Abstract:
A method is proposed, for use e.g. in the context of WiMAX networks supporting the CMIPv6 function, for allowing the ASN-GW to become aware of the status of a control procedure, the CMIPv6 mobility binding procedure. The ASN-GW is not directly aware of its result since the procedure implies a message exchange at the U-Plane level, where the ASN-GW implements only a routing function. Nevertheless the ASN-GW needs to know the status of the procedure since it has to perform some subsequent actions depending on that status. The method includes signalling the status via a signalling mechanism between the Access Service Network and the Connectivity Service Network, thus avoiding packet inspection at the U-plane by the Access Service Network Gateway.

Description:
FIELD OF THE INVENTION 
       [0001]    This disclosure relates to communication networks such as WiMAX (Worldwide Interoperability for Microwave Access) networks. 
         [0002]    This disclosure was devised by paying specific attention to its possible use in networks supporting the CMIPv6 (Client Mobile IP version 6) function introduced as part of the Release 1.0 of the WiMAX Forum specification. 
       DESCRIPTION OF THE RELATED ART 
       [0003]    In CMIPv6 R3 mobility binding is between a Mobile Station (MS) and a Home Agent (HA) and is handled via messages at the U-Plane level. Then only the MS and the HA are aware of BU (Binding Update)/BA (Binding Acknowledgement) status. A problem arises as to how the ASN becomes aware of the CMIPv6 binding state. 
         [0004]    At present, in WiMAX networks supporting CMIPv6, the only possible way to solve this problem is ASN-GW (Access Service Network Gateway) packet inspection: ASN-GW does not know if the MS actually sent BU and if the BA has indicated success, unless it performs packet inspection in the U-Plane. 
         [0005]    Then, in the currently adopted WiMAX solution, ASN-GW has to passively parse each U-Plane message to gain awareness of the status of BU/BA, both during Network Initiated R3 Re-Anchoring and Network Initiated Graceful Termination. 
         [0006]      FIGS. 1 and 2  are chronograms representative of these procedures as described e.g. in 
         [0007]    WIMAX End-to-End Network Systems Architecture 
         [0000]    Stage 2: Architecture Tenets, Reference Model and Reference Points—release 1.0.0—Mar. 28, 2007; and 
         [0008]    WIMAX End-to-End Network Systems Architecture 
         [0000]    Stage 3: Architecture Tenets, Reference Model and Reference Points—release 1.0.0—Mar. 28, 2007 
         [0009]    Specifically,  FIG. 1  is representative of a CMIPv6 mobility event triggering a network-initiated R3 re-anchoring event. 
         [0010]    The following reference numerals apply:
         100  Mobile Station     102  Base Station     104  Intra Access Service Network (ASN) Functional Entity     106  Target Data Path Function (DPF)     108  Target Access Router (AR)     110  Serving Data Path Function     112  Serving Access Router (AR)     114  Home Agent (HA)     116  New Care-of Address (CoA).       
 
         [0020]    The following events/transactions are effected in sequence:
         1000  Old ASN Data Path Function information exchanged between Base Station  102  and serving DPF  110       1002  Anchor DPF relocate request sent from Entity  104  to Target AR  108       1004  Router Advertisement sent from Target AR  108  to Mobile Station  100  to produce the new CoA  116       1006  Binding Update (BU) sent from Mobile Station  100  with new CoA  116  to Home Agent  114       1008  Binding Acknowledgement (BA) sent back from home Agent  114  to Mobile Station  100       1010  passive parsing of BU/BA at Target AR  108       1012  Anchor DPF Relocate Response sent from Target AR  108  to Entity  104       1014  Relocate CNF (Configuration—File Name Extension) sent from Entity  104  to Target AR  108       1016  ASN Data Path information exchanged between Base Station  102  and Target DPF  106       1018  base station  102  and Serving DPF  110  proceed to removing old ASN Data Path Function.       
 
         [0031]      FIG. 2  is representative of a CMIPv6 network-initiated “graceful” termination. 
         [0032]    The following reference numerals apply:
         100  Mobile Station     114  Home Agent (HA)     118  Access Router     120  Access Router Data Path (DP).       
 
