Abstract:
A method for providing IP multicast service using a VLAN in a network including an IP multicast/VLAN manager for supporting an IGMP and a GVRP, and multicast group members, includes: after generating an IP multicast group, allowing a sender to request the IP multicast/VLAN manager to search for at least one host joining the IP multicast group; allowing the IP multicast/VLAN manager to check whether the host supports the VLAN; and allowing the sender to transfer a packet through the VLAN if the host joining the IP multicast group supports the VLAN and allowing the sender to broadcast a packet though IP multicast if not.

Description:
BACKGROUND OF THE INVENTION 
   1. Field of the Invention 
   The present invention relates to a method for providing IP (Internet Protocol) multicast service using a virtual LAN (Local Area Network), and more particularly to a method for providing IP multicast service using a virtual LAN, wherein the method can provide efficient multicast service in a very high-speed network and rapidly process data by applying the virtual LAN to the IP multicast service. 
   2. Description of the Prior Art 
   Generally, multicasting is a data transmission method capable of efficiently employing resources of a network, whereby a specific group is organized and data is broadcast to a corresponding group so that the number of data transmissions by one sender can be reduced. Thus, the sender can send data to countless receivers through one data transmission, and the data is prevented from being sent to a destination if the destination does not want to receive the data, thereby preventing unnecessary network use (RFC 1112: Host Extensions for IP Multicasting, S. Deering, August 1989). Moreover, IP multicasting can maximally utilize bandwidth, maximally reduce a sender load, and efficiently employ the resources of the network. However, there is a problem in that, because the IP multicast necessarily needs software to carry out operations associated with a lower-order physical layer and a higher-order network layer, the IP multicast cannot acquire a desired bit rate in a very high-speed network. Moreover, there is a disadvantage in that all equipment in the network (including router, etc.) should support the IP multicast. 
   On the other hand, a VLAN (Virtual Local Area Network) is restricted to a configuration of a physical network by Network Administrator. In the VLAN, a logical network between network components can be flexibly formed and a bit rate is very high. That is, where a new network is configured, the network does not have to be physically configured, thereby saving costs for physically configuring the network. Through a VLAN function, the new network can be logically configured without any physical variation. The VLAN includes a port based VLAN, a layer  2  based VLAN and a policy based VLAN according to a user&#39;s network (IEEE 802.1Q, Virtual Bridged Local Area Network, IEEE 802.1, December 1998). Because the VLAN is implemented by hardware, it can achieve a relatively high bit rate. As the user cannot change or re-configure the network, only Network Administrator is able to change it. Furthermore, the VLAN is based on a protocol such as a GMRP (GARP Multicast Registration Protocol) for multicast communication, but the protocol support only single multicast address, so that this protocol is not able to make multiple multicast addresses. 
     FIG. 1  roughly shows a conventional IP multicast structure. Referring to  FIG. 1 , in a case of the conventional IP multicast, session information is transferred through an SDP (Session Description Protocol) and a host as a member desiring to join or leave a group can join or leave the group associated with a “JoinHostGroup/LeaveHostGroup” process through an IGMP (Internet Group Management Protocol). As described above, the member&#39;s joining or leaving is managed by an IGMP router  11  as a multicast router through the IGMP. Thus, data is sent to only joiners in the groups of a network A  12  and a network B  13 . In this method, IGMP routers  11  should necessarily carry out all operations associated with OSI (Open Systems Interconnection) 1st˜3rd layers  14 . Where the amount of traffic increases and the joining or leaving of group members frequently occurs, there is a problem in that the IGMP routers  11  should carry a heavy load. 
   On the other hand,  FIG. 2  roughly shows a conventional VLAN structure. The VLAN forms one group by designating a sub-network management group between network devices through a GVRP (GARP VLAN Registration Protocol)  22 . That is, the group formed through the GVRP  22  can be identified as a group formed by the VLAN. Accordingly, data sent from the sender  21  is broadcast to the group formed through the GVRP  22 . Since the GVRP  22  is a hardware-based protocol, a bit rate in the GVRP  22  is very high, but the user cannot readily intervene in the GVRP  22  and only a network device manager can directly intervene in the GVRP  22 . 
