Enhanced fast handover procedures

[0001] The invention relates to a method and system for switching a mobile device connection between two network access devices in a case where the global address of one or both of the network access devices involved in communication is not known to the mobile device performing the switch.

Background of the Invention [0002] The invention relates to mobile IP networks, in particular for performing switching or displacement from one access router to another access router. [0003] Document WO 01/28185 A1 discloses a method of providing mobility between IP-based networks in which, the method allows smooth switching between systems. Wide area network mobility is achieved by modifying existing protocols to include additional gateway addressing information.

[0004] The scope of the invention relates to optimized switching in the IP layer (i.e. optimization for Mobile IPv6) to ensure smooth session mobility. More specifically, the invention is most commonly used to achieve smooth session continuity during system to system switching or complementary IP access switching (e.g. smooth session continuity between WLAN and 3GPP system, described in 3GPP TR 22.934 "Study on the feasibility of interconnections from 3GPP system to a wireless local area network (WLAN)").

[0005] The IETF (Internet Engineering Task Force) association is making significant efforts to normalize mobile solutions for IP-based networks (Internet Protocol), such as the Mobile IP Protocol. The solution introduced by these standards can be supplemented with other mechanisms, also developed by IEFT to improve switching performance. To improve the performance of IP switches, for example, you can use the Fast Handover Internet Draft "draft-ietfmobileip-fast-mipv6-06.txt" in conjunction with the Mobile IPv6 protocol.

[0006] More detailed information on fast switching can be found, for example, in the following documents: "FAST HANDOVERS FOR MOBILE IPv6" EURESCOM Project participants P1113, Sebastien Auvray, France Telecom; "Fast switches and context transfers in cellular networks", Rajeev Koodli and Charles E. Perkins; and "Analysis of fast switching for the Mobile IPv6 protocol, Janne Lundberg, Helsinki University of Technology, Theoretical Computer Science Laboratory, May 28, 2003.

[0007] These solutions are designed independently of the underlying technology below the IP layer. Therefore, they can be used to implement IP switching between two access technologies, as long as both networks, the previous access network and the target access network use the IP protocol at the network layer.

A typical example is mobility between WLAN (wireless local area network) and GPRS (any packet transmission service by radio). However, some access technologies (such as GPRS) show some characteristics that can affect the functionality of IP switching, which will be explained later.

[0008] During a normal session, a Mobile Node (MN) is attached to an Access Router (ANG). The access router allows connecting to mobile nodes via IP and acts as the default router for the mobile nodes it currently supports. A supporting access router is also referred to as SAR (serving access router). An access router may include intelligence that goes beyond the simple forwarding service offered by ordinary IP routers. In the event that MN wants to make a switch, it usually has several access routers at its disposal to which it can switch. These access routers are referred to as Candidate Access Router (CAR).

[0009] The access router selected for switching is referred to as the Tanger Access Router. More specifically, TAR (Tanger Access Router) is an AR through which procedures are actually initiated for MN switching at the IP level. TAR is selected after running the TAR selection algorithm, which can take into account parameters such as CAR capabilities, MN preferences and any local operating principles. After switching, TAR becomes a (new) SAR.

[0010] After the switch has been made, the previous SAR to which the MN was previously attached is referred to as the previous access router (PAR), which is also occasionally referred to as the old access router (OAR) router). PAR is a (former) SAR that will stop or has already stopped offering MN the opportunity to connect to MN.

[0011] Typically, the MN is connected to the AR via an Access Point (AP). An access point is a second layer device connected to one or more than one access router. Access points are sometimes called base stations or access point transmitters / receivers. AP can be separate from AR or located together with AR.

[0012] In the fast handover procedure, the mobile node (MN) sends an F-BU (Fast Binding Update) message before moving to the TAR. When the PAR receives the F-BU message, it begins to forward incoming packets addressed to the MN towards TAR. F-BU is the last message sent by MN before it leaves PAR. MN can also send an F-BU message after moving to TAR (as the first message sent after moving) if it was not possible to send it before the move occurred.

[0013] The MN always knows the local IP address of the PAR link, as the MN can obtain this information from the router advertisement messages received from the PAR before moving. This information allows MN to send a F-BU message to PAR addressed to the local PAR link's IP address while MN is still connected to the PAR link. However, it cannot be assumed that MN always knows the publicly routable global unit IP address

PAR and therefore in cases where MN does not know the publicly routable global unit IP address of PAR, MN will not be able to send an F-BU message to PAR after it has moved to the target network because it will not be able to address actually F-BU (i.e. to the globally routable PAR IP address).

[0014] This scenario is always implemented when the MN needs to send the F-BU after moving to the target network and the previous access network is the GPRS network because the globally routable IP address of the GGSN (GPRS gateway support node) is completely unknown to the UE GPRS- u (it is assumed that for GPRS network the role of access router is performed by GGSN).

