Abstract:
A method and apparatus for dynamic home address assignment by a home agent in multiple network interworking. The invention provides a method and apparatus send a key authorization request from a mobile station to a network device, the request indicating that the mobile station wishes to use a foreign agent care-of address to continue to receive data. The network device assigns a temporary address to the mobile station and creates a security policy database for the mobile station. The mobile station receives agent advertisements from foreign agents that may be able to provide service. The mobile station registers with a foreign agent. The network device then modifies the security policy database to reflect the information of the foreign agent. The Home Agent then assigns a home address to the mobile station and the network device updates the security policy database to include only the mobile device&#39;s home address as a selector.

Description:
CROSS-REFERENCE TO RELATED APPLICATIONS 
       [0001]    This is a divisional application and claims the benefit of priority for U.S. patent application Ser. No. 11/840,735 filed Aug. 17, 2007. 
     
    
     FIELD OF THE INVENTION 
       [0002]    The present invention relates generally to communication systems, and more specifically, to a method and apparatus for interworking authorization of dual stack operation. 
       BACKGROUND 
       [0003]    Wireless communication technologies have seen tremendous growth in the last few years. This growth has been fueled in part by the freedom of movement offered by wireless technologies and the greatly improved quality of voice and data communications over the wireless medium. Improved quality of voice services along with the addition of data services have had and will continue to have a significant effect on the communicating public. The additional services include accessing the Internet using a mobile device while roaming. 
         [0004]    The ability to maintain a data session while moving is important to both users and system operators. As more users utilize mobile internet protocol operations a user may want to have simultaneous access to the same packet data interworking function using dual stack operation, which allows simultaneous use of two version of a mobile internet protocol. The packet data interworking function (PDIF) acts as a security gateway protecting the cellular network. 
         [0005]      FIG. 1  shows an interworking architecture for a wireless local area network (WLAN). The network may be part of a wireless communication system operating on the 3GPP2 standard defined by the standard offered by a consortium named “3rd Generation Partnership Project 2” referred to herein as 3GPP2, The architecture,  100 , includes a mobile station (MS),  102 , connected to a WLAN system,  104 . The WLAN system,  104  includes the Access Point (AP)  106 , and Access Router (AR)  108 . The WLAN system is connected to the 3G Home Network  110 . The WLAN system connects to the 3G Home Network  110  via the Packet Data Interworking Function (PDIF)  122 . The PDIF  114  is connected to the Home Authentication, Authorization, and Accounting (H-AAA) device  112 . 
         [0006]    The MS establishes a secure IP tunnel with the PDIF, which acts as a security gateway in the 3G Home Network. The tunnel establishment is authenticated and authorized by the H-AAA  112 . After the tunnel has been established, the MS may access services in the 3G Home Network  110 . The dashed line in  FIG. 1  indicates the path for Authentication, Authorization, and Accounting information and indicates information transfer between H-AAA  112  and PDIF  114 . The solid lines show the bearer path for user data traffic and the pipeline indicates the secure tunnel protecting the user data traffic between the MS  102  and the PDIF  114 . 
         [0007]    The MS is pre-configured with the PDIF address information, either an IP address or a Fully Qualified Domain Name (FQDN). If the MS is configured with the PDIF&#39;s FQDN, the MS will relay on the Domain Name System (DNS) to resolve the IP address associated with the FQDN. The MS uses Internet Key Exchange version 2 (IKEv2) to establish secure tunnels, known as IP-sec tunnels for data transfer, with the PIDF. Part of establishing a secure tunnel requires that the MS be authenticated and authorized by the H-AAA,  112  in  FIG. 1 . The MS may use a number of procedures for mutual authentication. The authentication information, including credentials and random challenges, are transported in Extensible Authentication Protocol (EAP) messages exchanged between the MS and H-AAA. The EAP messages are transported in the IKEv2 messages between the MS and the PDIF, and also in the RADIUS messages exchanged between the PDIF and H-AAA. 