   On the other hand, as a prior art patent associated with an IP multicast/VLAN, there is U.S. Pat. No. 6,112,251 entitled “Virtual Local Network for Sending Multicast Transmission to Trunk Station”, Anil G. Rijhsinghani, August 2000. As disclosed in the prior art patent, both IP multicast information and VLAN information is contained in a protocol header so that network equipment can use only information capable of being processed by its own equipment and therefore have flexibility.  FIG. 3  shows a structure of the IP multicast/VLAN disclosed in the prior art patent. Where a message having the protocol header containing both IP multicast information and VLAN address information is sent to a network in  FIG. 3 , network equipment  31 ,  32  and  33  selects and processes desired information between the IP multicast information and the VLAN address information. However, there is a problem in that a multicast group manager is not considered in the IP multicast/VLAN and that the network equipment should support a specific protocol disclosed in the prior art patent. 
   With regard to a combination of the VLAN and the IP multicast, only a protocol has been proposed, and structures and detailed operations of management programs have not been yet proposed. In particular, upon combining the VLAN and the IP multicast, problems associated with a network&#39;s transmission speed and global utility should be addressed. 
   SUMMARY OF THE INVENTION 
   Therefore, the present invention has been made in view of the above problems, and it is an object of the present invention to provide a method for providing IP (Internet Protocol) multicast service using a virtual LAN (Local Area Network), the method being capable of providing the IP multicast service at a desired bit rate in a very high-speed network by introducing the virtual LAN supported by a lower-order layer to IP multicast. 
   In accordance with one aspect of the present invention, the above and other objects can be accomplished by the provision of a method for providing IP (Internet Protocol) multicast service using a VLAN (Virtual Local Area Network) in a network including an IP multicast/VLAN manager for supporting an IGMP (Internet Group Management Protocol) and a GVRP (GARP VLAN Registration Protocol), and multicast group members, comprising the steps of: a) after generating an IP multicast group, allowing a sender to request the IP multicast/VLAN manager to search for at least one host joining the IP multicast group; b) allowing the IP multicast/VLAN manager to check through a router directly coupled to the host whether the host supports the VLAN; and c) allowing the sender to transfer a packet through the VLAN if the host joining the IP multicast group supports the VLAN and allowing the sender to broadcast a packet through IP multicast if the host joining the IP multicast group does not support the VLAN. 
   Preferably, the IP multicast/VLAN manager may performs an IP multicast router and the sender may select the IP multicast/VLAN manager. 
   Preferably, the step a) may further include the steps of: a1) allowing the sender to request the IP multicast/VLAN manager to manage registration or withdrawal of a host in and from the generated IP multicast group; a2) allowing the sender to give notice of a multicast session through an SDP (Session Description Protocol) if the IP multicast/VLAN manager accepts the request; and a3) allowing the IP multicast/VLAN manager to register or withdraw the host in and from the IP multicast group if the host requests the IP multicast/VLAN manager to register or withdraw the host in and from the IP multicast group. At this time, the SDP may have a new field so that the IP multicast group can use the VLAN, and the host may be registered in the VLAN and the IP multicast group using the SDP. 
   Preferably, the step c) may include the step of: if the host supports both VLAN and IP multicast, allowing the sender to primarily transfer the packet using the VLAN and to secondarily transfer the packet using the IP multicast. 
   The present invention relates to a method for providing IP multicast service using a VLAN. The present invention can improve a bit rate of the IP multicast service by applying the VLAN to the conventional IP multicast and provide a method for providing an IP multicast service using the VLAN so that efficient communication can be enabled. The pre-existing IP multicast network is made up of a multicast router and multicast group members and the pre-existing VLAN is made up of network equipment and VLAN members. However, the IP multicast network using the VLAN in accordance with the present invention includes the IP multicast/VLAN manager as network equipment of the IP multicast/VLAN and multicast group members. 
   The IP multicast/VLAN manager simultaneously supports the IGMP and the GVRP, and transfers and manages group information by converting the generated IP multicast group into a VLAN group. Moreover, the IP multicast/VLAN manager primarily transfers multicast information upon transferring the multicast information, and processes and manages the SDP. As described above, the present invention can equally handle the IP multicast group and the VLAN group generated by the IGMP and the GVRP by adding a function of supporting the GVRP of the VLAN to the pre-existing multicast router. 

