JP6891201B2 - Communication equipment, control methods and programs for communication equipment - Google Patents

Description

The present invention relates to a communication device capable of generating and transmitting a plurality of packets.

In network communication, communication by TCP (Transmission Protocol) / IP (Internet Protocol) is widely used. Since this TCP / IP is also used for large-capacity data communication such as uploading images and videos from terminals such as cameras and smartphones to a cloud server, it has been required in recent years to be able to communicate at a higher speed. There is.

In the TCP / IP protocol process for transmitting a packet to a communication counterpart, first, the user data specified by the send () call of the socket API from the application is transferred to the transmission buffer (network buffer). Next, the user data transferred and stored in the transmission buffer is typically cut out by MSS (Maximum Segment Size), which is a transmission unit of user data. A packet is generated by adding a TCP header, an IP header, or the like to the cut out user data (payload).

TSO (TCP Segmentation Offload) processing is one of the technologies for reducing the load on the CPU (Central Processing Unit) associated with the above TCP / IP protocol processing and speeding up the packet transmission processing.
In this TSO processing, the TCP / IP protocol processing for each packet based on the above MSS is not performed. That is, in the TSO processing, the user data transferred to the transmission buffer is read out in a size larger than the MSS which is the transmission unit, TCP / IP protocol processing is performed, and then the user data is divided into packet units based on the MSS to divide a plurality of packets. Is generated at once. By generating multiple packets by TSO processing, the TCP / IP protocol processing that was executed for each packet is reduced to one execution for each multiple packet, reducing the load on the CPU and packet transmission processing. Can be realized at high speed.

It is also possible to speed up the division process into a plurality of packets by offloading from the software process executed by the CPU to, for example, a hardware offloader mounted on a NIC (Network Interface Card).
Patent Document 1 discloses a TCP transmission control device capable of controlling whether or not to use TSO processing in units of TCP sessions (applications) depending on the presence or absence of packet loss and an application.

WO2010 / 0737671

By the way, the TCP protocol allows the addition of the TCP option header to the payload. However, when this TCP option header should be added to the payload, if it is simply divided into a plurality of packets based on the MSS, packets exceeding the maximum transfer unit MTU (Maximum Transmission Unit) may be generated. For example, when the payload size MSS is set to a value obtained by subtracting the TCP header and IP header sizes from the MTU which is the maximum transfer unit, the size of the entire IP packet is further added by adding the TCP option header. Exceeds MTU.

Since IP packets exceeding the MTU size in this way cannot be transmitted at one time, IP fragmentation processing is executed. That is, the IP packet exceeding the size of the MTU must be divided into a plurality of IP packets on the transmitting side and then transmitted, and the plurality of IP packets received on the receiving side must be reconstructed into the original IP packet.
The addition of such IP fragmentation processing on the transmitting side and the receiving side of the packet causes a decrease in communication throughput.

The present invention has been made in view of the above-mentioned problems, and an object of the present invention is to suppress a decrease in communication throughput and to transmit packets more efficiently.

In order to solve the above problems, the communication device according to the present invention is a header added to a packet transmitted by the communication device, and is an acquisition means for acquiring the header length of the header related to TCP (Transmission Control Protocol). A determination means for determining the payload length of the payload to be included in the packet based on the header length acquired by the acquisition means and the MSS (Maximum Segment Size) in the TCP connection for transmitting the packet, and at a predetermined timing. When the length of the transmission data to be transmitted by the communication device is longer than the payload length determined by the determination means, the first hardware is used to determine the payload length determined by the determination means. When the length of the transmission data is shorter than the payload length determined by the determination means, the first generation means for generating a plurality of packets including the payload is different from the first hardware. It has a second generation means for generating a packet using the hardware of the above .

According to the present invention, it is possible to suppress a decrease in communication throughput and transmit packets more efficiently.

A block diagram showing an example of the hardware and functional configuration of the communication device 1 according to the present embodiment. The figure which shows the configuration example of the large packet in the network buffer 34 of the communication apparatus 1 in Embodiment 1. The figure which shows an example of the sequence of the transmission / reception processing of a packet and ACK when the TCP option SACK (Selective ACK) is enabled. The figure which shows an example of the sequence of packet generation and transmission processing in communication apparatus 1. A flowchart showing an example of a detailed processing procedure of packet generation and transmission processing of the communication device 1 in the first embodiment. A flowchart showing an example of a detailed processing procedure of packet generation and transmission processing of the communication device 1 in the second embodiment. The figure which shows the configuration example of the large packet in the network buffer 34 of the communication apparatus 1 in Embodiment 2.

Hereinafter, embodiments for carrying out the present invention will be described in detail with reference to the accompanying drawings. The embodiment described below is an example as a means for realizing the present invention, and should be appropriately modified or changed depending on the configuration of the device to which the present invention is applied and various conditions. It is not necessarily limited to the embodiment. Moreover, not all combinations of features described in the present embodiment are essential for the means of solving the present invention. The same configuration will be described with the same reference numerals.

