JP4220530B2 - Gateway device and wireless terminal device - Google Patents

Description

The present invention relates to a gateway device and a wireless terminal device which are communication devices that realize a communication protocol including a transport layer.

In recent years, there has been an increasing demand for realizing wireless data communication. TCP (Transmi
session control Protocol) is widely used as a reliable transport layer protocol in wired data communication. However, if this protocol is applied to radio as it is, the following problems occur.

TCP segment loss in wired communication means network congestion, so TCP
Is designed to avoid congestion by reducing the data transmission rate when segment loss is detected. For this reason, TCP segment loss due to radio section errors and handoff is also interpreted as congestion, and throughput is reduced as a result of performing congestion avoidance more than necessary. Specifically, when a terminal is communicating, packet transmission / reception may not be performed due to, for example, deterioration of the quality of a wireless transmission path in the network. At this time, TCP tries to retransmit several times using the timeout of the retransmission timer and sets the congestion window to 1 × MSS (maximum segment size). This means that even if the packet can be transmitted and received again, it takes time to reach the same transmission rate as the original.

In addition, since many data communication services using a network are heavily used for downloading data from a server terminal to a client terminal, the bandwidth of input to the client terminal has recently been reduced in output from the client terminal. Extremely wide compared to bandwidth
Asymmetric transmission rate access networks have been developed. When such an asymmetric configuration is applied to wireless communication, there is an advantage that the client terminal can be reduced in size because the mounting of the broadband wireless transmitter of the client terminal can be omitted. However, in a network having such an asymmetric transmission path, there is an algorithm that “returns one ack (delivery confirmation) for at least two TCP segments” in the recommended TCP implementation method. TCP throughput from client to client may decrease. This is because the throughput from the server to the client is (client to server bandwidth) x (
This is because (2 × maximum segment size) / ack size cannot be exceeded.

In order to solve such a problem, a method of relaying at the boundary between a wired network and a wireless network using a normal TCP for a wired network and a wireless transport layer protocol for a wireless network has been proposed.
This method uses selective ack for high TCP segment loss rates,
For the congestion problem, the data loss in the radio unit is retransmitted without being regarded as congestion, and for the asymmetry problem, the TCP maximum segment size in the radio unit is increased.

However, the method of once terminating and transporting the transport layer connection at the gateway is as follows:
It breaks the end-to-end semantics of TCP that guarantees that the data targeted for ack has arrived at the receiving terminal when the transmitting terminal receives the ack that is the delivery confirmation. This is because when a gateway that performs TCP relay at the boundary between the wired part and the wireless part receives data, it returns an ack for the data to the transmitting side.

Some application layer protocols that utilize TCP require the preservation of this end-to-end semantics and others do not. HTTP (HyperText
Transfer Protocol) allows the client to TC prior to each request.
After setting up the P connection and sending a response to the HTTP request from the client,
The server disconnects the TCP connection. In this case, since the request is completed by the response of the application layer, there is no particular problem even if the end-to-end semantics of TCP are changed. However, for protocols such as TELNET (Remote Terminal Protocol), it is desirable to preserve the end-to-end semantics of TCP.

Also, if it is necessary to relay the TCP connection at a different gateway due to the handoff of the wireless terminal, the gateway that previously relayed the TCP connection of the wireless terminal to the new gateway is wired. Information on the state of the transport layer of the wireless unit and the wireless unit, and the TC of the wireless terminal in the new gateway
A state in which the P connection can be relayed must be established. Since it takes time to transfer and establish this state, there is a problem that throughput is reduced when a wireless terminal performs handoff between base stations accommodated in different gateways.

Furthermore, a wireless service area in which a gateway can provide a TCP connection relay service is preferable because a larger one can reduce the number of handoffs between gateways that perform TCP connection relay, while a wide wireless service area can be provided by a single gateway. When the service is performed, the number of wireless terminals served by the gateway increases, so that the load is concentrated, and there is a problem that it becomes a bottleneck in performance.

In addition, when an asymmetric communication path is used to multiplex and transmit not only the TCP ack but also other data to the narrowband transmission path on the narrowband transmission path, RTT (R
(Own Trip Time) and dispersion increase. in this case,
Since the bandwidth delay product increases, the throughput decreases unless the reception window size is increased accordingly. However, there are cases where the reception window size cannot be made sufficiently large corresponding to the bandwidth delay product on the wideband side. Also, the TCP transmission side uses the observed RTT to determine the RTO (
Retransmission Time Out) is determined, but as a result of an increase in RTO, the throughput decreases due to an increase in retransmission waiting time when a TCP segment is lost.

Further, a case is considered in which the gateway operation stops after the gateway transmits an ack for certain data to the transmitting side terminal and before the data is successfully transmitted to the receiving side terminal. In this case, the transmitting terminal that has received ack discards the data from the retransmission buffer at that time, and therefore cannot retransmit the data. In other words, the TCP connection is a transport layer protocol that achieves highly reliable communication, but it causes a negative effect that the reliability of the TCP is lowered due to the gateway.

Further, in the TCP layer and the IP layer, functions that are treated as options but added as a standard can be used. For example, in the TCP layer, MTU (MTU which is the maximum packet size that can be transferred without fragmentation on the path between communicating terminals in the TCP layer.
There is a method of searching for (Aximum Transfer Unit). If this procedure is performed, data can be transferred with the maximum packet length that can be transmitted on the path for setting the TCP connection, and no fragmentation occurs in a router or the like along the path, so that wasted processing time. No longer spend money.

For this reason, there is an advantage that throughput can be improved in the TCP connection. This procedure is referred to as “PATH MTU Discovery”.

Information for controlling such options follows the TCP and IP headers as shown in FIG. The terminal A that wants to use the option is directed to the terminal B of the communication partner,
When a TCP connection establishment request is made, a TCP segment having this optional header is transmitted. The terminal that has received the TCP segment having the header with the option performs a predetermined option process, and determines whether to permit or deny the option. The terminal B transmits a TCP segment including the permission / denial information to the terminal A. If this is permission, the optional function is executed, and if not, it is not executed.

In this way, it is necessary to finally decide whether or not to allow the option between the terminals that set up the connection, but when relaying the connection at the gateway, TCP
Since the gateway receives the connection establishment request and divides and sets the connection, there is a problem that the above-described exchange cannot be performed between terminals that set the connection.

In TCP, a series of flow of connection establishment → data transmission / reception → connection disconnection is managed using the TCP state transition diagram of FIG. In FIG. 30, ES
In the TABLESED state, actual user data is transmitted and received. CLOSE
The D state is from connection release to connection establishment, and is a period in which no connection exists. SYN_SENT, SYN_RCVD, and LISTEN are connection establishment phases, and the others are connection release phases. In TCP, there are many states like this. For example, when relaying a TCP connection or performing an operation to move the gateway function to be performed to another gateway, depending on the state of the original gateway, There is a problem that it may fall into an unstable state when transferring functions.

The present invention has been made in order to solve the above-described problems that occur when a reliable transport layer protocol is applied to a wireless network. The object of the present invention is to provide a wired network. Without changing the implementation of the transport layer of the connected terminal, set the transport layer connection between the wired terminal and the wireless terminal in a form suitable for the application, or according to the wireless communication status between the wireless terminal and the base station It is an object of the present invention to provide a highly reliable gateway device and wireless terminal device that can improve the performance of communication using the transport layer connection via a wireless network by making the transport layer connection controllable.

  A gateway device according to an embodiment of the present invention provides a transport layer protocol that performs congestion avoidance processing by interpreting a loss of a transport layer protocol data unit as congestion in a gateway device that connects and connects a wireless network and a wired network The transport layer connection between the transport protocol processing means to be processed and the connection terminal of the wireless network is divided into a first connection and a second connection of a transport layer protocol for communication with the wireless network. Or setting a transport layer connection between the connection terminal of the wireless network and the connection terminal of the wired network, between the first connection of the transport layer protocol for communication with the wireless network and the wired network Set to be divided into the second connection of the transport layer protocol for communication A handoff start signal indicating that the wireless terminal starts a handoff operation from the wireless service area handled by the first base station to another wireless service area handled by the second base station. When received, the terminal communicating with the wireless terminal performing the handoff transmits a transport layer protocol data unit including a signal for performing flow control so as to suppress packet transmission. The congestion avoiding process due to the loss of the transport layer protocol data unit is suppressed.

  The wireless terminal device according to an embodiment of the present invention congests a loss of a transport layer protocol data unit in a wireless terminal device that communicates with a wireless network connection terminal or a wired network connection terminal via a base station. Between the base station, the transport layer protocol processing means for processing the transport layer protocol for interpreting the congestion avoiding processing, the transmission suppressing means for transmitting a signal for suppressing packet transmission to the transport layer protocol processing means, and the base station A handoff notification means for notifying the transmission control means when the start and end of the handoff operation are detected, and a signal for suppressing the packet transmission when the start of the handoff operation is notified to the transmission control means. Starts transmission of transport layer protocol data units including the packet transmission The signal is a signal for performing flow control so as to suppress packet transmission for a signal that receives the signal for suppressing the packet transmission, and when the transmission control means is notified of the end of the handoff operation. The transmission of the transport layer protocol data unit including the signal for suppressing the transmission of the packet is terminated.

As described above in detail, according to the present invention, the transport layer connection between the wired terminal and the wireless terminal can be set in a form suitable for the application without changing the implementation of the transport layer of the terminal connected to the wired network. In addition, a highly reliable communication network that improves the performance of communication using the transport layer connection can be realized.

  Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings.

FIG. 1 shows a configuration of a gateway device 900 according to an embodiment of the present invention. In the figure, solid arrows between blocks indicate a data flow, and broken arrows indicate a control flow.

As shown in the figure, the gateway device 900 includes an application 800, a plurality of relay servers 810 and 820 each having caches 811 and 821, and a wireless TCP layer 6
00, TC having wireless to wired relay unit 611 and wired to wireless relay unit 612
The P relay unit 610, the TCP layer 620, the IP layer 400, the wired IF unit 100, and a plurality of wireless IF units 200, 210, and 220 are configured.

The wireless TCP layer 600 includes a wireless TCP input unit 601 having a segment filter 603 and a wireless TCP output unit 602. The TCP layer 620 includes a TCP input unit 621 having a segment filter 623 and a TCP output unit 622. The IP layer 400 includes an IP input unit 401 including a datagram filter 405, an IP relay unit 403, an IP output unit 402, and a movement control unit 404. The wired IF unit 100 includes a wired IF input unit 101 and a wired IF output unit 102.
And have. The wireless IF unit 200 includes a wireless IF input unit 201 and a wireless IF output unit 202. The wireless IF unit 210 has a wireless IF output unit 212. The wireless IF unit 220 includes a wireless IF input unit 221 and a wireless IF output unit 222.

Here, the transport layer protocol changed for wireless use is referred to as “wireless TCP”. For example, selective to deal with high error rates during wireless communication
It is possible to consider a TCP that has been modified so that the congestion window control is always set to slow start in order not to regard TCP segment loss as congestion. In addition, when the upstream and downstream bands are asymmetric, the maximum segment size is set to be large so as to reduce the number of occurrences of ack in the radio section, and the threshold for the fast retransmission algorithm is decreased to reduce retransmission due to timeout. The TCP may be modified so as to be changed.

In the present invention, control is performed using information across protocol layers, so that the block boundaries of each protocol layer are not strict. That is, a configuration in which functions belonging to the protocol layer according to the present embodiment are implemented in another protocol layer is also conceivable.

FIG. 2 shows a configuration example of a first communication network that includes the gateway device 900 of FIG. 1 and is the first embodiment of the present invention. As shown in the figure, this communication network is a wired network 1
Connected to the wired network 1101, the wired terminals 1001, 1002, 1003 connected to the terminal 101, the gateway device 901 connected to the wired network 1101 and indirectly connected to the base stations 1401, 1402, 1403 via the router 1301. And base stations 1404, 1405
1406, a gateway device 903 connected directly to the wired network 1101 and directly connected to the base stations 1407 and 1408, and base stations 1401-1.
408 includes wireless terminals 1601 to 1605 that perform communication while moving between wireless service areas 1501 to 1508, respectively.

