Abstract:
A system and method using the concept of secondary PDP context defined in the  3 GPP specification in order to preserve a uniform connectivity to a GGSN while roaming from different networks through a handover mechanism. The handover mechanism involved is efficient, with minimal messaging overhead, and preserves the IP address of the client. Thus the data connections do not suffer from interruptions. In one example embodiment, the present innovations establish a secondary PDP context through an alternate, non-GPRS access network in areas covered by both GPRS and a non-GPRS access technology (such as a WLAN). The GPRS access network uses a primary PDP context, which is maintained (though dormant) while the alternate access network and secondary PDP context are used.

Description:
CROSS-REFERENCE TO OTHER APPLICATIONS  
       [0001]     This application claims priority from provisional patent application 60/629,855, filed on Nov. 18, 2004, which is hereby incorporated by reference.  
         [0002]     This application also claims priority from provisional patent application 60/705,224, filed on Aug. 3, 2005, which is hereby incorporated by reference. 
     
    
     FIELD OF THE INVENTION  
       [0003]     The present inventions relate generally to wireless data movement and, more particularly, to how wireless devices maintain consistent network connections when more than one network is present.  
       BACKGROUND  
       [0004]     Wireless networks have evolved from a simple point-to-point link to encompassing different coverage areas at varying data transfer rates. For example, a short ranged network (made up of connectivity devices such as Bluetooth capable devices) provides data rates in excess of 3 Mb/s covering a small room; a medium range network (such as Wi-Fi or 802.11x) that provides data rates of 25 Mbps covering a several rooms; a large range network (such as The Global System for Mobile TeleCommunications (GSM)) with cells that provide several hundred kbits/s data rate covering a city; and the largest connectivity devices, satellite networks, provide data rates of up to 144 kbits/s that can cover several countries. The multi-mode mobile terminal has capabilities to connect to different networks based on the policies of the user and the network, such as the particular sources that have been purchased or provided. Due to the overlapping of these networks a user can roam through multiple networks during a single session. In all roaming scenarios, the handover mechanism between these different networks is a vital topic.  
         [0005]     General Packet Radio Service (GPRS) is a data communication technology that is capable of transferring packet data and signaling in a cost-efficient manner over GSM radio networks while optimizing the use of radio and network resources. The voice traffic and the data packet share the same physical channel, but new logical GPRS radio channels are defined. Data transfer rates up to 171.2 Kbps are possible over GPRS thus enabling mobile data services, like Internet applications, over mobile devices. The data traffic is segregated and sent to a Serving GPRS Support Node (SGSN) node from the BSC. The SGSN node connects to a Gateway GPRS Support Node (GGSN) for communication with external packet data networks. The next generation of this technology is UMTS that provides higher data transfer rates. Typically GPRS and UMTS networks operate over licensed frequencies and are owned by mobile operators. Several entities have created a partnership project called 3GPP that is responsible for defining services, architecture and protocols. These specifications cover wireless access, network nodes and interconnection protocols etc.  
         [0006]     A Wireless Local Area Network (WLAN) is a wireless extension to Ethernet LAN technologies. The IEEE 802.11 committee has defined several of these standards and named them 802.11b, 802.11g and 802.11a. In WLAN, each service access point (AP) covers a cell. In IEEE 802.11, each single cell is defined as a basic service set (BSS). Several BSSs can form an extended service set (ESS). IEEE 802.11 only defines the communication between mobile terminal (MT) and access point (AP) (the physical layer and data link layer). The MT connects to the AP that has higher signal quality and communicates wirelessly to the AP. The data communication is similar to the wired Ethernet communication except for the physical layer and medium access.  
         [0007]     802.11x WLAN technologies, popularly known as the Wi-Fi, have become predominant in the limited mobility wireless data networks due to reasonably higher data transfer rates and affordability of the technology. In fact, 3GPP has come up with a specification (TS 23.234) on how to interwork WLAN with GPRS/UMTS networks. Both these wireless technologies are complimentary in several aspects. Therefore, many operators provide both services, with GPRS for global roaming and Wi-Fi for limited mobility areas popularly known as hotspots. There are several devices that support these dual technologies paving way for pervasive computing. The hotspots are WLAN islands scattered at key geographic locations. The mobile user would be roaming between GPRS coverage area and Wi-Fi coverage area very frequently thus requiring a fast and efficient handover procedure.  
