JP2009071766A - Signal receiving terminal apparatus - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a signal receiving terminal apparatus which does not reduce its signal transmitting efficiency without applying any excessive load to a network, by minimizing its buffers and by preventing the signal re-sending caused by the packet losses originated from the overruns generated in its buffers. <P>SOLUTION: In the signal receiving apparatus (265), the payload lengths (PLD_LEN) of data (P) are so detected and a pre-indicated maximum window size (Win_SZ(max))is so held as to calculate window sizes (X) based on the maximum (Win_SZ(max)), the payload lengths, and a flow controlling indication (Almost_Full_st) given from the external. <P>COPYRIGHT: (C)2009,JPO&INPIT

Description

  The present invention relates to a terminal device that receives data according to a predetermined communication protocol, and more particularly to a TCP receiving terminal device that receives data according to a TCP protocol.

  FIG. 4 shows an example of a network conventionally used for streaming distribution of moving images and music. In the streaming distribution network, a server 100 that performs a streaming distribution service is connected via an Internet 1000 and a router 1004 to a home network 2000 configured in a user's home that receives the distribution service. Note that an AV device 200 that uses a distribution service provided from the server 100 is connected to the home network 2000. In FIG. 4, a dotted line Ld represents data transmission from the server 100 to the AV device 200. An alternate long and short dash line Li represents data transfer in the home network 2000.

  The server 100 includes servers 100_1, 100_2, and 100_3 that perform different streaming distribution services. In this example, the server 100_1 distributes moving images, the server 100_2 distributes music, and the server 100_3 distributes others.

  The AV device 200 includes a digital TV 200_1, a digital video recorder 200_2, an audio device 200_3, and a personal computer (hereinafter “PC”) according to the contents of the data streams distributed from the servers 100_1, 100_2, and 100_3. ) 200_4 is connected and device cooperation is performed.

  A TCP communication protocol is often used for communication services in such a streaming distribution network from the viewpoint of ensuring communication quality. In addition, as the speed of networks such as the Internet increases, a device called TCP Offload Engine (hereinafter referred to as “TOE”) that processes part or all of the TCP communication protocol that has been processed by software in hardware has also become widespread. I am doing.

  There are three advantages in using the TCP communication protocol: high affinity with the network, high communication quality, and flow control on the transmission side. Specifically, since the TCP communication protocol is widespread on the Internet, it has a high affinity with a network, particularly the Internet. The communication quality is high because the acknowledgment from the reception side for the transmission packet and the retransmission mechanism are implemented. The flow control on the transmission side can be performed using the window size from the reception side.

  Next, flow control when the TCP communication protocol is used will be described with reference to FIG. FIG. 5 shows a data transmission sequence between the TCP transmission terminal device 260 in the server 100 and the TCP reception terminal device 265 in the AV device 200. In the TCP communication protocol, first, the window size X1 representing the amount of data that can be processed by the buffer on the TCP receiving terminal device 265 side is determined. Then, a packet P200 (indicated as P200 (X1) in the figure) reflecting the window size X1 is generated and transmitted to the TCP transmission terminal device 260.

  In the distribution service using the Internet, the servers 100_1, 100_2, and 100_3 have a function corresponding to the TCP transmission terminal device 260 in FIG. Similarly, the digital TV 200_1, the digital video recorder 200_2, the audio device 200_3, and the PC 200_4 have the function of the TCP receiving terminal device 265. Note that in the home, the digital video recorder 200_2, the audio device 200_3, and the PC 200_4 have functions corresponding to both the TCP transmission terminal device 260 and the TCP reception terminal device 265, and the digital TV 200_1 functions as the TCP reception terminal device 265. It has a corresponding function.

  In response to the packet P200, packets P210, 211, and 212 are sequentially transmitted from the TCP transmission terminal apparatus 260 to the TCP reception terminal apparatus 265. After receiving the packet P212, the TCP receiving terminal device 265 again determines the window size X2 representing the amount of data that can be processed by the buffer, and an acknowledgment ACK250 (ACK250 (X2) in the figure) reflecting the window size X2. Display). Then, the TCP receiving terminal device 265 transmits an acknowledgment ACK 250 to the TCP transmitting terminal device 260.

