JP2001345854A - Method, system and apparatus for packet communication between networks - Google Patents

Abstract

(57) [Summary] In a network environment using a gateway device, even when a protocol having a session concept in an application layer and a protocol without a connection concept in a transport layer are used, command contents of the application layer are grammatically analyzed one by one. Provided are a packet communication method, system, and apparatus for efficiently performing packet relay processing by detecting session establishment and cancellation without analysis. A terminal device (10) includes a protocol stack (1).
3 is provided with a hierarchy (pseudo-connection layer) in which a connection can be described.
The in flag is set, and at the end of the session, the fin flag is set in the last packet to be issued, and the gateway device 20 is notified of the start and end of the session.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method and apparatus for packet communication between networks, and more particularly, to a terminal apparatus existing on one network and another terminal apparatus in a communication environment having two networks. A packet communication method for establishing a session with a server device existing on a network via a gateway device that relays between the two networks, a server-client system using the method, and each device .

[0002]

2. Description of the Related Art (Description of Network Model) An example of a model in which a protocol is modularized for each function is an OS.
A reference model of I (Open Systems interconnection) is generally cited. In the OSI reference model, communication functions are divided into seven layers, and standard function modules are defined for each layer. FIG. 13 is a diagram showing a seven-layer model of OSI. In FIG. 13, the first layer (physical layer)
Is responsible for electrical conversion and mechanical work for sending data to the communication line. Layer 2 (data link layer)
Secures a physical communication path with a communication partner and performs error detection and the like on data flowing through the communication path. The third layer (network layer) selects a communication path for delivering data to a communication partner and manages addresses (addresses) in the communication path. The fourth layer (transport layer) performs data compression, error correction, retransmission control, and the like for reliably and efficiently delivering data to a communication partner. The fifth layer (session layer) establishes and releases a virtual path (connection) for transmitting and receiving data between communication programs. The sixth layer (presentation layer) converts data received from the fifth layer into a format that is easy for the user to understand, and converts data sent from the seventh layer into a format suitable for communication. Seventh
The layer (application layer) provides various services using data communication to humans and other programs.

(Description of TCP / IP) Similar to the above-described OSI seven-layer model, another layered model of the network includes a TCP / IP (Transmission Control Protocol).
ol / Internet Protocol) There is a hierarchical model of the Internet. FIG. 14 is a diagram showing a hierarchical model of the TCP / IP Internet. FIG. 15 is a diagram that very roughly compares the OSI seven-layer model and the TCP / IP Internet layer model. In FIG. 14, the layer model of the TCP / IP Internet is composed of four conceptual layers, and each layer is called as follows. The uppermost application layer passes a message sequence and a byte stream transmitted and received from the application program to the next layer, the transport layer. The transport layer manages communication between the application program and other programs, and corresponds to approximately the fourth and fifth layers in the OSI seven-layer model (FIG. 1).
5). The transport layer guarantees that data arrives in order without error, and divides the data into packet units and passes the data to the Internet layer. The internet layer encapsulates the packet passed from the transport layer into an IP datagram and passes it to the appropriate network interface layer. The lowest network interface layer receives the IP datagram from the Internet layer and passes it to the hardware.

[0004] In the two general network protocol hierarchies described above, the respective hierarchies provide their respective functions, and the data output by a certain hierarchy on the transmission side and the data received by the same hierarchy on the reception side are different from each other. But are designed to be the same. For example, in the communication between the hosts shown in FIG. 16, the application layer of the host B is designed to receive the same message as the message transmitted from the application layer of the host A.

[0005] TCP, which is a typical protocol of the transport layer, establishes a connection to perform communication between hosts in order to check that data can be transmitted and received correctly. TCP is designed so that data can be correctly transmitted and received between hosts by communicating data retransmission, acknowledgment, and the like using this connection. In IP, which is a typical protocol of the Internet layer, data is exchanged in packet units. Here, since the packets are transmitted individually and independently, their order and duplication are not checked.
P is designed so that transmission and reception between hosts can be performed in an accurate format in packet units.

[0006] As described above, the communication between the hosts is finally realized by the protocol of each layer transmitting and receiving data based on the respective functions.

(Explanation of Literal Script Notation Protocol) As an example of a so-called literal script notation protocol that allows a person to read and understand the meaning of a sequence as it is, RTSP (Real Time Stroke) is used.
eaming Protocol) and HTTP (Hyper Text Transfer Pro)
tocol) and the like. As an example, FIG.
The state of protocol transmission and reception in P is schematically shown. In the example of FIG. 17, V
A series of procedures from setup and playback of the video and audio streams are shown.

[0008] RTSP is a protocol being developed to effectively transmit data in a stream format over an IP network. RTSP is TCP /
This is a protocol of an application layer in the hierarchical structure of the IP Internet, and establishes one or a plurality of time-synchronized continuous media streams and controls reproduction and stop. This RTSP does not carry continuous stream data itself, but is a network remote control protocol for multimedia servers. RTSP
There is no concept of connection in itself, and generally, after establishing a connection between a server device and a terminal device in a lower transport layer, a user can be uniquely specified by an identifier thereon. "session"
Logical connection state. FIG. 18 schematically shows a state of connection and session establishment using an example of a TCP protocol stack. Note that R
A detailed sequence regarding the establishment and cancellation of the TSP session will be described later in an embodiment of the present invention.

[0009] Similarly to the RTSP, there is HTTP as a protocol of the application layer. HTTP is an Internet-based WWW (World Wide Web) service in which a WWW server sends an HTTP to a WWW client.
This is a communication protocol for transmitting and receiving a document described in ML (Hyper Text Markup Language). In the HTTP, an HTML document and files such as images, sounds, and moving images associated with the document can be exchanged, including information such as an expression format.

