WO2011121206A1

WO2011121206A1 - Methods for registering a mobile terminal by means of an ip network access router, for managing the mobility of a terminal in an ip network, and for configuring a mobile terminal

Info

Publication number: WO2011121206A1
Application number: PCT/FR2011/050540
Authority: WO
Inventors: Sidi-Mohammed Senouci; Mohamed Cherif; Bertrand Ducourthial
Original assignee: France Telecom
Priority date: 2010-03-31
Filing date: 2011-03-17
Publication date: 2011-10-06

Abstract

The invention relates to methods for registering a mobile terminal by means of an IP network access router, for managing the mobility of a terminal in an IP network, and for configuring a mobile terminal. The invention proposes to assign a multicast group identifier solely to an IP network mobile terminal. Said multicast group identifier enables the creation of: a multicast address that acts a regional temporary IP address of the mobile terminal and is registered with the home agent thereof; and a multicast tree that associated with the multicast address to which the access routers of a remote network, visited by the terminal, subscribe in order to receive the data packets intended for the terminal and easily route said data packets to said terminal. The invention enables the optimization of the handover procedures in an IP network by relying on a hierarchical structure for the visited networks, local management of the mobility in said networks, and use of multicast communication protocols.

Description

Methods of registering a mobile terminal with an access router of an IP network, managing the mobility of a terminal in an IP network and configuring a mobile terminal Background of the Invention

The invention relates to the general field of telecommunications.

It more particularly concerns the management of the mobility of a terminal or "node" in a communication network based on the Internet protocol, also known as the Internet Protocol (IP) network. By "IP network" is meant here a set of IP networks or IP subnetworks connected to each other via equipment such as access routers.

The invention applies particularly preferably but not limited to networks based on IPv4 and IPv6 protocols.

In known manner, to manage the mobility of a node in an IPv6 network, the Mobile IPv6 protocol defines two IP addresses for each mobile node connected to the network:

a home IP address: this address is fixed and associated with the home network of the mobile node, and more specifically with its home agent. It is known to each of the correspondents of the mobile node; and

a temporary IP address (or "care-of-address"): this address is associated with the remote network visited by the mobile node, and more particularly with a remote agent (or "foreign agent") of the mobile node in the remote network .

The correspondence between the mother IP address of the mobile node and its temporary IP address is maintained at the level of the parent agent, in a table also known as the "binding table".

The update of this table is necessary to guarantee the routing to the mobile node of the communications intended for it, when this one is not in its network of origin.

During this update, the mobile node can not receive or send data. This can result in a high latency in communications, especially when the mobile node moves between several visited networks and at high speed, the frequency of handovers (Le. Passages or transfers from one visited network to another) increasing, such latency can be critical in the case of real-time applications, such as streaming video.

In addition, updating the correspondence table requires the exchange of many signaling messages, which contributes to the congestion of network equipment and in particular those of access networks.

To overcome these drawbacks, various solutions have been proposed in the context of the Internet Engineering Task Force (IETF).

A first proposal, called Hierarchical Mobile IPv6 (HIPv6), aims at reducing the signaling exchanged between the different devices of the network (mobile node, parent agent, remote agent, etc.) by introducing a new entity into the visited network, called Mobility Anchor Point (MAP). This new entity acts as a local remote agent managing the mobility of the node between the different access routers of the visited network that are connected to it.

Specifically, each mobile node has a regional temporary IP address, associated with the MAP, and a local temporary IP address associated with the access router to which the mobile node is connected.

Only the regional temporary IP address is known to the home agent, and associated with the home address. The correspondence between the temporary regional IP address and the local temporary IP address is maintained locally at the MAP level, thanks to the update messages sent by the mobile node to the MAP when it changes the access router.

The amount of signaling messages exchanged outside the local domain managed by the MAP is therefore reduced.

A second technique promoted as part of ΠΕΠΤ and called Fast Mobile IPv6 (FMIPv6), proposes to reduce the latency of handovers by limiting the time required for the acquisition by the parent agent of the temporary IP address of the mobile node.

To this end, FMIPv6 proposes to anticipate moving the mobile node and to configure in advance the temporary IP address associated with the future access router (NAR, "Next Access Router") to which the mobile node will be connected then same as it is still connected to its current access router (PAR, "Previous Access Router").

Note that in one or the other of the techniques mentioned above, it is necessary to verify the uniqueness of the temporary IP address assigned to the mobile node, which increases the latency of the handover. In addition, these two techniques only address one of the aforementioned problems related to the use of Mobile IPv6 in a mobile communication network, namely either excess signaling messages or handover latency.

One of the aims of the invention is to provide improvements over the state of the art.

Object and summary of the invention

The invention proposes to uniquely assign each mobile terminal (or node) of an IP network a multicast group identifier. This multicast group identifier advantageously allows the creation:

a multicast address, which acts as the regional temporary IP address of the mobile terminal and is registered with its home agent; and

a multicast tree associated with the multicast address, to which the access routers of the remote network in which the mobile terminal moves to receive the data packets intended for it, and to route them easily to the terminal, are subscribed to mobile. The invention thus makes it possible to optimize the handover procedures in an IP network, advantageously relying on a hierarchical structure of the networks visited by the mobile terminal and a local management of the mobility in these networks, as well as on the use multicast communication protocols.

Various entities cooperate in managing the mobility of the mobile terminal within the IP network according to the invention: the parent agent of the mobile terminal in its original network, the mobile terminal itself and, in each network visited by the terminal, the access routers to which it connects, and an entity called a rendezvous point which locally manages the mobility of the terminal in the visited network. It will be noted that for the purpose of the invention, the visited network is understood to mean an IP domain distinct from the original network of the mobile terminal and managed by a single one. meeting point.

Thus, according to a first aspect, the invention relates to a method for managing the mobility of a terminal in an IP network, implemented by a mother agent of the terminal, this method comprising, when the terminal connects to a visited network :

a step of updating in a database of a temporary IP address of the terminal on the visited network associated with a terminal IP address of the terminal, this temporary IP address being a multicast IP address associated with an assigned multicast group identifier; uniquely to the terminal; and

a step of establishing a tunnel between the home agent and a rendezvous point of the visited network in order to transmit data packets intended for the mobile terminal and received by the home agent, this tunnel being associated with a Multicast tree created for the multicast IP address in the visited network.

Specifically, a multicast session includes the tunnel and the multicast tree.

Correlatively, the invention also aims at a device for managing the mobility of a terminal in an IP network, this device providing a mother agent function for the terminal and comprising:

means for updating, in a database, a temporary IP address of the terminal on a visited network associated with a terminal IP address of the terminal, this temporary IP address being a multicast IP address associated with a group identifier multicast uniquely assigned to the terminal; and

means for establishing a tunnel between the home agent and a rendezvous point of the visited network in order to transmit data packets intended for the mobile terminal and received by the home agent, this tunnel being associated with a multicast tree created for the multicast IP address in the visited network;

the means for updating and establishing a tunnel being activated when the terminal connects to the visited network.