[0015] The "online working document on fast forwarding" assumes that MN knows the globally routable IP address of PAR. This assumption does not always apply, for example, it does not apply if the previous access technology is GPRS (and as a result PAR is GGSN). To date, no solution from the prior art is known.

[0016] The aforementioned problem - i.e. the fact that the globally routable addresses of the access routers participating in the switch are not known - affects the other details of the switch procedure.

[0017] Designed by (IETF) several protocols for smooth switching at the IP level, such as "Fast switching and context transfer". As these protocols establish IP signaling between the access router (AR) and the target access router (TAR), the requirement for this mechanism to work is that the TAR intended to switch the mobile node (MN) is known to the current AR (Fig. 1) . The TAR identification problem is being tested in IEFT Seamoby WG (working group

Seamoby IEFT) and was divided as follows:

- identification of neighboring ARs before switching (HO) occurs. This procedure is also known as finding an access router (CAR).

- TAR selection (from the CAR list) during switching (HO).

[0018] These mechanisms require that the TAR's IP address be known to the current AR in order for switching to be carried out. In some situations, this may be impossible / undesirable for one of the following reasons:

- The TAR is in a different administrative domain that wants to keep its internal address information confidential to other administrative domains.

- The TAR is in a private IP address domain (i.e., the TAR does not have a publicly routable IP address).

- TAR determination requires some technology-specific access procedures.

[0019] Therefore, in these cases it is not possible to make the transfer to TAR.

Summary of the invention [0020] Therefore, the object of the invention is to eliminate the abovementioned restrictions related to the characteristics of access technology according to the solutions known from the prior art and to enable switching even when the global address of one or both access devices to networks belonging to the networks participating in the switching does not is known to a mobile device, that performs the switch and / or other network access device involved in the switch.

There are two scenarios in which the invention applies:

1. the IP packet must be sent to a previous network access device whose global IP address is unknown to either the current network access device or the mobile device.

2. The IP packet must be sent to the target network access device whose IP address is unknown to the current network access device or mobile device.

[0021] The purpose of the first scenario is solved by a method for switching a mobile device connection from the first network access device from the first access network to the second network access device from the second access network in a fast, seamless switch between systems in which the global address of the first access device to the network is unknown to the mobile device, wherein the method comprises sending from the mobile device to the second network access device a message containing information for identifying the first network access device, which allows the second network access device to obtain the global address of the first network access device and to forward, based on the obtained global address, transmission packets for the first network access device.

[0022] Alternatively, the above goal is solved by a network system comprising at least one mobile device, a first network access device from the first access network and a second network access device from the second access network, in which the global address of the first network access device is unknown to the mobile device , while the network system is adapted to perform fast, smooth switching between systems, wherein the network device is adapted to send a message containing information to identify the first network access device to the second network access device, which allows the second network access device to obtain the global address of the first network access device and to redirect packet traffic to the first network access device based on the global address obtained.

In particular, the invention introduces a mechanism enabling a mobile node (MN) as an exemplary network device to engage in signaling (e.g. IP signaling) with its unconnected prior access router (PAR) as an exemplary first network access device , when the publicly routable global unit IP address of PAR is not known to MN. The functionality of the mobile node can be fulfilled by any mobile station, laptop, PDA equipment and the like.

[0024] An example in which such a mechanism is required is the provision of a Quick Binding Update (F-BU) message from the MN to the PAR in the Fast Switching Protocol if the PAR is GGSN. The solution of this invention is used in scenarios when the MN is to send the FBU to PAR after moving to the target network.

[0025] Accordingly, by using the mechanism of the invention, MN will be able to apply the fast switchover procedure when it performs IP switchover from GPRS to any other target network.

[0026] Furthermore, the publicly routable global unit IP address of GGSN in the GPRS network need not be disclosed to MN. [0027] The second network access device may identify whether the message received from the mobile device is directed to the first network access device by checking the address indicated in the message, and check whether the address is globally routable.

[0028] When checking the address - it can be assessed whether the address is globally routable or cannot be assessed by the address prefix.

[0029] The message may be a Fast Binding Update (F-BU) message.

[0030] A message containing information for identifying the first network access device may be sent before breaking the connection between the mobile device and the first network device. Optionally, a message containing information for identifying the first network access device may be sent after breaking the connection between the mobile device and the first network device.

[0031] If a message containing information for identifying the first network access device is sent prior to breaking the connection between the mobile device and the first network device, the second network access device may receive from the first network access device a message containing the global address of the first network access device.

[0032] The second network access device may include an address mapping table in which information for identifying the first network access device obtained from the mobile device is mapped to the global address of the first network access device.

[0033] The information for identifying the first network access device may include a link layer address of the mobile device.

[0034] Furthermore, a message containing all or part of the information for identifying the first network access device may be sent from the second network access device via an intermediate server in which the intermediate server determines the address of the first network access device.

