WO2009003578A1

WO2009003578A1 - Method, system and access point for supporting network based mobility

Info

Publication number: WO2009003578A1
Application number: PCT/EP2008/004823
Authority: WO
Inventors: Telemaco Melia; Patrick Stupar
Original assignee: Nec Europe Ltd.
Priority date: 2007-07-02
Filing date: 2008-06-16
Publication date: 2009-01-08

Abstract

A method for supporting network based mobility, preferably in Proxy Mobile IP (PMIP) or in NetLMM architectures, wherein communication nodes (MN) attach to a network via Points of Attachment (PoA), wherein the association between a communication node (MN) and a Point of Attachment (PoA) includes the step of granting authorization by an AAA framework, is characterized in that said Points of Attachment (PoA), after having completed the authorization procedure with the AAA framework, generate a trigger message, wherein said trigger message is forwarded to a mobility access gateway (MAG) and employed to initiate network- based mobility operation.

Description

METHOD, SYSTEM AND ACCESS POINT FOR SUPPORTING NETWORK BASED MOBILITY

The present invention relates to a method for supporting network based mobility, preferably in Proxy Mobile IP (PMIP) or in NetLMM architectures, wherein communication nodes attach to a network via Points of Attachment (PoA), wherein the association between a communication node and a Point of Attachment (PoA) includes the step of granting authorization by an AAA framework.

Furthermore, the present invention relates to a system for supporting network based mobility, comprising at least one Point of Attachment (PoA) being configured to allow for attachment of communication nodes to a network, an AAA framework being configured to authorize associations between a communication node and said at least one Point of Attachment (PoA), and one or more Mobility Access Gateways (MAG) being configured to send location update information regarding the communication node to a mobility anchor (LMA),

Finally, the present invention relates to an access point for supporting network based mobility, the access point being configured to allow for attachment of communication nodes to a network, and to communicate with an AAA framework for authorizing associations of communication nodes with the network.

The IETF Netlmm working group is currently specifying a method to support network based mobility. The upcoming standard relocates functionalities from the mobile terminals to the network, thus enabling network components to send location update messages, either upon network attachment or handover, to mobility anchors on behalf of the mobile nodes. It results in the design of more simplified mobile devices not requiring the support of traditional host based mobility protocols (e.g. Mobile IPv6).

The standard currently focuses on the specification of the protocol running between the defined network functionalities, namely the mobility access gateway and the mobility anchor. The first one, located in the access router (AR), is the entity in charge of detecting network attachment of communication nodes, e.g. mobile devices, and sending location updates to the mobility anchor, which is located in a router within the network. Upon reception of location updates, the mobility anchor creates a binding cache entry for each mobile device thus providing global reachability to peers in the Internet initiating data sessions with the host device. The mobility anchor is the entity receiving all the traffic destined to mobile devices and forwarding it towards the AR to which each mobile device is attached. This location info is contained and updated in a so-called Binding Cache entry.

Network-based mobility requires a controlled environment, i.e. a method verifying required information about a node profile (such as mobile node credentials) before letting it be attached to the network and exploit mobility services. To fulfil such requirement, an AAA (Authentication, Authorization, and Accounting) infrastructure is employed. In addition, AAA procedures are also used to retrieve mobile node information required by PMIP. Usually, AAA procedures involve only the mobile node itself and the layer 2 Point of Attachment (PoA). In such case, the detection of node attachment to the Access Router (AR) of the MAG is performed explicitly by means of IP signalling from the node to the AR and the procedure for mobile node MAG attachment detection is based on the standard neighbour discovery protocol (specified in RFC 2461 ) as depicted in Fig. 1. However, implementing network attachment detection at this layer causes large delays, which proves to be disadvantageous in many application scenarios.

It is therefore an object of the present invention to improve and further develop a method, a system and an access point of the initially described type for supporting network based mobility in such a way that the delay caused in connection with network attachment detection is reduced.

In accordance with the invention, the aforementioned object is accomplished by a method comprising the features of claim 1. According to this claim, such a method is characterized in that said Points of Attachment, after having completed the authorization procedure with the AAA framework, generate a trigger message, wherein said trigger message is forwarded to a mobility access gateway and employed to initiate network-based mobility operation. Furthermore, the aforementioned object is accomplished by a system comprising the features of independent claim 11. According to this claim, such a system is characterised in that said Points of Attachment are configured to generate a trigger message after having completed the authorization procedure with the AAA framework and forward said trigger message to a mobility access gateway, which is configured to employ said trigger message to initiate network-based mobility operation.