Hereinafter, an example in which the communication device executes a process of collectively generating a plurality of packets from the user data in the transmission buffer will be described. The process may be performed offload using, for example, TSO (TCP Transmission Offload).
Further, the header added to the transmission data at the time of packet generation may include a TCP header, an IP header, and an Ethernet (registered trademark) header. One or more of these TCp headers, IP headers, and Ether headers are hereinafter also referred to as protocol headers. The protocol header is a header processed in the communication protocol process. The IP header and TCP header are also collectively referred to as TCP / IP headers below.

(Embodiment 1)
<Hardware and functional configuration of this embodiment>
FIG. 1 is a diagram showing an example of a hardware configuration and a functional configuration of a communication device according to the present embodiment.
Of the functional modules of the communication device 1 shown in FIG. 1, for the functions realized by software, a program for providing the functions of the functional modules is stored in a memory such as a ROM and read into the RAM by the CPU. It is realized by executing. For the functions realized by the hardware, for example, by using a predetermined compiler, a dedicated circuit may be automatically generated on the FPGA from the program for realizing the functions of each function module. FPGA is an abbreviation for Field Programmable Gate Array. Further, a Gate Array circuit may be formed in the same manner as the FPGA and realized as hardware. Further, it may be realized by ASIC (Application Specific Integrated Circuit). The configuration of the functional blocks shown in FIG. 1 is an example, and a plurality of functional blocks may constitute one functional block, or any of the functional blocks may be divided into blocks that perform a plurality of functions. May be good.

The communication device 1 includes a main processing unit 2 and a communication processing unit 3. The main processing unit 2 executes the entire processing of the communication device 1 including various applications. The communication processing unit 3 executes various communication processes and controls including communication protocol processes such as TCP / IP. The main processing unit 2 and the communication processing unit 3 are interconnected by a bus bridge 4.

The main processing unit 2 includes a main CPU 21, a main memory 22, and a main bus 23.
The main CPU 21 executes various programs and controls the entire communication device 1. The program executed by the main CPU 21 includes an OS (Operating System) and various applications.
The main memory 22 stores data, programs, and the like necessary for the main CPU 21 and the sub CPU 31 of the communication processing unit 3 to execute each process. The main memory 22 may be composed of, for example, a semiconductor memory such as a DRAM (Dynamic Random Access Memory).

Inside the main memory 22, a user buffer 24 is configured by the main CPU 21, and user data is stored in the user buffer 24. The user buffer 24 is an area accessible from the sub CPU 31 as well as the main CPU 21 via the bus bridge 4 and the main bus 23. The user data stored in the user buffer 23 includes data that the main CPU 21 wants to send from the application of the communication device 1 to the communication opposite device via the network 5. Hereinafter, the user data is also referred to as transmission data or simply data.
The main bus 24 is used for access and data transfer from the main CPU 21 to the main memory 22 and the communication processing unit 3, access and data transfer from the communication processing unit 3 to the main memory 22 and the like.

The communication processing unit 3 includes a sub CPU 31, an on-chip memory 33, a data transfer unit 35, a packet generation unit 36, a LAN control unit 37, a WLAN control unit 38, and a local bus 39.
The sub CPU 31 executes programs related to various communication processes. The program executed by the sub CPU 31 includes an OS and a communication protocol stack for communication protocol processing. In the present embodiment, an example in which the TCP / IP protocol stack is executed as the communication protocol process will be described, but other protocol stacks may be used.
The sub CPU 31 includes a payload size determining unit 32.

The on-chip memory 33 is, for example, an internal memory configured in an ASIC or FPGA. The on-chip memory 33 is a memory that can be accessed from the sub CPU 31, the data transfer unit 35, and the packet generation unit 36 of the communication processing unit 3. The on-chip memory 33 may be composed of a semiconductor memory such as a SRAM (Static Random Access Memory), for example, so that the on-chip memory 33 can be accessed at a higher speed than the main memory 22. Further, the on-chip memory 33 may be a memory device configured on a NIC (Network Interface Card).

Inside the on-chip memory 33, a plurality of network buffers 34 are configured by the sub CPU 31. These network buffers 34 are transmission buffers used when the sub CPU 31 processes data transmitted / received to / from the communication opposing device.
The network buffer 34 is dynamically acquired in the on-chip memory 33 at the timing when the transmission buffer is needed, and is released when the data transmission process is completed and is no longer needed. Further, each of the network buffers 34 has a data area and a next buffer area. An address (pointer) of another network buffer is specified in the next buffer area in each network buffer 34. As a result, it is possible to concatenate a plurality of network buffers and pass transmission data larger than the size of each network buffer 34 to the packet generation unit 36. Details of the network buffer 34 will be described later with reference to FIG.

The data transfer unit 35 can execute various data transfers according to instructions from the main CPU 21, the sub CPU 31, and the packet generation unit 36. The data transfer unit 35 transfers, for example, the data stored in the main memory 22 to the packet generation unit 36 or the on-chip memory 33. In addition, all or a part of the processing executed by the data transfer unit 35 may be implemented in DMAC (Direct Memory Access Controller) and executed offload.

