JP2010147802A - Receiving terminal which receives packet whose header is compressed - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To acquire desired datagram without recovering header information of a received packet to original IP header information. <P>SOLUTION: A CID header information storing and CID responding part 22 generates a CID record by a CID (a context identifier) identified from a received header-compressed packet and header information extracted from the packet, and stores the CID record in a CID table. The CID table is searched to specify the CID using a designated IP address. A filter 24 selects the desired header-compressed packet by the CID. Payload extracting parts 25-A to 25-C extract datagram from a payload of the desired header-compressed packet. Thereby, an application part 21-1 can acquire the desired datagram corresponding to designated IP address. <P>COPYRIGHT: (C)2010,JPO&INPIT

Description

  In the present invention, when a content file is packetized and transmitted, the IP header information is replaced with a context identifier (CID: Context Identifier), the header is compressed, and a transmission terminal that transmits the header-compressed packet and the packet are received In a transmission system configured with a receiving terminal that restores an original content file, a technique for acquiring a datagram of content transmitted by a packet without restoring compressed header information to the original IP header information About.

  Conventionally, ROHC (RObust Header Compression) defined in RFC3095, Enhanced CRTP defined in RFC3545, and the like are known as header compression techniques for compressing the header of a packet, and these header compression techniques are used in an actual transmission system. Development to apply has been underway. For example, in a transmission system composed of terminals and servers, header information is compressed and decompressed (decompressed) so that throughput does not decrease even on non-target transmission lines with different uplink and downlink channel lines. ) And a packet that is not compressed and transmitted (refer to Patent Document 1). Also, a technique for transmitting a specific packet together with subsequent packets until a predetermined condition is satisfied so that the header information can be correctly reconstructed even if a packet having compressed header information is lost or error occurs. Is known (see Patent Document 2).

  On the other hand, among the transmission systems using the header compression technique described above, there is a system that compresses IP header information including an IP header and a UDP header and transmits the compressed header packet (header compressed packet) (Non-Patent Document 1). reference). In this transmission system, instead of transmitting all packets with all header information, header compressed packets are transmitted to improve transmission efficiency in the transmission system. Here, the IP header information is replaced with a context identifier called CID and compressed, and the CID is used as information for specifying the IP data flow of the header compressed packet.

  FIG. 8 is a diagram showing a schematic configuration of a system that compresses IP header information of an IP packet and transmits it as a header compressed packet. This transmission system is a satellite broadcasting system that realizes advanced BS digital broadcasting, a file transmission device and a multiplexing device (transmission terminal 1) provided in a broadcasting station, and a tuner device (reception) provided in a general household, for example. A terminal 2) and an application device are provided. The transmission terminal 1 and the reception terminal 2 are connected by a unidirectional transmission path 3 which is a broadcast transmission path via a broadcasting satellite. In addition, the file transmission device in the broadcasting station and the transmission terminal 1 are connected by an IP network, and the reception terminal 2 and the application device 4 in a general household are connected by an IP network constituting the home network.

  The transmission terminal 1 receives an IP packet from a file transmission device that transmits a content file, multiplexes the received IP packet, and transmits a broadcast wave to the reception terminal 2 via the one-way transmission path 3. Specifically, the transmission terminal 1 generates a TLV (Type Length Value) including information for realizing a television broadcast service and content for realizing a content load service. At this time, the transmission terminal 1 compresses the IP header information of the IP packet and replaces it with the CID, and stores the packet having the header including the CID in the TLV and transmits the packet. The TLV stores IP packets including content to be distributed and download control information necessary for download control.

  The receiving terminal 2 receives the broadcast wave from the transmitting terminal 1 via the one-way transmission path 3, extracts the CID from the received broadcast wave packet, restores it to IP header information, and generates an IP packet. Then, the receiving terminal 2 transmits the generated IP packet to the application device 4 via the IP network. The application device 4 receives the IP packet and acquires a desired datagram from the payload of the IP packet. As described above, the application device 4 in a general home can be downloaded from the file transmission device provided in the broadcasting station by the download application software via the transmission terminal 1, the one-way transmission path 3, and the reception terminal 2 by the operator. An IP packet of desired content can be received to obtain a desired datagram. Thereby, the operator can view or record desired content.

  FIG. 9 is a diagram illustrating a header compression method in which header information is compressed in the transmission terminal 1 and header information is restored in the reception terminal 2. Referring to FIG. 9, an IP packet is composed of an “IP header”, “UDP header”, and “payload”. The header compressed packet is classified into a full header packet and a compressed header packet. The full header packet is composed of “full header” and “payload”, and the compressed header packet is composed of “compressed header” and “payload”.

  The transmission terminal 1 receives an IP packet to be transmitted, distinguishes the IP packet based on an IP header and a UDP header added to the IP packet, and specifies an IP data flow. Here, the IP header includes a protocol type, a source IP address, and a destination IP address, and the UDP header includes a source port number and a destination port number. Identified. An IP data flow is an IP packet having a unique combination of the values of five fields of protocol type, source IP address, destination IP address, source port number, and destination port number included in the IP header and UDP header. A set. That is, the IP data flow specified by the information included in the IP header and the UDP header is a set of IP packets in the same content file sent by the file sending device shown in FIG.

  The transmission terminal 1 identifies a CID that can be assigned for each identified IP data flow, and generates a CID table including the CID and header information. Here, the CID is an identifier used to identify the IP data flow described above.

  FIG. 11 is a diagram showing the configuration of the CID table. (1) is a CID table when the IP header is IPv4, and (2) is a CID table when the IP header is IPv6. In (1), the IPv4 CID table includes a CID, an IPv4 header, and a UDP header. The IPv4 header includes a version (version) indicating the version of the IP header, an IHL (Internet Header Length), a TOS (Type Of Service: service type), an IP-ID (IP-Identification: IP identification number), and a flag. (Flag), Fragment Offset (fragment offset), TTL (Time To Live), Protocol (protocol), SrcAddr (source IP address), and DstAddr (destination IP address). The UDP header is composed of SrcPort (source port number) and DstPort (destination port number). In addition to the above, the IPv4 header has Total Length (packet length) and Header Checksum (header checksum), and the UDP header has Length (data length) and Checksum (checksum) in addition to the above. Since these values are assumed to be different for each packet, they are not held in the CID table.

  In (2), the IPv6 CID table includes a CID, an IPv6 header, and a UDP header. The IPv6 header includes a version (version), a traffic class (traffic class), a flow label (flow label), a next header (next header), a hop limit (hop limit), and a srcAddr (source IP address) indicating the version of the IP header. And DstAddr (destination IP address). The UDP header is composed of SrcPort (source port number) and DstPort (destination port number). In addition to the above, the IPv6 header has a payload length (payload length), and the UDP header has a length (data length) and a checksum (checksum) in addition to the above. Since they are assumed to be different, they are not held in the CID table.