         [0037]    The following events/transactions are effected in sequence:
         1020  R3 session release request sent from Access router DP  120  to Access Router  118       1022  Mobility Advertisement (with lifetime=0) sent from Access Router  118  to Mobile Station  100       1024  Binding Update (with lifetime=0) sent from Mobile Station  100  to Home Agent  114       1026  Binding Acknowledgement (with lifetime=0) sent from Home Agent  114  to Mobile Station  100 .     1028  Passive parsing of BU/BA at Access Router  118       1030  R3 session release reply sent from Access Router  118  to Access Router DP  120 .       
 
         [0044]    In the scenario portrayed in  FIGS. 1 and 2  the Access Service Network Gateway (ASN-GW) has to be aware of this binding status for several reasons, for example in order to start the release of the R4 tunnel between the Serving and Target ASN-GWs. 
       OBJECT AND SUMMARY OF THE INVENTION 
       [0045]    The preceding description of the related art indicates that the need is felt for improved solutions enabling a communication network, such as e.g. a WiMAX network, to become aware of the status of a procedure to be performed therein by avoiding the shortcomings of the procedures discusses in the foregoing. Exemplary of this situation is making an ASN-GW (Access Service Network Gateway) aware of BU (Binding Update)/BA (Binding Acknowledgement) status by avoiding ASN-GW packet inspection in the U-Plane. 
         [0046]    The object of the invention is thus to provide a satisfactory response to that need. 
         [0047]    According to the present invention, such an object is achieved by means of a method having the features set forth in the claims that follow. 
         [0048]    The invention also relates to a corresponding network, and to devices for use therein as well as to related computer program product, loadable in the memory of at least one computer and including software code portions for performing the steps of the method of the invention when the product is run on a computer. As used herein, reference to such a computer program product is intended to be equivalent to reference to a computer-readable medium containing instructions for controlling a computer system to coordinate the performance of the method of the invention. Reference to “at least one computer” is evidently intended to highlight the possibility for the present invention to be implemented in a distributed/modular fashion. 
         [0049]    The claims are an integral part of the disclosure of the invention provided herein. 
         [0050]    An embodiment of the arrangement described herein is thus a mechanism that allows a network to become aware of the status of a procedure, making use of a newly defined signalling mechanism. 
         [0051]    An embodiment applies to WiMAX networks, in particular to networks supporting CMIPv6. 
         [0052]    An embodiment of the arrangement described herein allows an Access Service Network Gateway (ASN-GW) to become aware of BU(Binding Update)/BA (Binding Acknowledgement) status making use of signalling mechanisms between the Access Service Network (ASN) and the Connectivity Service Network (CSN). 
         [0053]    In an embodiment, the CSN sends specific signalling messages to ASN-GW, informing it of the success of the mobility binding procedure. 
         [0054]    In an embodiment, a Home Agent (HA) informs the Authentication, Authorization and Account (AAA) function (e.g. an AAA server), the AAA function informs the ASN-GW authenticator, the ASN-GW authenticator informs the new anchor ASN-GW Data Path Function (DPF) and the new anchor ASN-GW DPF informs the old anchor ASN-GW DPF; otherwise the ASN-GW authenticator informs the old anchor ASN-GW Data Path Function (DPF) and the old anchor ASN-GW Data Path Function (DPF) informs the new anchor ASN-GW DPF. 
         [0055]    In an embodiment, in the case of a network-initiated R3 Re-Anchoring procedure, once a new binding with HA is created (after a successful exchange of BU/BA messages), the HA shall send Accounting Request Stop/Start (i.e. Access Request) messages to the AAA (due to the modification of the ongoing mobility binding). After the response towards HA, AAA will send a RADIUS Disconnect Request message to the Authenticator GW asking for releasing all the needed resources. 
         [0056]    In an embodiment, in the case of CMIPv6 Network Initiated Graceful Termination, the MS sends a binding update with lifetime=0 to the HA. Upon the successful deletion of mobility binding with the MS, the Accounting Client in HA shall send an Accounting Request Stop message to the AAA. After the response towards HA, AAA will send a RADIUS Disconnect Request message to the Authenticator GW asking for releasing all the needed resources. 
         [0057]    Embodiments of the arrangement described herein are applicable to ASN and CSN in case of CIMv6 support. In particular, depending on the signalling method used, ASN-GW, HA and AAA may be involved in implementing the arrangement described herein. 
     