         [0008]     To achieve seamless mobility, the MT should do fast handover from GPRS network to WLAN or vice versa without interruption. Several methodologies have been proposed for this roaming scenario. Two different methodologies that address this problem are described below.  
         [0000]     Background: Mobile IP  
         [0009]     Mobile IP (MIP) provides mobility at the network layer thus enabling roaming between different networks. The MIP is specified in Request for Comments (RFC) 2004 by the Internet Engineering Task Force (IETF) community. MIP defines two nodes, Home Agent (HA) and Foreign Agent (FA). The HA is the coordinating node on the home network of a user. The mobile node communicates to HA node directly, using normal IP routing, when connected to the home network. A Foreign Agent is a node in a MIP network that enables roamed IP users to register on the foreign network. The FA will communicate with the HA (Home Agent) to enable IP data to be transferred between the home IP network and the roamed IP user on the foreign network. Whenever the node is connected on a foreign network, it acquires a care-of-address (COA) and registers with the HA providing the COA. The data packets sent by a correspondent node (CN) destined to the mobile node are captured by HA in the home network and are tunneled to the COA. The packets are decapsulated either at FA or MT. When the MT roams to another network, it acquires new COA and registers with HA about its new location. Now all the data packets destined to this mobile node are tunneled to the new COA.  
         [0010]     One common solution for GPRS and WLAN mobility using MIP is to provide home agent (HA) functionality at the Gateway GPRS Support Node (GGSN). The FA functionality can be at Serving GPRS Support Node (SGSN) for the GPRS network and at the access point for the Wide Local Area Network (WLAN). Otherwise a co-located Care of Address (COA) can be used if the MT supports MIP.  
         [0011]      FIG. 1  illustrates this type of communication network. A GGSN  102  is connected to both a SGSN  104  and a WLAN Gateway  106 . There is generally a constant connection between the GGSN, SGSN, and WLAN Gateway. Clients  108 ,  110  may connect to the GGSN through either the SGSN or through the WLAN Gateway. The GGSN provides connectivity to an IP network such as the Internet.  
         [0012]     Though MIP provides mobility between these two networks the handover is not seamless because of the time delay from the point the MT moves to a different network and the registration with the HA is completed. During this phase, HA sends all packets for MT towards the old COA and could be lost. This is a problem when roaming from WLAN to GPRS network since the WLAN connection is gone and any packets sent over this network will not reach the MT. The other drawback of this solution is the triangle routing of the data packets (the packets from MT to the CN correspondent node (CN) are directly routed while the packets from CN are sent to HA first and then tunneled to MT) that is inherent in the MIP. Route optimization methods have been proposed to overcome this issue. Finally, there are 3GPP services that are valuable to operators and useful to end-users. Such services are accessible at the GGSN. Since HA is an independent entity.  
         [0000]     Background: Inter-SGSN Like Handover Approach  
         [0013]     The WLAN coverage cell is small compared to the cell of the GSM area. One method of integrating these two networks is by treating the WLAN as a smaller network within the GSM network. Several Access Points (AP) connecting to a WG represent a small coverage area. In “Method and System for Transparently and Securely Interconnecting a WLAN Radio Access Network into a GPRS/GSM Core Network” it has been demonstrated how the WG could function in a manner similar to the SGSN and thereby providing an interconnection into GPRS core network. The roaming scenario is just like an Inter-SGSN Routing Update process described in the GSM specification. When the MT roams in to WLAN area, the WG based on the information of the existing GPRS PDP context, sends an Update PDP Context to the GGSN that will transfer the existing GPRS session to this network.  
         [0014]     The GGSN sends a new packet data protocol/mobility management context standby command to the old SGSN. The message is to ask the SGSN to hold the PDP/MM context till the MT comes back to the UMTS or detaches. The packets are sent over the WLAN to the GGSN and the IP address of the session still remains the same. When the MT roams back to the GPRS network, triggering a periodic RA update procedure activates the old GPRS session. The handover delay in this process is lower than that of the Mobile IP method described earlier. Due to the tight integrated nature of this solution, the LAN based architecture on the WLAN needs several changes to accommodate this. Also, the client should be intelligent enough to obtain the GPRS session parameters. Since it is not an open architecture solution, this method is not preferred.  
