KR20070078922A - Method for transmitting data when reconnecting ppp in a mobile communication system - Google Patents

Abstract

A method for transmitting data when a PPP(Point to Point Protocol) reconnection is performed in a mobile communication system is provided to minimize a loss of data by using TCP(Transmission Control Protocol) characteristics in case data are continuously received as IP addresses are not changed when a PPP reconnection is executed. A mobile terminal establishes a PPP session with a PDSN(Packet Data Service Node)(501). If PPP establishment is completed, the mobile terminal executes data communication with a web server(503). In case a PPP establishment release situation occurs, the PDSN transmits an LCP(Link Control Protocol) terminate message(505). In this case, the physical layer of the mobile terminal transmits a notification to the TCP layer of the mobile terminal. The TCP layer inserts '0' in the window size field of a TCP header, configures a TCP packet, and transmits it to the web server through the physical layer together with the first TCP ACK message(507). Then the mobile terminal executes a PPP renegotiation with the PDSN(509). If the PPP renegotiation is completed, the mobile terminal transmits an MIP(Mobile IP) registration message to the PDSN(511). The PDSN transmits an MIP response message to the mobile terminal in order to allocate a mobile IP address(513). If a PPP reconnection between the mobile terminal and the PDSN is completed, the physical layer of the mobile terminal transmits a notification to the TCP layer. The TCP layer inserts the actual window size of the mobile terminal in the window size field, configures a TCP packet, and transmits it to the web server through the physical layer together with the second TCP ACK message(515). Receiving the second TCP ACK message and confirming the TCP packet, the web server executes data transmission to the mobile terminal again(517).

Description

METHOD FOR TRANSMITTING DATA WHEN RECONNECTING PPP IN A MOBILE COMMUNICATION SYSTEM}

1 is a block diagram of a general mobile communication system;

2 is a flowchart illustrating an IP allocation process of a mobile terminal in a mobile communication network according to the prior art;

3 is a diagram illustrating a TCP header applied to the present invention;

4 is a diagram illustrating a protocol stack of a mobile terminal to which the present invention is applied;

5 is a diagram illustrating a data transmission method when PPP reconnects in a mobile communication system according to an embodiment of the present invention.

The present invention relates to a mobile communication system, and more particularly, to a data transmission method when PPI is reconnected in a mobile communication system.

Mobile networks have been developed for voice communications. Such a mobile communication network has been developed into a system capable of transmitting high-speed data capable of a multimedia service such as an email, a still image, a video, as well as a general voice service due to the rapid development of technology. In general, the so-called third generation mobile communication network that supports both voice and packet services, as is well known as synchronous CDMA 2000 1x, 1x Evolution Data Only (EV-DO) capable of high-speed packet transmission, EV-DV (Evolution) of Data and Voice) and asynchronous UMTS (Universal Mobile Telecommunication Systems).

Referring to the mobile communication network as shown in FIG. 1, a mobile terminal 10 capable of accessing a mobile communication network and a base station system (BSS) 20 through which the mobile terminal 10 is connected through a wireless channel are shown. Is connected to. The base station 20 is connected to a packet control unit (not shown) that controls the transmission and reception of packet data between the mobile terminal 10 and the base station 20 to perform packet data communication. In addition, the packet controller is connected to a packet service node (PDSN) 30 that transmits / receives packet data. The packet data service node 30 provides an IP routing function to the mobile terminal 10 accessing the IP network 60 through a mobile communication network. In addition, the packet data service node 30 performs a Point to Point Protocol (PPP) connection to the mobile terminal accessing the IP network 60 through the mobile communication network. In addition, the packet data service node 30 may serve as a foreign agent (FA) when supporting mobile IP.

The web server 50 is connected to the IP network 60 and performs data communication with the mobile terminal 10. The web server 50 may also be referred to as a correspondent node (CN) that is an external server or host.

2 is a flowchart illustrating an IP allocation process of a mobile terminal in a mobile communication network according to the prior art.