The packet generation unit 36 packetizes the user data (payload) stored in the network buffer 34 based on the large packet input from the sub CPU 31 to execute the plurality of packet generation processes. The large packet is large-sized transmission data input from the sub CPU 31 to the packet generation unit 36, which can concatenate and store a plurality of network buffers 34.

First, the packet generation unit 36 generates a plurality of headers for a plurality of packets based on the TCP / IP header information input from the sub CPU 31 and stored in the first network buffer 34 constituting the large packet. To do. Specifically, the packet generation unit 36 generates a plurality of headers by duplicating the TCP / IP header of the large packet stored in the first network buffer 34 and rewriting the fields having different values for each packet.

For example, the IP address information and the port number information in the header are duplicated with the values in the TCP / IP header of the large packet, but the TCP sequence number is rewritten by the packet generation unit 36. This is because the TCP sequence number included in the large packet is the sequence number of the first packet, so the sequence numbers of the next and subsequent packets are calculated from each payload size of the divided packets.
The plurality of headers generated by the packet generation unit 36 may be stored in the built-in memory of the packet generation unit 36, or may be stored in the network buffer 34 acquired for header storage on the on-chip memory 33. The sub CPU 31 generates a plurality of packets to be transmitted to the network via the packet generation unit 36 by concatenating the generated header and the transmission data (payload) on the network buffer 34 corresponding to each header. ..

All or part of the processing executed by the packet generation unit 36 can be implemented in an offloader of TSO (TCP Transmission Offload) and executed offload. This TSO may be implemented as a hardware offloader on the NIC, for example.
The local bus 39 interconnects the functional blocks of the communication processing unit 3 and connects to the main bus 23 via the bus bridge 4.

The LAN (Local Area Network) control unit 37 is a wired communication interface that connects to the network 5, and executes transmission / reception of packets. The LAN control unit 37 includes a hardware circuit of a PHY layer and a MAC layer (transmission media control) of a transmission medium. For example, when the interface of the LAN control unit 37 is Ethernet (registered trademark), the LAN control unit 37 corresponds to an Ethernet (registered trademark) NIC (Network Interface Card).
The WLAN (Wireless LAN) control unit 38 is a wireless communication interface connected to the network 5 and executes transmission / reception of packets. The WLAN control unit 38 includes a controller that executes wireless LAN control such as IEEE802.11a / b / g / n / ac and an RF (Radio Frequency) circuit.
The plurality of packets generated by the packet generation unit 36 and the sub CPU 31 are passed to communication control units such as the LAN control unit 37 and the WLAN control unit 38, and are sent to the network 5.

<Payload size determination process>
The payload size determination unit 32 of the sub CPU 31 determines the data division size when dividing a large packet into a plurality of packets based on the size of the option header of the TCP / IP protocol of the packet to be transmitted from now on.
Specifically, the payload size determination unit 32 determines the size obtained by excluding the size of the TCP option header from the MSS (Maximum Segment Size) as the data division size. The MSS is the maximum value of the transmission unit (segment) of user data set when establishing a communication session such as a TCP session, that is, the maximum segment size that can be transmitted in the TCP session. Normally, this MSS is notified by the TCP option when the connection is established as the maximum value of the segment that the device can receive from the communication opposite device.

The sub CPU 31 generates input information for causing the packet generation unit 36 to execute a plurality of packet generation processes. The sub CPU 31 also inputs information on the TCP / IP header to the packet generation unit 36 for the packet generation unit 36 to generate a plurality of TCP / IP headers to be added to each of the plurality of packets by duplication.
In the present embodiment, the input information input for causing the packet generation unit 36 to divide the packet is referred to as a large packet. By generating this large packet by concatenating a plurality of network buffers 34 and inputting it to the packet generation unit 36, it is possible to generate a plurality of packets in which one large packet is divided via the packet generation unit 36. it can.

FIG. 2 shows a configuration example of a large packet configured by the sub CPU 31 on the network buffer 34 of the on-chip memory 33 of the communication device 1.
The large packet has a TCP / IP packet configuration in which a payload for a plurality of packets to be transmitted is concatenated with a set of TCP headers and IP headers corresponding to the payload.

As shown in FIG. 2, the large packet is stored in an area in which a plurality of network buffers NB1 to NB4 are concatenated. The network buffer NB1 in which the TCP / IP header is stored and the network buffers NB2 to NB4 in which each payload is stored are separate buffers. A plurality of network buffers NB1 to NB4 are concatenated by setting the address of the next buffer to be concatenated to the buffer in the area of the next buffer provided in each network buffer NB1 to NB4.
The network buffers NB1 to NB4 do not necessarily have to be arranged in a continuous area on the on-chip memory 33. Further, although four network buffers NB1 to NB4 are shown in FIG. 2, the number of network buffers is not limited to four, and the number of network buffers is appropriately increased based on the user data length to be transmitted, connection information, and the like. May be determined.

