Abstract:
In order to maintain the reliability of telecommunication by means of the multicast wireless communication when IP multicast is used in the IP broadcast service, the network system includes a transfer apparatus for transferring multicast packets and transfer request packets and a network apparatus for receiving transfer request packets and for transferring the multicast packets to be distributed. The transfer apparatus transmits transfer requests together with transfer request packets when it transmits multicast packets to the receiver requiring unicast communication, and the network apparatus receives multicast packets, sets the destination MAC address of the multicast packet as the unicast MAC address of the receiver in response to the conversion request from the transfer apparatus and transfers multicast packets.

Description:
CLAIM OF PRIORITY 
       [0001]    The present application claims priority from Japanese application JP 2007-212834 filed on Aug. 17, 2007, the content of which is hereby incorporated by reference into this application. 
       FIELD OF THE INVENTION 
       [0002]    The present invention relates to a data transfer system and in particular to a data transfer system for transmitting and receiving IP multicast packets. 
       BACKGROUND OF THE INVENTION 
       [0003]    The telecommunication network infrastructure has been developing and in addition to the traditional data transfer such as web, mail and the like, data transfer of movie or voice and the like is performed on telecommunication networks, and in particular movie data are transferred by multicast. And as a result of the telecommunication network as an infrastructure, the use of telecommunication networks is increasing at home. In the case of home network, not only wired communication but also wireless communication is widely used because of ease of use. 
         [0004]    Because of changes in the state of radio wave used in wireless communication, no reliability corresponding to that of wired communication in physical layer can be maintained. Therefore, according to the technology described in “IEEE, AN SI/IEEE Std 802.11, 1999 Edition (R2003),” the mechanism of acknowledging and retransmitting data transfer in the wireless communication set forth in IEEE 802.11 is specified. However, the acknowledgment and retransmission of data transfer in wireless communication are specified only when the wireless communication method is unicast, and they are not specified when the wireless communication method is multicast. 
         [0005]    The method of wireless communication is associated with the MAC layer of the transfer data, and the unicast is adopted when the destination address of the MAC layer is the unicast address while the multicast is used when the destination address of the MAC layer is the multicast address. In the multicast used for the broadcast-type distribution of movies, the destination address of the MAC layer is multicast address. Consequently, the data transfer in wireless communication is not acknowledged and retransmitted and as a result their reliability cannot be maintained. 
         [0006]    Accordingly, in a multicast communication, in order to maintain reliability by means of the acknowledgment and retransmission of data transfer in wireless communication, JP-A No. 2006-333309 describes a technology of converting a multicast communication into a unicast communication by the transmitter of wireless communication, and reconverting the unicast communication into the multicast communication by the receiver. 
         [0007]    And JP-A No. 2007-049382 describes the technology of converting the destination address of the MAC layer of multicast communication from multicast address to unicast address by a transfer apparatus which is a wireless communication apparatus. Since the application that receives a multicast communication processes data in the IP layer, according to the method of converting multicast communication including the IP layer to unicast communication like the technology described in JP-A No. 2007-333309, it is necessary to reconvert to multicast communication. However, according to the method of converting the MAC layer of the multicast communication into the unicast communication and leaving the IP layer in the multicast communication mode like the technology described in JP-A No. 2007-049382, there is no need to reconvert. 
         [0008]    And JP-A No. 2004-242063 describes the technology of converting the destination address of the MAC layer of multicast communication from the multicast address to the unicast address irrespective of the wireless communication. 
       SUMMARY OF THE INVENTION 
       [0009]    When the multicast communication is converted into the unicast communication in order to acknowledge and retransmit data transfer in a wireless communication, it is necessary to process the control protocol of multicast communication, to manage the receiver for multicast communication, reproduce multicast communication packets when there are a plurality of receivers according to the information for managing the receivers for multicast communication, and convert the destination address for multicast communication. The processing required for the conversion of these multicast communications will be new load processing for the wireless communication apparatuses. This is the first problem that the present invention tries to solve. 
         [0010]    And in the case of converting multicast communication in an apparatus different from the wireless communication apparatus, the receivers requiring the conversion of multicast communication for the sake of wireless communication cannot be identified. This is the second problem which the present invention tries to solve. 
         [0011]    A representative example of the present invention is as follows. Specifically, a network system connected with a transmitter for distributing multicast packets and a receiver for transmitting a transfer request packet of the multicast packets to be distributed and for receiving the multicast packets to be distributed, the network system including a transfer apparatus for transferring the multicast packets and the transfer request packets and a network apparatus for receiving the transfer request packets and for transferring the multicast packets to be distributed, the transfer apparatus including two interfaces including a first interface and a second interface, a receiver-transmitter for receiving the transfer request packets for multicast packets through the first interface and for transmitting the transfer request packets through the second interface, the transmitter-receiver transmitting the conversion requests for requesting that the source unicast MAC addresses of the transfer request packets be set as the destination MAC addresses of the multicast packets together with the transfer request packets when it transmits the multicast packets to the receiver requiring unicast communication, the network apparatus including a receiver for receiving the multicast packets, a holding unit for holding the unicast MAC addresses and the multicast MAC addresses used for transferring the received multicast addresses, a reproduction unit for reproducing the same number of the multicast packets as the number of the held unicast MAC addresses and multicast MAC addresses, and a transfer unit for setting any one of the held unicast MAC address and multicast MAC address as the destination MAC address of each of the reproduced multicast packets and transferring the multicast packets in which the destination MAC addresses were set. 
         [0012]    According to an embodiment of the present invention, the network apparatus determines whether it is necessary to process the conversion of multicast communication for each receiver terminal, and converts the destination addresses of the MAC layer from the multicast addresses to the unicast addresses when the conversion of the multicast communication is necessary, and does not convert from the multicast addresses to the unicast addresses when the conversion of the multicast communication is not necessary. 
