terminal 7 that has issued the participation request. It adds to the destination of the multicast group described in the 1z database (step S7), and ends the process.

  When the arithmetic processing unit 4 of the terminal control device 1z that has received the request message determines that there is no other communication terminal 7 receiving the distribution of this multicast group among the communication terminals 7 connected to the own device 1z. (Step S2, No), the end control device 1z adds the identification number of the multicast group and the entry of the communication terminal 7 that transmitted the request message to the database, and the relay control device 1y of the network island 8 to which the own device 1 belongs. In response to this, a request message is transmitted so as to duplicate and distribute the packet to its own device 1z (step S3). When the relay control device 1y receives the request message, the arithmetic processing unit 4 of the relay control device 1y refers to the database held in the database management unit 3 and searches for the entry of the multicast group for which the participation request has been made. Thus, it is determined whether the packet of the multicast group is distributed to the terminal control device 1z other than the terminal control device 1z that transmitted the request message by the terminal control device 1z belonging to the network island 8 to which the own device 1y belongs. (Step S4). When the packet is already distributed to another terminal control device 1z (step S4, Yes), there is a route for delivering the packet to the own device 1y, so the terminal control device 1z that transmitted the request message is copied in the database. By adding it to the delivery destination, the terminal control device 1z is set to replicate and deliver the packet (step S8), and the process ends.

  Receiving the request message, the arithmetic processing unit 4 of the relay control device 1y determines that there is no other end control device 1z receiving the multicast group distribution among the end control devices 1z distributed from the own device 1y. If the relay control device 1y receives the request message (step S4, No), it adds the identification number of this multicast group and the entry of the end control device 1z that transmitted the request message to the database, and sends it to the distribution control device 1x. Then, a request message is transmitted so as to duplicate and deliver the packet to the own apparatus 1y (step S5). When the distribution control device 1x receives the request message, the arithmetic processing unit 4 of the own device 1x transmits the request message to the replication distribution destination of the multicast group to the database held in the database management unit 3 of the own device 1x. By adding the relay control apparatus 1y, the relay control apparatus 1y is set to be replicated and distributed (step S6), and the process is terminated.

  In this way, when a communication terminal 7 belonging to the same network island 8 as the communication terminal 7 performing multi-packet communication desires to newly receive a multicast packet, the database of the distribution control device 1x is not changed as much as possible. Since the participation process for the multi-packet communication of the communication terminal 7 is executed, it is possible to reduce the load on the narrowband line due to the participation request message passing between the network islands 8.

  As described above, according to the overlay multicast packet communication system according to the first embodiment, a group of control devices connected by a physical communication path having a communication band of a certain width or more is formed as one sub-set (network island). The control device in each sub-set forms a logical communication path so that communication is possible without using a communication path between the sub-sets, and one multicast packet is defined for each sub-set. Each of the first control devices is transmitted to the first control device by unicast, and the predetermined first control device is configured to replicate and distribute the packet transmitted by the unicast to the control device which is the multicast distribution destination. Therefore, it is possible to suppress the consumption of a communication line with a narrow bandwidth and perform efficient overlay multicast communication.

Embodiment 2.
Next, an overlay multicast packet communication system according to the second embodiment of the present invention will be described. In the overlay multicast packet communication system according to the second embodiment, when a multicast packet is transmitted from a certain communication terminal 7 to a multicast group, the distribution control device 1x transmits the packet to the distribution control device 1x. Is characterized by transmitting a corresponding entry of multicast distribution information. Since the network configuration, the functional configuration of the control device, and the process of joining the multicast group are the same as those in the first embodiment, description thereof will be omitted, and the multicast distribution information that is a feature of the packet communication system of the present embodiment will be duplicated. Only the operation of transmitting is described.

  FIG. 7 is a diagram for explaining an operation of transmitting a copy of multicast distribution information to the relay control device 1y in the network of FIG.

  In FIG. 7, when the relay control device 1y receives a multicast packet from the communication terminal 7 belonging to the same network island 8 via the terminal control device 1z, the packet is transferred to the distribution control device 1x (broken line in the figure). Arrow (1)). The distribution relay device 1x that has received the multicast packet once transmits a copy of the entry related to the destination multicast group from the multicast distribution information to the relay control device 1y that has transferred the packet, and relay control that relays the multicast packet described above. The relay control apparatus 1y that has transmitted to and received the apparatus 1y stores the multicast distribution information entry in the database management unit 3 of the own apparatus 1y (dotted line arrow (2) in the figure). In this way, the relay control device 1y is added with the function as the distribution control device 1x for this multicast group.

