WO2009152844A1

WO2009152844A1 - Selective route optimisation

Info

Publication number: WO2009152844A1
Application number: PCT/EP2008/057541
Authority: WO
Inventors: Nikolaus Albert Fikouras; Carmelita GÖRG; Frank Pittmann; Asanga Udugama
Original assignee: Nokia Siemens Networks Oy
Priority date: 2008-06-16
Filing date: 2008-06-16
Publication date: 2009-12-23

Abstract

The present invention relates to a method and device for service control in a telecommunication connection between a mobile node (2) and at least one correspondent node (3), the method being implemented in a home agent (1) associated to the mobile node (2) and the at least one correspondent node (3). The home agent (1) intervenes in the data exchange between the mobile node (2) and the at least one correspondent node (3) and generates a general control message to the mobile node (2) or to the at least one correspondent node (3) for supporting or refusing services between the mobile node (2) and the at least one correspondent node (3).

Description

SELECTIVE ROUTE OPTIMISATION

FIELD OF THE INVENTION The present invention relates to a method and device for ser^¬ vice control in a telecommunication connection.

BACKGROUND OF THE INVENTION

The high availability of different wireless access technolo- gies in future telecommunication networks will elevate the issue of increased resource control for users and operators to critical status. Efficient resource management is needed, which means in the context of this invention (and focussing on future (mobile) telecommunication networks) that the net- work operator should have proper means to manage its networks efficiently, i.e., network-controlled.

The Internet Engineering Task Force (IETF) promotes specifi^¬ cations that adopt an end-to-end modus operandi. In the case of Mobile IPv6 the specification intends to prevent interme^¬ diate network entities (e.g. a home agent) controlled by the network operator to dictate the services that can be re^¬ quested by mobile nodes.

SUMMARY OF THE INVENTION

It is an object of the present invention to extend the capa^¬ bilities of a home agent in order to enable network operators to acquire dynamic control over the mode of communication used in all traffic exchanged between a mobile node and a correspondent node.

According to the invention, these objects are accomplished in particular by a method and a device according to the inde- pendent claims. Preferred embodiments are specified by the dependent claims .

The invention comprises a method for service control in a telecommunication connection between a mobile node and at least one correspondent node. The method is being implemented in a home agent associated to the mobile node and the at least one correspondent node. The home agent may intervene in the data exchange between the mobile node and/or the at least one correspondent node. The method may furthermore generate a general control message to the mobile node and/or to the at least one correspondent node for supporting or refusing services between the mobile node and/or the at least one corre^¬ spondent node .

The proposed method is simple and easy to deploy, as it re^¬ quires only slight modification of the Mobile IPv6 protocol at central entities such as the home agents and mobile nodes, leaving entities in the core or in other administrative do- mains untouched.

This method may advantageously allow mobile network operators (MNOs) in general to improve their quality of service pro^¬ vided to mobile nodes. The invention may furthermore offer the possibility to enable billing and tariffing services for mobile nodes roaming away from the MNO' s network infrastruc^¬ ture without any further assistance from the remote MNO. The invention may offer the possibility to enable the MNO to con^¬ trol which network peers may contact a mobile node and with what communication mode. The invention furthermore may pro^¬ vide enhanced security to mobile nodes because it may force all traffic for mobile nodes to traverse through an MNO en^¬ tity that may host an enhanced firewall and can sustain net^¬ work attacks . The method is described in view of its use in a home agent which is communicating with a mobile node and a correspondent node. The method is of course not limited to the use in a home agent and the communication with the above-mentioned de^¬ vices but can also be applied on any data processing unit in a telecommunication network or any device associated to the telecommunication network.

Preferably, the method for service control in a telecommuni^¬ cation connection may comprise that the home agent may fur^¬ ther execute the steps of intercepting a first message sent by the mobile node and/or the at least one correspondent node. Furthermore the method may comprise the step of select- ing a filter from a list of filters. The method may also com^¬ prise the step of filtering the first message received from the mobile node and/or the correspondent node by the filter selected by the home agent in view of matching the first mes^¬ sage with a predetermined value or pattern provided by the selected filter.

The list of filters may comprise information on data struc^¬ tures for messages relating to communication in a (telecommu^¬ nication) network. Furthermore the list of filters may com- prise information on data values or data patterns for mes^¬ sages relating to communication in a (telecommunication) network .