[0010] HTTP is a very simple protocol consisting of a request and a response, and the request and the response are independent communication units. First, W
The WW client wants to display the WW
Transmits the URL (Uniform Resource Locators) path name of the W page. On the other hand, the WWW server transmits its own HTML document to the WWW client. For example, when a WWW client accesses a certain WWW server and completes the connection, and the WWW client transmits a command “GET /”, <HEAD><TITLE>. . . . . </ TITLE>: </ BODY>, as a response from the WWW server,
The data described in L is returned.

[0011] As described above, even in HTTP, like RTSP, communication is performed based on the concept of a session in which a logical connection is made to a WWW server every time data is acquired, and the logical connection is cut off when data transmission and reception are completed.

[0012]

When a server device and a terminal device exist on different networks, a gateway device is generally used to relay the two devices. FIG. 19 shows an example of a system constructed using the gateway device. In the system of FIG. 19, when RTSP or the like having a logical connection state called a session without a concept of connection is used for a protocol of an application layer, a gateway device performs connection between devices performed in a lower transport layer. By detecting the establishment and disappearance of the session, it was possible to simultaneously detect (recognize) the establishment and disappearance of the session.

However, due to various restrictions of the communication system,
RTSP with the concept of a session in the application layer
Protocol such as UDP (for example, UDP (User Datagram)
Protocol)). In this case, since there is no connection between the devices, the gateway device shown in FIG. 19 needs to grammatically analyze the contents of commands such as RTSP one by one in order to know the establishment and disappearance of the session. Further, as described above, in the protocol such as RTSP, a literal script notation is used to describe a command sequence, which is convenient for humans to read and understand. But the computer is RT
In order to interpret a protocol such as SP, a number of processes that impose a heavy load on the CPU, such as binarization by LEX or the like and character string comparison, must be performed. Execution of such processing causes a reduction in communication efficiency.

Therefore, an object of the present invention is to provide a network environment using a gateway device, in which a protocol having a concept of a session in an application layer and a protocol having no concept of a connection in a transport layer are used. An object of the present invention is to provide a packet communication method, system, and apparatus capable of detecting establishment and cancellation of a session without performing grammatical analysis of command contents one by one and performing packet relay processing efficiently.

[0015]

Means for Solving the Problems and Effects of the Invention A first invention is directed to one or more terminal devices connected to a first network and one or more server devices connected to a second network. And a gateway device connected to the first and second networks and relaying packet communication between the two devices.
In the packet communication method, when a session that is a logical connection state for transmitting and receiving a message in a hierarchical communication protocol is established between a terminal device and a server device, the terminal device issues first. The leading packet is set to a specific part in the leading packet with a begin flag indicating the start of the session, transmitted to the gateway device, and the gateway device determines the start of the session by detecting the begin flag in the received leading packet. Then, when establishing a communication path with the server device and transferring the head packet to the server device to cancel the session established between the terminal device and the server device, the terminal device issues the last packet issued last. By setting a fin flag indicating a session end in a specific portion of the last packet, Transmitting to the gateway device, the gateway device determines the end of the session by detecting a fin flag in the received final packet, and cancels the session after receiving a response to the final packet from the server device. .

As described above, according to the first aspect, when a session is established between the terminal device and the server device,
A begin flag is added to the packet issued first from the terminal device, and the gateway device is notified of the start of the session. When ending a session already established, a fin flag is added to the last packet issued from the terminal device to notify the gateway device of the end of the session. This allows the gateway device to:
Even if a protocol with the concept of session in the application layer and a protocol without the concept of connection in the transport layer are used, the establishment and cancellation of the session can be detected without analyzing the command contents of the application layer one by one, and packet Relay processing can be performed efficiently.

According to a second aspect of the present invention, there is provided at least one terminal device connected to a first network, at least one server device connected to a second network, and at least one terminal device connected to the first and second networks. A packet communication method in a server-client system comprising a gateway device that is connected and relays packet communication between the two devices, for transmitting and receiving a message in a hierarchical communication protocol between a terminal device and a server device. When establishing a session that is a logical connection state, the terminal device transmits the first packet to be issued first to the gateway device by setting a begin flag indicating a session start in a specific portion of the first packet. , The gateway device,
The start of the session is determined by detecting the begin flag in the received first packet, a communication path with the server device is established, and the first packet is transferred to the server device.
When canceling the session established between the terminal device and the server device, based on the reception of the last packet issued last by the terminal device, the server device generates a response packet corresponding to the last packet in the response packet. Set the fin flag indicating the end of the session in the specific part,
The session is transmitted to the gateway device, and the gateway device detects the fin flag in the received response packet, determines the end of the session, and cancels the session.

As described above, according to the second aspect, when a session is established between the terminal device and the server device,
A begin flag is added to the packet issued first from the terminal device, and the gateway device is notified of the start of the session. When ending a session that has already been established, a fin flag is added to the last packet issued from the server device, and the gateway device is notified of the end of the session. Thus, even when the gateway device uses a protocol having a concept of a session in the application layer and a protocol without a concept of a connection in the transport layer, it establishes and establishes a session without analyzing the command content of the application layer one by one. Cancellation can be detected, and packet relay processing can be performed efficiently.

A third invention is an invention according to the first and second inventions, wherein the gateway device holds information on the established communication path and performs packet communication after the first packet in accordance with the information. It is characterized by.

A fourth invention is an invention according to the third invention, wherein the gateway device cancels the session by deleting the information on the communication route.

As described above, according to the third and fourth aspects, the gateway device establishes a session between the terminal device and the server device based on the detection of the begin flag, and establishes a communication path for the session. Information is held, and the session is canceled by deleting the information based on the detection of the fin flag. As a result, it is possible to easily and quickly execute packet communication after the first packet.

A fifth invention is an invention according to the first invention, wherein a communication protocol of a session layer on the first network is a protocol expressed in a literal script.