  The TCP transmission terminal device 260 transmits the packets P213 and P214 in response to the confirmation response ACK250. After receiving the packets P213 and 214, the TCP receiving terminal device 265 determines a window size X3 representing the amount of data that can be processed by the buffer, and an acknowledgment ACK 251 (ACK 251 in the figure) reflecting the window size X3. (Displayed as (X3)). The confirmation response ACK 251 is transmitted from the TCP receiving terminal device 265 to the TCP transmitting terminal device 260, and thereafter the same processing continues. Note that the window sizes X1, X2, X3,... Are collectively referred to as a window size X.

  FIG. 6 shows a configuration example of a TCP packet header Hp used in the TCP communication protocol. The TCP packet header Hp has an area in which information such as a transmission source TCP port, a destination TCP port, a TCP sequence number, a TCP acknowledgment number, and a window size is written. In this specification, each area is referred to as an information name to be written (for example, a window size area). The window size X written in the TCP packet header Hp is 16 bits and can take a value of 64K-1 bytes at the maximum.

  FIG. 7 shows a configuration of an example of a conventional TCP receiving terminal device 265 (hereinafter, “conventional example 1”). The TCP receiving terminal device 265a according to this example forms part of the AV device 200 together with the application unit 300. That is, the TCP receiving terminal device 265 a (TCP receiving terminal device 265) has a function for the AV device 200 to receive streaming data transmitted from the server 100 via the Internet 1000 and the home network 2000.

  The application unit 300 has a function of processing a payload included in the received streaming data so that the content can be presented to the user. That is, the AV device 200 functions as a digital TV 200_1, a digital video recorder 200_2, an audio device 200_3, a PC 200_4, or the like by the function of the application unit 300.

  The TCP receiving terminal device 265a includes a transmission / reception unit 1, an IP control unit 2, a TCP control unit 3a, and a payload output unit 4. The TCP control unit 3 a includes a TCP reception buffer 30 and a window size calculation unit 31.

The transmission / reception unit 1 is connected to the home network 2000 by a route C201. The transmission / reception unit 1 and the IP control unit 2 are connected to each other by a path C202.
The IP control unit 2 is connected to the window size calculation unit 31 through a path C208. The TCP reception buffer 30 is connected to the IP control unit 2 by a path C203. The window size calculation unit 31 is connected to the TCP reception buffer 30 through a path C206.

  The payload output unit 4 is connected to each of the TCP reception buffer 30 and the Almost_Full detection unit 102 by a path C204 and a path C301. In the application unit 300, the application buffer 101 is connected to the payload output unit 4 through a path C205. The Almost_Full detector 102 is connected to the application buffer 101 by a path C300.

  The flow control in the AV device 200a will be specifically described below with reference to FIGS. In the TCP receiving terminal device 265a, before the reception of the data stream distributed from the home network 2000 is started, the window size calculating unit 31 in the TCP control unit 3 uses the free space of the TCP receiving buffer 30 via the path C206. The capacitance value Vf30 is monitored to calculate the window size X1 (FIG. 5). The window size calculation unit 31 reflects the calculated window size X1 in the window size area of the TCP header to generate a packet P200. The generated packet P200 is passed to the IP control unit 2 via the path C208.

  The IP control unit 2 performs transmission processing on the packet P200 according to the IP protocol, and then passes it to the transmission / reception unit 1 via the path C202. The transmission / reception unit 1 transmits the passed packet P200 to the home network 2000.

  The TCP transmission terminal device 260 (FIG. 5) receives the packet P200 from the home network 2000. The TCP transmission terminal device 260 determines the number of bytes of transmission data based on the window size X1 written in the TCP packet header Hp of P200. Then, the TCP transmission terminal device 260 divides the data stream to be distributed into one or a plurality of packets and sequentially transmits them as packets P210, P211 and P212.

  Packets P210, P211, and P212 sequentially transmitted from the TCP transmission terminal device 260 are received by the transmission / reception unit 1 via the Internet 1000, the home network 2000, and the route C201. The received packets P210, P211 and P212 are passed to the IP control unit 2 via the path C202.

  The IP control unit 2 performs reception processing according to the IP protocol on the packets P210, P211, and P212, and then passes them to the TCP reception buffer 30 of the TCP control unit 3a via the path C203.