TCP / IP headers (IP header and TCP header) are stored in the first network buffer NB1. The TCP option header is also stored in the first network buffer NB1. In FIG. 2, the option header of the SACK (Selective ACK) block is stored as the TCP option header continuous with the TCP / IP header.
The information included in the TCP / IP header of the large packet is a value corresponding to the first packet when the large packet is divided into a plurality of packets. Further, each of the plurality of payloads (payloads 1 to 3) in the large packet is stored in each network buffer NB2 to NB4 with the data division size determined by the payload size determination unit 32 as the maximum value.

The large packet shown in FIG. 2 includes a payload for three packets. The payload 1 and the payload 2 have a size corresponding to the data division size determined by the payload sizing unit 32. On the other hand, the payload 3 has a size less than the data division size determined by the payload size determination unit 32.

The SACK block shown as the TCP option header in FIG. 2 is one of the TCP option headers added before the payload when the TCP option SACK (Selective ACK) is enabled. A normal ACK that responds to data transmission notifies that all data up to the ACK number has been received, while an ACK (SACK) with SACK enabled notifies that data has been partially received. can do. Data retransmission efficiency can be improved by enabling the SACK option and transmitting a data reception acknowledgment by SACK.

FIG. 3 shows an example of a data reception and ACK transmission sequence when the TCP option SACK is supported and enabled on both the transmit and receive sides.
Five consecutive transmission data (Seq = 100, 200, 300, 400) are transmitted from the data transmission side device 311 to the opposite data reception side device 312, of which the transmission data (Seq = 300) is the data reception side device 312. Is not reached.
On the other hand, it is assumed that the data receiving side device 312 transmits SACK (Ack = 300, SLE = 400, SRE = 500) when SACK is valid.
In this case, the data transmitting side device 311 need only retransmit the data of Seq = 300, and it is not necessary to retransmit the subsequent data of Seq = 400 already received by the data receiving side device 312. Therefore, the retransmission efficiency is improved as compared with having to retransmit the data of Seq = 300 and Seq = 400 when SACK is invalid.

When SACK is enabled, a SACK block as a TCP option header to be added to the packet is added, but the size of this SACK block (SACK block length) is variable depending on the data reception status of the data receiving side device 312. is there. Specifically, since the SACK block length is calculated in 4 + 8 * n (n = 1 to 4) bytes, the size of the TCP option header varies from +12 bytes to +36 bytes.
Therefore, since the SACK block, which is a TCP option header, is added, the size of the entire IP packet may exceed the MTU (Maximum Transmission Unit), which is the maximum transfer unit on the network.

For example, when the MTU size is 1500 bytes, it is assumed that the MSS size is 1460 bytes obtained by subtracting 40 bytes of the TCP / IP packet length. In this case, if the payload is separated by the MSS size, the TCP option header of the SACK block is added to the TCP / IP packet, so that the size of the entire IP packet exceeds the MTU and IP fragmentation occurs. That is, an IP packet exceeding the MTU size must be divided into a plurality of IP packets on the transmitting side and then transmitted, and the plurality of IP packets received on the receiving side must be reconstructed into the original IP packet. , It causes a decrease in communication throughput.
In the present embodiment, the payload size determining unit 32 of the sub CPU 31 determines the payload size so that such IP fragmentation does not occur.

In the above description, the payload size determination unit 32 subtracts the SACK block length from the MSS to determine the data division size based on the SACK block length as the TCP option header. Not limited to. For example, the payload size determination unit 32 may calculate the header length of the TCP option header other than the SACK block to determine the data division size, or calculate the header length of the IP option header to determine the data division size. You may. For example, the payload size determination unit 32 can determine the data division size based on the header length of the hop-by-hop routing header as the IPv6 option header.

<Example of packet generation and transmission processing sequence of communication device 1>
FIG. 4 shows an example of a transmission processing sequence in which the communication device 1 generates and transmits a packet to the communication opposite device via the network 5.
In S41, the main CPU 21 stores user data in the user buffer 24 in the main memory 22.
In S42, the main CPU 21 calls send (), which is a socket API, as a request for transmitting user data from the application.
When the call of send () is executed in S42, the sub CPU 31 starts the data transfer process for packet transmission. First, the user data is copied from the user buffer 24 to the network buffer 34.

In order to execute copying of the user data to the network buffer 34, in S43, the sub CPU 31 first transfers the network buffer 34 of the size required for user data transmission from the area for the network buffer 34 of the on-chip memory 33. Acquire. When a plurality of buffers are acquired, the acquired plurality of buffers are all concatenated by setting the address of the next buffer in the next buffer area of the buffer information.
In S44, the sub CPU 31 requests the data transfer unit 35 to copy (transfer) the user data from the user buffer 24 to the acquired network buffer 34.
In S45, the data transfer unit 35 requested to copy the user data reads the user data from the user buffer 24 and transfers the user data by dividing the user data into each buffer area in the network buffer 34 in order to generate a large packet.