         [0008]    The MS may desire simultaneous access to the same PDIF using both IPv4 and IPv6. This dual stack operation poses authorization problems for the PDIF, namely, the PDIF needs to know whether a MS is authorized for IPv4 and/or IPv6. Additionally, the PDIF needs to indicate to the MS that the MS is not authorized for one of the IP versions, in the case of an MS requesting dual stack operation that is not authorized for both IPv4 and IPv6. There is a need for a method and apparatus to indicate IP authorization to a MS and also to indicate to a MS that the MS is not authorized for both IP versions. 
       SUMMARY 
       [0009]    A method for dual stack authorization and operation in a communication system incorporating requesting authentication from an authorization entity in the communication system and then receiving an authentication message from the authorization entity if the authentication is successful, wherein the authentication message contains an authorization to use at least one internet protocol version to establish at least one secure tunnel for communication. 
         [0010]    A further embodiment provides for a method comprising: requesting dual stack operation using more than one internet protocol version; receiving authorization for dual stack operation using more than one internet protocol version; establishing a separate subordinate security authorization for each internet protocol version, wherein the subordinate security authorization is subordinate to the internet key exchange security authorization; establishing at least one secure tunnel for communication; and accessing simultaneously both internet protocol versions using the at least one secure tunnel for communication. 
         [0011]    Yet another embodiment provides a method comprising; requesting dual stack operation using more than one internet protocol version; receiving authorization for one internet protocol version in a message, wherein the message identifies at least one internet protocol version that is authorized and further wherein the message identifies at least one internet protocol version that is not authorized; establishing a security authorization for the authorized internet protocol version, wherein the security authorization for the authorized internet protocol version is subordinate to a internet key exchange security authorization; establishing a secure tunnel for communication; and communicating using the secure tunnel. 
         [0012]    Another embodiment provides for an apparatus composed of the following elements: a transmitter for requesting authentication from an authorization entity in a wireless communication system; and a receiver for receiving an authentication message from the authentication entity if the authentication is successful, wherein the authentication message contains an authorization to use at least one internet protocol version to establish at least one secure tunnel for communication. 
         [0013]    An additional embodiment provides for an apparatus composed of the following elements: a transmitter for requesting dual stack operation using more than one internet protocol version; a receiver for receiving authorization for dual stack operation using more than one internet protocol version; a memory for storing a separate subordinate security authorization for each internet protocol version, wherein the subordinate security authorization is subordinate to the internet key exchange security authorization; a processor for establishing at least one secure tunnel for communication using the transmitter; and a transmitter for accessing simultaneously more than one internet protocol versions using the at least one secure tunnel for communication. 
         [0014]    Yet another embodiment provides for an apparatus that includes the following elements: a transmitter for requesting dual stack operation using more than one internet protocol version; a receiver for receiving authorization for one internet protocol version in a message, wherein the message identifies at least one internet protocol version that is authorized and further wherein the message identifies at least one internet protocol version that is not authorized; a processor for establishing a security authorization for the authorized internet protocol version, wherein the security authorization for the authorized internet protocol version is subordinate to a internet key exchange security authorization; a memory for storing the security authorization for the authorized internet protocol version; a transmitter for establishing a secure tunnel for communication; and a transmitter for communicating using the secure tunnel. 
         [0015]    Another embodiment provides an apparatus composed of the following elements: means for requesting authentication from an authorization entity in a wireless communication system; and means for receiving an authentication message from the authorization entity if the authentication is successful, wherein the authentication message contains an authorization to use at least one internet protocol version to establish at least one secure tunnel for communication. 
         [0016]    An additional embodiment provides a method composed of the steps: means requesting dual stack operation using more than one internet protocol version; means for receiving authorization for dual stack operation using more than one internet protocol version; means for establishing a separate subordinate security authorization for each internet protocol version, wherein the subordinate security authorization is subordinate to the internet key exchange security authorization; means for establishing at least one secure tunnel for communication; and means for accessing simultaneously both internet protocol versions using the at least one secure tunnel for communication. 