A sixth invention is an invention according to the second invention, wherein the communication protocols of both session layers on the first and second networks are both protocols in a literal script notation. Features.

In the case of the communication protocol as in the fifth and sixth aspects, the most effect can be exhibited by using the packet communication method according to the first and second aspects.

According to a seventh aspect of the present invention, there is provided one or more terminal devices connected to the first network, one or more server devices connected to the second network, and the first and second networks. A server / client system comprising a gateway device connected to relay packet communication between the two devices, wherein the server / client system is in a logical connection state for transmitting and receiving messages in a hierarchical communication protocol with the server device. When a session is established, a begin flag indicating the start of a session is set in a specific portion of the first packet issued first, and when a session established with the server device is canceled, the last packet in the last packet issued last is set. A fin flag indicating the end of the session is set in a specific portion, and the packet is transmitted to the gateway device. And end devices, beg in the first packet
The start of the session is determined by detecting the in flag, the communication path with the server device is established, the first packet is transferred to the server device, and the end of the session is determined by detecting the fin flag in the last packet. A gateway device for canceling the session after receiving a response to the final packet from the server device.

According to an eighth aspect of the present invention, there is provided one or more terminal devices connected to the first network, one or more server devices connected to the second network, and one or more terminal devices connected to the first and second networks. A server / client system comprising a gateway device connected to relay packet communication between the two devices, wherein the server / client system is in a logical connection state for transmitting and receiving messages in a hierarchical communication protocol with the server device. When a session is established, a begin flag indicating the start of a session is set in a specific portion of the first packet issued first, and a session established between the terminal device that transmits the packet to the gateway device and the terminal device In order to eliminate the last packet, the terminal device responds to the last packet based on the last packet issued last. A fin flag indicating the end of the session is set in a specific part of the response packet to be transmitted, and the server device transmitting the packet to the gateway device, and detecting the begin flag in the first packet to determine the start of the session, A gateway device that establishes a communication path with the device, transfers the head packet to the server device, detects the fin flag in the response packet, determines the end of the session, and cancels the session.

A ninth invention is a terminal device connected via a first network to a gateway device connected to one or more server devices via a second network, wherein the terminal device is connected to the server device. In order to establish a session which is a logical connection state for message transmission and reception in a hierarchical communication protocol, a specific part in the first packet issued first indicates the session start be
a setting unit for setting a gin flag; and a transmitting unit for transmitting a leading packet with the begin flag set to the gateway device.

A tenth invention is a terminal device connected via a first network to a gateway device connected to one or more server devices via a second network, wherein the terminal device is connected to the server device. When establishing a session that is a logical connection state for message transmission and reception in a layered communication protocol, a specific portion in the first packet issued first indicates a session start b
a setting unit for setting an egin flag, and a setting unit for setting a fin flag indicating the end of the session in a specific part of a last packet to be issued last, in order to cancel a session established between the server device and the begin flag. And a transmitting unit that transmits the first packet in which the fin flag is set or the last packet in which the fin flag is set to the gateway device.

An eleventh invention is a server device connected via a second network to a gateway device connected to one or more terminal devices via a first network, wherein the server device is connected to the terminal device. A setting unit for setting a fin flag indicating the end of the session in a specific portion in a response packet to the last packet based on the reception of the last packet issued last by the terminal device when canceling the established session; And a transmission unit for transmitting a response packet in which the response packet is set to the gateway device.

[0030] A twelfth invention is a gateway device connected to one or more terminal devices via a first network and one or more server devices via a second network. A transmission unit that determines a session start by detecting a flag indicating a session start in a packet transmitted from the server, establishes a communication path with the server device, and transfers the packet to the server device, and a packet subsequent to the packet. In order to perform communication according to the information on the established communication path, the storage unit holding the information and the flag indicating the session end in the packet transmitted from the terminal device or the server device determine the session end by detecting the session end flag. And a processing unit for deleting the information on the communication path after completing the corresponding packet transmission to cancel the session. That.

A thirteenth invention is a invention according to the ninth and tenth inventions, wherein the communication protocol of the session layer on the first network is a protocol expressed in a literal script. .

A fourteenth invention is according to the eleventh invention, wherein the communication protocol of the session layer on the second network is a protocol in a literal script notation.

[0033] A fifteenth invention is an invention according to the twelfth invention, which is performed on the first network or in the first network.
The communication protocol of both session layers on the second network and the second network are both literal scripts.

As described above, the seventh to fifteenth inventions are the inventions in which the packet communication method according to the first to sixth inventions is applied to a server / client system, a terminal device, a server device, and a gateway device. Thereby, the first to first
A server-client system, a terminal device, a server device, and a gateway device that achieve the useful effects of the present invention described in the sixth invention can be realized.

[0035]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Hereinafter, a packet communication method, system and apparatus provided by the present invention will be described in a server-client system in which communication between a terminal device and a server device is performed via a gateway device. RT which is a script notation protocol
The case where the SP is used will be described as an example. The application layer may use another literal script protocol such as HTTP, a mail control protocol IMAP4, or the like.

(First Embodiment) FIG. 1 shows a first embodiment of the present invention.
It is a figure showing the composition of the server client system concerning an embodiment. FIG. 1 schematically shows a network connection and a protocol stack of the system. FIG. 2 is a diagram schematically showing a state in which a communication path between the first network 51 and the second network 52 has been established using the address conversion lookup table 22 of FIG.

In FIG. 1, the server / client system according to the first embodiment includes a plurality of terminal devices 10,
It includes a gateway device 20, a plurality of server devices 30, and a file system 40. First network 5
Reference numeral 1 denotes a connectionless network using UDP, which connects each terminal device 10 and the gateway device 20. As the first network 51, other than the implementation on the UDP, another connectionless network (for example, WDP or WTP) used for a mobile phone can be used. The second network 52
This is a connection-type network using TCP, and connects the gateway device 20 and each server device 30.

