CN105141588A - Management of seamless handover between different communication systems in IP (Internet Protocol) dual-mode terminal - Google Patents

Abstract

A dual-mode terminal designed to be connected to an IP-based network through a first communication system and a second communication system, the dual-mode terminal includes a first physical network interface module, and establishes a packet-based network with the IP-based network through the first communication system communication, the first physical network interface module with the first physical network address can access the first physical network interface module; the second physical network interface module establishes packet-based communication with the IP-based network through the second communication system, and has The second physical network interface of the second physical network address can access the second physical network interface module; the protocol stack based on IP works between the software application in the dual-mode terminal and these physical network interface modules; A system for performing seamless handover between first and second communication systems during an IP network, wherein the system includes a virtual network physical network interface module accessed through a virtual network interface having a virtual network address.

Description

Management of seamless handover between different communication systems in IP dual-mode terminal

This application is filed on October 31, 2006, the application number is 200680056674.7 (the international application number is PCT/EP2006/010468), and the invention name is "Management of seamless switching between different communication systems in IP dual-mode terminals." "A divisional application of the invention patent application.

technical field

The present invention relates to communication systems, and more particularly to the management of seamless handover between different communication systems in IP dual-mode terminals, ie dual-mode terminals providing connectivity to the Internet by means of different communication technologies.

Background technique

A known dual-mode mobile communication device is a device for connecting different wireless communication networks, in particular cellular and non-cellular radio communication networks, for voice and data communication. For example, third-generation (3G) dual-mode mobile communication devices can provide connectivity to the Internet through UMTS/W-CDMA cellular radio communication networks, and eg WLAN (Wi-Fi) radio communication networks based on IEEE802.11 specifications. Availability of dual-mode mobile communication devices providing cellular (2G/3G) and WLAN connectivity, coupled with global deployment of WLAN hotspots has improved the integration (interoperability) of WLAN communication systems with 2.5G and 3G cellular communication systems Interest in possible solutions for dual-mode mobile communication devices to provide the ability to use multiple radio access networks (multi-access capability), and the quality of service perceived by the end user when switching between different communication networks ( QoS) has negligible impact on the capability (vertical handover).

Depending on the level of integration required between different networks, several approaches can be considered to combine different Radio Access Technologies (RATs). When the integration between different RATs is tighter, service provisioning is more efficient and the selection of the RAT that can provide the best radio access conditions is faster and simpler. Another advantage of tight RAT integration is the shortened time required for vertical handover between two different communication networks with less impact on end-user perceived QoS. On the other hand, a high level of integration between two different communication networks requires more work to define the interfaces and mechanisms that allow the necessary data exchange and signaling between different RATs. In this case, the integration takes place at the L2/L3 layer of the ISO-OSI protocol stack, as proposed in the Unlicensed Mobile Access (UMA) standard.

Even if there is no real integration between RATs, vertical handover is possible due to the coexistence of network access technologies according to Internet Protocol (IP). However, if countermeasures are not taken, problems can arise when users switch between different network access technologies and/or network access providers: because IP addresses are assigned to fixed locations in the network, when the network location (connection new IP addresses should be assigned when the input technology and/or provider changes. This makes transparent mobile access to the Internet impossible, causing IP applications to be restarted, with consequent loss of current sessions. Furthermore, if the Transmission Control Protocol (TCP) is used in addition to IP, as in most IP links, the connection is also composed of a digital quaternion containing indications about the IP addresses and port numbers in the source and destination hosts group designation. If one of these four numbers is changed, it will cause the interruption of the TCP/IP connection.

In order to solve these problems, different technologies have been proposed, which can be divided according to the layer of the ISO-OSI protocol stack where the solution is provided, specifically, can be divided to provide solutions at the network layer (such as the IP layer). solutions, technologies that provide solutions at the transport layer (eg, TCP/UDP (User Datagram Protocol)), and technologies that provide solutions at higher layers (eg, socket or application layer).

The so-called Mobile IP represents a solution to solve the problem of end-to-end host mobility at the network layer. Mobile IP is an open standard defined by the Internet Engineering Task Force (IETF) RFC2002. It is not only a part of the IPv4 standard, but also a Part of the IPv6 standard, it allows users to maintain the same IP address, remain connected, and maintain ongoing applications when roaming between IP networks. Mobile IP provides users with ubiquitous connectivity and is scalable to the Internet because it is IP-based.

In more detail, Mobile IP attempts to solve the host mobility problem at the network layer by using some degree of indirect or triangular routing of all packets from the corresponding host to the mobile node.