         [0017]    A further embodiment provides an apparatus comprising; means for requesting dual stack operation using more than one internet protocol version; means for receiving authorization for one internet protocol version in a message, wherein the message identifies at least one internet protocol version that is authorized and further wherein the message identifies at least one internet protocol version that is not authorized; means for establishing a security authorization for the authorized internet protocol version, wherein the security authorization for the authorized internet protocol version is subordinate to a internet key exchange security authorization; means for establishing a secure tunnel for communication; and means for communicating using the secure tunnel. 
         [0018]    A computer program product embodiment is provided, comprising: a computer-readable medium comprising: instructions for causing a computer to request authentication from an authorization entity in a wireless communication system; and instructions for causing a computer to receive an authentication message from the authorization entity if the authentication is successful, wherein the authentication message contains an authorization to use at least one internet protocol version to establish at least one secure tunnel for communication. 
         [0019]    A further embodiment provides a computer program product comprising: a computer-readable medium comprising: instructions for causing a computer to request dual stack operation using more than one internet protocol version; instructions for causing a computer to receive authorization for dual stack operation using more than one internet protocol version; instructions for causing a computer to establish a separate subordinate security authorization for each internet protocol version, wherein the subordinate security authorization is subordinate to the internet key exchange security authorization; instructions for causing a computer to establish at least one secure tunnel for communication; and instructions for causing a computer to access simultaneously both internet protocol versions using the at least one secure tunnel for communication. 
         [0020]    An addition embodiment provides a computer program product comprising: a computer-readable medium comprising: instructions for causing a computer to request dual stack operation using more than one internet protocol version; instructions for causing a computer to receive authorization for one internet protocol version in a message, wherein the message identifies at least one internet protocol version that is authorized and further wherein the message identifies at least one internet protocol version that is not authorized; instructions for causing a computer to establish a security authorization for the authorized internet protocol version, wherein the security authorization for the authorized internet protocol version is subordinate to a internet key exchange security authorization; instructions for causing a computer to establish a secure tunnel for communication; and instructions for causing a computer to communicate using the secure tunnel. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0021]      FIG. 1  is a block diagram that shows an interworking architecture for supporting interworking authorization of dual stack operation according to an embodiment of the invention. 
           [0022]      FIG. 2  shows the contents of the CREATE_CHILD_SA request according to an embodiment of the invention. 
           [0023]      FIG. 3  shows the contents of the CREATE_CHILD_SA response according to an embodiment of the invention. 
           [0024]      FIG. 4A  shows IPsec Tunnel Establishment according to an embodiment of the invention. 
           [0025]      FIG. 4B  shows Tunnel Establishment Flow according to an embodiment of the invention. 
           [0026]      FIG. 5  shows the structure of the IP-Version-Authorized RADIUS VSA according to an embodiment of the invention. 
           [0027]      FIG. 6  illustrates a flow chart of authorized IPv4-IPv6 dual stack operation according to an embodiment of the invention. 
           [0028]      FIG. 7  illustrates a flow chart of operation when only IPv4 is authorized according to an embodiment of the invention. 
           [0029]      FIG. 8  illustrates a flow chart of operation when only IPv6 is authorized according to an embodiment of the invention. 
       
    
    
     DETAILED DESCRIPTION 
       [0030]    The word “exemplary” is used herein to mean “serving as an example, instance, or illustration”. Any embodiment described herein as “exemplary” is not necessarily to be construed as preferred or advantageous over other embodiments. 
         [0031]    A MS desiring access to packet data services needs to gain access to the IP access network. The MS initiates tunnel establishment as part of the access process. These tunnels are established between the MS and the PDIF and require several steps before a tunnel is established and packet data services may be started. 
         [0032]    The first step a MS takes begins an authentication, authorization, and accounting process. Authentication is the process of identifying and individual, most often, by a username and password. The authentication process assumes that a username and password uniquely identify a subscriber. 
         [0033]    Authorization allows a user access to network resources after authentication. Varying levels of access may be possible and users may be granted or denied access to network resources depending on the level of authorization. 
         [0034]    Accounting is the tracking of a user&#39;s activity while accessing network resources and includes the amount of time spent on the network, the services used while on the network, and the amount of data transferred during the network session. 
