fig2 is a block diagram of an isochronous stream transmission / receipt system according to an exemplary embodiment of the present invention . referring to fig2 , an isochronous stream receiving device mounted on a first node 2 according to the present invention includes an application layer 21 , a tcp / ip layer 22 , and an ieee 1394 layer 23 . when the present embodiment is implemented in practice , it will be understood by those of ordinary skill in the art that besides the layers illustrated in fig2 , other layers can be further included in the protocol stack or some layers can be substituted with other layers . for instance , a session layer can be further included , or the tcp layer can be substituted with a user datagram protocol ( udp ) layer . in addition , when the present embodiment is implemented in practice , it will be also understood by those of ordinary skill in the art that besides the elements illustrated in fig2 , other elements can be further included . for example , the tcp / ip layers 22 and 32 can further include elements defined by rfc 2734 corresponding to the ipv4 over ieee 1394 standard , and the ieee 1394 layers 23 and 33 can further include elements defined by the ieee 1394 standard . the application layer 21 includes an isochronous stream transmission requesting portion 211 , an isochronous stream receipt preparing portion 212 , and an isochronous stream receiving portion 213 . the isochronous stream transmission requesting portion 211 requests a second node 3 to transmit an isochronous stream over the ieee 1394 bus , using asynchronous block write by calling an asynchronous block write function in the application layer 21 . the ieee 1394 standard supports various transfer modes such as the asynchronous block write , an asynchronous stream , an isochronous stream , etc . in particular , commands such as ip datagram , address resolution protocol ( arp ) request / response , multicast channel allocation protocol ( mcap ) advertisement / solicitation , and the like , are transmitted using an asynchronous block write mode . therefore , the isochronous stream transmission requesting portion 211 requests the second node 3 to transmit the isochronous stream using the asynchronous block write . the isochronous stream receipt preparing portion 212 receives a response to the isochronous stream transmission request from the second node 3 , and prepares to receive the isochronous stream with reference to a channel and bandwidth included in the received response . more specifically , the isochronous stream receipt preparing portion 212 prepares to receive the isochronous stream by calling an input output control ( ioctl ) in the application layer . the ioctl , which is one of a linux command , is a function which manipulates parameters of lower layers . that is , the isochronous stream receipt preparing portion 212 sets values of registers of the ieee 1394 layer that are related to preparation for isochronous stream receipt and prepares to receive the isochronous stream by calling the ioctl . further , when the preparation for asynchronous stream receipt has been completed , the isochronous stream receipt preparing portion 212 informs the second node 3 that the isochronous stream receipt preparing portion 212 has prepared to receive the isochronous stream over the ieee 1394 bus 4 using the asynchronous block write by calling an asynchronous block write function in the application layer . the isochronous stream receiving portion 213 receives the isochronous stream , using a service of the ip , over the ieee 1394 bus 4 from the second node 3 which is informed by the isochronous stream receipt preparing portion 212 . more specifically , the isochronous stream receiving portion 213 can receive the isochronous stream over the ieee 1394 bus 4 while the qos is guaranteed using a service such as packet routing through an optimized path provided by the ip . a typical example of an isochronous stream is a moving picture content stream which needs to be transmitted in real time . the tcp / ip layer 22 includes an isochronous stream extracting portion 221 and an ip over ieee 1394 device driver 222 . the isochronous stream extracting portion 221 extracts an isochronous stream from isochronous stream packets output from an isochronous stream packet module 2213 . more specifically , the isochronous stream extracting portion 221 removes headers from the isochronous stream packets , and generates the isochronous stream by collecting data stored in payloads of the isochronous stream packets . the ip over ieee 1394 device driver 222 includes an asynchronous block write module 2211 , an asynchronous stream packet module 2212 , and the isochronous stream packet module 2213 . the asynchronous block write module 2211 supports the asynchronous block write which is based on an ip , the asynchronous stream packet module 2212 supports asynchronous stream packet transmission / receipt which is based on an ip , and the isochronous stream packet module 2213 supports isochronous stream packet transmission / receipt which is based on an ip . the ieee 1394 layer 23 includes a physical layer 231 , a link layer 232 , a transaction layer 233 and a bus management layer 234 which corresponds