This indirect routing is achieved through the use of "Home Agents" and "Foreign Agents", which are agents that provide services to mobile nodes. Although Mobile IP solves the host mobility and reachability problem well, it does not solve the transport connection failure (eg, any change of transport endpoint will cause the session to fail). Typically, applications that depend on transport session connectivity need to be restarted and new transport connections have to be established. Other disadvantages of Mobile IP include sub-optimal triangular routing and heavy use of IP tunneling. Service providers generally do not allow tunneling of packets for security reasons. Furthermore, due to the increased frequency of denial of service (DOS) attacks, service providers perform ingress filtering on incoming packets to ensure that incoming packets are indeed from the network they claim to originate from, and to block those packets with bogus source addresses. Although the ingress filtering problem can also be solved with reverse tunneling, reverse tunneling results in further sub-optimal use of network resources and adds additional packet delay between the two endpoints.

Solutions that attempt to solve the end-to-end host mobility problem at the transport layer or higher usually either split the connection into segments, modify the standard TCP implementation by adding new messages and states to the TCP state machine, or when attempting to re-establish the connection, Trick the application into believing the connection still exists.

For example, one solution that works at the transport layer level is the so-called Mobile Sockets (MSOCKS), which uses a segmented connection broker for connection redirection. MSOCKS inserts a proxy in the communication path between the mobile node and its corresponding host, and uses the TCP bonding mechanism to divide the connection into multiple segments, and thus conceals the mobility problem of the mobile node from the corresponding host. However, adding agents to the communication path can significantly degrade the service.

Other transport layer level techniques introduce a library between the application and the socket application programming interface (API) that maintains the illusion of a single, complete connection in the case of continuous connections. All of these methods require linking applications with their respective (proprietary) libraries. The illusion of a full connection is obtained by tricking the application into believing that the transport session is still valid (even if the transport session is closed). The intermediate library then attempts to re-establish the (new) transport connection and map the new transport connection to the application using the transport connection. The implementation of such a solution, and the operational difficulties involved, include virtualizing mechanisms such as I/O polling, asynchronous and non-blocking I/O processes, the need for timers and signal handlers, and the need for ", "kill" and "exec" the need for additional process control interfaces.

A solution that works at the application layer level uses the Session Initiation Protocol (SIP). In this case, if during a session a terminal needs to change its IP address, the terminal can inform its corresponding host by sending a new INVITE message specifying the new IP address and updated session parameters. Because it is at the application layer, SIP relies on protocols and mechanisms in the lower layers to handle physical network connections. Thus, additional procedures are required in order to monitor the radio link layer quality, and to connect the terminal to a new wireless network (and thus obtain a new IP address) before sending the SIPre-INVITE message. Furthermore, this mechanism is only applicable to applications that rely on SIP to manage sessions, and applications designed to support this IP change process.

Another solution provides a mechanism for end-to-end host mobility by modifying the transport layer protocol and end application programs. This modification adds new states and semantics to the TCP finite state machine, and defines new TCP options to negotiate connection transitions. Other techniques either involve changing the TCP header, packet format, protocol semantics, or adding extra headers to the packet. However, a disadvantage of these techniques is that in order to take advantage of a new feature, the end user application must be aware of the new feature, implying that existing applications are required to be changed.

WO02/43348 discloses a method of switching between heterogeneous communication networks, in particular a method of maintaining communication between a first mobile unit and a second unit, wherein the first unit communicates via the first communication network and the second unit Communicate over a second communication network. The first unit includes a first protocol stack, and the second unit includes a second protocol stack. The first unit comprises a first session layer adapted to operate within the first unit, functioning as an interface between the first protocol stack and the first software component. Similarly, the second unit includes a second session layer adapted to operate within the second unit, acting as an interface between the second protocol stack and the second software component. The first unit includes one or more first communication hardware associated with driver routines suitable for different communication networks. When the first unit switches from the first communication network to the third communication network, the first session layer maintains communication by selecting the first communication hardware and driver routines required by the third communication network. The respective identities of the first unit and the second unit are maintained by the first and second session layers, these identities being preserved during switching of the communication network by the first unit.

WO2005/076651 discloses a method and system for seamless handover of a mobile device in a heterogeneous network. Mobile devices move between different topological network locations and transmit and/or receive data via different network access technologies without any communication between the client IP application running on the mobile device and the interrupted server IP application Data transmission, wherein the client IP application of the mobile device sends a request to the client service module using the first data unit, wherein the client service module creates a second data unit based on the received first data unit, and sends the request to the client service module using the second data unit The server service module sends a request, wherein the server service module creates a third data unit according to the received second data unit, and uses the third data unit to send a request to the server IP application, thereby processing the client IP application and the server IP application data exchange between them.

In US2005/0198384 is disclosed a solution that works at the level of the socket layer and involves address changes of endpoints in packet networks, where the Seamless Transport Endpoint Mobility (STEM) architecture transfers the transport connection endpoints from the old IP Addresses are migrated to new IP addresses without losing sessions. The migration process is negotiated between the two endpoints themselves. Transport endpoint mobility consists of communication between two STEM daemons (daemons), one in each endpoint, each of which dynamically updates kernel data structures associated with the session (e.g., with Elements of the TCP/IP application-related 5-tuple). Migration is transparent to applications that use the underlying transport connection for data transfer.

