KR101021271B1 - Method for operating switch supporting relayed multicasting - Google Patents

Abstract

A method of operating a switch according to an embodiment of the present invention connected between a router group including at least one router and at least one host may include receiving a multicast packet from a router group, and transmitting the multicast packet to a router group. Relaying to other multicast agents to perform relay transmission multicasting; and delivering the delivered multicast packet to a host joined to a multicast group corresponding to the multicast packet among at least one host.

Description

Operation method of switch supporting relay transmission multicasting {METHOD FOR OPERATING SWITCH SUPPORTING RELAYED MULTICASTING}

The present invention relates to a network system.

The present invention is derived from the research conducted as part of the Ministry of Science and Technology's support for the development of information and communication standards.

IPTV (Internet Protocol TV) is a service that provides information service, video content, and broadcasting to a television receiver using the Internet. In IPTV, content provided from one provider is delivered to a plurality of information recipients over a network. UniCast-based networks support one-to-one (1: 1) communication. Therefore, in a unicast-based network, the provider of IPTV must deliver the same information as the number of information receivers. This causes an increase in network overhead.

MultiCast-based networks support one-to-many (1: n) communication. Therefore, in a multicast-based network, if a provider of IPTV delivers one content to a multicast network, the content is delivered to a plurality of information receivers.

An object of the present invention is to provide an efficient multicast communication method.

A method of operating a switch according to an embodiment of the present invention connected between a router group including at least one router and at least one host may include receiving a multicast packet from the router group; Relaying the multicast packet to another multicast agent through the router group to perform relay transmission multicasting; And forwarding the forwarded multicast packet to a host joined to a multicast group corresponding to the multicast packet among the at least one host.

In an embodiment, the router group operates on a unicast basis.

In an embodiment, the specific router connected to the at least one host of the at least one router of the router group manages a group of hosts connected to the specific router, and the step of receiving the multicast packet may include receiving the at least one host. Snooping a group management message from the at least one host to the specific router to detect that the at least one host requests to join the multicast group.

The receiving of the multicast packet may include receiving a multicast group from the at least one host and serving the multicast group, if the multicast group is serving the multicast group. And servicing the at least one host.

In an embodiment, the step of receiving the multicast packet may include: joining the multicast group by joining the multicast group if a subscription request for the multicast group is detected from the at least one host and the multicast group is not in service. Serving a cast group to the at least one host.

In an embodiment, joining the multicast group and serving the multicast group to the at least one host may include joining the multicast group to a session manager of the multicast group through a sender of the received multicast packet. Forwarding the request.

In an embodiment, the switch may include an address of a serviced multicast group, an interface ID indicating an interface connected to a host subscribed to the serviced multicast group, and an address of the serviced multicast group and an address of a session manager. And a group information table having a session ID generated based on the received information, wherein the receiving of the multicast packet includes a subscription message for joining the multicast group from the at least one host, and an address of the multicast group. If is registered in the group information table, adding the interface ID of the interface connected to the at least one host in the interface ID field corresponding to the address of the multicast group in the group information table.

In an embodiment, the step of receiving the multicast packet may include registering the address of the multicast group in the group information table if the address of the multicast group is not registered in the group information table. And generating a session ID based on the address of the multicast group, and registering the generated session ID in the group information table.

The switch may further include a session information table having the session ID and a parent multicast agent (PMA) ID indicating a multicast agent transmitting the multicast packet to the switch. In the receiving of the multicast packet, if the ID of the parent multicast agent of the multicast group is not registered in the parent multicast agent ID field of the session information table, the session join request is transmitted to the external session manager. It further comprises a step.

In an embodiment, the step of receiving the multicast packet receives a list of multicast agents pre-subscribed to the multicast group from the session manager, and relays them to the multicast agents pre-subscribed to the multicast group. It further comprises the step of requesting.

The switch according to an embodiment of the present invention performs relay transmission multicasting. Thus, the efficiency of multicast communication is increased.