         [0013]    Therefore, since the multicast communication is not converted in the wireless communication apparatus, it is possible to alleviate the load of the wireless communication apparatus. And it is possible to convert the multicast communication at the receiver terminal for wireless connection, and to maintain the reliability by the acknowledgment and retransmission of data transfer by wireless communication. Furthermore, it is possible to maintain the simultaneous transmission of the same contents and efficiency of multicasting communication by the receiver terminal of wired connection. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0014]      FIG. 1  is the block diagram of the network according to the first embodiment of the present invention; 
           [0015]      FIG. 2  shows the state of various layers of the IP multicast transmission start request and the IP multicast transmission stop request transmitted and received by various apparatuses shown in  FIG. 1  according to the first embodiment of the present invention; 
           [0016]      FIG. 3  shows the state of various layers of the IP multicast transmitted and received by various apparatuses shown in  FIG. 1  according to the first embodiment of the present invention; 
           [0017]      FIG. 4  is the block diagram of the network apparatus according to the first embodiment of the present invention; 
           [0018]      FIG. 5  shows the routing information table according to the first embodiment of the present invention; 
           [0019]      FIG. 6  shows the MAC conversion information table according to the first embodiment of the present invention; 
           [0020]      FIG. 7  shows a routing information table obtained by adding the MAC conversion information table to the routing information table according to the first embodiment of the present information; 
           [0021]      FIG. 8  is a block diagram of the wireless transfer apparatus according to the first embodiment of the present information; 
           [0022]      FIG. 9  is the block diagram of a network apparatus obtained by adding the function of a wireless transfer apparatus to the network apparatus according to the first embodiment of the present invention; 
           [0023]      FIG. 10  is a sequence diagram for processing the IP multicast transmission start request and the IP multicast transmission stop request from a wireless terminal requiring the conversion of the MAC layer according to the first embodiment of the present invention; 
           [0024]      FIG. 11  is a sequence diagram for processing the IP multicast transmission start request and the IP multicast transmission stop request from a wired terminal not requiring the conversion of the MAC layer according to the first embodiment of the present invention; 
           [0025]      FIG. 12  shows a flowchart for processing the routing control of the network apparatus according to the first embodiment of the present invention; 
           [0026]      FIG. 13  shows a flowchart for processing the multicast transmission start/stop request of the network apparatus according to the first embodiment of the present invention; 
           [0027]      FIG. 14  shows a flowchart for processing the addition of the request for MAC conversion to the wireless transfer apparatus according to the first embodiment of the present invention; 
           [0028]      FIG. 15  is the block diagram of the network according to the second embodiment of the present invention; 
           [0029]      FIG. 16  shows the state of each layer of the IP multicast transmission start request and the IP multicast transmission stop request transmitted and received by various apparatuses shown in  FIG. 15  according to the second embodiment of the present invention; 
           [0030]      FIG. 17  shows the state of each layer of the IP multicast transmitted and received by various apparatuses shown in  FIG. 15  according to the second embodiment of the present invention; 
           [0031]      FIG. 18  is a sequence diagram for processing the IP multicast transmission start requests and the IP multicast transmission stop requests by the receiver terminals requiring the individual control of the IP multicast according to the second embodiment of the present invention; 
           [0032]      FIG. 19  is a sequence diagram for processing the IP multicast transmission start requests and the IP multicast transmission stop requests by the receiver terminals not requiring the individual control of the IP multicast according to the second embodiment of the present invention; 
           [0033]      FIG. 20  is a block diagram of the network according to the third embodiment of the present invention; 
           [0034]      FIG. 21  shows the state of each layer of the. IP multicast transmission start requests and the IP multicast transmission stop requests transmitted and received by various apparatuses shown in  FIG. 20  according to the third embodiment of the present invention; 
           [0035]      FIG. 22  shows the state in each layer of the IP multicasts transmitted and received by various apparatuses shown in  FIG. 20  according to the third embodiment of the present invention. 
           [0036]      FIG. 23  is the block diagram of the ONU according to the third embodiment of the present invention; 
           [0037]      FIG. 24  is the block diagram of an ONU obtained by adding the function of a wireless transfer apparatus to the ONU according to the third embodiment of the present invention; 
           [0038]      FIG. 25  is the block diagram of the network apparatus according to the fourth embodiment of the present invention; 
           [0039]      FIG. 26  shows a conversion execution condition table according to the fourth embodiment of the present invention; 
           [0040]      FIG. 27  shows another conversion execution condition table according to the fourth embodiment of the present invention; 
           [0041]      FIG. 28  shows a routing information table according to the fifth embodiment of the present invention; 
           [0042]      FIG. 29  shows a MAC conversion information table according to the fifth embodiment of the present invention; and 
           [0043]      FIG. 30  shows a routing information table obtained by adding a MAC conversion information table to the routing information table according to the fifth embodiment of the present invention. 
       
    
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS 
       [0044]    We will describe the embodiments of the present invention with reference to drawings. 
       First Embodiment 
       [0045]    To begin with, we will describe the configuration of the network according to the first embodiment of the present invention. 
         [0046]      FIG. 1  is a block diagram of the network according to the first embodiment of the present invention. 
         [0047]    The network includes a transmitter  101 , a network apparatus  102 , a wireless transfer apparatus  103 , a wireless terminal  104 , a wired transfer apparatus  105  and a wired terminal  106 . 
         [0048]    The transmitter  101  transmits IP multicast to the network apparatus  102 . 
         [0049]    The network apparatus  102  receives a request to start an IP multicast transmission and a request to stop the multicast transmission with a request for MAC conversion from the wireless transfer apparatus  103 . The term “request for MAC conversion” means a request for setting the source unicast MAC addresses for the IP multicast transmission start request and the IP multicast transmission stop request as the destination MAC addresses of IP multicasts by the network apparatus  102 . The expression “with request for MAC conversion” means that a request for MAC conversion is included in the request to be transferred. And the network apparatus  102  receives a request to start an IP multicast transmission and a request to stop the IP multicast transmission without a request for MAC conversion from the wired transfer apparatus  105 . The expression “without request for MAC conversion” means that no request for MAC conversion is included in the request to be transferred. And the network apparatus  102  converts the destination MAC addresses of the IP multicast into the MAC addresses of the destination wireless terminals  104  and transmits the IP multicast whose destination MAC addresses have been converted to the wireless transfer apparatus  103 . And the network apparatus  102  transmits the IP multicast received from the transmitter  101  to the wired transfer apparatus  105  without converting the destination MAC address of the IP multicast. 
         [0050]    The wireless transfer apparatus  103  transmits the request to start the IP multicast transmission and the request to stop the IP multicast transmission received from the wireless terminal  104  to the network apparatus  102  with a request for MAC conversion. And the wireless transfer apparatus  103  transmits the IP multicast received from the network apparatus  102  to the wireless terminal  104 . 
         [0051]    The wireless terminal  104  transmits the request to start the IP multicast transmission and the request to stop the IP multicast transmission to the wireless transfer apparatus  103 . And the wireless terminal  104  receives IP multicast from the wireless transfer apparatus  103 . 
         [0052]    The wired transfer apparatus  105  transmits the request to start the IP multicast transmission and the request to stop the IP multicast transmission received from the wired terminal  106  to the network apparatus  102  without any request for MAC conversion. And the wired transfer apparatus  105  transmits the IP multicast received from the network apparatus  102  to the wired terminal  106 . 
         [0053]    The wired terminal  106  transmits the request to start the IP multicast transmission and the request to stop the IP multicast transmission to the wired relay terminal  105 . And the wired terminal  106  receives IP multicasts from the wired transfer apparatus  105 . 
         [0054]      FIG. 2  shows the state of each layer of the request to start IP multicast transmission and the request to stop IP multicast transmission transmitted and received by various apparatuses of the first embodiment of the present invention. 
         [0055]    The state of the physical layer includes the wired and wireless state. The state of the MAC layer includes multicast and unicast. And the state of the IP layer includes multicast. 
         [0056]    In the request to start the IP multicast transmission and the request to stop the IP multicast transmission, the destination addresses of the MAC layer and the IP layer is normally in the multicast state. The conversion of the destination addresses of the MAC layer into the unicast state and their differentiation from the normal request lead to show whether the request to start the IP multicast transmission and the request to stop the IP multicast transmission include any request for MAC conversion. 
         [0057]    Upon receipt of a request to start the IP multicast transmission and a request to stop the IP multicast transmission from the wireless terminal  104 , the wireless transfer apparatus  103  converts the destination addresses of the MAC layer of the request to start the IP multicast transmission and the request to stop the IP multicast transmission into the unicast MAC addresses of the network apparatus  102 , and transmits the same to the network apparatus  102 . 
         [0058]    And upon receipt of a request to start the IP multicast transmission and a request to stop the IP multicast transmission from the wired terminal  106 , the wired transfer apparatus  105  transmits the destination addresses of the MAC layer to the network apparatus  102  keeping the multicast MAC addresses without any conversion. 
         [0059]    The network apparatus  102  determines whether the destination addresses of the MAC layer of the request to start the IP multicast transmission and the request to stop the IP multicast transmission are unicast addresses or multicast addresses. As shown in  FIG. 3 , if the destination addresses of the MAC layer of the IP multicast transmission start request and the IP multicast transmission stop request are unicast addresses, the network apparatus  102  converts the MAC layer of the IP multicast received into the unicast, and if they are multicast addresses, it relays the MAC layer of the IP multicast received keeping the multicast state without conversion. 