The router 1301 may be a normal router that performs routing by looking at the header information of the IP datagram, or is an exchange that exchanges a virtual circuit that passes the IP datagram. May not be referred to (referred to when determining a route of a line only when a virtual line is set).

The configuration of the gateway device 900 illustrated in FIG. 1 is a general configuration, and does not indicate the specific configuration of the gateway devices 901, 902, and 903 in the network illustrated in FIG. However, for the sake of explanation, it is assumed that the wired IF unit 100 is connected to the wired network 1101 and the wireless IF unit 200 is connected to the base stations 1401 to 1406. Further, in the network of this example, the unidirectional wireless IF unit 210 is connected to the base station 1408, and operates as a pair with the wireless IF unit 220 connected to the base station 1407. Assume that communication at an asymmetric transmission rate is realized, in which transmission to 1605 is high speed and transmission / reception between the wireless terminal 1605 and the base station 1407 is relatively low speed.

  FIG. 3 shows the configuration of a wireless terminal 1600 according to an embodiment of the present invention.

As shown in the figure, the wireless terminal 1600 includes a wireless application 850, an application 860, a wireless TCP layer 700 including a wireless TCP input unit 701 and a wireless TCP output unit 702, a TCP input unit 711, and a TCP output unit. TCP layer 7 including 712
10, a TCP selection unit 720, an IP layer 500 including an IP input unit 501 and an IP output unit 502, and a wireless IF unit 300.

The wired IF unit 100 and the wireless IF units 200, 210, and 220 of the gateway device 900 are
This function realizes a so-called data link layer function, but performs an operation based on information of a part of the TCP layer and the IP layer. The following points should be particularly mentioned in this operation.

The wireless IF input units 201 and 221 are IP datagram reconstructing units 2 that combine IP datagrams received in a form divided into a plurality of data link frames into original IP datagrams.
03, 223.

FIG. 4 shows how an IP datagram is divided into a plurality of data link frames. The IP datagram reconstructing units 203 and 223 also operate when a plurality of data link frames constituting another IP datagram are interposed between a plurality of data link frames constituting a certain IP datagram (see FIG. 5). And processing to reassemble the original IP datagram (reconstruction). In this IP datagram reconfiguration, for example, a plurality of data link frames constituting an IP datagram are transmitted without changing the order, and the identifier of the IP datagram is described in the header of each data link frame. It is done under the conditions to say.

The IP datagram reconstructing units 203 and 223 confirm the size of the IP datagram based on the IP header included in the first data link frame, and all the data link frames constituting the IP datagram based on the size and the identifier. Are recombined to reconstruct the IP datagram. Also, the IP datagram reconstruction unit 203, 223
If a predetermined condition such as a timeout is satisfied before all the data link frames constituting the same IP datagram are received, these data link frames are discarded.

In the examples of FIGS. 4 and 5, TCP pure ack (ack of data only header)
Is assumed to be interposed between a plurality of data link frames constituting an IP datagram. In particular, if the first information is transmitted by TCP on the high-speed wireless link, the ack is returned on the low-speed wireless link, and the second information is transmitted on the low-speed wireless link, the second information is By shortening the data link frame to be sent and allowing ack between them, it can be expected to improve the TCP performance by reducing the size of TCP RTT and its dispersion. Further, the data link frame here has a significant difference from the IP fragment in that it has no IP header except for the first one. Since it is sufficient to guarantee short-term uniqueness, the identifier can be made sufficiently smaller than the IP header, so this method has less overhead than using IP fragments. Of course, T
The overhead of this method is less than the method of reducing the size and dispersion of TCP RTT by reducing the CP segment size.

The IP datagram reconstruction units 203 and 223 have a function of returning the compressed TCP / IP header to the normal TCP / IP header and then passing the IP datagram to the IP input unit. Compression methods include SLIP (Serial Line IP) and PP.
A method used in P (Point-to-Point Protocol) and its modifications can be applied. In particular, in wireless communication with an asymmetric transmission speed, it is effective to use these compressions in a transmission path with a narrow band (low transmission speed). There is.

The IP layer 400 of the gateway device 900 differs from a normal IP layer in the following points.

In the normal IP layer, the IP input unit 401 raises the IP datagram addressed to its own system to the upper layer (TCP layer), and passes the others to the IP relay unit 403. However, the IP according to the present invention
The datagram filter 405 of the input unit 401 is an IP datagram having a destination other than the IP address assigned to its own system as long as the following conditions (1) and (2) are satisfied. 200 and 220 are input to the wireless TCP input unit 601
When it is input from the wired IF unit 100, it is passed to the TCP input unit 621. When passing, a tag for identifying any of connection setting, relay in the TCP layer, and relay in the application layer is added to the IP datagram.

(1) IP datagram relating to setting of a new TCP connection (hereinafter referred to as “connection setting IP datagram”). Specifically, the SYN segment from the request side (ordinary client) necessary for setting the TCP connection, and the server side ac corresponding to it
An IP datagram containing one of three segments: a SYN segment containing k and a client side ack for it. A configuration in which the IP datagram input from the wireless IF unit 200 is not targeted is also conceivable. This is meaningful when the wireless terminal explicitly requests TCP relay by specifying the IP address of the gateway device.

(2) An IP datagram that flows through an existing TCP connection (the protocol field indicates TCP), and that is determined to be relayed at the TCP layer or higher when setting the TCP connection (hereinafter referred to as “upper layer relay IP datagram”) Call). Specifically, a combination of a source IP address, a source port number, a destination IP address, and a destination port number that identifies a TCP connection is registered in a relay method table described later as a TCP layer relay or an application layer relay. An IP datagram in which a combination of a source IP address, a destination IP address, and a flow ID is registered in a relay method table described later as a TCP layer relay or an application layer relay.

Note that IP datagrams relayed from wired to wired or wireless to wireless by referring to the destination IP address, transmission source IP address, or flow ID are not configured to be raised to higher layers such as the TCP layer. May be. For example, in the case of transmission between wireless terminals, only the wireless section is transmitted. Therefore, only the wireless TCP layer provided in each wireless terminal is changed according to the characteristics of the wireless transmission path, thereby improving the performance. It becomes effective in the case.

The movement control unit 404 included in the IP layer 400 changes the routing information of the IP relay unit 403 to reflect the movement of the wireless terminals 1601 to 1605, and the input IP datagram is sent to the destination wireless terminals 1601 to 1605. Control is performed so that it is output to the corresponding correct IF.

In addition, the movement control unit 404 physically moves the wireless terminals 1601 to 1605 to the wireless service area of the base station accommodated in another gateway apparatus among the wireless service areas of the base stations accommodated in the gateway apparatus. Appropriate events after the movement (for example, the received power is below the threshold), such as when moving from a non-adjacent to an adjacent one, or when a wireless terminal is powered on in an adjacent wireless service area TC, etc.)
The higher layer above the P layer is notified that the terminal may move to the service area of another gateway device. Ordinary handoff is performed below the network layer, but since the present invention has a state beyond the transport layer, it may be effective to provide a handoff above the transport layer. This notification is used to know the trigger for starting the handoff preparation above the transport layer.

The TCP layer (600, 610, 620 generically) of the gateway device 900 is a normal TC.
It differs from the P layer in the following points.

In the normal TCP layer, only the TCP segment addressed to its own system is input, and the data contained therein is transferred to an appropriate application according to the port number. However, the TC according to the present invention
In addition to these, the P layer processes the TCP segment and the upper layer relay IP datagram included in the connection setting IP datagram.

The wireless TCP layer 600 realizes the transport layer protocol improved for wireless as described above. When the wireless TCP input unit 601 or the TCP input unit 621 receives the connection setting IP datagram, the segment filter 603 or 623 performs the IP relay unit 403 based on the contents of the header of the TCP segment and possibly the contents of the payload. It is determined whether to perform relay, to relay by the TCP relay unit 610, or to relay by the application relay servers 810 and 820. In many cases, an upper-layer application can be identified by the source and destination port numbers included in the TCP header. In the case where the application cannot be identified, a method of estimating the application from information in the TCP payload is also conceivable. Whether the relay is performed at the IP layer, the TCP layer, or the application layer is determined by the type of application carried by the TCP connection to be set. The following are examples of guidelines for this determination.

The significance of relaying in the TCP layer is that the TCP layer 620 and the wireless TCP layer 600 of the gateway device 900 are changed to protocols suitable for the wired network 1101 or the transmission path of the wireless network, so that the TCP layer of the wired terminal The TCP throughput between terminals can be improved without changing the wireless TCP layer of the wireless terminals. Furthermore, the TCP connection between wireless terminals is divided into two connections used in the wireless network, or the TCP connection between the wireless terminal and wired terminal is divided into a connection used in the wireless network and a connection used in the wired network. As a result, the RTT in one connection is reduced, so that retransmission is quickly performed when a loss of the TCP segment occurs. Therefore, an improvement in throughput can also be expected in this respect.

However, since the end-to-end semantics of TCP are not preserved by relaying at the TCP layer as described above, the gateway device 90 is in communication during relaying at the TCP layer.
When the operation of 0 stops, even if the transmitting terminal recognizes that the data has arrived at the counterpart terminal, it may cause inconsistency that the data has not actually reached the counterpart terminal. Further, when all connections are relayed in the TCP layer, it is conceivable that the load on the gateway device 900 becomes too high and the performance is not actually improved.

In addition, the significance of relaying in the application layer is that it is possible to enter into the semantics of data to be transferred and perform relaying. For example, if data is cached at the time of relaying, when there is a request to relay the same data again, the caches 811 and 82 are cached.
By reading data from 1 and transmitting it, the relay operation can be omitted. Also, when the level of detail is expressed hierarchically with respect to certain information, it is composed of multiple levels of data from summary information with a small amount of data to detailed information with a large amount of data, and these data are stored in the server , Data of all layers is transferred from the server to the gateway device, but the layer is appropriately selected when transferring information from the terminal used by the user to the terminal according to the condition of the transmission path between the gateway devices. Data can be transmitted. Also, relay and transfer while performing any operation on the data, such as relaying while converting the information source compression encoding method to data, or relaying while performing encryption or decryption so,
A more advanced service can be provided to the terminal.

For this reason, as one of the guidelines for determining whether to relay in the TCP layer or whether to relay in the application layer, there are the following methods, for example.

If the application is desired not to change the TCP end-to-end semantics (when the ack is received, the transmitted data is received by the partner host)
Relay at the layer. For example, telnet.

If the application does not need to store TCP end-to-end semantics and does not have an application relay server corresponding to the gateway, relay is performed in the TCP layer. For example, smtp.

-It is not necessary to store the end-to-end semantics of TCP, and if the application has an application relay server corresponding to the gateway, relay is performed in the application layer. For example, ftp or http.

  Another example of decision guidelines is shown below.

If the application performs bursty data transfer that requires TCP throughput, relay is performed at the TCP layer. For example, ftp or http.

-In the case of an interactive application that does not require TCP throughput, relay is performed at the IP layer. For example, telnet.

A guideline for determining whether or not to relay by the TCP layer can be determined in advance by an application, or appropriately set according to the system configuration and the load status of the gateway device.

After determining the relay method, the four sets of source IP address, source port number, destination IP address, and destination port number for identifying the TCP connection are associated with the determined relay method, for example, FIG. Stored in the relay method table shown. Since the TCP connection is bi-directional, naming of the source / destination may be convenient, and when there is no entry in the relay method table by searching the source and destination of the information included in the IP datagram. , IP
The search may be performed by reversing the source and destination of the information included in the datagram. Further, the association may be a triple of a transmission source IP address, a destination IP address, and a flow ID, and the determined relay method may be stored in the relay method table shown in FIG.