Referring to FIG. 2, in step 201, the mobile terminal 10 first performs a traffic channel (TCH) setup with the base station 20, and the base station 20 performs an RP session with the packet data service node 30 ( Remote Node-PDSN Session) setup. The packet data service node 30 performs a Point to Point Protocol (PPP) connection and charging / authentication processing for a subscriber accessing an IP network through a mobile communication network, and provides a handoff service. In addition, the PDSN 30 may serve as a foreign agent (FA) when supporting a mobile IP.

The mobile terminal 10 and the packet data service node 30 perform a link control protocol (LCP) negotiation in step 203, and perform a CHAP (Challenge Handshake Authentication Protocol) authentication in step 205. Thereafter, in step 207, an IP Control Protocol (IPCP) negotiation is performed to allocate an IP address used by the mobile terminal 10.

As described above, most of the mobile terminals 10 are assigned IP as a simple IP and perform data communication with the web server 50. If the PPP session is terminated due to a situation such as a handoff or a system abnormality, the mobile terminal 10 cannot continue to receive data that has been previously received because the mobile terminal 10 needs to be allocated an IP again. When the mobile terminal 10 connects to the packet data service node 30 again and establishes a new PPP session, the mobile terminal 10 cannot maintain the session of the upper layer (TCP / UDP layer / application layer) because the old IP cannot be allocated. Results in. Therefore, when the above-mentioned thing occurs during data communication, there is a problem that data must be received from the beginning. In addition, the packet data service node 30 may not deliver the packet transmitted from the web server 50 to the mobile terminal 10 until the PPP reconnection is completed.

Next, when a mobile terminal uses mobile IP, a data transmission method upon PPP resetting will be described.

In case of using mobile IP, the mobile terminal 10 uses a home address managed through a home agent (HA) 40 to generate a handoff and then reconnects the PPP session even if the PPP session is terminated. You can keep the same IP address. The HA 40 intercepts the packet transmitted to the mobile terminal 10 through the existing IP packet forwarding path, and then delivers the packet to the mobile terminal 10 which is handed off through the new IP tunneling path. Can be provided. However, the mobile terminal 10 must reconnect to the disconnected PPP session, at which point data transmission is not possible. Data is sent only after a new PPP session is connected. However, the web server 50 sending the packet data does not know whether the PPP session between the mobile terminal 10 and the packet data service node 30 is disconnected and continues to transmit data to the mobile terminal 10. Will be sent to. In this case, when the mobile terminal 10 performs a PPP reconnection and establishes a new connection for a long time, the mobile terminal 10 cannot send an acknowledgment (ACK) message for the data received from the web server 50. Therefore, the web server 50 sends a retransmission frame, which wastes a lot of wired / wireless resources.

Accordingly, an object of the present invention is to provide a data transmission method when PPP reconnects in a mobile communication system that minimizes data loss by using the characteristics of Transmission Control Protocol (TCP) when PPP reconnects in a mobile communication system.

Another object of the present invention is to continuously receive data when the IP does not change during PPP reconnection, and at this time, to provide a data transmission method for PPP reconnection in a mobile communication system that minimizes data loss by using the characteristics of TCP have.

Another object of the present invention is to provide a data transmission method when PPP reconnects in a mobile communication system which minimizes bandwidth waste.

The method according to an embodiment of the present invention is a data transmission method in a mobile terminal when PPI is reconnected in a mobile communication system, and when the PPP is released, the LCP terminal is transmitted from a packet data service node. Upon receiving a terminate message, constructing a TCP packet having a window size of '0', delivering the configured TCP packet to the web server through the packet data service node, and in case of PPP renegotiation, the packet data service. The method may include configuring a TCP packet allocated with a mobile IP from a node, putting a window size into a window size, and delivering the configured TCP packet to a web server through the packet data service node.