The invention therefore makes it possible to limit the signaling exchanged in the IP network to manage the mobility of the terminal within this network: the multicast IP address assigned to the terminal is only updated when it connects to a new visited network. Likewise, a new tunnel should only be established when the mobile terminal attempts to connect to a new visited network managed by a new rendezvous point, that is, only in a handover situation between multiple apartment access routers. networks visited.

On the other hand, during a handover between access routers of the same visited network, these only have to subscribe to the multicast tree created for the multicast address to receive the data intended for the terminal. mobile; it is not necessary to inform the parent agent of the mobile terminal. Mobility management of the mobile terminal within the same visited network is therefore transparent to the parent agent.

In addition, the multicast IP address is associated with a multicast group identifier uniquely assigned to the terminal, it is by unique construction. The invention thus advantageously makes it possible to avoid a procedure for verifying the uniqueness of the regional temporary IP address assigned to the mobile terminal, such as, for example, a procedure of the "Duplicate Address Detection" type described in RFC 4429 of I1ETF. , likely to accentuate the latency of the handover.

Furthermore, the invention only requires the creation of a multicast tree and the setting up of a tunnel between the home agent and the rendezvous point of the visited network in a multicast session. The use of the multicast tree makes it possible to avoid the creation of a tunnel between the access routers to which the mobile terminal connects, as is required for example in the FMIPv6 technique. It is not necessary for the rendezvous point to encapsulate or decapsulate the data for transmission on the multicast tree. The latency of the handover is thus reduced.

The invention therefore advantageously makes it possible to optimize the signaling required and the latency of a handover within the same visited network or between several visited networks.

In a particular embodiment, the management method further comprises:

a step of creating the multicast group identifier assigned to the terminal; and

a step of sending this identifier to the terminal.

This minimizes the signaling required to verify the uniqueness of the multicast group identifier assigned to the terminal.

Alternatively, the multicast group identifier may be chosen by the terminal and then its uniqueness validated by the parent agent.

According to a second aspect, the invention is directed to a configuration method implemented by a mobile terminal, comprising:

a step of obtaining a multicast group identifier, this identifier being uniquely assigned to the terminal;

a step of sending to an access router of a network visited or to be visited by the terminal of a message containing the multicast group identifier and requesting the subscription of the multi-cast tree router associated with the multicast group identifier to provide IP connectivity of the terminal on the network.

In a particular embodiment, the configuration method according to the invention further comprises a step of receiving a local temporary IP address created by the access router, this local temporary IP address comprising the multicast group identifier. and a network prefix of the access router.

Correlatively, the invention also relates to a mobile terminal comprising:

means for obtaining a multicast group identifier, this multicast group identifier being uniquely assigned to the terminal;

means for sending, to an access router of a network visited or to be visited by the terminal, a message containing the multicast group identifier and requesting the router's subscription to an associated multicast tree the multicast group identifier to provide IP connectivity of the terminal on the network;

means for receiving a local temporary IP address created by the access router, this local temporary IP address comprising the multicast group identifier and a network prefix of the access router.

By subscribing to the multicast tree associated with the multicast group identifier of the mobile terminal prior to its connection with it, the access router is assured of receiving the packets intended for the mobile terminal. It can then be transferred to the terminai via the established connection with it. In this way, the IP connectivity of the terminal on the network is ensured, the., The mobile terminal can communicate with other nodes through its home agent, these nodes using the mother IP address of the mobile terminal for him. send packages.

In addition, no packet destined for the mobile terminal will be lost during the establishment of its connection with the access router as long as it is subscribed to the multicast tree, and therefore a fortiori 'during a handover between several routers access.

According to the invention, a temporary local IP address is assigned to the mobile terminal which differs according to the access router to which it is connected or to which it will connect. The invention thus proposes a self-configuration of the local temporary IP address of the mobile terminal: it is advantageously created by the access router and contains the multicast group identifier uniquely assigned to the terminal. In this way, the uniqueness of the local temporary IP address of the mobile terminal is ensured and does not need to be controlled by a DAD type procedure mentioned above.

In addition, since the local temporary IP address depends on the multicast group identifier and the network prefix of the access router to which the mobile terminal wishes to connect, it can be configured in advance, according to principles similar to those used. in the FMIPvô protocol. In this way, the latency of the handover can be further diminished.

According to a third aspect, the invention provides a method of registering a mobile terminal by a first access router of an IP network, comprising: a step of receiving a multicast group identifier uniquely assigned to the terminal;

a subscription step to a multicast tree associated with the multicast group identifier, so as to receive data packets intended for the terminal via the multicast tree and to provide IP connectivity of the terminal on the network; ; and

a step of unsubscribing the multicast tree on reception of a predetermined message from a second access router connected to the terminal.

The recording method further comprises:

a step of creating a local temporary IP address for the terminal comprising the multicast group identifier and a network prefix of the first access router; and

a step of transmitting this temporary local IP address to the terminal.

Correlatively, the invention also provides an access router of an IP network comprising:

means for receiving a multicast group identifier uniquely assigned to a mobile terminal;

means for creating a local temporary IP address for the terminal comprising the multicast group identifier and a network prefix of the first access router;

means for transmitting this local temporary IP address to the terminal;

means for subscribing to a multicast tree associated with the multicast group identifier, so as to receive data packets intended for the terminal via the multicast tree and to provide IP connectivity of the terminal on the network; and

means for unsubscribing from the activated multicast tree on receipt of a predetermined message from a second access router connected to the terminal.

The recording method and the access router according to the invention have the same advantages as those described for the configuration method and the mobile terminal according to the invention,

The invention allows a very simple management of the mobility of a mobile terminal in an IP network: the access routers brought to establish a connection with the terminal simply have to subscribe or unsubscribe from the tree multicast according to principles known to those skilled in the art, to receive or no longer receive the data for the mobile terminal.

According to the invention, the unsubscription of the multicast tree by the first access router will be implemented only after the handover to the second access router, that is to say when the terminal will be connected to the second access router and upon request from the latter. It should be noted that the second access router may belong equally to the same visited network as the first access router or to a separate visited network.

In a particular embodiment of the invention, the group identifier is received from a third access router and the local temporary address is transmitted to the terminal via the third access router. . The recording method also comprises, when the IP connectivity of the terminal is provided via the first router, a step of sending the third access router of the predetermined message to unsubscribe from a multicast tree. associated with the multicast group ID.

In a variant, the recording method comprises:

a step of transmission to the second access router of the multicast group identifier assigned to the terminal;

a step of receiving the second access router of a temporary local IP address of the terminal, said local temporary IP address comprising the multicast group identifier and a. network prefix associated with the second access router; and

a step of transmitting this temporary local IP address to the terminal.