[0035] The information for identifying the first network access device may include at least one of the following parameters:

former network identity (such as e.g. PLMN IP, IP identity in the network in an area served by one mobile operator), name of the former access point (e.g. name of the GPRS access point (APN), if the first access device to the network was GGSN) associated identity with an access point through which the mobile device was connected to the first network access device, and / or the link layer address of the network device.

[0036] Thanks to this, the globally routable address of the first network device is determined by the proxy server so that the global address does not have to be disclosed to the second network device or mobile device.

[0037] Thus, according to the invention, switching or other type of change of the mobile device connection between two network access devices can be made even if the address of one of the network access devices participating in the switch is either unknown or undesirable to be widely known . [0038] The proxy server may also be used to forward signaling (and other packet traffic on the network) between the second network access device and the first network access device.

[0039] The mobile device may monitor the network attributes of the first network access device in advance relative to the handover to obtain information for identifying the first network access device. [0040] The second network access device may determine the address of the appropriate proxy server based on the information contained in the information received to the mobile device to identify the first network access device.

[0041] In addition, the above purpose for the second scenario is solved by a method of performing a mobile device connection switch from the first network access device from the first access network to the second network access device from the second access network in a fast, smooth switch between systems in which the global address the second network access device is unknown to the mobile device, wherein the method comprises sending from the mobile device a message containing information for identifying the second network access device to the first network access device, which allows obtaining the global address of the second network access device and redirecting packet traffic to the second network access device based on the obtained global address .

[0042] In addition, the above goal is solved by a network system consisting of a mobile device, a first network access device from the first access network and a second network access device from the second access network, in which the global address of the second network access device is not known to the device mobile, while the network system is adapted to perform fast, smooth switching between systems and in which the mobile device is adapted to send a message to the first device to the next step to the network containing information for identifying the second device accessing the network, which message allows the first network access device to obtain the global address of the second network access device and to route packet traffic to the second network access device based on the obtained global address.

[0043] Furthermore, a message containing all or part of the information for identifying the second network access device may be sent to an intermediate server in which the intermediate server designates the address of the second network access device.

[0044] Due to this, the globally routable address of the second network device is determined by the proxy server not to disclose the global network address to the first network device or mobile device.

[0045] Thus, according to the invention, switching or other type of change of the mobile device connection between two network access devices can be made even if the address of one of the network access devices involved in the handover is not known or if it is undesirable to be widely known.

[0046] The proxy server may also be used to forward signaling (and other type of packet traffic) between the first network access device and the second network access device.

[0047] The mobile device may monitor the network attributes of the second network access device to obtain information for identifying the second network access device.

[0048] The first network access device may determine the proxy server address based on the information contained in the information received from the mobile device to identify the second network access device.

[0049] The first network access device may identify whether the message received from the mobile device is directed to the second network access device, checking the address indicated in the message and checking whether the address is globally routable.

[0050] in addition, when checking the address, it can be determined, based on the address prefix, whether the address is globally routable or not.

[0051] The message may be a handover initiation (HI) message.

[0052] The first network access device may include an address mapping table in which information for identifying the second network access device received from the mobile device is mapped to the global address of the second network access device. [0053] The information for identifying the second network access device may include at least one of the following parameters:

destination network identity (such as e.g. PLMN IP, network identity in an area served by one mobile operator), name of the destination access point (e.g. destination GPRS access point (APN) if the new connection is a GPRS connection), and / or an identity associated with the access point through which the mobile device will be connected to the second network access device.

BRIEF DESCRIPTION OF THE DRAWINGS [0054]

Fig. 1 shows the first scenario for a quick switch procedure,

Fig. 2 shows a second scenario for a quick handover procedure to which the first embodiment may apply.

Fig. 3 shows a third scenario for a fast handover procedure to which the first embodiment may apply.

Figures 4A and 4B show the general procedure for the solution according to the first embodiment.

Fig. 5 shows the signaling of switching between the current access router (AR) and the target access router (TAR) according to the state of the art.

Fig. 6 shows finding a TAR IP address according to a simple example according to the second embodiment.

Fig. 7 shows the finding of a TAR IP address based on the proxy server function of the target network according to the second embodiment.

Fig. 8 shows the TAR IP address signaling flow based on the proxy server function of the target network according to the second embodiment.

Fig. 9 shows the details of the signaling flow step S5 of Fig. 8.

Fig. 10 shows the security bindings required when using the solution without a proxy server according to the second embodiment,

Fig. 11 shows the security associations required when using the proxy server according to the second embodiment, and

Fig. 12 shows a combination of the first and second embodiments according to which the proxy is used to determine the global TAR address.

DESCRIPTION OF PREFERRED EMBODIMENTS [0055] Preferred embodiments are described below with reference to the accompanying drawings.

[0056] According to a first embodiment, the connection change (i.e., handover or displacement) of the mobile device from the first network access device to the second network access device is performed such that the mobile device sends a message containing information to identify the first network access device to the second network, which allows the second network device to obtain the global address of the first network device.

