WO2008031967A2

WO2008031967A2 - Method of supervising a session for accessing a service set up by a client terminal by means of a dynamic configuration protocol

Info

Publication number: WO2008031967A2
Application number: PCT/FR2007/051877
Authority: WO
Inventors: Christophe Alter; Jean-Marc Corolleur
Original assignee: France Telecom
Priority date: 2006-09-12
Filing date: 2007-09-05
Publication date: 2008-03-20
Also published as: WO2008031967A3

Abstract

The invention relates to a method of managing a session for accessing a service set up by a client terminal through a network by means of a protocol for dynamically providing at least one configuration parameter for said client terminal, called the dynamic configuration protocol, the management of said access session being performed by means of exchanges of access session management messages complying with a protocol for supervising an access session, between the client terminal and at least one item of equipment of said network. The method according to the invention comprises, when setting up said access session, a step of reception by the client terminal, with said configuration parameter, of a list of at least one identification parameter for at least one item of equipment of said network, termed the operator equipment, with which said client terminal is authorized to exchange at least one access session management message.

Description

METHOD FOR SUPERVISION OF A SERVICE ACCESS SESSION

ESTABLISHED BY A CLIENT TERMINAL USING A PROTOCOL OF

DYNAMIC CONFIGURATION

The invention lies in the field of telecommunications, and more particularly in the field of fixed access networks.

Such fixed access networks allow for example a user to access the global Internet network, by narrow-band connection, or, more recently, by means of a broadband connection such as ADSL (abbreviation English "Asymmetric Digital Subscriber One", or in French

"Asymmetrical Digital Subscriber Line")

For historical reasons and in similarity to what is used in narrow-band connections, broadband Internet access for most telecommunications operators worldwide is achieved by using a protocol PPP (Point-to-Point Protocol). The installed base of users subscribing to ADSL and equipped with hardware using this protocol is therefore very important. The PPP protocol allows, among other things, access control, of which user authentication is a component, and the assignment of IP addresses to the client terminals, and includes the notion of establishing and terminating sessions between a client. and a server. Such a PPP protocol is defined in referenced document RFC 1661 (RFC for Request For Comments) established by the IETF (group for participation in the standardization of the Internet, abbreviation of the English terms Internet Engineering Task Force).

Since the notion of session is clearly defined in the PPP protocol, it is possible for a telecommunications operator to know with accuracy the duration of a session that is in progress or has been completed. This allows him to control and bill in a standard and accurate way the consumption of its users.

However, the lack of flexibility of the PPP protocol, in particular for applications broadcast in multicast and / or requiring distinct qualities of service is one of the main disadvantages of the PPP protocol.

In this context, the question of the relevance of keeping an architecture based on the use of the PPP protocol, especially for Internet access in a network arises. The players in the telecommunications industry have therefore studied the possibilities open to them as alternatives to the PPP protocol. Of these, DHCP (short for Dynamic Host Configuration Protocol, or "Dynamic Host Configuration Protocol") is widely used and deployed in local and private networks. It is used by some telecom operators for the deployment of services such as ADSL television or video telephony.

The DHCP protocol allows a device that connects to a network to dynamically obtain, that is to say without particular intervention, configuration parameters such as a logical address or IP address. Such a DHCP protocol is defined in the referenced document RFC 2131.

The use of the DHCP protocol for access to services of the Internet type also makes it possible to homogenize all the services offered by a telecommunications operator by using the same IP address assignment protocol since, as indicated above, high, some of these services such as television by ADSL for example, are already in conformity with this protocol. The use of the DHCP protocol is also a step towards the convergence of fixed and mobile networks and a better mutual integration of the services offered by the operator. With reference to FIG. 1, when a terminal 1 connects to a network R, a link is established between a DHCP client 2, embedded in the equipment 1, and a DHCP server 3 present in the network R.

Unlike the case of the PPP protocol, the notion of session does not exist as such in the DHCP protocol. When implementing the DHCP protocol, the configuration parameters of a DHCP client 2, such as its IP address, are assigned for a specified duration called "lease", after which they are released and become available again to other users, which optimizes network resources. However, a DHCP client 2 that sees its lease complete may request the DHCP server 3 to extend the lease. If the DHCP server 3 does not receive a lease extension request from the DHCP client 2, before the lease expires, or if the lease is not extendable, it makes available at the end of the lease the lease. IP address that he had assigned to this DHCP client 2 for the duration of his lease. It should be noted that although the notion of session does not exist as such in the DHCP protocol, it is common in the field of dynamic configuration protocols to speak, by misuse of language, of session to designate a lease.