         [0060]      FIG. 3  shows the state of each layer of the IP multicast transmitted and received by various apparatuses of the first embodiment of the present invention. 
         [0061]    The state of the physical layer includes the wired and wireless state. The state of the MAC layer includes multicast and unicast. And the state of the IP layer includes multicast. 
         [0062]    The transmitter  101  transmits the IP multicast of the physical layer (wired), the MAC layer (multicast) and the IP layer (multicast) to the network apparatus  102 . 
         [0063]    The network apparatus  102  converts the MAC layer of the IP multicast received from the transmitter  101  into the MAC addresses of the wireless terminals  104 , and transmits the IP multicast of the physical layer (wired), the MAC layer (unicast) and the IP layer (multicast) to the wireless transfer apparatus  103 . And the network apparatus  102 , without converting the MAC layer of the IP multicast received from the transmitter  101 , transmits the IP multicast of the physical layer (wired), the MAC layer (multicast) and the IP layer (multicast) to the wired transfer apparatus  105 . 
         [0064]    The wireless transfer apparatus  103  receives the IP multicast of the MAC layer (unicast) from the network apparatus  102 , converts the physical layer and the MAC layer into wireless and transmits the IP multicast of the physical layer (wireless), the MAC layer (wireless, unicast) and the IP layer (multicast) to the wireless terminals  104 . 
         [0065]    The wireless terminal  104  receives the IP multicast of the physical layer (wireless), the MAC layer (wireless, unicast) and the IP layer (multicast) from the wireless transfer apparatus  103 . 
         [0066]    The wired transfer apparatus  105  receives the IP multicast of the MAC layer (multicast) from the network apparatus  102 , and transmits the IP multicast of the physical layer (wired), the MAC layer (multicast) and the IP layer (multicast) to the wired apparatus  106 . 
         [0067]    The wired terminal  106  receives the IP multicast of the physical layer (wired), the MAC layer (multicast) and the IP layer (multicast) from the wired transfer apparatus  105 . 
         [0068]      FIG. 4  is an illustration of the constitution of the network apparatus according to the first embodiment of the present invention. 
         [0069]    The network apparatus  1101  includes a control unit  1102 , and interfaces  1103  ( 1103 A,  1103 B,  1103 C). Incidentally, the network apparatus  1101  corresponds to the network apparatus  102  shown in  FIG. 1 . 
         [0070]    The control unit  1102  includes a control memory  1104  and a control processor  1105 . The control memory  1104  includes a multicast transmission start/stop request processing program  1106 , a routing control processing program  1107 , a MAC conversion information table  1108  and a routing information table  1109 . 
         [0071]    The multicast transmission start/stop request processing program  1106  prepares the relay information of the IP multicast. Specifically, based on the IP multicast transmission start request or the IP multicast transmission stop request received from the wireless transfer apparatus  103  or the wired transfer apparatus  105 , it prepares or deletes the MAC conversion information table  1108  and the routing information table  1109 . 
         [0072]    In order to transfer the IP multicast received from the transmitter  101 , the routing control processing program  1107  controls the routing of the IP multicast based on the MAC conversion information table  1108  and the routing control table  1109 . 
         [0073]    The MAC conversion information table  1108  holds the information on the destination MAC addresses to which the IP multicasts are to be transmitted. 
         [0074]    The routing information table  1109  holds the information on the interface for transmitting and receiving the IP multicast. 
         [0075]    The control processor  1105  executes the program housed within the control memory  1104 . 
         [0076]    The interface  1103  is connected with the control unit  1102  and transmits or receives data to or from outside. Incidentally,  FIG. 3  shows three interfaces. However, any number other than three may be used. 
         [0077]      FIG. 5  shows a routing information table according to the first embodiment of the present invention. 
         [0078]    The routing information table  1109  includes IP multicast group addresses  2101 , an input interface  2102  and an output interface  2103 . 
         [0079]    The IP multicast group addresses  2101  are the destination addresses of the IP layer used at the time of distributing IP multicasts. The input interface  2102  is an interface through which the network apparatus  102  receives IP multicast. The output interface  2103  is an interface through which the network apparatus  102  transmits IP multicasts. 
         [0080]      FIG. 6  shows a MAC conversion information table according to the first embodiment of the present invention. 
         [0081]    The MAC conversion information table  1108  includes IP multicast group addresses  2201 , an output interface  2202 , and destination MAC addresses  2203 . 
         [0082]    The IP multicast group addresses  2201  are the destination addresses of the IP layer to be used at the time of distribution of IP multicasts. The output interface  2202  is an interface through which the network apparatus  102 transmits IP multicasts. The destination MAC addresses  2203  are MAC addresses to be set as the destination MAC addresses of the IP multicasts to be transmitted by the network apparatus  102 . 
         [0083]    For example, the column  2211  represents information to be set when it is not necessary to convert the destination MAC addresses of the IP multicast into unicast. In this case, the MAC address 01:00:5e:7f:01:01 corresponding to the IP multicast group address 239.255.1.1 is set as the destination MAC address  2203 . The MAC address corresponding to this IP multicast group address agrees with the MAC address set as the destination MAC address of the IP multicast whose destination MAC address has not been converted. And the columns  2212 - 2215  represent information to be set when the destination MAC address of the IP multicast needs to be converted into unicast. In this case, the MAC address of the receiver terminal having requested the transmission of the IP multicast is set as the destination MAC address  2203 . 
         [0084]    Incidentally, the network apparatus  102  according to the first embodiment of the present invention houses separately the routing information table  1109  and the MAC conversion information table  1108 . However, as shown in  FIG. 7 , the information of the MAC conversion table  1108  may be added to the routing information table  1109 . 
         [0085]      FIG. 7  shows an example of a routing information table wherein a MAC conversion information table is added to the routing information table according to the first embodiment of the present invention. 
         [0086]    The routing information table shown in  FIG. 7  includes the IP multicast group address  2301 , the input interface  2302 , the output interface  2303  and the destination MAC address  2304 . 
         [0087]    We omit the description of the details of various items shown in  FIG. 7  because they are similar to those shown in  FIG. 5  and  FIG. 6 . Incidentally, the IP multicast group address  2301  corresponds with the IP multicast group address  2101 , the input interface  2302  corresponds with the input interface  2102 , the output interface  2303  corresponds with the output interface  2103 , and the destination MAC address  2304  corresponds with the destination MAC address  2203 . 
         [0088]    Thus, it is possible to realize the present invention if the network apparatus  102  includes only a routing information table to which a MAC conversion information table is added. 
         [0089]      FIG. 8  is an illustration of structure of the wireless transfer apparatus according to the first embodiment of the present invention. 
         [0090]    The wireless transfer apparatus  1201  includes a control unit  1202 , a wireless processing unit  1203  and an interface  1204 . Incidentally, the wireless transfer apparatus.  1201  corresponds with the wireless transfer apparatus  103  shown in  FIG. 1 . 
         [0091]    The control unit  1202  includes a control memory  1205  and a control processor  1206 . 
         [0092]    The control memory  1205  includes a MAC conversion request additional processing program  1207 , a multicast transmission start/stop request processing program  1208  and a wire/wireless MAC processing program  1209 . 
         [0093]    The MAC conversion request additional processing program  1207  adds the MAC conversion request to the IP multicast transmission start request or the IP multicast transmission stop request received from the wireless terminal  104 . 
         [0094]    The multicast transmission start/stop request processing program  1208  transfers the IP multicast transmission start request or the IP multicast transmission stop request received from the wireless terminal  104  to the network apparatus  102 . 
         [0095]    The wired/wireless MAC processing program  1209  switches the state of data transmitted or received in the physical layer from wired to wireless or from wireless to wired. 