to the ieee 1394 device driver . the physical layer 231 physically and electrically connects the ieee 1394 layer and the ieee 1394 bus . the link layer 232 has two queues for transmission and a single queue for receipt in order to transmit and receive packets in two transmission modes , that is , an asynchronous transmission mode and an isochronous transmission mode . the two queues for transmission are divided into a queue for asynchronous transmission and a queue for isochronous transmission and used in writing , and the queue for receipt is used in reading . additionally , the link layer 232 controls a cycle for smooth transmission and receipt . fig3 illustrates a cycle configuration according to the ieee 1394 standard . referring to fig3 , a cycle master of the bus management layer 234 transmits a cycle start packet every 125 μsec . nodes receiving the cycle start packet over the ieee 1394 bus 4 synchronize the cycle on the basis of the cycle start packet . after the cycle start packet is transmitted , packets are transmitted in the isochronous transmission mode for a predetermined period of time , and packets are transmitted through channel arbitration in the asynchronous transmission mode for a remained period of time . fig4 illustrates a format of an isochronous stream packet according to an exemplary embodiment of the present invention . referring fig4 , the isochronous stream packet includes an isochronous header 51 , a cip header 52 , a tcp / ip header 53 , and a data field 54 . as shown in fig3 , the isochronous stream packet is transmitted after the cycle start packet , which is transmitted every 125 μsec . the data field 54 is composed of four packets , each of 24 bytes . when a total of eight 24 - byte packets , which are stored in data fields of two isochronous stream packets , are collected , an mpeg 2 packet composed of a time stamp ( ts ) and a transport stream packet ( tsp ) can be obtained . mpeg 2 is a typical moving picture compression standard . fig5 illustrates in detail the format of the isochronous stream packet illustrated in fig4 . referring to fig5 , an isochronous header 51 of the isochronous stream packet includes a data length field 511 , a tag field 512 , a channel field 513 , a tcode ( transaction code ) field 514 , an sy ( synchronization ) field 515 , and a header_crc ( cyclic redundancy check ) 516 . further , a data_crc field 517 is added after the data field 54 . referring to fig2 again , the link layer 232 includes an isochronous stream packet detecting portion 2321 . the isochronous stream packet detecting portion 2321 detects the isochronous stream packets in packets input from the physical layer 231 referring to values of the tag field 512 of the isochronous header 51 . a value of 00 in the tag field 512 illustrated in fig5 indicates that a packet is in an isochronous transmission mode or an asynchronous transmission mode according to the conventional ieee 1394a , and a value of 01 in the tag field 512 indicates an iec 61883 cip header . also , a value of 10 in the tag field 512 indicates the ip over ieee 1394 according to the present embodiment , and a value of 11 in tag field 512 indicates a general asynchronous stream packet ( gasp ) according to the conventional ieee 1394a standard . the isochronous stream packets are input to the isochronous stream packet module 2213 of the ip over ieee 1394 device driver 222 using the reserved value of 10 in a tag field 512 of the isochronous header 51 . the transaction layer 233 controls the link layer 232 such that reading and writing are performed on a node having a particular address . more specifically , the transaction layer 233 issues a read transaction such that a read can be performed on a node having a particular address . the transaction layer 233 also issues a write transaction such that a write can be performed on the node . additionally , the transaction layer 233 issues a lock transaction such that updates can be performed until a specific condition is satisfied . the bus management layer 234 manages the ieee 1394 bus by controlling the transaction layer 233 , the link layer 232 and the physical layer 231 . in particular , the bus management layer 234 includes an isochronous resource manager ( irm ) which manages a limited channel resource , a bandwidth resource and the like , and the cycle master which controls bus timing . referring to fig2 again , the protocol stack of the isochronous stream transmission device mounted on the second node 3 according to the present embodiment is composed of an application layer 31 , a tcp / ip layer 32 , and an ieee 1394 layer 33 . the application layer 31 includes an isochronous resource obtaining portion 311 , an isochronous stream transmission responding portion 312 , and an isochronous stream transmitting portion 313 . when the application layer 31 receives a request for transmission of the isochronous stream over the ieee 1394 bus 4 using the asynchronous block write , the isochronous resource obtaining portion 311 obtains an isochronous resource for transmission of the isochronous stream . more specifically , the isochronous resource obtaining portion 311 informs the ip over ieee 1394 device driver 322 in the ip layer 32 of the