However, since the notion of session is not clearly defined in the DHCP protocol, it is difficult, if not impossible, for a service provider to know exactly how long a session is running or has been completed. Thus, it is difficult for him to control and bill in a standard and precise way the consumption of his users.

To overcome this drawback, it has been suggested to use the ICMP protocol (Internet Control Message Protocol). Such a protocol is defined in RFC 792. The ICMP protocol is designed for the transmission of messages between different terminals or equipment punctuating the network. These messages make it possible to report processing errors of datagrams circulating in the network. Thus, depending on the routing status of an ICMP message, it is possible to know the state of a session established by a terminal in accordance with the DHCP protocol, or access session. In fact, if a terminal or a device of the network sends an ICMP message requiring a response from the terminal or the destination device (such a message may consist for example of an echo message), and that the transmitting terminal does not receive no answer, it may mean that the access session is broken. Thus, depending on the nature of the ICMP messages sent and their status, it is possible to determine the state of an access session.

However, some terminals, such as demodulators for television by ADSL or Set Top Box, do not allow the use of the ICMP protocol. Indeed, such terminals are equipped with security means such as firewalls, preventing ICMP message exchanges. This choice was made by the service providers to ensure the security of these terminals, the purpose being to protect them from attempts by third parties to usurp the proposed services. However, such a measure does not allow service providers to monitor the sessions established by these terminals via the ICMP protocol.

Thus, there is a need for service providers to be able to accurately know the duration of a session that is in progress or has been completed in order to be able to control the various access sessions initialized using DHCP while continuing to ensure the security of their terminals against usurpations of services.

The invention responds to this need by proposing a method of managing a session of access to a service established by a client terminal through a network by means of a dynamic provisioning protocol of at least one parameter of configuration of said client terminal, called dynamic configuration protocol, the management of said access session being performed by means of exchange of access session management messages compliant with a supervision protocol of an access session. The method according to the invention is particular in that it comprises, during setting up said access session, a step of reception by the client terminal, with said configuration parameter, of a list of at least one identification parameter of at least one piece of equipment of said network, said operator equipment , with which said client terminal is authorized to exchange at least one access session management message.

Such a dynamic configuration protocol may for example be of the DHCP type. The session supervision protocol can be of ICMP type.

By providing the client terminal, during the establishment of the access session, a list of identification parameters of one or more devices arranged in the network, it is possible to bypass the security means implemented in the client terminal. . Indeed, if a management message comes from a device whose identification parameter is known to the client terminal, then these messages are not filtered by the security means and management of the session is then possible.

Equipment disposed in the network and whose identification parameter is known to the client terminal is called operator equipment. The client terminal is authorized to exchange access session management messages only with operator equipment. The invention has an advantage, also in the context of the use of client terminals not equipped with security means. Indeed, by providing the list of identification parameters to these client terminals, it limits the equipment from which they can normally receive access session management messages. Thus, the security of the client terminals is increased, since we choose the equipment with which it is possible for them to dialogue.

According to a first characteristic of the method according to the invention, said identification parameter of said operator equipment consists of at least one logical address of said operator equipment. Conventionally, the operator equipment has a fixed logical address. Such a logical address is allocated to them during their first commissioning and for the entire duration of their operation. The value of this address does not change over time unless the service provider decides to change the addressing policy of his network.

Finally, a logical address is associated with a single piece of equipment, which is not the case, for example, with a physical address. Thus, by identifying a device by its logical address, it limits the risk of communicating with the wrong equipment. According to a second characteristic of the method according to the invention, prior to any transmission by the client terminal of a management message of said access session intended for a piece of equipment of said network, said method comprises a step of verifying that the equipment to which the management message of said access session is sent, is an operator equipment.

Thus, the client terminal can send management messages of the access session to a device whose logical address has been transmitted by the dynamic configuration protocol during the establishment of the access session. This makes it possible to guarantee the security of the client terminals by preventing them from communicating information to non-concerned equipment.

According to a third characteristic of the method which is the subject of the invention, the latter comprises a step of reception by said operator equipment of the configuration parameter of the client terminal to / from which the operator equipment is authorized to send / receive messages. managing said access session.