The method according to an embodiment of the present invention is a data transmission method in a packet data service node when PPI is reconnected in a mobile communication system, and when the PPP is released, the LCP terminal is transmitted to the mobile terminal. Transmitting a terminate message, receiving a TCP packet having a window size of '0' from the mobile terminal, and transmitting the same to a web server; and assigning a mobile IP to the mobile terminal when renegotiating PPP, And receiving a TCP packet including the actual window size of the mobile terminal in the window size from the terminal and transmitting the received TCP packet to the web server.

In the following description of the present invention, detailed descriptions of well-known functions or configurations will be omitted if it is determined that the detailed description of the present invention may unnecessarily obscure the subject matter of the present invention. Terms to be described later are terms defined in consideration of functions in the present invention, and may be changed according to intentions or customs of users or operators. Therefore, the definition should be made based on the contents throughout the specification.

In the PPP reconnection in the mobile communication system according to an embodiment of the present invention, it is possible to minimize data loss and minimize waste of wired / wireless resources by using the characteristics of Transmission Control Protocol (TCP).

To this end, according to the present invention, when the mobile station sends a notification to the TCP layer of the mobile station before performing the PPP reconnection, the TCP stack of the mobile station fills a value 0 in the window size field of the TCP header. If the packet is sent to the web server, the web server does not send data until the mobile terminal increases the window size, thereby minimizing resource loss as well as data loss.

To do this, you first need to understand TCP.

The Transmission Control Protocol (TCP) is a connection-oriented protocol, and a connection must be established between two endpoints before sending data to each other. The TCP is a protocol that controls the connection when connecting to the Internet, and is used when FTP sharing with a unique address owned by each computer as an IP. Transmission control protocol / Internet Protocol (TCP / IP) is the basic communication protocol of the Internet, and is also used in private networks such as intranets and extranets. When a user configures his or her computer to access the Internet, a TCP / IP program is installed, which allows users to exchange messages or get information with other computer users who also use the same TCP / IP protocol.

TCP / IP is a two-layer program. The upper layer, TCP, is responsible for breaking messages or files into smaller packets for transmission over the Internet, and for reassembling the received packets into original messages. The lower layer, or IP, processes the address portion of each packet, allowing packets to reach their destination exactly. Each gateway on the network checks the address of the message to know where to send the message. If a message is divided into packets, each packet can be delivered through a different path, and they are reassembled at the final destination.

The transport layer protocol provides several functions, such as: One is to establish interprocess communication. TCP uses port numbers for interprocess communication. Another function of the transport layer protocol is to provide flow and error control mechanisms in the transport phase. TCP uses a sliding window protocol for flow control. TCP also uses response packets, time-outs, and retransmissions for error control. The transport layer also provides a connection mechanism for the application. The application program must be able to transmit the data stream to the transport layer. The transport layer of the transmitting station performs a function of establishing a connection with the receiving side, cutting the data stream into units that can be transmitted, numbering each unit, and transmitting one by one. The transmitting layer of the transmitting station performs a function of establishing a connection with the receiving side, cutting the data stream into units that can be transmitted, assigning a number to each unit, and transmitting one by one. The transport layer on the receiving side waits until each unit belonging to one application program arrives, checks whether there is an error, makes no error, and passes them as a data stream to the receiving application. After all data streams have been transmitted, the transport layer terminates the connection. TCP performs all these tasks. TCP is called a connection-oriented reliable transport protocol. TCP adds connection-oriented and reliability features to IP services.

It is assumed that the present invention is applied to the case of data communication performed through a TCP connection.

In the mobile communication system according to an embodiment of the present invention will be described with reference to the drawings of FIG.

The present invention transmits a TCP ACK message when the mobile terminal 10 receives an LCP Terminate request from the base station 20 before the mobile terminal performs the PPP reconnection. At this time, the TCP ACK message includes a TCP header as shown in FIG.