This means that if the global address of the first network access device is necessary to complete the switchover and the mobile device (e.g. Mobile IPv6 MN Mobile Node) does not know it, the mobile device sends known information associated with the first network access device , which is known to the device of the second network. Using this information, the second network device can obtain the global address of the first network access device, so that the handover or displacement procedure can be completed.

[0057] It should be noted that in the context of this application the term "global address" refers to an address that has a meaning in the network (destination access router as an example of a second network device) of the TAR (i.e. it is an address that can be used to reach PAR from TAR (previous access router as an example of a first network device)). This means that "global address" refers to an address that is globally known (or available) on the network. Conversely, the term "local address" refers to an address that is only available locally, ie only on part of the network. For example, in the current case, the local link address of the first network access device (e.g., PAR) can only be used on a mobile device that is on the same link.

[0058] The above procedure will be described in more detail below.

[0059] Fig. 1, Fig. 2 and Fig. 3 show the various scenarios of the quick switch procedure listed in the introductory part.

[0060] In these scenarios, it is assumed that the mobile node (MN) moves from the previous access router (PAR) as an exemplary first network access device to the destination access router (TAR) as an exemplary second network access device. It is assumed that PAR is located in subnet 1 - access network 1, and TAR is located in subnet 2 - access network 2. [0061] It should be noted that the figures do not show all the elements involved in the signaling. For example, APs (access points) are located between access routers and mobile network nodes.

[0062] Fig. 1.shows a scenario called the "predicted case" scenario. Here, it means that the fast switching procedure is initiated before the move. [0063] MN initiates the switch by sending a router selection message for the proxy (RtrSolPr) to PAR in message 11. This is a message from MN to PAR requesting information for a potential switch. PAR sends a Initialize Switch message (message 12, HI) to the TAR. In response to the HI message, TAR sends a HACK message (confirmation of switching) to PAR (message 13). After receiving a HACK message from TAR, PAR sends a proxy announcement router message to MN (message 14). Proxy server router advertisement (PrRtrAdv) is a message from PAR indicating to MN that it should switch.

[0064] Next, the MN sends a Fast Binding Update (F-BU) message to the PAR. The Fast Binding Update (F-BU) message is a message from MN instructing its PAR to redirect packet traffic towards NAR, i.e., TAR. This message is therefore important for completing the transfer.

[0065] After displacement, the MN sends a quick neighborhood message to the TAR. Quick Neighborhood Notification (FNA) is a message sent from MN to NAR (here TAR) to confirm the use of NCoA (the new address of the current connection to the network) if MN has not received a quick confirmation of the association (FBACK). That is, in the event that PAR did not send the FBACK message to MN because MN just moved to TAR. In response to the FNA 16 message, the TAR sends an FBACK message (message 17) to the MN. This message ends the quick switch procedure. [0066] It should be noted that the current network connection (CoA) address is the temporary address assigned to MN while he visits external networks. The base agent maintains a binding between the static MN base address and the current CoA.

[0067] Thanks to this, in the scenario 1 shown in Fig. 1, the MN sends the F-BU message 15 while it is still connected to the previous access network. Therefore, MN has no problem with sending the F-BU message to PAR because it is located on the same link as PAR. MN uses the PAR local link IP address to address the FBU to the PAR.

[0068] The second scenario is shown in Fig. 2. Messages 21 to 24 correspond to the messages up to 11 to 14 in Fig. 1. However, here the MN sends a F-BU (message 25) after moving to TAR- and. This message must, however, be directed to PAR, because PAR must be required to redirect MN packet traffic (packets addressed to the previous MN CoA) to TAR. Thus, the TAR is to forward the F-BU message to PAR in message 25. In the event that the MN does not know the PAR's globally routable IP address, the MN cannot address the F-BU message to the PAR properly unless the solution according to the present embodiment of the invention is used.

[0069] More specifically, as will be explained in detail later, to determine PAR's globally routable IP address, information is used which MN is additionally inserted into the F-BU message.

[0070] After sending the F-BU 25 message, the MN sends the FNA message (message 26) to the TAR, which responds with the FBACK message (message 27) to complete the quick switching procedure.

[0071] It should be noted that FNA is sent after the MN reaches the new access network. They are used to start delivering buffered packets from TAR to MN. F-BU starts forwarding packets from PAR to TAR. The TAR then caches packets until MN appears in the new access network. When MN arrives at TAR, sending FNA begins delivering buffered packets from TAR to MN.

[0072] Fig. 3 illustrates a scenario of the so-called "unforeseen case", i.e. a procedure of quick handover initiated after displacement.

[0073] This means that in this case the fast switching procedure starts by sending an F-BU message (message 31) from MN to TAR. The F-BU message is forwarded to the PAR as in the case of Fig. 2. Then, the PAR sends a HI message (message 32) to the TAR, and the TAR responds with a HACK message (message 33).