  Returning to FIG. 9, the transmission terminal 1 generates a full header packet to which header information including a CID, an IP header, and a UDP header is added and intermittently transmits the packet. At other times, a compressed header packet to which header information including CID is added is generated and transmitted. Thus, the full header packet and the compressed header packet are transmitted as a header compressed packet to which the compressed header information is added.

  FIG. 12 is a diagram showing a configuration of header compressed packets (full header packet and compressed header packet). (1) shows the configuration of an IPv4 full header packet, (2) shows the configuration of an IPv4 compressed header packet, (3) shows the configuration of an IPv6 full header packet, and (4) 3 shows the structure of an IPv6 compressed header packet. The numbers indicate the byte length of each data item (the same applies to FIGS. 13 to 15).

  In (1), an IPv4 full header packet includes a CID, an SN (sequence number) indicating the order of packets having the same CID, a CID_header_type (CID header type: 0x20) indicating the type of header information, IPv4_header_wo_length, UDP_header_wo_length and data. Consists of bytes. CID, SN, CID_header_type (CID header type), IPv4_header_wo_length, and UDP_header_wo_length correspond to the full header part constituting the full header packet shown in FIG. 9, and the data byte corresponds to the payload part. IPv4_header_wo_length is a partial IPv header (partial IPv header) with respect to the IPv4 header included in the IP header information of the IP packet, and is obtained by removing the packet length and the header checksum from the IPv4 header. Furthermore, UDP_header_wo_length is a partial UDP header (partial UDP header) with respect to the UDP header included in the IP header information of the IP packet, and is obtained by removing the data length and the checksum from the UDP header of the IP packet.

  In (2), the compressed header packet of IPv4 includes a CID, SN (sequence number) indicating the order of packets having the same CID, CID_header_type (CID header type: 0x21), and identification (identification) indicating the identification number of the IPv4 header. ID number) and data bytes. CID, SN, CID_header_type (CID header type), and identification correspond to the compressed header part that constitutes the compressed header packet shown in FIG. 9, and the data byte corresponds to the payload part.

  In (3), the IPv6 full header packet is composed of CID, SN (sequence number) indicating the order of packets having the same CID, CID_header_type (CID header type: 0x60), IPv6_header_wo_length, UDP_header_wo_length, and data bytes. The CID, SN, CID_header_type (CID header type), IPv6_header_wo_length, and UDP_header_wo_length correspond to the full header part constituting the full header packet shown in FIG. 9, and the data byte corresponds to the payload part. IPv6_header_wo_length is a partial IPv header (partial IPv header) with respect to the IPv6 header included in the IP header information of the IP packet, and is obtained by removing the payload length from the IPv6 header. Furthermore, UDP_header_wo_length is a partial UDP header (partial UDP header) with respect to the UDP header included in the IP header information of the IP packet, and is obtained by removing the data length and the checksum from the UDP header of the IP packet.

  In (4), the IPv6 compressed header packet is composed of a CID, an SN (sequence number) indicating the order of packets having the same CID, a CID_header_type (CID header type: 0x61), and a data byte. CID, SN, and CID_header_type (CID header type) correspond to the compressed header portion that constitutes the compressed header packet shown in FIG. 9, and the data byte corresponds to the payload portion.

  (1) to (4) are distinguished by CID_header_type (CID header type) in the full header packet and the compressed header packet. Further, IPv4_header_wo_length and UDP_header_wo_length in the IPv4 full header packet according to (1) respectively correspond to the IPv4 header and the UDP header in the IPv4 CID table shown in FIG. 11 (1). Further, IPv6_header_wo_length and UDP_header_wo_length in the IPv6 full header packet according to (3) correspond to the IPv6 header and the UDP header in the IPv6 CID table shown in FIG. 11 (2), respectively.

  FIG. 13 is a diagram illustrating a configuration of IPv4_header_wo_length in the IPv4 full header packet illustrated in FIG. This IPv4_header_wo_length is a version (version) indicating the version of the IP packet, IHL, TOS (Type Of Service: service type), IP-ID (IP-Identification: IP identification number), Flag (flag), Fragment Offset (fragment offset) ), TTL (Time To Live), Protocol (protocol), SrcAddr (source IP address) and DstAddr (destination IP address).

  FIG. 14 is a diagram illustrating a configuration of IPv6_header_wo_length in the IPv6 full header packet illustrated in FIG. This IPv6_header_wo_length is a version (version) indicating the version of the IP packet, traffic class (traffic class), flow label (flow label), next header (next header), Hop Limit (hop limit), SrcAddr (source IP address). And DstAddr (destination IP address).

  FIG. 15 is a diagram showing a configuration of UDP_header_wo_length in the IPv4 and 6 full header packets shown in FIGS. 12 (1) and 12 (3). This UDP_header_wo_length is composed of SrcPort (source port number) and DstPort (destination port number). Refer to Non-Patent Document 1 for details of the configuration shown in FIGS.

  Returning to FIG. 9, the receiving terminal 2 receives the header compressed packet. Specifically, the receiving terminal 2 first receives a full header packet, and subsequently receives a compressed header packet. The receiving terminal 2 needs to restore the compressed header information to the same IP header and UDP header as at the time of transmission and generate an IP packet. This is because the application device 4 receives the IP packet and needs to specify the IP packet based on the source IP address, the destination IP address, the destination port number, etc. stored in these headers (IP header and UDP header). This is because a desired datagram is obtained from the identified IP packet.

  When the received header compressed packet is a full header packet, the receiving terminal 2 associates the CID included in the full header of the full header packet with the IP header and the UDP header, and stores the information in the CID table. . In addition, when the received header compressed packet is a compressed header packet, the receiving terminal 2 searches the CID table based on the CID included in the compressed header of the compressed header packet, and obtains the IP header and UDP header associated with the CID. Acquire and restore the CID to the original IP header and UDP header. In this way, the receiving terminal 2 generates an IP packet and transmits it to the application device 4.

  FIG. 10 is a block diagram showing the configuration of a conventional receiving terminal 2 and application device 4, and each period from when the receiving terminal 2 receives a header compressed packet until the application device 4 acquires a desired datagram. The component which performs a process is shown. The receiving terminal 2 includes a CID identification unit 51, a type identification unit 52, a CID / header information storage unit 53, and a header restoration unit 54. In addition, the application apparatus 4 includes a filter unit 55 and a payload extraction unit 56.

  When the receiving terminal 2 receives the header compressed packet, the CID identifying unit 51 inputs the header compressed packet, extracts the CID from the header information of the header compressed packet, and identifies the CID. Then, the CID identifying unit 51 outputs the identified CID to the CID / header information storage unit 53, and outputs the input header compressed packet to the type identifying unit 52. The header (compressed header) of the header compressed packet is restored to the original IP header and UDP header in the header restoration unit 54 at the subsequent stage for each identified CID.

