JP2007043678A - Communication terminal and communication method - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To achieve a multiform enabled transport protocol for performing control similar to an ordinary TCP without using any header other than an ordinary TCP header. <P>SOLUTION: A communication terminal 10 includes: a path information manager unit 12 for managing TCP control information related to each of a plurality of paths; a transmission segment manager unit 11 for storing segments generated by dividing data to be transmitted; and a segment transmitter unit 13 for extracting a segment from the transmission segment manager unit 11 and transmitting the extracted segment to a receiving terminal 30. The transmission segment manager unit 11 makes a reservation for the transmission of the segment based on the TCP control information by storing the segment in association with a path used for the transmission of the segment, and the segment transmitter unit 13 extracts only a segment from the transmission segment manager unit 11 and transmits the extracted segment to the receiving terminal along a path associated with the segment. <P>COPYRIGHT: (C)2007,JPO&INPIT

Description

  The present invention relates to a communication method in which a transmission terminal transmits data to a reception terminal using a plurality of paths simultaneously, and a communication terminal that implements the communication method.

Conventionally, as a communication method using a multi-home compatible transport protocol (Multi-Path TCP (Transmission Control Protocol)), that is, a communication method in which a transmitting terminal transmits data to a receiving terminal using a plurality of paths simultaneously, Techniques described in Patent Documents 1 to 3 are known.
RFC 2960, “SCTP (Stream Control Transmission Protocol)” “A transport layer approfor for improving end-to-end perforance and Robustness using redundant paths.”, 2004. “A transport layer approach for aggregating bandwidth on multi-homed mobile hosts.” Hung-Yun Heleh, Raghupathy Momon, 2002

  However, the communication method using the multihome-compatible transport protocol proposed in Non-Patent Document 1 performs communication using only one path having the best communication state, and uses other paths as detour paths at the time of failure. Since it is configured to use, there is a problem that communication cannot be performed using a plurality of paths simultaneously.

  On the other hand, the technologies proposed in Non-Patent Documents 2 and 3 can perform communication by simultaneously using a plurality of paths existing between the transmission terminal and the reception terminal.

  However, since the technique proposed in Non-Patent Document 2 requires a new header above the normal TCP header, communication with a communication terminal not equipped with the protocol proposed in Non-Patent Document 2 There was a problem that it was not possible to communicate with.

  In this regard, in the technology proposed in Non-Patent Document 3, communication is performed by using only a normal TCP header and simultaneously using a plurality of paths existing between a transmitting terminal and a receiving terminal (that is, Multi-home connection).

  However, in the technique proposed in Non-Patent Document 3, only one path (ACK path) for transmitting an ACK (Acknowledgement signal) can be used, so a failure occurs in the ACK path being used. Then, all the paths are affected, and each path is asymmetric (the path that transmitted the packet is different from the path that receives the ACK), so that the RTT (Round Trip Time) is not accurately measured. there were.

  Furthermore, the technique proposed in Non-Patent Document 3 has a problem that C-ACK (Cumulative ACK) cannot be used, and it is impossible to perform control equivalent to normal TCP on a path basis. There was a problem.

  The present invention has been made in view of the above points. In order to enable communication even with a receiving terminal to which the technology according to the present invention is not applied, a header other than a normal TCP header is used. Without using it, it is possible to perform the same control as normal TCP by measuring accurate RTT using a symmetric path by using multiple ACK paths and improving Cumulative ACK An object of the present invention is to provide a communication method and a communication terminal for realizing a transport protocol.

  A first feature of the present invention is a communication terminal capable of transmitting data to a receiving terminal using a plurality of paths simultaneously, and configured to manage TCP control information related to each of the plurality of paths. A path information management unit, a transmission segment management unit configured to store a segment generated by dividing data to be transmitted to the receiving terminal, and extracting the segment from the transmission segment management unit A segment transmission unit configured to transmit to the receiving terminal, and the transmission segment management unit, based on the TCP control information, determines the segment and a path used for transmission of the segment. The segment transmission unit is configured to perform transmission reservation for the segment by associating and storing the segment, and the segment transmission unit includes the transmission segment. From processing section extracts only the segment, and summarized in that via the path associated with the segment is configured to transmit the segment to the receiving terminal.

  According to this invention, since the segment is transmitted using only a normal TCP header, communication can be performed even with a receiving terminal to which the technology according to the present invention is not applied. It can be performed.

  1st characteristic of this invention WHEREIN: When the delivery confirmation signal which concerns on the said segment is received via the path | pass same as the path | pass used for transmission of this segment, it is delivered in all the transmission segment management parts. A segment reception unit configured to delete from the transmission segment management unit a segment having a sequence number smaller than the minimum sequence number of a segment that has not received a confirmation signal may be provided.

  In the first aspect of the present invention, when the transmission segment management unit detects a timeout, the transmission segment management unit cancels the transmission reservation for all the segments that have not received the delivery confirmation signal, and again, based on the TCP control information, You may be comprised so that the transmission reservation with respect to a segment may be performed.

  In the first aspect of the present invention, the transmission segment management unit receives a delivery confirmation signal between the largest segment that has received the selective delivery confirmation signal and the next segment that should receive the delivery confirmation signal. If there are more than a certain number of segments, cancel transmission reservations for segments that have not received a delivery confirmation signal with a sequence number equal to or less than the sequence number of the largest segment that has received the selective delivery confirmation signal, and unsent segments, and again The transmission reservation for the segment may be performed based on the TCP control information.

  In the first aspect of the present invention, the segment transmission unit may be configured to form an ad hoc network with a neighboring communication terminal and transmit the segment via the path in the ad hoc network. Good.