A configuration in advance of the temporary local IP address of the terminal is thus permitted by the invention, with knowledge of the network prefix associated with the second access router.

According to a fourth aspect, the invention provides a communication system in an IP network comprising:

a mobile terminal as described above;

a rendezvous point managing a network visited by the mobile terminal and arranged to establish a multicast tree associated with the multicast group identifier;

a device for managing the mobility of the mobile terminal according to the invention and able to establish a tunnel with the rendezvous point, this tunnel being associated with the multicast tree managed by the rendezvous point; and

an access router of the visited network, as described above;

this communication system being adapted to. routing data packets destined for the mobile terminal and received by the management device, to the mobile terminal via the tunnel and the multicast tree.

In a particular embodiment, the various steps of the mobility management, registration and configuration methods are determined by computer program instructions.

Consequently, the invention also relates to a computer program on an information carrier, this program being capable of being implemented in a mobility management device or more generally in a computer, this program comprising instructions adapted to the implementation of the steps of a mobility management method as described above.

The invention also relates to a computer program on an information medium, this program being capable of being implemented in an access router or more generally in a computer, this program comprising instructions adapted to the implementation of steps of a recording method as described above. The invention also relates to a computer program on an information medium, this program being capable of being implemented in a mobile terminal or more generally in a computer, this program comprising instructions adapted to the implementation of steps of a configuration method as described above.

These programs can use any programming language, and be in the form of source codes, object codes, or intermediate codes between source code and object code, te! only in a partially compiled form, or in any other desirable form.

The invention also relates to a computer-readable information medium, comprising instructions of a computer program such as those mentioned above.

The information carrier may be any entity or device capable of storing the program. For example, the medium may comprise storage means, such as a ROM, for example a CD-ROM or a microelectronic circuit ROM, or magnetic recording means, for example a floppy disk or a disk. hard.

On the other hand, the information medium may be a transmissible medium such as an electrical or optical signal, which may be conveyed via an electrical or optical cable, by radio or by other means. The programs according to the invention may in particular be downloaded on an Internet-type network.

Alternatively, the information carrier may be an integrated circuit in which the program is incorporated, the circuit being adapted to execute or to be used in the execution of the method in question.

It is also possible to envisage, in other embodiments, the mobility management method, the registration method, the configuration method, the communication system, the mobile terminal, the access router and the device. In accordance with the invention, the present invention comprises all or some of the above-mentioned features.

Brief description of the drawings

Other features and advantages of the present invention will emerge from the description given below, with reference to the accompanying drawings which illustrate an embodiment having no limiting character. In the figures:

- Figure 1 shows schematically a management system according to the invention, in a particular embodiment;

FIGS. 2A to 2D schematically represent the hardware architecture of a rendezvous point, a home agent, a mobile terminal and an access router in accordance with the invention and belonging to the system of FIG. management shown in Figure 1;

FIG. 3 schematically represents the main steps implemented in accordance with the invention during a handover of the mobile terminal of FIG. 1 between an access point of its mother network and an access point of a visited network; FIG. 4 represents an example of an association table updated by the home agent HA;

FIG. 5 represents an example of a temporary local IP address allocated to the mobile terminal;

FIG. 6 represents an example of a multicast address that can be used in the context of the invention;

FIG. 7 schematically represents the main steps implemented in accordance with the invention during handover of the terminal of FIG. 1 between two access routers belonging to visited networks managed by rendezvous points; you separate; and

FIG. 8 is a schematic representation of the main steps implemented in accordance with the invention during a handover of the terminal of FIG. 1 between two access routers belonging to the same visited network and managed by the same point. of appointment.

Detailed description of an embodiment

FIG. 1 represents, in its environment, a communication system 1 in an IP network 2, according to the invention, in a particular embodiment.

In the example envisaged here, the network 2 is an IP network based on the IPv6 protocol.

However, this assumption is not limiting, the invention being similarly similar to other communication networks, such as for example to a network based on the IPv4 protocol.

According to the invention, the system 1 is able to manage the mobility of a MN finished it in the IP network 2 between multiple subnets IP network 2 For simplicity the term "networks" will be used ^'to designate these "subnets". Here we will limit ourselves to three subnetworks, namely the home network or home network HN ("home network") of the mobile terminal, and two remote networks VN1 and VN2 ("foreign network") visited by the terminal.

By mobile terminal is meant here any mobile communication device capable of connecting to its original network and other remote networks (or domains) visited by the terminal, to exchange data with another device 2. Thus, the mobile terminal MN can be indifferently a mobile phone, a laptop, a personal assistant PDA (Personal Digital Assistant), etc., equipped with a wireless communication module. .

The implementation of the invention is based on a hierarchical architecture of the visited networks VN1 and VN2 by the terminal, and a local management of the mobility of the terminal within these networks. This local management is provided through an entity called here meeting point. This rendezvous point is, for example, the remote agent of an IPv4 network or the mobility anchor point (MAP) of an IPv6 network.

Thus, in the example envisaged here, each of the networks VN1, VN2 is managed respectively by a rendezvous point RVP1, RVP2, each rendezvous point being in charge of a plurality of equipment such as proxy servers and network access routers, thus forming a multilevel architecture, For example in FIG. rendezvous point RVP1 is connected to the AR11 access router through the Pli proxy server and the P13 proxy server.

. Such an architecture is advantageously very flexible and can be extended by adding proxy servers and intermediate hierarchical levels. Of course this example is not. given as an illustration, and other architectures could be considered. In particular, the rendezvous point RVP1 can be connected directly to the access routers AR11, AR12, AR13, etc.

According to the invention, the management of the mobility of the mobile terminal MN within the network 2 is based on a multicast tree defined specifically for the mobile terminal. It should be noted that, in a manner known to those skilled in the art, a multicast tree allows each member of a group of subscribers to this tree to transmit and / or receive messages via the multicast group IP address which it is associated with it (each member of the group uses this multicast IP address as long as it does not leave the group). The invention thus takes advantage of existing multicast communication protocols for easily and reliably conveying the data packets to the mobile terminal during its movements in the network 2.

To this end, the rendezvous point RVP1 is equipped with:

means for creating a TREE1 multicast tree, uniquely assigned to the mobile terminal, and from which the access routers to which the mobile terminal is connected during its movement in the network VN1 are subscribed and the set intermediate proxy servers between these access points and the RVP1 rendezvous point; and

means for establishing, with a mother agent HA of the terminal MN defined in its mother network HN, a tunnel T1 associated with this multicast tree.

In this way, the data packets received by the home agent HA and intended for the mobile terminal MN are encapsulated by the home agent and routed to the rendezvous point RVP1 using the tunnel T1. Then they are routed via the multicast tree TREE1, to the access router to which the mobile terminal MN is connected using a multicast communication protocol known per se.