This makes it possible, for example, for the operator equipment to be able to identify the client terminal transmitting the access session management messages that it receives and to respond only to the management messages of a session. accesses issued by a client terminal whose configuration parameters it knows.

Thus, it is possible to supervise an access session by means of the method according to the invention only by means of a client terminal and an operator equipment which know their mutual identities.

According to a fourth characteristic of the method which is the subject of the invention, when the client terminal detects a lack of response to at least one management message of said access session sent to an operator equipment, said method comprises a step of sending by the client terminal a message conforming to the dynamic configuration protocol requesting the assignment of a new configuration parameter in order to establish a new access session.

In the method according to the invention, since the client terminal can only communicate with authorized operator equipment and able to respond to its supervision messages, a lack of response can only mean a break in the access session.

The method according to the invention makes it possible, in case of termination of the access session detected by the client terminal, to automatically restart a new session. Thus, it is no longer necessary to manually reset the client terminal to establish a new access session as is the case in the prior art.

According to another characteristic of the method according to the invention, when the operator equipment detects a lack of response to at least one management message of said access session sent to the client terminal, said method includes a transmission step by said equipment of a message conforming to the dynamic configuration protocol requesting the release of the configuration parameter assigned to the client terminal during the establishment of the access session in order to terminate said access session. The method according to the invention makes it possible, in the event of termination of the access session detected by the operator equipment, to terminate the access session correctly by releasing the configuration parameters associated with the client terminal. This makes it possible to avoid any usurpation of these configuration parameters by a third party client terminal and to be able to reassign them to another client terminal.

The subject of the invention is also a client terminal comprising means for establishing a service access session across a network by means of a dynamic provisioning protocol for at least one configuration parameter of said service terminal. client terminal, called dynamic configuration protocol, and means for transmitting / receiving management messages of said access session conforming to a supervision protocol of an access session.

Such a client terminal is particular in that it comprises means for receiving a list of at least one identification parameter of at least one piece of equipment of said network, called operator equipment, with which said client terminal is authorized to exchange at least one management message of said access session.

According to a first characteristic of the terminal that is the subject of the present invention, the latter comprises means for comparing identification parameters of an equipment item of said network with the identification parameters contained in said list, prior to transmission by said means. transmission, a management message of said access session to said equipment. According to a second characteristic of the terminal that is the subject of the present invention, it comprises means for detecting a lack of response from the operator equipment to a management message of said access session sent by said terminal. client, and means for transmitting a message conforming to the dynamic configuration protocol, requesting the allocation of a new configuration parameter when a lack of response is detected by said detecting means.

The invention also relates to an operator equipment comprising means for transmitting / receiving messages for managing a session for accessing a service, to / from a client terminal, said management messages of said session. access being in accordance with a session supervision protocol, said access session being established by a client terminal through a network by means of a dynamic provisioning protocol of at least one configuration parameter of said client terminal, called dynamic configuration protocol. Such equipment is particular in that it comprises means for receiving at least one configuration parameter of the client terminal to / from which the operator equipment is authorized to send / receive management messages of said session. 'access.

According to a feature of the equipment object of the present invention, it further comprises means for detecting an absence of response from the client terminal to a management message of said access session sent by said operator equipment, and means for transmitting a message conforming to the dynamic configuration protocol, requesting the release of the configuration parameter assigned to said client terminal in order to terminate said access session when a non-response is detected by said detection means.

The invention also relates to a system comprising at least one client terminal, at least one server and at least one device, a session for accessing a service being established by said client terminal near said server, said access session being compliant a protocol for dynamically providing at least one configuration parameter of said client terminal, called a dynamic configuration protocol, said access session being furthermore managed by means of access session management message exchanges between the client terminal and the equipment, said management messages said access session being in accordance with a supervision protocol of an access session.

Such a system is particular in that said client terminal is a client terminal according to the invention, and in that said equipment is an operator equipment according to the invention.

The invention also relates to a computer program comprising program code instructions for executing the steps of the method relating to the client terminal when said program is executed by a processor. The invention also relates to a computer program comprising program code instructions for executing the steps of the method relating to the operator equipment when said program is executed by a processor.

The invention finally relates to a signal intended to be transmitted between a first device and a client terminal interconnected by a communication network, said signal carrying a configuration message conforming to a dynamic configuration protocol, said configuration message comprising a field containing a list comprising at least one identification parameter of at least one second piece of equipment of said network with which the client terminal is authorized to exchange management messages of a session.