  According to this invention, by using a path in an ad hoc network formed with neighboring communication terminals, a plurality of communication terminals that do not have a plurality of interfaces exist between a transmission terminal and a reception terminal. It is possible to realize communication (that is, virtual multi-home connection) by simultaneously using these paths.

  A second feature of the present invention is a communication terminal capable of receiving data from a transmission terminal using a plurality of paths simultaneously, and configured to manage TCP control information related to each of the plurality of paths. A path information management unit, a segment reception unit configured to receive a segment generated by dividing the data via the plurality of paths, and the segment received by the segment. A reception segment management unit configured to store for each path, and a transmission confirmation signal for notifying a reception result of the segment through each path based on the TCP control information. And a segment transmission unit.

  In the second aspect of the present invention, the delivery confirmation signal may be configured to notify a sequence number of a segment successfully received via the path.

  According to this invention, since it is configured to transmit an ACK to the path that received the packet, it is possible to accurately measure the RTT, and to improve the C-ACK, The same control as the TCP control can be performed.

  In the second aspect of the present invention, when a plurality of segments having consecutive sequence numbers are received through the same path, the delivery confirmation signal collectively notifies the reception results of the plurality of segments. It may be configured.

  According to this invention, since a plurality of ACKs (acknowledgment confirmation signals) can be transmitted (for example, C-ACK can be used), the number of ACKs to be transmitted can be reduced.

  In the second aspect of the present invention, the segment receiving unit may be configured to form an ad hoc network with a neighboring communication terminal and receive the segment via the path in the ad hoc network. Good.

  A third feature of the present invention is a communication method in which a transmission terminal uses a plurality of paths simultaneously to transmit data to a reception terminal, and the transmission terminal is managed for each of the plurality of paths. Based on the control information, the segment generated by dividing the data to be transmitted to the receiving terminal and the path used for transmitting the segment are associated with each other and stored in the transmission segment management unit. A step of performing transmission reservation, a step in which the transmission terminal extracts only the segment from the transmission segment management unit, and transmits the segment to the reception terminal via a path associated with the segment; The receiving terminal manages the received segment for each path through which the segment is transmitted, and is managed for each of the plurality of paths. A step of transmitting a delivery confirmation signal for notifying the reception result of the segment via each path based on the TCP control information, and the transmission terminal sends a delivery confirmation signal related to the segment to the transmission of the segment. And a step of deleting the segment and the path associated with the segment from the transmission segment management unit when received via the same path as the used path.

  In the third aspect of the present invention, the transmitting terminal and the receiving terminal have a step of forming an ad hoc network with a neighboring communication terminal, and the transmitting terminal transmits the generated segment to the ad hoc network. May be transmitted to the receiving terminal via the path, and the receiving terminal may receive the segment via the path in the ad hoc network.

  As described above, according to the present invention, a communication method and a communication terminal for realizing a multihomed transport protocol capable of performing the same control as normal TCP without using a header other than the normal TCP header. Can be provided.

(Configuration of communication terminal according to the first embodiment of the present invention)
FIG. 1 shows an example of a communication system including communication terminals (transmission terminal 10 and reception terminal 30) according to the first embodiment of the present invention. As shown in FIG. 1, in the present embodiment, an environment is assumed in which data is transmitted from the transmission terminal 10 to the reception terminal 30 using the three paths # 1 to # 3 simultaneously.

  As such data, applications such as FTP (File Transfer Protocol), SMTP (Simple Mail Transfer Protocol), HTTP (Hyper Text Transfer Protocol), and POP3 (Post Office Protocol Version 3) are assumed.

  In addition, such data can be applied in a database language such as SQL (Structured Query Language), and can be applied in a file access over a network such as NFS (Network File System), such as SSH (Secure Shell) or SSL (Secure The present invention can be applied to any communication using TCP such as VPN (Virtual Private Network) such as Socket Layer) and Ethernet (registered trademark) over TCP / IP.

  As shown in FIG. 1, a receiving terminal 30 according to the present embodiment includes a 3G-compatible interface in a WAN (Wireless Area Network), an IEEE802.11b-compatible interface in a WLAN (Wireless Local Area Network), and a WPAN (Wireless Person). It is configured to have a plurality of wireless interfaces (compatible with multi-home connection) such as an interface compatible with Bluetooth (registered trademark) in Area Network.

  The receiving terminal 30 according to the present embodiment is configured to receive data transmitted from the transmitting terminal 10 by simultaneously using a plurality of paths # 1 to # 3 established by a plurality of interfaces.

  On the other hand, in the example of FIG. 1, the transmission terminal 10 according to the present embodiment includes only a wired interface and does not include a plurality of wireless interfaces.

  However, in normal TCP, a path (a general TCP connection) is determined by four addresses: [(IP address of sender, port number), (IP address of recipient, port number)].

  Therefore, the transmission terminal 10 according to the present embodiment also needs to transmit the data (the segment constituting the) to the reception terminal 30 by using the plurality of paths # 1 to # 3 simultaneously. 1 to # 3 can be discriminated (corresponding to multihome connection).

  As shown in FIG. 2, the transmission terminal 10 according to the present embodiment includes an application function unit 10a, a transmission segment management unit 11, a path information management unit 12, a segment transmission unit 13, and a segment reception unit 14. is doing.

  The application function unit 10a instructs the transmission segment management unit 11 to transmit data used in the application.

  Here, the application function unit 10a may be configured to be able to explicitly specify a set of a plurality of paths as a path for transmitting data.

  Further, the application function unit 10a may be configured to designate a representative path as a path for transmitting data and to automatically add other paths.