WO02/103978 discloses a mobile IP method in a heterogeneous network, wherein the interface management module of the mobile node checks the mobile node of the available physical network interface, uses the available and configurable physical network interface to draw up a look-up table, and compares itself with the available Link to one of the physical network interfaces. The IP application program of the mobile node accesses the heterogeneous network through the virtual IP network interface generated in the mobile node, and the permanent virtual IP network interface is connected with the current network through the interface management module. During the change process of the physical network interface of the mobile node, according to the look-up table, the link between the permanent virtual IP network interface and the network is updated by means of the interface management module. In particular, the invention relates to a method for mobile nodes with real-time applications in heterogeneous networks.

WO03/065654 discloses an Internet Protocol-based wireless communication scheme that allows mobile devices such as personal digital assistants or mobile phones to communicate with the Internet or another based IP network connection. A wireless network driver software structure called the Multistandard Wireless Adaptation Layer (MWAL) is proposed for client devices MT that are portable and need to switch efficiently from one wireless standard to another , and must be able to remain connected and reachable on the Internet and other IP-based networks even when switching between wireless communication standards. This technology is a Layer 2 technology suitable for vertical markets and proprietary solutions, where MWAL enables client device MTs to switch vertically between wireless communication standards.

Contents of the invention

The applicant notes that despite all the above solutions, there remains a need for a method that allows the management of A solution for switching between different network access technologies.

This need is at least partially fulfilled by the present invention in that it relates to a dual mode terminal designed to enable seamless handover between different communication systems in the dual mode terminal as defined in the appended claims. The present invention also relates to an IP single-mode terminal communicating with said dual-mode terminal and supporting seamless handover in the dual-mode terminal as defined in the appended claims, and achieving seamlessness between different communication systems in the dual-mode terminal Switched systems and software products.

In particular, the present invention fulfills the above needs by introducing into the operating system of a dual-mode terminal a network sublayer comprising a virtual network interface, a type capable of handling incoming and outgoing data packets and residing in A software application in and running on a physical device, hereinafter referred to as a physical network interface module. The physical network interface module is responsible for transmitting and receiving data packets, and acts as the host of the network interface driver. The operating system of the network interface driver provides the service of the physical network interface module and hides the actual transmission mechanism used by the physical network interface module from the operating system.

In a preferred embodiment, the dual-mode terminal comprises two physical network interface modules, which provide data packets via two different access technologies, specifically two different radio access technologies transmission and reception. The operating system of the dual-mode terminal can access the first physical network interface module through the first physical network interface with the first IP address, and can access the second physical network interface through the second physical network interface with the second IP address. In addition to these two physical network interface modules, a virtual network interface module is provided in the dual-mode terminal, said virtual network interface module consisting of appropriate modules of the kernel of the operating system of the dual-mode terminal. The virtual network interface module is accessible through the virtual network interface with the virtual IP address and receives and transmits incoming and outgoing data packets through the physical network interface module depending on which physical network interface module is in the best propagation condition.

In addition, by an appropriate module of the kernel of the remote terminal's operating system, another virtual network interface module is provided in the remote terminal accessible through a virtual network interface with its own virtual IP address, which dispatches to/from A data packet comprising a physical network interface in a remote terminal and having its own IP address. A routing table in the dual-mode terminal and a routing table in the remote terminal are maintained to route data packets destined for the virtual IP address to the virtual network interfaces of the dual-mode terminal and the remote terminal. When an application in the dual-mode terminal opens a connection with an application in the remote terminal, the dual-mode terminal will send a data packet from its virtual IP address to the virtual IP address of the remote terminal. Specifically, the data packets are routed to the virtual network interface module in the dual-mode terminal, and the virtual network interface module changes the IP address associated with the data packet in such a way that the target IP address is changed to the physical network in the remote terminal The IP address of the interface, and the source IP address is changed to the IP address of the physical network interface in the dual-mode terminal for data transmission, that is, the first IP address (if the first physical network interface is used), or the second IP address (if the second physical network interface is used). The data packets are then routed over the Internet to a physical network interface module in the remote terminal, where it is received. The physical network interface module in the remote terminal is configured such that when a data packet is received with a source IP address equal to one of the IP addresses of the physical network interfaces in the dual-mode terminal, the data packet is passed to the virtual network interface in the remote terminal module. The virtual network interface module changes the IP address associated with the data packet in such a way that the source IP address changes from the IP address of the physical network interface of the physical network interface module in the dual-mode terminal to the IP address of the virtual network interface in the dual-mode terminal. The virtual IP address, and the target IP address is changed from the IP address of the physical network interface of the physical network interface module in the remote terminal to the virtual IP address of the virtual network interface of the virtual network interface module in the remote terminal. The data packets are then passed by the virtual network interface module to the application program that received them. The same steps are followed when the remote terminal answers, sending an IP data packet from the remote terminal's virtual network interface to the virtual network interface in the dual-mode terminal.