As shown in FIG. 3, the TCP header includes a 16-bit source port address, a 16-bit destination port address, a 32-bit sequence number, and a 32-bit confirmation. Acknowledgment number, 4-bit TCP header length, 6-bit reserved information, Urgent Pointer field significant (URG), Acknowledgment field significant (ACK), Push Function (PSH), Reset the connection ), FIN (No more data from sender), SYN (Synchronize sequence numbers), 16 bit window size, 16 bit checksum, 16 bit Urgent pointer, Options & Padding (Option & padding), etc.

In the present invention, the window size field is used.

The window size represents a buffer size of the mobile terminal. In the present invention, if the TCP packet is configured by filling the window size field with a specific value 0, and the configured TCP packet is transmitted to the web server 50, the web server 50 determines that the mobile terminal 10 determines the window size. The data is in a standby state without being transmitted to the mobile terminal 10 until it is increased and transmitted. In this case, putting '0' in the window size field of the TCP header includes the meaning that the web server 50 waits without transmitting data since the reception buffer of the mobile terminal is '0'.

Next, a protocol stack of a mobile terminal for transmitting a TCP packet including a TCP header as described above to a web server will be described with reference to FIG. 4.

4 is a diagram illustrating a protocol stack of a mobile terminal to which the present invention is applied.

Referring to FIG. 4, the mobile terminal includes a UDP layer / TCP layer 401/403, an IP layer 405, a PPP layer 407, a MAC layer 409, and a physical (PHY) layer in descending order. 411).

When the physical layer 411 of the mobile terminal receives an LCP Terminate message indicating that the PPP connection is to be terminated from the packet data service node 30, the physical layer 411 transmits a notification to the TCP layer 403 of the mobile terminal. do. Then, when configuring the TCP packet, the TCP layer 403 of the mobile terminal configures the TCP packet by putting '0' in the window size of the TCP header, and transmits the configured TCP packet to the physical layer 411. Then, the TCP packet is transmitted to the web server 50 through the physical layer 411 of the mobile terminal.

5 is a flowchart illustrating a data transmission method when PPP reconnects in a mobile communication system according to an exemplary embodiment of the present invention. Referring to FIG. 5, a method of transmitting data when PPP reconnects in a mobile communication system according to an embodiment of the present invention will be described.

Referring to FIG. 5, in step 501, the mobile terminal 10 establishes a PPP session with the packet data service node 50. When the PPP configuration is completed, the mobile terminal 10 performs data communication with the web server 50 in step 503. If a situation to release the PPP setting occurs, the packet data service node 30 transmits an LCP Terminate message to the mobile terminal 10 in step 505 to inform the mobile terminal 10 of this. Then, the mobile terminal 10 receiving the LCP Terminate message performs the following operation in step 507.

First, when the physical layer 411 of the mobile terminal 10 transmits a notification to the TCP layer 403 of the mobile terminal 10, the TCP layer 403 configures a TCP packet, as shown in FIG. A TCP packet is constructed by putting '0' in the window size field of the TCP header. The configured TCP packet is included in the first TCP ACK message and transmitted to the web server 50 through the physical layer 411.

Since the window size of the TCP header of the mobile terminal 10 is '0', the size of the reception buffer of the mobile terminal 10 is '0'. After confirming that it is, wait without transmitting data.

Meanwhile, in step 509, the mobile terminal 10 performs PPP re-negotiation with the packet data service node 30. After the renegotiation, the mobile terminal 10 transmits a mobile IP (MIP) registration message to the packet data service node 30 in step 511. Then, in step 513, the packet data service node 30 transmits a MIP response message to allocate the mobile IP to the mobile terminal 10.

When the PPP reconnection between the mobile terminal 10 and the packet data service node 30 is completed, the physical layer 411 of the mobile terminal transmits a notification to the TCP layer 403. When configuring the TCP packet as shown in FIG. 3, the TCP layer 403 of the mobile terminal 10 configures the TCP packet by inserting the actual window size of the mobile terminal into the window size field, that is, the size of the actual buffer of the mobile terminal. The TCP packet configured by the above method is included in the second TCP ACK message in step 515 and transmitted to the web server 50 through the physical layer 411.