Finally, the aforementioned object is accomplished by an access point comprising the features of independent claim 14. According to this claim, such an access router is characterised in that the access point is further configured to generate a trigger message after having completed the authorization procedure with the AAA framework and forward said trigger message to a mobility access gateway, which is configured to employ said trigger message to initiate network-based mobility operation.

According to the invention it has first been recognized that the requirement of sending an IP broadcasted message over the air from the communication node to the mobility anchor it is associated with is critical with respect to handover latency. To reduce handover latency, the invention proposes the generation of a trigger message to trigger network-based mobility operation after a node has attached to a PoA in scenarios where node credentials and profile retrieval procedures are terminated in the PoA. The trigger message is sent to the AR by the PoA after association between the PoA and the mobile node has been completed (and hence authorization has been granted). By doing so, the procedure is built upon the interface between layer two and layer three. The invention, by using existing technologies, optimizes layer three network detection attachment by using layer two information in a technology independent manner. The invention can be broadly applied to any network-based mobility solution involving only layer three entities, e.g. NETLMM and Proxy_MIPv4 working in co-located CoA (Care of Address) mode with MPA (Mobility Proxy Agent) located in the AR.

The performance of the PoA according to the invention enables optimal link attachment detection, which can further be exploited to trigger the Proxy Mobile IP stack in the mobility anchor (AR) without requiring any AAA involvement of the MAG. The authentication procedure is kept confined to the PoA, while the mobility anchor is involved only in mobility support

According to a preferred embodiment the mobility access gateways send location update information regarding the attached communication node to a mobility anchor. Based on the information received from the mobility access gateways, it may be provided that the mobility anchors configure routing states for the communication node. More specifically, a proxy binding update message may be sent from the mobility anchor to the mobility access gateway where a proxy binding cache is created. The creation of the proxy binding cache at the mobility access gateway may be acknowledged to the mobility anchor by way of an appropriate message.

Preferably, the trigger message is endowed with information related to the attached communication node. For instance, the communication node's identifier may be inserted into the trigger message as additional information. The communication node's identifier corresponds to the network access identifier (NAI) provided to the point of attachment by the mobile node during the authentication phase.

Additionally or alternatively, the mobility anchor's IP address may be inserted into the trigger message as additional information. Again, this information is owned by the point of attachment after the authentication phase and is retrieved from the AAA server.

According to a preferred embodiment the MIH_LINK_UP event message as defined in the IEEE 802.21 standard may be employed as a trigger message. It is to be noted that the MIH_Link_UP primitive specified in the 802.21 standard does not support yet the "nodelD" parameter. Thus, an insertion of the communication node's identifier into the MIH_LINK_UP event message requires an extension of that message. As regards a straightforward sending of the MIH_LINK_UP event, it may be provided that the mobility access gateway is subscribed to the LINKJJP event service with any point of attachment to which it is connected. With respect to a unique identification of the communication node, it may be provided that the communication node is identified by means of its MAC (Media Access Control) address within the trigger message.

There are several ways how to design and further develop the teaching of the present invention in an advantageous way. To this end, it is to be referred to the patent claims subordinate to patent claims 1 , 11 and 14 and to the following explanation of a preferred example of an embodiment of the invention, illustrated by the figure on the other hand. In connection with the explanation of the preferred example of an embodiment of the invention by the aid of the figure, generally preferred embodiments and further developments of the teaching will be explained. In the drawings:

Fig. 1 illustrates an example of a network configuration based upon PMIPv6 as network-based mobility solution according to the stat of the art, and

Fig. 2 illustrates an example of a system for supporting network based mobility according to an embodiment of the present invention.

Fig. 1 shows an example of a network configuration based upon PMIPvβ as network-based mobility solution and an AAA server providing node credentials and granting node attachment to the network.

The authentication procedure is performed between the AAA server and the PoA. After the PoA has received a MAG ASSOCIATION message from the mobile node MN (step 1 ), the PoA, in case of successful authentication, associates the MN with the network (steps 2 and 3) and sends a corresponding ASSOCIATED message to the MN (step 4). After having received this message, the MN sends a ROUTER SOLICITATION message to the MAG (step 5). In a next step, the proxy mobile IP handshake takes place, i.e. proxy binding update and proxy binding acknowledgement messages are exchanged between the MAG and the corresponding LMA (steps 6 and 7). Finally, the MAG sends a ROUTER ADVERTISEMENT message to the MN for address configuration (step 8).

It is important to note that the detection of MN attachment to the access router (AR) is performed explicitly by means of IP signalling from the MN to the AR. Such implementation causes large delays with respect to network attachment detection and consequently with respect to handover performance.