Then, to complete the quick switching procedure, the TAR sends an FBACK message (message 34) to MN.

[0074] In scenario 3, MN starts the quick switch procedure by sending an F-BU message after moving. In the event that the MN does not know the PAR's globally routable IP address, it cannot properly address the F-BU message to the PAR unless the solution according to the illustrated embodiment of the invention is used.

[0075] Figures 4A and 4B show the general procedure for the solution described in this invention.

[0076] The general requirement in the "foreseeable case" of the quick switching procedure implies that the so-called MN-LLA option (which carries the MN link layer identity, such as the MAC address) must be included in all RtrSolPr, HI and F-BU messages of the quick procedure switching. This will allow TAR to map MN-LLA through a globally routable PAR address, as described below.

[0077] MN-LLA is the MN-a address in the link layer, and in particular it is the address in the link layer of the MN-which is switched to the destination point. According to the above-mentioned "Internet working document on fast forwarding" ("draft-ietf-mobileip-fast-mipv606.txt") this option should be included to help the destination recognize the MN when it connects to the destination.

[0078] Figs. 4A and 4B show the proposed step-by-step procedure:

1. Two possible scenarios are considered, "anticipated case" and "unforeseen case" (as described in Fig. 2 and Fig. 3):

a) The "predicted handover" case (Fig. 4A): when the TAR receives an HI message, it maps the source IP address of the packet (publicly routable global unit PAR PAR address available from the TAR) in the MN-LLA contained in this message. This is a new feature according to the practical application for AR implementing the fast switching functionality.

b) Case of "unpredictable switching" (Fig. 4B): as described above with reference to Fig. 3, in the event that the F-BU message was not sent before the movement, MN sends the F-BU message to the PAR after the movement . This message is addressed to PAR at IP level, but the second layer frame (W2) is ultimately directed to the TAR interface (the next stage on the routing path). The MN shall contain the following information in the message:

• Destination Point Address (DA): local PAR link address (as specified in the above-mentioned quick switching work document) • Source Address (SA): MN_PCoA, i.e. the previous address of the current mobile node network connection (as specified in the above-mentioned document quick switching).

[0079] At this point, the NAR cannot forward the F-BU message to the PAR because the local link address is not globally routable and the NAR also does not know the PAR public public IP address.

[0080] Thus, according to the presented embodiment, it is proposed to include in the F-BU message some new parameters (marked as optional, since they are only useful for the case in which MN sends the F-BU after the displacement (the case of "unforeseen switching")) whose purpose is to enable the TAR to forward the F-BU message to the relevant PAR:

- former NET_ID: network identity of the previous access network.

- former APN_name | old AP_name: name (in GPRS) APN (access point name) or (in WLAN) AP (access point) to which MN was connected in the previous access network.

- MN_LLA: link layer address of the MN node.

[0081] The former network identity may be, for example, PLMN ID (IP identity in the network in an area served by one mobile operator).

[0082] Upon receipt of F-BU, the TAR checks the packet DA. It is learned that the destination IP address is the local IP address of the link (which has the prefix FE80), which does not belong to the TAR itself. Therefore, the TAR checks whether in the address mapping table created by mapping the publicly routable global IP address in MN_LLA there is a record for MN_LLA, which is contained by MN in F-BU (information received in the HI message, as described in step 1.a ) above):

a) In the case where there is a record for MN_LLA (i.e. TAR has just received the HI message) and PAR has disclosed its IP address, then the TAR obtains the associated PAR's IP address and passes the F-BU message straight to the PAR (in the transfer can be used IP encapsulation). This will apply to scenario 2 (anticipated case).

b) In the case where there is no record for MN_LLA, the TAR forwards the F-BU message to PAR, whose publicly routable global unit address is determined by the "former NET_ID" and "APN_name | former AP_name "included by MN in the F-BU message. The NAR may need the support of a node acting as a proxy server to be able to perform this mapping, which is described further in relation to the second embodiment of the invention. After the publicly routable global unit IP address of the PAR is determined, the F-BU message can be forwarded to the PAR (e.g. by IP-in-IP encapsulation). This will apply for scenario 3 (unforeseen case).

[0083] When modifying the first embodiment, a globally routable TAR address may occur that may be unknown to the MN node. This means that in this modification the roles of PAR and TAR with respect to determining the globally routable address are reversed.

[0084] The TAR address may be determined primarily as according to the first embodiment.

[0085] If the mapping according to the first embodiment is used, the PAR includes an address mapping table in which the information for identifying the TAR obtained from the MN is mapped to the global TAR address.

[0086] The second embodiment of the invention is described below. The second embodiment is directed to identifying the TAR.