         [0035]    Authentication and authorization to access network resources is performed when the MS attempts to access packet data services. Service authorization is usually independent of WLAN authentication and authorization. The H-AAA server performs authentication and authorization using an access protocol, such as the Remote Authentication Dial-In User Service (RADIUS), or DIAMETER. RADIUS is an authentication and accounting system used by many internet service providers. 
         [0036]    IP Security (IPsec) provides confidentiality, data integrity, access control and data source authentication to IP datagrams. These services are provided by maintaining a shared state between the source and the sink of an IP datagram. This state defines the specific services provided to the datagram and which cryptographic algorithms will be used to provide the services, and the keys used as input to the cryptographic algorithms. A protocol, know as the Internet Key Exchange (IKE) is used to establish this shared state. 
         [0037]    IKE performs mutual authentication between two parties and also establishes an IKE security association (SA) that includes shared secret information that can be used to efficiently establish SAs for Encapsulating Security Payload (ESP) and/or Authentication Header (AH) and a set of cryptographic algorithms to be used by the SAs to protect the traffic that they carry. An initiator proposes the set of cryptographic algorithms used to protect a SA. An IKE SA is called an “IKE_SA”. The SAs for ESP and/or AH that are set up through that IKE_SA are known as “CHILD_SAs”. 
         [0038]    All IKE communications consist of pairs of messages: a request and a response. The pair is known as an exchange. The first messages that establish the IKE_SA are the initial exchange “IKE_SA_INIT” and “IKE_AUTH”. Subsequent exchanges that establish a child SA are known as “CREATE_CHILD_SA” or informational exchanges. In a common case, there first is a single IKE_SA_INIT exchange and a single IKE_AUTH exchange using a total of four messages to establish the IKE_SA and the first CHILD_SA. In some cases more than one such exchange may be needed. In all cases, the IKE_SA_MIT exchanges must complete prior to any other exchange type. Next, all the IKE_AUTH exchanges must be completed. Following any number of CREATE_CHILD_SA exchanges and INFORMATIONAL exchanges may follow in any order. Subsequent exchanges may establish additional CHILD_SAs between the same authenticated pair of endpoints. 
         [0039]    IKE message flow consists of a request followed by a response. It is the responsibility of the requester to ensure reliability. If the response is not received within a timeout interval, the requester needs to retransmit the request or abandon the connection. 
         [0040]    The first request/response of an IKE session negotiates the security parameters of the IKE_SA, sends nonces, and Diffie-Hellman values. 
         [0041]    The second request response, IKE_AUTH transmits identities, proves knowledge of the secrets corresponding to the two identities, and sets up a SA for the first AH and/or ESP CHILD_SA. 
         [0042]    Subsequent exchanges may create CHILD_SAs (CREATE_CHILD_SA) and INFORMATIONAL, which may delete a SA, report error conditions or other housekeeping functions. Every request requires a response. Subsequent exchanges may not occur until after completion of the initial exchanges. 
         [0043]    The CREATE_CHILD exchange consists of a single request/response pair and may be initiated by either end of the IKE_SA after the initial exchanges are completed. All messages after the initial exchange are cryptographically protected using the negotiated cryptographic set of the first two messages of the IKE exchange. Either endpoint may initiate a CREATE_CHILD_SA exchange. A CHILD_SA is created by sending a CREATE_CHILD_SA request. The CREATE_CHILD_SA request may contain a payload for an additional Diffie-Hellman exchange to enable more robust guarantees for forward secrecy for the CHILD_SA. The keying material for the CHILD_SA is a function established during the establishment of the IKE_SA, the nonces exchanged during the CREATE_CHILD_SA exchange, and the Diffie-Hellman value (if the key exchange payloads are included in the CREATE_CHILD_SA exchange. 
         [0044]    In the CHILD_SA that was created during the initial exchange, a second key exchange payload and nonce, must not be sent. The nonces from the initial exchange are used to compute the keys for the CHILD_SA. 