Fig. 2 illustrates schematically an example of a system for supporting network based mobility according to an embodiment of the present invention. The network architecture is the same as in Fig. 1 and like references are used for like components. The specific embodiment shown in Fig. 2 involves the IEEE 802.21 standard and builds up on the interface between layer two and layer three. The IEEE 802.21 WG is currently specifying a standard for enhancing handover procedures across heterogeneous access including 802.x family of networks, 3GPP and 3GPP2 networks. To help mobility decision functions (located both in the terminal and in the network) the standard proposes the deployment of three different services, namely Event Services (ES), Command Services (CS) and Information Services (IS). Event Services consist on a set of messages and primitives enabling 802.21 aware or MIH (Media Independent Handover) enabled entities to be informed when layer 2 events happen.

According to the embodiment of Fig. 2, the MIH_LINK_UP event message, which is endowed with additional parameters related to the attached mobile node MN, is used to trigger PMIP after the MN has attached to the Point of Attachment PoA. Again, as in Fig. 1 , the situation shown in Fig. 2 relates to a scenario where AAA procedures are terminated in the PoA.

More specifically, the MIH_Link_UP event message is sent to the MAG by the PoA after association between the PoA and the MN has been completed (and hence authorization has been granted by AAA framework). To get this message sent easily, the 802.21 module of the MAG is preferably subscribed to link_up event with any PoA to which it is connected. For instance, the subscription operation can be done at installation phase when PoA and AR/MAG get connected for the first time. Through the subscription, every time that a PoA detects a communication node associated (and hence authenticated by AAA framework) to it, a MIH_Link_UP event message is sent to the MAG by the PoA itself. 802.21 standard content of this message uniquely identifies the new attached node by using its MAC address.

Additional information, which is processed by PMIP, is inserted in the MIH_LINK_UP message: the identifier of the mobile node MN and the IP address of the mobility anchor LMA. Both data are owned by PoA after the authentication phase: the first one is the network access identifier (NAI) provided by the MN and the second is retrieved from the AAA server.

In the following the single steps of the method are described in some more detail. In a first step (1) the MN triggers the MN's profile retrieval procedure, i.e. the association authentication procedure, which is a standard MAC layer based procedure, and provides its NAI (used as node identifier NodelD). Next, the PoA, which functions as network access server (NAS), communicates with the AAA infrastructure to learn about the profile of the MN (2). In this context, it is checked whether the MN is allowed to connect to the network, and the IP address of the mobility anchor LMA assigned to the MN is retrieved. In the following steps (3) and (4), the MN's association with the PoA is established.

In the next step (5), the PoA sends message the MIH_Link_UP message to the MAG (AR) to trigger the Proxy Mobile IP stack. The MIH_Link_UP message contains the "nodelD", which is used in the Proxy Mobile IP stack to control location and/or registration update, and the LMA address. If the mobility anchor LMA is a static information owned by the PoA (i.e. not linked to MN's profile), steps (3), (4) and (5) can be performed concurrently.

In steps (6) and (7) the Proxy Mobile IP handshake takes place and the Mobile Node MN is registered in the network. More specifically, the mobility access gateway MAG sends a Proxy Binding Update PBU to the mobility anchor LMA₁ and the mobility anchor LMA sends a Proxy Binding Acknowledgement to the mobility access gateway MAG after a binding cache has been created at the mobility anchor LMA. Finally, in step (8) the MAG sends a router advertisement to the MN for address configuration, i.e. the MAG sets up IP plane on the link towards the MN. It is to be noted that the last step (8) can be performed concurrently with steps (6) and (7) independently from the way mobility anchor address is provided.

In the embodiment illustrated in Fig, 2, the MN does not need to send any Router Solicitation and as soon as the authentication procedure is completed the network triggers Proxy Mobile IP. The mapping in the PoA (done upon authentication) is secured and prevents mobile devices to send fake messages for network attachment, thus avoiding DoS (Denial of Service) attacks. The Router Advertisement is sent in unsolicited mode, enabling the mobile node to configure a routable IPv6 address, or, in case of handover, to update layer 3 information and keep on exchanging IP traffic. It should also be noted that the fact that the MIH_Link_UP message contains a technology independent nodelD helps the mobility platform to not depend on MAC identifiers. It derives that the described technology enables integration of homogeneous as well as heterogeneous deployments (e.g. handover from a MAG offering WLAN access to a MAG offering WiMax access is possible without changes in the technology) and does not depend on the AAA protocols.

The approach performed at the PoA (in the case considered in connection with the embodiment of Fig. 2 the NAS) enables optimal link attachment detection, further exploited to trigger the Proxy Mobile IP stack in the MAG (AR) without requiring any AAA involvement of the MAG. It aims at avoiding the requirement of sending an IP broadcasted message over the air and, hence, at the reduction of handover latency. This optimization does not require any modification to the involved terminals, neither that such terminals implement 802.21 functions, which must be implemented by PoAs and ARs.