The terminal device 10 comprises a memory device 11 storing a control program, a CPU 12, a protocol stack 13, and a socket 14. The pseudo connection layer of the protocol stack 13 has a flag (hereinafter, referred to as a begin flag) 15 added to the first packet of communication to notify the start of the session and a flag (added to the last packet of communication to notify the end of the session). Hereinafter, an area for storing the fin flag 16) is secured. This pseudo connection layer is called begin
To place the flag 15 and the fin flag 16, RT
This can be regarded as an area where the payload for storing the SP command is partially extended. Gateway device 2
0 indicates that the protocol stack 21 and U
A lookup table 22 for address conversion for performing DP-TCP conversion, a TCP socket generation unit 23 for establishing a TCP connection, a socket 24 having a port number on the first network 51, and a 2 created on network 52 of socket 2
5 The server device 30 includes a protocol stack 31, a socket 32 having a port number on the second network 52, and a packet generation protocol stack for transmitting desired content data from the file system 40 in which the content data is stored. 33
Consists of

Hereinafter, referring to FIGS. 3 to 5, in the server / client system according to the first embodiment, one of the plurality of terminal devices 10 is replaced with one of the plurality of server devices 30.
Next, a series of sequences from establishing an RTSP session to ending the session will be described.

FIG. 3 is a sequence diagram showing an example in which the terminal device 10 issues a SETUP command to establish a session with the server device 30. In FIG.
As an internal operation of the terminal device 10 at the time of issuing the SETUP command, the CPU 12
At the same time as writing the SETUP script in the P layer, the begin flag 15 indicating the start of the session is displayed in the pseudo connection layer.
Is set. In this state, the terminal device 10 changes the predetermined port number (fixed value depending on the design of the terminal device) from the socket 14 to the predetermined port number of the gateway device 20 (determined by the communication protocol. In the case of RTSP, , Socket 554)
4, the packet of the SETUP command with the begin flag (the first packet) is transferred. Note that the terminal device 1
It is assumed that a mechanism for compensating for packet loss in the first network 51 is implemented between 0 and the gateway device 20 by the function of the retransmission processing layers of the protocol stacks 13 and 21.

The gateway device 20 that has received the packet of the SETUP command with the begin flag is
The start of the session is detected by the begin flag without parsing the command of “SETUP” of the SP layer, and the operation for establishing a communication path for transferring the received packet to the server device 30 is started. At this time, the gateway device 20 uses the TCP socket generation unit 23 to select the IP address of the server device 30, generate a new TCP socket 25, and generate the generated TCP socket 25.
And a predetermined port number (RTS
In the case of P, a connection is established with the socket 32 (generally number 554). And the gateway device 20
Sets the established TCP connection (the file descriptor number of the socket) and the IP address of the terminal device 10 (hereinafter referred to as the terminal IP address) as a set, and uses the address conversion path as the address conversion reference table 22.
(FIG. 2). The registered address conversion path (hereinafter, referred to as an entry) can be searched from the terminal IP address and the TCP socket.

In the present embodiment, it is assumed that one terminal device 10 establishes only one session with the server device 30, so that the correspondence between sessions and entries is one-to-one. . In addition, one terminal device 10 is 2
When establishing one or more sessions, an entry for each session is prepared in the address conversion lookup table 22 of the gateway device 20, and a field for session identification is provided in the pseudo connection layer of the terminal device 10 for each session. I just need. Further, in the present embodiment, an example has been described in which only the terminal IP address and the TCP socket are registered as entries, but other information such as a port number and the terminal device 1
If 0 is a telephone, additional information such as a telephone number may be registered together.

When the address translation path is generated as described above, the server 30
To the SETUP command packet. After receiving this packet, the server device 30 obtains the URL and prepares to transmit the stream, and then returns a packet (OK packet) describing an OK acknowledge in the RTSP layer of the protocol stack 31 to the terminal device 10. This OK packet is sent to the gateway device 20 through the above-described TCP connection. In the gateway device 20, the lookup table 22 for address conversion is
By searching in the CP socket 25, the terminal IP address is extracted. After that, the gateway device 20
Using the terminal IP address and the port number of the terminal device, the address conversion shown in the protocol stack 21 is performed, and the OK packet is transferred to the terminal device 10. Thus, the sequence of the SETUP command is completed.

FIG. 4 is a sequence diagram showing an example of packet transfer when the terminal device 10 issues a command other than SETUP or TEARDDOWN, for example, a command such as PLAY. As shown in FIG.
Since the address translation path has already been determined in the processing of the TUP command (FIG. 3), the gateway device 20 searches the address translation lookup table 22 (terminal IP address).
Address conversion is performed quickly only by searching for a TCP socket based on an address), and a packet such as a PLAY command is transferred from the terminal device 10 to the server device 30.

FIG. 5 shows that the terminal device 10 is in the TEARDOWN state.
FIG. 14 is a sequence diagram illustrating an example of a case where a command is issued to end a session established with the server device 30. In FIG. 5, as an internal operation of the terminal device 10 at the time of issuing the TEARDOWN command, the CPU 12
TEARDOW is added to the RTSP layer of the protocol stack 13.
At the same time as writing the script of N, the fin flag 16 indicating the end of the session is set in the pseudo connection layer. In this state, the terminal device 10 transfers the TEARDOWN command packet (final packet) with the fin flag from the socket 14 having the predetermined port number to the socket 24 having the port number of the gateway device 20.