         [0096]    The control processor  1206  is a processor for executing the program held in the control memory  1205 . 
         [0097]    The wireless processing unit  1203  includes a wireless processing processor  1210  and a wireless unit  1211 . 
         [0098]    The wireless processing processor  1210  is a processor for mutually converting data signals and wireless signals and for controlling the retransmission of wireless communication. The wireless unit  1211  transmits and receives wireless signals. 
         [0099]    The interface  1204  is connected with the control unit  1202  and transmits and receives data to and from the outside. Incidentally,  FIG. 8  shows only an interface. However, a plurality of interfaces may be provided. 
         [0100]    Incidentally, the network structure according to the first embodiment of the present invention includes separately a network apparatus  102  and a wireless transfer apparatus  103 . However, as shown in  FIG. 9 , the function of a wireless transfer apparatus  103  may be added to the network apparatus  102 . 
         [0101]      FIG. 9  is an illustration of configuration of the network apparatus obtained by adding the function of a wireless transfer apparatus to the network apparatus according to the first embodiment of the present invention. 
         [0102]    The network apparatus  1301  shown in  FIG. 9  is a variation of the network apparatus  102  according to the first embodiment obtained by combining the same with the function of a wireless transfer apparatus  103 . Incidentally, it is possible to construct a network by using a network apparatus  1301  in the place of the network apparatus  102  and the wireless transfer apparatus  103  shown in  FIG. 1 . 
         [0103]    The network apparatus  1301  shown in  FIG. 9  includes a control unit  1302 , a wireless processing unit  1303 , and interfaces  1304  ( 1304 A,  1304 B). 
         [0104]    The control unit  1302  includes a control memory  1305  and a control processor  1306 . The control memory  1305  houses a multicast transmission start/stop request processing program  1307 , a routing control processing program  1308 , a wired/wireless MAC processing program  1309 , a MAC conversion information table  1310 , and a routing information table  1311 . 
         [0105]    The wireless processing unit  1303  includes a wireless processing processor  1312  and a wireless unit  1313 . 
         [0106]    We omit the detailed description of each item because they are identical with those shown in  FIG. 4  and  FIG. 8 . Incidentally, the multicast transmission start/stop request processing program  1307  corresponds to the multicast transmission start/stop request processing program  1106 , the routing control processing program  1308  corresponds to the routing control processing program  1107 , the wired/wireless MAC processing program  1309  corresponds to the wired/wireless MAC processing program  1209 , and the control processor  1306  corresponds to the control processor  1105 . Moreover, the MAC conversion information table  1310  corresponds to the MAC conversion information table  1108 , and the routing information table  1311  corresponds to the routing information table  1109 . And the wireless processing processor  1312  corresponds to the wireless processing processor  1210 , the wireless unit  1313  corresponds to the wireless unit  1211 , and the interface  1304  corresponds to the interface  1103 . 
         [0107]    And since the network apparatus  1301  shown in  FIG. 9  requires no addition of requests for MAC conversion, the MAC conversion request addition processing program  1207  shown in  FIG. 8  becomes unnecessary. 
         [0108]    Thus, by adding the function of a wireless transfer apparatus to the network apparatus, it will be possible to realize the functions of a network apparatus and the wireless transfer apparatus in a single apparatus. 
         [0109]      FIG. 10  is a sequence diagram for processing the IP multicast transmission start request and the IP multicast transmission stop request received from the wireless terminal indicating the necessity of converting the MAC addresses in the MAC layer according to the first embodiment of the present invention. 
         [0110]    To begin with, the wireless terminal  104  transmits an IP multicast transmission start request to the wireless transfer apparatus  103 . Upon receipt of an IP multicast transmission start request from the wireless terminal  104 , the wireless transfer apparatus  103  transmits an IP multicast transmission start request with a request for MAC conversion to the network apparatus  102 . 
         [0111]    Then, upon receipt of an IP multicast transmission request from the wireless terminal  103 , the network apparatus  102  prepares IP multicast relay information including MAC conversion information. 
         [0112]    Then, the network apparatus  102  converts the destination MAC addresses of the IP multicast received from the transmitter  101  to the unicast MAC addresses of the wireless terminal  104  based on the IP multicast relay information prepared and transmits the converted IP multicast to the wireless transfer apparatus  103 . The wireless transfer apparatus  103  transmits the IP multicast received from the network apparatus  102  to the wireless terminal  104 . 
         [0113]    Then, the wireless terminal  104  transmits the IP multicast transmission stop request to the wireless transfer apparatus  103 . Upon receipt of the IP multicast transmission stop request from the wireless terminal  104 , the wireless transfer apparatus  103  transmits the IP multicast transmission stop request with a request for MAC conversion to the network apparatus  102 . 
         [0114]    Then, upon receipt of the IP multicast transmission stop request with a request for MAC conversion from the wireless transfer apparatus  103 , the network apparatus  102  deletes the IP multicast relay information including the MAC conversion information prepared. 
         [0115]      FIG. 11  is a sequence diagram for processing the request to start the IP multicast transmission and the request to stop the IP multicast transmission from the wired terminal not requiring the conversion of the MAC layer according to the first embodiment of the present invention. 
         [0116]    To begin with, the wired terminal  106  transmits an IP multicast transmission start request to the wired transfer apparatus  105 . Upon receipt of the IP multicast transmission start request from the wired terminal  106 , the wired transfer apparatus  105  transmits an IP multicast transmission start request without any request for MAC conversion to the network apparatus  102 . 
         [0117]    Then, upon receipt of an IP multicast transmission start request without any request for MAC conversion from the wired transfer apparatus  105 , the network apparatus  102  prepares IP multicast relay information without any information on MAC conversion. 
         [0118]    Then, the network apparatus  102  transmits the IP multicast received from the transmitter  101  to the wired transfer apparatus  105  based on the IP multicast relay information prepared. The wired transfer apparatus  105  transmits the IP multicast received from the network apparatus  102  to the relay terminal  106 . 
         [0119]    Then, the wired terminal  106  transmits an IP multicast transmission stop request to the wired transfer apparatus  105 . Upon receipt of the IP multicast transmission stop request from the wired terminal  106 , the wired transfer apparatus  105  transmits the IP multicast transmission stop request without any request for MAC conversion to the network apparatus  102 . 
         [0120]    Then, upon receipt of the IP multicast transmission stop request without any request for MAC conversion from the wired transfer apparatus  105 , the network apparatus  102  transmits the confirmation of stopping the IP multicast to the wired transfer apparatus  105 . The wired transfer apparatus  105  transmits the confirmation of stopping the IP multicast received from the network apparatus  102  to the wired terminal  106 . 
         [0121]    Then, in the absence of response to the confirmation of stopping the IP multicast transmission during a predetermined period of time from the wired terminal  106 , the network apparatus  102  deletes the. IP multicast relay information prepared without any request for MAC conversion. 
         [0122]      FIG. 12  shows a flowchart of routing control processing of the network apparatus according to the first embodiment of the present invention. 
         [0123]    To begin with, the network apparatus  102  receives an IP multicast from the transmitter  101  ( 3102 ). 
         [0124]    Then, the network apparatus  102  refers the routing information table  1109  to determine whether the relay information of the IP multicast received exists or not ( 3103 ). If it is determined in the step  3103  that the output interface  2103  corresponding to the IP multicast group addresses  2101  of the IP multicast exists in the routing information table  1109 , the process advances to the step  3104 . On the other hand, it is not found in the routing information table  1109 , the IP multicast received is disposed and the processing is terminated. 
         [0125]    In the step  3104 , the network apparatus  102  refers the routing information table  1109  and acquires the interface indicated by the output interface  2103  corresponding to the IP multicast group addresses  2101  of the IP multicast ( 3104 ). 