  In this state, when any subordinate communication terminal 7 (which may not be the same as the first communication terminal) transmits a packet addressed to the same multicast group as described above, the packet is transferred to the relay control device 1y, By referring to the multicast distribution information stored in the database management unit 3 described above, the packet itself is duplicated and distributed to the destination relay control device 1y described in the list (broken line arrow (3) in the figure). The subsequent transfer processing is the same as the operation of transmitting the packet of the overlay multicast packet communication system according to the first embodiment.

  Thus, according to the overlay multicast packet communication system according to the second embodiment, when the distribution control device 1x receives the multicast packet, the multicast distribution information corresponding to the relay control device 1y transmitted via the packet is received. Since the relay control apparatus 1y transfers the packet addressed to the corresponding multicast group based on the transmitted multicast distribution information and the relay distribution information held therein, the embodiment Compared with the overlay multicast packet communication system according to FIG. 1, since it is not necessary to go through the distribution control device 1x for distribution to the relay control device 1y, the number of transfers on the narrowband communication path between the network islands 8 is reduced. The Also, since the delivery packet to the communication terminal 7 existing on the same network island 8 as the transmission source communication terminal 7 is looped back and delivered by the relay control device 1y, the delivery packet is delivered without going through the communication path outside the network island 8. Is done.

  By the way, in the overlay multicast packet communication system according to the first embodiment and the second embodiment, the communication path between the network islands 8 may be configured to be held only by the relay control device 1y. In this way, the number of transfers within the same network island 8 can be further reduced.

  As described above, the overlay multicast packet communication system according to the present invention is suitable for application to an overlay multicast packet communication system that performs multicast packet communication in an overlay network including a narrow band.

1 is a diagram for explaining an example of a network configuration of an overlay multicast packet communication system according to a first embodiment; FIG. FIG. 3 is a diagram illustrating a functional configuration of a control device according to the first embodiment. It is a figure explaining the example of a database. 6 is a diagram for explaining a multicast packet distribution route in the packet communication system according to the first embodiment; FIG. It is a figure explaining the delivery route of the multicast packet in a general overlay multicast packet communication system. 5 is a flowchart for explaining a join processing operation in which a communication terminal joins a multicast group in the packet communication system according to the first embodiment. FIG. 11 is a diagram for explaining an operation of transmitting a duplicate of multicast distribution information entry to the relay control device in the packet communication system according to the second embodiment.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Control apparatus 1x Distribution control apparatus 1y Relay control apparatus 1z End control apparatus 2 Control information management part 3 Database management part 4 Arithmetic processing part 5 Transmission processing part 6 Reception processing part 7 Communication terminal 8 Network island

Claims (4)

Multicast distribution information including a control device connected to each other via a physical communication path and a communication terminal connected to the control device, and indicating a relationship between a multicast group and a control device to which multicast packets are distributed, is multicast. In an overlay multicast packet communication system that is distributed and held in one first control device uniquely determined for each group and forwards the multicast packet based on the multicast distribution information,
Based on the width of the physical communication path connecting the control devices, the control device is divided into a plurality of sub-sets each including a plurality of control devices connected without going through a narrowband communication path. Add a logical communication path to enable communication to all control devices belonging to the subset.
The multicast distribution information held in the first control device sets a second control device that is selected for each subset as a control device to which the multicast packet is distributed,
The second control device holds relay distribution information indicating a relationship between the multicast group and a control device that belongs to the same subset as the control device to which the multicast distribution destination communication terminal is connected,
The first control device transmits a multicast packet unicast to the second control device based on the multicast distribution information,
The second control device that has received the packet transmitted by the unicast copies the packet to the distribution destination control device of the destination multicast group indicated by the relay distribution information and copies the logical communication path. Deliver along
An overlay multicast packet communication system characterized by the above. Only the second control device forms a logical communication path between different subsets,
The overlay multicast packet communication system according to claim 1. When a communication terminal newly desires to join a multicast group, the communication terminal transmits a participation request message to the second control device,
The second control device that has received the message adds the control device to which the communication terminal is connected to the multicast distribution destination of the multicast group of the relay distribution information.
The overlay multicast packet communication system according to claim 1 or 2, When a communication terminal belonging to a multicast group transmits a multicast packet, the control device passes the packet through a second control device belonging to the same subset as the own device along the logical communication path. Take a transfer path, transfer to the first control device holding the multicast distribution information about the multicast group,
The first control device that has received the packet replicates and transmits the multicast distribution information to the second control device through which the packet has passed, and the second control device that has received the multicast distribution information When a multicast packet addressed to the multicast group is received from a communication terminal connected to a control device belonging to the same subset as the own device, the second control device belonging to a different subset based on the received multicast distribution information The multicast packet is transmitted by unicast to the control device connected to the communication terminal belonging to the multicast group held in the relay distribution information of the own device, and the packet addressed to the multicast group is duplicated. Deliver along a logical channel,
The overlay multicast packet communication system according to any one of claims 1 to 3.

Images