   
     BRIEF DESCRIPTION OF THE DRAWINGS 
     The invention will be described in detail with reference to the following drawings in which like reference numerals refer to like elements wherein: 
       FIG. 1  is a view illustrating a conventional structure of an IP (Internet Protocol) multicast network; 
       FIG. 2  is a view illustrating a conventional structure of a virtual LAN (Local Area Network); 
       FIG. 3  is a view illustrating a conventional integrated structure of an IP multicast/virtual LAN; 
       FIG. 4  is a view illustrating a structure of an IP multicast/virtual LAN in accordance with an embodiment of the present invention; and 
       FIG. 5  is a flow chart illustrating a procedure of registering and withdrawing a host of a multicast group in and from an IP multicast/virtual LAN in accordance with the present invention. 
   

   DESCRIPTION OF THE PREFERRED EMBODIMENTS 
   The above-described object, features and advantage of the present invention will become apparent from the following detailed description. Now, preferred embodiments of the present invention will be described in detail with reference to the annexed drawings. 
     FIG. 4  is a view illustrating a structure of an IP (Internet Protocol) multicast/VLAN (Virtual Local Area Network) in accordance with an embodiment of the present invention. Referring to  FIG. 4 , a plurality of networks  400  and  410  are coupled to a plurality of routers  42 ,  43 ,  44  and  45  in the structure of the IP multicast/VLAN in accordance with the present invention. An IP multicast/VLAN manager  42  for supporting an IGMP (Internet Group Management Protocol) and a GVRP (GARP VLAN Registration Protocol), and multicast group members  47  are basically configured in the IP multicast/VLAN. The IP multicast/VLAN includes a router  44  supporting the VLAN/IP multicast and a router  45  supporting the IP multicast. The IP multicast/VLAN manager  42  further performs as an IP multicast router. At this time, the IP multicast/VLAN manager  42  is preferably selected by a sender  41 , which desires to send an IP multicast packet. The sender  41  requests the IP multicast/VLAN manager  42  to announce multicast session and make the multicast group  47  using an SDP (Session Description Protocol) so that the IP multicast packet can be sent to a desired multicast group  47 . In response to the request, the IP multicast/VLAN manager  42  sends a message, necessary for checking whether hosts belonging to the multicast group  47  can support the VLAN, to the routers  44  and  45  coupled to the host group  47 . At this time, the IP multicast/VLAN manager  42  sends the message, necessary for checking whether the hosts belonging to the host group  47  can support the VLAN, to the routers  44  and  45  through a plurality of routers  43  (including routers not shown in  FIG. 4 ). The routers  44  and  45  then send an acknowledgement message to the IP multicast/VLAN manager  42  if the hosts of the multicast group  47  support the VLAN. If not, the routers  44  and  45  do not send the acknowledgement message to the IP multicast/VLAN manager  42 . In  FIG. 4 , the network  400  supports the VLAN, but the network B  410  does not support the VLAN. 
   On the other hand, a host as a group member desires to join or leave the multicast group  47 , which wants to use the IP multicast service, joins or leaves the multicast group  47  through the IGMP. If a network (e.g., the network A  400 ) associated with a host, joining the multicast group  47 , which desires to use the IP multicast service, supports the VLAN, a VLAN sub-network group  47 - 1  joining an IP multicast group is formed within the network A  400 . A packet is broadcast to the VLAN sub-network group  47 - 1  through the VLAN. In this case, the IP multicast/VLAN manager  42  interprets the broadcasting of the packet to the VLAN sub-network group  47 - 1  as the IP multicast. However, the IP multicast/VLAN manager  42  transfers the packet to a host  47 - 2  contained in the network B  410 , which doesn&#39;t support the VLAN, through the IP multicast. The IP multicast/VLAN manager  42  further transfers the packet to a VLAN unavailable area through the IP multicast. 