  The type identifying unit 52 inputs the header compressed packet from the CID identifying unit 51, extracts CID_header_type (CID header type) from the header information of the header compressed packet, and identifies the CID header type. As shown in FIG. 12, four CID_header_type = 0x20, 0x21, 0x60, and 0x61 are assigned to the CID header type. The type identification unit 52 determines that the header compressed packet is an IPv4 full header packet when CID_header_type = 0x20, and determines that the header compressed packet is an IPv4 compressed header packet when CID_header_type = 0x21. When CID_header_type = 0x60, it is determined that the header compressed packet is an IPv6 full header packet. When CID_header_type = 0x61, it is determined that the header compressed packet is an IPv6 compressed header packet.

  When it is determined that the input header compressed packet is a full header packet, the type identification unit 52 extracts header information from the full header packet and outputs the header information to the CID / header information storage unit 53. Also, the input header compressed packet is output to the header restoration unit 54. Here, as shown in FIG. 12, the header information is CID, SN, CID_header_type (CID header type), IPv4_header_wo_length, and UDP_header_wo_length in the case of an IPv4 full header packet. , SN, CID_header_type (CID header type), IPv6_header_wo_length, and UDP_header_wo_length.

  The CID / header information storage unit 53 receives the CID from the CID identification unit 51 and the header information from the type identification unit 52, and compares the input CID with the CID included in the input header information. If the CID / header information storage unit 53 determines that the CIDs are the same, the CID / header information storage unit 53 associates the input CID with the input header information, and generates a CID record as shown in FIG. Save to.

  The header restoration unit 54 receives the header compressed packet from the type identifying unit 52, performs the same processing as the type identifying unit 52 identifies the type and determines the type of the header compressed packet, and the header compressed packet is a full header. When it is determined that the packet is a packet, CID, SN, and CID_header_type (CID header type) are removed from the header information of the full header packet.

  The header restoration unit 54 calculates the packet length and the header checksum in the IP header in the case of IPv4, the payload length in the case of IPv6, based on the length calculated from the “data length” field of the TLV. The data length and checksum in the UDP header are calculated. Then, the header restoration unit 54 adds the calculated packet length and header checksum to IPv4_header_wo_length that is a partial IPv4 header in the case of IPv4, and adds the calculated payload length to IPv6_header_wo_length that is a partial IPv6 header in the case of IPv6. Restore to IP header. Also, the calculated data length and checksum are added to UDP_header_wo_length to restore the UDP header. Then, the header restoring unit 54 generates an IP packet using the restored IP header and UDP header as IP header information.

  On the other hand, if the header restoration unit 54 determines that the header compressed packet is a compressed header packet, the header restoration unit 54 extracts the CID from the header information of the compressed header packet, and uses the CID as a key to retrieve the CID record from the CID table of the CID / header information storage unit 53. Is read. Then, the header restoring unit 54 acquires the partial IPv4, 6 header and the partial UDP header from the CID record, calculates the data length and the like as described above, and restores the compressed header to the IP header and UDP header to obtain the IP header. Generate a packet. The receiving terminal 2 transmits the IP packet generated by the header restoring unit 54 to the application device 4.

  When the application apparatus 4 receives an IP packet from the receiving terminal 2, the filter unit 55 inputs the IP packet, refers to the header information of the IP packet, and designates an IP address (transmission) to obtain a desired datagram. Only IP packets having a source IP address and a destination IP address) and a port number (destination port number) are selected and filtered.

  Specifically, between the receiving terminal 2 and the application apparatus 4, IGMP (Internet Group Management Protocol) defined in RFC2236, which is a reception control protocol for IP multicast packets, or MLD (Multicast Listener Discovery) defined in RFC3810. ) And other protocols have been established. The application apparatus 4 specifies a desired IP multicast group address according to such a protocol, and receives only IP packets having a desired IP address (source IP address and destination IP address) from the receiving terminal 2. Then, the filter unit 55 performs filtering for selecting only an IP packet having a desired port number (destination port number) among the IP packets, and outputs the desired IP packet to the payload extracting unit 56.

  The payload extraction unit 56 receives the IP packet from the filter unit 55 and extracts a datagram from the payload of the IP packet. In this way, the download application software of the application apparatus 4 can obtain a desired datagram.

"Information and Communication Council, Information and Communication Technology Subcommittee (60th) Report of the 60-1-2 Broadcasting System Committee", [online], July 29, 2008, Information and Communication Council, [November 2008] Search on May 12], Internet <URL: http://www.soumu.go.jp/joho_tsusin/policyreports/joho_tsusin/bunkakai/080729_1.html> Japanese Patent No. 3540641 Japanese Patent No. 3559019

  In the transmission system described above, the receiving terminal 2 receives the header compressed packet transmitted by the transmitting terminal 1, restores the compressed header information of the header compressed packet to the original IP header information, and generates an IP packet. Then, the application device 4 acquires a desired datagram from the IP packet. Thus, in order for the application device 4 to obtain a desired datagram, the receiving terminal 2 needs to restore the IP header information and generate an IP packet.

  However, in the transmission system described above, it may not be necessary to restore the compressed header information to the IP header information. For example, when there is no network that needs to transfer IP packets, or when the receiving terminal 2 and the application device 4 are integrated and provided in the same housing, the IP header information restoration processing is necessary. There is no need to generate an IP packet. As described above, when the receiving terminal 2 that receives the header compressed packet does not need the IP header information, it is desired to omit the restoration process of the IP header information and reduce the processing load.

  Therefore, the present invention has been made to solve the above-described problems, and an object of the present invention is to make the header information of the received packet the original IP header information in the receiving terminal that receives the packet in which the IP header information is compressed. An object of the present invention is to provide a receiving terminal capable of acquiring a desired datagram without restoring it.

  In order to solve the above problem, the receiving terminal according to the present invention determines an IP data flow of content to be transmitted based on an IP address and a port number, and adds a header including a context identifier (CID) for specifying the IP data flow. And receiving the header-compressed packet under a transmission system that transmits the packet as a header-compressed packet, and acquiring a datagram of a predetermined content from the packet, the CID is obtained from the header of the received packet. A CID identifying unit that identifies a header type from the received packet, and if the identified header type is a type that includes an IP address in a header, a type identifying unit that extracts an IP address from the header of the packet; The CID identified by the CID identification unit; A CID table configured by a CID record including an IP address extracted by an IP identification unit, and a search for the CID table based on an IP address designated to obtain a datagram of the predetermined content; A CID specifying unit that specifies a CID from a CID record including an IP address, a filter unit that selects a packet having a CID specified by the CID specifying unit from the received packets, and a filter unit selected by the filter unit A payload extracting unit that extracts a datagram of content from the payload of the packet.