In a preferred embodiment the method for service control in a telecommunication connection may comprise that the home agent may execute the step of selecting a trigger from a list of triggers based on the result of filtering of the first mes^¬ sage by the home agent . The list of triggers may contain information on application servers for providing services being related to the informa^¬ tion derived from the filtering of the first message. The list of triggers may furthermore contain information on ser- vice units provided by the telecommunication network or any other network.

Preferably, the method for service control in a telecommuni^¬ cation connection may comprise that the home agent may fur- ther execute the step of sending the selected trigger to a service control means of a telecommunication network. Furthermore the method may comprise the step of receiving a re^¬ sponse message generated by the service control means indi^¬ cating the result of processing the selected trigger by the service control means.

The service control means may comprise an application server which provides data and/or command messages for initiating or refusing a specific application or service. Furthermore the service control means may comprise a decision means with a policy decision point determining whether a specific service may be enabled or disabled.

The method for service control in a telecommunication connec- tion may further comprise that the home agent executes the step of generating the general control message based on the response message received from the service control means. Furthermore it may comprise the step of sending the general control message to the mobile node and/or to the at least one correspondent node.

In a preferred embodiment the method for service control in a telecommunication connection may comprise that the general control message may contain at least the address of the cor^¬ respondent node and/or the address of the mobile node.

Preferably, in the method for service control in a telecommu- nication connection the generation of the general control message by the home agent to the mobile node and/or to the correspondent node may be independent of external events. That is, the general control message is preferably generated by the home agent after consulting the service control means. In another embodiment of the present invention the telecommu^¬ nication network may send a message to the home agent which leads to the generation of the general control message by the home agent. Furthermore the home agent may generate the gen^¬ eral control message as soon as an event occurs.

A home agent being associated to a telecommunication network may be configured for intervening in the data exchange be^¬ tween the mobile node and the correspondent node. The home agent may be furthermore capable of generating a general con- trol message for supporting and/or refusing services between to the mobile node and/or the at least one correspondent node .

In a preferred embodiment the home agent may further comprise means for intercepting a first message sent by the mobile node or the at least one correspondent node. The home agent may further comprise means for selecting a filter from a list of filters. The home agent may further comprise means for filtering the first message received from the mobile node and/or the correspondent node by the filter selected by the home agent in view of matching the first message with a pre^¬ determined value or pattern provided by the selected filter. The home agent may further comprise means for selecting a trigger from a list of triggers based on the result of fil^¬ tering of the first message by the home agent.

Preferably, the home agent may further comprise means for sending the selected trigger to a service control means of a telecommunication network. The home agent may further comprise means for receiving a response message generated by the service control means indicating the result of processing the selected trigger by the service control means. The home agent may further comprise means for generating the general control message based on the response message received from the ser^¬ vice control means. The home agent may further comprise means for sending the general control message to the mobile node and/or to the at least one correspondent node.

In a service control means for use in a method according to the present invention the service control means may be con^¬ figured for receiving a trigger from the home agent . The service control means may be further configured for initiating and/or supporting a service between the mobile node and the correspondent node. The service control means may be further^¬ more configured for generating a response message indicating the service initiated and/or supported between the mobile node and the correspondent node.

Preferably, a system may comprise a home agent and a service control means, wherein the service control means and the home agent may be integrated in one device.

In another preferred embodiment the service control means for use in a telecommunication system may be a remote unit for the home agent . A telecommunication system may be configured for supporting data intervening between a mobile node and a correspondent node, wherein the system may comprise at least one home agent and/or a service control means.

A mobile node for use in a telecommunication network may be configured for receiving and/or processing the general control messages sent by the home agent.

Preferably, the method may comprise the step of encrypting the messages exchanged between the mobile node, the home agent and the correspondent node.

Preferred embodiments and further details of the present in- vention will be explained in the following with reference to the figures. In the following description, for purposes of explanation and not limitation, specific details are set forth, such as particular embodiments, circuits, signal for^¬ mats, techniques, etc. in order to provide a thorough under- standing of the present invention. Although specific proto^¬ cols are referred to for purposes of facilitating the de^¬ scription, the present invention is not necessarily limited to such specific protocols. Moreover, although the example described refers to Mobile IPv6, the present invention may be used with IP addresses that conform to other versions of IP. Therefore it will be apparent to one skilled in the art that the present invention may be practiced in other embodiments that depart from these specific details. In other instances, detailed description of well-known methods, devices and cir- cuits are omitted so as not to obscure the description of the present invention with unnecessary detail.