In order to implement the steps explained above, before starting the IP connection, the dual-mode terminal and the remote terminal must exchange information related to their physical and virtual IP addresses, and if the dual-mode terminal decides to change the physical network interface module, it shall notify the remote terminal that the IP data packet will be received by the new IP address of the new physical network interface module, rather than the previous IP address. The exchange of said information is managed by signaling software applications running in the dual mode terminal and the remote terminal respectively.

Description of drawings

In order to understand the present invention better, preferred embodiment is described below with reference to accompanying drawing, and preferred embodiment is only as example, rather than limitation of the present invention, wherein:

1 shows a block diagram of a dual-mode terminal and a remote terminal configured to seamlessly switch between different communication systems in the dual-mode terminal according to a preferred embodiment of the present invention; and

Figure 2 represents messages exchanged between a dual-mode terminal and a remote terminal during an IP session.

Detailed ways

The following description is provided to enable any person skilled in the art to make and use the invention. Various modifications to the embodiments will be readily apparent to those skilled in the art, and the general principles herein can be applied to other embodiments and applications without departing from the scope of the present invention. Thus, the present invention is not intended to be limited to the embodiments shown, but is to be accorded the widest scope consistent with the principles and features disclosed herein and defined in the following description and appended claims.

Fig. 1 represents a dual-mode mobile terminal T1 and a remote terminal T1 configured to communicate through an IP-based network such as the Internet, and to realize and support seamless switching between different communication systems in the dual-mode terminal, according to a preferred embodiment of the present invention. Block diagram of mobile terminal T2.

Each of the dual-mode terminal T1 and the remote terminal T2 is provided with an operating system, the operating system has a kernel space responsible for terminal resource allocation and management, and a user space responsible for user software application execution management. In particular, the kernel space provides individual software applications with secure access to the terminal's hardware resources and manages (when and how long) each software application uses the terminal's hardware resources.

In particular, the dual-mode terminal T1 includes in the kernel space:

A first physical network interface module N11, in a preferred embodiment a Universal Mobile Telecommunications System (UMTS) module, accessible through a first physical network interface ph11 with a first IP address IP1_P1 and adapted to communicate via a first wireless The network (UMTS in this embodiment) receives and transmits incoming and outgoing TCP/IP data packets;

A second physical network interface module N12, in a preferred embodiment a wireless local area network (WLAN) modem, accessible through a second physical network interface ph12 having a second IP address IP1_P2, and adapted to communicate via a second wireless communication network ( In this embodiment a WLAN) receives and transmits incoming and outgoing TCP/IP data packets;

a Transmission Control Protocol/Internet Protocol (TCP/IP) stack adapted to operate between the user's software application and the first and second physical network interface modules N11, N12; and

The virtual network interface virt11 with the virtual IP address IP1_V1 provided by a module (hereinafter referred to as the virtual network interface module M1) of the kernel of the operating system is suitable for use in the TCP/IP protocol stack and the first and second physical network interface modules Operate between N11, N12 to receive and transmit incoming and outgoing TCP via the physical network interface ph11 or ph12 according to a predetermined resource management strategy, e.g. depending on which of the physical network interface modules N11 or N12 has the best propagation conditions /IP data packets.

In other embodiments, the physical network interface module may be adapted to conform to a communication system other than UMTS or WLAN, for example according to one or more of: GSM, CDMA2000, WiMAX, Bluetooth, or any other suitable wireless communication system, Or a less preferred wired communication system, communicating with an IP-based network.

Similarly, remote terminal T2 (in the example shown in Figure 1 is a single-mode terminal) includes in kernel space:

• A physical network interface module N21 accessible through the physical network interface ph21 with IP address IP2_P1 and adapted to receive and transmit incoming and outgoing data packets over the wireless communication network. In a preferred embodiment, the physical network interface module N21 may be a UMTS module connected to a UMTS communication network. In a different embodiment, the remote terminal T2 may be a server or a terminal connected to a local area network (LAN). In the latter case, the physical network interface module N21 may be an Ethernet card connected to a local area network (LAN);

· A TCP/IP protocol stack adapted to operate between the user's software application and the physical network interface module N21; and

A virtual network interface virt21 with virtual IP address IP2_V1 and provided by a module of the kernel of the operating system (hereinafter referred to as virtual network interface module M2), suitable for operating between the TCP/IP protocol stack PS and the physical network interface module N21 , thereby receiving and transmitting incoming and outgoing TCP/IP data packets through the physical network interface ph21.

On the other hand, the remote terminal T2 may itself be a dual-mode terminal capable of communicating with an IP-based network through two different physical network interface modules (eg, similar to that described above for the dual-mode terminal T1).

In a preferred embodiment, each virtual IP address uniquely identifies a virtual network interface in the corresponding terminal. The virtual IP address can be statically or dynamically assigned to the virtual network interface through a connection with a remote server provided by the network operator, such as a DHCP (Dynamic Host Configuration Protocol) server. Once the terminal is connected to the Internet, a connection to a remote server can be established through one of the physical network interfaces ph11 or ph12.