  In the receiving terminal according to the present invention, the CID specifying unit specifies a plurality of CIDs, and the filter unit selects any one of the plurality of CIDs specified by the CID specifying unit from among the received packets. A packet having the CID is selected for each CID, and the payload retrieving unit retrieves a content datagram from the payload of the packet for each CID selected by the filter unit. It is characterized by.

  In the receiving terminal according to the present invention, when the type identifying unit identifies a header type from the received packet, and the identified header type is a type including an IP address and a port number in the header, the header of the packet The IP address and the port number are extracted from the CID table, and the CID table is configured by a CID record including the CID identified by the CID identifying unit and the IP address and the port number retrieved by the type identifying unit. A unit searches the CID table based on an IP address and a port number designated for obtaining a datagram of the predetermined content, and specifies a CID from a CID record including the IP address and the port number; It is characterized by.

  The receiving terminal according to the present invention determines the IP data flow of the content to be transmitted based on the IP address and port number, adds a header including a context identifier (CID) for specifying the IP data flow, and compresses the header. A CID including a preset CID, IP address, and port number at a receiving terminal that receives the header-compressed packet and obtains a datagram of a predetermined content from the packet under a transmission system that transmits the packet. A CID specification that searches a CID table based on a CID table configured by records and an IP address designated to obtain a datagram of the predetermined content, and specifies a CID from a CID record including the IP address And the received packet A filter unit for selecting a packet having a CID specified by the CID specifying unit, and a payload extracting unit for extracting a datagram of content from the payload of the packet selected by the filter unit. Features.

  The receiving terminal according to the present invention determines the IP data flow of the content to be transmitted based on the IP address and port number, adds a header including a context identifier (CID) for specifying the IP data flow, and compresses the header. In addition to transmitting as a packet, the CID is described in download control information including the location information of the content, the distribution start time and distribution end time of the content, and the content ID, and the header compressed packet is transmitted. A receiving terminal that receives the download control information and a header-compressed packet under a transmission system that transmits the download control information in advance, and obtains a datagram of a predetermined content from the packet. The described CID A CID specifying unit that specifies a CID for acquiring a datagram of a predetermined content; a filter unit that selects a packet having a CID specified by the CID specifying unit from the received packets; and the filter unit And a payload extracting unit that extracts a content datagram from the payload of the packet selected by.

  As described above, according to the present invention, a receiving terminal selects a packet using a CID and extracts a datagram from the selected packet. This makes it possible to acquire a desired datagram without restoring the header information of the received packet to the original IP header information.

  The best mode for carrying out the present invention will be described below in detail with reference to the drawings. A feature of the present invention is that a receiving terminal receives a packet having header information in which IP header information is compressed, and selects a desired packet without restoring the header information of the received packet to the original IP header information. The purpose is to obtain a desired datagram from the payload of the selected packet. In the first to fourth embodiments described below, an apparatus in which the receiving terminal 2 and the application apparatus 4 illustrated in FIG. 8 are integrated is assumed as the receiving terminals 2-1 to 2-4. Hereinafter, Examples 1-4 will be described in detail.

[Example 1]
In the first embodiment, a desired packet is selected using an IP address (source IP address and destination IP address) without restoring the header information of the received packet to the original IP header information, and the payload of the selected packet is selected. To obtain a desired datagram. In this case, a packet having a plurality of different destination port numbers is also selected, but a desired datagram can be acquired by restricting use of only one destination port number.

  FIG. 1 is a block diagram showing a configuration of a receiving terminal according to an embodiment (Example 1) of the present invention. The receiving terminal 2-1 includes a CID identification unit 51, a type identification unit 52, an application unit 21-1, a CID / header information storage and CID response unit (CID identification unit) 22, an IGMP / MLD processing unit 23, and a filter unit 24. And payload take-out units 25-A to 25-C. In the CID / header information storage and CID response unit 22 CID table, there are three destination port numbers for one IP address (source IP address and destination IP address) specified by the application unit 21-1. Each existing CID record is stored, the CID / header information storage and CID response unit 22 specifies three CIDs, the filter unit 24 selects three header compressed packets A to C for each CID, and the payload Assume that the extraction units 25-A to 25-C extract three datagrams A to C for each CID.

  The CID identifying unit 51 and the type identifying unit 52 have the same functions as the CID identifying unit 51 and the type identifying unit 52 shown in FIG. The application unit 21-1 specifies an IP address (source IP address and destination IP address), and acquires a desired datagram. The IGMP / MLD processing unit 23 stores an IP address (source IP address and destination IP address) designated by the application unit 21-1 using IGMP, MLD or the like as a reception control protocol, and stores CID / header information and a CID response. Notification to the unit 22.

  The CID / header information storage and CID response unit 22 inputs the CID from the CID identification unit 51 and the header information from the type identification unit 52, like the CID / header information storage unit 53 shown in FIG. The CID is associated with the header information, and a CID record is generated and stored in the CID table as shown in FIG. Further, the CID / header information storage and CID response unit 22 searches the CID table using the IP address (source IP address and destination IP address) notified by the reception control protocol such as IGMP or MLD, and specifies the CID. To do.

  The filter unit 24 performs filtering for selecting only packets having the CID specified by the CID / header information storage and CID response unit 22. The payload extraction units 25-A to 25-C extract datagrams A, B, and C from the payload of the packet selected by the filter unit 24, respectively.

  Next, the process of the receiving terminal 2-1 shown in FIG. 1 will be described. FIG. 2 is a flowchart for explaining processing of the receiving terminal 2-1 according to the first embodiment. First, the application unit 21-1 specifies an IP address (source IP address and destination IP address) to be added to the packet of the datagram to be acquired in order to acquire a desired datagram, and filtering is performed in the filter unit 24. A command to start reception control for starting is output to the IGMP / MLD processing unit 23. The reception control start command is output to the filter unit 24 via the IGMP / MLD processing unit 23, the CID / header information storage and CID response unit 22, and the filter unit 24 starts reception control by filtering.

  The IGMP / MLD processing unit 23 receives a reception control start command including an IP address (a transmission source IP address and a destination IP address) from the application unit 21-1, and receives the IP address (transmission) by the IGMP or MLD reception control protocol. An instruction to start reception control including the original IP address and the destination IP address is sent to the CID / header information storage and CID response unit 22 (steps S21 and S22).