  The transmission segment management unit 11 includes a transmission buffer that stores segments generated by dividing data to be transmitted to the receiving terminal 30.

  In addition, the transmission segment management unit 11 generates a segment generated based on TCP control information managed by “TCP-CB: TCP Control Block” for each path, and a path (variable “ path ") is stored in association with each other, thereby making a transmission reservation for the segment.

  Specifically, as shown in FIG. 3, the transmission segment management unit 11 divides the data to be transmitted to the receiving terminal 30 passed from the application function unit 10 a into PDU (Protocol Data Unit) units. A segment is formed by adding a normal TCP header to the data. Here, the TCP header is assumed to be a TCP header used in normal TCP.

  Moreover, the transmission segment management part 11 is comprised so that the special header for managing the said segment may be provided and managed with respect to the formed said segment.

  As shown in FIG. 3, the special header is configured to include variables such as “path”, “sack”, “p_seq”, “next”, and flags such as “rsv” flag.

  Here, the variable “p_seq” indicates the sequence number of the segment allocated for each path.

  In TCP, the sequence number is generally expressed in “byte order”, but in this specification, it is expressed in “sequence order” for the sake of simplicity.

  The variable “path” indicates identification information of a path used for transmission of the segment, and the variable “sack” indicates identification information of a path used for reception of an ACK for the segment. The variable “next” indicates a segment to be referred to next to the segment.

  The “rsv” flag is a flag indicating a state in which transmission reservation for the segment is performed (“1” in this state).

  Further, the transmission segment management unit 11 manages a variable “rsv_nxt” indicating the data start position to be reserved next.

  If the transmission segment management unit 11 detects a timeout, the transmission segment management unit 11 cancels transmission reservations for all segments that have not received ACK (acknowledgement signal), and again, based on TCP-CB (TCP control information), It is configured to make a transmission reservation for the segment.

  In addition, the transmission segment management unit 11 includes a maximum segment (“max_sack”) that has received the SACK block (selective acknowledgment signal) and a segment (“rcv_nxt”) that is to receive the next ACK (delivery acknowledgment signal). If there are more than a predetermined number (for example, 3) of segments that have not received ACK (acknowledgment acknowledgment signal) in the meantime, the sequence number is equal to or less than the sequence number of the largest segment that has received the SACK block (selective acknowledgment signal) It is configured to cancel transmission reservations for segments that have not received an ACK (acknowledgement signal) and untransmitted segments, and make transmission reservations for the segments again based on TCP-CB (TCP control information). ing.

  The path information management unit 12 is configured to manage TCP-CB (TCP control information) related to each of the plurality of paths # 1 to # 3 by the plurality of path information management units # 1 to # 3. Each path is identified by four addresses, [(IP address of sender, port number), (IP address of recipient, port number)].

  Specifically, as illustrated in FIG. 4, each path information management unit #n performs “rtt”, “t_timer”, “t_seq”, “cwnd”, “ssthresh”, “rcv_nxt”, “snd_nxt”, “ It is configured to manage TCP-CB (n) including variables such as “rsv_num”, “snd_num”, and “max_sack”.

  In addition, various information for maintaining a TCP connection such as “t_state” and “t_flags” may be secured in the TCP-CB (n).

  Here, “rtt” is a measured round trip time, “t_timer” is a timeout value calculated based on “rtt”, and “t_seq” is a segment used for measuring “rtt”. "Cwnd" is a congestion window, "ssthresh" is "Slow Start Threshold", "rcv_nxt" is the sequence number of the segment that is expected to be received next, and "snd_nxt" Is a sequence number of a segment to be transmitted next, “rsv_num” is a reserved data amount, “snd_num” is a transmitted data amount, and “max_sack” is transmitted through the path. Notify by ACK or SACK option in segment Is the largest sequence number assigned.

  The segment transmission unit 13 is configured to extract a segment from the transmission segment management unit 11 and transmit the segment to the receiving terminal 30 via a path associated with the segment.

  Moreover, the segment transmission part 13 is comprised so that it may retransmit about the said segment, when the loss of a specific segment is detected.

  When the ACK (acknowledgment confirmation signal) related to the segment is received via the same path as the path used for transmitting the segment, the segment receiving unit 14 A segment having a sequence number smaller than the minimum sequence number of a segment that has not received (delivery confirmation signal) is deleted from the transmission segment management unit 11.

  As shown in FIG. 5, the receiving terminal 30 according to the present embodiment includes an application function unit 30a, a segment receiving unit 31, a path information managing unit 32, a receiving segment managing unit 33, and a segment transmitting unit 34. is doing.

  The segment receiving unit 31 receives segments from the transmitting terminal 10 via a plurality of paths # 1 to # 3, and selects each of the received segments [(sender's IP address, port number), (receiver's IP address , Port number)]] to the specific path information management units # 1 to # 3.

  The path information management unit 32 is configured to manage TCP-CB (TCP control information) related to each of the plurality of paths # 1 to # 3 by the plurality of path information management units # 1 to # 3. Each path is identified by four addresses, [(IP address of sender, port number), (IP address of recipient, port number)].

  Specifically, each path information management unit #n includes a TCP including variables such as “del_timer”, “del_ack”, “rcv_nxt”, “p_sack1”, “p_sack2”, “p_sack3”, etc., as shown in FIG. -It is configured to manage CB (n).

  In addition, various information for maintaining the TCP connection may be secured in the TCP-CB (n).

  Here, “del_timer” is a timer for delaying transmission of ACK, “del_ack” is a sequence number used for ACK when “del_timer” expires, and “rcv_nxt” is expected to be received next. This is the sequence number of the segment, and “p_sackn” is the sequence number entered in the nth block.