When relaying at the TCP layer or higher, the same 4 as the identification information of the two TCP connections
A pair is assigned (source IP address, source port number,
Implicitly in the context of processing, such as whether the destination IP address and destination port number are used as identification information), whether the target IP datagram is input or output to the gateway device, or whether the source and destination are the same or reversed The two TCP connections can be distinguished by using information that can be understood. In addition, when relaying in the TCP layer or higher, two TCP connections can be identified by separate four groups. In that case, it is desirable to configure a table and perform a search accordingly.

When relaying at the IP layer, the input IP datagram is directly used as the IP output unit 402.
To pass. When relaying at the TCP layer or higher, the gateway device 900 sets the originally requested TCP connection by dividing it into a wireless TCP connection and a TCP connection. When the gateway apparatus 900 receives the first SYN segment for setting the TCP connection, it returns a SYN segment including an ack for the segment to the transmission source terminal. When the gateway apparatus 900 receives the ack for the SYN segment, the first TCP (or wireless TCP) is received. Set up a connection. On the other hand, in order to set up the second wireless TCP (or TCP) connection between the gateway apparatus 900 and the requested destination terminal, the gateway apparatus 900 transmits a new SYN segment. SY including ack for this
The setting of the second wireless TCP (or TCP) connection is completed through reception of the N segment and transmission of an ack for the N segment. In the application layer relay, since the second wireless TCP (or TCP) connection is set by the request of the relay servers 810 and 820, the application request is satisfied by reading the information already stored in the caches 811 and 812. In such a case, the second wireless TCP (or TCP) connection may not be set.

When relaying in the application layer in the gateway device of the present invention, the difference from the proxy used conventionally is that when the wireless terminal requests connection setting,
Even if the proxy is not explicitly specified, two TCP connections are connected and relayed in the application layer in the gateway device on the way, and the wireless terminal can operate without being aware of this.

The wireless TCP input unit 601 is an upper layer relay IP datagram (originally included in the TC
When the tag attached to the IP input unit is TCP layer relay, it is transferred to the TCP output unit 622 via the wireless → wired relay unit 611 of the TCP relay unit 610. In addition, when the TCP input unit 621 also receives the upper layer relay IP datagram, if the tag given by the IP input unit is a TCP layer relay, the wireless TCP output unit 602 via the wired → wireless relay unit 612. Pass it to. If the tag is an application layer relay,
An IP datagram is passed to the application corresponding to the TCP port number.

In addition, although the case where the wireless TCP connection and the TCP connection are relay-connected by the gateway device has been described as an example here, the wireless TCP connection and the wireless TCP connection are relay-connected in the communication between the wireless terminals, or the communication between the wired terminals The TCP layer and I
Relay connection can be performed in the same procedure, except for the F section.

In the TCP layer, the wireless terminals 1601 to 1605 have the wireless service areas of the gateway apparatuses 901 to 903 (the sum of the wireless service areas of the base stations accommodated in the gateway apparatuses).
TCP layer handoff when moving between. The TCP layer handoff is completed by reestablishing the state of all TCP (and wireless TCP) connections relayed for the wireless terminal in the new gateway device. The connection status here means
A set of four addresses and ports that identify each connection.

The first (second) not acked by the second (first) TCP (wireless TCP) connection
) Received data in the wireless TCP (TCP) connection.

The reception window, congestion window, acked sequence number, and transmitted sequence number of each TCP connection.

Etc.

As already described, since the mobility control unit 404 can notify the TCP handoff control unit 640 of the TCP layer that a handoff between the gateway devices is likely to occur, the TCP handoff control unit 640 starts preparations in response to this. By doing so, the time for handoff of the TCP layer can be shortened. Specifically, for example,
A TCP connection for TCP layer handoff information transfer is set between the current gateway device and the gateway device expected to move.

-Secure and initialize an area for holding the transfer data (for the maximum window size) and management information of each TCP connection.

The data received in the first (second) wireless TCP (or TCP) connection is also transferred to the gateway device expected to be the movement destination and stored in the secured transfer data area. If it overflows from the reserved area, it is discarded in ascending order of sequence number.

Make preparations.

When handoff actually occurs, the status of management information such as reception window, congestion window, acked sequence number, transmitted sequence number, etc. is determined, and this information is transferred to a new gateway device to move the gateway function When this is completed, TCP relay by a new gateway device is started. Wireless TCP ack is normal TCP
If it has the same cumulative nature as, a sent from the wireless terminal to the old gateway device
Even if ck cannot be received by the new gateway device, the state of the wireless TCP does not become unstable, and the throughput does not decrease. Therefore, before receiving ack for all data transmitted from the old gateway device, transmission of untransmitted data from the new gateway device may be started. By using this method, the interruption time of data transfer at the time of handoff can be reduced, so that the TCP throughput can be improved.

Even when the wireless terminals 1601 to 1604 are handed off between base stations accommodated in the same gateway device, such as the base stations 1401 to 1403 and the base stations 1404 to 1406,
As described above, using the fact that TCP ack is cumulative, the TCP output unit 622 does not pass through the new base station before receiving all ack for data transmitted through the old base station. Transmission of data to be transmitted may be started. In this case as well, the TCP state does not become unstable, and there is an effect that throughput does not decrease.

Next, a procedure for predicting and detecting that a wireless terminal moves and performs handoff across base stations by a gateway device that performs a TCP relay operation on the terminal or that handoff is completed is shown in FIG. This will be described with reference to FIG.

In the wireless terminal 1610 of FIG. 8, the electric field strength measurement unit 1804 continuously or periodically measures the received electric field strength of the radio wave transmitted from the base station, and notifies the control unit 1700 periodically. A BER (Bit Error Rate) measurement unit 1806 measures a bit error rate of a signal flowing from the receiver 1801 to the wireless IF input unit 311 for a certain period of time, and periodically notifies the control unit 1700 of the bit error rate. The electric field strength change notification unit 1701 of the control unit 1700 passes the received electric field strength obtained by the electric field strength measurement unit 1804 including the identifier of the own wireless terminal and the destination addressed to the gateway device to the IP output unit 512. As an identifier, for example, an IP address assigned to the wireless terminal 1610 can be used.

Similarly, the BER change notification unit 1702 of the control unit 1700 passes to the IP output unit 512 a message including the bit error rate obtained by the BER measurement unit 1806 and the identifier of the own wireless terminal and having the destination as the gateway device. The IP output unit transmits this message as an IP packet via the wireless IF output unit 312 and the transmitter 1802.

When the wireless terminal 1610 moves during wireless communication with a base station and comes to the vicinity of the boundary of the wireless service area of the base station, the reception field strength generally decreases and the BER increases. For this reason, the gateway device receives the received electric field strength and the BER notification transmitted from these wireless terminals, and when the movement control unit 404 detects a decrease in the received electric field strength and an increase in the BER described above,
It can be determined that the wireless terminal has moved near the boundary of the wireless service area of the base station with which it is communicating, and preparations for handoff can be started.

Similarly, in the base station 1400 shown in FIG. 9, the received field strength of the radio wave transmitted from the wireless terminal is measured by the field strength measuring unit 1854, or the bit error rate of the signal flowing from the receiver 1851 to the IF output unit 152 is determined. Since it can be measured by the BER measurement unit 1856, the gateway device predicts the handoff of the wireless terminal by transmitting the measurement result at the base station before handoff to the gateway device, or the measurement at the base station after handoff By transmitting the result to the gateway device, the gateway device can detect the completion of the handoff.

In addition to measuring the quality of the wireless transmission path in this way, a wireless transmission path between the wireless terminal and the base station is established by the wireless transmission / reception unit 1800 of the wireless terminal 1610 and the wireless transmission / reception unit 1850 of the base station 1400. It is also possible to implement such that the gateway device predicts the handoff of the wireless terminal or detects the completion of the handoff by detecting whether it is present and notifying the gateway device of the information.

Specifically, the wireless transmission path between the wireless transmission / reception unit 1800 of the wireless terminal 1610 and the wireless transmission / reception unit 1850 of the base station 1400 is assigned to the wireless transmission / reception unit or the wireless IF unit 310 as in the conventional wireless communication system. The establishment state is managed based on the physical address and MAC address. At this time, for example, in the radio transceiver 1850 of the base station 1400,
When the gateway device detects that the wireless transmission path with the wireless terminal performing TCP relay is disconnected, the wireless device identifier (for example, the gateway device can identify the physical address and MAC address of the wireless terminal) In order to convert it into (IP address), the wireless terminal address registration table shown in FIG. 10 is referred to, and a message including this identifier and the destination as the gateway device is transmitted via the IP output unit 552 and the wired IF output unit 152.

Upon receiving this message, the gateway device 900 recognizes that data transfer is not possible on the transmission path between the wireless terminal that has been performing TCP relay and the base station, and the handoff between the base stations or the gateway function The movement preparation operation can be started. Note that the wireless terminal address registration table shown in FIG. 10 may be configured to be installed in the gateway apparatus 900. In this case, the base station 1400 can notify the gateway apparatus of the physical address and MAC address of the wireless terminal. Can obtain the identifier (for example, IP address) of the wireless terminal by referring to the wireless terminal address registration table.

Conversely, when the base station detects that the wireless terminal 1610 has established a wireless transmission path with the destination base station, a wireless terminal identifier (for example, an IP address) that allows the gateway to identify the physical address or MAC address of the wireless terminal 10), a message with this identifier and the destination as the gateway device is transmitted via the IP output unit 552 and the wired IF output unit 152. The wireless terminal address registration table shown in FIG.

Upon receiving this message, the gateway device 900 can recognize that the transmission path between the wireless terminal 1610 and the movement-destination base station has been established, and can quickly start data transfer again. The wireless terminal address registration table shown in FIG.
In this case, if the base station 1400 notifies the gateway device of the physical address or MAC address of the wireless terminal, the gateway device refers to the wireless terminal address registration table to identify the wireless terminal identifier ( For example, an IP address) can be obtained.

Next, a procedure for the gateway device to detect the movement when the wireless terminal moves between base stations accommodated in different gateway devices will be described.

In a system that accesses the Internet from a wireless terminal via a base station and a gateway device, when the wireless service area of many base stations is configured with multiple subnets, the wireless terminal can be accessed even if the wireless terminal moves between these subnets. Mobile-IP or DHCP (Dynam) as a technology for connecting (capable of sending and receiving IP packets)
The case where ic Host Configuration Protocol is used will be described. In these techniques, when a wireless terminal moves to a different subnet, exchange with each function arranged on the network side is performed.

FIG. 11 shows a configuration example of a second communication network according to the second embodiment of the present invention. As shown in the figure, this communication network is a wired terminal 1001 connected to a wired network 1101.
, 1002 and 1003, connected to the wired network 1101 and indirectly connected to the base stations 1411 and 1412 via the router 1302, and indirectly connected to the base station 1 via the router 1303.
413 and 1414, a gateway device 911 connected to the wired network 1101, and indirectly connected to the base stations 1415 and 1416 via the router 1304, and the router 1
Gateway device 912 indirectly connected to base stations 1417 and 1418 via 305
And wireless terminals 1611 to 1614 that perform communication while moving between wireless service areas 1511 to 1518 respectively handled by the base stations 1411 to 1418. Here, base stations 1411 and 1412, 1413 and 1414, 1415 and 141 connected to the same router.
6, 1417 and 1418 are operated as the same subnet, and each of the routers 1302 to 1305 has a FA (Foreign Agent) function for providing various functions in the destination subnet by Mobile-IP. Assume that it is installed.

In Mobile-IP, the FA in each subnet (if DHCP, DHCP server in each subnet) periodically bases the subnet identifier or the address of the FA (or DHCP server) that can identify the subnet as shown in FIG. Broadcast via the station. The wireless terminals 1611 to 1614 periodically receive this notification information, so that when the wireless terminals 1611 to 1614 move to a subnet different from the subnet where they stayed before, they can be detected.