BRIEF DESCRIPTION OF THE DRAWINGS

Fig. 1 shows two modes of communication in Mobile IPv6. Fig. 2 shows the process of correspondent registration in Mo^¬ bile IPv6.

Fig. 3 shows the process of selective route optimization as one embodiment of the present invention.

Fig. 4 shows one embodiment of selective route optimization for 3GPP networks according to the invention.

Fig. 5 shows one example of message flow for selective route optimization in 3GPP networks according to the invention.

Fig. 6 shows one embodiment of the structure of a Home Test Init Refused message for selective route optimization accord^¬ ing to the invention.

Fig. 7 shows one example of message flow for failed passive selective route optimization according to the invention.

Fig. 8 shows one embodiment of the structure of a Binding Ad^¬ vice message for active selective route optimization accord^¬ ing to the invention.

Fig. 9 shows one example of message flow for active selective route optimization according to the invention.

Fig. 10 shows one embodiment of a correspondent registration cache according to the invention.

DETAILED DESCRIPTION OF EMBODIMENTS OF THE INVENTION Fig. 1 shows two modes of communication that are supported in Mobile IPv6 according to the state of the art. There are two ways to handle packet forwarding between correspondent nodes and mobile nodes, route optimization and bidirectional tun^¬ nelling mode. Each of these registration types leads to a different type of service for mobile node communications.

In route optimization all traffic is exchanged directly be^¬ tween a mobile node 2 and a correspondent node 3 in both di^¬ rections. When correspondent registrations are not supported, a home agent 1 is deployed as an intermediary in the communi^¬ cation between the mobile node 2 and the correspondent node 3. In Mobile IPv6 the home agent 1 has no control on the choice of communication mode used between the mobile node 2 and the correspondent node 3. The setup of Fig. 1 shows a situation in which the mobile node 2 is in a visited network that is not connected to his home network. The correspondent node 3 can be part of the visited network or can be located and connected to any other network being different from the home network and the visited network.

Fig. 2 shows the process of correspondent registration in Mo- bile IPv6. Before the process of correspondent registration will be described the features and functions of the involved messages are explained.

HoTI (Home Test Init) Message: When a mobile node 2 wants to perform route optimization it sends a HoTI Message to the correspondent node 3 in order to initiate the return routability verification for the home ad^¬ dress. This message tells the mobile node's home address to the correspondent node 3. The mobile node 2 also sends along a cookie CO (not shown) that the correspondent node 3 must return later, along with the nonce index (an index of numbers use once) and a token that it generates based on the home ad^¬ dress. The HoTI message is reverse tunnelled through the home agent 1. HoT (Home Test) Message:

When the correspondent node 3 receives the HoTI message, it generates a token KO (not shown) and sends it to the mobile node 2 via the home agent 1; it is an assumption of the pro^¬ tocol that the home agent 1 - mobile node 2 HoT/HoTI signal^¬ ling is encrypted. Token KO acts as a challenge to test that the mobile node 2 can receive messages sent to its home ad^¬ dress. A security key (not shown) and a nonce are used in the production of token KO in order to allow the correspondent node 3 to verify that the tokens used later really came from itself, without forcing the correspondent node 3 to remember a list of all tokens it has handed out. Cookie CO from the mobile node 2 is returned as well in the HoT message, to en- sure that the message comes from someone on the path towards the correspondent node 3.

CoTI (Care-of Test Init) Message:

When the mobile node 2 wants to perform route optimization it sends a CoTI message to the correspondent node 3 in order to initiate the return routablility verification for the care-of address. This message can be sent in parallel with HoTI mes^¬ sage. A CoTi tells the correspondent node 3 the mobile node's care-of address. The mobile node 2 also sends along cookie Cl (not shown) that the correspondent node 3 must return later, along with the token that it generates based on the care-of address. The CoTi message is sent directly to the correspon^¬ dent node 3.

CoT (Care-of Test) Message:

This message is sent in response to a CoTI message. When the correspondent node 3 receives the CoTI message, it generates a token Kl (not shown) and sends it to the mobile node 2. Cookie Cl (not shown) from the mobile node 2 is returned as well, to ensure that the message comes from someone on the path towards the correspondent node 3.

BU (Binding Update) Message: When the mobile node 2 has received both the HoT and CoT it has the tokens and nonce indices necessary to authenticate the Binding Update. The mobile node 2 hashes together the challenges to form a session key (not shown) , and then uses this session key to authenticate a Binding Update.

Once the correspondent node 3 has verified the Binding Up^¬ date, it can create a binding cache entry for the mobile node 2.