  The reception segment management unit 33 is configured to manage the received segment for each path through which the segment is transmitted.

  Specifically, as shown in FIG. 7, the reception segment management unit 33 manages each segment transmitted from the path information management unit 12 by adding a special header for managing the segment. The reception buffer is configured as described above.

  The special header is configured to include a variable such as “path” as shown in FIG.

  Here, the variable “path” indicates identification information of a path used for transmission of the segment.

  Further, the reception segment management unit 33 manages a variable “rcv_buf_first” indicating the start position where the first received segment is stored.

  The reception segment management unit 33 is configured to transmit from the segment indicated by the variable “rcv_buf_first” to the application function unit 30a.

  Based on TCP-CB (TCP control information) managed for each path, the segment transmission unit 34 transmits an ACK (delivery confirmation signal) for notifying the reception result of the segment via each path. It is configured.

  Note that, as will be described later, a SACK (Selective Acknowledgment) option defined in RFC2018 is given to the ACK.

  Here, the SACK option given to ACK is configured to notify the sequence number of the segment successfully received via each path.

  Further, when a plurality of segments having consecutive sequence numbers are received in the same path, the segment transmission unit 34 transmits a delivery confirmation signal (C-ACK) for collectively reporting the reception results of the plurality of segments. It may be configured to.

(Operation of the communication terminal according to the first embodiment of the present invention)
The operation of the communication terminal according to the first embodiment of the present invention will be described below with reference to FIGS.

  First, with reference to FIG. 8 and FIG. 9, an operation in which the transmission terminal 10 according to the present embodiment transmits data to the reception terminal 30 using a plurality of paths # 1 to # 3 simultaneously will be described.

  As shown in FIG. 8, in step S101, the transmission segment management unit 11 of the transmission terminal 10 divides the data passed from the application function unit 10a into MTU units.

  In step S102, the transmission segment management unit 11 forms a segment by adding a TCP header to each piece of data divided in MTU units, and manages the data by adding the above-described special header (see FIG. 3).

  Here, the transmission segment management unit 11 sets “0” as an initial value in each variable and flag.

  In step S103, the transmission segment management unit 11 monitors the variable “rsv_num” in the TCP-CB related to all paths managed by the path information management unit 12, and the variable “rsv_num” is changed to the variable “max_burst”. ”Is less than“ ”, a transmission reservation is made for the top data (data indicated by the variable“ rsv_nxt ”).

  Here, the variable “max_burst” indicates the maximum data amount (number of segments) that can be transmitted at a time when an ACK is received. The variable “max_burst” is a variable common to all paths (interfaces).

  Then, the transmission segment management unit 11 makes a transmission reservation for the segment in which the “rsv” flag is not set from the top data of the transmission segment management unit 11 (“data indicated by the variable“ rsv_nxt ””). The management unit 12 adds the data amount of the segment for which transmission reservation has been made to the variable “rsv_num” in the TCP-CB corresponding to the path used for transmission of the segment.

  The reserved segments are connected by the variable “next”, and the next reserved segment can be traced by following the variable “next” in the special header given to each segment. .

  Here, when a value is already set in the variable “rsv_num”, the transmission segment management unit 11 performs transmission reservation only for the segments corresponding to “cwnd” − “rsv_num”.

  That is, the transmission segment management unit 11 is configured to make a transmission reservation for a segment such that the variable “rsv_num” = the variable “cwnd”.

  However, when the advertisement window value in the ACK is smaller than the sum (Σcwnd) of the variables “cwnd” managed by all the path information management units #n, the transmission segment management unit 11 sets the variable “rsv_num” Do not exceed “advertising window value in ACK × cwnd / Σcwnd”.

  When the transmission reservation is completed, the transmission segment management unit 11 sets “rs” in the “rsv” flag in the special header described above, and sets the identification information of the path for which the transmission reservation has been made to the variable “path” in the header. To "".

  Here, when the transmission reservation is made for the segment located before the position set in the variable “snd_nxt”, the path information management unit 12 sets the variable “snd_nxt” next to the segment for which the transmission reservation has been made. Set the start position of the segment.

  When the variable “rcv_nxt” falls below the variable “snd_nxt”, the path information management unit 12 similarly sets the value set to “snd_nxt” to the variable “rcv_nxt”.

  In step S <b> 104, the segment transmission unit 13 sequentially transmits the segments for which transmission reservation is performed to the receiving terminal 30 using the plurality of paths # 1 to # 3 simultaneously.

  If “cwnd” − “snd_num”> 0, the segment transmission unit 13 performs transmission in order from the segment indicated by the variable “snd_nxt”.

  Here, the variable “snd_num” is the number of segments that have been transmitted in the corresponding path and have not received ACK.

  When the segment transmission unit 13 transmits a segment via a specific path, the path information management unit 12 subtracts the data amount of the segment transmitted from the variable “rsv_num” in the TCP-CB related to the specific path. Then, the data amount of the segment transmitted to the variable “snd_num” in the TCP-CB related to the specific path is added.

  Each time the segment transmission unit 13 transmits a segment, the path information management unit 12 follows the variable “next” and sets the start position of the next segment to the variable “snd_nxt”.

  When the segment transmission unit 13 transmits a segment and the variable “t_timer” is not set, the path information management unit 12 calculates the variable “t_timer” from the variable “rtt” or the like. A new timeout value is set, and the sequence number (seq) of the transmitted segment is set in the variable “t_seq”.