         [0045]      FIG. 2  illustrates the contents of the CREATE_CHILD_SA. The initiator sends a SA offer(s) in the SA payload. A nonce is sent in the Ni payload. This nonce, and others contained in the IKE_SA_INIT messages are used as inputs to cryptographic functions. In the CREATE_CHILD_SA request and response, the nonces are used to add freshness to the key derivation technique used to obtain keys for the CHILD_SA, and to ensure the creation of strong pseudo-random bits from the Diffie-Hellman key. Nonces used in IKEv2 are randomly chosen and are at least 128 bits in size and are at least half the key size of the negotiated pseudo-random function. A Diffie-Hellman value may be sent in the KEi payload. The proposed traffic selectors are sent in the TSi and TSr payloads. If the SA offers include different Diffie-Hellman groups KEi must be an element of the group that the initiator expects the responder to accept. If the guess is wrong the CREATE_CHILD_SA exchange will fail and will need to be retried with a different KEi. 
         [0046]    The message following the header is encrypted and the message including the header is integrity protected using the negotiated cryptographic algorithms for the IKE_SA. 
         [0047]      FIG. 3  shows the contents of the CREATE_CHILD_SA response. The responder replies using the same message identifier with the accepted offer in a SA payload and a Diffie-Hellman value in the KEr payload if KEi was included in the request and the negotiated cryptographic set includes that group. If the responder selects a cryptographic set with a different group, it must reject the request. The initiator should then repeat the request, but with a KEi payload from the group the responder selected. The traffic selectors for traffic to be sent on that SA are specified in the traffic selector (TS) payloads, which may be a subset of the initiator of the CHILD_SA proposed. Traffic selectors may be omitted if the CREATE_CHILD_SA request is being used to change the key of the IKE_SA. 
         [0048]    Once the CHILD_SA has been created, the next step is to set up the IPsec tunnel Tunnel establishment procedures are detailed below. 
         [0049]    The MS may either be pre-provisioned with the IP address of the PDIF or shall use DNS mechanisms to retrieve the IP address of the PDIF. When building a FQDN for the DNS request the MS should identify the operator&#39;s network. To facilitate access to the network, the MS may be pre-provisioned with the FQDNs of multiple PDIFs. Once a MS receives a response containing one or more PDIF IP addresses, the MS selects a PDIF IP address with the same IP version as its local IP address that is the IP address allocated by the WLAN at successful association. This selection may be performed by the user or may be performed automatically by the MS. Several mechanisms may be used to discover the PDIF and are implementation dependent. 
         [0050]    A message exchange is used to set up the IPsec tunnel between the MS and the PDIF.  FIG. 4  shows this message exchange. In step  1  the MS authenticates to the WLAN Access Network and gains access to the Internet. This may involve the WLAN checking with the H-AAA for authorization. 
         [0051]    In step  2  the MS obtains an IP address from the Access Network. The MS also discovers the default router and the DNS server addresse(s). 
         [0052]    In step  3  the MS begins an IKEv2 exchange with the PDIF. The first set of messages sent in this exchange is the initial exchange, designated IKE_SA_INIT. 
         [0053]    In step  4  the MS initiates the IKE_AUTH exchange with the PDIF. These messages are encrypted and integrity protected with the keys established during the IKE_SA_NIT exchange. 
         [0054]    The MS requests a tunnel inner IP address (TIA) in step  5 , by setting the CONFIGURATION payload in the IKE_AUTH request. The MS includes its Network Access Identifier (NAI) in the payload. If the MS wishes to use the Extensible Authentication Protocol (EAP) it does not include the authorization (AUTH) payload in the IKE_AUTH message. 
         [0055]    In step  6  the PDIF receives the IKE_AUTH request without the AUTH payload it contacts the H-AAA to request service authorization and user authentication information by sending the EAP-Response/Identity message in the RADIUS Access-Request message or Diameter-EAP-Request (DER) command. 
         [0056]    In step  7  EAP messages are exchanged between the MS and H-AAA. The H-AAA sends an EAP request message in the RADIUS Access-Challenge or in a Diameter-EAP-Answer (DEA) command to the PDIF. The PDIF sends the IKE_AUTH reply message including the EAP request message to the MS. 
         [0057]    The MS responds in step  8  with the IKE_AUTH request message including the EAP response message. The PDIF sends the EAP response message in the RADIUS Access-Request message or the Diameter-EAP-Request Command to the H-AAA. Steps  7  and  8  may occur a number of times. 