Binding Acknowledgement (BA) Message:

The correspondent node 3 optionally acknowledges the Binding Update. It uses the same key to authenticate a Binding Ac^¬ knowledgement .

Correspondent registrations are initiated by the mobile node 2. In base Mobile IPv6, a correspondent registration consists of two main functions, namely the Return Routability Proce^¬ dure (RRP) and the actual registration between the mobile node 2 and the correspondent node 3. The latter may only take place once the RRP has successfully completed.

RRP enables the correspondent node 3 to verify whether the mobile node 2 is reachable at its CoA as well as at its HoA.

A mobile node 2 initiates RRP by transmitting to the corre- spondent node 3 two messages, namely the HoTI and CoTI at the same time .

Since the correspondent node 3 is generally unaware of move^¬ ment of the mobile node 2, packets continue to be forwarded from the correspondent node 3 to the mobile node' s care-of address via the home agent 1. As a result, packets are routed inefficiently. In order to optimize the route via which pack^¬ ets are routed from the correspondent node 3 to the mobile node 2, it is desirable to enable the correspondent node 3 to communicate directly with the mobile node.

The CoTI is send directly to the correspondent node 3 convey^¬ ing the CoA of the mobile node 2. In parallel, the mobile node 2 transmits a HoTI message to the correspondent node 3 via reverse tunneling. That is, the HoTI message is tunnelled from the mobile node 2 to the home agent 1, where it is de- capsulated. The home agent 1 creates a binding cache entry and a tunnel established between the mobile node' s care-of address and the home agent 1. Mobile IPv6 defines that a home agent 1 may only accept reverse tunnelled traffic from mobile nodes 2 maintaining a valid registration with the home agent 1. When a correspondent node 3 sends a packet to the mobile node 2, it is forwarded to the mobile node 2 by the home agent 1 via the tunnel that has been established. The mobile node 2 then sends a Binding Update message to the home agent 1. The home agent 1 then sends a Binding Acknowledgement mes^¬ sage to the mobile node 2. The Binding Update and Binding Ac^¬ knowledgement messages are protected in IPSec transport mode.

Fig. 3 shows the process of selective route optimization as one embodiment of the present invention. In the following the HoTIR message corresponds to the general control message ac^¬ cording to the claims. The HOTI or CoTI message corresponds to the first message according to the claims. The policy de^¬ cision point corresponds to the service control means accord^¬ ing to the claims. The invention specifies for a network- controlled selective route optimization two mechanisms for controlling the mode of mobile node communications, namely passive and active selective route optimization:

- Passive selective route optimization is based on frequent correspondent registrations initiated by the mobile node 2.

Mobile IPv6 requires mobile nodes to renew a correspondent registration every time that a mobile node relocates or at least every 7 minutes. At these intervals, the home agent 1 may reassess the mode of communication used for each corre- spondent node 3.

- Active selective route optimization defines new signaling that is send from the home agent 1 to a mobile node and ex^¬ plicitly dictates the mode of communication to be used for communications with a correspondent node as well as the dura- tion of this directive.

A possible use case in a "pure Internet environment" may be derived from Figure 1 meaning that the depicted modified home agent 1 has now the means to control route optimization se- lectively per mobile node/correspondent node pair. The modi^¬ fication is due to the support of the proposed mechanisms for network-controlled selective route optimization. The follow^¬ ing use case illustrates an example of the operation of the network-controlled passive selective route optimization.

A mobile node 2 is roaming away from the home network and into a foreign network infrastructure that provides no bill^¬ ing or tarrifing facilities. The mobile node 2 is trying to establish communications with two correspondent nodes, namely correspondent node A 3 and correspondent node B 4. All commu^¬ nications with correspondent node B 4 are free of charge while there is a charge for all communications with corre^¬ spondent node A 3. The home network operator uses selective route optimization to provide the best possible service to the mobile node 2 while at the same time preserving the ser^¬ vice agreement maintained with the mobile node 2.

Initially, the mobile node 2 attempts to perform a correspon- dent registration by initiating a RRP with correspondent node A 3. The HoTI message is intercepted by the home agent 1 and the CML determines that the mobile node 2 should not pursuit route optimization in its communications with the correspondent node A 3. For this reason, a Home Test Init Refused (HoTIR) message is sent to the mobile node 2. After that, all communications between the mobile node 2 and the correspon^¬ dent node A 3 will use the home agent 1 as an intermediate. The home agent 1 may terminate service to the mobile node 2 at any required time.