  The CID / header information storage and CID response unit 22 receives an instruction to start reception control including the IP address (source IP address and destination IP address) from the IGMP / MLD processing unit 23, searches the CID table, and searches for the IP address. A CID record having the same data as (source IP address and destination IP address) is read from the CID table, and the CID is specified (step S23). The CID table stores a CID record in which a CID and header information including an IP address (source IP address and destination IP address) are associated with each other. Therefore, the CID / header information storage and CID response unit 22 The CID can be specified based on the IP address (source IP address and destination IP address). Then, the CID / header information storage and CID response unit 22 sends a reception control start command including the specified CID as a response to the reception control start command including the input IP address (source IP address and destination IP address). Output to the filter unit 24.

  The filter unit 24 receives an instruction to start reception control including the CID from the CID / header information storage and CID response unit 22, selects only the header compressed packet having the CID, and performs filtering (step S24). Since the CID is an identifier specified by an IP address (source IP address and destination IP address), the CID / header information storage and CID response unit 22 may specify a plurality of CIDs. For this reason, the filter unit 24 selects header compressed packets having designated IP addresses (source IP address and destination IP address) and having different destination port numbers.

  For example, when the CID / header information storage and CID response unit 22 specifies three CIDs, the filter unit 24 performs filtering for each of these three CIDs. Then, as shown in FIG. 1, the filter unit 24 is a header compressed packet having a designated IP address (source IP address and destination IP address), and has a first destination port number. A is selected and output to the payload takeout unit 25-A. Further, the header compression packet B having the designated IP address (source IP address and destination IP address) and having the second destination port number is output to the payload extraction unit 25-B. Further, the header compression packet C having the specified IP address (source IP address and destination IP address) and having the third destination port number is output to the payload extraction unit 25-C.

  The payload extraction unit 25-A receives the header compressed packet A having the first destination port number from the filter unit 24, extracts the datagram A from the payload, and outputs it to the application unit 21-1 (step S25). Similarly, the payload extraction unit 25-B receives the header compressed packet B having the second destination port number from the filter unit 24, extracts the datagram B from the payload, and outputs it to the application unit 21-1. The payload takeout unit 25-C receives the header compressed packet C having the third destination port number from the filter unit 24, takes out the datagram C from the payload, and outputs it to the application unit 21-1.

  The application unit 21-1 inputs the datagrams A to C from the payload extraction units 25-A to 25-C. Thereby, the application unit 21-1 can obtain a desired datagram corresponding to the designated IP address (source IP address and destination IP address) for each destination port number (step S26).

  The application unit 21-1 specifies an IP address (source IP address and destination IP address) on which reception control is performed in order to end acquisition of a desired datagram, and stops filtering in the filter unit 24. Command to end the reception control is output to the IGMP / MLD processing unit 23. The reception control end command is output to the filter unit 24 via the IGMP / MLD processing unit 23, the CID / header information storage and CID response unit 22, and the reception control by filtering ends in the filter unit 24 (step S27). In this case, the CID / header information storage and CID response unit 22 inputs the IP address (source IP address and destination IP address) from the application unit 21-1 via the IGMP / MLD processing unit 23, and searches the CID table. Then, the CID is specified, and a reception control end command including the specified CID is output to the filter unit 24. Thereby, the application unit 21-1 can stop the input of the datagram corresponding to the designated IP address (source IP address and destination IP address).

  As described above, according to the receiving terminal 2-1 of the first embodiment, the CID / header information storage and CID response unit 22 uses the designated IP address (source IP address and destination IP address) to specify the CID. The filter unit 24 selects a desired header compressed packet based on the CID, and the payload extraction units 25-A to 25-C extract datagrams from the desired header compressed packet. Thereby, the application part 21-1 can acquire the desired datagram corresponding to the designated IP address (source IP address and destination IP address). Therefore, the receiving terminal 2-1 can obtain a desired datagram without restoring the header information of the received header compressed packet to the original IP header information, so that the processing load is reduced with a simple configuration. It becomes possible to do. In addition, since the processing load is reduced, reception at a high packet rate is possible.

  Further, according to the receiving terminal 2-1 of the first embodiment, the CID / header information storage and CID response unit 22 determines the CID identified by the CID identifying unit 51 and the full identifying packet by the type identifying unit 52. In addition to generating header information and generating a CID record and storing it in the CID table, the CID table is identified using the input IP address (source IP address and destination IP address). To do. As a result, a CID record in which the CID and the header information are associated with each other is stored in the CID table, and the CID and the IP data flow are associated with each other using the header information of the full header packet. It will be the same and will not be restricted.

  Note that IGMP and MLD are widely used for controlling the start and end of reception of IP multicast packets. In the first embodiment, IGMP or MLD by the IGMP / MLD processing unit 23 is used as means for notifying the IP address. However, it is not essential to use these reception control protocols.

[Example 2]
The second embodiment selects a desired packet by using the IP address (source IP address and destination IP address) and destination port number without restoring the header information of the received packet to the original IP header information. The desired datagram is obtained from the payload of the packet that has been received. Comparing Example 1 and Example 2, in Example 1, even if filtering is performed by the specified CID, packets having a plurality of different destination port numbers are also selected. On the other hand, in the second embodiment, only a packet having a predetermined destination port number is selected by filtering with the specified CID.

  FIG. 3 is a block diagram showing a configuration of a receiving terminal according to the embodiment (Example 2) of the present invention. The receiving terminal 2-2 includes a CID identification unit 51, a type identification unit 52, an application unit 21-2, a CID / header information storage and CID response unit (CID identification unit) 22, a filter unit 24, and a payload extraction unit 25. ing.

  The CID identifying unit 51 and the type identifying unit 52 have the same functions as the CID identifying unit 51 and the type identifying unit 52 shown in FIG. The application unit 21-2 specifies an IP address (source IP address and destination IP address) and a destination port number, and acquires a desired datagram.

  The CID / header information storage and CID response unit 22 associates the CID from the CID identification unit 51 with the header information from the type identification unit 52, like the CID / header information storage unit 53 shown in FIG. As shown in FIG. 11, a CID record is generated and stored in the CID table. Further, the CID / header information storage and CID response unit 22 searches the CID table using the IP address (source IP address and destination IP address) and the destination port number, and specifies the CID.

  The filter unit 24 performs filtering for selecting only packets having the CID specified by the CID / header information storage and CID response unit 22. The payload extraction unit 25 extracts a datagram from the payload of the packet selected by the filter unit 24.

  Next, processing of the receiving terminal 2-2 illustrated in FIG. 3 will be described. FIG. 4 is a flowchart for explaining processing of the receiving terminal 2-2 according to the second embodiment. First, the application unit 21-2 specifies an IP address (source IP address and destination IP address) and a destination port number to be added to a datagram packet to be acquired in order to acquire a desired datagram, and a filter unit In 24, a reception control start command for starting filtering is output to the CID / header information storage and CID response unit 22. The reception control start command is output to the filter unit 24 via the CID / header information storage and CID response unit 22, and the filter unit 24 starts reception control by filtering (steps S41 and S42).