  In the TCP control unit 3a, processing according to the TCP reception processing is performed, and based on the TCP sequence number and the TCP checksum described in the TCP packet header Hp (FIG. 5), the received packets (P210, P211, And the validity of P212) is determined. Then, only the payload data Dp is extracted from the received packets (P210, P211, and P212) determined to be valid and passed to the payload output unit 4 via the path C204. Further, the payload data Dp is passed from the payload output unit 4 to the application buffer 101 of the application unit 100 via the path C205.

  In the TCP control unit 3a, the window size calculation unit 31 monitors the free capacity value Vf30 of the TCP reception buffer 30 via the path C206 and calculates the window size X2. In the window size calculation unit 31, the calculated window size X2 is referred to by the confirmation response ACK 250 returned to the transmission source. The ACK 250 is passed to the IP control unit 2 via the route C208.

  The IP control unit 2 performs transmission processing on the confirmation response ACK 250 according to the IP protocol, and then passes it to the transmission / reception unit 1 via the path C202. The transmission / reception unit 1 transmits an acknowledgment ACK 250 to the home network 2000 via the path C201. Thereafter, similarly, packets P213 and P214 are transmitted from the TCP transmission terminal apparatus 260 to the TCP reception terminal apparatus 265.

  Then, the window size X3 is calculated, and the confirmation response ACK 251 is transmitted to the TCP transmission terminal device 260. Note that the confirmation responses ACK 250 and ACK 251 and packets P 213 and P 214 are not displayed in FIG. 7 due to space limitations.

  In FIG. 8, as a further example of the conventional TCP receiving terminal device 265, the configuration of a wireless communication terminal device (hereinafter, “conventional example 2”) proposed in Japanese Patent Application Laid-Open No. 2006-2111015 (Patent Document 1) The comparison is made with the above-described TCP receiving terminal device 265a, and the TCP receiving terminal device 265b in this example also constitutes a part of the AV device 200 together with the application unit 300.

  In the TCP reception terminal device 265b, the transmission / reception unit 1 and the TCP control unit 3a are replaced with a transmission / reception unit 1b and a TCP control unit 3b, respectively, in the TCP reception terminal device 265a. Further, a buffer amount estimation unit 401 and an RWIN control unit 402 are added between the TCP control unit 3b and the transmission / reception unit 1b. Note that the buffer amount estimation unit 401 is bidirectionally connected to the transmission / reception unit 1 and the RWIN control unit 402 via a path C451 and a path C452, respectively. The RWIN control unit 402 is bidirectionally connected to the TCP control unit 3b through a path C453.

  Unlike the transmission / reception unit 1, the transmission / reception unit 1 b includes a reception buffer 10. On the other hand, unlike the TCP control unit 3a, the TCP control unit 3b does not include the TCP reception buffer 30 and the window size calculation unit 31.

  Before starting the reception, the buffer amount estimation unit 401 estimates the free capacity value Vf10 of the reception buffer 10 in the transmission / reception unit 1b via the path C451, and sends the free capacity value Vf10 to the RWIN control unit 402 via the path C452. To be notified. The RWIN control unit 402 determines the window size X1 of the number of receivable bytes based on the empty capacity value Vf10 notified from the path C452, and determines the window size determined by the TCP control unit 400 via the path C453. The size X1 is notified.

  Thereafter, as a result of the same processing as in the AV device 200a described above, P packets 210 to P212 are sequentially transmitted from the TCP transmission terminal device 260 to the TCP reception terminal device 265b, and the payload data Dp is transmitted from the P packets 210 to P212. Are extracted and passed to the application buffer 101.

  The buffer amount estimation unit 401 periodically estimates the free capacity value Vf10 of the reception buffer 10 and notifies the RWIN control unit 402 of it. The RWIN control unit 402 determines a window size X2 representing the number of receivable bytes based on the free capacity value Vf10 and notifies the TCP control unit 3b of the window size X2. Since the subsequent processing is the same as that in the above-described AV device 200a, description thereof will be omitted.