In order to efficiently support services such as IPTV, a multicast function is required for a network in which an IPTV service is provided. However, the backbone and the conventional networks are generally configured to operate on a unicast basis. In order to efficiently provide a service such as IPTV in a unicast-based network, a network system according to an embodiment of the present invention provides a relayed multicast (RMC) or overlay multicasting (Overlay Multicasting) function.

A method of operating a switch according to an embodiment of the present invention connected between a router group including at least one router and at least one host may include receiving a multicast packet from a router group, and transmitting the multicast packet to the router group. Relaying to the other multicast agent to perform relay transmission multicasting; and forwarding the delivered multicast packet to a host joined to a multicast group corresponding to the multicast packet among at least one host. .

DETAILED DESCRIPTION Hereinafter, exemplary embodiments of the present invention will be described with reference to the accompanying drawings so that those skilled in the art may easily implement the technical idea of the present invention. . By way of example, a record would represent a row of a table, and a field would represent each box constituting rows and columns of the table.

1 is a block diagram illustrating a network system 10 according to an exemplary embodiment of the present invention. Referring to FIG. 1, the network system 10 according to an exemplary embodiment of the present invention may include a router group 100 including a plurality of routers R and a host group 200 including hosts H1 to H3. , A switch S1 connected between the host group 200 and the router group 100, between the host group 300 including the hosts H4 to H6, the host group 300, and the router group 100. The switch includes a switch S2, a sender multicast agent (SMA), and a session manager (SM).

Router group 100 includes a plurality of routers (R). The number of routers R included in the router group 100 is not limited. The router group 100 is connected to a transmitting multicast agent (SMA). The transmitting multicast agent (SMA) delivers multicast packets to the router group 100. A session manager (SM) manages a relayed tree of a transmission multicast agent (SMA) and a reception multicast agent. That is, the session manager SM manages the multicast tree so that the corresponding multicast packet is delivered to the reception multicast agent RMA subscribed to the preset multicast group.

As an example, the transmitting multicast agent (SMA) will forward the multicast packets corresponding to the first and second multicast groups to the router group 100. Multicast packets corresponding to the first multicast group will be delivered to the multicast agents (MAs) subscribed to the first multicast group based on the relay transmission tree managed by the session manager SM. . Similarly, multicast packets corresponding to the second multicast group will be delivered to the multicast agents MA subscribed to the second multicast group.

The switch S1 is connected between the router group 100 and the host group 200, and the switch S2 is connected between the router group 100 and the host group 300. The switches S1 and S2 operate as a multicast agent (MA). By way of example, the switches S1 and S2 will act as a receiving multicast agent (RMA). The switch S1 receives a multicast packet from the router group 100 through a relay transmission multicast tree (for example, an overlay tree) controlled by the session manager SM, and the switch S1 The multicast packet is delivered to a host joined to the multicast group corresponding to the multicast packet received among the hosts H1 to H3 of the host group 200 connected to the multicast packet.

Similarly, the switch S2 receives a multicast packet from the router group 100 through a multicast tree controlled by the session manager SM, and hosts H4 of the host group 300 connected to the switch S2. The multicast packet is delivered to the host joined to the multicast group corresponding to the received multicast packet.

In the figure, the router group 100 is shown connected to two switches S1 and S2. However, it will be understood that the number of switches S1 and S2 connected to the router group 100 is not limited. Further, it will be appreciated that the number of switches S1, S2, ie multicast agents, that are joined to one multicast group is also not limited.

The switches S1 and S2 will perform relayed multicasting. By way of example, switch S1 will receive a multicast packet from a transmitting multicast agent SMA or another multicast agent (eg, switch S2). Similarly, switch S2 will receive a multicast packet from a transmitting multicast agent SMA or another multicast agent (eg, switch S1).

In exemplary embodiments, the network system 10 may manage the hosts H1 to H3 connected to the switch S1 based on the Internet Group Management Protocol (IGMP). For example, the switch S1 snoops an Internet Group Management Protocol (IGMP) message from the hosts H1 to H3 of the host group 200 to obtain multicasting information, and the obtained multicasting information. We will do multicasting based on In an exemplary embodiment, the switch S1 may maintain a mapping table based on information of an IGMP join report (IGMP join report), a relayed multicasting protocol (RMCP) session, and an overlay tree. The switch S1 performs relay transmission multicasting with another switch S2 based on the mapping table, and forwards the multicast packet to the hosts H1 to H3 of the host group 200.