The dual-mode terminal T1 and the remote terminal T2 respectively include in the user space:

· One or more users' software applications A1, A2; and

• A signaling software application, referred to below as a connection manager C1, C2.

In particular, the connection manager C1 of the dual-mode terminal T1 has the following tasks:

- managing the first and second physical network interfaces ph11 and ph12. Specifically, the connection manager C1 talks to the WLAN and UMTS physical network interfaces N11 and N12 to monitor their link quality. The decision as to which interface is to be used for data packet transmission and reception is based on reported received signal strength indicator (RSSI) values.

- Manage active peer-to-peer connections. Specifically, the connection manager C1 handles the connections to the remote terminal T2, and in general to all remote terminals that support IP session continuity, presenting to the remote terminal T2 the physical and virtual network interface ph11 of the dual-mode terminal T1 , ph12 and virt11 virtual and physical IP addresses IP1_P1 , IP1_P2 and IP1_V1 , and when a switch between physical network interfaces ph11 and ph12 occurs, the event is signaled. In a preferred embodiment, the switching between the physical network interfaces ph11 and ph12 is signaled to the remote terminal T2 via a TCP connection which is always kept on the UMTS network since this network is more reliable than the WLAN network.

More specifically, with respect to the first task, the connection manager C1 of the dual-mode terminal T1 talks to the UMTS and WLAN physical network interface modules N11 and N12 and periodically checks the status of these two connections in order to decide which physical network Interface modules will be used for data transmission. The algorithm used to select the best connection is configurable by the network operator. In a preferred embodiment, a connection to a WLAN is selected whenever a WLAN connection with an RSSI level above a certain threshold guaranteeing good QoS is available. If the RSSI of the WLAN network is below said threshold, the connection manager C1 checks the existence of the UMTS network and switches the virtual network interface virt11 of the dual-mode terminal T1 to the UMTS network. In another embodiment, a double threshold can be used: when the RSSI of the WLAN network is below the first threshold, the connection manager C1 checks for the presence of the UMTS network and starts sending short dummy data packets in order to "warm up" the connection . This is done to avoid additional delays introduced by the UMTS network during the establishment of the data connection. With these dummy data packet transmissions, the UMTS link will be fully available and responsive when a handover is required. If the RSSI of the WLAN continues to drop and is lower than the second threshold, link switching occurs.

Additional or alternative resource management strategies may be employed to select the connection to be used for data transmission (for example, when the transmission quality of both connections is good) in order to optimize, for example, the resources available on the two communication systems linked to the corresponding network interfaces. Use of radio resources.

For the second task, the connection manager C1 of the dual-mode terminal T1 exchanges signaling information with the connection manager C2 of the remote terminal T2. Figure 2 represents the exchange of messages between the connection managers C1 and C2 of the dual-mode terminal T1 and the remote terminal T2 during a communication session.

Whenever the application A1 running on the dual-mode terminal T1 requests to open a connection with a remote terminal supporting IP session continuity (in the example shown in FIG. The controller C2 sends an "open message" containing a request to open the connection. Assuming that the connection manager C1 determines that the first physical network interface ph11 provides the best connection, the open message is in the form of "Open(IP1_P1, IP1_V1)", which specifies the first physical network interface in the dual-mode terminal T1 that will be used for data packet transmission. The IP address of the network interface ph11, and the IP address of the virtual network interface virt11 in the dual-mode terminal T1. In this way, the remote terminal T2 is informed that the dual-mode terminal T1 wishes to start an IP session, and that the dual-mode terminal T1 uses a virtual network interface with IP address IP1_V1 which transmits data packets over a physical network interface with IP address IP_P1. The first message includes a signaling data packet, and the signaling data packet is sent on a more reliable link, such as a UMTS link, through a TCP channel (if the dual-mode terminal T1 is a 3g-WLAN dual-mode mobile phone), And it is received by the physical network interface module N21 of the remote terminal T2.

In a preferred embodiment, the driver of the physical network interface module N21 monitors all data packets received and passes them to a function called the vrit_change function below, which is provided by the module M2 of the kernel space of the operating system of the remote terminal T2 Derive and check if the received data packet is addressed to the TCP port of the remote terminal T2 where the connection manager C2 is waiting for a message. If this is the case, the virt_change function parses the message and extracts the information needed for module M2 to function correctly. With this solution, the module M2 reads the signaling information exchanged between the connection managers C1 and C2 and configures itself independently. The connection manager C2 replies to the dual-mode terminal T1 with an "Accept message" containing an acceptance report in the form "Accept(IP2_P1, IP2_V1)" in which the virtual network interface virt21 in the remote terminal T2 is specified The IP address IP2_V1 of the remote terminal T2 and the IP address IP2_P1 of the physical network interface ph21 in the remote terminal T2.

In another embodiment, the open request is received by the connection manager C2, which calls it via an appropriate method exposed by the virtual driver (e.g., an ioctl, see J. Corbet, A. Rubini, G. Kroah-Hartman eds. "LinuxDeviceDrivers", O'Reilly), configures module M2, and then replies with an acceptance message.