Note that the rendezvous point RVP1 here has hardware architecture of a computer, as shown schematically in Figure 2A. It comprises in particular a processor 3A, a random access memory 4A, a read-only memory 5A, a non-volatile memory 6A and communication means 7A for communicating through the network VN1 as well as with entities of other networks, for example with the mother agent HA of the MN terminal. For this purpose, the communication means 7A comprise in particular a network interface respecting the standards known to those skilled in the art.

The RVP2 rendezvous point is similar in structure and operation to the RVP1 rendezvous point and will not be described further here.

To inform the home agent that! (S) multicast tree (s) the data packets intended for the MN terminal must be sent when it is in a remote network of its mother network (typically here when the mobile terminal MN visits the VNl or VN2 networks), two addresses are registered for the mobile terminal MN in the IP network 2 at its home agent HA:

a fixed IP address H @, known from each of the CN correspondents of the terminal, and associated with the parent agent HA; and

a temporary IP address which is, according to the invention, a muiticast IP address uniquely associated with the terminal MN and corresponding to the muiticast tree created specifically for the terminal by the rendezvous point of the network visited by the terminal . Note that when a handover between two visited networks associated with two separate meeting points, two muiticast addresses can be associated with the same terminal to ensure the continuity of communications of the mobile terminal during the handover.

The correspondence between the fixed IP address and the temporary IP address of the terminal MN is maintained in a database BT of the mother agent HA, also known as the association or correspondence table ("binding"). table "). Within the meaning of the invention, a database designates a set or any structure of data.

The home agent HA is a device for managing the mobility of the terminal MN in the IP network 2 according to the invention. It has here the hardware architecture of a computer, shown schematically in FIG. 2B, and notably comprises a processor 3B, a random access memory 4B, a read-only memory 5B, and a non-volatile memory 6B in which the table BT is stored. . The read-only memory 5B constitutes a recording medium in accordance with the invention, readable by the processor 3B of the home agent and on which is recorded a computer program according to the invention, comprising instructions for the execution of the steps of a mobility management method according to the invention, described later.

The home agent HA also comprises communication means 7B for communicating on the network HN as well as with entities of other networks, for example with the rendezvous points RVPl and RVP2 of the remote networks VN1 and VN2 visited. by the mobile terminal MN. For this purpose, the communication means 7B comprise in particular a network interface respecting the standards known to those skilled in the art.

Thus, through the BT association table updated by the home agent and the muiticast tree created by each rendezvous point of the networks visited by the terminal MN, it ensures a reliable and optimized management of the mobility of the MN terminal in the IP network 2, limiting not only the packet losses but also the latency of the handovers operated by the MN terminal within the IP2 network.

The terminal MN is a mobile terminal according to the invention, here having the hardware architecture of a computer shown schematically in Figure 2C. It comprises in particular a processor 3C, a random access memory 4C, a read-only memory 5C, and a non-volatile memory 6C. The read-only memory 5C constitutes a recording medium in accordance with the invention, readable by the processor 3C and on which a computer program is recorded. according to the invention, comprising instructions for carrying out the steps of a configuration method according to the invention, described later:

As mentioned above, the mobile terminal MN also comprises a wireless communication module 7C, flui for communicating on the networks HN, VN1 and VN2. The wireless communication module 7C comprises for example a WiFi® interface (Wireless Fidelity) known per se.

The mobile terminal MN can access the networks VN1 and VN2 via access routers (eg for the network VN1, the access routers AR11, AR12, AR13 and AR14) in a known manner. These access routers are here all in accordance with the invention and have the hardware architecture of a computer, shown schematically in FIG. 2D.

They each comprise in particular a 3D processor, a 4D RAM, a 5D read-only memory, and a non-volatile memory 6D. The read-only memory 4D constitutes a recording medium in accordance with the invention, readable by the 3D processor and on which is recorded a computer program according to the invention, comprising instructions for carrying out the steps of a method according to the invention, described later.

The access routers also include 7D communication means for communicating on the VN1 and VN2 networks as well as with entities of other networks. The communication means 7D comprise for example a WiFi® interface,

We will now describe, with reference to FIGS. 3 to 8, the main steps of the mobility management method of the terminal MN, of the recording method and of the configuration method according to the invention, in a particular embodiment in which these methods are implemented respectively by the home agent HA, by the access routers of the networks VN1 and the network VN2, and by the mobile terminal MN represented in FIG.

Various mobility situations are envisaged to illustrate the mobility management of the MN terminal in the IP network 2:

a first situation SI in which the mobile terminal MN connects to its mother network HN and then moves to an access router of the remote network VN1. This situation is described with reference mainly to FIG. 3;

a second situation S2 in which the mobile terminal MN moves between the access router AR11 of the network VN1 and an access router AR21 of the network VN2. This is, in other words, a mobility situation between different domains (or networks) managed by separate meeting points. This situation is described with reference mainly to FIG. 7; and

a third situation S3 in which the mobile terminal MN moves between two access routers of the network VN1. It is, in other words, a mobility situation within the same domain managed by a rendezvous point. This situation is described with reference mainly to FIG.

Figure 3 schematically illustrates the steps implemented in the first situation SI. When the mobile terminal MN connects to its home network HN (step E10), its home agent HA allocates, in known manner, a mother IP address here namely the H @ address.

Further> in accordance with the invention, the home agent HA uniquely assigns the mobile terminal MN a multicast group identifier GID (step E20). By "uniquely assign" is meant here that each mobile terminal attached to the home agent HA is associated with it to a distinct group identifier.

The group identifier GID is here a 32-bit integer created by the home agent according to one of the procedures described in the RFC 3307 of IIETF entitled "Allocation Guidelines for IPv6 Multicast Addresses". More precisely, it consists of the last 32 bits of the MAC (Medium Access Control) address of the MN terminal. In this way, we guarantee the uniqueness of the identifier.

As a variant, the multicast group identifier GID can be created by the terminal MN and then validated by the home agent HA, which ensures by this validation of its uniqueness.

The address H @ and the identifier GID are sent by the home agent to the terminal MN and the correspondence between the address H @ and the identifier GID is stored in the table BT.

An example of a BT association table is shown in FIG. 4. The state of the table for the MN terminal at the end of the step E20 is illustrated by the line L1.

It is now assumed that the MN terminal moves and attempts to connect to the remote network VN1 via the access router AR11 (step E30). To this end, it initiates a procedure for obtaining a local temporary IP address on the visited network VN1 and for the subscription of the access router AR11 to a multicast tree associated with the multicast group identifier GID.

For this purpose, the terminal MN sends the identifier GID to the access router AR11 in a message BU (Binder Update), conforming to the protocol MIPv6 (step E40).

The message BU also includes here the address H @ and a field "mode" placed at the value "init". This value is representative, because the MN terminal connects for the first time to a remote network of its mother network. The message BU is a message requesting the subscription of the router to a multicast tree associated with the identifier GID within the meaning of the invention.