For example, when Mobile-IP is used, the care-of address of the packet addressed to the wireless terminal is notified from the FA while the wireless terminal is in the subnet, or the care-of address is displayed. The registration request is made to the FA to transfer the packet addressed to the wireless terminal to the wireless terminal. For example, in DHCP, while there is a wireless terminal in the subnet, a temporary IP address used to access the Internet from the wireless terminal is acquired from the DHCP server. In addition to these series of interactions,
If the identifier (for example, IP address) of the gateway device that accommodates the subnet is received from the FA or DHCP server and it is different from the identifier of the gateway device that was relaying the previous TCP connection, it is necessary to move the gateway function Is detected. At this time, the FA or DHCP server receives the T of the wireless terminal in the subnet.
The identifier of the gateway device that relays the CP connection is registered.

If the wireless terminal detects that the gateway function needs to be moved to a new (destination) gateway device (TCP layer handoff), the TCP handoff including the identifier of the own wireless terminal and the identifier of the previous gateway device The request is transmitted to the gateway device at the destination.

When the gateway device at the destination of the wireless terminal receives this handoff request at the TCP layer, it recognizes that the handoff between the base stations of the wireless terminal is completed, and that the gateway function needs to be moved subsequently. Requests transfer of data that has already been transmitted to the device and that has not been confirmed for delivery and status information of the TCP connection. Thereafter, the gateway function described above is moved.

Next, instead of the method in which the FA or DHCP server notifies the subnet identification number via the base station, a method in which the gateway device as shown in FIG. 12 notifies the identifier will be described. The configuration of the communication network shown in FIG. 12 is basically the same as the configuration of the first communication network shown in FIG.

Each gateway device 921 to 923 broadcasts its identifier (for example, IP address) via the base station, and the wireless terminal periodically receives the broadcast information.
If it is different from the identifier of the gateway device that has been performing the relay connection of the P connection, it is detected that the movement of the gateway device function is necessary. Also in this case, the subsequent TCP handoff procedure is the same as that described above.

Furthermore, the wireless TCP layer 600 and the TCP layer 620 of the gateway device 900 are TCP
P by persistent timer and keep alive timer
A method for processing the robot segment will be described with reference to FIGS.

A window probe that is typically generated by a persist timer
The reason for the segment is that the sending side checks whether the reason why the receiving side does not notify that the receiving window has been opened is because the ack for notifying that the receiving window has been opened has been lost, or because there is actually no room in the TCP buffer. To send to. The buffer of the wireless TCP layer 600 viewed from the wireless terminals 1601 to 1605 and the TCP layer 620 viewed from the wired terminals 1001 to 1003
Therefore, the wireless TCP layer 600 and the TCP layer 620 respond to the window probe segment as usual. That is, the reception window size to be notified is determined based on the free buffer amount, and the value is notified by ack. At the same time, the window probe segment may be relayed from the wired side to the wireless side or from the wireless side to the wired side via the TCP relay unit 610. Even if it is not relayed, the persistent TCP layer 600 and TCP layer 620 of the gateway device are persistent.
If the window is transmitted by moving the timer, the TCP layer 600 and TCP of the gateway device are not available in the TCP layer of the wireless terminals 1601 to 1605 or the TCP layer of the wired terminals 1001 to 1003. The state of the wrong reception window size remains in the layer 620 and data cannot be transmitted.

In general, a probe generated by a keep alive timer is TC.
The reason why no activity is seen in the P connection for a long time is transmitted to confirm whether the terminal has fallen or because the TCP connection has not been maintained because the terminal has been restarted after being dropped. Therefore, it is contrary to the original intention that the gateway device responds to these probes instead of the terminals. Therefore, the wireless TCP layer 300 and the TCP layer 620 of the gateway device do not respond to this probe, but simply a TCP.
Relay to the other via the relay unit 610. However, the wireless TCP layer 600 and the TCP layer 62
0 stores the contents of the relayed TCP segment, and if a response to this probe is returned, it relays as it is (as opposed to ack once for normal transmission).

In addition, when either the wireless side or the wired side TCP connection forming the relaying TCP connection is cut, the other side is also cut.

Next, the application relay servers 810 and 820 will be described with reference to FIG. When the application relay server 810 or 820 receives an IP datagram (application protocol data included therein) from the wireless TCP input unit 601 or the TCP input unit 621, the application relay server 810 or 820 performs a process defined in the application protocol, The TCP output unit 622 or the wireless TCP output unit 602 is requested to set the TCP (or wireless TCP) connection. Data requested by the user is cached 81
The case where the second TCP (or wireless TCP) connection does not exist is an example of setting the second TCP (or wireless TCP) connection.

Next, the wireless terminal 1600 will be described with reference to FIG. The wireless IF unit 300 of the wireless terminal 1600 implements a so-called data link layer function, but the wireless IF unit 300 according to the present invention.
Performs operations based on information of the TCP layer and the IP layer. Of particular note are the following points.

The wireless IF output unit 302 transmits an IP datagram dividing unit 303 that divides an IP datagram into a plurality of data link frames as shown in FIG. 4 and a plurality of data link frames that constitute a low-priority IP datagram. In the meantime, if a high priority IP datagram to be transmitted appears, the data link frame including the high priority IP datagram is preceded by the data link frame including the low priority IP datagram. And a priority control unit 304 for transmission. The IP datagram dividing unit 303 also has a TCP / IP header compression function. These operate in combination with the IP datagram reconstructing units 203 and 223 of the wireless IF input units 200 and 220 of the gateway device 900. As a high-priority IP datagram, it is assumed that the payload includes a pure ack (ack with only a header not including data), and this can improve the TCP performance as described above. .

In order to realize such a function, for example, the following method can be taken. The priority level is determined by the upper IP layer or the TCP layer, and the upper layer attaches a tag for identifying the priority to each IP datagram, or the data link in which each IP datagram is provided for each priority. If it is connected to the queue of the layer, it can also be identified by the priority control unit 304 of the data link layer. I
When a P datagram is queued to the data link layer queue, control passes to the data link layer.
An IP datagram dividing unit 303 divides the IP datagram into one or more data link frames. The link header includes an identifier that uniquely identifies the IP datagram (for an appropriate period of time). The priority control unit 304 requests the hardware to transmit a data link frame having a high priority by looking at the queue. Thereafter, control is once transferred to the upper layer. If the upper layer has an IP datagram to be transmitted, it is connected to the queue of the data link layer and the same processing as described above is performed. If the upper layer does not have an IP datagram to send,
By an interruption from the hardware of the transmission completion of the data link frame transmitted earlier,
Control is returned to the data link layer, and the priority control unit 304 requests the hardware to transmit one high-priority data link frame in the queue.

Note that when the bandwidth in the output direction from a wireless terminal for which this division / priority control method is particularly effective is narrow, the upper layer does not become a bottleneck for transmission processing, so the transmission data forms a queue. It is considered to be a data link layer. Therefore, it can be said that the data link layer is a suitable place for performing priority control of transmission data.

FIG. 5 shows that the second data link frame has a high priority IP datagram (pure ack
) Including data link frames.

TCP layer of the wireless terminal 1600 (TCP layer 700, wireless TCP layer 710 and TCP selection unit 7)
20) is different from a normal TCP layer in the following points.

The wireless TCP layer 700 realizes a transport layer protocol improved for wireless use as described above. When the TCP connection is set, if the other party operates as a normal TCP, the control of the connection is taken over by the TCP layer 710.

The TCP selection unit 720 performs communication using normal TCP according to information that can specify or estimate the application 860 without an explicit request by the wireless compatible application 850 or without an explicit request, or performs communication using the wireless TCP. To decide. If normal TCP here, there is no relay beyond the TCP layer by the gateway device,
In the case of wireless TCP, a TCP connection is set up assuming that there is relaying beyond the TCP layer by the gateway device. The determination criteria for the relay method are the same as those described in the description of the gateway device.

In the application layer of the wireless terminal 1600, the wireless compatible application 850 is a TC.
The P selection unit 720 has a function of explicitly requesting selection of wireless TCP or TCP. The application 860 does not make an explicit request to the TCP selection unit 720.

Next, FIG. 13 shows the configuration of a third communication network according to the third embodiment of the present invention.
The communication network of the present embodiment is an example in which a router is used to distribute the load of transport layer relay or application layer relay to a plurality of gateway devices.

A router 1311 interconnects base stations 1421 to 1426 that respectively handle a wired network 1111 that accommodates the wired terminals 1011 to 1013, gateway devices 931 to 933, and wireless service areas 1521 to 1526. The router 1311 includes wireless terminals 1621 to 1624.
Are routed by a method to be described later so as to transmit / receive IP datagrams to / from the wired terminals 1011 to 1013 via any one of the gateway devices 931 to 933 assigned thereto.

FIG. 14 shows the configuration of the router 1311. As shown in the figure, in this router 1311, the wired IF units 180 and 190 are connected to a wired network 1111 or gateway devices 931 to 933.
The wireless IF units 280 and 290 are connected to the base stations 1421 to 1426.
The IP layer 480 outputs IP datagrams input from these IFs to appropriate IFs according to the routing table of the IP relay unit 483.

The router 1311 is characterized in that the IP relay unit 483 has a correspondence table 486 of the wireless terminals 1621 to 1624 and the gateway devices 931 to 933.

The association between the wireless terminals 1621 to 1624 and the gateway devices 931 to 933 is performed when it is detected that the wireless terminals 1621 to 1624 are in the wireless service areas 1521 to 1526 or when the wireless terminals 1621 to 1624 are joined. Can do. In the former case, an IP datagram in which the base station notifies the detection of new wireless terminals 1621 to 1624 is transferred to the mobility control unit 484 by the datagram filter 485 of the router 1311. The movement control unit 484 attaches the correspondence between the notified wireless terminals 1621 to 1624 and the gateway devices 931 to 933 according to a certain rule, and registers the contents in the correspondence table 486. A certain rule is defined with the goal of equalizing the load based on the load of the gateway devices 931 to 933 in the immediately preceding period, for example.

As described above, the gateway devices 921 to 923 shown in FIG.
~ 1408 is notified of the identifier (for example, IP address) of the gateway device, while the wireless terminals 1601 to 1604 periodically receive this notification information to recognize the gateway device that accommodates the base station. it can. When there are a plurality of gateway apparatuses that accommodate one base station, for example, as shown in FIG. 15, the identifier of each gateway apparatus is notified via the base station, and all of the wireless terminals that have received the notification information receive them. The service provision request signal is transmitted to the gateway device. The gateway device that has received the request transmits a service provision response signal to the wireless terminal. For example, the gateway device that has transmitted the response earliest can determine that the load on the gateway device is light, and this is associated with the wireless terminal. It can also be defined as a device.

When the association between the wireless terminals 1621 to 1624 and the gateway devices 931 to 933 is performed during the subscription procedure of the wireless terminals 1621 to 1624, a remote network management device (not shown) sets the correspondence table 486. The setting may be performed by a method performed via the movement control unit 484 as described above, or may be performed by a method performed via a management application (not shown) in the router 1311.

The routing of the IP datagram using the correspondence table 486 set in this way will be described in detail below.

Transmission of IP datagrams from the wired terminals 1011 to 1013 to the wireless terminals 1621 to 1624 is divided into several cases.

(W1) A case where the IP addresses of the wireless terminals 1621 to 1624 are directly written as destinations in the header of the IP datagram transmitted by the wired terminals 1011 to 1013.

(W2) IP transmitted from the wired terminals 1011 to 1013 using so-called tunneling technology
The header of the datagram is the router 1311 or gateway device 931-93 as the destination.
3. An IP datagram (or a modification thereof) is further encapsulated in the IP payload, and the addresses of the wireless terminals 1621 to 1624 are described as the destination of the header of the encapsulated IP datagram. .

(W2-1) When the router 1311 is a destination address.

(W2-2) When gateway devices 931-933 (corresponding to wireless terminals 1621-1624, respectively) are destination addresses.