         [0058]    If the authentication is successful, in step  9  the H-AAA sends the EAPSuccess in the RADIUS Access-Accept message or, a DEA command with a code indicating successful authentication. 
         [0059]    In step  10 , upon receipt of a RADIUS Access-Accept message or a DEA command with a result code that indicates successful authentication, the PDIF sends an IKE_AUTH response message that includes the EAP success. If the PDIF receives a RADIUS-Reject message or a DEA command with a result code indicating failure of authorization, the PDIF rejects tunnel establishment toward the MS and sends an IKE_AUTH response message with the Notify payload set to ‘AUTHENTICATION FAILED’. 
         [0060]    The MS then sends the IKE_AUTH request message in step  11 , including the AUTH payload calculated from the Master Session Key (MSK) which is generated upon successful EAP authentication. 
         [0061]    The PDIF replies with the IKE_AUTH response message in step  12 , including an assigned TIA, AUTH payload, and security authorizations. The PDIF uses the MSK to compute the AUTH payload. The PDIF obtains the MSK from the H-AAA in step  9 , above. 
         [0062]    In step  13 , when the IKE_AUTH exchange is completed, an IPsec tunnel is established between the MS and the PDIF. 
         [0063]      FIG. 4B  illustrates the steps in normal tunnel establishment flow. This may be utilized when establishing multiple tunnels as discussed further below. 
         [0064]    It is possible to establish multiple tunnels to the same PDIF. Once the IKE 
         [0065]    Security Association (SA) has been authenticated, more than one child SA can be negotiated within the IKE_SA. The exchange is known as the CREATE_CHILD_SA is protected and uses the cryptographic algorithms and keys negotiated in the first two messages of the IKE exchange, as described above. As a result, the creation of additional CHILD_SAs between the MS and the PDIF does not trigger further authentication messaging to the H-AAA. 
         [0066]    The MS may want to simultaneously have IPv4 and IPv6 access to the same PDIF. Although the IKEv2 standard allows such simultaneous access in the same or separate IPsec tunnels, authorization is not addressed and the PDIF needs to know whether the MS requesting dual-stack authorization is authorized for IPv4 and IPv6. 
         [0067]    The first embodiment addresses the question of the PDIF knowing if the requesting MS is authorized for IPv4 and/or IPv6. During the IPsec tunnel establishment as described above, if the EAP authorization is successful, the H-AAA returns the IP-Version-Authorized VSA in the RADIUS Access-Accept message to indicate whether IPv4 and/or IPv6 are authorized. If the IP-Version-Authorized VSA is not present in the RADIUS Access-Accept message the PDIF shall apply its local policy for the authorization of dual stack operation.  FIG. 5  shows the structure of the IP-Version-Authorized RADIUS VSA. 
         [0068]    Another embodiment is used when the MS wants to use IPv4 and IPv6 simultaneously and is authorized to use both.  FIG. 6  illustrates the method of this embodiment. The method,  600  begins when the MS requests IPv4-IPv6 dual stack operation in step  602 . This request is in the form of a message sent to the AAA server through the PDIF. In step  604 , the AAA server determines if the MS is authorized to use both IPv4 and IPv6. In step  606  the AAA server informs the PDIF that the requesting MS is authorized to use both IPv4 and IPv6. The PDIF informs the MS in step  608  that the request for IPv4-IPv6 dual stack operation is authorized. In step  610 , the MS and PDIF establish separate CHILD_SAs under the same IKE_SA for IPv4 and IPv6. If the MS is not authorized for both IPv4 and IPv6, the AAA server informs the PDIF in step  612 . In turn, the PDIF informs the MS in step  614  of the non-authorization and also informs the MS which IP version is not authorized. 