         [0126]    Then, the network apparatus  102  refers the MAC conversion information table  1108  and acquires the MAC addresses indicated by the destination MAC addresses  2203  corresponding to the IP multicast group addresses  2201  of the IP multicast ( 3105 ). 
         [0127]    Then, the network apparatus  102  reproduces as many IP multicasts as necessary to relay ( 3106 ). Specifically, the network apparatus  102  reproduces as many IP multicasts as there are the destination MAC addresses  2203  corresponding to the IP multicast group addresses  2201 . 
         [0128]    Then, the network apparatus  102  converts the destination MAC addresses of the IP multicast ( 3107 ). Specifically, the network apparatus  102  sets the destination MAC addresses acquired in the step  3105  as the destination MAC addresses of each IP multicast that had been reproduced in the step  3106 . Incidentally, if the destination MAC addresses of the IP multicast agree with the destination MAC addresses acquired in the step  3105 , it is not necessary to convert the destination MAC addresses of the IP multicast. 
         [0129]    Then, the network apparatus  102  transmits IP multicast from the output interface ( 3108 ). Specifically, the network apparatus  102  transmits IP multicast from the output interface acquired in the step  3104 . And the network apparatus  102  stops processing ( 3109 ). 
         [0130]      FIG. 13  shows a flowchart for processing the multicast transmission start/stop request of the network apparatus according to the first embodiment of the present invention. 
         [0131]    To begin with, the network apparatus  102  receives data from the transfer apparatus (wireless transfer apparatus  103  or wired transfer apparatus  105 ) ( 3202 ). 
         [0132]    Then, the network apparatus  102  determines whether the data received contain an IP multicast transmission start request or not ( 3203 ). If it is determined in the step  3203  that the data received contain an IP multicast transmission start request, the process advances to the step  3204 . On the other hand, if the data received is not an IP multicast transmission start request, the process advances to the step  3207 . 
         [0133]    In the step  3204 , the network apparatus  102  determines whether the data received is an IP multicast transmission start request ( 3204 ). If it is determined in the step  3204  that the data received is an IP multicast transmission start request, the process advances to the step  3205 . On the other hand, if the data received contained no MAC conversion request, the process advances to the step  3206 . 
         [0134]    In the step  3205 , the network apparatus  102  prepares IP multicast relay information based on the unicast MAC information to be converted ( 3205 ). Specifically, the network apparatus  102  prepares a routing information table  1109  shown in  FIG. 5  based on the IP multicast transmission start request received, and prepares a MAC conversion information table  1108  shown in  FIG. 6  based on the source unicast MAC addresses information requesting to start the IP multicast transmission received. And then it terminates processing. 
         [0135]    In the step  3206 , the network apparatus  102  prepares IP multicast relay information based on the multicast MAC information corresponding to the IP multicast ( 3206 ). Specifically, the network apparatus  102  prepares the routing information table  1109  shown in  FIG. 5  based on the IP multicast transmission start request received, and prepares the MAC conversion information table  1108  shown in  FIG. 6  based on the multicast MAC addresses information corresponding to the IP multicast. Then, it terminates processing. 
         [0136]    In the step  3207 , the network apparatus  102  determines whether the data received is an IP multicast transmission stop request or not. If it is determined in the step  3207  that the data received is an IP multicast transmission stop request, the process advances to the step  3208 . On the other hand, if the data received is not an IP multicast transmission stop request, in the step  3211  normal data processing is executed and the processing is terminated. 
         [0137]    In the step  3208 , the network apparatus  102  determines whether a MAC conversion request is added to the data received or not ( 3208 ). If it is determined in the step  3208  that a MAC conversion request has been added to the data received, the process advances to the step  3209 . On the other hand, if no MAC conversion request is added to the data received, the process advances to the step  3210 . 
         [0138]    In the step  3209 , the network apparatus  102  deletes the IP multicast relay information of the unicast MAC to be converted ( 3209 ) and terminates the processing. 
         [0139]    In the step  3210 , the network apparatus  102  confirms whether any receiver terminal has received a request for stopping transmission for which there is no need of MAC conversion of IP multicast ( 3210 ) and terminates the processing. 
         [0140]      FIG. 14  shows the flowchart of processing the addition of a MAC conversion request to the wireless transfer apparatus according to the first embodiment of the present invention. 
         [0141]    To begin with, the wireless transfer apparatus  103  receives data from the wireless terminal  104  ( 3302 ). 
         [0142]    Then, the wireless transfer apparatus  103  determines whether the data received is an IP multicast transmission start request or not ( 3303 ). If it is determined in the step  3303  that the data received is not an IP multicast transmission start request, the process advances to the step  3304 . On the other hand, if the data received is an IPmulticast transmission start request, the process advances to the step  3305 . 
         [0143]    In the step  3304 , the wireless transfer apparatus  103  determines whether the data received is an IP multicast transmission stop request or not ( 3304 ). If it is determined in the step  3304  that the data received is an IP multicast transmission stop request, the process advances to the step  3305 . On the other hand, if the data received is not an IP multicast transmission start request, the process advances to the step  3306 , and the wireless transfer apparatus  103  executes the normal data processing and terminates the processing. 
         [0144]    In the step  3305 , the wireless transfer apparatus  103  adds the MAC conversion request and transmits to the network apparatus  102  ( 3305 ). Specifically, the wireless transfer apparatus  103  adds a MAC conversion request to an IP multicast transmission start request or an IP multicast transmission stop request and transmits an IP multicast transmission start request or an IP multicast transmission stop request coupled with a MAC conversion request to the network apparatus  102 . And the wireless transfer apparatus  103  stops the processing. 
       Second Embodiment 
       [0145]    The second embodiment of the present invention is an example wherein the wired terminals requiring the transmission of the IP multicast must be controlled individually. The case where wired terminals must be controlled individually means the case wherein the quality of transmission of IP multicast to separate wired terminals must be controlled. 
         [0146]      FIG. 15  is a diagram of configuration of the network according to the second embodiment of the present invention. 
         [0147]    The network includes a transmitter  101 , a network apparatus  102 , a transfer apparatus  107 , a receiver terminal (with separate control)  108 , a transfer apparatus  109  and a receiver (without separate control)  110 . 
         [0148]    The difference with the first embodiment lies in the fact that the receiver terminals  108  and  110  connected with the transfer apparatus are both connected with wires and that the necessity of individual control of the transfer apparatuses cannot be judged from the viewpoint of their connecting method. 
         [0149]    The transmitter  101  transmits IP multicasts to the network apparatus  102 . 
         [0150]    The network apparatus  102  receives IP multicast transmission start requests and IP multicast transmission stop requests with a MAC conversion request from the transfer apparatus  107 . And the network apparatus  102  receives IP multicast transmission start requests and IP multicast transmission stop requests without any MAC conversion request from the transfer apparatus  109 . And the network apparatus  102  converts the destination MAC addresses of the IP multicast received from the transmitter  101  into the MAC addresses in the destination receiver terminals (with individual control)  108  and transmits the IP multicasts whose destination MAC addresses have been converted into the transfer apparatus  107 . And the network apparatus  102  transmits the IP multicasts received from the transmitter  101  to the transfer apparatus  109  without converting the destination MAC addresses of the IP multicasts. 
         [0151]    The transfer apparatus  107  transmits the IP multicast transmission start requests and the IP multicast transmission stop requests with a MAC conversion request received from the receiver terminal (with individual control)  108  to the network apparatus  102 . And the transfer apparatus  107  transmits the IP multicasts received from the network apparatus  102  to the receiver terminal (with individual control)  108 . 