content type and the maximum packet size of the isochronous stream by calling the ioctl in the application layer 31 . the content type and the maximum packet size of the isochronous stream is used to decide a channel and bandwidth of the isochronous stream that the second node 3 intends to transmit . afterwards , the isochronous resource obtaining portion 311 is informed of the channel and the bandwidth , which correspond to the isochronous source , as a response to the content type and maximum packet size sent to the ip over ieee 1394 device driver 322 , that is , the return value for the ioctl call . in the present invention , the maximum packet size is used as a data rate . the isochronous stream transmission responding portion 312 transmits a response including information about the channel and the bandwidth , which are results of obtaining the isochronous resource in the isochronous resource obtaining portion 311 , to the first node 2 over the ieee 1394 bus 4 using an asynchronous block write by calling the asynchronous block write function in the application layer 31 . when the isochronous stream transmitting portion 313 is informed by the first node 2 , which received the response transmitted from the isochronous stream transmission responding portion 312 , that preparation for isochronous stream receipt is completed , the isochronous stream transmitting portion 313 uses the service of ip based on the obtained result in the isochronous resource obtaining portion 311 and transmits the isochronous stream over the ieee 1394 bus 4 by calling the isochronous stream transmission function in the application layer 31 . more specifically , by using a service such as packet routing through an optimized path that the ip provides , the isochronous stream transmitting portion 313 can transmit the isochronous stream over the ieee 1394 bus 4 with guaranteed qos . the tcp / ip layer 32 contains an isochronous stream packet generating portion 321 and an ip over ieee 1394 device driver 322 . the isochronous stream packet generating portion 321 generates the isochronous stream packets from the isochronous stream in the tcp / ip layer 32 according to an isochronous stream transmission function call of the isochronous stream transmitting portion 313 from the application layer 31 . in particular , the isochronous stream packet generating portion 321 records a predetermined value in a type of service ( tos ) field of an ipv4 header if the isochronous stream packet is an ipv4 packet , or a predetermined value in a traffic class field of an ipv6 header if the isochronous stream packet is an ipv6 packet so that the isochronous stream packets and the general packets can be managed by different queues in the ip over ieee 1394 device driver 322 . the specific values recorded in the tos field of the ipv4 header or the traffic class field of the ipv6 header will now be described with reference to fig6 . fig6 is a diagram for explaining packet management of the isochronous stream packet module illustrated in fig2 . referring to fig6 , each of the tos field of the ipv4 header or the traffic class field of the ipv6 header includes a differentiated service code point ( dscp ) field 531 and a currently unused ( cu ) field 532 . the isochronous stream packet generating portion 321 records a value of 00 in the cu field 532 when the packet output from the application layer 31 is a general packet , and records a value of 01 when the packet output from the application layer 31 is an isochronous stream packet . the ip over ieee 1394 device driver 322 includes an asynchronous block write module 3211 , an asynchronous stream packet module 3212 , and an isochronous stream packet module 3213 . the asynchronous block write module 3211 corresponds to the above - mentioned asynchronous block write module 2211 , the asynchronous stream packet module 3212 corresponds to the above - mentioned asynchronous stream packet module 2212 , and the isochronous stream packet module 3213 corresponds to the above - mentioned isochronous stream packet module 2213 . the ip over ieee 1394 device driver 322 is informed of the content type and the maximum packet size of the isochronous stream through the ioctl call from the application layer 31 , and informs an isochronous resource manager in the transaction layer 333 of the content type and the maximum packet size of the isochronous stream . thereafter , when the ip over ieee 1394 device driver 322 is assigned the channel and bandwidth by the isochronous resource manager , the ip over ieee 1394 device driver 322 informs the application layer 31 of the assigned channel and bandwidth . on the other hand , when the ip over ieee 1394 device driver 322 is not assigned the channel and bandwidth by the isochronous resource manager , the ip over ieee 1394 device driver 322 informs the application layer 31 that the isochronous stream cannot be transmitted . further , the ip over ieee 1394 device driver 322 registers the assigned channel and bandwidth to an output plug control register ( opcr ) and an output master plug register ( ompr ) of the second node 3 and to an input plug control register ( ipcr ) of the first node 2 and an input master plug register ( impr ) through an asynchronous