The accept message is received by the preferred physical network interface ph11 or ph12 of the dual-mode terminal T1, for example, the UMTS physical network interface ph11. In a preferred embodiment, the physical network interface driver monitors all data packets received and passes them to the virt_change function exported by the module M1 of the kernel space of the operating system of the dual-mode terminal T1, the virt_change function according to the received message information, configure itself to manage the real IP address and virtual IP address of the physical and virtual network interfaces ph21 and virt21 of the remote terminal T2, and the virt_change function will be used for data packet transmission and reception with the remote terminal T2.

Whenever the connection manager C1 determines that the physical network interface currently used for data packet transmission and reception is to change, it sends a "Switch message" containing a request to switch connections. Assuming that the connection manager C1 determines that the second physical network interface ph12 now provides the best connection, the switching message is in the form of "Switch(IP1_P2, IP1_V1)", which specifies the second physical network interface ph12 in the dual-mode terminal T1 that will be used for data packet transmission. The IP address of the network interface ph12, and the IP address of the virtual network interface virt11 in the dual-mode terminal T1.

The switching message is received by the remote terminal T2 and used by the module M2 to configure itself for correct address switching. The connection manager C2 then replies to the dual-mode terminal T1 with an "Accept message" containing an acceptance report in the form "Accept(IP2_P1, IP2_V1)", and the module M1 in the dual-mode terminal T1 uses this "Accept message" to complete the handover.

On the basis of a "close message" containing a request to switch the connection and in the form of "Close(IP1_V1)", the dual-mode terminal T1 is able to close the connection with the remote terminal T2. This message informs the module M2 in the remote terminal T2 that it should stop changing the IP address of messages sent to or received from the virtual IP address IP1_V1.

Finally, the remote terminal T2 replies with a corresponding "close message" containing a request to switch the connection and in the form "Close(IP2_V1)". This message informs the module M1 in the dual-mode terminal T1 that it can close the connection, stop changing the IP address of the data packets sent to or received from the virtual address IP2_V1 of the remote terminal T2.

The low-level processing of IP data packets sent and received by the two terminals T1 and T2 is carried by the terminals T1 and T2, and when loaded is configured to connect with the real physical device of the terminals T1 and T2 and monitor the correct TCP port on The signaling information for modules M1 and M2 is completed. Modules M1 and M2 activate the virtual network interface virt1 or virt2 associated with the virtual IP address and, in addition to the functionality necessary to implement IP address changes and physical network interface switching, provide one or more of the virtual network interface drivers necessary Typical functions (eg, init, open, stop, etc.). In particular, in a preferred embodiment, the core of these functions is provided by three functions referred to below as virt_change, virt_hw_tx and virt_header.

Specifically, virt_change is a function derived from modules M1 and M2 that is called from the physical network interface driver each time the physical network interface driver receives a data packet. To call this function, the driver of the physical network interface forwards the received data packet to the virt_change function before processing the received data packet. The virt_change function checks whether the data packet is a packet generated by the connection manager C1 or C2, and if this is the case, Then explain the commands exchanged between the two terminals T1 and T2 as before. In a preferred embodiment, the driver of the virtual network interface keeps track of every active peering connection managed by the connection manager C1 or C2 by means of a matrix called the VirtualVsReal matrix, which records the difference between the virtual IP address and the real IP address. right. The virt_change function reads the virtual IP address received in the accept message, and if the virtual IP does not exist in the matrix, it records the new virtual IP-real IP pair. If the virtual IP exists, but the real IP is different due to ongoing switching, then the driver of the virtual network interface records the new IP pairing in the matrix. The virt_change function is also responsible for changing the IP address in the received data packet. For each received IP data packet, the virtual network interface driver checks whether the source address is one of the real IP addresses registered in the matrix, if this is the case, it changes the source address to the corresponding virtual address, and changes the destination address from The real IP is changed to its own virtual IP address. After changing the IP address, the virtual network interface driver recalculates the TCP/UDP checksum, if necessary, so that the operating system does not discard processed data packets.

While packet processing on the receiver side is entirely managed by the virt_change function, the peering process on the transmitter side is handled by two functions: virt_hw_tx and virt_header. The function virt_hw_tx implements the handling of source and destination addresses, and the queuing of such modified packets in the correct physical network interface queues. This function controls the destination address in the virtual part of the VirtualVsReal matrix, if it finds a correspondence, then changes the destination address with the real address, and signals with the connection manager the IP address of the physical network interface for the currently used physical network interface to change the source address . After an IP address change, the UDP or TCP checksum is recalculated and the data packet is transmitted over the currently used physical network interface. A layer 2 header must be appended to a data packet before the data packet is transmitted. The format of the Layer 2 header depends on the physical network interface used. The virt_header function solves this problem by modifying the layer 2 header according to the physical network interface that should be used.