         [0152]    The receiver terminal (with individual control)  108  transmits the IP multicast transmission start requests and the IP multicast transmission stop requests requiring the individual control of the IP multicast and coupled with a MAC conversion request to the transfer apparatus  107 . And the receiver terminal (with individual control)  108  receives IP multicasts from the transfer apparatus  107 . 
         [0153]    The transfer apparatus  109  transmits the IP multicast transmission start requests and the IP multicast transmission stop requests without MAC conversion request and received from the receiver terminal (without any individual control)  110  to the network apparatus  102 . And the transfer apparatus  109  transmits the IP multicasts received from the network apparatus  102  to the receiver terminal (without individual control)  110 . 
         [0154]    The receiver terminal (without individual control)  110  transmits the IP multicast transmission start requests and the IP multicast transmission stop requests not requiring the individual control of the IP multicasts and without any MAC conversion request to the transfer apparatus  109 . And the receiver terminal (without individual control)  110  receives IP multicasts from the transfer apparatus  109 . 
         [0155]      FIG. 16  shows the state of each layer of the IP multicast transmission start requests and the IP multicast transmission stop requests transmitted and received by each apparatus according to the second embodiment of the present invention. 
         [0156]    The state of the physical layer includes the wired state. The state of the MAC layer includes the multicast and unicast state. And the state of the IP layer includes the multicast layer. 
         [0157]    The receiver terminal (with individual control)  108  sets the unicast MAC addresses of the network apparatus  102  as the destination addresses of the MAC layer of the IP multicast transmission start requests and the IP multicast transmission stop requests and transmits them to the network apparatus  102 . 
         [0158]    The receiver terminal (without individual control)  110  sets the multicast MAC addresses as the destination addresses of the MAC layer of the IP multicast transmission start requests and the IP multicast transmission stop requests and transmits them to the network apparatus  102 . 
         [0159]    The network apparatus  102  determines whether the destination addresses of the MAC layer of the IP multicast transmission start requests and the IP multicast transmission stop requests are unicast addresses or multicast addresses. If the destination addresses of the MAC layer of the IP multicast transmission start requests and the IP multicast transmission stop requests are unicast addresses, it converts the MAC layer of the IP multicast received into unicast, and if they are multicast addresses, it relays leaving the MAC layer of the IP multicast received in the multicast state without converting the same. 
         [0160]      FIG. 17  shows the state in each layer of the IP multicast transmitted and received by each apparatus shown in  FIG. 15  according to the second embodiment of the present invention. 
         [0161]    The transmitter  101  transmits the IP multicasts from the physical layer (wired), the MAC layer (multicast) and the IP layer (multicast) to the network apparatus  102 . 
         [0162]    The network apparatus  102  converts the MAC layer of the IP multicast received from the transmitter  101  into the MAC addresses of the receiver terminal (with individual control)  108 , and transmits the IP multicasts of the physical layer (wired), the MAC layer (unicast) and the IP layer (multicast) to the transfer apparatus  107 . And the network apparatus  102  transmits the IP multicasts of the physical layer (wired), the MAC layer (multicast) and the IP layer (multicast) to the transfer apparatus  109  without converting the MAC layer of the IP multicast received from the transmitter  101 . 
         [0163]    The transfer apparatus  107  receives the IP multicast of the MAC layer (unicast) from the network apparatus  102 , and transmits the IP multicast of the physical layer (wired), the MAC layer (unicast) and the IP layer (multicast) to the receiver terminal (with individual control)  108 . 
         [0164]    The receiver terminal (with individual control)  108  receives the IP multicast of the physical layer (wired), the MAC layer (unicast) and the IP layer (multicast) from the transfer apparatus  107 . 
         [0165]    The transfer apparatus  109  receives the IP multicast of the MAC layer (multicast) from the network apparatus  102  and transmits the IP multicast of the physical layer (wired), the MAC layer (multicast) and the IP layer (multicast) to the receiver terminal (without individual control)  110 . 
         [0166]    The receiver terminal (without individual control)  110  receives the IP multicast of the physical layer (wired), the MAC layer (multicast) and the IP layer (multicast) from the transfer apparatus  109 . 
         [0167]      FIG. 18  is a sequence diagram for processing the IP multicast transmission start request and the IP multicast transmission stop request from the receiver terminal requiring the individual control of IP multicasts according to the second embodiment of the present invention. 
         [0168]    To begin with, the receiver terminal (with individual control)  108  transmits an IP multicast transmission start requests coupled with a request for MAC conversion to the transfer apparatus  107 . Upon receipt of an IP multicast transmission start request coupled with a request for MAC conversion from the receiver terminal (with individual control)  108 , the transfer apparatus  107  transmits an IP multicast transmission start request coupled with a request for MAC conversion to the network apparatus  102 . 
         [0169]    Then, upon receipt of an IP multicast transmission start request coupled with a request for MAC conversion from the transfer apparatus  107 , the network apparatus  102  prepares IP multicast relay information including information on MAC conversion. 
         [0170]    Then, based on the IP multicast relay information prepared, the network apparatus  102  converts the destination MAC addresses of the IP multicast received from the transmitter  101  into the unicast MAC addresses of the receiver terminals (with individual control)  108 , and transmits the converted IP multicasts to the relay terminal  107 . The transfer apparatus  107  transmits the IP multicasts received from the network apparatus  102  to the receiver terminal (with individual control)  108 . 
         [0171]    Then, the receiver terminal (with individual control)  108  transmits an IP multicast transmission stop request coupled with a request for MAC conversion to the transfer apparatus  107 . Upon receipt of an IP multicast transmission stop request coupled with a request for MAC conversion from the receiver terminal (with individual control)  108 , the transfer apparatus  107  transmits an IP multicast transmission stop request coupled with a request for MAC conversion to the network apparatus  102 . 
         [0172]    Then, upon receipt of an IP multicast transmission stop request coupled with a request for MAC conversion from the transfer apparatus  107 , the network apparatus  102  deletes the IP multicast relay information prepared containing MAC conversion information. 
         [0173]      FIG. 19  is a sequence diagram for processing the IP multicast transmission start request and the IP multicast transmission stop request from the receiver terminal not requiring the individual control of IP multicasts according to the second embodiment of the present invention. 
         [0174]    To begin with, the receiver terminal (without individual control)  110  transmits an IP multicast transmission stop requests without any request for MAC conversion to the transfer apparatus  109 . Upon receipt of an IP multicast transmission start request without any request for MAC conversion from the receiver terminal (without individual control), the transfer apparatus  109  transmits an IP multicast transmission start request without any request for MAC conversion to the network apparatus  102 . 
         [0175]    Then, upon receipt of an IP multicast transmission start request without any request for MAC conversion from the transfer apparatus  109 , the network apparatus  102  prepares IP multicast relay information without MAC conversion information. 
         [0176]    Then, the network apparatus  102  transmits the IP multicasts received from the transmitter  101  based on the IP multicast relay information prepared to the transfer apparatus  109 . The transfer apparatus  109  transmits the IP multicasts received from the network apparatus  102  to the receiver terminal (without individual control)  110 . 
         [0177]    Then, the receiver terminal (without individual control)  110  transmits IP multicast transmission stop requests without any MAC conversion request to the transfer apparatus. 109 . Upon receipt of an IP multicast transmission stop request without any MAC conversion request from the receiver terminal (without individual control)  110 , the transfer apparatus  109  transmits an IP multicast transmission stop request without any MAC conversion request to the network apparatus  102 . 
         [0178]    Then, upon receipt of an IP multicast transmission stop request without any MAC conversion request from the transfer apparatus  109 , the network apparatus  102  transmits a confirmation of stopping the IP multicast to the transfer apparatus  109 . The transfer apparatus  109  transmits the confirmation of stopping the IP multicast it had received from the network apparatus  102  to the receiver terminal (without individual control)  110 . 