  As described above, in the TCP communication protocol, flow control for adjusting the amount of data to be received is performed by controlling the window size from the reception side (TCP reception terminal device 265) to the TCP transmission terminal device 260. . In other words, in the TCP communication protocol, the transmission side (TCP transmission terminal device 260) does not transmit a packet larger than the number of bytes that can be received by the reception side (TCP reception terminal device 265). The packet transmitted in (265) is not missed.

  Next, the data transmission performance of the TCP communication protocol will be described with reference to FIG. FIG. 9 shows the relationship between the window size X1 and the packets 210, P211, and P212, and the relationship between the acknowledgment ACK 250 (window size X2) and the packets P213 and P214. Note that RTT represents the round trip time from the start of data transfer to the start of the next data transfer. In this example, transmission of the packet P210 is started in response to the packet P200 (window size X1) until transmission of the packet P213 is started in response to the acknowledgment ACK 250 (window size X2). It's time.

With the round trip time RTT and the window size X (bytes), the transmission performance can be expressed by the following equation (1).
Transmission performance = X / RTT ... Formula (1)

  From the above equation (1), for example, the round trip time RTT has the same value, and the transmission performance between the two receiving terminal devices having different window sizes X depends on the window size X. It can be seen that there is a difference. In other words, in the TCP receiving terminal device 265 implemented as a single chip as the TOE, the free space value Vf of the buffer in the device is notified to the transmission source as the window size X, so the maximum value of the window size X is mounted. It becomes the capacity of the buffer. Therefore, in order to improve the transmission performance, it is necessary to have a large-capacity buffer, resulting in high cost.

As another method for improving the transmission performance, it is also possible to notify a window size X that is equal to or larger than the size of the buffer in the TCP control unit. However, when the application unit 100 is notified that the application buffer 101 is almost exhausted via the path C301 to the TCP receiving terminal device 265, the payload extraction unit 4 stops the payload extraction from the buffer. In this case, the buffer in the TCP receiving terminal apparatus receives more packets than can be received. As a result, an overrun of the received packet occurs and packet loss occurs. Then, retransmission of lost packets occurs frequently, increasing network load and reducing transmission efficiency.
JP 2006-2111015 A

  In view of the above problems, the present invention minimizes the buffer and prevents retransmission due to packet loss due to overrun in the buffer, thereby reducing transmission efficiency without imposing an unnecessary load on the network. An object of the present invention is to provide a receiving terminal device that does not decrease.

In order to achieve the above object, a receiving terminal device according to the present invention provides:
A receiving terminal device used for data transmission using a communication protocol that notifies a window size representing a receivable data size and performs flow control of data transmission to the transmitting terminal device,
Payload length detecting means for detecting the payload length of the data;
Maximum window size holding means for holding a pre-specified maximum window size;
Window size calculating means for calculating the window size based on the maximum window size, the payload length, and a flow control instruction given from the outside.

  Here, the communication protocol is preferably a TCP protocol. Further, it is preferable that the window size calculating means calculates a value obtained by subtracting the payload length from the start time of the flow control instruction as the window size. Alternatively, it is preferable that the window size calculation means calculates the maximum window size as the window size when the flow control instruction is not given.

  The value of the maximum window size is set to 64 KB-1 if the data buffer capacity that can be received by the external application processing unit is 64 KB-1 or more. On the other hand, if the data buffer capacity receivable by the external application processing unit is less than 64 KB-1, the maximum window size value is set to the data buffer capacity receivable by the external application processing unit. .

  In the present invention, the receivable window size can be determined based on the capacity of the buffer for storing the payload.

(First embodiment)
A TCP receiving terminal device according to the first embodiment of the present invention will be described below with reference to FIGS. 1 and 2. As shown in FIG. 1, the TCP receiving terminal device 265_1 constitutes a part of the AV device 200 together with the application unit 300 and the CPU 710a. In the TCP receiving terminal device 265_1, in the TCP receiving terminal device 265a (FIG. 7), the TCP control unit 3a is replaced with the TCP control unit 3, and a maximum window size holding unit 700 and a window size calculating unit 701 are newly added. Has been.

  The maximum window size holding unit 700 is connected to the CPU 710a through a path C760. The CPU 710a is bidirectionally connected to the Almost_Full detection unit 102 of the application unit 300 through a path C761. The window size calculation unit 701 is connected to the maximum window size holding unit 700 and the Almost_Full detection unit 102 through a route C752 and a route C301, respectively.