lock transaction , and generates an isochronous channel for transmitting the isochronous stream packets . opcr , ompr , ipcr , and impr are registers defined by the ieee 1394 standard for generating an isochronous channel . in addition , the ip over ieee 1394 device driver 322 manages the isochronous stream packet and the general stream packet with different queues with reference to the value of the tos field of the ipv4 header when the isochronous stream packet generated by the isochronous stream packet generating portion 321 is an ipv4 packet , or with reference to the value of the traffic class field of the ipv6 header when the isochronous stream packet is an ipv6 packet . also , the ip over ieee 1394 device driver 322 transmits the isochronous stream packet based on management which will be described in detail with reference to fig6 . referring to fig6 , the isochronous stream packet module 3213 of the ip over ieee 1394 device driver 322 includes a packet divider 61 , a general packet queue 62 , and an isochronous stream packet queue 63 . the ip over ieee 1394 device driver 322 stores the general packet in the general packet queue 62 when the value of the cu field 532 in the tos field of the ipv4 header or in the traffic class field of the ipv6 header is 00 , and stores the isochronous stream packet in the isochronous stream packet queue 63 when the value of the cu field 532 is 01 . the packets stored in the general packet queue 62 and the isochronous stream packet queue 63 are stored in an ieee 1394 transmission queue 64 of the ieee 1394 device driver 322 according to a scheduling algorithm which is the most suitable for the network environment where the first node 2 and the second node 3 are placed . that is , as shown in fig3 , every 125 μsec after a cycle start packet is received , an isochronous stream packet is transmitted through the isochronous channel , and then , the asynchronous stream packets and the asynchronous block write packets are transmitted through the channel arbitration . the ieee 1394 layer 33 includes a physical layer 331 , a link layer 332 , a transaction layer 333 , and a bus management layer 334 . the transaction layer 333 , the link layer 332 , the physical layer 331 , and the bus management layer 334 correspond to an ieee 1394 device driver . the physical layer 331 corresponds to the above - mentioned physical layer 231 , the link layer 332 corresponds to the above - mentioned link layer 232 , the transaction layer 333 corresponds to the above - mentioned transaction layer 233 , and the bus management layer 334 corresponds to the above - mentioned bus management layer 234 . however , the link layer 332 includes an isochronous stream packet displaying portion 3321 instead of the isochronous stream packet detecting portion 2321 of the link layer 232 . as shown in fig4 and 5 , the isochronous stream packet displaying portion 3321 records the value of 10 , which indicates the isochronous stream packet , in the tag field 512 of the isochronous header 51 in order to distinguish the isochronous stream packet from the general packet . fig7 and 8 are flowcharts illustrating a method of transmitting and receiving an isochronous stream according to an exemplary embodiment of the present invention . referring to fig7 and 8 , the method of transmitting and receiving the isochronous stream includes the following operations . the operations of the method of transmitting and receiving an isochronous stream is processed in the first node 2 ( node a ) and the second node 3 ( node b ) illustrated in fig2 . accordingly , the above description related to the isochronous stream receiving device mounted on the first node 2 and the isochronous stream transmission device mounted on the second node 3 will be applied to the method of transmitting and receiving an isochronous stream even though the description is omitted below . in operation 71 , the isochronous stream transmission requesting portion 211 of the first node 2 sends a request to the second node 3 to transmit an isochronous stream using an asynchronous block write over the ieee 1394 bus 4 by calling the asynchronous block write function in the application layer 21 . in operation 81 , the isochronous resource obtaining portion 311 of the second node 3 receives the request for the isochronous stream transmission using the asynchronous block write over the ieee 1394 bus 4 . in operation 82 , the isochronous resource obtaining portion 311 of the second node 3 obtains the isochronous resource for transmitting the isochronous stream in response to the request received in operation 81 . more specifically , the second node 3 informs the ip over the ieee 1394 device driver 322 in the ip layer 32 of the content type and the maximum packet size of the isochronous stream by calling the ioctl in the application layer 31 . in operation 83 , the ip over ieee 1394 device driver 322 of the second node 3 is informed of the content type and the maximum packet size of the isochronous stream through the ioctl call from the application layer 31 . the ip over 1394 ieee device driver 322 informs the isochronous resource manager in the transaction layer 333 of the content type and the maximum packet size of the isochronous stream , and is assigned the channel and bandwidth by the isochronous resource manager . in operation 84 , when the ip over ieee 1394 device driver 322 of the second node 3 is assigned the channel and bandwidth in operation 83 , the ip over ieee 1394 device driver 322 registers the assigned channel and bandwidth with the opcr and ompr of the second node 3 and with the ipcr of the first node 2 and the impr through the asynchronous lock transaction to generate the isochronous channel for transmitting the isochronous stream packets , and informs the application layer 31 of the assigned channel and bandwidth . in operation 85 , when the ip over ieee 1394 device driver 322 of the second node 3 is not assigned the channel and bandwidth , the ip over ieee 1394 device driver 322 informs the application layer 31 that the isochronous stream cannot be transmitted . in operation 86 , when the isochronous stream transmission responding portion 312 of the second node 3 is informed of the channel and bandwidth informed by the ip over ieee 1394 device driver 322 in operation 84 , the isochronous stream transmission responding portion 312 transmits the response including information about the channel and bandwidth to the first node 2 using the asynchronous block write over the ieee 1394 bus 4 by calling the asynchronous block write function in the application layer 31 . on the other hand , when the isochronous stream transmission responding portion 312 is informed by the ip over ieee 1394 device driver 322 that the isochronous stream cannot be transmitted , the isochronous stream transmission responding portion 312 transmits to the first node 2 a response which indicates that the isochronous stream transmission is not possible using the asynchronous block write over the ieee 1394 bus 4 by calling the asynchronous block write function from the application layer 31 . in operation 72 , the isochronous stream receipt preparing portion 212 of the first node 2 receives from the second node 3 the response to the request for the isochronous stream transmission . in operation 73 , when the response received in operation 72 includes the channel and bandwidth for transmitting the isochronous stream , the isochronous stream receipt preparing portion 212 determines that isochronous stream transmission is possible , or determines that isochronous stream transmission is not possible when the response indicates that the isochronous stream transmission is not possible . in operation 74 , when it is determined that the isochronous stream transmission is possible in operation 73 , the isochronous stream receipt preparing portion 212 of the first node 2 prepares to receive the isochronous stream with reference to the channel and bandwidth included in the response by calling the ioctl in the application layer 21 . in operation 75 , when it is determined that the isochronous stream transmission is not possible in operation 73 , the isochronous stream receipt preparing portion 212 of the first node 2 terminates an isochronous stream transmission request process . in operation 76 , when the isochronous stream receipt preparing portion 212 of the first node 2 completes the preparation for the isochronous stream receipt , the isochronous stream receipt preparing portion 212 informs the second node 3 that the isochronous stream receipt has been prepared using the asynchronous block write over the ieee 1394 bus 4 by calling the asynchronous block write function in the application layer 21 . in operation 87 , when the isochronous stream transmitting portion 313 of the second node 3 is informed of the fact that the isochronous stream receipt has been prepared in operation 76 , the isochronous stream transmitting portion 313 transmits the isochronous stream to the first node 2 using the service of ip based on the obtaining result of the isochronous resource obtaining portion 311 over the ieee 1394 bus 4 by calling the isochronous stream transmission function in the application layer 31 . in operation 77 , the isochronous stream receiving portion 213 receives the isochronous stream from the second node 3 , which has received the information from the isochronous stream receipt preparing portion 212 , by using the service of the ip over the ieee 1394 bus 4 . the operations 71 through 77 are included in the method of receiving the isochronous stream , and the operations 81 through 87 are included in the method of transmitting the isochronous stream . fig9 is a flowchart illustrating in detail operation 87 illustrated fig8 . referring to fig9 , operation 87 includes the following operations . in operation 871 , the isochronous stream transmitting portion 313 of the second node 3 outputs the isochronous stream from the application layer 31 to the tcp / ip layer 32 . in operation 872 , the isochronous stream packet generating portion 321 of the second node 3 generates the isochronous stream packets from the isochronous stream output in operation 871 . in particular , the isochronous stream packet generating portion 321 of the second node 3 records a predetermined value in the tos field of the ipv4 header when the isochronous stream packet is an ipv4 packet or records a predetermined value in the traffic class field of the ipv6 