[0087] As mentioned in the introductory part, the TAR identification mechanism requires that the current AR specify the IP address

TAR for MN node switching purposes. This is illustrated by the example of Fig. 5. Fig. 5 shows the basic interaction in the IP layer between the current AR and TAR. This means that signaling the IP switch between the current AR and the TAR requires that the current AR know the globally routable (public) IP address of the target AR. Note that TAR also needs a PAR address.

[0088] Fig. 6 is a high level diagram of finding the TAR IP address. In particular, the situation is presented in which the globally routable (public) IP address of TAR is not known to MN. The MN mobile node is connected to the current AR and wants to switch to the TAR (target AR). Fig. 6 shows that the corresponding access points are Layer 2 access points (e.g., WLAN APs). According to this example, a similar procedure is used as according to the first embodiment. This means that the MN provides information to the corresponding AR to identify another AR (in this case, the TAR). In particular, in step S61, the MN monitors the attributes (e.g., the target's WLAN AP MAC address) from the target network attachment point, which attributes will help identify the TAR IP address. At step S62, the attributes are disclosed to the current AR. At step S63, the current AR determines the TAR's IP address based on the attributes provided by the MN. Thus, at step S64, the current AR may send IP switch signaling to the correct TAR.

[0089] It should be noted that, at step S63, it requires the AR to have access to an address mapping table that maps layer 2 IDs (e.g., WLAN AP MAC addresses) to their corresponding AR IP addresses. However, this mapping will not work for GPRS because the cell ID will not always map to the same GGSN - depending on which access point name (APN) MN intends to access. In GPRS, APN is the logical name that assigns the currently connected access point to an external packet network according to the DNS naming convention. This refers to the fact that GGSN should be used.

[0090] As mentioned above, this requires the current AR to know the globally routable IP address of the TAR. In some situations, however, this may be impossible / undesirable for any of the following reasons:

- The TAR is in a different administrative domain that wants to keep its internal address information confidential to other administrative domains. For example, if the MN moves from WLAN to GPRS, the TAR will be GGSN in the GPRS network. If the WLAN is not administered by the GPRS operator (for example, WLAN is administered by the University and GPRS is administered by the Operator X), the GPRS operator (Operator X) most likely does not want to disclose its internal addressing (GGSN IP address) to the WLAN operator (University). Such information can be used, for example, to organize a DoS attack (denial of service) on GGSN. In addition, the GPRS operator may consider GGSN's address information to be confidential.

- The TAR is in the private IP address domain (i.e. the TAR does not have a publicly routable IP address). Another possibility may be that the TAR does not have a globally routable IP address. This IP address cannot therefore be used by the current AR for addressing the TAR (unless the current AR and TAR are in the same private address space).

- TAR determination requires certain access technology specific procedures.

[0091] In addition to the above, there are additional problems that are solved according to the second application example. The following are the most important problems:

- In switching between systems with WLAN to GPRS, the target GGSN of the MN node (TAR) will depend on the APN to which the MN will access. As a result, the mapping mechanism of the 2nd layer access point identifier in the TAR IP will not work. Because in GPRS the target GGSN depends on APN, AR WLAN would have to be aware of APN-to-GGSN mappings, which are usually maintained in the domain name server (DNS) in the GPRS operator's network.

- In some access networks, specifying the TAR IP address requires some network-specific functions

Revealing these features to other networks is highly undesirable. For example, designating a TAR in GPRS means identifying the destination GGSN's IP address. In GPRS, the target GGSN depends on the APN that the MN node wants to access. GPRS mapping in APN determined by the GPRS-enabled support node (SGSN) by querying the DNS server. And again - if the WLAN is not administered by the GPRS operator, the GPRS operator is very likely not to allow the WLAN operator to query the DNS server on its internal nodes. In addition, it would be desirable to maintain GPRS-specific details transparent to the WLAN. It would therefore be beneficial if the WLAN operator did not have to make access.

access point for any GPRS-specific activity to determine the IP address of the target GGSN.

[0092] According to a second embodiment of the practical invention, the function of an intermediate server between administrative domains is introduced to allow the current AR to perform the required IP signaling in the direction of TAR (e.g. signaling fast switchover or context transfer) without disclosing the TAR's IP address to the current AR- owi (fig. 6). In addition, the proxy server function hides any access-specific procedures required to specify the TAR IP address. As a result, from the perspective of the current access router, all target access networks will look the same. All specific access functions are performed by an intermediary server located in a specific access network. This is illustrated in Figure 7:

[0093] MN provides an information container containing specific access attributes about the target access network (step S72). Thanks to them, MN monitors attributes from the target network connection point, which in step S71 will help to identify the TAR IP address (e.g. PLMN ID of the target network). [0094] The current access router uses some of these attributes to identify the target access network and its corresponding proxy server, and passes the rest of the attributes transparently to the identified proxy server. In detail at step S73, the current AR designates the IP address of the target proxy server corresponding to the parameters of the attributes passed through the MN (e.g. PLMN ID), and in step S74 there is signaling of IP switching between the current AR and the proxy.