  The window size calculation unit 701 is further bidirectionally connected to the TCP control unit 3 through a path C751. The TCP control unit 3 is basically configured by removing the TCP reception buffer 30 and the window size calculation unit 31 from the above-described TCP control unit 3a (FIG. 7), and is not included in the TCP control unit 3a. It has a function (described later).

The Almost_Full detector 102 monitors whether or not the amount of data buffered by the application buffer 101 has reached the threshold Th of Almost_Full via the path 300. That is, the Almost_Full detection unit 102
Based on the usage amount Vb of the application buffer 101, a signal indicating the state of whether or not the buffering data amount has reached the threshold value Th (hereinafter, “Almost_Full_st”) is used as a flow control instruction, and the window 301 is passed through the path 301. Notify the size calculation means 701.

  The CPU 710 a obtains a data size receivable by the application unit 300 based on the Almost_Full detection threshold Th by the Almost_Full detection unit 102. Based on the obtained data size, the CPU 710a determines the maximum window size Win_SZ (max). The CPU 710a sets the maximum window size Win_SZ (max) in the maximum window size holding unit 700 via the path C760.

  The maximum window size holding unit 6 constantly notifies the window size calculation unit 701 of the maximum window size Win_SZ (max) set via the path C752. The window size calculation unit 701 calculates the window size X based on the notified Win_SZ (max).

  If the maximum window size Win_SZ (max), that is, the data buffer capacity that can be received by the application buffer 101 is 64 KB-1 or more, a value of 64 KB-1 is set as the window size X. If the maximum window size Win_SZ (max) is less than 64 KB, the data buffer capacity of the application buffer 101 is set as the window size X.

  Next, TCP packet reception in the AV device 200 will be described. Before starting the reception of the TCP packet, the window size calculation unit 701 refers to Almost_Full_St input via the path C301 to determine the window size X1. The determined window size X1 is notified to the TCP control unit 3 via the path C751.

  The TCP control unit 3 reflects the window size X1 in the window size area of the TCP packet header Hp to generate a packet P200. The packet P200 is passed to the IP control unit 2 via the route C750. As described above, the packet P200 is transmitted to the home network 2000 via the route C202, the transmission / reception unit 1, and the route C201 after being subjected to transmission processing according to the IP protocol by the IP control unit 2.

  Thereafter, after the TCP transmission terminal device 260 receives the packet P200 via the home network 2000, the packets P210, 211, and 212 are transferred to the TCP control unit 3, and the payload data Dp is transferred from the TCP control unit 3 to the application buffer 101. The process up to being passed to is as described above. The TCP control unit 3 further calculates the payload / data length of a packet that is determined to be valid. The TCP control unit 3 passes the calculated payload data length PLD_LEN to the window size calculation unit 701 via the path C751.

  In the application unit 300, the application buffer 101 buffers the payload data Dp received from the path C205. The Almost_Full detection unit 102 generates Almost_Full_st based on the data amount (usage amount Vb) buffered by the application buffer 101 via the path C300, and sends it to the window size calculation unit 701 as a flow control instruction. The notification is as described above.

  The window size calculation unit 701 determines an appropriate window size X that can be received with reference to the flow control instruction (Almost_Full_st). Then, the determined window size X is notified as the above-described window sizes X1, X2, and X3 to the TCP transmission terminal device 260 that is a packet transmission source, thereby performing flow control of TCP packet transmission. .

  A method for calculating the window size X by the window size calculation unit 701 will be described below. Upon receiving PLD_LEN from the TCP control unit 3, the window size calculation unit 701 refers to Win_SZ (max) notified from the maximum window size holding unit 700 and Almost_Full_st notified from the application unit 300, and enters the state of Almost_Full_st. In response, the window size Cur_Win_SZ is calculated according to the rules described below.