When the web server 50 receives the second TCP ACK message, the web server 50 checks a TCP packet including a window size other than '0' from the mobile terminal 10 and transmits data to the mobile terminal 10 again. Perform. That is, in step 517, data communication is performed between the mobile terminal 10 and the web server 50.

It takes at least 2 to 3 seconds for the mobile terminal 10 to perform PPP reconnection in the traffic channel of 153.6kbps in the code division multiple access method, and also takes at least 2 to 3 seconds when performing the Mobile IP registration. do. Eventually, nothing can be received for 4 to 6 seconds, but the amount of lost packets increases in proportion to the window size that the mobile terminal 10 originally had. The web server 50 sends data to the mobile terminal 10 to wait for an ACK, and then sends a retransmission frame when the retransmission timer expires. Assuming that the retransmission timer of the web server 50 was the first 1 second (average value in the wireless network), no response can be received even when sending data and sending a second packet. In general, if the TCP retransmission timer was initially 1 second, then the next timer is 3 seconds, so retransmit and wait 3 seconds. You can still receive it, so you can send it one more time and eventually receive a response. When PPP re-negotiation is performed as soon as possible, at least three TCP packets (1500 * (windowsize / MSS)) retransmissions occur. After all, one packet must send the same thing at least four times before the mobile terminal 10 can receive it. If the PPP session reconnection is slower, there will be much more retransmission packets. Since the data of this period is caused by the mobile terminal 10 not being able to receive such packet loss, it should not be sent at all, thereby preventing the waste of wired / wireless bandwidth. In order to prevent such a loss, the present invention prevents the mobile terminal from sending data from the web server using the TCP characteristic without complicated functions even when the mobile terminal performs PPP reconnection, thereby minimizing the loss of bandwidth of the wired / wireless network and controlling the data flow. Data flow control) can minimize data loss.

In the present invention operating as described in detail above, the effects obtained by the representative ones of the disclosed inventions will be briefly described as follows.

The present invention can minimize data loss by using the characteristics of Transmission Control Protocol (TCP) when reconnecting PPP in a mobile communication system.

The present invention can continuously receive data when the IP is not changed during PPP reconnection. In this case, data loss can be minimized by using the characteristics of TCP.

The present invention can minimize bandwidth waste.

Claims (6)

In the point-to-point protocol (PPP) reconnection in the mobile communication system, in the data transmission method in the mobile terminal, When the PPP is deconfigured, upon receiving the LCP terminate message from the packet data service node, a TCP packet including '0' in the window size is composed, and the configured TCP packet is transmitted to the web server through the packet data service node. Process, In case of PPP renegotiation, mobile IP is allocated from the packet data service node, constructs a TCP packet having a window size in a window size, and delivers the configured TCP packet to a web server through the packet data service node. A data transmission method when PPI is reconnected in a mobile communication system. The method of claim 1, The window size is a buffer size of the mobile terminal, characterized in that the data transmission method when the PPI is reconnected in the mobile communication system. The method of claim 1, When the web server receives a TCP packet including '0' in the window size from the mobile terminal, The method of claim 1, further comprising the step of stopping data transmission to the mobile terminal. In the method of data transmission in the packet data service node when P-PIP (PPP) reconnection in a mobile communication system, When the PPP is released, transmitting an LCP terminate message to the mobile terminal, receiving a TCP packet having a window size of '0' from the mobile terminal, and transmitting the received TCP packet to a web server; A mobile communication system comprising: allocating a mobile IP to the mobile terminal upon PPP renegotiation, receiving a TCP packet including the actual window size of the mobile terminal in the window size from the mobile terminal, and transferring the received packet to a web server; To send data when PPI is reconnected. The method of claim 4, wherein The window size is a buffer size of the mobile terminal, characterized in that the data transmission method when the PPI is reconnected in the mobile communication system. The method of claim 4, wherein When the web server receives a TCP packet including '0' in the window size from the mobile terminal, The method of claim 1, further comprising the step of stopping data transmission to the mobile terminal.

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