When the router 1311 routes IP datagrams from the wired terminals 1011 to 1013 to the wireless terminals 1621 to 1624, it is necessary to perform an operation different from normal (W
This is the case of 1) and (W2-1). In the case of (W1), the IP relay unit follows the correspondence table 486,
The IP datagram is routed to gateway devices 931 to 933 corresponding to the wireless terminals 1621 to 1624 that are destinations of the header of the IP datagram. In the case of (W2-1), the IP datagram encapsulated by the IP input unit 481 of the router 1311 is extracted,
Thereafter, the same as (W1) is performed. In the case of (W1), the IP datagram transmitted after the conversion / relay by the gateway devices 931 to 933 includes the wireless terminals 1621 to 1624 in the header as in the case of the transmission from the wired terminals 1011 to 1013. IP datagrams with destination addresses must be routed to different routes. Since the former and the latter can be distinguished by information such as the difference in input IF and the MAC address of the transmission source, such routing is possible.

Transmission of IP datagrams from the wireless terminals 1621 to 1624 to the wired terminals 1011 to 1013 is divided into several cases.

(R1) When the IP addresses of the wired terminals 1011 to 1013 are directly written as destinations in the headers of IP datagrams transmitted by the wireless terminals 1621 to 1624.

(R2) IP transmitted by wireless terminals 1621 to 1624 using so-called tunneling technology
The header of the datagram is the router 1311 or gateway device 931-93 as the destination.
3. An IP datagram (or a modification thereof) is further encapsulated in the IP payload, and the addresses of the wired terminals 1011 to 1013 are described as destinations of the header of the encapsulated IP datagram. .

(R2-1) When the router 1311 is a destination address.

(R2-2) When gateway devices 931-933 (corresponding to wireless terminals 1621-1624, respectively) are destination addresses.

When the router 1311 routes IP datagrams from the wireless terminals 1621 to 1624 to the wired terminals 1011 to 1013, it is necessary to perform an operation different from normal (R
This is the case of 1) and (R2-1). In the case of (R1), the IP relay unit performs I
The IP datagram is routed to the gateway devices 931 to 933 corresponding to the wireless terminals 1621 to 1624 that are the transmission source of the header of the P datagram. In the case of (R2-1),
The IP datagram encapsulated by the IP input unit 481 of the router 1311 is taken out, and thereafter the same as (R1) is performed. In the case of (R1), the IP datagrams transmitted after the conversion / relay by the gateway devices 931 to 933 include the wireless terminals 1011 to 1013 in the header in the same manner as those transmitted from the wireless terminals 1621 to 1624. IP datagrams with destination addresses must be routed to different routes. Since the former and the latter can be distinguished by information such as the difference in input IF and the MAC address of the transmission source, such routing is possible.

Next, FIG. 16 shows the configuration of a fourth communication network according to the fourth embodiment of the present invention.
The configuration of the communication network according to the present embodiment is characterized in that the gateway device is duplicated in order to improve the reliability of the gateway function. Except for the duplex gateway device, the configuration of the third communication network in FIG. 13 is applied.

A router 1312 interconnects base stations 1421 to 1426 that respectively handle the wired network 1111 that accommodates the wired terminals 1011 to 1013, gateway devices 944 and 945, and wireless service areas 1521 to 1526. The router 1312 includes wireless terminals 1621 to 1624.
However, routing is performed in a manner similar to that described in the configuration of the third communication network so as to transmit and receive IP datagrams with the wired terminals 1011 to 1013 via the gateway devices 944 and 945.

The router 1312 of the fourth communication network configuration includes an IP datagram transmitted from the wired terminals 1011 to 1013 to the router 1312 with the wireless terminals 1621 to 1624 as the final destination, and the wireless terminals 1621 to 1624 connected to the wired terminals 1011 to 1013. The IP datagram transmitted to the router device 1312 as the final destination is converted into each gateway device 944, 94.
5 is different from the router 1311 having the configuration of the third communication network in that it broadcasts to 5.

The router 1311 has an interface for each gateway device. However, the router 1312 has a physical connection difference that the gateway devices 944 and 945 are accommodated by a shared media network (for example, Ethernet (R)). Not right.

A method in which the router 1312 broadcasts to the gateway devices 944 and 945 will be described. In the case shown in the configuration of the third communication network, (W2-2) and (R2-2) are IP addresses that include gateway devices 944 and 945 in the host group because the gateway device is the destination address. The destination address may be used. This host group is set in advance by some method. When resolving the IP multicast address to the MAC address of the shared media network, gateway devices 944 and 945 are used.
To the multicast address of the shared media network including This address resolution method is the same as in ordinary IP multicast. Here, in the configuration of the gateway devices 944 and 945 shown in FIG. 17, the broadcast receiving function 113 has a function of receiving a frame having a multicast address of the shared media network.

In the case of (R1), (R2-1), (W1), and (W2-1), the destination is a single cast IP address, but this single cast IP address is resolved to the MAC address of the shared media network. At this time, it is only necessary to resolve the multicast address of the shared media network including the gateway devices 944 and 945. In this address resolution method, a single cast IP address is a single cast M address.
This is different from the usual method of resolving to an AC address.

Since the network connecting the router 1312 and the gateway devices 944 and 945 is a shared medium, even if the router 1312 resolves to a single cast MAC address, the gateway device 944 adds M to the gateway device 945 in addition to the frame addressed to itself.
Broadcast of the wired IF input unit 111 of the gateway devices 944 and 945 is also received so that the gateway device 945 also receives a frame having the MAC address addressed to the gateway device 944 in addition to the frame addressed to itself. If the reception function 113 is set, the same effect can be obtained.

FIG. 17 shows a configuration of the gateway device 944 or 945 that can be duplicated. Each gateway device 944, 945 receives a broadcast reception function 1 in the wired IF input unit 111 of the wired IF unit 110.
13, the wired IF output unit 112 is provided with a broadcast transmission function 114. For example, an Ethernet (R) IF card, which is a shared media network, has such a broadcast function. However, in the present invention, an IP datagram (TCP or wireless) to be transmitted by a frame having a single MAC destination MAC address is usually used. Including TCP segment)
Is broadcast by a frame having a multicast destination MAC address.

The IP layer 410 differs from the IP layer 400 of the gateway device 900 in that it does not have a movement control unit and in that it is controlled by the duplexing control unit 1900, but the former difference is not essential. A dual gateway device is also possible. Redundant control unit 1
When 900 is instructed to operate as the IP layer of the primary gateway device, the datagram to be relayed is relayed by the IP layer. When it is instructed to operate as the IP layer of the secondary gateway apparatus by the duplex control unit 1900, even if it is normally determined to be relayed by the IP layer, the datagram is silently relayed. Discard.

The wireless TCP layer 650, the TCP layer 670, and the TCP relay unit 660 are respectively connected to the wireless TC.
Compared with the P layer 600, the TCP layer 620, and the TCP relay unit 610, the duplex control unit 190
The difference is that necessary information is given to 0 and control by the duplexing control unit 1900 is received. This will be described in detail below.

First, a case will be described in which the gateway device 944 is a primary gateway device, the gateway device 945 is a secondary gateway device, and a TCP connection between the wired terminal 1011 and the wireless terminal 1621 is relayed.

At this time, the wired terminal 1011 that receives and responds to the TCP segment and the primary gateway device 944 have a TCP peer relationship, and the wireless terminal 1621 that receives and responds to the wireless TCP segment and the primary gateway device 944 have a wireless TCP peer relationship. It is in. The secondary gateway device 945 receives these TCP segment exchanges and confirms the contents. However, unless the primary gateway device 944 fails, the secondary gateway device 945 does not respond to the received TCP segment and is not in a peer relationship. .

Assume that the wireless terminal 1621 makes a connection setting request for wireless TCP. Wireless TC
The SYN segment of P is broadcast to the primary gateway device 944 and the secondary gateway device 945 through the path a in FIG. As a TCP connection setting request, the primary gateway device 944 sends a T to the wired terminal 1011 and the secondary gateway device 945 via the route d.
Broadcast the SYN segment of the CP. The determination unit 1901 of the secondary gateway device 945
This reception is expected when the wireless TCP SYN segment is received, and it is determined that the primary gateway device 944 is operating normally by receiving the expected segment.

If the expected segment is not received for a certain period, the determination unit 1901 sends an operation confirmation message to the primary gateway apparatus 944 via the path f. On the other hand, if the primary gateway device 944 does not return a response through the route e, the determination unit 1901 of the secondary gateway device 945 determines that the primary gateway is faulty, and the switching control unit 1902 sets the own device as the primary gateway device. Instruct to configure. The switching control unit 1902 instructs the wireless TCP layer 650, the TCP relay unit 660, and the TCP layer 670 to operate as a primary gateway device. In the present case, the TCP layer 670 transmits a TCP SYN segment to the wired terminal 1011.

The process returns to the case where the primary gateway device 944 is operating normally again. Wired terminal 101
The TCP SYN / ACK segment returned by 1 is broadcast by the router 1312 to the primary gateway device 944 and the secondary gateway device 945 through the path c. The primary gateway device 944 receives this, and the wired terminal 1011 and the secondary gateway device 94 via the route d.
Broadcast the ACK segment to 5. The determination unit 1901 of the secondary gateway device 945 determines the operation state of the primary gateway device 944 based on the presence / absence of this reception, and performs switching if necessary.

Further, the primary gateway device 944 returns a wireless TCP SYN / ACK message to the wireless terminal 1621 and the secondary gateway device 945 through the path b. Based on the presence / absence of the reception, the determination unit 1901 of the secondary gateway device 945 determines the primary gateway device 9.
It is the same that the operation state of 44 is judged and switched if necessary. The ACK segment of the wireless TCP transmitted by the wireless terminal 1621 is broadcast by the router to the primary gateway device 944 and the secondary gateway device 945 through the path a.

At this point, a bidirectional TCP connection between the wireless terminal 1621 and the wired terminal 1011 that is relayed by the primary gateway device 944 is established.

Consider a case where data is transferred from the wired terminal 1011 to the wireless terminal 1621. Wired terminal 1
A TCP segment including data to be transmitted from 011 is broadcast to the primary gateway device 944 and the secondary gateway device 945 through a path c. Primary gateway device 944
Broadcasts an ACK segment for confirming reception of the data to the wired terminal 1011 and the secondary gateway device 945 through the route d. The determination unit 1901 of the secondary gateway device 945 determines the operating state of the primary gateway device 944 based on the presence / absence of reception of this ACK segment, and performs switching if necessary. Further, the primary gateway device 944
Transmits a wireless TCP segment including data to be transmitted to the wireless terminal 1621 through a path b.
To the secondary gateway device 945. Determination unit 190 of secondary gateway device 945
Since 1 is expecting a wireless TCP segment including data, the operation state of the primary gateway device 944 is determined based on the presence / absence of reception, and switching is performed if necessary. The wireless terminal 1621 transmits a wireless TCP ACK segment for confirming reception of this data,
Broadcast to the primary gateway device 944 and the secondary gateway device 945 on the route a. This A
If CK is not received, the primary gateway device 944 should perform retransmission due to timeout. When the primary gateway device 944 should not perform retransmission, the determination unit 1901 of the secondary gateway device 945 checks the operating state of the primary gateway device 944, performs switching if necessary, and performs retransmission.

Consider a case where the wireless terminal 1621 requests disconnection of a TCP connection. Wireless terminal 16
21 broadcasts the FIN segment of the wireless TCP to the primary gateway device 944 and the secondary gateway device 945 through the path a. The primary gateway device 944 broadcasts the TCP FIN segment to the wired terminal 1011 and the secondary gateway device 945 through the route d. The determination unit 1901 of the secondary gateway device 945 determines the operation state of the primary gateway device 944 based on the presence / absence of reception of the FIN segment, and performs switching if necessary. The TCP ACK segment returned by the wired terminal 1621 is broadcast to the primary gateway device 944 and the secondary gateway device 945 by the router 1312 through the path c. The primary gateway device 944 broadcasts the wireless TCP ACK segment for the FIN to the wireless terminal 1621 and the secondary gateway device 945 through the path b. The determination unit 1901 of the secondary gateway device 945 determines the operating state of the primary gateway device 944 based on whether or not the ACK segment is received, and performs switching if necessary.