    
     
       BRIEF DESCRIPTION OF THE ANNEXED VIEWS 
         [0058]    The invention will now be described, by way of example only, with reference to the enclosed figures of drawing, wherein: 
           [0059]      FIGS. 1 and 2  have been already described in the foregoing; 
           [0060]      FIG. 3  is a chronogram representative of a CMIPv6 mobility event triggering a network-initiated R3 re-anchoring event according to the arrangement described herein; 
           [0061]      FIG. 4  is a chronogram representative of a CMIPv6 network-initiated graceful termination according to the arrangement described herein; and 
           [0062]      FIG. 5  is generally representative of a signalling mechanism according to the arrangement described herein. 
       
    
    
     DETAILED DESCRIPTION OF PREFERRED EMBODIMENTS 
       [0063]    In the following description, numerous specific details are given to provide a thorough understanding of embodiments. The embodiments can be practiced without one or more of the specific details, or with other methods, components, materials, etc. In other instances, well-known structures, materials, or operations are not shown or described in detail to avoid obscuring aspects of the embodiments. 
         [0064]    Reference throughout this specification to “one embodiment” or “an embodiment” means that a particular feature, structure, or characteristic described in connection with the embodiment is included in at least one embodiment. Thus, the appearances of the phrases “in one embodiment” or “in an embodiment” in various places throughout this specification are not necessarily all referring to the same embodiment. Furthermore, the particular features, structures, or characteristics may be combined in any suitable manner in one or more embodiments. 
         [0065]    The headings provided herein are for convenience only and do not interpret the scope or meaning of the embodiments. 
         [0066]    The following is a list of acronyms used throughout this description with an explanation of the respective meanings. These meanings (and the meaning of any other acronym appearing in this description) are otherwise well known to those of skilled in the art. 
         [0067]    This list is provided solely by way of immediate reference.
   AAA Authentication, Authorization and Accounting   Acct Accounting   ACK ACKnowledge   ASN Access Service Network   ASN-GW Access Service Network Gateway   BA Binding Acknowledgement   BU Binding Update   CMIPv6 Client Mobile IP version 6   CSN Connectivity Service Network   DPF Data Path Function   GW GateWay   HA Home Agent   ID IDentifier   IPv6 Internet Protocol version 6   MS Mobile Station   NACK Not ACK   RADIUS Remote Access Dial-In User Service   WiMAX Worldwide Interoperability for Microwave Access   
 
         [0086]    Throughout  FIGS. 3 to 5 , parts, elements, and/or entities identical or equivalent to parts, elements, and/or entities already described in connection with  FIGS. 1 and 2  are indicated with the same reference numerals already appearing in  FIGS. 1 and 2 . Conversely, events/transactions depicted in  FIGS. 3 to 5  are indicated by way of orderly description with new reference numerals even though certain events/transactions as depicted in  FIGS. 3 to 5  may in fact be identical or equivalent events/transactions depicted in  FIGS. 1 and 2 . 
         [0087]      FIG. 3  is representative of an exemplary CMIPv6 mobility event triggering a network-initiated R3 re-anchoring event according to the arrangement described herein. 
         [0088]    The following reference numerals apply:
         100  Mobile Station     102  Base Station     104  Intra Access Service Network (ASN) Functional Entity     114  Home Agent (HA)     116  New Care-of Address (CoA).     200  Target ASN-GW Access Router (AR)/DPF     202  Serving ASN-GW Access Router (AR)/DPF     204  ASN-GW authenticator     206  Authentication, Authorization and Accounting (AAA) function (e.g. AAA server).       
 