[0095] The proxy server then performs all the procedures specified for the target access network required to determine the IP address of the access router. The same node can also additionally pass through the proxy the entire IP signaling between the current and target access router, which means that the IP address of the destination access router is not disclosed to the current access router, which can be administered by another operator or MN . From the point of view of the current access router, everything will look as if it was communication directly with the target access router or more specifically - with the target access router that is in the same access technology.

[0096] In detail in step S75, the proxy server performs the access-specific function required for mapping the TAR's IP address. In the case of GPRS, this means a query to the DNS server (domain name server) based on APN. Then, in step S76, the intermediary server mediates the transfer of IP HO signaling (switching) between the current AR and TAR (which in the case of GPRS is GGSN). [0097] Thus, as shown in Fig. 7, the proxy device performs all the specified access functions required to determine the TAR IP address. The proxy server also hides the internal GPRS addressing from devices from the WLAN.

[0098] The procedure according to the presented embodiment of the invention will be described below in more detail with reference to the specific scenario of switching from WLAN to GPRS, as shown in Fig. 8. Fig. 8 shows the detection of TAR IP address signaling flow based on the proxy server function in the destination network. It should be noted that the "RtrSolPr" (router selection for proxy server), "HI" (initiate switchover) and HACK (switch confirmation) messages are also described in the first embodiment, and are also described, for example, in "Quick Switching for Mobile IPv6 "" Draft-ietf-mobileipfast-mipv6-06.txt. "

[0099] A prerequisite for the steps described below is that the current AR must have access to the "T" table, which maps identities from potential target networks (e.g. PLMN IDs) to the IP address of the corresponding proxy server (e.g. to signal to Operator Y the use of the proxy server IP address).

[0100] In step S1, the MN gathers the "A" attributes useful for identifying the point of attachment to the target network (e.g. PLMN ID + APN). This means that MN determines the information about its connection point to the target network, for example by monitoring broadcast channels (also known as cellular beacon in cell systems). The level of information that MN can determine depends on the terminal's capabilities and the type of target access network.

[0101] In step S2, the MN sends the identified parameters regarding the target GGSN to the current AR (i.e. to the WLAN AR). They can, for example, be placed in the "RtrSolPr" message in quick switches. MN may need to consider additional parameters required to identify the TAR. For GPRS, MN would have to disclose the access point name (APN) that MN applications will require, for example, when using GPRS access. In detail, an additional RtrSolPr option or a new destination option containing the 'A' attributes collected in step S1 may be added to the 'RtrSolPr' message.

[0102] In step S3, the current AR (in this example the WLAN AR) defines the target GPRS network (based on the parameters sent by the MN) and identifies the address of the corresponding proxy server from the list of available proxy servers (the WLAN operator maintains a list of potential target networks and their corresponding proxy servers in table "T" as described above). This means that WLAN AR uses some of the 'A' attributes (e.g. PLMN ID) to specify the target network and its corresponding proxy server.

[0103] In step S4, the MN sends a message intended for GGSNa (e.g., HI message in fast handovers) to the IP address of the identified proxy server from step S3. This message contains a destination point option containing parameters that can be used to identify the target GGSN (these are the same parameters that were transmitted by the MN in step S2). This means that MN sends the HI + message a new destination option containing the 'A' attributes copied from the 'RtrSolPr' message in step S2. [0104] In step S5, the proxy obtains information from the destination point options and determines the GGSN IP address corresponding to the parameters sent by the WLAN AR. For a specific case of switching from WLAN to GPRS, this can be done by querying the DNS server in the GPRS network, based on the APN contained in the message received by the proxy server. This is illustrated in Fig. 7 in step S75.

[0105] In addition, this is also illustrated in Fig. 9, which shows step S5 of Fig. 8 in more detail for the case in which the target network uses DNS to resolve the destination address of the access router. Specifically, in step S5a, the proxy sends a query to the DNS server for APN to DNS. In the event that DNS successfully determines the IP address, it sends to the proxy in step S5b a DNS response containing the TAR's IP address.

[0106] In step S6, the proxy relays the message received from the WLAN AR (excluding the destination option) to the identified GGSN. This message must include a new ID option that helps the proxy identify which WLAN AR it should send the corresponding reply to. To allow this, the AR must also maintain a temporary state that maps the WLAN AR's IP address (read from the source address of the incoming packet) in the ID of the message used in the message forwarded to GGSN. Alternatively, the message ID may be the same as the IP address of the WLAN AR, without the proxy having to maintain any state. Therefore, in step S6, the proxy sends a HI message (without the option of the destination point containing attributes) + the option of the new destination containing the IP address of the current AR obtains from the IP header of the message sent in step S4.