Next, a procedure for associating a communication between a wireless terminal and a wired terminal, between wireless terminals, or between wired terminals with a gateway device that performs relay connection in a TCP layer or an application layer with each communication is shown in FIGS. The description includes the configuration of FIG.

Note that, when a message is transferred on the communication network having the configuration shown in FIG. 13, an IP packet is used and data transfer is performed using an arbitrary transport layer protocol.

Here, FIG. 9 shows the base stations 1421 to 1426 of FIG.
400). The base station 1400 includes an electric field strength change notification unit 1
751, a BER (bit error rate) change notification unit 1752, a control unit 1750 including a terminal movement control unit 1753, a receiver 1851 including a field strength measurement unit 1854, a transmitter 1852, and these for sharing an antenna 1855 Wireless transceiver 1850 including duplexer 1853, B
ER measurement unit 1856, IP layer 550 including IP input unit 551 and IP output unit 552, wired I
The wired IF unit 150 includes an F input unit 151 and a wired IF output unit 152. In addition,
In the figure, solid arrows indicate data flow, and broken arrows indicate control flow.

The electric field strength measuring unit 1854 measures the received electric field strength of radio waves transmitted from the wireless terminals 1621 to 1624 and periodically notifies the control unit 1750 of the received electric field strength. The BER measurement unit 1856 determines the bit error rate of the signal flowing from the receiver 1851 to the wired IF output unit 151 to each wireless terminal 162.
1 to 1624 is measured, and the control unit 1750 is periodically notified.

Note that the received electric field strength and the bit error rate are examples of information indicating a wireless communication state between the wireless terminal and the base station. The electric field strength change notification unit 1751 of the control unit 1750 includes the electric field strength measurement unit 1.
A message including the identifiers of the wireless terminals 1621 to 1624 corresponding to the received electric field strengths of the wireless terminals 1621 to 1624 obtained by 854 and having the destination as the router 1311 is passed to the IP output unit 552.

Similarly, the BER change notification unit 1752 of the control unit 1750 has wireless terminal 1621-1 corresponding to the bit error rate of each wireless terminal 1621-1624 obtained by the BER measurement unit 1856.
A message including the identifier of 624 and having the destination as the router 1311 is passed to the IP output unit 552.

As the identifier, for example, an IP address assigned to the wireless terminals 1621 to 1624 can be used. As a message transferred to the router 1311 via the IP output unit 552, a new ICMP (Internet Control Message P) is used.
rotocol) message may be defined. That is, as an ICMP message for notifying information indicating a wireless communication state such as a received electric field strength or a bit error rate and an identifier of a wireless terminal, a type and a code are newly assigned, and information contents (received electric field strength or bit The format of the error rate and wireless terminal identifier) is defined. This message may be periodically notified from the base station 1400 to the router 1311 or may be notified only when the received electric field strength and the bit error rate exceed predetermined thresholds.

FIG. 14 shows a configuration example of the router 1311 shown in FIG. Router 1311
Broadly divided, a plurality of wired IF units 1 (only two of them are shown in FIG. 14) for connecting the wired network 1111 and the plurality of gateway devices 931 to 933 one by one.
80 and 190 and a plurality of base stations 1421 to 1426 connected one by one (FIG. 14).
In the figure, only two of them are shown) and the wireless IF units 280 and 290 and the IP layer 480 are included.

The wired IF units 180 and 190 include a wired IF input unit (181 and 191) and a wired IF output unit (
182 and 192), and the wireless IF units 280 and 290 are connected to the wireless IF input unit (28).
1, 291) and wireless IF output units (282, 292).

The IP layer 480 includes an IP input unit 481 having a datagram filter 485, an IP output unit 482, an IP relay unit 483 storing a correspondence table 486, and a movement control unit 484.

A message (for example, an ICMP message) for notifying the wireless communication state transmitted from the base station reaches the IP input unit 481 via the wireless IF input unit 281 or 291. Then, the IP input unit 481 recognizes that the message is an ICMP message for notifying the wireless communication state by the datagram filter 485 (it can be identified by the ICMP type and code). Then, the message (IP datagram) to be transferred to any one of gateway devices 931 to 933 that relays the transport layer connection terminated at the wireless terminal identified by the identifier included in the message. Recognize and pass to IP relay unit 483.

The correspondence table 486 of the IP relay unit 483 shows the correspondence between the IP addresses of the wireless terminals 1621 to 1624 and the IP addresses of the gateway devices 931 to 933 that relay the trans-layer port connection terminated at the wireless terminals 1621 to 1624. The relationship is shown.

This correspondence is assumed to be attached as follows, for example. Wireless terminal 1621-
When the terminal mobility control unit 1753 of the base stations 1421 to 1426 indicates that the 1624 is newly found in any of the wireless service areas 1521 to 1526 (including when the power is turned on), the router 13
11, the mobile control unit 484 associates the wireless terminal with any one of the gateway devices 931 to 933 according to a certain rule.

Now, the IP relay unit 483 obtains one of the IP addresses of the gateway devices 931 to 933 corresponding to the IP address of the wireless terminal included in the message from the correspondence table 486. The IP address of this gateway device is used as a new destination for the message.
Write to the P header and pass to IP output unit 482.

The IP output unit 482 transmits the message to any one of the gateway devices 931 to 933 via the wired IF output unit (182 or 192) corresponding to the destination.

Since the destination of the message input to the IP input unit 481 is the address of the router 1311, it should be handed over to the upper layer. Accordingly, the processing in the IP relay unit 483 as described above (identifying the gateway device corresponding to the wireless terminal having the identifier included in the message with reference to the correspondence table 486, the message to the specified gateway device) The processing for transfer) may be performed in an upper layer. That is, a part for processing the message may be provided in an upper layer without passing to the IP relay unit 483.

Next, a procedure for adaptively controlling the transport layer protocol of the gateway device that relay-connects communication with the wireless terminal according to the wireless communication state between the wireless terminal and the base station is shown in FIG.
9 will be used for explanation. FIG. 19 shows a configuration example of the gateway devices 931 to 933 (hereinafter collectively referred to as the gateway device 930) of FIG. The gateway device 930 is roughly divided into a wired IF unit 120, an IP layer 420, a TCP layer 620, and a T.
A CP relay unit 610 and a wireless TCP layer 630 are configured.

The wired IF unit 120 includes a wired IF input unit 121 and a wired IF output unit 122.
The router device 1311 is connected. The IP layer 420 includes an IP input unit 421 including a datagram filter 425, an IP output unit 422, an IP relay unit 423, and a wireless communication state reception processing unit 426.

The TCP layer 620 includes a TCP input unit 621 including a segment filter 623 and a TCP output unit 622. The wireless TCP layer 630 includes a wireless TCP input unit 631 including a segment filter 633, a wireless TCP output unit 632, and a wireless communication state adaptive control unit 634.

The TCP relay unit 610 includes a relay unit 611 that converts a wireless transport layer protocol into a wired transport layer protocol, and a relay unit 612 that converts a wired transport layer protocol into a wireless transport protocol.

The message transferred from the router 1311 to the gateway device 930 passes through the wired IF input unit 121 of the gateway device 930 and reaches the IP input unit 421.

When the IP input unit 421 recognizes that the input message is a message for notifying the wireless communication state by the datagram filter 425, the IP input unit 421 sends this to the wireless state reception processing unit 426.

The wireless state reception processing unit 426 extracts an identifier (for example, IP address) of the wireless terminal in the message and information about the wireless communication state (for example, reception field strength or bit error rate),
This is notified to the wireless TCP layer 630.

The wireless communication state adaptive control unit 634 of the wireless TCP layer 630 adaptively changes the operation of the wireless TCP based on the information regarding the wireless communication state. For example, when the bit error rate is higher than a certain threshold (or when the received electric field strength is smaller than a certain threshold), the maximum size of the wireless TCP segment to be transmitted is reduced, and the bit error rate is larger than the certain threshold. Radio T to be transmitted when the received electric field strength becomes larger than a certain threshold value.
Increase the maximum size of the CP segment.

Such a transport layer connection control instruction (for example, an instruction to change the size of the TCP segment) acts on, for example, the wireless TCP output unit 632 and thereafter the TCP relay unit 6.
The TCP segment sent from the 10 wired to wireless relay units 612 is output from the wireless TCP output unit 632 with the size determined by the wireless communication state adaptive control unit 634, and the IP output unit 422 and the wired IF output unit 122 to the base station.

Up to now, based on a message for notifying the wireless communication state transmitted from any of the base stations 1421 to 1426 to the router 1311, the router 1311 is identified by an identifier included in the message. Associate the terminal with one of multiple gateway devices (identification of the gateway device to which the message is transferred to notify the wireless communication status)
I have explained the case.

Next, the case where the base stations 1421 to 1426 associate the wireless terminal with one of a plurality of gateway devices will be described. FIG. 20 shows another configuration example of base stations 1401 to 1406 (hereinafter collectively referred to as base station 1400). In addition, the same code | symbol is attached | subjected to FIG. 9 and an identical part, and a different part is demonstrated. That is, in the configuration shown in FIG.
50 includes a correspondence table 1754.

Correspondence table 1704 shows correspondence between identifiers (for example, IP addresses) of wireless terminals 1621 to 1624 and IP addresses of gateway devices 931 to 933 that relay transport layer connections terminated at wireless terminals 1621 to 1624. It is shown.

This correspondence is assumed to be attached as follows, for example. First, the router device 1
It is assumed that 311 already has a correspondence relationship in the correspondence table 486 by a separately defined method. Any of the terminal movement control units 1753 of the base stations 1421 to 1426 is connected to the wireless terminals 1621 to 1624.
When a message for notifying that one of the above has been found is transmitted to the router 1311,
The mobility control unit 484 of the router 1311 refers to the correspondence table 486 and selects any of the gateway devices 931 to 933 that relay the transboat layer connection terminated at the wireless terminal having the identifier (IP address) included in the received message. The identifier (IP address) is searched.

Then, a predetermined response message including the identifier of the searched gateway device is transmitted to the base station that transmitted the message for notifying that the wireless terminal has been found first.

In the base station, a response message from the router 1311 is sent to the wired IF input unit 151, the IP
When the gateway device identifier is extracted from the response message received via the input unit 551, the terminal movement control unit 1753 registers the correspondence relationship between the gateway device identifier and the wireless terminal in the correspondence table 1754.

On the other hand, the electric field strength change notification unit 1751 of the control unit 1750 generates a message including the received electric field strength of the radio wave transmitted from the wireless terminal obtained by the electric field strength measuring unit 1854 and the identifier of the wireless terminal. It is passed to the output unit 552. At that time, the electric field strength change notification unit 175
1 from the correspondence table 1754, the identifier of the gateway device corresponding to the identifier of the wireless terminal (
IP address) and set it as the destination of the generated message.

Similarly, the BER change notification unit 1752 of the control unit 1750 generates a message including the bit error rate of the wireless terminal obtained by the BER measurement unit 1856 and the identifier of the wireless terminal, and passes the message to the IP output unit 552. At that time, the BER change notification unit 1752 reads from the correspondence table 1754,
The identifier (IP address) of the gateway device corresponding to the identifier of the wireless terminal is searched and set as a destination in the generated message.

This message is sent to the router 1311 via the IP output unit 552 and the wired IF output unit 152.
Is routed to one of the gateway devices 931 to 933 specified by the IP address included in the IP packet in the same manner as a normal IP packet. As described above, the gateway devices 931 to 933 that have received this message are configured so that the wireless TCP state 630 adaptive control unit 634 adaptively controls the operation of the wireless TCP based on the information on these wireless communication states. change.

Next, a control option processing method used when a TCP connection establishment request is made from a wireless terminal or a wired terminal will be described with reference to FIGS. FIG. 21 shows a configuration of a gateway apparatus according to an embodiment of the present invention. The same parts as those in FIG. 1 are denoted by the same reference numerals, and different parts will be described here.