The session manager SM and the switches S1 and S2 will each be assigned an IP. By way of example, the IP of the session manager SM and the switches S1 and S2 will be assigned by the service provider. For example, assume that the IP of the switch S1 is "20.0.0.1". For example, assume that the IP of the switch S2 is "10.10.0.1". The switches S1 and S2 will have a Multicast Agent Identifier (MAID). For example, assume that the multicast agent ID MAID of the switch S1 is "101" and the multicast agent ID MAID of the switch S2 is "102".

2 is a flowchart illustrating a process of performing multicasting in the network system 10 of FIG. 1. 1 and 2, in step S110, the switch S1 / S2 receives a multicast subscription request. For the sake of brevity, assume that host H2 of host group 200 forwards the multicast subscription request to switch S1. However, the network system 10 according to the embodiment of the present invention is not limited to the transmission of a multicast subscription request from the host H2.

For example, the host H2 forwarding the multicast join request to the switch S1 may include that the host H2 sends an IGMP join report through the switch S1 to an edge router of the router group 100. In S120, the switch S1 may be performed by snooping an IGMP join report (S120). That is, the switch S1 will snoop the message from the host H2 when the destination of the message from the host H2 is a multicast address.

The switch S1 is a group information table having a multicast group address, an interface ID representing an interface connected to a host subscribed to the multicast group address, and a session ID generated based on the multicast group address and the session manager address. (GIT, Group Information Table) will be maintained. Table 1 shows an embodiment of a group information table.

Multicast Group Address (GA) Interface ID Session id GA1 One SID1 GA2 3 SID2

The multicast group address GA represents the addresses of the multicast groups to which the hosts H1 to H3 connected to the switch S1 are subscribed. The interface ID indicates a connection relationship between the switch S1 and the hosts H1 to H3. Referring to Table 1, it is shown that a host corresponding to the interface of the interface ID "1" of the switch S1 is joined to the multicast group corresponding to the multicast group address GA1. In exemplary embodiments, the interface ID may be a port number of the switch S1 to which the hosts H1 to H3 are connected. By way of example, host H1 is connected to port "1" of switch S1, host H2 is connected to port "2", and host H3 is connected to port "3".

The session ID is an ID for identifying a session to which the hosts H1 to H3 are subscribed. The session ID is generated by the switch S1 and will be generated by combining the IP address and multicast group address of the session manager SM.

In step S130, the switch S1 will check the group information table as described in Table 1 using the snooped IGMP join report.

3 is a flowchart illustrating a method of checking the group information table by the switch S1 of FIG. 1. 1 and 3, in step S210, the switch S1 has a multicast group address (address of an incoming multicast group) included in an IGMP join report transmitted from the host H2. Determine if it is registered at. For example, assume that the multicast group address of the IGMP join report delivered from the host H2 is GA1. In other words, it is assumed that the multicast group address requested to be subscribed by the host H2 is registered in the group information table GIT. At this time, after step S210 step S220 will be performed.

In operation S220, the switch S1 determines whether an interface ID of the host H2 is registered in the interface ID field corresponding to the multicast group address GA1 requested to be subscribed by the host H2. When the interface ID of the host H2 is registered in advance in the interface ID field corresponding to the multicast group address GA1 requested to be subscribed by the host H2, the group information table GIT check is finished. If the interface ID of the host H2 is not registered in advance in the interface ID field corresponding to the multicast group address GA1 requested to be subscribed by the host H2, the interface ID of the host H2 is registered in step S230. The group information table (GIT) check is finished. When the steps S210, S220, and S230 are performed, the group information table GIT of the switch S1 will be set as shown in Table 1 to Table 2.

Multicast Group Address (GA) Interface ID Session id GA1 1, 2 SID1 GA2 3 SID2

In step S210, it is assumed that the multicast group address GA3 requested to be joined by the host H2 is not registered in the group information table GIT. At this time, after step S210 step S240 will be performed.