  FIG. 9 shows an example of the above-described special header and TCP-CB when the transmission terminal 10 transmits the segment # 4 via the path # 1.

  In this case, in the special header assigned to segment # 4 in the transmission segment management unit 11, the variable “path” = 1, the variable “sack” = 0, the “rsv” flag = 0, and the variable “next” = 0. Is set.

  In TCP-CB (1) related to path # 1, the variable “rcv_nxt” = 1, the variable “snd_nxt” = 4, the variable “rsv_num” = 1, and the variable “snd_num” = 1 are set.

  Secondly, with reference to FIGS. 10 and 11, an operation in which the transmission terminal 10 according to the present embodiment receives an ACK will be described.

  As shown in FIG. 10, in step S301, the segment receiving unit 14 of the transmitting terminal 10 receives the ACK transmitted from the receiving terminal 30, and [(sender's IP address, port Number) and (recipient's IP address, port number)], the ACK is transferred to an appropriate path information management unit #n.

  In the example of FIG. 11, the segment receiver 14 of the transmission terminal 10 manages the ACK (A) or (B) received from the reception terminal 30 and the path # 1 that has received the ACK (A) or (B). Transfer to path information management unit # 1.

  Here, ACK (A) shown in FIG. 11 notifies that the segment with the smallest sequence number among the segments that have not yet been received is “segment # 1”.

  In addition, the ACK (B) shown in FIG. 11 notifies that the segment with the smallest sequence number among the segments that have not been received is “segment # 2”, and the segment # 7 is received by the SACK option. Is a notification of success.

  Note that the ACK may be configured to notify successful reception of a plurality of segments by one SACK option.

  In step S302, the path information management unit #n sets the variable “sack” in the special header for the segment whose arrival to the receiving side is reported by the received ACK and SACK option by the path information management unit #n. The transmission segment management unit 11 is instructed to set the identification information of the managed path.

  If the path identification information set in the variable “sack” matches the path identification information set in the variable “path”, the variable “sack” is overwritten when another ACK is received. do not do.

  In the example of FIG. 11, the path information management unit # 1 sets the variable “sack” in the special header assigned to the segment # 1 notified of successful reception by ACK (A) to the variable “sack”. The transmission segment management unit 11 is instructed to set the identification information.

  In the example of FIG. 11, the path information management unit # 1 sets the variable “sack” in the special header attached to the segment # 7 that is notified of the successful reception by the SACK option of ACK (B). The transmission segment management unit 11 is instructed to set the identification information of the path # 1.

  In step S303, the path information management unit #n compares the variable “rcv_nxt” in the TCP-CB (n) with the sequence number (seq) of the segment notified by the ACK or SACK option.

  When the variable “rcv_nxt” is smaller than the seq (ACK), or when the reception of the segment corresponding to the variable “rcv_nxt” is not notified by the SACK block, the operation proceeds to step S304. In other cases, the operation proceeds to step S305.

  In the example of FIG. 11, since the “sequence number of segment # 1” is set in the variable “rcv_nxt” in TCP-CB (n), the path information management unit # 1 has received ACK (A). In this case, the operation proceeds to step S305.

  In step S305, the path information management unit #n determines whether or not the variable “sack” in the special header related to the segment specified by the variable “rcv_nxt” in the TCP-CB (n) matches the variable “path”. Judgment is made.

  In step S305, when the variable “sack” in the special header relating to the segment specified by the variable “rcv_nxt” in the TCP-CB (n) matches the variable “path”, in step S306, the variable “rcv_nxt”. Next, the segment to be set is moved according to the variable “next” in the TCP-CB (n).

  In the case of FIG. 11, the segment “# 4” is set in the variable “rcv_nxt” by receiving the ACK (A) (the variable “next” in the special header given to the segment # 1 is the path # 1). To point to the next segment to be transmitted). This process continues until a segment is found in which the variable “sack” does not match the variable “path”.

  On the other hand, if a segment in which the variable “sack” does not match the variable “path” is found in step S305, it is determined whether or not the variable “rcv_nxt” has been updated in step S307.

  If the variable “rcv_nxt” has been updated, the variable “t_timer” is canceled in step S308. In step S309, the segment up to the minimum variable “rcv_nxt” is transmitted to all the path information management units. Delete from.

  In step S308, after step S307, in step S308a, the segment variable “p_seq” corresponding to the variable “rcv_nxt” is changed to the segment variable “p_seq” corresponding to the variable “t_seq” managed by the path information management unit 12. If it exceeds, it will be cancelled.

  On the other hand, step S309 is always executed after step S308 regardless of the presence or absence of step S308.

  On the other hand, when ACK (B) is received, the variable “rcv_nxt” in TCP-CB (n) is updated in segment # 4 (variable “rcv_nxt” is updated by receiving ACK (A) in the example of FIG. 11. The 1st block of the SACK option notifies the segment # 7, but does not include the segment # 4 set in the variable “rcv_nxt”, so this operation moves to step S304). Since arrival at the receiving side is not reported by the ACK or SACK option, the operation moves to step S304.

  In step S304, the maximum sequence number of the segment in which the path identification information set in the variable “sack” matches the path identification information set in the variable “path” for the segment transmitted in the path. , The variable “max_sack” in the TCP-CB (n) is set.

  In the example of FIG. 11, when ACK (B) is received, segment # 7 is set to the variable “max_sack” in the TCP-CB (n).

  Next, in step S310, the number of segments in which the variable “sack” is not set is counted between the variable “max_sack” and the variable “rcv_nxt”. Such calculation can be easily performed by referring to the variable “rcv_nxt”, the variable “max_sack”, and the variable “p_seq”.