At some further time, the same mobile node 2 determines that it wishes to communicate with correspondent node B 4. Such a connection is considered free of charge. On receipt of the HoTI at the home agent 1 the CML determines that route opti- mization is authorized for this communication and the corre^¬ spondent registration is allowed to complete.

Passive selective route optimization was used in this exam^¬ ple. The same type of behaviour can be reproduced with the help of active selective route optimization.

Fig. 4 shows one embodiment of selective route optimization for 3GPP networks according to the invention. Considering a use case in a "3GPP environment" it has to be first-of-all motivated why standard route optimization and the proposed extensions are relevant for future 3GPP networks. Internet applications and mobile Web seems to be the drivers for fu^¬ ture (mobile) telecommunication networks. Consequently it is foreseen with this invention that sophisticated IETF mecha- nisms like route optimization are necessary for network operators to cope with future challenges. Network operators are forced to apply efficient resource management mechanisms where appropriate. Route optimization is one of these mecha- nisms and the invention proposes to add the aspect of net^¬ work-control. IP Multimedia Subsystems (IMS) won't help op^¬ erators to deliver mobile Web services; hence, network layer solutions may address parts of the described problem space. Therefore, leaving the motivation thread, a potential network deployment can be as follows:

In this use case the user equipment (UE) 10 attaches to a trusted non-3GPP access network and host based mobility man^¬ agement mechanisms are used. Relevant in the context of this invention is the interface S2c 11 that can be described as

"It provides the user plane with related control and mobility support between user equipment and the gateway. This refer^¬ ence point is implemented over trusted and/or untrusted non- 3GPP Access and/or 3GPP access." According to terms defined in Mobile IPv6, the functional entities terminating both the control and user planes are denoted mobile node 2 in the user equipment 10, and home agent 1 in a gateway.

The interface S2c 11 has to be extended according to the de^¬ tails from this invention. The message flow for a successful authorization may look as follows (non-roaming case) :

Before correspondent registration is performed the user equipment 10 shall be authenticated and authorized to get IP connectivity through the trusted access network and a local IP address from the access network domain shall be assigned to the user equipment 10. This local IP address is used by the user equipment 10 during the security association estab^¬ lishment of step 1.

1) A security association is established between user equipment 10 and Packet Data Network gateway 12 to secure the Mobile IP messages between user equipment 10 and Packet Data Network gateway 12. The user equipment 10 initiates the es^¬ tablishment of the security association. The Packet Data Net^¬ work gateway 12 may communicate with the AAA infrastructure during this step.

2a) The user equipment 10 sends the HoTI message to the Packet Data Network gateway 12.

2b) In parallel the user equipment 10 sends also the CoTI message to the correspondent node 3. 3) The Packet Data Network gateway 12 processes the HoTI message received from the user equipment 10. During the proc^¬ essing the Packet Data Network gateway 12 performs authenti^¬ cation and authorization of the user based on the information received from AAA infrastructure; this step includes a policy decision point (PDP) evaluation that is here foreseen as being part of HSS/AAA (PDP may also be part of Packet Data Net^¬ work gateway 12 or be a separate network entity.) . Depending on the outcome of the evaluation the Packet Data Network gateway 12 sends HoTI to the correspondent node 3 (successful route optimization authorization, depicted in the figure with "3a") or HoTIR back the user equipment 10 (failed route opti^¬ mization authorization, not shown in the figure) . 3a) In case of successful route optimization authorization Packet Data Network gateway 12 sends a HoTI message to corre- spondent node 3 (see step 3) .

4a/b) The RRP is finalized with correspondent node 3 respond^¬ ing with HoT or CoT, respectively. 5, 6) The correspondent registration is finalized with Bind^¬ ing Update/Binding Acknowledge signaling between mobile node 2 and correspondent node 3.

As a result of the above steps the route optimized IP connec^¬ tivity is established. Only the successful authorization for selective route optimization is shown here; the application of the two proposed mechanisms for network-controlled selec^¬ tive route optimization can be applied accordingly.

The necessary modifications (in the 3GPP network) for net^¬ work-controlled selective route optimization can be summa^¬ rized as follows:

- Extension of interface S2c 11 * New messages HoTIR and Binding Advice

- Extension of Packet Data Network gateway 12 (hosting the home agent 1)

* To cope with the extended interfaces S2c 11 and to a policy decision point * Including now an extended Binding Cache to cope with new Correspondent Registration Cache (CRC) linked with the registered mobile node 2 (record of correspondent registra^¬ tions initiated by mobile node' s containing correspondent node's address, lifetime and a flag) .