Other features and advantages will be apparent from the reading of preferred embodiments described with reference to the drawings in which:

- Figure 1, already commented in connection with the prior art, shows an architecture comprising various network equipment involved in the establishment of a DHCP session;

FIG. 2 shows an architecture in which the method according to the invention is implemented, FIG. 3 describes an operating algorithm of the method according to the invention,

FIGS. 4 and 5 describe an operating algorithm of the method according to the invention implemented in a client terminal; FIG. 6 describes an operating algorithm of the method according to the invention implemented in an operator equipment,

FIG. 7 proposes a timing diagram of exchanges of requests between a client terminal on the one hand and an operator equipment on the other and, between this client terminal on the one hand and a DHCP server on the other hand, FIG. 8 proposes a timing diagram of exchanges of requests between a client terminal on the one hand and an operator equipment on the other hand and, between this operator equipment on the one hand and a DHCP server on the other hand,

FIG. 9 illustrates a frame conforming to the DHCP protocol conveying in one of its options a list of logical addresses of operator equipment. Throughout the rest of the description, we will limit ourselves to a particular example of application to the DHCP and ICMP protocols. The invention is of course also applicable to other close or similar protocols.

Fig. 2 shows a communication system in which the present invention is implemented. Such a system comprises a client terminal 20, such as a set top box for example, connected to a communication network R. A DHCP server 30 is also connected to the network R and a plurality of devices 40,.

The client terminal 20 comprises means for setting up a session in accordance with the DHCP protocol, or access session, means for sending / receiving messages 22 conforming to the DHCP protocol, transmission / reception means 23 ICMP-compliant messages, logical address comparison means 24, and means for detecting an absence of response to an ICMP message. The function of these various means will appear more clearly when describing the implementation of the access session management method object of the present invention. Such a client terminal 20 is sometimes equipped with a firewall system which limits in particular the exchange of ICMP messages between the client terminal and network equipment by blocking either the reception of such messages or the transmission of reply messages to these messages. incoming and this, whatever the equipment 40, at the origin of the first message. Thus, when faced with this kind of client terminal, it is impossible to be able to supervise an access session initialized using DHCP using the ICMP protocol.

The equipment 40, for its part, comprises transmission / reception means 41 for messages conforming to the DHCP protocol, transmission / reception means 42 for messages conforming to the ICMP protocol, and detection means 43 for a message. no response to an ICMP message. The function of these different means will also appear more clearly when describing the implementation of the management method of an access session. With reference to FIG. 3, in a first step E1, the client terminal 20 transmits, via its DHCP message transmission / reception means 22, to the DHCP server 30 a request for allocation of configuration parameters so as to it is possible to establish, using its means of establishing a DHCP session 21, an access session through the network R. These configuration parameters are, for example, a logical address or IP address. In response to this request, and in accordance with the invention, the client terminal 20 receives, in a step E2, from the DHCP server 30 a message containing the configuration parameters necessary for the establishment of an access session and a list {X} comprising a plurality of IP addresses of different network devices with which the client terminal is authorized to exchange messages in accordance with the ICMP protocol. Such equipment is called 40 operator equipment.

A frame conforming to the DHCP protocol, or DHCP frame, is represented in FIG. 9. Such a frame constitutes the message received by the client terminal during step E2. This DHCP frame has a plurality of options, each of which may contain parameters useful for reestablishing an access session. For example, the third DHCP option is an option that indicates the identity of routers to use to route data to a client terminal or network equipment, while option number 51 is an option whose function is to indicate the duration of the DHCP lease allocated to a terminal. One of these options contains, in accordance with the invention, the list {X} containing the IP addresses of the different operator equipment with which the client terminal is authorized to exchange management messages of a session.

Returning to FIG. 3, in a step E3, the operator equipment 40 receives, by means of its DHCP transmission / reception means 41, a message sent by the DHCP server communicating to it the configuration parameters associated with the client terminal. 20. The operator equipment 40, then has means of identification of the client terminal 20 to avoid dialogue with third-party client terminals.

Thus, the client terminal 20 has data enabling it to identify the equipment 40, sending ICMP-compliant messages, or ICMP messages. This makes it possible to bypass the firewall devices present in the client terminals 20.