When the data transfer to the network buffer 34 in S45 is completed, the data transfer unit 35 notifies the sub CPU 31 of the completion of data transfer of the user data in S46.
When the completion of data transfer of the user data to the network buffer 34 is notified, in S47, the sub CPU 31 determines the transmission size of the user data to be transmitted from now on.
In the communication in the TCP protocol, the connection is different for each application communicating, and the window size, MSS, data reception status from the communication opposite device, etc. are managed for each connection.

In the present embodiment, the sub CPU 31 manages each connection, and the connection information of each connection is stored in the main memory 22.
In S47, the sub CPU 31 compares the transmission window size and the congestion window size obtained by referring to the connection information with the size of the user data copied to the network buffer 34 in S45, and determines the smallest size as the transmission size.
In S48, the sub CPU 31 starts the generation process of a plurality of packets.

Specifically, first, the payload size determination unit 32 in the sub CPU 31 determines the data division size when the packet generation unit 36 collectively generates a plurality of packets from the user data.
The payload size determination unit 32 determines the data division size from the size of the TCP option header and the MSS by referring to the connection information of the connection to which the plurality of generated packets should be transmitted.
The payload size determination unit 32 refers to the connection information, and if the TCP SACK option is valid, confirms the data reception status from the communication opposite device and calculates the SACK option length.
As described above, the SACK option is a TCP option that notifies the communication partner of the received data section by a parameter such as an Ac number when the transmission data from the communication partner is partially received. Since the communication partner who has received the SACK only needs to retransmit the data other than the data section notified by the SACK, the retransmission efficiency can be improved.

The payload size determination unit 32 determines in S48 the size obtained by subtracting the SACK option length from the MSS as the data division size. The sub CPU 31 divides the transmission data by the data division size determined by the payload size determination unit 32 to generate a large packet which is input information to be input to the packet generation unit 36.
In S49, the sub CPU 31 acquires the network buffer 34 for storing the header to be generated by the packet generation unit 36 from the network buffer 34.
The data area of the network buffer 34 acquired for storing the header in S49 may be limited to a size smaller than the data area of the network buffer 34 for storing the user data acquired in S43.

In S50, the sub CPU 31 requests the packet generation unit 36 to perform a plurality of packet generation processes. The multiple packet generation process may be executed by the TSO process. This request for multiple packet generation processing is executed by designating a large packet to the packet generation unit 36, while when a normal packet is generated in S48, the request for multiple packet generation to the packet generation unit 36 is executed. Not executed.
The sub CPU 31 further generates information on the TCP / IP header for the large packet and passes it to the packet generation unit 36 as information for causing the packet generation unit 36 to generate the TCP / IP header by duplication. In the present embodiment, the information of the TCP / IP header for this large packet includes, for example, the information of the SACK block as the above-mentioned TCP option header.
After setting the information necessary for packet generation, in S50, the sub CPU 31 makes a packet generation request to the packet generation unit 36.

In S51, the packet generation unit 36 divides the large packet set from the sub CPU 31 in S50, generates a plurality of TCP / IP headers from the information of the TCP / IP header for the passed large packet, and generates a plurality of TCP / IP headers. Generate a packet.
Specifically, the packet generation unit 36 has a large header field such as a source, a destination IP address, a destination, and a destination port number that does not change between a plurality of packets among the information required for header generation. Generate a header by duplicating the packet header.

On the other hand, the packet generation unit 36 changes the contents of header fields that change between a plurality of packets, such as the checksum in the IPv4 header, the datagram length, the sequence number in the TCP header, and the checksum, from the header of the large packet. The TCP / IP header information for the large packet generated by the sub CPU 31 is also referred to as a template header.
In the present embodiment, the plurality of TCP / IP headers generated by the packet generation unit 36 by duplicating the header of the large packet are TCP option headers (SACK block) similar to the header of the large packet shown in the network buffer NB1 of FIG. )including. By redundantly adding the SACK block, which is a TCP option header, to all of a plurality of packets, the reliability of data transmission / reception can be improved even when the communication environment is poor.

In S52, the packet generation unit 36 instructs the data transfer unit 35 to store the generated plurality of headers in the area of the network buffer 34 acquired in S49. The data transfer unit 35 stores a plurality of headers instructed to be stored in the network buffer 34.
When the generated plurality of headers are stored in the network buffer 34, the data transfer unit 35 notifies the packet generation unit 36 of the completion of storage (writing) of the generated plurality of headers in the network buffer 34 in S53. To do.

When notified of the completion of storage of the plurality of headers in the network buffer 34, the packet generation unit 36 updates the buffer information in order to concatenate each generated header and each corresponding payload to generate a packet. To do. Specifically, the packet generation unit 36 can form one packet by setting the address in which the payload is stored in the next buffer address of the network buffer 34 in which the header is stored. The same process is repeatedly executed for the number of packets. As a result, a plurality of packets are generated. The above process of generating a plurality of packets from a plurality of headers may be executed by the sub CPU 31 in whole or in part instead of the packet generation unit 36.
In S54, the packet generation unit 36 notifies the sub CPU 31 that the generation of the plurality of headers has been completed.