<Rule 1>
When Almost_Full_St is 0, that is, when the usage amount Vb of the application unit 300 is less than the threshold Th, the application unit 300 (application buffer 101) can accept payload data Dp larger than the maximum window size Win_Sz (Max). . In this case, the window size Cur_Win_SZ is set as represented by the following equation (2).
Cur_Win_SZ = Win_SZ (max) (2)

<Rule 2>
When Almost_Full_St is 1, that is, when the usage amount Vb of the application unit 300 is equal to or greater than the threshold Th, the application unit 300 (application buffer 101) can receive payload data Dp with the maximum window size Win_Sz (Max) as an upper limit. is there. However, each time payload data Dp is received, the number of payload data Dp that can be accepted by the application unit 300 decreases. In this case, the window size Cur_Win_SZ is set as represented by the following equation (3).
Cur_Win_SZ = Win_SZ (max) −PLD_LEN (sum)
(3)
Note that PLD_LEN (sum) is a value obtained by accumulating PLD_LEN when the usage Vb of the application buffer 101 is equal to or greater than the threshold Th by Almost_Full_St.

Or it sets so that it may represent with following Formula (4).
Cur_Win_SZ = Old_Win_SZ-PLD_LEN
(4)
Note that Old_Win_SZ is the value of Cur_Win_SZ set in the previous round.

  In this manner, Cur_Win_SZ obtained by the window size calculation unit 701 is referred to as the window size X2 by the TCP control unit 3, and the confirmation response ACK 250 is generated. Thereafter, similarly, an acknowledgment ACK 251 is generated and data transmission / reception processing is performed.

  Next, a window size calculation method by the window size calculation unit 701 will be described with reference to FIG. In FIG. 2, the horizontal axis indicates time t, and each solid line indicates, from the top, the usage amount Vb of the application buffer 101, Almost_full_st of the Almost_Full detection unit 102, and the time of window size X set by the window size calculation unit 701. It represents the transition state for t. When the value of Almost_Full_st is 0, the usage amount Vb of the application buffer 101 is less than the threshold Th, and when it is 1, the usage amount Vb of the application buffer 101 is greater than or equal to the threshold Th.

  The value of Almost_Full_st maintains 0 from time t0 and becomes 1 at time t1. A period in which the value of Almost_Full_st from time t0 to time t1 is 0 is defined as F1. After time t1, the value of Almost_Full_st maintains 1 and becomes 0 again at time t3. Of the period in which the value of Almost_Full_st is 1, the period from time t1 to time t2 when the usage amount Vb of the application buffer 101 becomes maximum is F2, and the period from time t2 to time t3 when the value of Almost_Full_st becomes 0 again Is F3.

  In the period F1 in which Almost_Full_st is 0, the usage amount Vb of the application buffer 101 tends to increase but does not reach the threshold Th. Therefore, the window size X is the maximum window size Win_Sz (Max).

  In the period F2, since the usage amount Vb of the application buffer 101 exceeds the threshold Th, the value of Almost_Full_st becomes 1, and the window size X decreases. If the use amount Vb of the application buffer 101 increases, the window size X finally becomes 0 at time t2. At this time, the usage amount Vb of the application buffer 101 starts to decrease.

  In the period F3, new data is not accumulated in the application buffer 101, but the data already accumulated is read from the application buffer 101 and processed. Therefore, the application buffer usage Vb decreases from time t2 and reaches the threshold Th at time t3. Accordingly, Almost_Full_st becomes 0, and the window size X is set to the maximum window size Win_Sz (Max).

  Then, in response to the window size X (Win_Sz (max)) set at time t3, the buffering of the application buffer 101 is resumed, and the usage amount Vb again exceeds the threshold Th. Almost_full_st is also set to 1. As a result, the window size X decreases as in the period F2.

  As described above, the window size X of the acknowledgment ACK returned to the transmission source server 100 is controlled based on the usage amount Vb of the application buffer 101, and the flow control for the transmission source server 100 is performed. As a result, buffer overrun at the TCP receiving terminal 265 is prevented, and efficient data transmission becomes possible.

  Further, in the conventional TCP receiving terminal device, the window size X is determined based on the size of the receiving buffer buffered in units of packets. Therefore, in order to increase the window size X, it is necessary to increase the capacity of the reception buffer to be used. However, in the present invention, the window size X is determined based on the size of the application buffer that is buffered in units of payload data. In other words, it is required for flow control by the window size X and no reception buffer is required. Further, since the capacity required for the application buffer is smaller than the capacity required for the reception buffer, the buffer capacity in the TCP receiving terminal device can be minimized.