The gateway device 20 that has received the TEARDOWN command packet with the fin flag is
An end mark is added in order to detect the end of the session by the fin flag without parsing the command “TEARDOWN” of the TSP layer and to delete the entry of the session registered in the lookup table 22 for address translation. (FIG. 2). The addition of the end mark may be performed by ON / OFF of a flag or the like.
After that, the TEARDOWN command packet is transferred to the server device 30 through the TCP connection for the present session according to the entry registered in the address conversion reference table 22. After receiving the packet, the server device 30 performs a process of stopping the transmission of the stream, and thereafter, a packet (OK packet) describing an OK acknowledge in the RTSP layer of the protocol stack 31.
Is returned to the terminal device 10.

This OK packet is sent to the gateway device 20 through the above-mentioned TCP connection. In the gateway device 20, the terminal IP address is extracted by searching the reference table for address conversion 22 with the TCP socket 25. At that time, since the end mark is added to the address translation path entry,
At this point, the data of this entry is deleted from the address conversion lookup table 22. Thereafter, the gateway device 20 performs an address conversion using the terminal IP address and the port number of the terminal device, and sends an O to the terminal device 10.
Transfer K packets. Thereby, TEARDOWN
Upon completion of the command sequence, the terminal device 1
The session between 0 and the server device 30 is canceled.

FIG. 6 is a flowchart showing an example of the operation of the gateway device 20 for realizing the packet communication method already described with reference to FIGS. First, the gateway device 20 determines whether or not any packet has been received (step S601). If the packet has been received, the packet is transmitted to the terminal device 10 or the server device 3.
It is determined from which of the two packets the packet was transmitted (step S602). If it is determined in step S602 that the packet is transmitted from the terminal device 10,
The gateway device 20 checks whether a begin flag or a fin flag is added to this packet (steps S603 and S604). As a result of this check,
When the begin flag is added, the gateway device 20 generates a new TCP connection with the server device 30 (step S605), and transmits the generated TCP connection and the terminal IP address of the terminal device 10 to the address. It is registered as a new entry in the conversion reference table 22 (step S606). Then, the gateway device 20 sets the address conversion lookup table 22
The address is converted according to the entry of the session registered in the server, and the received packet is transferred to the server device 30 (step S608). When the fin flag is added, the gateway device 20 adds an end mark to the entry of the session already registered in the address conversion reference table 22 (step S607), and performs the address conversion according to the entry. Then, the received packet is transferred to the server device 30 (step S608). On the other hand, the begin flag or fin
If none of the flags is added, the gateway device 20 performs address translation according to the entry of the session already registered in the address translation lookup table 22, and transfers the received packet to the server device 30 (step S608). ).

On the other hand, if it is determined in step S 602 that the packet is transmitted from the server device 30, the gateway device 20 performs address translation according to the entry already registered in the address translation lookup table 22 and receives the packet. The packet is transferred to the terminal device 10 (Step S609). At this time, the gateway device 20 determines whether or not an end mark has been added to the entry of the present session (step S610). If the end mark has been added, the registered entry is deleted. This session is canceled (step S611).

As is well known to those skilled in the art, generally, a relay thread dedicated to packet transfer is constructed in the gateway device 20 for each session established. Therefore, in practice, the gateway device 20 prompts the packet transfer process to the terminal device 10 or the server device 30 by issuing a signal to the corresponding relay thread together with the information of the terminal IP address and the pointer of the received buffer. Is performed (steps S608 and S609). In general, socket identification and packet source confirmation are generally
This is performed using a select function, a sockopt function, or the like.

As described above, according to the server / client system according to the first embodiment of the present invention, when a session is established between a terminal device and a server device, a packet first issued from the terminal device is used. To the gateway device to notify the gateway device of the start of the session. When ending a session that has already been established, the last packet issued from the terminal device
By adding an n flag, the gateway device is notified of the end of the session. And in the gateway device, beg
Based on the detection of the in flag, a session between the terminal device and the server device is established, and transfer path information (entry) relating to the session is held, and fi
The session is canceled by deleting the entry based on the detection of the n flag. This allows the gateway device to:
Even if a protocol with the concept of session in the application layer and a protocol without the concept of connection in the transport layer are used, the establishment and cancellation of the session can be detected without analyzing the command contents of the application layer one by one, and packet Relay processing can be performed efficiently.

(Second Embodiment) FIG. 7 shows a second embodiment of the present invention.
It is a figure showing the composition of the server client system concerning an embodiment. FIG. 7 schematically shows the network connection and the protocol stack of the system. FIG. 8 is a diagram schematically showing a state in which a communication path between the first network 101 and the second network 102 has been established using the address conversion lookup table 72 of FIG.

In FIG. 7, the server / client system according to the second embodiment includes a plurality of terminal devices 60,
A gateway device 70, a plurality of server devices 80, and a file system 90 are provided. First network 1
The first and second networks 102 are both connectionless networks based on UDP, and connect each terminal device 60 and the gateway device 70 to the gateway device 7.
0 and each server device 80 are connected. This first
The other network 101 and the second network 102 include other connectionless networks (for example, W
DP or WTP) can be used.

The terminal device 60 comprises a memory device 61 storing a control program, a CPU 62, a protocol stack 63, and a socket 64. Also, the pseudo connection layer of the protocol stack 63 has a “begi” added to the first packet of the communication to notify the start of the session.
An area for storing the n flag 65 is secured. This pseudo connection layer can be regarded as an area in which the payload for storing the RTSP command is partially extended in order to arrange the begin flag 65. The gateway device 70 includes a protocol stack 71, an address conversion reference table 72 for performing UDP-to-UDP conversion at the time of packet relay, a UDP socket generation unit 73, and a socket 74 having a port number on the first network 101. And a socket 75 generated on the second network 102 each time a session is established. The server device 80 includes a memory device 84 storing a control program, a CPU 85, a protocol stack 81,
It comprises a socket 82 having a port number on the second network 102, and a packet generation protocol stack 83 for transmitting desired content data from the file system 90 storing the content data. In the pseudo connection layer of the protocol stack 81, an area for storing a fin flag 86 added to the last packet of the communication to notify the end of the session is secured. This pseudo connection layer can be regarded as an area in which the payload for storing the RTSP command is partially extended in order to arrange the fin flag 86.