Of course, other ways of signaling to the access router that the terminal is connecting for the first time to a remote network and that the access router AR11 must subscribe to a multicast tree associated with the identifier GID can to be considered.

In the embodiment described here, upon receipt of the message BU, the access router AR11 implements a stateful autoconfiguration of the local temporary IP address of the mobile terminal MN. More precisely, it extracts the identifier GID of the message BU and creates, from this identifier, the temporary local IP address Co @ ll (step E50).

The Co @ ll address conforms to the IPv6 address format. With reference to the figure

5, it comprises 128 bits, among which are the multicast group identifier GID and the network prefix "AR11-net-prefix" of the router AR11. The concept of network prefix is known to those skilled in the art and will not be described in more detail here. It will be noted that the presence of the identifier GID in the address Co @ ll ensures its uniqueness on the network VN1, the latter having been uniquely assigned to the terminal MN. It is therefore not necessary to implement a supplementary procedure for checking the uniqueness of the Co @ 11 address, such as for example a procedure of the "Duplicate Address Detection" type described in the document RFC 4429 entitled "Optimistic Duplicate Address Detection (DAD) for IPv6".

In the embodiment described here, the "mode" field of the message BU having the value "init", the access router AR11 also builds, from the multicast group identifier GID, a multicast IP address MC @ 1 for the mobile terminal MN (step E60). This address conforms to the IPv6 multicast address format.

The access router AR11 sends the address Co @ ll and the multicast IP address MC @ 1 thus created to the terminal MN (step E70), for example in a message BAck (Binder Acknowledge) according to the protocol MIPv6. The local temporary IP address advantageously allows the MN terminal to communicate in adhoc mode with other equipment and other terminals of the network VN1.

In known manner, the IPv6 protocol defines two types of multicast addresses, i.e., permanent multicast addresses and temporary multicast addresses. There are also various categories of temporary multicast addresses, such as for example general multicast addresses ("Gênerai Temporay Multicast Address"), addresses derived from an IPv6 unicast prefix ("Unicast-Prefic-based IPv6 Temporary Multicast Address"). ), multicast addresses embedding the address of the rendezvous point ("Embedded-RP IPv6 Temporary Multicast Adress") and SSM addresses adapted to a specific source ("Source Specifies Multicast Address").

Although each of these categories of temporary multicast addresses may be suitable for the construction of the MC @ 1 address, preference will be given to an SSM multicast address. This facilitates the establishment of a multicast session with the parent agent HA. In addition, in the invention, only the mother agent HA acts as a source with respect to the multicast address MC @ 1 by routing on this address the data packets intended for the mobile terminal MN. However, in a known manner, the SSM addresses are particularly well suited to this particular case.

The format of an SSM multicast address is recalled in Figure 6. The construction of such an address is described in more detail in RFC 3306 of IIETF entitled "Unicast-Prefix-based IPv6 Multicast Addresses".

Following the creation of the MC @ 1 address, the router AR11 broadcasts on its local link a notification message for the creation of a new multicast group associated with the identifier GID and the multicast address MC @ 1 (step E80). This local link connects the AR11 router to the P13 proxy server. The AR12 router is also connected to this local link.

The message broadcast by the router AR11 conforms here to the multicast group management protocol MLDv2 (Multicast Listener Discovery v2), known to those skilled in the art, and contains the multicast address MC @ l (which, by construction, contains the group ID GID). This is for example a HearIPv5Multicast message (GID, MC @ l, adr_HA), adrJHA designating the IP address of the mother agent HA.

This HearlPvBMulticast message is for the creation by the RVPl rendezvous point of a TREEl multicast tree associated with the identifier GID and the multicast address MC @ 1. It is propagated step by step to the rendezvous point RVPl by the equipment acting as intermediaries between the access router ARll and the rendezvous point RVPl,

The message HearIPvôMulticast makes it possible to inform the intermediate equipment between the access router AR11 and the rendezvous point (typically the proxy server P13), that a multicast group has been created for the mobile terminal MN and that these must subscribe to the TREEl multicast tree associated with this multicast group and using the MC @ 1 address. In addition, it requires the P13 proxy server to register the mobile terminal MN as a subscriber to the TREEl multicast tree.

The message HearlPvôMuItîcast thus constitutes not only a request for creation of the multicast tree TREEl intended for the rendezvous point RVPl but also a request for subscription of the access router AR11 to the tree TREEl.

Upon receipt of this message, the proxy server P13 stores the terminal MN as a subscriber to the TREEl multicast tree and in turn transmits on its local link a message HearIPv6Multicast (GID, MC @ l, adr_HA) (step E90) . This message is intended in particular for the proxy server P11 to register the proxy server P13 as a subscriber to the TREE1 multicast tree, subscribe itself to the multicast tree TREE1 and propagate the request for creation of the TREEl multicast tree to the rendezvous point RVPl.

Upon receipt of this message, the proxy server P11 registers the proxy server P13 as a subscriber to the TREEl multicast tree and subscribes to the rendezvous point RVPl to the TREEl multicast tree with the help of a HearIPv6Multicast message (step E100),

It should be noted that the broadcast of the message HearIPv6Multîcast (GID, MC @ l, adr_HA) and the subscription to the TREEl multicast tree are implemented at each higher hierarchical level separating the access router AR11 from the rendezvous point RVPl. , so to build the TREEl multicast tree,

In response to the message HearIPv6Multicast received from the proxy server P13 at the step E100, the rendezvous point RVPl sends a message to the home agent HA to complete the construction of the TREEl tree, this tree taking root on the point of Appointment RVPl and having as sole source the parent agent HA (step E110).

This message complies with the Protocol Independent Multicast Protocol (SSM), which is described in more detail in IETF RFC 3569, "An Overview of Source- Specifies Multicast (SSM)." This is for example a PIM message (adr_HA, GID) join.

The home agent HA extracts the identifier GID of this message and reconstructs from this identifier the multicast address SSM MC @ 1. For this, it applies a procedure identical to that applied by the access router AR11. The home agent HA then stores the address MC @ 1 in the table BT as the temporary IP address of the terminal MN associated with the mother IP address H @ (step E120). The state of the table BT for the terminal MN at the end of the step E120 is illustrated by the line L2 of FIG. 4,

Then, a tunnel T1 associated with the multicast tree TREE1 is established between the home agent HA and the rendezvous point RVPl, according to means known to those skilled in the art (step E13G). A multicast session comprising the tunnel T1 and the tree TREE1 is thus created for the exchanges between the mobile terminal MN and its home agent HA.

Once the TREEl multicast tree and the Tl tunnel have been created, the rendezvous point RVPl informs the mobile terminal MN, the router AR11 and the servers P11 and P13 that the tree associated with the identifier GID and with the address multicast @ MC1 is created, for this it uses a notification message multicast address Mcast_Addr_Notif (GID) (step E140).