Fig, 6 shows one embodiment of the structure of a HoTIR mes^¬ sage for selective route optimization according to the invention. The HoTIR message is sent by the home agent to the mo^¬ bile node indicating that RRP was obstructed for a specific correspondent node.

The HoTIR message uses the mobile node type value "5". When this value is indicated in the mobility header type field, the format of the Message Data field in the mobility header is as follows :

Reserved: 16-bit field reserved for future use. This value must be initialized to zero by the sender, and must be ig- nored by the receiver.

Home Init Cookie: 64-bit field which contains the home init cookie contained in the Home Test Init message. Target Node Addresses: Address of the correspondent nodes for which route optimization was obstructed. Mobility Options: If no actual options are present in this message, no padding is necessary and the Header Len field of the Mobility Header will be set to the value of one.

Fig. 7 shows one example of message flow for failed passive selective route optimization. The proposed method dictates that whenever, a HoTI message is intercepted by the home agent 1 a PDP (not shown) is consulted. The specification of the PDP is out of scope and only mentioned to have the full view on the procedure: If the PDP decides that route optimi- zation is not authorized for the given mobile node 2 and cor^¬ respondent node 3 pair, then a HoTIR message is sent to the mobile node 2 indicating the correspondent node 3 for which route optimization was not authorized.

Mobile IPv6 requires mobile nodes 2 to renew correspondent registrations every time that a mobile node 2 relocates or at least every 7 minutes. Passive selective route optimization dictates that at recurring correspondent registrations, the home agent 1 may reassess the mode of communication used for each correspondent node 3.

For the support of passive selective route optimization, the home agent 1 has to be able to detect reverse tunneled pack^¬ ets that contain a mobility header with a type value equal to one. This would identify the packets as HoTI messages. The filtering of HoTI messages at the home agent 1, for the sup^¬ port of passive selective route optimization, can take place at the same time as when reverse tunneled packets are checked for the validity of the registration of their source mobile node 2.

Information contained in the HoTI messages, such as the ad^¬ dresses of the mobile node 2 and the correspondent node 3 are forwarded to a decision engine (not shown) that determines whether route optimization is authorized for the particular node pair. If the authorization is successful, the decapsu- lated HoTI is forwarded to the correspondent node 3 as per normal RRP and the correspondent registration may resume.

The proposed method for passive selective route optimization defines that in case of a failed authorization the mobile node 2 is to pursuit route optimization with the particular correspondent node 3 then the home agent 1 issues the HoTIR message. HoTIR is a new type of message defined in the frame^¬ work of the proposed method that is send from the home agent 1 to the mobile node 2 when a HoTI message is rejected. The HoTIR message contains the address of the correspondent node 3 for which route optimization is not authorized. HoTIR is protected from the same security mechanisms foreseen in Mo^¬ bile IPv6 for the exchange of binding signaling between the mobile node 2 and the home agent 1.

Fig. 8 shows a structure of the Binding Advice message ac- cording to the present invention. In this embodiment the Binding Advice message corresponds to the general control message according to the claims. The proposed method defines a new type of message, namely the Binding Advice (BAd) mes^¬ sage that enables a home agent 1 to instruct a mobile node 2 to initiate a correspondent registration with a correspondent node 3. The Binding Advice message is protected from the same security mechanisms foreseen in Mobile IPv6 for the exchange of binding signaling between the mobile node 2 and the home agent 1. The Binding Advice message uses the mobility header type value "8". When this value is indicated in the mobility header type field, the format of the Message Data in the mo^¬ bility header is as follows: Lifetime: The recommended lifetime for the correspondent reg- istration with the indicated correspondent node(s) . A value of zero indicates that the home agent 1 is directing the mo^¬ bile node 2 to issue a Binding Update with a zero lifetime, which results in expiration of the binding. Target Node Address: One or more addresses of correspondent node(s) . Each address identifies a correspondent node with which the mobile node 2 should perform RRP and correspondent registration .

Mobility Options: This field contains zero or more mobility options. The only valid mobility option for this message is the HoA option used in this message in a different context other then that presented in base Mobile IPv6. The presence of a HoA option is used in cases where the mobile node 2 has several HoAs. It indicates the HoA that the mobile node 2 should use when communicating with the target node addresses.