  The CID / header information storage and CID response unit 22 receives an instruction to start reception control including the IP address (source IP address and destination IP address) and destination port number from the application unit 21-2, and searches the CID table. A CID record having the same data as the IP address (source IP address and destination IP address) and destination port number is read from the CID table, and the CID is specified (step S43). The CID table stores CID records in which CIDs are associated with header information including IP addresses (source IP address and destination IP address) and destination port numbers. The response unit 22 can specify the CID based on the IP address (source IP address and destination IP address) and the destination port number. Then, the CID / header information storage and CID response unit 22 issues a reception control start command including the specified CID to start reception control including the input IP address (source IP address and destination IP address) and destination port number. It outputs to the filter part 24 as a response of a command.

  The filter unit 24 receives an instruction to start reception control including the CID from the CID / header information storage and CID response unit 22, selects only the header compressed packet having the CID, and performs filtering (step S44). Since the CID is an identifier specified by the IP address (source IP address and destination IP address) specified by the application unit 21-2 and the destination port number, the header compression with the datagram desired by the application unit 21-2 Only the packet is selected by the filter unit 24. The filter unit 24 outputs the selected header compressed packet to the payload extraction unit 25.

  The payload extraction unit 25 receives the header compressed packet from the filter unit 24, extracts a datagram from the payload, and outputs the datagram to the application unit 21-2 (step S45).

  The application unit 21-2 inputs a datagram from the payload extraction unit 25. Thereby, the application unit 21-2 can obtain a desired datagram corresponding to the designated IP address (source IP address and destination IP address) and destination port number (step S46).

  The application unit 21-2 specifies an IP address (source IP address and destination IP address) and a destination port number for which reception control is performed in order to end acquisition of a desired datagram, and the filtering unit 24 performs filtering. Is output to the CID / header information storage and CID response unit 22. The reception control end command is output to the filter unit 24 via the CID / header information storage and CID response unit 22, and the reception control by filtering ends in the filter unit 24 (step S47). In this case, the CID / header information storage and CID response unit 22 inputs the IP address (source IP address and destination IP address) and destination port number from the application unit 21-2, and searches the CID table to identify the CID. Then, a command to end reception control including the specified CID is output to the filter unit 24. Thereby, the application unit 21-2 can stop inputting the datagram corresponding to the designated IP address (source IP address and destination IP address) and destination port number.

  As described above, according to the receiving terminal 2-2 of the second embodiment, the CID / header information storage and CID response unit 22 sets the designated IP address (source IP address and destination IP address) and destination port number. The CID is specified, the filter unit 24 selects a desired header compressed packet based on the CID, and the payload extraction unit 25 extracts the datagram from the desired header compressed packet. As a result, the application unit 21-2 can acquire a desired datagram corresponding to the designated IP address (source IP address and destination IP address) and destination port number. Accordingly, the receiving terminal 2-2 can acquire a desired datagram without restoring the header information of the received header compressed packet to the original IP header information, and thus the processing load is reduced with a simple configuration. It becomes possible to do. In addition, since the processing load is reduced, reception at a high packet rate is possible.

  Further, according to the receiving terminal 2-2 of the second embodiment, the CID / header information storage and CID response unit 22 inputs the CID record in which the CID and the header information are associated with each other in the CID table. The CID is specified by referring to the CID table using the IP address (source IP address and destination IP address) and destination port number. Thus, as in the first embodiment, the CID table stores the CID record in which the CID and the header information are associated with each other, and the CID and the IP data flow are associated with each other using the header information of the full header packet. The operation of the CID is the same as in the prior art and is not restricted.

  Further, according to the receiving terminal 2-2 of the second embodiment, the application unit 21-2 specifies an IP address (source IP address and destination IP address) and a destination port number, and acquires a desired datagram. Therefore, the destination port number can be freely specified as compared with the first embodiment in which only the IP address (source IP address and destination IP address) is specified. Therefore, in the first embodiment, a plurality of datagrams are acquired, while in the second embodiment, a desired one datagram can be acquired.

Example 3
The third embodiment refers to the fixed CID table using the IP address (source IP address and destination IP address) and destination port number without restoring the header information of the received packet to the original IP header information. A desired packet is selected, and a desired datagram is acquired from the payload of the selected packet. In the second embodiment, a CID record in which CID and header information are associated with each other is generated and stored in the CID table. In the third embodiment, a fixed CID table including a preset CID record is used. That is, in the third embodiment, the association between the IP header information for specifying the IP data flow and the CID is fixedly used.

  FIG. 5 is a block diagram showing a configuration of a receiving terminal according to the embodiment (Example 3) of the present invention. The receiving terminal 2-3 includes an application unit 21-3, a CID / header information correspondence table unit (CID identification unit) 26, a filter unit 24, and a payload extraction unit 25.

  In the third embodiment, the CID identifying unit 51 and the type identifying unit 52 of the first and second embodiments illustrated in FIGS. 1 and 3 are not provided. The application unit 21-3 specifies an IP address (source IP address and destination IP address) and a destination port number, and acquires a desired datagram.

  The CID / header information correspondence table unit 26 includes a preset CID table in a storage medium such as a nonvolatile memory. As shown in FIG. 11, the CID table includes header information such as a CID and an IP address (source IP address and destination IP address).

  Note that the CID table does not have to be configured to include all of the header information shown in FIG. 11, and includes, for example, only the CID, IP address (source IP address and destination IP address), and destination port number. It may be configured. When the application unit 21-3 designates only the destination IP address and the destination port number, the application unit 21-3 may be configured to include only the CID, the destination IP address, and the destination port number. The transmission source port number may also be provided. In this case, it is only necessary to have at least a CID, a destination IP address, and a destination port number.

  The CID / header information correspondence table unit 26 inputs a reception control start command including an IP address (source IP address and destination IP address) and a destination port number from the application unit 21-3, and receives an IP address (source IP address). And the destination IP address) and the destination port number are searched to identify the CID.

  The filter unit 24 performs filtering for selecting only packets having the CID specified by the CID / header information correspondence table unit 26. The payload extraction unit 25 extracts a datagram from the payload of the packet selected by the filter unit 24.

  The processing of the receiving terminal 2-3 shown in FIG. 5 is the same as the processing shown in FIG.

  As described above, according to the receiving terminal 2-3 of the third embodiment, the CID / header information correspondence table unit 26 uses the designated IP address (source IP address and destination IP address) and destination port number. The CID is specified with reference to the fixed CID table, the filter unit 24 selects a desired header compressed packet based on the CID, and the payload extraction unit 25 extracts the datagram from the desired header compressed packet. Thereby, even when the CID table in which the CID and the header information are associated with each other is fixedly operated, the application unit 21-3 specifies the specified IP address (source IP address and destination IP address) and destination port number. A desired datagram corresponding to can be acquired. Therefore, the receiving terminal 2-3 can acquire a desired datagram without restoring the header information of the received header compressed packet to the original IP header information, so the processing load is reduced with a simple configuration. It becomes possible to do. In addition, since the processing load is reduced, reception at a high packet rate is possible.