For example, it is assumed that the gateway device 901 has the configuration shown in FIG. 20 in the configuration of the communication network of FIG. At this time, the gateway device 901 requested the option h.
When a packet for establishing a CP connection is received from the terminal 1001 in the wired network 1101 (assuming that the option h indicates path MTU discovery), the gateway device 901 sends an answer to the option to h. In addition to the connection to the terminal 1001, the connection with the terminal 1001 is established. At this time, what is requested as a connection option is recorded in the option table 683.

Next, the gateway device 901 is a partner with which the terminal 1001 wants to establish a connection.
For example, the operation for establishing a connection with the wireless terminal 1601 is started. The TCP handoff control unit 640 in the gateway device 901 refers to the option table 683 when generating a packet for establishing a connection. Thereby, the gateway device 901 confirms that the option h is requested, and searches for an MTU on the route. However, since the packet size in the wireless link is generally smaller than the packet size in the wired link, if the MTU here is treated as an MTU on the path between the wireless terminal 1601 and the terminal 1001, it is necessary in the wired network. The above data division is performed, and as a result, the link utilization efficiency decreases.
Therefore, h is treated as unnecessary when establishing a connection with a wireless terminal. Therefore,
The TCP handoff control unit 640 in the gateway device 901 transmits the wireless TC to the wireless terminal 1601 without adding anything to the packet option for establishing the TCP connection.
The request is transmitted to the wireless TCP output unit 602 in the P600.

The wireless terminal 1601 that has received the packet for establishing the TCP connection understands that there is no option, and sends a delivery confirmation / response packet to the gateway device 9.
Send to 01. As a result, the connection between the wireless terminal and the gateway device 901 is established without any option.

As described above, for example, when the connection between the wireless terminal and the wired terminal is divided and set, the option setting can be flexibly changed depending on the communication link status and the like, so that the communication link can be used efficiently.

Next, a procedure in which a wireless terminal moves between base stations accommodated in different gateway devices and a gateway function is moved (handoff by TCP layer) between these gateway devices will be described with reference to FIG. FIG. 22 shows a configuration of a gateway apparatus according to an embodiment of the present invention. The same parts as those in FIG. 1 are denoted by the same reference numerals, and different parts will be described here.

When a wireless terminal moves between base stations accommodated in different gateway devices, and a gateway function moves (handoff by TCP layer) between these gateway devices,
The TCP handoff control unit 640 of the gateway device 960 has two Ts that are TCP relaying.
CP connection (for example, between gateway device 960 and wireless terminal, gateway device 96
Reference is made to state transition variables 689 and 694 indicating the current TCP connection state (between 0 and the wired terminal).

The state transition variables 689 and 694 of each TCP connection are both ESTABLIS
In the case of HED, it is detected that two TCP connections for TCP relay have been established and are in a data transfer state, so that a gateway function can be realized in a new gateway device even after the wireless terminal has moved. A series of handoff operations by the TCP layer described above are performed.

On the other hand, when any of the state transition variables 689 and 694 of each TCP connection is not ESTABLISHED, the gateway device 960 has each (CL
A process of cutting the TCP connection (not OSED) is performed. Of course, both CLOSE
If it is D, no operation is required.

By performing handoff between gateway devices according to such a criterion, it is possible to avoid having a gateway operation procedure in an abnormal state transition, so that simplification of the system configuration of the gateway device can be expected.

Next, a TCP connection management procedure in the wireless terminal when the wireless terminal performs handoff between different base stations will be described with reference to FIG. FIG. 23 shows a configuration of a wireless terminal according to an embodiment of the present invention. The same parts as those in FIG. 3 are denoted by the same reference numerals, and different parts will be described here.

When the wireless terminal 1620 disconnects the wireless transmission path to perform handoff between different base stations, the wireless TCP state transition variable 734 indicating the current TCP connection state in the wireless TCP layer of the wireless terminal 1620 is referred to. Is SYN_SENT, SYN_RC
If either VD or LISTEN, that is, in the middle of establishing a connection, the wireless terminal 1620 performs an operation of disconnecting this connection, and also indicates that the connection has been disconnected, a TCP handoff control unit 740. It is recorded in the handoff disconnection variable 741 at the time of connection establishment.

After this, the fact that the handoff of the wireless terminal 1620 has been completed and the wireless transmission path has been established is
When the handoff control unit 740 detects, it refers to the above-described handoff disconnection variable 741 at the time of connection establishment, and starts reestablishing the TCP connection if it is recorded that the connection has been disconnected.

As described above, even when the wireless terminal 1620 is in the middle of establishing the TCP connection, even if the connection is disconnected by handoff, the connection can be reestablished automatically after the handoff. It is possible to omit performing the operation for re-establishment.

Next, a data flow control procedure when the wireless transmission transmission line between the wireless terminal and the gateway device is disconnected due to handoff, for example, will be described with reference to FIGS. FIG. 24 shows a configuration of a gateway device according to an embodiment of the present invention. The same parts as those in FIG. 1 are denoted by the same reference numerals, and different parts will be described here. FIG. 25 shows the configuration of a wireless terminal according to an embodiment of the present invention. The same parts as those in FIG. 3 are given the same reference numerals, and different parts will be described here. 2 is configured as a gateway device 970 in FIG. 24, and the wireless terminal 1604 in FIG. 2 is configured as a wireless terminal 1630 in FIG.

When the wireless terminal 1604 communicates with the wired terminal 1001 via the gateway device 902 by dividing and setting the connection, when the handoff starts from the wireless service area 1505 covered by the base station 1405 to the wireless service area 1506 covered by the base station 1406 The TCP handoff control unit in the gateway device 970 is the packet generation unit 6 in the TCP layer 695.
In 99, a packet having no data with the window size field set to 0 is generated, and this packet is transmitted to the wired terminal 1001 via the TCP output unit 697. Wired terminal 1
When 001 receives a packet notifying that the window size is 0, it interprets that the reception buffer of the partner wireless terminal 1604 is not empty, and thereafter the wireless terminal 1604
Temporarily stop sending addressed data.

In addition, when the partner terminal with which the wireless terminal 1604 is communicating is, for example, the wireless terminal 1603, data transmitted to the wireless terminal 1604 is similarly transmitted by transmitting a packet whose window size field is 0 to the gateway device 901. Transmission is temporarily stopped.

As a result of the above, there is no congestion in the network, but communication is not possible. For example, during handoff operation, data transmission is temporarily stopped at the TCP layer of the partner terminal communicating with the wireless terminal. In addition, it is possible to stop the decrease in the congestion window for controlling the transmission rate to the wireless terminal in this connection, and it is possible to immediately start data transmission at a high transmission rate after the handoff is completed.

Similarly, the TCP handoff control unit of the wireless terminal 1604 that has started the handoff operation transmits a signal indicating that the handoff is started to the packet generation unit 755 of the wireless TCP layer 750.
Send to. At this time, in the packet generation unit 755, the window size field is 0.
The wireless terminal 16 does not contain data, and the destination address and connection identification port number
04 address (IP address) and the port, source address, and connection identification port number of the currently communicating connection include the address (IP address) and port of the wired terminal 1001 communicating with the wireless terminal. Generate the set packet.

The packet generation unit 755 transmits the generated packet to the wireless TCP input unit 751.

Upon receiving this packet, the wireless TCP input unit 751 interprets that the receiving buffer of the partner wired terminal 1001 has no free space when receiving a packet notifying that the window size is 0. Temporarily stop sending

The TCP handoff control unit 760 of the wireless terminal 1604 receives a signal indicating that the handoff is completed from the wireless IF unit 300 or communicates with the wireless terminal 1604 from the IP input unit 501 or the wireless TCP input unit 751. A signal indicating that a packet has been received from the wired terminal 1001 is received, or the partner terminal 1001 is received from the TCP control unit 761.
When the signal indicating that the connection with the terminal is disconnected is received, a signal indicating that the generation of the window size 0 packet described above is stopped is transmitted to the packet generation unit 755. The packet generation unit 755 generates this packet, for example, every second and transmits it to the wireless TCP input unit 751 until it receives a signal indicating that generation of the window size 0 packet is to be stopped.

As described above, while there is no congestion in the network, communication is not possible. For example, during the handoff operation, the transmission of data is temporarily stopped in the TCP layer of the wireless terminal, and the wireless communication in this connection is performed. It is possible to stop the decrease in the congestion window that controls the transmission rate from the terminal side, and data transmission at a high transmission rate can be started immediately after the handoff is completed.

Next, the operation when the wireless terminal moves out of the wireless service area of the base station accommodated in the gateway device during communication by dividing and setting the connection with the wired terminal via the base station and the gateway device is shown in FIG. This will be described with reference to FIG. FIG. 26 shows a configuration of a gateway apparatus according to an embodiment of the present invention, and shows a part of the configuration of FIG.
The same parts as those in FIG. 1 are denoted by the same reference numerals, and different parts will be described here. Assume that the gateway devices 901 to 903 in FIG. 2 have the configuration shown by the gateway device 980 in FIG.

When the TCP handoff control unit 640 of the gateway device 902 receives a signal indicating that the wireless transmission path between the wireless terminal 1604 and the base station 1405 communicating with the gateway device 902 has been disconnected, for example, from the base station 1405, the gateway When a packet is received from the wireless terminal 1604 to the gateway devices 901 and 903 that accommodate base stations that serve areas adjacent to the boundaries of the radio service areas 1504 to 1506 of the base station accommodated by the device 902 27 including the identifier (for example, IP address) of the wireless terminal 1604 and the identifier (for example, IP address) of the own gateway device 902 requesting to be transferred.

The gateway devices 901 and 903 that have received this packet record the address of the wireless terminal 1604 included in this packet and the address of the gateway device 902 requesting the transfer in the transfer request table as shown in FIG.

When the gateway device 901 or 903 to which the wireless terminal 1604 has moved receives a packet from the wired IF unit connected to the wireless IF unit or the router 1301 in which the base station is accommodated, the gateway device 901 or 903 With reference to the transfer request table 491, when the source address of the received packet is the address of the wireless terminal 1604 registered in the transfer request table 491, the packet is transferred to the gateway device 902 registered as the transfer destination address. To do. Further, for each entry in the transfer request table 491, a timer is set in the transfer table timer 492 (the timer number corresponding to the timer No. item in the transfer request table 491 is described), and a fixed time. If the timer expires after elapses, the item subject to the timer is deleted.

If the gateway device 980 shown in FIG. 26 does not have the packet transfer function in the gateway device 903 in FIG. 2, the packet is sent to the base stations 1407 and 1408, and if the gateway device 901 does not have the packet transfer function, the packet is sent to the router 1301. A configuration having a function of performing transfer may be used. In that case, the gateway device 902 transmits a transfer request packet as shown in FIG. 27 to the base stations 1407 and 1408 or the router 1301 according to the procedure described above.

As described above, even when a wireless terminal moves to a service area of a base station accommodated by a different gateway device during communication, a packet can be transferred from the gateway device or base station accommodating the base station. The handoff between devices can be performed smoothly and the connection is not disconnected.