         [0069]    Yet another embodiment is used when the MS may desire to use both IPv4 and IPv6 simultaneously, but may only be authorized for IPv4.  FIG. 7  illustrates the method of operation of this embodiment. The method,  700  begins with step  702  when the MS requests IPv4-IPv6 dual stack operation. In step  704  the AAA server checks to see that the MS is authorized for both IPv4 and IPv6. If the MS is authorized for both IPv4 and IPv6, the method returns to step  606  of the method of  FIG. 6 . If the MS is authorized for only IPv4, the AAA server informs the PDIF that the MS is only authorized for IPv4. The PDIF sends a Notify Payload with the Notify Message Type set to a specific message type that indicates that only IPv4 is authorized in step  710 . If the wireless communication system operates using the 3GPP2 standard, the Message Type is set to 8193 in the IKE_AUTH Response message. Other operating systems may use different message types, but do not affect the operation of this embodiment. In this case, in step  712  only the IPsec tunnel for IPv4 will be established. To prevent the MS from establishing an IPv6 session with the network, the MS sets the INTERNAL_IP6_ADDRESS attribute t 0::0 in CFG request payload. The PDIF sets the length of the INTERNAL_IP6_ADDRESS attribute to zero in the CFG reply payload. The PDIF may notify the MS that the MS is not authorized for IPv6 access by sending a Notify Payload with a specific message type indicating errors. If the MS tries to acquire an IPv6 prefix from the PDIF, the PDIF discards the message without notifying the MS. 
         [0070]      FIG. 8  illustrates an embodiment used when the MS desires to utilize IPv4 and IPv6 dual stack operation but is only authorized for IPv6. The method,  800 , begins with step  802  when the MS requests IPv4-IPv6 dual stack operation. The AAA server checks to see if the MS is authorized for IPv4 and IPv6 in step  804 . If the MS is authorized for both IPv4 and IPv6, the method returns to step  606  of  FIG. 6 . If the MS is not authorized for IPv4 and IPv6 and is only authorized for IPv6 in step  808  the AAA server informs the PDIF that the MS is only authorized for IPv6. In step  810 , the PDIF sends the Notify Payload Message with the Notify Message Type set to a specific message type that indicates that the MS is only authorized for IPv6 in the IKE_AUTH Response message. If the wireless communication system operates using the 3GPP2 standard, the Message Type is set to 8194. In step  812  the IPsec tunnel for IPv6 is established. The MS is prevented from establishing an internal IPv4 session with the network by having the MS set the INTERNAL_IP4_ADDRESS attribute to 0.0.0.0 in the CFG request payload. Likewise, the PDIF sets the length of the INTERNAL_IP4_ADDRESS attribute to zero in the CFG reply payload. The PDIF may notify the MS that the MS is not authorized for IPv4 access by sending a Notify Payload with a specific message type. If the MS attempts to acquire an IPv4 prefix from the PDIF the PDIF discards the message without notifying the MS. 
         [0071]    In further embodiments, those skilled in the art will appreciate that the foregoing methods can be implemented by the execution of a program embodied on a computer readable medium, such are the memory of a computer platform. The instructions can reside in various types of signal-bearing or data storage primary, secondary, or tertiary media. The media may comprise, for example, RAM accessible by, or residing within, the client device and/or server. Whether contained in RAM, a diskette, or other secondary storage media, the instructions may be stored on a variety of machine-readable data storage media, such as DASD storage (e.g., a conventional “hard drive” or a RAID array), magnetic tape, electronic read-only memory (e.g., ROM or EEPROM), flash memory cars, an optical storage device (e.g., CD-ROM, WORM, DVD, digital optical tape), paper “punch” cards, or other suitable data storage media including digital and analog transmission media. 
         [0072]    While the foregoing disclosure shows illustrative embodiments of the invention, it should be noted that various changes and modifications could be made herein without departing from the scope of the invention as defined by the appended claims. The activities or steps of the method claims in accordance with the embodiments of the invention described herein need not be performed in any particular order. Furthermore, although elements of the invention may be described or claimed in the singular, the plural is contemplated unless limitation to the singular is explicitly stated. 
         [0073]    Preferred embodiments of the present invention have thus been shown and described. It would be apparent to one of ordinary skill in the art, however, that numerous alterations may be made to the embodiments herein disclosed without departing from the spirit or scope of the invention. Therefore, the present invention is not to be limited except in accordance with the following claims.