A home agent 1 may issue Binding Advice messages only to mo^¬ bile nodes for which it maintains a registration. The home agent 1 can request from a mobile node 2 to perform a corre^¬ spondent registration with a correspondent node 3 not present in a Correspondent Registration Cache (CRC) (further details about the CRC will be explained in the description of Fig. 10) but it is expected that Binding Advice messages will con^¬ tain target nodes selected out of the CRC. A non-zero life^¬ time field value in a Binding Advice message indicates that the mobile node 2 should establish a binding with a corre^¬ spondent node 3. As a result all traffic between the mobile node 2 and the correspondent node 3 will enjoy route optimi^¬ zation. If the lifetime field value in the Binding Advice message is zero, then this will cause the mobile node 2 to delete the binding that it maintains with the defined corre^¬ spondent node 3. The result of this action will be that route optimization will be prevent for all traffic between the mobile node 2 and the correspondent node 3 using the home agent 1 as an intermediate.

Fig. 9 shows one example of message flow for active selective route optimization according to the invention. A binding is established at the correspondent node 3 and all traffic ex- changed uses route optimization. At some point in time a PDP (not shown) decides that route optimization should be allevi^¬ ated and the home agent 1 issues a Binding Advice message containing a zero lifetime field to the mobile node 2. This causes the mobile node 2 to remove its binding with the cor- respondent node 3 and to force all traffic to use the home agent 1 as an intermediate. At a further point in time, the PDP decides again that route optimization should be applied to communications between the mobile node 2 and the corre^¬ spondent node 3. A further Binding Advice message is send by the home agent 1 to the mobile node 2, this time, with a non^¬ zero lifetime field value. As a response, the mobile node 2 re-establishes a binding at the correspondent node 3 using again route optimization in their communications. The Binding Advice message can further comprise information relating to mobility options of the mobile node 2. Furthermore the Bind^¬ ing Advice message can be sent by the home agent 1 to the mo^¬ bile node 2 at any time. Fig. 10 shows one embodiment of a Correspondent Registration Cache 5 according to the invention. The proposed method of the present invention also assumes modifications to the Bind^¬ ing Cache conceptual data structure defined for home agents in Mobile IPv6. For the support of active selective route op^¬ timization the Binding Cache has to be extended to include information about the correspondent registrations initiated by every mobile node. For those that were authorized as well as those that were rejected. For every mobile node entry in a Binding Cache, the home agent 1 has to maintain a record of correspondent registrations initiated by the mobile node. This is the purpose of the CRC 5. There exists a different CRC for each registered mobile node and each CRC 5 is at^¬ tached to the respective mobile node entry in the Binding Cache. The sum of all the records of correspondent registra^¬ tion in the CRC 5 forms a list 6. The correspondent nodes of the list 6 in the CRC 5 are derived from previously received messages received from mobile nodes (not shown) . In another preferred embodiment the correspondent nodes of the list 6 in the CRC 5 are provided by a telecommunication network to which the home agent 1 is associated.

Every element of the CRC 5 contains the address of a corre^¬ spondent node, a lifetime and a flag. When the flag is set then the respective entry of the CRC 5 belongs to a failed correspondent registration. In that case the lifetime is set to the value of zero.

Entries in the CRC 5 age just as bindings in the Binding Cache do. If a binding expires and is removed from the Bind^¬ ing Cache so does the related CRC 5. If an entry in the CRC 5 expires (lifetime is zero) and its flag is not set then it is removed from the CRC 5. The maximum lifetime for a CRC 5 en^¬ try is defined equivalent to 7 minutes just like the maximum lifetime of a correspondent registration in Mobile IPv6. The Binding Advice message of Fig. 9 can indicate a correspondent node 3 for route optimization between the mobile node 2 and the correspondent node 3, wherein the correspondent node 3 is not present in the list 6 of correspondent nodes of the CRC 5.

An entry is introduced to the CRC 5 when the home agent 1 in^¬ tercepts a HoTI message from a mobile node or when a HoT is received at the home agent 1 from the correspondent node. In the latter case, the home agent 1 is ensured that RRP has completed successfully but filtering for HoT messages may in^¬ troduce more overhead to the home agent 1.

The specifications and drawings are to be regarded in an il^¬ lustrative rather than a restrictive sense. It is evident that various modifications and changes may be made thereto, without departing from the scope of the invention as set forth in the claims. It is possible to combine the features described in the embodiments in a modified way for providing additional embodiments that are optimized for a certain usage scenario. As far as such modifications are readily apparent for a person skilled in the art, these modifications shall be regarded as implicitly disclosed by the above described em- bodiments.