When the generation of the plurality of packets is completed in S54, the sub CPU 31 starts the packet transmission process in S55.
In S56, the sub CPU 31 notifies the WLAN control unit 38 of a transmission request in which a plurality of packets are concatenated.
The WLAN control unit 38 notified of the transmission request of a plurality of packets reads a plurality of packets (packet group) stored in the network buffer 34 in S57 and transmits the plurality of packets (packet group) to the network 5.

In S58, when the WLAN control unit 38 completes the transmission of all the packets, the WLAN control unit 38 notifies the sub CPU 31 of the completion of the packet transmission. Although the example in which the WLAN control unit 38 transmits the packet has been described above, the LAN control unit 37 may similarly transmit the packet instead.
The above processes S47 to S58 correspond to a series of a plurality of packet generation and transmission processes. The processes S47 to S58 are repeated until all the user data copied to the network buffer 34 is transmitted.
When all the user data copied to the network buffer 34 is transmitted as a packet, in S59, the sub CPU 31 notifies the main CPU 21 of a response indicating that the send () call is successful.

<Packet transmission processing flow of communication device 1>
FIG. 5 is a flowchart showing an example of a processing procedure of packet transmission processing executed and controlled by the sub CPU 31 of the communication device 1 in the present embodiment. The process shown in FIG. 5 corresponds to the processes S43 to S58 shown in FIG. The packet transmission process of FIG. 5 may be started, for example, when an application instructs to transmit user data, but the packet transmission process is not limited to this.
In S501, the sub CPU 31 starts the packet transmission process and copies the user data from the user buffer 24 to the network buffer 34 by being called from the application via the execution of the socket API send () (FIG. 4). Corresponds to S43 to S46).

In S502, the sub CPU 31 determines the transmission size to be transmitted from the user data copied to the network buffer 34 (corresponding to S47 in FIG. 4).
In S503, the sub CPU 31 refers to the connection information of the TCP connection used in send () from the application, and determines whether or not the SACK option is enabled in the TCP connection. The setting of the SACK option is determined when the connection is established, and it can be determined whether the connection is enabled or disabled by referring to the connection information of the connection.

If the SACK option is enabled (S503: Y) in the TCP connection, the process proceeds to S504, while if the SACK option is disabled (S503: N), S504 is skipped and the process proceeds to S505.
In S504, the sub CPU 31 calculates the SACK block length added to the TCP header. SACK is used when the data received from the communication opposite device is discontinuous, the SACK block length is variable, and up to four SACK blocks can be added to the TCP header.
Even if the SACK option is valid, the SACK length is 0 when there is no SACK block to be added, such as when the data received from the communication opposite device is continuously received.

In S505, the payload size determination unit 32 of the sub CPU 31 calculates the data division size. The data division size can be calculated by subtracting the SACK block length calculated in S504 from the MSS set in the TCP connection used in send (). For a TCP connection for which the SACK option is invalid, the value set in the MSS of the TCP connection may be used as the data division size as it is.

In S506, the sub CPU 31 compares the transmission size determined in S502 with the data division size calculated in S505.
If the transmission size is larger than the data division size (S506: Y), the process proceeds to S507 to generate a large packet. On the other hand, when the transmission size is less than or equal to the data division size (S506: N), that is, when it is less than or equal to the payload length delimited by the data division size, it branches to S508 to generate a normal packet and proceeds to S510. In S508, the user data corresponding to the transmission size determined in S502 is used as the payload, and the sub CPU 31 generates a normal packet by adding the TCP / IP header corresponding to the payload without going through the packet generation unit 36. To do.

When the transmission size is larger than the data division size in S506, the sub CPU 31 generates a large packet based on the data division size in S507.
Specifically, the sub CPU 31 uses the user data corresponding to the transmission size determined in S502 as a payload, and generates and adds a TCP / IP header corresponding to this payload to generate a large packet. The TCP header added to the large packet in S506 includes a SACK option header (SACK block).
The transmission size is the total length of the payload of the large packet, and the entire payload is divided by each of the plurality of network buffers 34 by the data division size (payload size) calculated in S505 as shown in FIG. Generated.

In S509, the sub CPU 31 inputs the large packet generated in S507 to the packet generation unit 36, and causes a batch generation process of a plurality of packets to be executed by, for example, a TSO process. The packet generation unit 36 duplicates the TCP / IP header added to the large packet generated in S507 by the sub CPU 31 by the number of the plurality of packets to be generated. The TCP / IP header containing the SACK option is duplicated and added to each of the plurality of packets.
In S510, the sub CPU 31 transmits either a plurality of packets generated in S509 or a normal packet generated in S508 to the outside via, for example, the WLAN control unit 38.
In S511, the sub CPU 31 determines whether or not there is untransmitted user data in the user data copied to the network buffer 34 in S501. When untransmitted user data exists in the network buffer 34 (S511: Y), the process returns to S502 and the packet transmission processing from S502 to S511 is executed. On the other hand, when all the user data copied to the network buffer 34 in S501 is transmitted, the packet transmission process is terminated.