If there are three or more such segments, in step S311, the segment transmitted from the path below the variable “max_sack” and the variable “sack” is not set, and the variable “snd_nxt” or more. Deletes the “rsv” flag of the segment reserved for the path, and shifts to the retransmission mode (the segment reserved for the variable “snd_nxt” or more is reserved for transmission but not yet transmitted) (There are no segments.)
In the case of the example of FIG. 11, the “rsv” flags of the segments # 4, # 5, and # 6 are deleted.

  At the same time, in step S312, based on the initialization result, the variable “rsv_num”, variable “snd_num”, and variable “snd_nxt” are updated in TCP-CB (n).

  Note that the mode changes to the retransmission mode not only by ACK reception but also by expiration of the variable “t_timer”. The operation in this case starts from step S311. However, in step S311, the variable “t_timer” expires below the variable “snd_nxt”, although the variable “max_sack” is equal to or less than the variable “max_sack”.

  Thirdly, with reference to FIG. 11 and FIG. 12, an operation in the “retransmission mode” of the transmission terminal 10 according to the present embodiment will be described.

  As shown in FIG. 12, in step S <b> 401, the “retransmission mode” is activated in the transmission terminal 10. At this time, the path information management unit #n sets half of the variable “cwnd” in the variable “ssthresh” and “1” in the variable “cwnd” in TCP-CB (n).

  The path information management unit #n may be configured to set the variable “cwnd” and the variable “ssthresh” in consideration of the wireless type.

  In step S403, the transmission segment management unit 11 makes a transmission reservation for the segment again based on TCP-CB (TCP control information) managed by each path information management unit #n.

  Here, when a plurality of paths are used, transmission reservation is performed using a path different from the path identification information indicated by the variable “path” (the segment is lost by the path indicated by the variable “path”). Therefore, if the path is used again, there is a high possibility that it will be lost again. Therefore, a new path is used when the segment is retransmitted).

  Here, the transmission segment management unit 11 sets the variables “path” and “rsv” in the special header given to the segment for which transmission reservation has been made, and sets the path information management unit #n, TCP-CB ( Update the variable “rsv_num” in n).

  In step S404, the segment transmitting unit 13 transmits the segments for which transmission reservations are made sequentially to the receiving terminal 30 by using a plurality of paths # 1 to # 3 at the same time as in the operation of step S104 described above. To do.

  Here, when the segment transmission unit 13 transmits a segment via a specific path, the transmission segment management unit 11 sets “1” in the “snd” flag in the special header related to the segment, and the path information The management unit 12 subtracts the amount of segment data transmitted from the variable “rsv_num” in the TCP-CB related to the specific path, and transmits the data of the segment transmitted to the variable “snd_num” in the TCP-CB related to the specific path. Add quantity.

  Each time the segment transmission unit 13 transmits a segment, the path information management unit 12 sets a special header in which “1” is set in the “rsv” flag selected from the segments located behind the segment. Is set to the variable “snd_nxt”.

  When the segment transmission unit 13 transmits a segment and the variable “t_timer” is not set, the path information management unit 12 calculates the variable “t_timer” from the variable “rtt” or the like. A new timeout value is set, and the sequence number (seq) of the transmitted segment is set in the variable “t_seq”.

  Fourthly, with reference to FIG. 13 to FIG. 15, an operation in which the receiving terminal 30 according to this embodiment receives a segment transmitted by the transmitting terminal 10 will be described.

  As shown in FIG. 13, in step S501, the segment receiving unit 31 of the receiving terminal 30 selects the received segment [(sender's IP address, port number), (receiver's IP Address, port number)]] is transferred to an appropriate path information management unit #n.

  Here, the reception segment management unit 33 manages the segment transferred from the path information management unit #n by adding a special header. Note that the reception segment management unit 33 may be configured to manage the segments in the order of the sequence numbers of the received segments.

  Here, the reception segment management unit 33 sets the segment in the variable “next” of the special header of the segment received immediately before the segment in the path in the special header given to the segment. To do.

  In step S502, the segment transmission unit 34 generates an ACK for the segment received by the reception segment management unit 33. In step S503, the segment transmission unit 34 generates a SACK option for adding to the ACK.

  Here, the 1st block in the SACK option indicates a block including a segment received this time, the 2nd block in the SACK option indicates a segment received last time through the same path as the segment received this time, and the 3rd block in the SACK option Indicates a segment received two times in advance through the same path as the segment received this time.

  In the example of FIG. 14, in the SACK option given to ACK (A) generated when segment # 10 is received via path # 1, “identification information of segment # 10” is set in the 1st block. “Identification information of segment # 8” is set in the 2nd block, and “identification information (3-4) of segment # 3, # 4” is set in the 3rd block.

  In this case, in the conventional SACK option, “identification information of segment # 6” is set in the 3rd block.

  In the example of FIG. 14, in the SACK option given to the ACK (B) generated when the segment # 11 is received via the path #n, “identification of the segments # 10 and # 11 is included in the 1st block. "Information (10-11)" is set, "Identification information of segment # 6" is set in the 2nd block, and "Identification information (3-4) of segment # 3, # 4" is set in the 3rd block.

  In this case, in the conventional SACK option, “identification information of segment # 8” is set in the 2nd block, and “identification information of segment # 6” is set in the 3rd block.

  In step S504, the path information management unit #n refers to the variable “rcv_nxt” to determine whether or not the segment reception via the same path is continuous.

  If the operation is continuous, the operation proceeds to step S505. If the operation is not continuous, the operation proceeds to step S506.