While the method and apparatus of the present invention have been illustrated with respect to presently preferred embodiments of the invention, it will be apparent that various modifications and substitutions may be made to the described embodiments and numerous other embodiments of the invention may be practiced without departure from the spirit and scope of the invention as defined in the following claims.

Claims (20)

1. A dual-mode terminal (T1) designed to be connected to an IP-based network via a first and a second communication system, said dual-mode terminal (T1) comprising: a first physical network interface module (N11), adapted to For establishing packet-based communication with an IP-based network via a first communication system, said first physical network interface module (N11) having an associated first physical network address (IP1_P1); a second physical network interface module (N12) , adapted to establish packet-based communication with an IP-based network via a second communication system, the second physical network interface module (N12) having an associated second physical network address (IP1_P2); the first IP-based protocol stack (TCP/IP) adapted to work between the software application (A1) and the first and second physical network interface modules (N11, N12) in said dual-mode terminal (T1); It is characterized by: The first IP-based protocol stack (TCP/IP) is configured to generate data packets having an IP address equal to a first virtual network address (IP1_V1) associated with the first virtual network interface module (M1) the source physical network address, and Wherein the dual-mode terminal (T1) further includes a system for performing seamless switching between the first and second communication systems, the system includes: - a first virtual network interface module (M1) with an associated first virtual network address (IP1_V1) configured to send data packets from the first IP-based protocol stack (TCP/IP) to the source physical network address changing to a physical network address (IP1_P1, IP1_P2) associated with said physical network interface module (N11, N12), and - a first connection management application (C1) configured to manage at least one of the first and second physical network addresses (IP1_P1, IP1_P2) and the first virtual network address (IP1_V1) to said dual-mode terminal (T1) Transmission of the communicating receiving terminal (T2). 2. The dual-mode terminal according to claim 1, wherein said first connection management application (C1) is further configured to manage first and second physical network interface modules (N11, N12), and said dual-mode A connection between a terminal (T1) and said IP-based network. 3. The dual-mode terminal according to claim 2, wherein the first connection management application (C1) is further configured to determine in the dual-mode terminal (T1), which of the first and second communication systems will be for connecting to said IP-based network, and performing a seamless handover between the first and second communication systems to maintain IP session continuity. 4. The dual-mode terminal according to claim 3, wherein said first connection management application (C1) is further configured to cooperate with the first and second physical network interface modules (N11, N12) to determine the Which of the first and second communication systems has the best propagation conditions for connection of said IP-based network. 5. The dual-mode terminal according to claim 4, wherein the first connection management application (C1) is further configured to determine which of the first and second communication systems has The optimal propagation conditions. 6. The dual-mode terminal according to claim 2, wherein the first connection management application (C1) is further configured to manage information related to the occurrence of switching between the first and second communication systems via the first and second communication systems One of the two communication systems and the IP-based network for transmission. 7. A single-mode terminal (T2) designed to establish packet-based communication over an IP-based network with a dual-mode terminal (T1 ) according to any preceding claim, said single-mode terminal (T2) comprising: Three physical network interface modules (N21) adapted to establish packet-based communications with an IP-based network via a third communication system, said third physical network interface module (N21) having an associated third physical network address (IP2_P1) ; a second IP-based protocol stack (TCP/IP) adapted to work between a software application (A2) in said single-mode terminal (T2) and said third physical network interface module (N21); It is characterized in that, The second IP-based protocol stack (TCP/IP) is configured to generate data packets having a second virtual network address (IP2_V1) equal to a second virtual network address (IP2_V1) associated with a second virtual network interface module (M2) a source physical network address, and a target physical network address equal to the first virtual network address (IP1_V1) of the first virtual network interface module (M1); and Said single-mode terminal further comprises: a system for maintaining IP session continuity during connection to said dual-mode terminal (T1) over an IP-based network, said system comprising: A second connection management application (C2) configured to receive at least one of the first and second physical network addresses (IP1_P1, IP1_P2) from the sending terminal (T1) with which the single-mode terminal (T2) communicates and the transmission of the first virtual network address (IP1_V1), and A second virtual network interface module (M2) with an associated second virtual network address (IP2_V1), configured to send data packets from said second IP-based protocol stack (TCP/IP) to the source physical network address changing to a third physical network address (IP2_P1) associated with a third physical network interface module (N21), and changing the target physical network address of data packets from said second IP-based protocol stack (TCP/IP) into physical network addresses (IP1_P1, IP1_P2) associated with the physical network interface modules (N11, N12) of the dual-mode terminal (T1) for data transmission. 8. The single-mode terminal according to claim 7, wherein the second virtual network interface module (M2) is also configured to change the source physical network address of the data packet received from the dual-mode terminal (T1) to be the same as the first virtual network address. The first virtual network address (IP1_V1) associated with the network interface module (M1), and the target physical network address of the data packet received from the dual-mode terminal (T1) is changed to be associated with the second virtual network interface module (M2) The second virtual network address (IP2_V1) of . 