In operation S240, the switch S1 registers the multicast group address GA3 requested to be subscribed by the host H2 to a new record of the group information table GIT. In step S250, the switch S1 registers the interface ID of the host H2 in the interface ID field corresponding to the multicast group address GA3 requested to be subscribed by the host H2. In operation S250, the switch S1 generates a session ID SID3 by combining the multicast group address GA1 requested by the host H2 and the address of the session manager SM. The switch S1 registers the generated session ID SID3 in the session ID field corresponding to the multicast group address GA3 requested to be subscribed by the host H2. Thereafter, the group information table (GIT) check is finished. When the steps S210, S240, S250 and S260 are performed, the group information table GIT of the switch S1 will be set as shown in Table 1 to Table 3.

Multicast Group Address (GA) Interface ID Session id GA1 One SID1 GA2 3 SID2 GA3 2 SID3

Referring back to FIGS. 1 and 2, in step S130, the group information table GIT is checked as described with reference to FIGS. 1 and 3.

The switch S1 includes a session ID and a multicast agent ID (MAID) of a parent multicast agent (PMA) indicating a multicast agent (MA) for sending multicast packets to the switch S1. Maintain a Session Information Table (SIT). The session information table (SIT) indicates information of a CMA pointer, a timer, and a PMA / neighbor multicast agent indicating a child multicast agent (CMA) receiving a multicast packet from a switch S1. It further includes a PMA / neighbor pointer. Table 4 shows an embodiment of a session information table (SIT).

Session id PMA MAID CMA pointer timer PMA / Neighbor Information Pointer SID1 102 * 10 * SID2 204 N / A 10 *

In operation S140, the switch S1 checks the session information table SIT.

FIG. 4 is a flowchart illustrating a method of checking the session information table SIT by the network system 10 of FIG. 1. 1 and 4, in step S310, the switch S1 checks the PMA MAID corresponding to the session ID corresponding to the multicast group requested to join from the host H2. The PMA MAID field will include one of Blank, Preset Value, and PMA MAID. If the PMA MAID is a preset value, it will indicate that the PMA of the switch S1 is not registered. If the PMA MAID is blank, the switch S1 will indicate that it is performing a process to register the PMA. The MAID described in the PMA MAID will represent a PMA for sending a multicast packet corresponding to the session ID to the switch S1.

For example, when the session ID of the multicast group requested to join from the host H2 is "SID1" (S320) as described with reference to Table 2, the MAID is displayed in the PMA MAID field corresponding to the session ID "SID1". "101" is described. At this time, the switch S1 is set to receive the multicast packet from the switch S2 corresponding to the MAID " 101 " and joins the multicast group corresponding to the session ID " SID1 "

For example, when the session ID of the multicast group requested to join from the host H2 is "SID3" as described with reference to Table 3 (S320), the PMA corresponding to the session ID "SID3" is not registered. Therefore, the switch S1 generates a session join request message (S330). The switch S1 will generate a session join request message including the session ID "SID3" of the multicast group requested to join from the host H2 and the MAID of the switch S1. The switch S1 will encapsulate the generated session join request message in TCP / IP. In the encapsulation operation, the source IP address will be the IP address of the switch S1 and the destination IP address will be the IP address of the session manager SM.

In operation S340, the switch S1 transmits an encapsulated session join request message. The switch S1 will access the neighbor information table with reference to the PMA / Neighbor Information Pointer. The neighbor information table will contain general information for the switch S1 to communicate with the outside. The neighbor information table S1 will be maintained at the switch S1. The switch S1 may send a session join request message to the session manager SM with reference to the neighbor information table.

In operation S350, the switch S1 sets the PMA MAID field corresponding to the session ID "SID3" to a blank. The PMA MAID field set to blank will indicate that the switch S1 is accessing the session manager SM to set up the PMA. Thus, even if a join request for the multicast group corresponding to the session ID " SID3 " is transmitted from other hosts H1 and H3, the switch S1 will not generate a session join request message if the PMA MAID field is blank. . That is, the transmission of the session join request message in duplicate for the same multicast group is prevented.