         [0179]    Then, in the absence of response to the confirmation of stopping IP multicast transmission during a predetermined period of time from the receiver terminal (without individual control)  110 , the network apparatus  102  deletes the IP multicast relay information without any request for MAC conversion. 
       Third Embodiment 
       [0180]    The third embodiment of the present invention is the case of a apparatus resulting from adding the function of a network apparatus of the first embodiment to the ONU of a PON (Passive Optical Network) system. 
         [0181]    The difference from the first embodiment lies in that the network includes a PON apparatus (OLT: Optics Line Terminal) and a PON apparatus (ONU: Optical Network Unit) in the place of network apparatuses, wireless transfer apparatuses, and wired transfer apparatuses. 
         [0182]      FIG. 20  is a block diagram of the network according to the third embodiment of the present invention. 
         [0183]    The network according to the third embodiment includes a transmitter  101 , an OLT  111 , an ONU  112 , ONU  113 , a optical splitter  114 , a receiver terminal (with individual control)  108 , and a receiver terminal (without individual control)  110 . The expression “with or without individual control” means, like the second embodiment described above, for example, whether it is necessary or not to control the quality of IP multicast transmission for specific wired terminals. 
         [0184]    The transmitter  101  transmits IP multicasts to the OLT  111 . 
         [0185]    The OLT  111  receives IP multicast transmission start requests and IP multicast transmission stop requests from the ONU  112 . And the OLT  111  receives IP multicast transmission start requests and IP multicast transmission stop requests from the ONU  113 . Furthermore, the OLT  111  transmits the IP multicast received from the transmitter  101  to the optical splitter  114 . The optical splitter  114  distributes the IP multicasts received from OLT  111  into a plurality of ONU  112  and  113 . 
         [0186]    The ONU  112  transmits the IP multicast transmission start requests and the IP multicast transmission stop requests received from the receiver terminal (with individual control)  108  to the OLT  111 . And the ONU  112  converts the destination MAC address of the IP multicasts received from the OLT  111  into the MAC addresses of the receiver terminal (with individual control)  108  and transmits the IP multicast whose destination MAC addresses have been converted to the receiver terminal (with individual control)  108 . 
         [0187]    The receiver terminal (with individual control)  108  transmits the IP multicast transmission start requests and the IP multicast transmission stop requests requiring the individual control of the IP multicast and coupled with a MAC conversion request to the ONU  112 . And the receiver terminal (with individual control)  108  receives IP multicasts from the ONU  112 . 
         [0188]    The ONU  113  transmits the IP multicast transmission start requests and the IP multicast transmission stop requests received from the receiver terminal (with individual control)  110  to the OLT  111 . And the ONU  113  transmits the IP multicast received from the OLT  111  to the receiver terminal (without individual control)  110  without converting the destination MAC addresses of the IP multicasts. 
         [0189]    The receiver terminal (without individual control)  110  transmits the IP multicast transmission start requests and the IP multicast transmission stop requests not requiring the individual control of the IP multicast and without any MAC conversion request to the ONU  113 . And the receiver terminal (without individual control)  110  receives IP multicasts from the ONU  113 . 
         [0190]      FIG. 21  shows the state of each layer of the IP multicast transmission start requests and the IP multicast transmission stop requests transmitted and received by various apparatuses according to the third embodiment of the present invention. 
         [0191]    The receiver terminal (with individual control)  108  sets the unicast MAC addresses of the ONU  112  as the destination addresses of the MAC layer of the IP multicast transmission start requests and the IP multicast transmission stop requests to transmit the same to the ONU  112 . 
         [0192]    The receiver terminal (without individual control)  110  sets the multicast MAC addresses as the destination addresses in the MAC layer of the IP multicast transmission start requests and the IP multicast transmission stop requests to transmit the same to the ONU  113 . 
         [0193]    The ONU  112  and the ONU  113  determine whether the destination addresses in the MAC layer of the IP multicast transmission start requests and the IP multicast transmission stop requests are unicast addresses or multicast addresses. If the destination addresses in the MAC layer of the IP multicast transmission start requests and the IP multicast transmission stop requests are unicast addresses, the MAC layer of the IP multicast transmission received is converted to the unicast, and if they are multicast addresses, the MAC layer of the IP multicast transmission received is left as it is without conversion and the data are relayed as they are. 
         [0194]      FIG. 22  shows the state in each layer of the IP multicast transmission transmitted and received by various apparatuses shown in  FIG. 20  according to the third embodiment of the present invention. 
         [0195]    The transmitter  101  transmits the IP multicast in the physical layer (wired), the MAC layer (multicast) and the IP layer (multicast) to the OLT  111 . 
         [0196]    The OLT  111  constitutes the MAC layer part of the IP multicast received from the transmitter  101  in the PON frame format, distributes the IP multicast by a optical splitter  114  in the physical layer (wired), the PON layer and the IP layer (multicast) and transmits the same to the ONU  112  and the ONU  113 . 
         [0197]    The ONU  112  reconstitutes the PON layer of the IP multicast received from the OLT  111  by using the unicast MAC addresses of the receiver terminal (with individual control)  108 , and transmits the IP multicasts in the physical layer (wired), the MAC layer (unicast) and the IP layer (multicast) to the receiver terminal (with individual control)  108 . 
         [0198]    The receiver terminal (with individual control)  108  receives the IP multicast in the physical layer (wired), the MAC layer (unicast) and the IP layer (multicast.) from the ONU  112 . 
         [0199]    The ONU  113  reconstitutes the PON layer of the IP multicast received from the OLT  111  by using the multicast MAC addresses corresponding to the IP multicast addresses and transmits the IP multicast in the physical layer (wired), the MAC layer (multicast) and the IP layer (multicast) to the receiver terminal (without individual control)  110 . 
         [0200]    The receiver terminal (without individual control)  110  receives the IP multicast in the physical layer (wired), the MAC layer (multicast) and the IP layer (multicast) from the ONU  113 . 
         [0201]      FIG. 23  is a block diagram of the ONU according to the third embodiment of the present invention. 
         [0202]    The ONU  1401  includes a control unit  1402 , interfaces  1403  ( 1403 A,  1403 B), an electric-optical conversion unit  1404 , and an optical transmitter-receiver  1405 . 
         [0203]    We omit the description of the control unit  1402  and the interface  1403 , because they are made in the same way as the network apparatus according to the first embodiment. Incidentally, the control memory  1406  corresponds to the control memory  1104 , the multicast transmission start/stop request processing program  1408  corresponds to the multicast transmission start/stop request processing program  1106 , the routing control processing program  1409  corresponds to the routing control processing program  1107 , the MAC conversion information table  1410  corresponds to the MAC conversion information table  1108 , and the routing information table  1411  corresponds to the routing information table  1109 . And the control processor  1407  corresponds to the control processor  1105 , and the interface  1403  corresponds to the interface  1103 . 
         [0204]    The electric-optical conversion unit  1404  converts the data signal to be transmitted and received from electricity to light or from light to electricity. 
         [0205]    The optical transmitter-receiver  1405  is an interface for transmitting and receiving data signals by light. 
         [0206]    And as shown in  FIG. 24 , the function of a wireless transfer apparatus according to the first embodiment may be added to the ONU  1401  shown in  FIG. 23 . 
         [0207]      FIG. 24  is a block diagram of an ONU wherein the function of a wireless transfer apparatus is added to the ONU according to the third embodiment of the present invention. 