  In step S505, the path information management unit #n sets the identification information of the next segment of the received segment to the variable “rcv_nxt” in TCP-CB (n), and sets the variable “del_ack” in step S502. The identification information of the segment notified by the generated ACK (the segment with the smallest sequence number among the segments not yet received) is set, and the variable “p_sack 1 to 3” is set by each block of the SACK option generated in step S503. Set the segment identification information to be notified.

  Further, the path information management unit #n activates the variable “del_timer” in TCP-CB (n).

  If a new segment is not received while the variable “del_timer” expires, the value of the variable “del_ack” is returned (if a new segment is received, the variable “del_timer” is canceled).

  Before entering step S505, it is determined whether or not ACK is stored in step S505a. If stored, the process proceeds to step S506, and if not stored, the process proceeds to step S505.

  In step S506, the segment transmission unit 34 generates and transmits an ACK based on the variables “p_sack1 to 3” in TCP-CB (n). In such a case, the path information management unit #n updates the variable “rcv_nxt” in TCP-CB (n) as necessary.

  In the example of FIG. 15, the segment transmission unit 34 continuously receives the segments # 6 and # 7 via the same path # 2, so that two segments # 6 and # 7 are received successfully. Instead of notifying by ACK, it is configured to notify by one ACK.

(Operations and effects of the communication terminal according to the first embodiment of the present invention)
According to the communication terminal according to the present embodiment, since the segment is transmitted using only a normal TCP header, the receiving terminal 30 to which the technology according to the present invention is not applied Communication can be performed even between the two.

  The communication terminal according to the present embodiment is configured to transmit ACK through a plurality of paths, so that RTT can be accurately measured and is equivalent to normal TCP control for each path. Can be controlled.

  According to the communication terminal according to the present embodiment, since a plurality of ACKs (acknowledgment confirmation signals) can be transmitted together (for example, C-ACK can be supported), the number of ACKs to be transmitted is reduced. can do.

(Modification 1)
With reference to FIG.16 and FIG.17, the example 1 of a change of this invention is demonstrated.

  As shown in FIG. 16, the segment receiving unit 13 of the transmitting terminal A according to the first modification forms an ad hoc network with the neighboring communication terminals B to E, and sets the paths # 1 to # 3 in the ad hoc network. Is configured to transmit the segment over the network.

  Note that the transmitting terminal A is a paper “A hybrid Approach to Internet Connectivity for Mobile Ad Hoc Networks” (P. Ratchandani and R. Cratons, Proceedings of IEc W, and Proceedings of IEt. Y. Sun, E. Belding-Royer, C. Perkins, International Journal of Wireless Information Networks, special issue on Mobile Ad Hoc Networks, MANETs: MANETs. ch, Applications, 9 (2), using the techniques described in April 2002) "and the like, it is necessary to know in advance for the gateway and comprising terminals C to E of the fixed network.

  As shown in FIG. 17, the transmission terminal A sets the “address of the transmission terminal F” as the destination address and the “address of the reception terminal A” as the transmission source address via the path # 1. Assume that a segment addressed to the receiving terminal F is transmitted using the first packet including the header.

  First, the transmitting terminal A encapsulates the first packet by the second header in which “the address of the transmitting terminal E” is set as the destination address and “the address of the receiving terminal A” is set as the source address. The second packet is transmitted to terminal E.

  Second, the terminal E sets the “address of the transmission terminal F” as the destination address and the “address of the reception terminal E” as the transmission source address of the first packet included in the received second packet. The third packet encapsulated again by the set third header is transmitted to the receiving terminal F.

  Thirdly, the receiving terminal F determines the path through which the segment is transmitted based on the header of the third packet. In the example of FIG. 17, the receiving terminal F can determine the path F → E → A by referring to the first header and the third header.

  Similarly to the segment transmission unit 13 of the transmission terminal A according to the modification example 1, the segment transmission unit 34 of the reception terminal F according to the modification example 1 forms an ad hoc network with neighboring communication terminals, and the ad hoc network It may be configured to receive the segment via the path within.

  According to the communication terminal according to the present embodiment, by using a path in the ad hoc network formed between neighboring communication terminals, even in a communication terminal having no plurality of interfaces, the transmission terminal and the reception terminal It is possible to realize communication (that is, multihome connection) by simultaneously using a plurality of paths existing in between.

  Even if the receiving terminal does not have the function corresponding to the first modification example as described above, if the receiving terminal has the “Mobile IP” function defined in RFC3775, the transmitting terminal When a segment is transmitted using, a BU (Binding Update) for the address corresponding to the interface that transmitted the packet is added to operate the interface that returns ACK, and the 1st block of the SACK option is By referring, it becomes possible for the segment receiving unit 14 to transmit the received ACK to the appropriate path information managing unit #n, and the receiving terminal has a function corresponding to the first modified example as described above It is possible to enjoy the same merits.