In the flow of FIG. 5, after starting the packet transmission process, the transmission SACK block length is calculated every time the packet generation process is executed in S504. However, in the present embodiment, after the transmission SACK block length to be added to the packet to be generated first is calculated once, the transmission SACK block length may be fixed and used without calculating the transmission SACK block length each time. Good.
Specifically, the data division size is calculated by subtracting the maximum value of the SACK block length (for example, 36 bytes) from the MSS only at the time of the first packet generation processing, and the data division size calculated at the first time is used. To generate a large packet. In the second and subsequent packet generation processes, the data division size calculated at the first time may be used without recalculating the data division size. By omitting the calculation of the data division size from the second time onward and simplifying the large packet generation process, the load related to the packet transmission of the sub CPU 31 can be reduced and the packet transmission can be speeded up.

As described above, according to the present embodiment, when a plurality of packets are collectively generated, even if the TCP option header length is added, a packet having an appropriate payload size in which the occurrence of IP fragmentation is effectively prevented can be obtained. Can be generated.

(Embodiment 2)
Hereinafter, the second embodiment will be described in detail only with reference to FIGS. 6 and 7 and different from the above-described first embodiment. In the first embodiment, the same data division size was calculated for each of the plurality of packets generated by the packet generation unit 36. On the other hand, in the second embodiment, the payload size is calculated in consideration of the transmission SACK block length for the first packet, and the SACK block, which is a TCP option header, is added to the TCP / IP header for the first packet. On the other hand, for the second and subsequent packets, the large packet is separated by MSS and generated as a payload, and the SACK block, which is a TCP option header, is not added to the TCP / IP header.

The hardware configuration and functional configuration of the communication device 1 according to the second embodiment are the same as those of the first embodiment shown in FIG.
The packet generation and transmission processing executed by the communication device 1 according to the second embodiment is the same as that of the first embodiment shown in FIG.

FIG. 6 is a flowchart showing an example of a detailed processing procedure of packet generation and transmission processing controlled by the sub CPU 31 of the communication device 1 in the present embodiment.
Each process of S501 to S504 is the same as each process of S501 to S504 of the first embodiment shown in FIG.
After calculating the transmission SACK length to be added as the TCP option header in S504, the sub CPU 31 of the communication device 1 calculates the data division size for the payload at the beginning of the large packet in S601, and proceeds to S506. The specific calculation method is the same as the data division size calculation method calculated by the sub CPU 31 in S505 of FIG. 5 in the first embodiment. However, in the present embodiment, the data division size calculated in S601 is applied only to the payload at the beginning of the large packet.

The processing of S506 is the same as the processing of S506 of the implementation mobile phone 1 shown in FIG.
When it is determined in S506 that the transmission size determined in S502 is larger than the data division size calculated in S601 (S506: Y), in S602, the sub CPU 31 generates a large packet header and a head payload.

In the present embodiment, the sub CPU 31 generates a TCP / IP header that does not include the SACK block, which is a TCP option header, in the network buffer 34 for the header.
On the other hand, the sub CPU 31 first generates a SACK block, which is a TCP option header, in the network buffer 34 for the head payload. In addition to this SACK block, the sub CPU 31 divides the user data for the data division size for the head payload determined in S601 from the user data to be transmitted and generates it as a payload.

The network buffer 34 for the header is connected to the network buffer 34 for the head payload by designating the address (pointer) of the network buffer 34 for the head payload in the next buffer area of the network buffer 34 for the header.
In S603, the sub CPU 31 generates the second and subsequent payloads of the large packet. For these second and subsequent payloads, user data (large packets) are separated by MSS for each network buffer 34 to generate packets.
The network buffer 34 for the first payload and the network buffer 34 for the second and subsequent payloads are also concatenated by designating the address of the next network buffer 34 to the next buffer area. The generation of large packets is completed by generating packets separated by MSS for all the remaining user data to be transmitted.

FIG. 7 shows an example of the configuration of a large packet generated in the network buffer 34 through the processes of S602 and S603.
With reference to FIG. 7, a TCP / IP header that does not include a TCP option header is generated in the network buffer NB1 for the header. The network buffer NB2 for the first payload stores the SACK block, which is a TCP option header, and the payload 1 separated by the data division size for the first payload.
On the other hand, the payload 2 and the payload 3 separated by the MSS are stored in the second network buffer NB3 and the third network buffer NB4, respectively.

Returning to FIG. 6, in S509, the sub CPU 31 inputs the large packet generated in S603 to the packet generation unit 36, and causes the batch generation process of a plurality of packets to be executed.
The packet generation unit 36 generates a header (TCP / IP header) generated by the sub CPU 31 in S602. Therefore, in the present embodiment, the packet generation unit 36 duplicates the TCP / IP header that does not include the SACK block, which is the TCP option header, and adds it to each packet. As a result, only the network buffer 34 (NB1 in FIG. 7) of the first payload is added with the SACK block, which is a TCP option header, following the TCP / IP header. On the other hand, the SACK block, which is a TCP option header, is not added to the network buffer 34 of the payload other than the beginning.
Each process of S508 to S511 is the same as the process of S508 to S511 shown in FIG.