Hereinafter, referring to FIGS. 9 to 11, in the server / client system according to the second embodiment, one of the plurality of terminal devices 60 establishes an RTSP session with one of the plurality of server devices 80. Then, a series of sequences up to the end of the session will be described.

FIG. 9 is a sequence diagram showing an example in which the terminal device 60 issues a SETUP command to establish a session with the server device 80. In FIG.
As an internal operation of the terminal device 60 at the time of issuing the SETUP command, the CPU 62
At the same time as writing the SETUP script in the P layer, the begin flag 65 indicating the start of the session is displayed in the pseudo connection layer.
Is set. In this state, the terminal device 60 transmits the predetermined port number (fixed value depending on the design of the terminal device) from the socket 64 to the predetermined port number of the gateway device 70 (in general, 554 in the case of RTSP).
No.) to socket 74 with a begin flag
The UP command packet (head packet) is transferred.
In addition, between the terminal device 60 and the gateway device 70,
It is assumed that a mechanism for compensating for packet loss in the first network 101 is implemented by the function of the retransmission processing layers of the protocol stacks 63 and 71.

The gateway device 70 that has received the packet of the SETUP command with the begin flag is
The start of the session is detected by the begin flag without interpreting the command “SETUP” of the SP layer, and the operation for establishing a communication path for transferring the received packet to the server device 80 is started. At this time, the gateway device 70 selects the IP address of the server device 80 by using the UDP
A P socket 75 is generated. Further, the gateway device 70 transmits the generated file descriptor number of the UDP socket 75 and the IP address of the terminal device 60 (terminal IP address).
The address conversion path is registered in the address conversion reference table 72 (FIG. 8). The registered address conversion path (entry) is stored in the terminal I
It is possible to search from both the P address and the UDP socket.

In the present embodiment, it is assumed that one terminal device 60 establishes only one session with the server device 80, so that there is a one-to-one correspondence between sessions and entries. . Note that one terminal device 60 is 2
When establishing one or more sessions, an entry for each session is prepared in the address conversion reference table 72 of the gateway device 70, and a field for session identification is provided in the pseudo connection layer of the terminal device 60 for each session. I just need. Further, in the present embodiment, an example has been described in which only the terminal IP address and the UDP socket are registered as entries, but other information such as a port number, a terminal device 6
If 0 is a telephone, additional information such as a telephone number may be registered together.

When the address translation path is generated as described above, the generated UDP socket is directed to the socket 82 of a predetermined port number (in the case of RTSP, generally number 554) of the server device 80. The packet of the SETUP command is transferred. Note that the gateway device 7
0 and the server device 80, a protocol stack 71
And 81, a mechanism for compensating for packet loss in the second network 102 is assumed to be implemented.

After receiving the packet from the gateway device 70, the server device 80 prepares for the acquisition of the URL and the transmission of the stream.
A packet in which an OK acknowledgment is described in the SP layer (OK packet) is returned to the terminal device 60. This OK packet is sent to the gateway device 70 by following the communication path when the SETUP command packet was received in the reverse direction. In the gateway device 70, the terminal IP address is extracted by searching the address conversion reference table 72 with the UDP socket 75. Thereafter, using the terminal IP address and the port number of the terminal device, the gateway device 70 performs address conversion indicated in the protocol stack 71 and transfers an OK packet to the terminal device 60. Thus, the sequence of the SETUP command is completed.

FIG. 10 shows a case where the terminal device 60 issues a command other than SETUP or TEARDDOWN, for example, PLAY.
FIG. 9 is a sequence diagram illustrating an example of packet transfer when a command such as a command is issued. As shown in FIG. 10, since the address conversion path has already been determined in the processing of the above SETUP command (FIG. 9), the gateway device 7
In the case of 0, the address is quickly converted only by searching the lookup table for address conversion 72 (searching the UDP socket based on the terminal IP address), and a packet such as a PLAY command is transferred from the terminal device 60 to the server device 80.

FIG. 11 shows that the terminal device 60
FIG. 17 is a sequence diagram illustrating an example of issuing an N command to end a session established with a server device 80. In FIG. 11, first, a TEARDOWN command is issued from the terminal device 60, and reaches the server device 80 via the gateway device 70.
This is exactly the same operation as the case of the PLAY command in FIG.

The server device 80 that has received the TEARDOWN command packet causes the CPU 85 to send the OPER for TEARDOWN to the RTSP layer of the protocol stack 81.
At the same time as writing the K acknowledge, the fin flag 86 indicating the end of the session is set in the pseudo connection layer. Next, after performing the process of stopping the stream transmission, the server device 80 traces the generated packet describing the OK acknowledgment (OK packet) in the reverse direction on the communication path at the time of receiving the TEARDOWN command packet, and returns to the terminal It is returned to the device 60. The gateway device 70 that receives the OK packet with the fin flag in the middle of returning the packet,
Without interpreting the acknowledgment “OK” of the RTSP layer, the end of the session is detected by the fin flag without grammatical interpretation. Thereafter, the gateway device 70 performs address conversion using the terminal IP address and the port number of the terminal device, and transfers an OK packet to the terminal device 60. As a result, the session between the terminal device 60 and the server device 80 is canceled at the same time when the sequence of the TEARDOWN command is completed.