         [0098]    The following events/transactions are effected in sequence:
         2000  Old ASN Data Path Function information exchanged between Base Station  102  and serving ASN-GW/DPF  110       2002  Anchor DPF HO (Hand-Over) Trigger sent from Entity  104  to serving ASN-GW AR/DPF  202       2004  Anchor DPF HO (Hand-Over) Request sent from serving ASN-GW AR/DPF  202  to Target ASN-GW AR/DPF  200       2006  Router Advertisement sent from serving ASN-GW AR/DPF  202  to Mobile Station  100  to produce the new CoA  116       2008  Binding Update (BU) sent from Mobile Station  100  with new CoA  116  to Home Agent  114       2010  Binding Acknowledgement (BA) sent back from Home Agent  114  to Mobile Station  100       2012  RADIUS Accounting Stop Request sent from Home Agent  114  to AAA  206       2014  RADIUS Accounting Stop Response sent from AAA  206  to Home Agent  114       2016  RADIUS Accounting Start Request sent from Home Agent  114  to AAA  206       2018  RADIUS Accounting Start Response sent from AAA  206  to Home Agent  114       2020  RADIUS Disconnect Request sent from AAA  206  to ASN-GW authenticator  204       2022  RADIUS Disconnect ACK sent from ASN-GW authenticator  204  to AAA  206       2024  Mobility binding success Indication sent from ASN-GW authenticator  204  to Target ASN-GW AR/DPF  200       2026  Mobility binding success Confirmation sent from Target ASN-GW AR/DPF  200  to ASN-GW authenticator  204       2028  Anchor DPF HO Response sent from Target ASN-GW AR/DPF  200  to serving ASN-GW/DPF  202       2030  ASN Data Path information exchanged between Base Station  102  and Target ASN-GW AR/DPF  200       2030  Base Station  102  and Serving ASN-GW AR/DPF  204  proceed to removing old ASN Data Path Function.       
 
         [0116]    Those of skill in the art will appreciate that the chronogram of  FIG. 3  and all the chronograms described herein are an illustrative (i.e. not mandatory) schematic representation of a sequence of steps/operations. 
         [0000]    Just to make an example, the Anchor DPF HO Request step  2004  preceding the Router Advertisement step  2006  of  FIG. 3  may in fact involve an Anchor DPF HO Request being sent first from the Authenticator ASN-GW HO to the Serving ASN-GW HO and in turn from the Serving ASN-GW HO to the Target ASN-GW HO, followed by a trigger being sent from the Target ASN-GW HO to the Target ASN-GW AR. As a further example, the RADIUS messages  2012 - 2018  may be replaced by an Access Request message sent from sent from Home Agent  114  to AAA  206  and by an Access Accept message sent from AAA  206  to HA  104 . Also, the Mobility binding success Indication/Confirmation messages  2024 - 2026  can take the form of a “Context_rpt” message sent by the Authenticator to the serving ASN-GW, which message is then forwarded to the target ASN-GW. The exemplary names attributed to the messages within the framework of this description are for convenience and ease of description and understanding only and do not interpret the scope or meaning of the embodiments. 
         [0117]    Along the same lines,  FIG. 4  is representative of an exemplary CMIPv6 network-initiated “graceful” termination according to the arrangement described herein. 
         [0118]    The following reference numerals apply:
         100  Mobile Station     114  Home Agent (HA)     118  Access Router     120  Access Router Data Path (DP).     204  ASN-GW authenticator     206  Authentication, Authorization and Accounting (AAA).       
 
         [0125]    The following events/transactions are effected in sequence:
         2100  R3 session release request sent from Access router DP  120  to Access Router  118       2102  Mobility Advertisement (with lifetime=0) sent from Access Router  118  to Mobile Station  100       2104  Binding Update (with lifetime=0) sent from Mobile Station  100  to Home Agent  114       2106  Binding Acknowledgement (with lifetime=0) sent from Home Agent  114  to Mobile Station  100       2108  RADIUS Accounting Stop Request sent from Home Agent  114  to AAA  206       2110  RADIUS Accounting Stop Response sent from AAA  206  to Home Agent  114       2112  RADIUS Disconnect Request sent from AAA  206  to ASN-GW authenticator  204       2114  RADIUS Disconnect ACK sent from ASN-GW authenticator  204  to AAA  206       2116  Mobility binding success Indication sent from ASN-GW authenticator  204  to Access Router  118       2118  Mobility binding success Confirmation sent from Access Router  118  to ASN-GW authenticator  204       2120  R3 session release reply sent from Access Router  118  to Access Router DP  120 .       
 