With reference to FIG. 4, the client terminal 20 receives, thanks to its ICMP transmitting / receiving means 23, during a step E4, a message

ICMP from an equipment of the network R. During a step E5, the client terminal 20 compares through its means of comparison 24, the IP address of the equipment that sent the ICMP message with the list {X } containing the IP addresses of the operator equipment 40, with which it is authorized to exchange management messages of the access session.

If the IP address of the sending equipment of the received ICMP message belongs to the list {X}, then the client terminal 20 transmits, during a step E7, a response to this ICMP message in the form of a other ICMP message.

If the IP address of the sending equipment of the received ICMP message does not belong to the list {X}, then the client terminal 20 does not respond to this ICMP message, this corresponds to the step E7. With reference to FIG. 5, following the sending of an ICMP message by the client terminal 20 to an operator equipment 40, the client terminal 20 can wait for a response if the type of ICMP message sent is a message requiring an answer, such as an echo message for example. During a step E8, the client terminal 20 detects, by means of its detection means 25, a lack of response from the operator equipment 40,. If, after a predetermined number of consecutive sendings of the same ICMP message to the operator equipment 40, the latter does not respond, then the client terminal transmits, in a step E9, a DHCP message to the DHCP server 30. Such a message consists in asking the DHCP server 30 to issue new configuration parameters in order to allow the client terminal 20 to establish a new access session.

This request for new configuration parameters is therefore done automatically. Thus, it is no longer necessary, as is currently the case, to manually request the allocation of these new parameters by cutting off the power supply of the client terminal or by resetting it.

With reference to FIG. 6, following the transmission of an ICMP message by an operator equipment 40 to the client terminal 20, the operator equipment 40 can wait for a response from the client terminal 20 if the type Issued ICMP message is a message that requires a response. At During a step F1, the operator equipment 40 detects, by means of its detection means 43, a lack of response from the client terminal 20. If after a predetermined number of consecutive shipments of the same message ICMP to the client terminal 20, it does not respond, then the operator equipment 40 transmits, during a step F2, a DHCP message to the DHCP server 30. Such a message is to ask the server DHCP 30 to release the configuration parameters assigned to the client terminal 20 for the duration of the access session.

It is therefore possible to request the closing of the access session automatically. Thus, in the event of a break in an access session, the configuration parameters associated with the client terminal whose session is broken are released, thus avoiding any risk of spoofing thereof by a third party terminal. In addition, once released, the configuration parameters associated with the client terminal can be assigned to a new client terminal. FIG. 7 represents a diagram of the protocol exchanges carried out during the implementation of the method according to the invention. When the client terminal 20 wishes to establish an access session through the network R, the establishment of the access session begins with the sending by the client terminal 20 of a request DHCP Request. On receipt of this message the DHCP server 30 responds to the client terminal 20 by sending a DHCP Offer message. Such a DHCP Offer message contains the configuration parameters necessary for the establishment of the access session as well as the list {X} of the IP addresses of the operator equipments 40, with which the client terminal 20 is authorized to exchange management messages. of the session. Once the access session is established, the client terminal 20 exchanges ICMP Request and Response messages with the operator equipment 40, so as to supervise the session.

If following the sending of several ICMP Request messages by the client terminal 20, it receives no response from the operator equipment 40 ,, then the client terminal sends a DHCP Request message to destination of the DHCP server 30 by which it asks him to provide new configuration parameters. The DHCP server 30 responds to the client terminal 20 by sending a DHCP Offer message containing new configuration parameters. FIG. 8 represents a diagram of the protocol exchanges carried out during the implementation of the method according to the invention. When the client terminal 20 wishes to establish an access session through the network R, the establishment of the access session begins with the sending by the client terminal 20 of a request DHCP Request. On receipt of this message the DHCP server 30 responds to the client terminal 20 by sending a DHCP Offer message. Such a DHCP Offer message contains the configuration parameters necessary for the establishment of the access session as well as the list {X} of the IP addresses of the operator equipments 40, with which the client terminal 20 is authorized to exchange management messages. of the access session. Once the access session is established, the operator equipment 40 exchanges ICMP Request and Response messages with the client terminal 20 so as to supervise the access session.

If following the sending of several ICMP Request messages by the operator equipment 40, it receives no response from the client terminal 20, then the operator equipment 40 sends a DHCP Release message to the DHCP server 30 by which it asks him to release the configuration parameters assigned to the client terminal for the duration of the access session since it is considered broken.