header when the isochronous stream packet is an ipv6 packet so that the isochronous stream packet and the general packet are managed with different queues by the ip over the ieee 1394 device driver 322 . in operation 873 , the ip over ieee 1394 device driver 322 of the second node 3 manages the isochronous stream packet and the general packet with different queues with reference to the value of the tos field of the ipv4 header when the isochronous stream packet generated in operation 872 is an ipv4 packet or with reference to the value of the traffic class field of the ipv6 packet when the isochronous stream packet is an ipv6 packet . also , the ip over ieee 1394 device driver 322 transmits the isochronous stream packet based on the management . more specifically , the ip over ieee 1394 device driver 322 of the second node 3 stores the general packet in the general packet queue 62 when the value of the cu field 532 of the tos field in the ipv4 header or the traffic class field in the ipv6 header is 00 , and stores the isochronous stream packet in the isochronous stream packet queue 63 when the value of the cu field 532 is 01 . in operation 874 , the ieee 1394 layer 33 of the second node 3 stores the packets which are stored in the general packet queue 62 and the isochronous stream packet queue 63 in operation 873 in an ieee 1394 transmission queue 64 according to a scheduling algorithm which is the most suitable for the network environment where the first node 2 and the second node 3 are placed . in operation 875 , the ieee 1394 layer 33 of the second node 3 transmits the isochronous stream packets in the order that they are stored in the ieee 1394 transmission queue 64 in operation 874 . at this moment , the isochronous stream packet displaying portion 3321 of the ieee 1394 layer 33 records a value of 10 which indicates an isochronous stream packet in the tag field 512 of the isochronous header 51 so that the isochronous stream packet can be distinguished from the general packets . fig1 is a flowchart illustrating in detail operation 76 illustrated in fig8 . referring to fig1 , operation 76 includes the following operations . in operation 761 , the isochronous stream packet detecting portion 2321 of the first node 2 detects the isochronous stream packets from the packets input from the physical layer 231 with reference to the value of the tag field 512 of the isochronous header 51 , and outputs the detected isochronous stream packets to the isochronous stream packet module 2213 of the ip over ieee 1394 device driver 222 . in operation 762 , the isochronous stream extracting portion 221 of the first node 2 extracts the isochronous stream from the isochronous stream packets output from the isochronous stream packet module 2213 which received the isochronous stream packets in operation 761 . more specifically , the isochronous stream extracting portion 221 of the first node 2 removes headers from the isochronous stream packets and collects data recorded in payloads of the isochronous stream packets to generate the isochronous stream , and outputs the generated isochronous stream to the isochronous stream receiving portion 213 of the application layer 21 . in operation 763 , the isochronous stream receiving portion 213 of the first node 2 receives the isochronous stream which was output in operation 762 . the embodiments of the present invention can be written as computer programs and can be implemented in general - use digital computers that execute the programs using a computer readable recording medium . examples of the computer readable recording medium include magnetic storage media ( e . g ., rom , floppy disks , hard disks , etc . ), optical recording media ( e . g ., cd - roms , or dvds ), and storage media such as carrier waves ( e . g ., transmission through the internet ). according to the present invention , by allowing an ip over ieee 1394 to support isochronous stream transmission , an isochronous stream can be efficiently and securely transmitted using an ip service . that is , isochronous stream packets can be transmitted with a qos that is guaranteed through an optimized path . as a result , the quality of the real - time transmission of multimedia contents , for example , voice over ip ( voip ), image communications and a streaming service between it devices and electric home appliances can be enhanced . in particular , the present invention is more useful for ip over ieee 1394 - based isochronous stream transmission when time division type isochronous ethernet according to an the ieee 802 . 9 committee standard is supported . further , according to the present invention , both isochronous stream transmission and asynchronous stream transmission can be supported in a single application , and isochronous stream packets can be more rapidly transmitted by managing the isochronous stream packets with different queues . while the present invention has been particularly shown and described with reference to exemplary embodiments thereof , it will be understood by those of ordinary skill in the art that various changes in form and details may be made therein without departing from the spirit and scope of the present invention as defined by the following claims .