  In the third embodiment, since the fixed operation is performed using the preset CID table, the transmission terminal 1 does not need to transmit a full header packet for associating the CID with the header information. The receiving terminal 2-3 does not need to include the CID identifying unit 51 and the type identifying unit 52. As a result, the receiving terminal 2-3 can omit the processing of CID identification and type identification in addition to omitting the restoration processing of the IP header information, so that the processing load can be further reduced.

Example 4
In the fourth embodiment, a desired packet is selected based on the designated CID without restoring the header information of the received packet to the original IP header information, and a desired datagram is acquired from the payload of the selected packet. In the first to third embodiments, the CID is obtained by referring to the CID table using the specified IP address (source IP address and destination IP address), or IP address (source IP address and destination IP address) and destination port number. In the fourth embodiment, the CID is directly specified.

  FIG. 6 is a block diagram showing a configuration of a receiving terminal according to the embodiment (Example 4) of the present invention. The receiving terminal 2-4 includes an application unit (CID designation unit) 21-4, a filter unit 24, and a payload extraction unit 25.

  In the fourth embodiment, the CID identifying unit 51 and the type identifying unit 52 of the first and second embodiments shown in FIGS. 1 and 3 are not provided, and the CIDs of the first and second embodiments shown in FIGS. The header information storage and CID response unit 22 and the CID / header information correspondence table unit 26 of the third embodiment shown in FIG. 5 are not provided.

  The application unit 21-4 acquires a CID corresponding to a desired datagram from download control information (DCI: Download Control Information) described later, and acquires the datagram by specifying the CID.

  The filter unit 24 performs filtering for selecting only packets having the CID specified by the application unit 21-4. The payload extraction unit 25 extracts a datagram from the payload of the packet selected by the filter unit 24.

  Here, the download control information generally includes location information (link information: for example, service ID corresponding to a channel of a broadcasting station), content distribution start time, and distribution end time. , Content ID, license ID, location information of ECG (Electronic Content Guide) metadata, etc., and is used for downloading and viewing or recording the content.

  As described above, the transmission terminal 1 of the broadcasting station specifies an IP data flow for the IP packet of the content to be transmitted, specifies the CID, and generates a CID table including the CID and header information. Then, the transmission terminal 1 stores the header compressed packet to which the compressed header information including the CID is added in the TLV and transmits the packet via the one-way transmission path 3. At this time, the transmission terminal 1 also stores download control information related to content transmitted within a predetermined period in the TLV at a predetermined cycle by the carousel process, and transmits it in advance. Prior to transmission of the header compressed packet, the transmission terminal 1 transmits the specified CID described in the download control information. That is, the transmission terminal 1 specifies the CID in advance prior to transmitting the header compressed packet of the content to be transmitted. Then, the transmission terminal 1 describes the specified CID in the download control information in addition to various information related to the content to be transmitted, and transmits the download control information in a predetermined cycle by the carousel process. When the receiving terminal 2-4 receives the download control information, the application unit 21-4 acquires the CID corresponding to the desired datagram content from the download control information, and acquires the datagram by specifying the CID. To do.

  Next, processing of the reception terminal 2-4 illustrated in FIG. 6 will be described. FIG. 7 is a flowchart for explaining processing of the reception terminal 2-4 according to the fourth embodiment. First, the application unit 21-4 acquires the CID corresponding to the content of the desired datagram from the download control information (step S71). For example, the application unit 21-4 specifies the ID (content ID) of the content selected by the operator according to the operation of the operator, and acquires the CID corresponding to the content ID from the download control information.

  The application unit 21-4 designates the acquired CID, and outputs a reception control start command for starting filtering to the filter unit 24. Thereby, reception control by filtering is started in the filter unit 24 (steps S72 and 73).

  The filter unit 24 inputs a reception control start command including the CID from the application unit 21-4, selects only the header compressed packet having the CID, and performs filtering (step S74). Since the CID is an identifier corresponding to the datagram desired by the application unit 21-4, only the header compressed packet having the datagram desired by the application unit 21-4 is selected by the filter unit 24. Then, the filter unit 24 outputs the selected header compressed packet to the payload extraction unit 25.

  The payload extraction unit 25 receives the header compressed packet from the filter unit 24, extracts a datagram from the payload, and outputs the datagram to the application unit 21-4 (step S75).

  The application unit 21-4 inputs a datagram from the payload extraction unit 25. Thereby, the application part 21-4 can acquire the desired datagram corresponding to the designated CID (step S76).

  The application unit 21-4 specifies the CID for which reception control is performed in order to end acquisition of a desired datagram, and outputs a reception control end command for stopping filtering to the filter unit 24. The filter unit 24 inputs a reception control end command, and the reception control by filtering ends (step S77). Thereby, the application part 21-4 can stop the input of the datagram corresponding to the designated CID.

  As described above, according to the fourth embodiment, the transmission terminal 1 transmits the download control information describing the CID, and the application unit 21-4 of the reception terminal 2-4 acquires the CID included in the download control information. Then, a CID is specified to obtain a desired datagram, the filter unit 24 selects a desired header compressed packet based on the CID specified by the application unit 21-4, and the payload extraction unit 25 selects a desired header. The datagram was extracted from the compressed packet. Thereby, the application part 21-4 can acquire the desired datagram corresponding to the designated CID. Therefore, the receiving terminal 2-4 can obtain a desired datagram without restoring the header information of the received header compressed packet to the original IP header information, so that the processing load is reduced with a simple configuration. It becomes possible to do. In addition, since the processing load is reduced, reception at a high packet rate is possible.

  Further, in the fourth embodiment, since the CID table is unnecessary, the transmission terminal 1 does not need to transmit a full header packet for associating the CID and the header information, and the reception terminal 2-4 includes the CID identification unit 51 The type identification unit 52 and the CID / header information storage and CID response unit 22 or the CID / header information correspondence table unit 26 need not be provided. As a result, the receiving terminal 2-4 can omit the CID identification and type identification processes in addition to omitting the IP header information restoration process, and can also omit the process for the CID table. Can be further reduced.