The figure which shows the structure of the gateway apparatus which is one Embodiment of this invention. The figure which shows the structural example of the 1st communication network containing the gateway apparatus of FIG. The figure which shows the structure of the radio | wireless terminal which is one Embodiment of this invention. The figure which shows a mode that the IP datagram was divided | segmented into the some data link frame in the communication network of one Embodiment of this invention. The figure which shows the case where TCP pure ack is interposing between several data link frames which comprise IP datagram in the communication network of one Embodiment of this invention. The figure which shows the relay method table in the gateway apparatus of one Embodiment of this invention. The figure which shows the relay method table in the gateway apparatus of one Embodiment of this invention. The figure which shows the structure of the radio | wireless terminal which is one Embodiment of this invention. The figure which shows the structure of the base station which is one Embodiment of this invention. The figure which shows the radio | wireless terminal address registration table in the base station of one Embodiment of this invention. The figure which shows the structural example of the 2nd communication network which is the 2nd Embodiment of this invention. The figure which shows operation | movement of the gateway apparatus of one Embodiment of this invention. The figure which shows the structure of the 3rd communication network which is the 3rd Embodiment of this invention. The figure which shows the structure of the router of one Embodiment of this invention. The figure which shows operation | movement of the gateway apparatus of one Embodiment of this invention. The figure which shows the structure of the 4th network which is the 4th Embodiment of this invention. The figure which shows the structure of the gateway apparatus which can be duplexed which is one Embodiment of this invention. The figure which shows the message path | route between the duplexed gateway apparatus which is one Embodiment of this invention, and a radio | wireless and a wired terminal. The figure which shows the structure of the gateway apparatus which is one Embodiment of this invention. The figure which shows the structure of the base station which is one Embodiment of this invention. The figure which shows the structure of the gateway apparatus which is one Embodiment of this invention. The figure which shows the structure of the gateway apparatus which is one Embodiment of this invention. The figure which shows the structure of the radio | wireless terminal which is one Embodiment of this invention. The figure which shows the structure of the gateway apparatus which is one Embodiment of this invention. The figure which shows the structure of the radio | wireless terminal which is one Embodiment of this invention. The figure which shows the structure of the gateway apparatus which is one Embodiment of this invention. The figure which shows the structure of the packet of the transfer request which the gateway apparatus which is one Embodiment of this invention transmits. The figure which shows the structure of the transfer request table in the gateway apparatus which is one Embodiment of this invention. The figure which shows the IP header with an option by a prior art. The figure which shows the TCP state transition diagram by a prior art.

Explanation of symbols

100 …… Wired IF unit 101 …… Wired IF input unit 102 …… Wired IF output unit 110 …… Wired IF unit 111 …… Wired IF input unit 112 …… Wired IF output unit 113 …… Broadcast reception function 114 …… Broadcast transmission function 120 …… Wired IF unit 121 …… Wired IF input unit 122 …… Wired IF output unit 150 …… Wired IF unit 151 …… Wired IF input unit 152 …… Wired IF output unit 180 …… Wired IF unit 181 …… Wired IF input unit 182 …… Wired IF output unit 190 …… Wired IF unit 191 …… Wired IF input unit 192 …… Wired IF output unit 200 …… Wireless IF unit 201 …… Wireless IF input unit 202 …… Wireless IF output unit 203 …… IP datagram reconstructing unit 210 …… Wireless IF unit 212 …… Wireless IF output unit 220 …… Wireless IF unit 221 …… Wireless IF input unit 222 …… Wireless IF output unit 223 …… IP datagram reconstruction unit 280 …… Wireless IF unit 281 …… Wireless IF input unit 282 …… Wireless IF output unit 290 …… Wireless IF unit 291 …… Wireless IF input unit 292… ... Wireless IF output section 295 ... Data link section 296 ... Handoff control section 300 ... Wireless IF section 301 ... Wireless IF input section 302 ... Wireless IF output section 303 ... IP datagram dividing section 304 ... Priority Control unit 310 ... Wireless IF unit 311 ... Wireless IF input unit 312 ... Wireless IF output unit 320 ... Wireless IF unit 321 ... Wireless IF input unit 322 ... Wireless IF output unit 323 ... IP datagram dividing unit 324 …… Priority control unit 330 …… Wireless IF unit 331 …… Wireless IF input unit 332 …… Wireless IF output unit 333 …… IP datagram division 334... Priority control unit 400... IP layer 401... IP input unit 402... IP output unit 403... IP relay unit 404 ....... Movement control unit 405. IP input unit 412 ... IP output unit 413 ... IP relay unit 415 ... Datagram filter 420 ... IP layer 421 ... IP input unit 422 ... IP output unit 423 ... IP relay unit 425 ... Datagram filter 426 …… Radio communication state reception processing unit 480 …… IP layer 481 …… IP input unit 482 …… IP output unit 483 …… IP relay unit 484 …… movement control unit 485 …… datagram filter 486 …… correspondence table 490 Transfer control unit 491 Transfer request table 492 Transfer table timer 500 IP layer 501 IP input unit 502 …… IP output unit 510 …… IP layer 511 …… IP input unit 512 …… IP output unit 550 …… IP layer 551 …… IP input unit 552 …… IP output unit 600 …… Wireless TCP layer 601 …… Wireless TCP input unit 602... Wireless TCP output unit 603... Segment filter 610... TCP relay unit 611... Wireless → wired relay unit 612 .. Wired to wireless relay unit 620... TCP layer 621. ... TCP output part 623 ... Segment filter 630 ... Wireless TCP layer 631 ... Wireless TCP input part 632 ... Wireless TCP output part 633 ... Segment filter 634 ... Wireless communication state adaptive control part 640 ... TCP handoff control part 641 ... TCP control unit 642 ... Packet generation unit 650 ... Wireless TCP layer 651 ... Wireless T CP input unit 652 ... Wireless TCP output unit 653 ... Segment filter 660 ... TCP relay unit 661 ... Wireless to wired relay unit 662 ... Wired to wireless relay unit 670 ... TCP layer 671 ... TCP input unit 672 ... ... TCP output part 673 ... Segment filter 680 ... TCP relay part 681 ... Wireless to wired relay part 682 ... Wired to wireless relay part 683 ... Option table 685 ... Wireless TCP layer 686 ... Wireless TCP input part 687 ... Wireless TCP output unit 688 ... Segment filter 689 ... Wireless TCP state transition variable 690 ... TCP layer 691 ... TCP input unit 692 ... TCP output unit 693 ... Segment filter 694 ... TCP state transition variable 695 ... ... TCP layer 696 ... TCP input part 697 ... TCP output part 69 …… Segment filter 699 …… Packet generation unit 700 …… Wireless TCP layer 701 …… Wireless TCP input unit 702 …… Wireless TCP output unit 710 …… TCP layer 711 …… TCP input unit 712 …… TCP output unit 720 …… TCP selection unit 730 ... wireless TCP layer 731 ... wireless TCP input unit 732 ... wireless TCP output unit 734 ... wireless TCP state transition variable 740 ... TCP handoff control unit 741 ... handoff disconnection variable 750 ... Wireless TCP layer 751 …… Wireless TCP input unit 752 …… Wireless TCP output unit 755 …… Packet generation unit 760 …… TCP handoff control unit 761 …… TCP control unit 800 …… Application 810 …… Application relay server 811 …… Cache 820 Application Relay server 821 …… Cache 850 …… Wireless compatible application 860 …… Application 900 …… Gateway device 901-903 …… Gateway device 911-912 …… Gateway device 921-923 …… Gateway device 930 …… Gateway device 931-933 …… Gateway device 944 …… Primary gateway device 945 …… Secondary gateway device 950 …… Gateway device 960 …… Gateway device 970 …… Gateway device 980 …… Gateway device 1001 to 1003 …… Wired terminal 1011 to 1013 …… Wired Terminal 1101 …… Wired network 1111 …… Wired network 1301 …… Router 1302-1305 …… Router 1311 …… Router 1312 …… Router 1400 …… Base station 1401-1 08 ... Base station 1411-1418 ... Base station 1421-1426 ... Base station 1501-1508 ... Wireless service area 1511-1518 ... Wireless service area 1521-1526 ... Wireless service area 1600 ... Wireless terminal 1601 1605: Wireless terminal 1610: Wireless terminal 1611-1614 ... Wireless terminal 1620 ... Wireless terminal 1621-1624 ... Wireless terminal 1630 ... Wireless terminal 1700 ... Control unit 1701 ... Electric field strength change notification unit 1702 ... BER change notification unit 1703... Terminal movement control unit 1750... Control unit 1751 .. field strength change notification unit 1752... BER change notification unit 1753... Terminal movement control unit 1754 ... correspondence table 1800. ... Receiver 1802 ... Transmitter 1803 ... Equipment 1804 …… Field strength measurement unit 1805 …… Aerial 1806 ... BER measurement unit 1850 …… Wireless transmission / reception unit 1851 …… Receiver 1852 …… Transmitter 1853 …… Shared device 1854 …… Field strength measurement unit 1855 …… Antenna 1856 ... BER measurement unit 1857 ... Wireless terminal address registration table 1900 ... Duplex control unit 1901 ... Judgment unit 1902 ... Switching control unit

Claims (4)

In a gateway device that relays and connects a wireless network and a wired network,
Transport layer protocol processing means for processing a transport layer protocol that interprets the loss of the transport layer protocol data unit as congestion and performs congestion avoidance processing;
The transport layer connection between the connection terminals of the wireless network is set by dividing the first connection and the second connection of the transport layer protocol for communication with the wireless network, or the connection of the wireless network The transport layer connection between the terminal and the connection terminal of the wired network is the first connection of the transport layer protocol for communication with the wireless network and the transport layer protocol for communication with the wired network. A connection division setting means for dividing and setting two connections,
A radio that performs the handoff when the wireless terminal receives a handoff start signal indicating that a handoff operation starts from a radio service area that the first base station serves to another radio service area that the second base station serves. Due to the loss of the transport layer protocol data unit during the handoff operation by transmitting a transport layer protocol data unit including a signal for performing flow control so as to suppress packet transmission to the terminal communicating with the terminal. A gateway device characterized by suppressing congestion avoidance processing .   In a gateway device that relays and connects a wireless network and a wired network,
  Transport layer protocol processing means for processing a transport layer protocol that interprets the loss of the transport layer protocol data unit as congestion and performs congestion avoidance processing;
  A transport layer connection between connection terminals of the wireless network is divided and set into a first connection and a second connection of a transport layer protocol for communication with the wireless network, or the connection of the wireless network The transport layer connection between the terminal and the connection terminal of the wired network is the first connection of the transport layer protocol for communication with the wireless network and the transport layer protocol for communication with the wired network. A connection division setting means for dividing and setting two connections,
  A radio that performs the handoff when the wireless terminal receives a handoff start signal indicating that a handoff operation starts from a radio service area that the first base station serves to another radio service area that the second base station serves. By transmitting a transport layer protocol data unit for temporarily stopping packet transmission to the terminal communicating with the terminal, the congestion window is reduced due to the loss of the transport layer protocol data unit during the handoff operation. The gateway apparatus characterized by suppressing. In a wireless terminal device that communicates with a wireless network connection terminal or a wired network connection terminal via a base station,
Transport layer protocol processing means for processing a transport layer protocol that interprets the loss of the transport layer protocol data unit as congestion and performs congestion avoidance processing ;
Transmission suppression means for transmitting a signal for suppressing packet transmission to the transport layer protocol processing means;
Handoff notification means for notifying the transmission control means when detecting the start and end of a handoff operation between base stations,
When the start of the handoff operation is notified to the transmission control unit, and starts transmission of the transport layer protocol data unit that includes a suppress signal the packet transmission,
The signal that suppresses the packet transmission is a signal that performs flow control so as to suppress the packet transmission with respect to the signal that receives the signal that suppresses the packet transmission.
A radio terminal apparatus, which terminates transmission of a transport layer protocol data unit including a signal for suppressing transmission of the packet when the transmission control means is notified of completion of a handoff operation.   A wireless terminal device that communicates with a wireless network connection terminal or a wired network connection terminal via a base station
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  Transport layer protocol processing means for processing a transport layer protocol that interprets the loss of the transport layer protocol data unit as congestion and performs congestion avoidance processing;
  Transmission suppression means for transmitting a signal for suppressing packet transmission to the transport layer protocol processing means;
  Handoff notification means for notifying the transmission control means when detecting the start and end of a handoff operation between base stations,
  When the transmission control means is notified of the start of the handoff operation, the transmission of the transport layer protocol data unit including the signal for suppressing the packet transmission is started,
  The signal for suppressing the packet transmission is a signal for temporarily stopping the packet transmission for the one that receives the signal for suppressing the packet transmission,
  A wireless terminal device, which terminates transmission of the transport layer protocol data unit including a signal for suppressing transmission of the packet when the transmission control means is notified of completion of a handoff operation.

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