Claims

A method of managing a service access session established by a client terminal over a network by means of a dynamic provisioning protocol of at least one configuration parameter of said client terminal, called dynamic configuration, the management of said access session being performed by means of exchange of access session management messages compliant with an access session supervision protocol, between the client terminal and at least one piece of equipment said network, characterized in that said method comprises, during the establishment of said access session, a step of reception by the client terminal, with said configuration parameter, of a list of at least one parameter of identification of at least one device of said network, said operator equipment, with which said client terminal is authorized to exchange at least one access session management message.

2. Method according to claim 1, characterized in that said identification parameter of said operator equipment consists of at least one logical address of said operator equipment.

3. Method according to any one of the preceding claims, characterized in that prior to any transmission by the client terminal of a management message of said access session to a device of said network, said method comprises a step to verify that the equipment to which the management message of said access session is sent, is an operator equipment.

4. Method according to any one of claims 2 or 3, characterized in that it comprises a step of reception by said operator equipment, the configuration parameter of the client terminal to / from which the operator equipment is authorized to send / receive management messages of said access session.

5. Method according to any one of the preceding claims, characterized in that when the client terminal detects a lack of response to at least one access session management message sent to an operator equipment, said method comprises a step of sending by the client terminal a message conforming to the dynamic configuration protocol requesting the assignment of a new configuration parameter in order to establish a new access session.

6. Method according to one of the preceding claims, characterized in that when the operator equipment detects a lack of response to at least one access session management message sent to the client terminal, said method comprises a step d transmitting by said equipment a message conforming to the dynamic configuration protocol requesting the release of the configuration parameter assigned to the client terminal during the establishment of the access session in order to close said access session.

7. Client terminal comprising means for establishing a session for accessing a service over a network by means of a dynamic provisioning protocol for at least one configuration parameter of said client terminal, called a connection protocol. dynamic configuration, and means for transmitting / receiving management messages of said access session conforming to a supervision protocol of an access session, characterized in that it comprises means for receiving a list at least one identification parameter of at least one device of said network, said operator equipment, with which said client terminal is authorized to exchange at least one management message of said access session.

8. Customer terminal according to claim 7, characterized in that it comprises means for comparing identification parameters of a said network equipment with the identification parameters contained in said list, prior to transmission by said transmission means, an access session management message to said equipment.

9. Customer terminal according to any one of claims 7 to 8, characterized in that it comprises means for detecting a lack of response from the operator equipment to an access session management message. issued by said client terminal, and means for transmitting a message conforming to the dynamic configuration protocol, requesting the allocation of a new configuration parameter when a lack of response is detected by said detection means.

10. Operator equipment comprising means for transmitting / receiving messages for managing a session of access to a service to / from a client terminal, said management messages of said access session being in accordance with a session supervision protocol, said access session being established by said client terminal through a network by means of a dynamic provisioning protocol of at least one configuration parameter of said client terminal, called a dynamic configuration protocol , characterized in that it comprises means for receiving at least one configuration parameter of the client terminal to which the operator equipment is authorized to send / receive management messages of said access session.

1 1. Operator equipment according to claim 10, characterized in that it further comprises means for detecting a lack of response from the client terminal to an access session management message sent by said client terminal. operator equipment, and means for transmitting a message conforming to the dynamic configuration protocol, requesting the release of the configuration parameter assigned to said client terminal in order to terminate said access session when a non-response is detected by said means detection.

12. System comprising at least one client terminal, at least one server and at least one device, a session for accessing a service being established by said client terminal near said server, said access session being in accordance with a protocol of dynamic provision of at least one configuration parameter of said client terminal, called dynamic configuration protocol, said access session being furthermore managed by means of exchanges of access session management messages between the client terminal and the equipment, said management messages of said access session being in accordance with a supervision protocol of an access session, characterized in that said client terminal is in accordance with any one of claims 7 to 9, and in that said equipment is an operator equipment according to any one of claims 10 to 11.

A computer program comprising program code instructions for performing the steps of the method according to any one of claims 1 to 3 and 5 when said program is executed by a processor.

A computer program comprising program code instructions for performing the steps of the method according to any one of claims 4 and 6 when said program is executed by a processor.

15. Signal intended to be transmitted between a first device and a client terminal interconnected by a communication network, said signal carrying a configuration message conforming to a dynamic configuration protocol, said configuration message comprising a field containing a list comprising at least one identification parameter of at least one second device of said network with which the client terminal is authorized to exchange management messages of a session.