In operation S360, the switch S1 receives a subscription permission message from the session manager SM. The subscription grant message sent from the session manager SM will include the session ID "SID3". The switch S1 will register the session ID "SID3" in the session ID field of the session information table SIT. As another example, the switch S1 receives the session ID " SID3 " from the session manager SM and registers it in the session information table SIT, instead, as described with reference to FIGS. 1 and 3, the group information table GIT. It will be appreciated that the session ID " SID3 " generated with reference to FIG. 2 may be registered in the session information table SIT. It will be appreciated that the session ID " SID3 " may be registered in the session information table SIT before step S310, after step S370, or between steps S310 and S370.

Referring back to FIGS. 1 and 2, in step S140, the switch S1 checks the session information table SIT as described with reference to FIGS. 1 and 4. The subscription grant message sent from the session manager SM will include a list of multicast agents MA already subscribed to the multicast group corresponding to the session ID " SID3 ". In step S150, the switch S1 refers to the list of multicast agents MA delivered from the session manager SM, and joins the multicast agent MA that is joined to the multicast group corresponding to the session ID "SID3". Will send a relay transfer request message. If the relay transmission request is denied, the switch S1 will send a relay transmission request message to another multicast agent MA in the list.

When the relay transmission permission message is transmitted from the multicast agent MA, the switch S1 registers the MAID of the multicast agent MA that has transmitted the relay transmission permission message in the PMA MAID field of the session information table SIT and sets a timer. Update the. Thereafter, the switch S1 will receive a multicast packet corresponding to the session ID " SID3 " from the multicast agent MA registered with the PMA MAID. The timer will be updated to a preset value when a relay transmit permission message is sent from the PMA. When the preset time for the timer has elapsed, the switch S1 will search for a new PMA. That is, if a multicast packet or message is delivered from the PMA within the time set for the timer, the switch S1 will maintain communication with the PMA.

The switch S1 will further maintain a Multicast Agent Information Table (MAIT) containing information about the Multicast Agent (MA). In an example, the multicast agent information table (MAIT) may include information about the MAID, the address of the MA (eg, an IP address), the port number of the MA, and the interface ID of the MA. An embodiment of a multicast agent information table (MAIT) is described in Table 5.

MAID Destination address Port number Interface ID 102 10.10.0.1 xxxx 5 201 20.0.0.4 yyyy 5 202 30.0.0.3 zzzz 6 203 40.0.0.2 kkkk 6 204 50.0.0.5 hhhh 4

 The port number of the MA may be the number of an application port. By way of example, the port number of the MA may be the TCP / UDP port number of the MA. By way of example, if a new PMA is registered in the session information group, the switch S1 will register the information of the new PMA in the multicast agent information table MAIT.

For example, when the MAID of the PMA of the switch S1 is registered, the PMA / neighbor information pointer of the session information table SIT of Table 4 is a PMA field of the multicast agent information table MAIT of the switch S1. Will indicate. If the PMA of the switch S1 is not set, the PMA / Neighbor Information Pointer will indicate the neighbor information table. In other words, if the MAID of the PMA is registered, the switch S1 will access the multicast group via the PMA. If the MAID of the PMA is not registered, the switch S1 will access the multicast group through the neighbor information table.

FIG. 5 is a flowchart illustrating an operation of a switch receiving a multicast packet in the network system 10 of FIG. 1. 1 and 5, in step S410, the switch S1 receives a multicast packet through the router group 100. In step S420, the switch S1 analyzes the multicast packet. In operation S430, the switch S1 determines whether a relayed multicast protocol message is included in the multicast packet. If the multicast packet does not include the relay transmission message, the switch S1 will forward the multicast packet to the host and the CMA that are subscribed to the multicast group corresponding to the received multicast packet (S440).

If the forwarded multicast packet includes a relay transmission request message, in step S450, the switch S1 checks the maximum amount of relay transmission allowed and determines whether to relay transmission according to the check result. When the relay transmission amount being used by the switch S1 is smaller than the maximum relay transmission allowed to the switch S1, the switch S1 determines whether the multicast group corresponding to the multicast packet is being served by the switch S1. (S460).