         [0137]      FIG. 5  is a higher level, generalized representation of the signalling mechanism between Access Service Network (ASN) and Connectivity Service 
         [0138]    Network (CSN) as described herein. 
         [0139]    The following reference numerals apply:
         100  Mobile Station     102  Base Station BS     114  Home Agent (HA)     206  Authentication, Authorization and Accounting (AAA)     208  Access Service Network Gateway (ASN-GW)       
 
         [0145]    Reference numerals  3000  and  3002  are representative of Binding Update (BU) information sent from the Mobile Station  100  to the home Agent  114  and Binding Acknowledgement (BA) information sent from the home Agent  114  to the Mobile Station  100 , respectively. 
         [0146]    The double arrow designated  3004  is generally representative of the new signalling mechanism as described herein. 
         [0147]    The arrangement described herein is thus representative of a mechanism allowing an ASN-GW to become aware of BU/BA status, making use of signalling mechanisms between ASN and CSN. One of the advantages is that this signalling mechanisms allow the ASN-GW to avoid parsing each U-Plane message, then saving extensive capacity resources. 
         [0148]    Still in compliance with the arrangement exemplified herein, different signalling flows could be used to solve this problem, the basic idea underlying this arrangement being to allow the CSN to send specific signalling messages to the ASN-GW, informing it of the success of the mobility binding procedure. 
         [0149]    An efficient embodiment is the one where the status of BU/BA exchange is realized in a circular way: the Home Agent (HA) informs the AAA (Authentication, Authorization and Accounting) function, the AAA function informs the ASN-GW authenticator, the ASN-GW authenticator informs the new anchor ASN-GW DPF and the new anchor ASN-GW DPF informs the old anchor ASN-GW DPF. 
         [0150]    So in this embodiment the problem is basically solved by signalling the status of BU/BA to ASN-GW authenticator through the AAA function. 
         [0151]    Following this approach in case of a Network Initiated R3 Re-Anchoring (as exemplified in  FIG. 3 ), once a new binding with the Home Agent (HA) is created (after a successful exchange of BU/BA messages), the HA shall send Accounting Request Stop/Start (i.e. Access Request) messages to the AAA function (due to the modification of the ongoing mobility binding). After the response towards HA, the AAA function will send a RADIUS Disconnect Request message to the Authenticator GW asking for releasing all the needed resources. 
         [0152]    Similarly, in case of CMIPv6 Network Initiated Graceful Termination (as exemplified in  FIG. 4 ), the MS sends a binding update with lifetime=0 to the HA. Upon the successful deletion of mobility binding with the MS, the Accounting Client in HA shall send an Accounting Request Stop message to the AAA. After the response towards HA, AAA will send a RADIUS Disconnect Request message to the Authenticator GW asking for releasing all the needed resources. 
         [0153]    The arrangement described herein would work even if the Home Agent does not really do accounting, since the function of accounting inside HA is an optional feature also in case of IPv6 support (HA could send just the STOP message as a trigger with AAA-Session-ID and some appropriate Acct-Terminate-Cause value). 
         [0154]    This RADIUS disconnect feature would use the existing format of RADIUS disconnect request and response messages. The code field used in disconnect messages would have three different codes: Disconnect-Request ( 40 ), Disconnect-ACK ( 41 ), Disconnect-NAK ( 42 ). For differentiating between the two different use cases reported above (R3 re-anchoring and graceful network exit) new RADIUS VSAs may be introduced to be used in the RADIUS Disconnect messages sent to the authenticator. Each RADIUS Client is already able to receive and to process unsolicited disconnect requests from RADIUS servers: the disconnect response will be either a Disconnect-ACK or a Disconnect-NAK, depending on the status of the disconnection procedure. 
         [0155]    Of course, other signalling methods may be possible. 
         [0156]    For instance, using “Access Request” messages between HA and AAA in the R3 re-anchoring procedure is enough for differentiating between R3 re-anchoring and graceful network exit. 
         [0157]    However the arrangement illustrated here, even if somewhat convoluted, is a complete circle and it appears as a clean solution. In addition it allows avoiding major impacts on the existing implementations. 
         [0158]    The arrangement described herein is applicable to ASN and CSN in case of CIMv6 support; in particular, depending on the signalling method used, ASN-GW, HA and AAA may be involved in implementing the invention. 
         [0159]    Without prejudice to the underlying principles of the invention, the details and the embodiments may vary, even appreciably, with reference to what has been described by way of example only, without departing from the scope of the invention as defined by the annexed claims.