FIG. 12 is a flowchart showing an example of the operation of the gateway device 70 for realizing the packet communication method already described with reference to FIGS.
First, the gateway device 70 determines whether or not any packet has been received (step S1201), and if so, determines whether the packet is transmitted from the terminal device 60 or the server device 80. (Step S1202). If it is determined in step S1202 that the packet is transmitted from the terminal device 60, the gateway device 70
It is checked whether an egin flag is added (step S1203). If the result of this check is that the begin flag has been added, the gateway device 70 generates a new UDP socket with the server device 80 (step S1204), and the generated UDP socket and the terminal IP of the terminal device 60. The address is registered as a new entry in the address conversion reference table 72 (step S1205). And the gateway device 7
0 performs address conversion according to the entry of the present session registered in the address conversion reference table 72, and transfers the received packet to the server device 80 (Step S).
1206). On the other hand, when the begin flag is not added, the gateway device 70 performs the address conversion according to the entry of this session already registered in the address conversion reference table 72, and transfers the received packet to the server device 80 (step S1206).

On the other hand, if it is determined in step S 1202 that the packet is transmitted from the server device 80, the gateway device 70 performs address translation according to the entry already registered in the address translation lookup table 72, and receives the packet. The packet is transferred to the terminal device 60 (step S1207). At this time, the gateway device 70 checks whether the fin flag is added to the received packet (step S1208),
If the fin flag is added, the registered entry is deleted to cancel the session (step S1209).

As is well known to those skilled in the art, generally, a relay thread dedicated to packet transfer is constructed in the gateway device 70 for each session established. Therefore, in practice, the gateway device 70 issues a signal to the corresponding relay thread together with the information of the terminal IP address and the pointer of the received buffer, thereby prompting the packet transfer process to the terminal device 60 or the server device 80. Is performed (steps S1206 and S1207). Also, the determination of the socket and the confirmation of the source of the packet are generally performed using a select function, a sockopt function, or the like.

As described above, according to the server / client system according to the second embodiment of the present invention, when a session is established between a terminal device and a server device, a packet first issued from the terminal device is used. To the gateway device to notify the gateway device of the start of the session. When ending the already established session, the packet issued last from the server
An in flag is added to notify the gateway device of the end of the session. And in the gateway device, be
Based on the detection of the gin flag, a session between the terminal device and the server device is established, and transfer path information (entry) relating to the session is held.
The session is canceled by deleting the entry based on the detection of the in flag. Thus, even when the gateway device uses a protocol having a concept of a session in the application layer and a protocol without a concept of a connection in the transport layer, it establishes and establishes a session without analyzing the command content of the application layer one by one. Cancellation can be detected, and packet relay processing can be performed efficiently.

[Brief description of the drawings]

FIG. 1 is a diagram showing a configuration of a server / client system according to a first embodiment of the present invention.

FIG. 2 is a diagram schematically showing an address conversion lookup table 22 of FIG. 1;

FIG. 3 is a sequence diagram when a SETUP command is issued in the first embodiment.

FIG. 4 is a sequence diagram when a PLAY command is issued in the first embodiment.

FIG. 5 is a sequence diagram when a TEARDOWN command is issued in the first embodiment.

FIG. 6 is a flowchart showing an example of the operation of the gateway device 20 of FIG.

FIG. 7 is a diagram showing a configuration of a server / client system according to a second embodiment of the present invention.

8 is a diagram schematically showing an address conversion lookup table 72 of FIG. 7;

FIG. 9 is a sequence diagram when a SETUP command is issued in the second embodiment.

FIG. 10 is a sequence diagram when a PLAY command is issued in the second embodiment.

FIG. 11 is a sequence diagram when a TEARDOWN command is issued in the second embodiment.

12 is a flowchart showing an example of the operation of the gateway device 70 of FIG.

FIG. 13 is a diagram showing a seven-layer model of OSI.

FIG. 14 is a diagram showing a hierarchical model of the TCP / IP Internet.

FIG. 15 is a diagram comparing an OSI seven-layer model with a TCP / IP Internet layer model.

FIG. 16 is a diagram showing the principle of protocol layering.

FIG. 17 is a diagram schematically showing protocol transmission and reception in RTSP.

FIG. 18 is a diagram schematically illustrating an established state of a general TCP connection and an RTSP session on TCP / IP.

FIG. 19 is a diagram schematically illustrating a TCP connection and an RTSP session established between a terminal device and a server device using a gateway device.

[Explanation of symbols]

10, 60 terminal device 11, 61, 84 memory device 12, 62, 85 CPU 13, 21, 31, 33, 63, 71, 81, 83 protocol stack 14, 24, 25, 32, 64, 74 , 75, 82 ... socket 15, 65 ... begin flag 16, 86 ... fin flag 20, 70 ... gateway device 22, 72 ... address conversion lookup table 23 ... TCP socket generator 30, 80 ... server device 40, 90 ... file System 51, 101: First network 52, 102: Second network 73: UDP socket generation unit

 ────────────────────────────────────────────────── ─── Continued on the front page (72) Inventor Masahiro Oho 1006 Kazuma Kadoma, Kadoma-shi, Osaka Matsushita Electric Industrial Co., Ltd. F-term (reference) 5K030 HA06 HA08 HD03 HD05 HD06 HD09 KA01 KA05 LA08 5K034 BB05 EE11 FF11 HH01 HH02 KK29

Claims (15)