1 is an overall configuration diagram of a communication system including a communication terminal according to a first embodiment of the present invention. It is a functional block diagram of the communication terminal (transmission terminal) which concerns on the 1st Embodiment of this invention. It is a figure which shows an example of the management content of the transmission segment management part of the communication terminal (transmission terminal) which concerns on the 1st Embodiment of this invention. It is a figure which shows an example of the management content of the path information management part of the communication terminal (transmission terminal) which concerns on the 1st Embodiment of this invention. It is a functional block diagram of the communication terminal (receiving terminal) which concerns on the 1st Embodiment of this invention. It is a figure which shows an example of the management content of the path information management part of the communication terminal (receiving terminal) which concerns on the 1st Embodiment of this invention. It is a figure which shows an example of the management content of the receiving segment management part of the communication terminal (receiving terminal) which concerns on the 1st Embodiment of this invention. It is a flowchart which shows the operation | movement which the communication terminal (transmission terminal) which concerns on the 1st Embodiment of this invention transmits a segment. It is a figure for demonstrating the operation | movement which the communication terminal (transmission terminal) which concerns on the 1st Embodiment of this invention transmits a segment. It is a flowchart which shows the operation | movement which the communication terminal (transmission terminal) which concerns on the 1st Embodiment of this invention receives ACK. It is a figure for demonstrating the operation | movement which the communication terminal (transmission terminal) which concerns on the 1st Embodiment of this invention receives ACK. It is a flowchart which shows the operation | movement of the resending mode in the communication terminal (transmission terminal) which concerns on the 1st Embodiment of this invention. It is a flowchart which shows the receiving operation in the communication terminal (receiving terminal) which concerns on the 1st Embodiment of this invention. It is a figure for demonstrating the reception operation | movement in the communication terminal (receiving terminal) which concerns on the 1st Embodiment of this invention. It is a figure for demonstrating the reception operation | movement in the communication terminal (receiving terminal) which concerns on the 1st Embodiment of this invention. It is a figure for demonstrating the communication terminal which concerns on the example 1 of a change of this invention. It is a figure for demonstrating the communication terminal which concerns on the example 1 of a change of this invention.

Explanation of symbols

DESCRIPTION OF SYMBOLS 10 ... Transmission terminal 10a, 30a ... Application function part 11 ... Transmission segment management part 12, 32 ... Path information management part 13, 34 ... Segment transmission part 14, 31 ... Segment reception part 30 ... Reception terminal 33 ... Reception segment management part

Claims (11)

A communication terminal capable of simultaneously transmitting data to a receiving terminal using a plurality of paths,
A path information management unit configured to manage TCP control information related to each of the plurality of paths;
A transmission segment manager configured to store a segment generated by dividing data to be transmitted to a receiving terminal;
A segment transmission unit configured to extract the segment from the transmission segment management unit and transmit the segment to the reception terminal;
The transmission segment management unit is configured to make a transmission reservation for the segment by associating and storing the segment and a path used for transmission of the segment based on the TCP control information,
The segment transmission unit is configured to extract only the segment from the transmission segment management unit and transmit the segment to the receiving terminal via a path associated with the segment. Communication terminal.   When the delivery confirmation signal related to the segment is received via the same path as the path used for transmission of the segment, among all the transmission segment management units, the segment that has not received the delivery confirmation signal The communication terminal according to claim 1, further comprising: a segment receiving unit configured to delete a segment having a sequence number smaller than a minimum sequence number from the transmission segment management unit.   The transmission segment management unit is configured to cancel transmission reservations for all segments that have not received a delivery confirmation signal when a timeout is detected, and perform transmission reservations for the segments again based on the TCP control information The communication terminal according to claim 1 or 2.   The transmission segment management unit, when there is a predetermined number or more of segments that have not received the delivery confirmation signal between the largest segment that has received the selective delivery confirmation signal and the segment that should receive the next delivery confirmation signal, Cancel a transmission reservation for a segment that has not received a delivery confirmation signal with a sequence number equal to or less than the sequence number of the largest segment that has received the selective acknowledgment signal, and an untransmitted segment, and again based on the TCP control information, The communication terminal according to claim 1, wherein the communication terminal is configured to make a transmission reservation for the segment.   5. The segment transmission unit is configured to form an ad hoc network with neighboring communication terminals and transmit the segment via the path in the ad hoc network. The communication terminal according to any one of the above. A communication terminal capable of receiving data from a transmission terminal using a plurality of paths simultaneously,
A path information management unit configured to manage TCP control information related to each of the plurality of paths;
A segment receiver configured to receive a segment generated by dividing the data via the plurality of paths;
A received segment management unit configured to store the received segment for each path through which the segment is transmitted;
A communication terminal, comprising: a segment transmission unit configured to transmit a delivery confirmation signal for notifying a reception result of a segment through each path based on the TCP control information.   The communication terminal according to claim 6, wherein the delivery confirmation signal is configured to notify a sequence number of a segment that has been successfully received via the path.   When a plurality of segments having consecutive sequence numbers are received via the same path, the delivery confirmation signal is configured to collectively notify the reception results of the plurality of segments. The communication terminal according to claim 6.   9. The segment receiving unit is configured to form an ad hoc network with neighboring communication terminals and receive the segment via the path in the ad hoc network. The communication terminal according to any one of the above. A communication method in which a transmitting terminal transmits data to a receiving terminal using a plurality of paths simultaneously,
A segment generated by dividing the data to be transmitted to the receiving terminal based on TCP control information managed for each of the plurality of paths by the transmitting terminal, and a path used for transmitting the segment Storing transmission data in the transmission segment management unit in association with each other,
The transmitting terminal extracts only the segment from the transmission segment management unit, and transmits the segment to the receiving terminal via a path associated with the segment;
The receiving terminal manages the received segment for each path through which the segment is transmitted, and the segment reception result via each path based on the TCP control information managed for each of the plurality of paths. Sending a delivery confirmation signal to notify
When the transmission confirmation signal related to the segment is received through the same path as that used for transmission of the segment, the transmission terminal sets the transmission segment to the segment and the path associated with the segment. And a step of deleting from the management unit. The transmitting terminal and the receiving terminal form an ad hoc network with neighboring communication terminals,
The transmitting terminal transmits the generated segment to the receiving terminal via the path in the ad hoc network;
The communication method according to claim 10, wherein the receiving terminal receives the segment via the path in the ad hoc network.

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