In this way, when data packets for the mobile terminal MN arrive at the level of the home agent HA, they are encapsulated by the latter and then sent in the tunnel T1 to the mobile terminal MN. The rendezvous point RVPl transmits the packets received from the home agent via tunnel T1 on the TREEl multicast tree using the multicast address MC @ 1. The packets thus reach all the subscribers to the tree TREE1, and in particular the fold server, the server P13 and the router AR11. The router AR11 then transmits the packets received to the terminal MN on its local link. It will be noted that the multicast header is removed only at the mobile terminal MN. The IP connectivity of the terminal MN is then ensured via the access router AR11 and the multicast tree TREE1 (step E150), ie, the terminal MN can communicate with any corresponding node with the mother agent HA using the mother address H @ of the terminal MN.

With reference to FIG. 7, a procedure that is quasi-similar to the initialization procedure represented in FIG. 3 is implemented when the terminal MN is in a handover situation between two remote networks managed by two separate rendezvous points. . The steps similar to those of Figure 3 will not be described again for the sake of simplification.

To illustrate this situation, one now places himself in the situation S2 introduced earlier in which the MN terminal moves (step F10) and considers a handover of the access router AR11 of the network VN1 to the access router AR21 of the network VN2. The AR11 and AR21 routers are managed respectively by the rendezvous points RVPl and RVP2.

In order to further minimize the latency of the handover between the two access routers, the invention advantageously proposes to implement a pre-configuration of the local temporary IP address of the mobile terminal MN on the network VN2.

To this end, in known manner, the mobile terminal MN has the ability to identify in advance the access routers to which it will connect. For example, it may discover access routers in its vicinity using level 2 mechanisms, such as a frequency sweep in a WLAN, or alternatively, if its path is predefined, have a list of access routers located along its path. It can then obtain from its current access router information concerning the access routers so identified, such as for example their network prefixes. Such mechanisms are already implemented in the protocol

Fast ΜΙΡνβ and will not be described further here. .

The terminal MN then sends the router AR11 a message

BU (Co @ il, adr_HA, GID, mode = inter) initialization of a handover to the router AR21 (step F20). This message is in fact a message sent to the router AR21 to request its subscription to a multicast tree associated with the identifier GID.

It contains the multicast group identifier GID, the temporary local IP address Co @ II of the terminal on the network VN1, its mother IP address H @ and the network prefix of the router AR21. The value "inter" taken by the mode field in the message BU specifies to the router AR11 that the terminal MN wishes to set up a handover to a domain (ie remote network) distinct from that to which the router AR11 belongs and the subscription of the router AR21 to a multicast tree associated with the identifier GID.

Upon receipt of this message, the router AR11 sends the router AR21 a HI handover initiation message (Co @ ll, adr_HA, GID, mode = inter), to verify that the router AR21 accepts the connection of the mobile terminal MN and ie if necessary, request its subscription to a multicast tree associated with the identifier GID (step F30), This message contains the group identifier

GID, the local temporary IP address Co @ ll and the mother IP address H @ of the mobile terminal MN.

On receipt of this message, the router AR21 checks whether it can accept a connection with the terminator MN (step F40). For example, he can check on this occasion that he has the necessary resources to manage the communications of the mobile terminal MN.

If necessary, it creates a temporary local IP address Co @ 21 for the mobile terminal MN on the network VN2, this address being associated with the router AR21 (step F50). address

Co @ 21 is created similarly to the address Co @ ll, from the identifier GID and the network prefix associated with the router AR21.

In parallel, the mode field of the message HI having the value "inter", the router AR21 builds a new multicast IP address MC @ 2 for the terminal MN (step F60). The multicast address MC @ 2 is constructed, similarly to the multicast address MC @ 1, from the identifier GID. This is a temporary multicast address SSM, as shown in FIG. 6. It will be noted that the multicast address MC @ 2 may be identical to the multicast address MC @ 1 as is the case here, or in a different variant of the multicast address MC @ i, for example if it embeds the prefix of the rendezvous point.

Then it sends the local temporary address Co @ 21 and multicast address MC @ 2 thus created to the router AR11 (step F70), for example in a handover acceptance message

HAck (Co @ ll, Co @ 21, MC @ 2) (Handover Acknowledgment).

The router AR11 in turn transmits the local temporary IP address Co @ 21 and the multicast address MC @ 2 to the terminal MN, for example in a message BAck (Co @ 21, MC @ 2) (Binder

Acknowledgment) (step F80). Following the creation of the MC @ 2 address, the router AR21 broadcast on its local link a message HearIPv6Multicast (GID, MC @ 2, adr_HA) notification of the creation of a new multicast group associated with. the identifier GID and the multicast address MC @ 2 (step F90).

This message is for the creation by the RVP2 rendezvous point of a TREE2 multicast tree associated with the identifier GID and the multicast address MC @ 2. It is propagated step by step to the rendezvous point RVP2 by the equipment acting as intermediaries between the access router AR21 and the rendezvous point RVP2.

The message HearIPv6MuIticast (GID, MC @ 2, adr_HA) informs the proxy server P23 that a multicast group has been created for the mobile terminal MN and that the latter must subscribe to the multicast tree TREE2 associated with this multicast group and corresponding to the address MC @ 2. In addition, it requires the P23 proxy server to register the mobile terminal MN as a subscriber to the TREE2 multicast tree. The message HearIPv6Multlcast thus constitutes not only a request for creation of the multicast tree TREE2 destined for the rendezvous point RVP2 but also a request for subscription of the access router AR21 to the tree TREE2.

On receiving this message, the proxy server P23 registers the terminal as a subscriber to the multicast tree TREE2 and in turn transmits on its local link a message HearIPv6MuItîcast (GID, MC @ 2, adr_HA) (step F100). This message is intended in particular for the proxy server P.21 so that it registers the proxy server P23 as a subscriber to the TREE2 multicast tree, subscribes itself to the multicast tree TREE2, and propagates the request. creation of the TREE2 multicast tree to the RVP2 rendezvous point. Upon receipt of this message, the proxy server P21 registers the proxy server P23 as a subscriber to the multicast tree TREE2 and in turn subscribes to the rendezvous point RVP2 to the multicast tree TREE2 at the same time. using the HearIPv6Multicast message (step F110). In response to the message HearIPv6MuIticast received from the proxy server P23 in the step F110, the rendezvous point RVP2 sends a message conforming to the PIM-SSM protocol to the home agent HA to complete the construction of the tree TREE2, this tree taking root on the rendezvous point RVP2 and having as sole source the parent agent HA (step F120).

The home agent extracts the multicast group identifier GID from this message and reconstructs the multicast address MC @ 2 from this identifier. It then updates the BT table by storing as the temporary IP address of the terminal MN associated with the H @ address, the multicast address MC @ 2 (step F130). The table BT is then in the state shown in Figure 4 by the line L3.