[Claims] 1. One or more terminal devices connected to a first network, one or more server devices connected to a second network, and both devices connected to the first and second networks. A packet communication method in a server-client system comprising a gateway device that relays packet communication between the terminal device and the server device, comprising: a logic for transmitting and receiving a message in a hierarchical communication protocol between the terminal device and the server device. When the terminal device establishes a session in a temporary connection state, the terminal device assigns a first packet to be issued first to a specific portion of the first packet to indicate a session start.
A gin flag is set and transmitted to the gateway device, and the gateway device determines a session start by detecting the begin flag in the received first packet, and establishes a communication path with the server device. When the terminal device transfers the first packet to the server device and cancels the session established between the terminal device and the server device, the terminal device outputs the last packet to be issued last in the last packet. Fi indicating the end of the session in a specific part
Set the n flag and transmit to the gateway device, the gateway device determines the end of the session by detecting the fin flag in the received last packet, and sends a response to the last packet from the server device A packet communication method characterized by canceling a session after receiving. 2. One or more terminal devices connected to the first network, one or more server devices connected to the second network, and both devices connected to the first and second networks. A packet communication method in a server-client system comprising a gateway device that relays packet communication between the terminal device and the server device, comprising: a logic for transmitting and receiving a message in a hierarchical communication protocol between the terminal device and the server device. When the terminal device establishes a session in a temporary connection state, the terminal device assigns a first packet to be issued first to a specific portion of the first packet to indicate a session start.
A gin flag is set and transmitted to the gateway device, and the gateway device determines a session start by detecting the begin flag in the received first packet, and establishes a communication path with the server device. Transferring the first packet to the server device, and canceling the session established between the terminal device and the server device, based on the reception of the last packet issued last by the terminal device, the server The device sets a fin flag indicating a session end in a specific part of the response packet, and transmits the response packet to the final packet to the gateway device, and the gateway device transmits the response packet in the received response packet. Determine the end of the session by detecting the fin flag, and release the session. A packet communication method characterized in that the packet communication is erased. 3. The method according to claim 2, wherein the gateway device holds information on an established communication path, and performs packet communication after the first packet in accordance with the information.
The packet communication method according to claim 1. 4. The packet communication method according to claim 3, wherein the gateway device cancels the session by deleting information on the communication path. 5. The packet communication method according to claim 1, wherein a communication protocol of a session layer on the first network is a protocol written in a literal script. 6. The packet communication method according to claim 2, wherein the communication protocols of both session layers on the first and second networks are both protocols in a literal script notation. 7. One or more terminal devices connected to the first network, one or more server devices connected to the second network, and both devices connected to the first and second networks. A server / client system comprising a gateway device for relaying packet communication between the server device and a session which is a logical connection state for message transmission / reception in a hierarchical communication protocol with the server device. When a session is started, a begi indicating the start of a session is added to a specific portion in the first packet issued first.
When the n flag is set to cancel the session established with the server device, a fin flag indicating the end of the session is set in a specific portion of the last packet to be issued last, and the packet is transmitted to the gateway device. And a terminal device for transmitting the first packet, determining a session start by detecting the begin flag in the first packet, establishing a communication path with the server device, transferring the first packet to the server device, After determining the end of the session by detecting the fin flag in the last packet, after receiving a response to the last packet from the server device,
A gateway device for canceling the session,
Server / client system. 8. One or more terminal devices connected to the first network, one or more server devices connected to the second network, and both devices connected to the first and second networks. A server / client system comprising a gateway device for relaying packet communication between the server device and a session which is a logical connection state for message transmission / reception in a hierarchical communication protocol with the server device. When a session is started, a begi indicating the start of a session is added to a specific portion in the first packet issued first.
When the n flag is set to cancel the session established between the terminal device transmitting the packet to the gateway device and the terminal device, based on the reception of the last packet issued last by the terminal device By setting a fin flag indicating the end of the session in a specific part of the response packet to the last packet, and detecting the begin flag in the top packet and the server device transmitting the packet to the gateway device Determining a session start, establishing a communication path with the server device, transferring the head packet to the server device, and detecting the fin flag in the response packet to determine the end of the session; Server / client system comprising a gateway device for solving the problem 9. A terminal device connected via a first network to a gateway device connected to one or more server devices via a second network, wherein a hierarchical structure is provided between the terminal device and the server device. When establishing a session which is a logical connection state for transmitting and receiving a message in the communication protocol performed, a begi indicating a session start is specified in a specific portion of a first packet issued first.
A terminal device comprising: a setting unit that sets an n flag; and a transmission unit that transmits the top packet with the begin flag set to the gateway device. 10. A terminal device connected via a first network to a gateway device connected to one or more server devices via a second network, wherein a hierarchical structure is provided between the terminal device and the gateway device. When establishing a session which is a logical connection state for transmitting and receiving a message in the communication protocol performed, a begi indicating a session start is specified in a specific portion of a first packet issued first.
a setting unit for setting an n flag; and a setting unit for setting a fin flag indicating a session end in a specific portion in a last packet to be issued last when canceling a session established with the server device. the first packet with the begin flag set or the last packet with the fin flag set,
A transmission unit for transmitting to the gateway device. 11. A server device connected via a second network to a gateway device connected to one or more terminal devices via a first network, the server device being established with the terminal device. When canceling the session, based on the reception of the last packet issued last by the terminal device, a setting unit that sets a fin flag indicating the end of the session in a specific portion in a response packet to the last packet; A transmission unit for transmitting the set response packet to the gateway device. 12. A gateway device connected to one or more terminal devices via a first network and one or more server devices via a second network, wherein the gateway device is connected to the terminal device. A transmission unit that determines a session start by detecting a flag indicating a session start in a packet to be established, establishes a communication path with the server device, and transfers the packet to the server device, and a packet subsequent to the packet. In order to perform communication in accordance with the information on the established communication path, a storage unit for holding the information, and a session end by detecting a flag indicating a session end in a packet transmitted from the terminal device or the server device The session is resolved by deleting the information on the communication path after completing the corresponding packet transmission. A gateway device, comprising: a processing unit for deleting. 13. The terminal device according to claim 9, wherein a communication protocol of a session layer on the first network is a protocol in a literal script notation. 14. The communication protocol according to claim 11, wherein the communication protocol of the session layer on the second network is a protocol in a literal script notation.
A server device according to item 1. 15. The communication protocol according to claim 12, wherein both communication protocols of the session layer on the first network or on the first and second networks are both protocols written in a literal script. 3. The gateway device according to 1.