         [0208]    The ONU  1501  shown in  FIG. 24  is a variation wherein the system of a wireless transfer apparatus  103  according to the first embodiment is added to the system of the ONU  1401  according to the third embodiment. Incidentally, it is possible to constitute a network by adopting the ONU  1501  in the place of the ONU  112  and ONU  113  shown in  FIG. 20 . In such a case, the ONU  1501  and the receiver terminal  108  are connected by a wireless circuit. 
         [0209]    The ONU  1501  includes a control unit  1502 , a wireless processing unit  1503 , interfaces  1504 , electric-optical conversion unit  1505 , and optical transmitter-receiver  1506 . 
         [0210]    The control unit  1502  includes a control memory  1507  and a control processor  1508 . The control memory  1507  includes a multicast transmission start/stop request processing program  1509 , a routing control processing program  1510 , a wired/wireless MAC processing program  1511 , a MAC conversion information table  1512 , and a routing information table  1513 . 
         [0211]    The wireless processing unit  1503  includes a wireless processing processor  1514  and a wireless unit  1515 . 
         [0212]    We omit the detailed description of various units because they are the same as described in  FIG. 8  and  FIG. 23 . Incidentally, the multicast transmission start/stop request processing program  1509  corresponds to the multicast transmission start/stop request processing program  1408 , the routing control processing program  1510  corresponds to the routing control processing program  1409 , and the wired/wireless MAC processing program  1511  corresponds to the wired/wireless MAC processing program  1209 . And the MAC conversion information table  1512  corresponds to the MAC conversion information table  1410 , and the routing information table  1513  corresponds to the routing information table  1411 . Furthermore, the control processor  1508  corresponds to the control processor  1407 , and the interface  1504  corresponds to the interface  1403 , the electric-optical conversion unit  1505  corresponds to the electric-optical conversion unit  1404 , and the optical transmitter-receiver  1506  corresponds to the optical transmitter-receiver  1405 . 
         [0213]    Thus, it is possible to provide an ONU having a PON system with the function of a network apparatus and a wireless transfer apparatus. 
       Fourth Embodiment 
       [0214]    The fourth embodiment of the present invention is the case of distinguishing whether the MAC layer should be converted from the multicast to the unicast or not in a way different from the first embodiment while the network apparatus is relaying an IP multicast transmission. 
         [0215]      FIG. 25  is a block diagram of the network apparatus according to the fourth embodiment of the present invention. 
         [0216]    The difference from the first embodiment lies in that the control memory  1104  includes a conversion execution condition table  1110 . 
         [0217]    The conversion execution condition table  1110  contains the conditions required to determine whether the IP multicast transmission start request and the IP multicast transmission stop request that the network apparatus  102  had received require the conversion of unicast in the MAC layer or not. 
         [0218]      FIG. 26  is a conversion execution condition table according to the fourth embodiment of the present invention. 
         [0219]    The conversion execution condition table  1110  shown in  FIG. 26  represents the case wherein the source IP addresses for the IP multicast transmission start request and the IP multicast transmission stop request are used as the condition for determining whether the conversion of unicast in the MAC layer is required or not. 
         [0220]    The conversion execution condition table  1110  shown in  FIG. 26  includes the source IP addresses  2401  for the multicast transmission start requests and the IP multicast transmission stop requests. 
         [0221]    The conversion execution condition table  1110  is a register of unicast IP addresses. And when the source IP addresses for the IP multicast transmission start requests and the IP multicast transmission stop requests agree with the registered unicast IP addresses, at the time when the IP multicasts are to be relayed, the condition is set so that the MAC layer may be converted or not converted into the unicast. 
         [0222]    Incidentally, the conversion execution condition table  1110  is referred when the IP multicast transmission start request or the IP multicast transmission stop request has been received. Specifically, when a determination is made whether a MAC conversion request is added to the IP multicast transmission start request or the IP multicast transmission stop request received in the step  3204  or the step  3208  shown in  FIG. 13 , the conversion execution condition table  1110  is referred. When a determination is made that the MAC layer is to be converted into the unicast, the process advances respectively to the step  3205  or the step  3209 . On the other hand, when a determination is made that the MAC layer will not be converted into the unicast, the process advances respectively to the step  3206  or the step  3210 . 
         [0223]      FIG. 27  is another conversion execution condition table according to the fourth embodiment of the present invention. 
         [0224]    The conversion execution condition table  1110  shown in  FIG. 27  represents the case wherein the source MAC addresses for the IP multicast transmission start request or the IP multicast transmission stop request are used as the condition for determining whether the conversion of unicast in the MAC layer is necessary or not. 
         [0225]    The conversion execution condition table  1110  shown in  FIG. 27  includes the source IP addresses  2501  for the multicast transmission start requests and the IP multicast transmission stop requests. 
         [0226]    The conversion execution condition table accepts the registration of unicast MAC addresses. And when the source IP addresses for the IP multicast transmission start requests and the IP multicast transmission stop requests agree with the registered unicast IP addresses, at the time of relaying the IP multicast, the condition is set in such a way that the MAC layer may be converted or not converted into the unicast. 
         [0227]    Incidentally, like the conversion execution condition table  1110  shown in  FIG. 26 , when an IP multicast transmission start request or an IP multicast transmission stop request has been received, the conversion execution condition table  1110  shown in Table  27  is referred. 
       Fifth Embodiment 
       [0228]    The fifth embodiment of the present invention represents the case wherein the source IP address information of the transmitter is added to the routing information table and the MAC conversion information table when the network apparatus controls the distribution of the IP multicast by using the IP multicast group addresses and the IP addresses of the transmitter. 
         [0229]      FIG. 28  shows the routing information table according to the first embodiment of the present information. 
         [0230]    The routing information table shown in  FIG. 28  includes IP multicast group addresses  2101 , source IP addresses  2104 , input interface  2101 , and output interface  2103 . 
         [0231]    The difference with the first embodiment lies in that the routing information table includes the source IP addresses. 
         [0232]    The source IP addresses  2104  are the IP addresses of the transmitter for distributing IP multicasts. 
         [0233]      FIG. 29  is the MAC conversion information table according to the first embodiment of the present invention. 
         [0234]    The MAC conversion information table shown in  FIG. 29  includes IPmulticast group addresses  2201 , source IP addresses  2204 , output interface  2202 , and destination MAC addresses  2203 . 
         [0235]    The difference with the first embodiment lies in that the MAC conversion information table includes source IP addresses  2204 . 
         [0236]    For example, the column  2221  represents the information set when it is not necessary to convert the destination MAC addresses of IP multicast into unicast. In this case, the MAC address 01:00:5e:7f:01:01 corresponding to the IP multicast group address 239.255.1.1 is set as the destination MAC address  2203 . And the column  2222 - 2225  is the information set when it is necessary to convert the destination MAC addresses of IP multicast into unicast. In this case, the MAC addresses of the receiver terminal that had requested the transmission of the IP multicast are set as the destination MAC addresses  2203 . 
         [0237]      FIG. 30  is a routing information table obtained by adding a MAC information table to the routing information table according to the fifth embodiment of the present invention. 
         [0238]    The routing information table shown in  FIG. 30  includes IP multicast group addresses  2301 , source IP addresses  2305 , input interface  2302 , output interface  2303 , and destination MAC addresses  2304 . 
         [0239]    We omit the detailed information on various constituent elements because they are the same as  FIG. 28  and  FIG. 29 . Incidentally, the IP multicast group addresses  2301  correspond to the IP multicast group addresses  2101 , the source IP addresses  2305  correspond to the source IP addresses  2104 . And the input interface  2302  corresponds to the input interface  2102 , and the output interface  2303  corresponds to the output interface  2103 . And the destination MAC addresses  2304  correspond to the destination MAC addresses  2203 .