As described above, according to the present embodiment, when a plurality of packets are collectively generated, the SACK block is added only to the first packet, and the SACK block length is taken into consideration for the second and subsequent packets. User data can be separated by a long MSS. Therefore, the second and subsequent packets can be generated with a longer payload length while effectively preventing the occurrence of IP fragmentation, so that the throughput of packet transmission is improved. In addition, the load of SACK reception processing on the packet receiving side is also reduced.

The present invention can also be realized by a program that realizes a part or one or more functions of the above-described embodiment. That is, it can be realized by supplying the program to the system or device via a network or storage medium, and reading and executing the program by one or more processors in the computer (or CPU, MPU, etc.) of the system or device. is there. Further, the program may be recorded and provided on a computer-readable recording medium.
Further, the function of the embodiment is not limited to the one realized by executing the program read by the computer. For example, the operating system (OS) running on the computer may perform a part or all of the actual processing based on the instruction of the program, and the function of the above-described embodiment may be realized by the processing.

1 ... Communication device, 2 ... Main processing unit, 3 ... Communication processing unit, 4 ... Bus bridge, 5 ... Network, 21 ... Main CPU, 22 ... Main memory, 23 ... Main bus, 24 ... User buffer, 31 ... Sub CPU , 32 ... payload size determination unit, 33 ... on-chip memory, 34 ... network buffer, 35 ... data transfer unit, 36 ... packet generation unit, 37 ... LAN control unit, 38 ... WLAN control unit, 39 ... local bus

Claims (16)

It ’s a communication device,
A header added to a packet transmitted by the communication device, and an acquisition means for acquiring the header length of the header related to TCP (Transmission Control Protocol).
A determination means for determining the payload length of the payload to be included in the packet based on the header length acquired by the acquisition means and the MSS (Maximum Segment Size) in the TCP connection for transmitting the packet.
When the length of the transmission data to be transmitted by the communication device at a predetermined timing is longer than the payload length determined by the determination means, it is determined by the determination means using the first hardware. A first generation means for generating a plurality of packets including a payload of the payload length, and
When the length of the transmission data is shorter than the payload length determined by the determination means, the second generation means for generating the packet using the second hardware different from the first hardware. ,
A communication device characterized by having. The communication device according to claim 1, wherein the header length is a length determined based on a reception status of data transmitted from another communication device via the TCP connection. The communication device according to claim 1, wherein the determination means determines the payload length when the TCP connection is established. The communication device according to any one of claims 1 to 3, wherein the header length is the header length of the TCP option header. The communication device according to claim 4, wherein the TCP option header is a header for the SACK (Selective ACK) option of TCP. The communication device according to claim 4 or 5, wherein the determination means determines the payload length by subtracting the header length of the TCP option header from the MSS. The determination means is characterized in that the payload length is determined so that the packet length obtained by adding the TCP header to the payload of the payload length determined by the determination means does not exceed the MTU (Maximum Transmission Unit). Item 2. The communication device according to any one of Items 1 to 5. A dividing means for dividing transmission data based on the payload length determined by the determining means, and a dividing means.
An input means for inputting transmission data divided by the dividing means to the first generation means, and
With more
The communication device according to any one of claims 1 to 7, wherein the first generation means generates a plurality of packets using the divided transmission data input by the input means. .. The communication device according to claim 8, wherein the first generation means uses the divided transmission data to generate a plurality of packets including a payload having the payload length. The first generation means according to claim 8, wherein the divided transmission data is used to generate a packet including a payload having the payload length and a packet including the payload of the MSS. Communication device. It also has a transmit buffer with multiple areas
The communication device according to any one of claims 8 to 10, wherein the dividing means stores each of the divided transmission data in each of the plurality of regions. It further has a third generation means of generating a plurality of TCP / IP headers by duplicating a predetermined TCP / IP (Internet Protocol) header.
The first generation means according to any one of claims 1 to 11, wherein a plurality of packets are generated by using the plurality of TCP / IP headers generated by the third generation means. The communication device described. The communication device according to any one of claims 1 to 12, further comprising a transmission means for transmitting a packet generated by the first generation means via the TCP connection. The communication device according to any one of claims 1 to 13, wherein the determination means uses the second hardware to determine the payload length of the payload to be included in the packet. A control method for a communication apparatus which have a the first hardware and second hardware,
A step of acquiring the header length of a header related to TCP (Transmission Control Protocol), which is a header added to a packet transmitted by the communication device, and
A step of determining the payload length of the payload to be included in the packet based on the acquired header length and the MSS (Maximum Segment Size) in the TCP connection for transmitting the packet.
When the length of the transmission data to be transmitted by the communication device at a predetermined timing is longer than the determined payload length, the first hardware is used to include the payload of the determined payload length. Steps to generate multiple packets and
When the length of the transmitted data is shorter than the determined payload length, a step of generating a packet using the second hardware different from the first hardware, and a step of generating a packet.
A method of controlling a communication device, which comprises. Computer program to function as each unit of the communication apparatus according to any one of claims 1 1 4.

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