Claims

1. Method for service control in a telecommunication connec^¬ tion between a mobile node (2) and at least one correspondent node (3), the method being implemented in a home agent (1) associated to the mobile node (2) and the at least one corre^¬ spondent node (3) , the method being characterized in that the home agent (1) intervenes in the data exchange between the mobile node (2) and the at least one correspondent node (3) and generates a general control message (HoTIR, Binding Ad^¬ vice) to the mobile node (2) or to the at least one corre^¬ spondent node (3) for supporting or refusing services between the mobile node (2) and the at least one correspondent node (3) .

2. Method for service control in a telecommunication connec^¬ tion according to claim 1, characterized in that the home agent (1) further executes the steps of:

- intercepting a first message sent by the mobile node (2) or the at least one correspondent node (3) ,

- selecting a filter from a list of filters,

- filtering the first message received from the mobile node (2) or the correspondent node (3) by the filter selected by the home agent (1) in view of matching the first message with a predetermined value or pattern provided by the selected filter.

3. Method for service control in a telecommunication connec^¬ tion according to claim 2, characterized in that the home agent (1) executes the step of:

- selecting a trigger from a list of triggers based on the result of filtering of the first message by the home agent (D •

4. Method for service control in a telecommunication connec^¬ tion according to claim 3, characterized in that the home agent (1) further executes the steps of:

- sending the selected trigger to a service control means of a telecommunication network,

- receiving a response message generated by the service con^¬ trol means indicating the result of processing the selected trigger by the service control means.

5. Method for service control in a telecommunication connec^¬ tion according to at least one of the preceding claims, characterized in that the home agent (1) further executes the steps of:

- generating the general control message (HoTIR, Binding Ad^¬ vice) based on the response message received from the service control means,

- sending the general control message (HoTIR, Binding Advice) to the mobile node (2) or to the at least one correspondent node (3) .

6. The method for service control in a telecommunication con^¬ nection according to at least one of the preceding claims, characterized in that the general control message contains at least the address of said correspondent node (3) or the ad^¬ dress of the mobile node (2) .

7. The method for service control in a telecommunication con- nection according to claim 5 or 6, characterized in that the generation of the general control message (HoTIR, Binding Ad^¬ vice) by the home agent (1) to the mobile node (2) or to the correspondent node (3) is independent of external events.

8. A home agent (1) being associated to a telecommunication network, characterized in that the home agent (1) is config^¬ ured for intervening in the data exchange between the mobile node (2) and the correspondent node (3), wherein the home agent (1) is capable of generating a general control message (HoTIR, Binding Advice) for supporting or refusing services between to the mobile node (2) and the at least one corre^¬ spondent node (3) .

9. The home agent according to claim 8, characterized by fur^¬ ther comprising: - means for intercepting a first message sent by the mobile node (2) or the at least one correspondent node (3),

- means for selecting a filter from a list of filters,

- means for filtering the first message received from the mo^¬ bile node (2) or the correspondent node (3) by the filter se- lected by the home agent (1) in view of matching the first message with a predetermined value or pattern provided by the selected filter and

- means for selecting a trigger from a list of triggers based on the result of filtering of the first message by the home agent (1) .

10. The home agent according to claim 9, characterized by further comprising:

- means for sending the selected trigger to a service control means of a telecommunication network,

- means for receiving a response message generated by the service control means indicating the result of processing the selected trigger by the service control means, - means for generating the general control message (HoTIR, Binding Advice) based on the response message received from the service control means and

- means for sending the general control message to the mobile node (2) or to the at least one correspondent node (3) .

11. The service control means for use in a method according to at least one of the claims 2-7, characterized in that the service control means is configured for receiving a trigger from the home agent (1) and further configured for initiating or supporting a service between the mobile node (2) and the correspondent node (3) and is further configured for generat^¬ ing a response message indicating the service initiated or supported between the mobile node (2) and the correspondent node (3) .

12. A system comprising a home agent (1) according to one of the claims 8-10 and a service control means according to claim 11, characterized in that the service control means and the home agent (1) are integrated in one device.

13. A telecommunication system configured for supporting data intervening between a mobile node (2) and a correspondent node (3), the system comprising at least one home agent (1) according to claim 9 and a service control means according to claim 10.

14. A mobile node for use in a telecommunication network according to claim 13, characterized in that the mobile node (2) is configured for receiving and processing the general control messages (HoTIR, Binding Advice) sent by the home agent (1) .