9. The single-mode terminal according to claim 7 or 8, wherein said third physical network interface module (N21) is further configured to check whether the source physical network address of the received data packet is consistent with the first and second physical network addresses. One of the physical network addresses (IP1_P1, IP1_P2) associated with the network interface modules (N11, N12) matches and, in case of a positive match, passes the received data packet to the second virtual network interface module (M2). 10. The single-mode terminal according to claim 7 or 8, wherein said system for maintaining IP session continuity further comprises a third physical network interface module (N21) configured to manage, and the single-mode terminal (T2) communicates with A second connection management application (C2) for connections between IP networks. 11. The single-mode terminal according to claim 10, wherein the second connection management application (C2) is further configured to manage the transmission and connection to the dual-mode terminal (T1) via a third communication system and an IP-based network. The second virtual network address (IP2_V1) associated with the second virtual network interface module (M2) and the third physical network address (IP2_P1) associated with the third physical network interface module (N21). 12. The single-mode terminal according to claim 10, wherein the second connection management application (C2) is further configured to manage the second virtual network interface module (M2) through the third communication system and IP-based network, from the dual The module terminal (T1) receives and utilizes the first virtual network address (IP1_V1) associated with the first virtual network interface module (M1), the first IP address associated with the first and second physical network interface modules (N11, N12). and second physical network addresses (IP1_P1, IP1_P2), and information related to the occurrence of switching between the first and second communication systems in the dual-mode terminal (T1). 13. A dual-mode terminal according to claim 1 for communicating with a single-mode terminal (T2) according to any one of claims 7-12 via an IP-based network, wherein said first IP-based protocol the stack (TCP/IP) is further configured to generate a data packet having a target physical network address equal to a second virtual network address (IP2_V1) associated with the second virtual network interface module (M2); and the The first virtual network interface module (M1) is further configured to change the target physical network address of the data packet from the first IP-based protocol stack (TCP/IP) to be associated with the third physical network interface module (N21) The third physical network address (IP2_P1) of . 14. The dual-mode terminal according to claim 13, wherein the first virtual network interface module (M1) is also configured to change the source physical network address of the data packet from the single-mode terminal (T2) to be consistent with the second virtual network address The second virtual network address (IP2_V1) associated with the interface module (M2), and the target physical network address of the data packet from the single-mode terminal (T2) is changed to the first virtual network address associated with the first virtual network interface module (M1). A virtual network address (IP1_V1). 15. The dual-mode terminal according to claim 13, wherein the physical network interface module (N11, N12) in the dual-mode terminal (T1) is also configured to check whether the source physical network address of the received data packet is consistent with the third The third physical network address (IP2_P1) associated with the physical network interface module (N21) matches, and in case of a positive match, the received data packet is passed to the first virtual network interface module (M1). 16. The dual-mode terminal according to claim 13, wherein the first connection management application (C1) is further configured to manage the first virtual network interface module (M1) through one of the first and second communication systems and the An IP-based network, receiving and using a second virtual network address (IP2_V1) associated with a second virtual network interface module (M2) and an address associated with a third physical network interface module (N21) from a single-mode terminal (T2) A third physical network address (IP2_P1). 17. The dual-mode terminal according to any one of claims 1-6 and 13-16, wherein the first and second physical network interface modules (N11, N12) in the dual-mode terminal (T1) are respectively Universal Mobile Communication system (UMTS) physical network interface module and wireless local area network (WLAN) physical network interface module. 18. The dual-mode terminal according to claim 17, wherein the first connection management application (C1) is further configured to, when the Received Signal Strength Indication (RSSI) is higher than a predetermined threshold, via a Wireless Local Area Network (WLAN) physical network interface The module interfaces with an IP-based network and when the Received Signal Strength Indicator (RSSI) drops below a predetermined threshold, checks for the presence of a Universal Mobile Telecommunications System (UMTS) network and, if the check is positive, switches to Universal Mobile Telecommunications System (UMTS) physical network interface module. 19. The dual-mode terminal according to claim 17, wherein the first connection management application (C1) is further configured to cause the dual-mode terminal (T1) to Connected to an IP-based network through a wireless local area network (WLAN) physical network interface module, when the received signal strength indicator (RSSI) drops below a first predetermined threshold, checks for the presence of a Universal Mobile Telecommunications System (UMTS) network, and upon checking If the result is affirmative, a dummy data packet is sent through the Universal Mobile Telecommunications System (UMTS) physical network interface module in order to warm up the connection to the Universal Mobile Telecommunications System (UMTS) network and avoid the Additional delay introduced by the Mobile Telecommunications System (UMTS) network, and switching to the Universal Mobile Telecommunications System (UMTS) physical network interface when the Received Signal Strength Indicator (RSSI) drops below a second predetermined threshold below the first predetermined threshold module. 20. A communication system comprising a dual-mode terminal (T1) according to any one of claims 1-6 and 13-19, and a single-mode terminal (T2) according to any one of claims 7-12 , both the dual-mode terminal (T1) and the single-mode terminal (T2) are configured to establish a connection through an IP-based network.