[0107] In step S7, the TAR (in this case, GGSN) receives the message and performs the necessary actions. GGSN sends a reply message to the proxy. The message must contain a copy of the Message ID option to help the proxy identify which WLAN AR to forward the message to. This means that the GGSN sends a message

HACK + destination option containing the current IP address

AR copied from the message sent in step S6.

[0108] In step S8, the proxy receives the response message, extracts the ID option message from it, and uses it to determine the target WLAN AR to which the response should be forwarded. The proxy then sends the reply message to the intended WLAN AR which sends the request message. This means that in step S8 the proxy sends a HACK message (without the destination point option) and determines the destination IP address based on the destination option contained in the message sent in step S7.

[0109] The effects of the second embodiment will be described below with respect to the required security associations.

[0110] Fig. 10 shows the security associations required for a "standard solution" in the event that no intermediate server such as according to the second embodiment will be used.

[0111] Generally, IP mobility signaling between access routers requires security links between access routers in order to protect IP mobility signaling. Fig. 10 shows that for "standard solutions" n is required² security associations for n geographically adjacent access routers. In the example shown in Fig. 10, 3 WLAN access routers (marked in Fig. 10 successively from WLAN AR # 1 to WLAN AR # 3) delimiting the region covered by coverage by 3 GGSNs (marked in Fig. 10 successively from GGSN # 1 to GGSN # 3), give a demand for 32 = 9 security associations (marked in Fig. 10 successively from SA # 1 to SA # 9). This leads to exponentially increasing complexity.

[0112] Fig. 11 shows the security associations required for the solution according to the second embodiment.

[0113] According to a second embodiment, a security binding is only required between the proxy server and each access router. It follows that for n geographically adjacent access routers it requires n security associations, which corresponds to linear complexity. In the example of Fig. 11, again, 3 WLAN access routers and 3 GGSNs are shown. Only 6 safety associations are required here.

[114] As a modification of the second embodiment, the reverse case can also be used, similar to the modification of the first embodiment.

[0115] The invention is not limited to the embodiments described above, but may vary within the scope of the claims.

[0116] For example, the above embodiments can be combined as desired.

[0117] In particular, the proxy server function described in the second embodiment may be used for the procedures of the first embodiment and according to the modification of the first embodiment.

[0118] Basically, in the case where there is no record for MN_LLA in the procedure according to the first embodiment as shown in Fig. 3 for example, the TAR further sends an F-BU message to PAR, whose publicly routable global unit address is determined by the "former NET_ID" and "APN_name | options former APN_name ”contained by MN in the F-BU message. In this case, the NAR may require the support of a node acting as an intermediary server in order to perform this mapping. This node may be a proxy server as described in the second embodiment.

[0119] This case is illustrated in Fig. 12. A situation similar to that in Fig. 3 (scenario 3) is shown, in which, however, a proxy server is used. In message 121 from MN the TB message is sent to the TAR containing the parameters described in the first embodiment. Unlike the first embodiment, the TAR does not attempt to find the PAR's globally routable IP address, but forwards the message to the proxy. Now the proxy server specifies the globally routable PAR IP address - if necessary, by querying the DNS server. After obtaining the address, the proxy sends the F-BU message to the PAR.

[0120] Next, the HI message (message 122) is also forwarded to the TAR via the proxy server, as well as the HACK message (message 123) is sent from the TAR to the PAR via the proxy server. This means that it is not necessary for the globally routable IP address of PAR to be known to TAR or MN. To complete the handover procedure, the FBACK message is sent to the MN in message 124, similar to, for example, message 34 of FIG.

3.

[0121] Furthermore, the invention and particularly the second embodiment focus on the implementation of the proxy server for the purposes of network cooperation between WLAN and

GPRS. However, the invention is not limited to this. The same principle can be applied between other access technologies or even within the same access technology when IP mobility signaling from the target access network to the current access network between different administrative domains is required without revealing any confidential addressing and without requiring specific access procedures.

[0122] The details given in the description of the first and second practical applications and modifications thereof indicate that all required options are "superimposed" (ie, transferred) to already existing signaling messages (specifically to fast switching messages). The information contained in these options can equally well be transmitted by other mechanisms, such as, for example, ICMP (Internet Control Message Protocol) options.

[0123] Details of the internal functions of the proxy server as described in the first and second embodiments and their modifications were specified for GPRS. This, however, does not limit the use of this invention for switching from WLAN to GPRS. If the target network is for example WLAN, the proxy server may maintain a table that maps the relevant WLAN AP MAC addresses to the corresponding IP address ARa.

[0124] The mobile node (MN) as an example of the mobile device of the above-described embodiments is only an example for a general network element. This means that the invention can be applied to any device that can perform a switch or change of connection between two network access devices.

[125] Particularly in this application, the term "mobile device" is used to designate any device that switches its IP connections from one network access device to another network access device. This change may be caused, but is not limited, for example, by the mobility of the mobile device, the end user's choice of the mobile device, or a trigger from the end of the network.

21255 / EP / 11

EP 1 645 157