Note that if the multicast address MC @ 2 is distinct from the multicast address MC @ 1, the mother agent HA stores in the table BT, in association with the address H @, the two multicast addresses MC @ 1 and MC @ 2, until contrary instructions are received from one of the meeting points.

Then, a tunnel T2 associated with the multicast tree TREE2 is established between the home agent HA and the rendezvous point RVP2 (step F14D). A multicast session is thus created for the tree TREE2 with the home agent HA. In this way, when data packets for the mobile terminal MN arrive at the level of the home agent HA, they are encapsulated by the latter and then sent to the two tunnels T1 and T2 to the mobile terminal MN.

Each RVP1 and RVP2 rendezvous point transmits the packets received from the home agent to the associated multicast tree.

Thus the access routers AR11 and AR21 both receive the data packets intended for the MN terminal via the trees TREE1 and TREE2 to which they are subscribed respectively. In this way, it is ensured that no data packet destined for the terminal MN is lost during the handover between the AR11 and AR21 access points.

Once the TREE2 multicast tree and the T2 tunnel have been created, the rendezvous point RVP2 informs the mobile terminal MN, the access router AR21 and the proxy servers P21 and P23 that the tree TREE2 associated with the identifier of GID group and multicast address @ MC2 is created by a notification message Mcast_Addr_Notif (GID) (step F150). When the connection between the router AR21 and the terminal MN is established (step F160), the IP connectivity of the terminal MN is then ensured not only via the access router AR11 and the multicast tree TREE1, but also by via the AR21 router and the TREE2 multicast tree (step F170).

Following the establishment of its connection with the router AR21, the mobile terminal MN informs neighboring equipment VN2 network (ie, located near the radio, MN terminal) its presence by broadcasting its temporary local IP address Co @ 21 ( step F180). This equipment is for example routers or other terminals, which can thus communicate with the MN terminal through adhoc communications.

Once the connection with the mobile terminal MN is established, the router AR21 routes, if necessary, the packets received via the multicast tree TREE2 to the mobile terminal MN and sends the router AR11 a request to unsubscribe from the tree multicast TREE1 and terminate the multicast session created with the home agent for that tree (step F190).

Upon receipt of this message, the access router AR11 informs the rendezvous point RVP1 that the multicast tree TREE1 must be deleted as well as the tunnel T1 (step F200).

The rendezvous point RVP1 deletes the multicast tree TREE1 and sends a message to the home agent HA to terminate the multicast session associated with the tree TREE1 and the tunnel T1 (step F210).

Upon receipt of this message, the session is closed and the Tl tunnel deleted. The home agent updates the base BT by deleting the multicast address MC @ 1 associated with the terminal MN if it is different from the multicast address MC @ 2 (step F220), the table BT is then in the state shown in Figure 4 by line L4.

We will now describe, with reference to Figure 8, the management of a handover of the termina! MN, within the same domain, between two access routers that depend on the same rendezvous point. The steps similar to those of FIGS. 3 and 7 are not described again for the sake of simplification. To illustrate this situation, we now place ourselves in the situation S3 previously introduced in which, following step E150, the terminal MN moves in the network VN1 and considers a handover of the access router AR11 to the access router AR12, The AR11 and AR21 routers are managed by the rendezvous point RVP1, so that, according to the invention, the mobile terminal MN changes local temporary IP address (the latter being associated with the access router to which the terminal is connected) but no multicast address since it remains in the same remote network.

As previously described for inter-network handover, the invention proposes a pre-configuration of temporary IP addresses. So, we assume here that the termina! mobile MN considers a handover of the AR11 access router to the AR12 access router that it has previously identified and selected (step G10).

To do this, it sends the router AR11 a message BU (Co @ ll, adr_HA, GID, mode = intra) initialization of a handover to the router AR12 (step G20). This message is in fact a message sent to the router AR12 to request its subscription to a multicast tree associated with the identifier GID.

It contains the identifier GID, the temporary IP address Co @ 11 of the terminal MN and its mother IP address H @, as well as the network prefix of the router AR12. The value "intra" taken by the mode field in the message BU specifies to the router AR11 that the terminal MN wishes to set up a handover in the same domain to which the router AR11 belongs and the subscription of the router AR12 to the multicast tree associated with the identifier GID.

Upon receipt of this message, the router AR11 sends the router AR12 a handover HI initialization message (Co @ ll, adr_HA, GID, mode = intra), to verify that the router AR12 accepts the connection of the mobile terminal MN and ie where appropriate, request its subscription to a multicast tree associated with the identifier GID (step G30). This message contains the group identifier GID, the temporary IP address Co @ ll and the mother IP address H @ of the mobile terminal MN.

Upon receipt of this message, the router AR12 verifies whether it can accept a connection with the MN terminal (step G40), as previously described in step F40.

If necessary, it creates a temporary local IP address Co @ 12 for the mobile terminal MN, this address being associated with the router AR12 (step G50). This address is created similarly to the local temporary IP address Co @ ll, from the GID identifier and the AR12 router network prefix.

Then it sends the address thus created to the router AR11 (step G60), for example in a handover acceptance message HAck (Co @ 11, Co @ 12) (Handover Acknowledgment).

The router AR11 in turn transmits the second temporary IP address Co @ 12 to the mobile terminal MN, for example in a Back message (Co @ 12 (Binder acknowledgment) (step G70).

In parallel, the handover envisaged by the mobile terminal MN being carried out within the VN1 network itself (specified by the value "intra" of the mode field of the message HI), it is useless to create a new multicast address and, a fortiori, a new multicast tree. It is the multicast address MC @ 1 and the multicast tree TREE1 that will be used by the access router AR12 to receive the data packets intended for the mobile terminal MN.

Thus, the router AR12 broadcasts on its local link a message HearIPv6Multicast (GID, MC @ l, adr_HA) to the particular attention of the proxy server P13 so that it saves it as a subscriber to the multicast tree ( step G80).

Note that if the proxy server P13 is not subscribed to the TREEl tree, it sends a message HearIPv6Multicast (GID, MC @ l, adr_HA) to the proxy server Fold to subscribe, as described in relation to Figure 3.

The tree TREE1 and the tunnel Tl are already created (the table BT updated by the parent agent is then in the state shown in Figure 4 by the line L2), when data packets for the mobile terminal MN arrive at the level of the home agent HA, they are encapsulated by the home agent and then sent in the tunnel T1 to the mobile terminal MN. The rendezvous point RVP1 forwards received packets to the TREEl multicast tree.

Thus the access routers AR11 and AR12 each receive the data packets intended for the terminal MN via the TREEl multicast tree to which they are subscribed. In this way, it is ensured that no data packet intended for the MN terminal is lost during the handover between the two access routers.

When the connection between the router AR12 and the terminator MN is established (step G90), the IP connectivity of the terminal MN is thus ensured both via the access router AR11 and via the access router AR12, via the TREEl multicast tree.