(Second Embodiment)
A TCP receiving terminal apparatus according to the second embodiment of the present invention will be described with reference to FIG. In the TCP receiving terminal device 265_2 in this example, the CPU 710a is replaced with a CPU 710b in the TCP receiving terminal device 265_1 shown in FIG. Accordingly, a path C301 that connects the window size calculation unit 701 to the Almost_Full detection unit 102 is removed, and a path C762 that connects the window size calculation unit 701 to the CPU 710b is provided.

  As a result, Almost_Full_st generated by the Almost_Full detection unit 102 is passed to the CPU 710b via the path C761, not the window size calculation unit 701. The CPU 710b generates a flow control signal Sc for the TCP transmission terminal device 260 based on Almost_Full_st. The flow control signal Sc is passed to the window size calculation unit 701 via the path C762. With this configuration, in the present embodiment, more precise flow control is possible by adding processing to Almost_Full_St that changes directly according to the usage amount Vb of the application buffer 101.

  That is, according to the present invention, the TCP receiving terminal device does not require a large-capacity TCP buffer, the buffer can be minimized, and the cost can be reduced. Furthermore, the window size can be flexibly adapted to the system requirements and the network environment, and no packet loss occurs in the buffer in the TCP receiving terminal device, so that it can be efficiently transmitted without applying a network load.

  The embodiment according to the present invention has been specifically described above by taking the TCP receiving terminal device using the TCP communication protocol as an example. However, these descriptions do not limit the scope of application of the present invention, and can be applied to other similar protocols that perform flow control.

  The present invention can flexibly deal with network transmission using a TCP communication protocol and a communication protocol that performs flow control similar to the TCP communication protocol. Specifically, it is useful for applications such as home appliances and mobile terminals connected to such networks.

The block diagram showing the structure of the TCP receiving terminal device concerning the 1st Embodiment of this invention Explanatory drawing of the calculation method of window size by the window size calculation part shown in FIG. The block diagram showing the structure of the TCP receiving terminal device concerning the 2nd Embodiment of this invention Streaming distribution network configuration diagram Data transmission sequence diagram using TCP communication protocol Explanatory drawing of packet header used for TCP communication protocol Block diagram showing an example of a configuration of a conventional TCP receiving terminal device A block diagram showing a further example of the configuration of a conventional TCP receiving terminal device Illustration of transmission performance of data transmission by TCP communication protocol

Explanation of symbols

NW streaming distribution network 100, 100_1, 100_2, 100_3 Server 1000 Internet 1004 Router 2000 Home network 200 AV equipment 200_1 Digital TV
200_2 Digital video recorder 200_3 Audio equipment 200_4 PC
260 TCP transmission terminal device 265a, 265b, 265_1, 265_2 TCP reception terminal device 300 Application unit 1 Transmission / reception unit 2 IP control unit 3, 3a, 3b TCP control unit 4 Payload output unit 30 TCP reception buffer 31 Window size calculation unit 101 Application Buffer 102 Almost_Full detection unit 401 Buffer amount estimation unit 402 RWIN control unit 700 Maximum window size holding unit 701 Window size calculation unit

Claims (6)

A receiving terminal device used for data transmission using a communication protocol that notifies a window size representing a receivable data size and performs flow control of data transmission to the transmitting terminal device,
Payload length detecting means for detecting the payload length of the data;
Maximum window size holding means for holding a pre-specified maximum window size;
A receiving terminal device comprising: a window size calculating unit that calculates the window size based on the maximum window size, the payload length, and a flow control instruction given from outside.   The receiving terminal device according to claim 1, wherein the communication protocol is a TCP protocol.   2. The receiving terminal device according to claim 1, wherein the window size calculating unit calculates a value obtained by subtracting the payload length from a start time of the flow control instruction as the window size.   4. The receiving terminal apparatus according to claim 3, wherein the window size calculating unit calculates the maximum window size as the window size when the flow control instruction is not given.   The value of the maximum window size is set to a value of 64 KB-1 if a data buffer capacity receivable by an external application processing unit is 64 KB-1 or more. Receiving terminal device.   The maximum window size value sets the data buffer capacity that can be received by the external application processing unit if the data buffer capacity that can be received by the external application processing unit is less than 64 KB-1. The receiving terminal device according to claim 1.