Referring to the session information table of Table 4, a value corresponding to "SID3" does not exist in the session ID field. In other words, the multicast group corresponding to the session ID " SID3 " is not served by the switch S1. The PMA MAID of the multicast group corresponding to the session ID "SID1" is "101", and a CMA pointer is also set. That is, the multicast group corresponding to the session ID " SID1 " is being serviced by the switch S1.

The switch S1 may maintain a relayed information table (RIT) for managing relay transmission information. In exemplary embodiments, the relay transmission information table (RIT) may include a session ID, a MAID, a CMA pointer, a timer, and a CMA information pointer. An embodiment of the relay transmission information table (RIT) is shown in Table 6.

Session id MAID CMA pointer timer CMA Information Pointer SID1 201 * 10 * SID1 202 * 10 * SID1 203 N / A 10 *

The CMA pointer of the session information table (SIT) will indicate the first CMA of the relay transmission information table (RIT). The CMA pointer of the relay transmission information table (RIT) will indicate the CMA in the following order. That is, the CMA pointer of the last CMA of the relay transmission information table (RIT) will not be set. By way of example, in the relay transmission information table (RIT), the CMA pointer corresponding to MAID "201" will indicate a record corresponding to MAID "202". The CMA pointer corresponding to MAID "202" will represent the record corresponding to MAID "203".

The next CMA indicated by the CMA pointer of the relay transmission information table RIT is not set according to the record order of the relay transmission table. The next CMA indicated by the CMA pointer of the relay transmission table (RIT) is set by the relay transmission tree. By way of example, in the relay transport tree, the CMA in the order of the multicasting agent (MA) of MAID "201", the multicasting agent (MA) of MAID "202", and the multicasting agent (MA) of MAID "203". Suppose it is set. At this time, as described with reference to Table 6, the CMA pointer of the session information table (SIT) will indicate a record of the relay transmission information table (RIT) corresponding to the MAID "201". In the relay transmission information table RIT, the CMA pointer of the record corresponding to the MAID "201" indicates the record corresponding to the MAID "202", and the CMA pointer of the record corresponding to the MAID "202" indicates the MAID "203". And the CMA pointer field of the record corresponding to MAID " 203 " will have a null value.

As another example, in the relay transport tree, the CMA is in the order of the multicasting agent (MA) of MAID "203", the multicasting agent (MA) of MAID "201", and the multicasting agent (MA) of MAID "202". Suppose it is set. At this time, the CMA pointer of the session information table (SIT) will indicate a record of the relay transmission information table (RIT) corresponding to the MAID "203". In the relay transmission information table RIT, the CMA pointer of the record corresponding to the MAID "203" indicates the record corresponding to the MAID "201", and the CMA pointer of the record corresponding to the MAID "201" indicates the MAID "202". And the CMA pointer field of the record corresponding to MAID "202" will have a null value.

The timer of the relay transmission information table (RIT) will have a preset value. The timer will be updated upon receiving a relay transfer request from the CMA. When the preset time for the timer has elapsed, the switch S1 will delete the record for the CMA whose timer has elapsed. That is, if a message is delivered from the CMA within the time set in the timer, the switch S1 will maintain communication with the CMA. The CMA information pointer will indicate the record corresponding to the CMA among the records of the multicast agent information table (MAIT).

By way of example, it is assumed that the forwarded multicast packet includes a relay transmission request for the multicast group corresponding to the session ID "SID1". The switch S1 accesses along the CMA pointer of the relay transmission information table RIT until the value of the CMA pointer field of the relay transmission information table RIT becomes a null value. The switch S1 registers information of the multicast agent MA that has transmitted the relay transmission request message in a new record of the relay transmission information table RIT (S460). Then, the switch S1 writes a pointer indicating a new record to a CMA pointer including a null value, and sets the CMA pointer of the new record to null.

In operation S480, the switch S1 registers information on the multicast agent that has transmitted the relay transmission request message in the multicast agent information table MAIT. If the multicast agent MA that has sent the relay transmission request message has already been registered in the multicast agent information table MAIT, the switch S1 indicates that the CMA information pointer of the new record in the relay transmission information table RIT is multicast. The CMA information pointer will be set to indicate the record corresponding to the multicast agent MA that sent the relay transfer request message of the agent information table MAIT.