Following the establishment of its connection with the router AR12, the mobile terminal MN informs neighboring equipment VN1 network (ie, located near the MN terminal radio) of its presence by broadcasting its new temporary local IP address Co @ 12 ( step G100). This equipment is for example routers, or other terminals. In this way, they can communicate with him through adhoc communications.

Once the connection with the mobile terminal MN is established, the router AR12 routes the packets received via the multicast tree TREE1 to the mobile terminal MN and sends the router AR11 a request to unsubscribe from the multicast tree TREE1 (step G110 ).

Upon receipt of this message, the access router AR11 unsubscribes with the rendezvous point RVP1 of the multicast tree TREE1 (step G120).

Claims

1. A method of registering a mobile terminal (MN) by a first access router (AR11, AR12, AR21) of an IP network (2), characterized in that it comprises:

a step of receiving (E40, F20, G20) a multicast group identifier uniquely assigned to the terminal;

a step of creating (E50, F60, G50) a local temporary IP address (Co @ 11, Co @ 12, Co @ 21) for the terminal comprising the multicast group identifier and a network prefix of the first router; access;

a step of transmitting (E70, F70, G60) said temporary local IP address to the terminal;

a subscription step (E80, F90, G80) to a multicast tree associated with the multicast group identifier, so as to receive data packets intended for the terminal via the multicast tree and to ensure a IP connectivity of the terminal on the network (2); and

a step of unsubscribing (G120, F210) from the multicast tree on reception (G110, F200) of a predetermined message from a second access router to which the terminal is connected.

2. Recording method according to claim 1, characterized in that said group identifier (GID) is received from a third access router (AR11) and in that the local temporary IP address is transmitted to the terminal by through the third access router.

3. Recording method according to claim 2, characterized in that it further comprises, when the IP connectivity of the terminal is provided via the first access router (F170), a sending step (F190 ) to the third access router of said predetermined message to unsubscribe from a multicast tree associated with the multicast group identifier.

4. Recording method according to claim 1, characterized in that it comprises:

a transmission step (F30, G30) to the second access router of said multicast group identifier assigned to the terminal;

a reception step (F70, G60) of the second access router (AR21, AR12) of a local temporary IP address (Co @ 21, Co @ 12) of the terminal, said local temporary IP address comprising the identifier of multicast group and a network prefix associated with the second access router; and

a step of transmitting (F80, G70) this temporary local IP address to the terminal.

A computer program comprising instructions for performing the steps of the recording method according to claim 1 when said program is executed by a computer.

A method for managing the mobility of a terminal (MN) in an IP network (2), implemented by a home agent (HA) of the terminal, said method comprising, when the terminal connects to a visited network ( VN1, VN2):

a step of updating (E120, F130) in a database (BT) of a temporary IP address of the termina! on the visited network, associated with a terminal IP address (H @) of the terminal, said temporary IP address being a multicast IP address (MC @ I, MC @ 2) associated with a uniquely assigned multicast group identifier (GID) at the terminal; and

a step of establishing (E130, F140) a tunnel (T1, T2) between the home agent and a rendezvous point (RVP1, RVP2) of the visited network in order to transmit data packets intended for the terminating ! mobile and received by the home agent, said tunnel being associated in a multicast session to a multicast tree created for said multicast IP address in the visited network.

7. Management method according to claim 6 characterized in that it further comprises:

a step of creating (E20) the group identifier assigned to the terminal; and

a step of sending this identifier to the terminal.

A computer program comprising instructions for executing the steps of the management method according to claim 6 when said program is executed by a computer.

9. Configuration method implemented by a mobile terminal (MN), characterized in that it comprises:

a step of obtaining (E20) a multicast group identifier (GID), said identifier being uniquely assigned to the terminal;

a sending step (E40, F20, G20) to an access router (AR11, AR21, AR12) of a visited network (VN1, VN2) or to be visited (VN2) by said terminal a message containing the multicast group identifier and requesting the subscription of said router to a multicast tree created for a multicast IP address associated with the multicast group identifier to provide IP connectivity of the terminal on the network

a step of receiving (E70, F80, G70) a local temporary IP address (Co @ 11, Co @ 21, Co @ 12) created by the access router, said local temporary IP address comprising the identifier of multicast group and a network prefix of the access router.

A computer program comprising instructions for executing the steps of the configuration method according to claim 9 when said program is executed by a computer.

11. Access router (AR11, AR12, AR21) of an IP network (2), characterized in that it comprises:

means for receiving a multicast group identifier (GID) uniquely assigned to a mobile terminal;

means for transmitting said local temporary IP address to the terminal, and

means for subscribing to a multicast tree associated with the multicast group identifier, so as to receive data packets intended for the terminal via the multicast tree and to provide IP connectivity of the terminator; and

Device (HA) for managing the mobility of a terminal (MN) in an IP network (2), said device providing a mother agent function for the terminal and comprising:

means for updating, in a database (BT), a temporary IP address of the terminal on a visited network (VN1, VN2) associated with a mother IP address (H @) of the terminal, said IP address temporary being a multicast IP address (MC @ 1, MC @ 2) associated with a multicast group identifier (GID) uniquely assigned to the terminal; and

means for establishing a tunnel (T1, T2) between the home agent and a rendezvous point (RVP1, RVP2) of the visited network in order to transmit data packets intended for the mobile terminal and received by the the parent agent, said tunnel being associated in a multicast session with a multicast tree created for said multicast IP address in the visited network;

said means for updating and establishing a tunnel being activated when the terminal connects to said visited network.

13. Mobile terminal (MN) characterized in that it comprises:

means for obtaining a multicast group identifier (GID), said multicast group identifier being uniquely assigned to the terminal;

means for sending to an access router (AR11, AR12, AR21) of a visited IP network (VNi, VN2) or to be visited (VN2) by the terminal, a message containing the multicast group identifier and requesting the subscription of said router to a multicast tree associated with the multicast group identifier to provide IP connectivity of the terminal in the network;

means for receiving a local temporary IP address created by the access router, said local temporary IP address comprising the multicast group identifier and a network prefix of the access router.

14. Communication system (1) in an IP network (2) comprising: a mobile terminal (MN) according to claim 13;

a rendezvous point (RVP1, RVP2) managing a visited network (VN1, VN2) by the mobile terminal and arranged to establish a multicast tree associated with the multicast group identifier;

a device (HA) for managing the mobility of the mobile terminal according to claim 12 and able to establish a tunnel (T1, T2) with the rendezvous point / said tunnel being associated in a multicast session with the tree multicast managed by the meeting point; and

an access router of the visited network (AR11 _; AR12, AR21) according to claim 11;

said communication system (1) being able to route data packets for the mobile terminal and received by the management device, to said mobile terminal via said tunnel and said multicast tree.