   A new protocol field is added to the SDP so that an IP multicast network can use the VLAN. That is, a new field is added to a VLAN packet so that the VLAN packet is transferred as an IP multicast packet. Accordingly, the VLAN and the IP multicast network can be simultaneously employed. For this, hosts, desiring to use the IP multicast service, register themselves in a VLAN group and an IP multicast group. Further, when the IP multicast service is provided in the IP multicast/VLAN, it is determined whether a host, desiring to use the IP multicast service, supports the VLAN. If the host, desiring to use the IP multicast service, supports the VLAN, the IP multicast/VLAN broadcasts a packet to the hosts through the VLAN first. If not, the IP multicast/VLAN broadcasts a packet to the hosts through the IP multicast. At this time, since the packet transferred through the VLAN can include the packet transferred through the IP multicast, the amount of work to be processed by a higher-order layer  46  is reduced and therefore the amount of work to be processed by network equipment is reduced, when the packet is transferred through the IP multicast. 
     FIG. 5  is a flow chart illustrating a procedure of registering and withdrawing a host of a multicast group in and from the IP multicast/virtual LAN in accordance with the present invention. The IP multicast/VLAN manager  42  in accordance with the present invention carries out a procedure of registering and withdrawing a host in and from the IP multicast/virtual LAN. Referring to  FIG. 5 , the sender  41  generates a multicast group at step  501 . Through the IGMP, the sender  41  requests the IP multicast/VLAN manager  42  to manage joining or leaving of a host of the generated multicast group at step  502 . The IP multicast/VLAN manager  42  accepts or rejects the request at step  503 . If the IP multicast/VLAN manager  42  rejects the request at step  503 - 1 , the IP multicast/VLAN manager  42  completes a procedure of registering and withdrawing a host of the multicast group in and from the IP multicast/virtual LAN. On the other hand, if the IP multicast/VLAN manager  42  accepts the request at step  503 - 2 , the sender  51  broadcasts multicast session information to hosts through the SDP (Session Description Protocol: RFC 2327) at step  504 . To use the VLAN in the IP multicast network, the SDP has the following additional protocol items. 
   At this time, the IP multicast/VLAN manager  42  stores a VLAN ID within the reception range of the SDP at step  505 . If a host receiving the multicast session information broadcast from the sender  41  desires to join the multicast group, the host applies to the IP multicast/VLAN manager  42  through the IGMP for joining the multicast group at steps  506  and  507 . If multicast communication is permitted within a management range of the IP multicast/VLAN manager  42 , the IP multicast/VLAN manager  42  forms a new VLAN using the stored VLAN ID at step  508 . The IP multicast/VLAN manager  42  checks an application message sent from the host desiring to join the multicast group and determines whether data can be transferred to the host through the newly formed VLAN. If data can be transferred to the host through the newly formed VLAN, the IP multicast/VLAN manager  42  transmits the data to the host through the VLAN. If not, the IP multicast/VLAN manager  42  transmits the data to the host through the IP multicast at step  509 . On the other hand, if the IP multicast/VLAN manager  42  receives a message indicating the host&#39;s leaving from the group through the IGMP, it withdraws the host from the VLAN group and the IP multicast group. When the IP multicast/VLAN manager  42  registers or withdraws the host in or from the IP multicast/VLAN, it may use the GMRP, but it does not use the GMRP in the present invention. The reason why the GMRP is not used in the present invention is because the GMRP&#39;s multicast address is “0x01-80-C2-00-00-20” and a process due to the generated groups is complicated when a plurality of groups are generated. 
   The above-described detailed description and drawings of the present invention have been described in terms of preferred embodiments solely for the purpose of illustration. The present invention is not limited to the embodiments described, but may be defined only by the spirit and scope of the appended claims. 
   As apparent from the above description, the present invention can provide a method for providing IP multicast service using a virtual LAN, wherein the method can reduce the amount of work processed by network equipment upon transmitting a packet, because a process of a higher-order layer is not needed, as in the conventional IP multicast, and enable multicast communication to be efficiently used in very high-speed communication system of a Gbps class. 
   Moreover, the method of the present invention can improve utility, because both VLAN and IP multicast are used, and allow a user to arbitrarily generate a VLAN group. The method can be implemented by software rather than special equipment, thereby minimizing costs for implementing the method. 
   The above-described detailed description and the drawings are not intended to limit the present invention, and those skilled in the art will appreciate that various modifications, additions and substitutions are possible, without departing from the scope and spirit of the present invention.