As described above, the network system 10 according to an embodiment of the present invention uses a switch connected to a plurality of hosts as a multicasting agent, instead of using the hosts as a multicasting agent. In addition, the switch performs relay transmission multicasting by using the switch's IGMP snooping function. By way of example, the hosts H1-H6, see 1, may be IPTV setup boxes. By way of example, switches S1, S2, see FIG. 1, will be provided one per building. According to the present invention, it is possible to perform relay transmission multicasting, regardless of the service scheme of IPTV service providers, i.e., the specification of the IPTV setup box. Accordingly, it will be appreciated that according to the present invention, a network efficient network system is provided.

In the detailed description of the present invention, specific embodiments have been described, but it is obvious that various modifications can be made without departing from the scope and spirit of the present invention. Therefore, the scope of the present invention should not be limited to the above-described embodiments, but should be determined by the claims equivalent to the claims of the present invention as well as the claims of the following.

1 is a block diagram illustrating a network system according to an exemplary embodiment of the present invention.

2 is a flowchart illustrating a process of performing multicasting in the network system of FIG. 1.

3 is a flowchart illustrating a method of checking a group information table by a switch of FIG. 1.

4 is a flowchart illustrating a method of checking a session information table by the network system of FIG. 1.

FIG. 5 is a flowchart illustrating an operation of a switch receiving a multicast packet in the network system of FIG. 1.

Claims (10)

A method of operating a switch connected between a router group comprising at least one router and at least one host: Starting a multicast service in response to a request of the at least one host; Receiving a packet corresponding to the multicast service from the router group; Relaying the received packet to another multicast agent through the router group; And Forwarding the received packet to the at least one host that requested the multicast service, Starting the multicast service Snooping messages delivered from the at least one host to a particular router in the router group to detect a request for the multicast service of the at least one host. The method of claim 1, The router group operates on a unicast basis. The method of claim 1, The specific router is configured to manage the group of the at least one host, Detecting the request of the multicast service of the at least one host Snooping a group management message from the at least one host to the particular router. The method of claim 1, Starting the multicast service And if the subscription request for a specific multicast group is detected from the at least one host and is servicing the specific multicast group, serving the specific multicast group to the at least one host. The method of claim 1, Starting the multicast service If a join request for a particular multicast group is detected from the at least one host, and the particular multicast group is not in service, joining the particular multicast group and attaching the particular multicast group to the at least one host. Service method further comprising the step of serving. The method of claim 5, Joining the specific multicast group and servicing the specific multicast group to the at least one host Forwarding a join request of the particular multicast group to a session manager of the particular multicast group through a sender transmitting the packet of the particular multicast group. The method of claim 1, The switch is generated based on an address of a serviced multicast group, an interface ID representing an interface connected to a host subscribed to the serviced multicast group, and an address of the serviced multicast group and an address of a session manager. A group information table having a session ID, Starting the multicast service If a subscription message corresponding to a specific multicast group is received from the at least one host, and the address of the specific multicast group is registered in the group information table, And adding an interface ID of an interface connected to the at least one host to an interface ID field corresponding to the address of the specific multicast group in the group information table. The method of claim 7, wherein Starting the multicast service If the address of the specific multicast group is not registered in the group information table, the address of the specific multicast group is registered in the group information table and based on the address of the session manager and the address of the specific multicast group. Generating a session ID, and registering the generated session ID in the group information table. The method of claim 8, The switch further includes a session information table having a session ID and a Parent Multicast Agent (PMA) ID indicating a multicast agent transmitting the packet to the switch, Starting the multicast service And if the ID of the parent multicast agent of the specific multicast group is not registered in the parent multicast agent ID field of the session information table, sending a session join request to the session manager. The method of claim 9, Starting the multicast service Receiving a list of multicast agents pre-subscribed to the specific multicast group from the session manager, and requesting relay transmission from a multicast agent pre-subscribed to the specific multicast group.

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