Many modifications and other embodiments of the invention set forth herein will come to mind the one skilled in the art to which the invention pertains having the benefit of the teachings presented in the foregoing description and the associated drawings. Therefore, it is to be understood that the invention is not to be limited to the specific embodiments disclosed and that modifications and other embodiments are intended to be included within the scope of the appended claims. Although specific terms are employed herein, they are used in a generic and descriptive sense only and not for purposes of limitation.

Claims

C l a i m s

1. Method for supporting network based mobility, preferably in Proxy Mobile IP (PMIP) or in NetLMM architectures, wherein communication nodes (MN) attach to a network via Points of Attachment (PoA), wherein the association between a communication node (MN) and a Point of Attachment (PoA) includes the step of granting authorization by an AAA framework, c h a r a c t e r i z e d i n that said Points of Attachment (PoA), after having completed the authorization procedure with the AAA framework, generate a trigger message, wherein said trigger message is forwarded to a mobility access gateway (MAG) and employed to initiate network-based mobility operation.

2. Method according to claim 1 , wherein the mobility access gateways (MAG) send location update information regarding the communication node (MN) to a mobility anchor (LMA).

3. Method according to claim 2, wherein the mobility anchors (LMA), based on the information received from said mobility access gateways (MAG), set up routing states for the communication node (MN).

4. Method according to any of claims 1 to 3, wherein said network-based mobility operation includes proxy binding updates at a mobility anchor (LMA).

5. Method according to any of claims 1 to 4, wherein said trigger message is endowed with information related to the attached communication node (MN).

6. Method according to any of claims 1 to 5, wherein the communication node's (MN) network access identifier (NAI) is inserted into said trigger message as additional information.

7. Method according to any of claims 1 to 6, wherein the mobility anchor's (LMA) IP address is inserted into said trigger message as additional information.

8. Method according to any of claims 1 to 7, wherein the M I HJJ NKJJP event message as defined in IEEE 802.21 standard is employed as said trigger message.

9. Method according to any of claims 1 to 8, wherein said mobility access gateway (MAG) is subscribed to the link_up event service with any Point of Attachment (PoA) to which it is connected.

10. Method according to any of claims 1 to 9, wherein the attached communication node (MN) is uniquely identified within the trigger message by means of its MAC (Media Access Control) address.

11. System for supporting network based mobility, preferably in Proxy Mobile IP (PMIP) or in NetLMM architectures, comprising at least one Point of Attachment (PoA) being configured to allow for attachment of communication nodes (MN) to a network, an AAA framework being configured to authorize associations between a communication node and said at least one Point of Attachment (PoA), and one or more mobility access gateways (MAG) being configured to send location update information regarding the communication node (MN) to a mobility anchor (LMA), c h a r a c t e r i z e d i n that said Points of Attachment (PoA) are configured to generate a trigger message after having completed the authorization procedure with the AAA framework and forward said trigger message to a mobility access gateway (MAG), which is configured to employ said trigger message to initiate network-based mobility operation.

12. System according to claim 11 , wherein the mobility anchors (LMA) are configured to set up routing states for the communication node (MN) based on the information received from said mobility access gateways (MAG).

13. System according to claim 11 or 12, wherein said network-based mobility operation includes proxy binding updates at a mobility anchor (LMA).

14. Access point for supporting network based mobility, preferably in Proxy Mobile IP (PMIP) or in NetLMM architectures, the access point being configured to allow for attachment of communication nodes (MN) to a network, and to communicate with an AAA framework for authorizing associations of communication nodes (MN) with the network, c h a r a c t e r i z e d i n that the access point is further configured to generate a trigger message after having completed the authorization procedure with the AAA framework and forward said trigger message to a mobility access gateway (MAG), which is configured to employ said trigger message to initiate network-based mobility operation.

15. Access point according to claim 14, wherein said network-based mobility operation includes proxy binding updates at a mobility anchor (LMA).

16. Access point according to claim 14 or 15, wherein said trigger message is endowed with information related to the attached communication node (MN).

17. Access point according to any of claims 14 to 16, wherein the communication node's (MN) network access identifier (NAI) is inserted into said trigger message as additional information.

18. Access point according to any of claims 14 to 17, wherein the mobility anchor's (LMA) IP address is inserted into said trigger message as additional information.

19. Access point according to any of claims 14 to 18, wherein the MIHJJNKJJP event message as defined in IEEE 802.21 standard is employed as said trigger message.