  The present invention has been described with reference to the embodiments. However, the present invention is not limited to the above-described embodiments, and various modifications can be made without departing from the technical idea thereof. For example, in the first to third embodiments, the transmission source IP address and the destination IP address are designated as the IP address, but only the destination IP address may be designated. In this case, in the first embodiment, the CID / header information storage and CID response unit 22 searches the CID table using the destination IP address specified by the application unit 21-1, and specifies the CID. Similarly, in the second embodiment, the CID / header information storage and CID response unit 22 searches the CID table using the destination IP address and the destination port number specified by the application unit 21-2, and specifies the CID. Furthermore, in the third embodiment, the CID / header information correspondence table unit 26 searches the CID table using the destination IP address and the destination port number specified by the application unit 21-3, and specifies the CID.

  In the fourth embodiment, the transmission terminal 1 describes the specified CID in the download control information, transmits the download control information via the one-way transmission path 3 at a predetermined cycle by the carousel process, and receives the reception terminal. 2-4 receives the download control information via the one-way transmission path 3 and acquires the CID. However, the present invention does not limit the method for receiving the download control information, and the download control information may be received via a communication line such as the Internet. Specifically, for example, it is assumed that download control information is stored in a server in a broadcast station. The application unit 21-4 of the receiving terminal 2-4 receives the download control information related to the selected and operated content according to the selection operation of the content that the user wants to view or record. Send to the server in the broadcasting station. When receiving the request, the server in the broadcast station transfers the request to the transmission terminal 1 and receives from the transmission terminal 1 the CID specified for the content indicated by the request. Then, the server reads the download control information related to the content indicated by the request from the storage device, describes the CID received from the transmission terminal 1, and transmits it to the reception terminal 2-4 via the communication line. In this way, the application unit 21-4 of the receiving terminal 2-4 receives the download control information in which the CID is described via a communication line such as the Internet.

It is a block diagram which shows the structure of the receiving terminal by embodiment (Example 1) of this invention. FIG. 6 is a flowchart for explaining processing of the first embodiment. It is a block diagram which shows the structure of the receiving terminal by embodiment (Example 2) of this invention. It is a flowchart explaining the process of Example 2,3. It is a block diagram which shows the structure of the receiving terminal by embodiment (Example 3) of this invention. It is a block diagram which shows the structure of the receiving terminal by embodiment (Example 4) of this invention. FIG. 10 is a flowchart for explaining processing of the fourth embodiment. It is a figure which shows schematic structure of the transmission system containing the transmission terminal and receiving terminal which implement | achieve advanced BS digital broadcasting. It is a figure explaining the header compression system which compresses header information in a transmission terminal, and decompress | restores header information in a reception terminal. It is a block diagram which shows the structure of the conventional receiving terminal and application apparatus. (1) is a diagram showing a configuration of an IPv4 CID table. (2) is a diagram showing the configuration of an IPv6 CID table. (1) is a diagram showing a configuration of an IPv4 full header packet. (2) is a diagram showing a configuration of an IPv4 compressed header packet. (3) is a diagram illustrating a configuration of an IPv6 full header packet. (4) is a diagram showing a configuration of an IPv6 compressed header packet. It is a figure which shows the structure of IPv4_header_wo_length in the full header packet of IPv4. It is a figure which shows the structure of IPv6_header_wo_length in the full header packet of IPv6. It is a figure which shows the structure of UDP_header_wo_length in the full header packet of IPv4 and IPv6.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Transmission terminal 2 Reception terminal 3 Unidirectional transmission line 4 Application apparatus 21 Application part 22 CID / header information storage and CID response part 23 IGMP / MLD processing part 24, 55 Filter part 25, 56 Payload extraction part 26 CID / header information correspondence Table unit 51 CID identification unit 52 Type identification unit 53 CID / header information storage unit 54 Header restoration unit

Claims (5)

Under a transmission system in which an IP data flow of content to be transmitted is determined by an IP address and a port number, a header including a context identifier (CID) for identifying the IP data flow is added, and the packet is transmitted as a header compressed packet Receiving a header-compressed packet and obtaining a datagram of a predetermined content from the packet;
A CID identifying unit for identifying a CID from the header of the received packet;
Identifying a header type from the received packet, and if the identified header type is a type that includes an IP address in the header, a type identifying unit that extracts an IP address from the header of the packet;
A CID table configured by a CID record including the CID identified by the CID identification unit and the IP address extracted by the type identification unit;
A CID specifying unit that searches the CID table based on an IP address designated to obtain a datagram of the predetermined content, and specifies a CID from a CID record including the IP address;
A filter unit for selecting a packet having the CID specified by the CID specifying unit from the received packets;
A receiving terminal comprising: a payload extracting unit that extracts a datagram of content from a payload of a packet selected by the filter unit. The receiving terminal according to claim 1,
The CID specifying unit specifies a plurality of CIDs,
The filter unit selects, for each CID, a packet having any one of the plurality of CIDs specified by the CID specifying unit from the received packets.
The receiving terminal, wherein for each packet of each CID selected by the filter unit, a content datagram is extracted from the payload of the packet. The receiving terminal according to claim 1,
The type identifying unit identifies a header type from the received packet, and when the identified header type is a type including an IP address and a port number in the header, extracts the IP address and the port number from the header of the packet,
The CID table is configured by a CID record including a CID identified by the CID identification unit and an IP address and a port number extracted by the type identification unit,
The CID specifying unit searches the CID table based on an IP address and a port number designated for acquiring a datagram of the predetermined content, and specifies a CID from a CID record including the IP address and the port number. A receiving terminal characterized by: Under a transmission system in which an IP data flow of content to be transmitted is determined by an IP address and a port number, a header including a context identifier (CID) for identifying the IP data flow is added, and the packet is transmitted as a header compressed packet Receiving a header-compressed packet and obtaining a datagram of a predetermined content from the packet;
A CID table configured by a CID record including a preset CID, IP address, and port number;
A CID specifying unit that searches the CID table based on an IP address designated to obtain a datagram of the predetermined content, and specifies a CID from a CID record including the IP address;
A filter unit for selecting a packet having the CID specified by the CID specifying unit from the received packets;
A receiving terminal comprising: a payload extracting unit that extracts a datagram of content from a payload of a packet selected by the filter unit. An IP data flow of content to be transmitted is determined by an IP address and a port number, a header including a context identifier (CID) for specifying the IP data flow is added, and the packet is transmitted as a header compressed packet. The download control information including the location information, the distribution start time and distribution end time of the content, and the content ID is described in the CID, and the download control information is transmitted prior to transmission of the header-compressed packet. A receiving terminal that receives the download control information and a header-compressed packet under a transmission system and obtains a datagram of a predetermined content from the packet.
A CID designating unit for designating a CID described in the download control information as a CID for obtaining a datagram of the predetermined content;
A filter unit for selecting a packet having a CID designated by the CID designation unit from the received packets;
A receiving terminal comprising: a payload extracting unit that extracts a datagram of content from a payload of a packet selected by the filter unit.

Images