         [0000]     Background: Secondary PDP Context  
         [0015]     The secondary PDP context is setup by reusing the PDP address and other PDP context information from an already active PDP context, but with a specific Traffic Flow Template (TFT). A unique Tunnel Identifier (TI) and a unique NSAPI preferably identify each PDP context sharing the same PDP address and Access Point Name (APN). The MT sends an Activate Secondary PDP Context Request (Linked TI, NSAPI, QoS Requested, TFT, PDP Configuration Options) message to the SGSN. The linked TI indicates the TI value assigned to any one of the already activated PDP contexts for this PDP address and APN. Contained within the requested QoS is the desired QoS profile. A TFT is preferably sent transparently through the SGSN to the GGSN to enable packet classification for downlink data transfer. The TI and NSAPI preferably contain values not used by any other activated PDP context. PDP Configuration Options may be used to transfer optional PDP parameters and/or requests to the GGSN. The SGSN validates the request and sends a Create PDP Context Request (QoS Negotiated, Tunnel Endpoint Identifier (TEID), network service access point identifier (NSAPI), Primary NSAPI, TFT, PDP Configuration Options, serving network identity) message to the affected GGSN. The GGSN uses the same packet data network as used by the already-activated PDP context(s) for that PDP address, generates a new entry in its PDP context table, and stores the TFT. The new entry allows the GGSN to route PDP PDUs via different GTP tunnels between the SGSN and the packet data network. The GGSN returns a Create PDP Context Response (TEID, QoS Negotiated, Cause, PDP Configuration Options, Prohibit Payload Compression, APN Restriction) message to the SGSN. The SGSN selects Radio Priority and Packet Flow Id based on QoS Negotiated, and returns an Activate Secondary PDP Context Accept (TI, QoS Negotiated, Radio Priority, Packet Flow Id, PDP Configuration Options) message to the MT. The SGSN is now able to route PDP PDUs between the GGSN and the MT via different GTP tunnels and possibly different LLC links. For more details of this process, please refer to the 3GPP spec. TS 23.060.  
         [0000]     Background: Data Flow Over Secondary PDP Contexts  
         [0016]     GGSN and MT use the TFT to distinguish the different user traffic flows. A TFT consists of from one and up to eight packet filters, each identified by a unique packet filter identifier. A packet filter also has an evaluation precedence index that is unique within all TFTs associated with the PDP contexts that share the same PDP address. This evaluation precedence index is in the range of 255 (lowest evaluation precedence) down to 0 (highest evaluation precedence). The MT manages packet filter identifiers and their evaluation precedence indexes, and creates the packet filter contents.  
         [0017]     Each valid filter contains a unique identifier within a given TFT, an evaluation precedence index that is unique within all TFTs for one PDP address, and at least one of the following attributes:  
         [0018]     Source Address and Subnet Mask;  
         [0019]     Protocol Number (IPv4)/Next Header (IPv6);  
         [0020]     Destination Port Range;  
         [0021]     Source Port Range;  
         [0022]     IPSec Security Parameter Index (SPI);  
         [0023]     Type of Service (TOS) (IPv4)/Traffic Class (IPv6) and Mask;  
         [0024]     Flow Label (IPv6).  
         [0025]     Some of the above-listed attributes may coexist in a packet filter while others mutually exclude each other. If the parameters of the header of a received PDP PDU match all specified attribute values in a packet filter, then it is considered that a match is found for this packet filter and the PDP context associated with the TFT defining this filter is sued for packet transmission. In this case, the evaluation precedence is aborted. Other packet filters in increasing order of their evaluation precedence index are evaluated until such a match is found. If no match is found the PDP context that has no TFT defined will be used, if such a PDP context exists.  
       Maintaining Consistent Network Connections Using a Secondary PDP Context  
       [0026]     In one example embodiment, the present innovations include a system and method for maintaining a consistent connection when a user moves into an area served by more than one access network for a wireless device or mobile terminal (MT) such as a cellular telephone, handheld device, or laptop computer. An example is presented in the context of an area served by a GPRS access network and a WLAN access network. In this example context, user first connects through a primary (e.g., GPRS) access network using a primary PDP context. When access is available using a secondary (e.g., WLAN) access network, a secondary PDP context is used in an alternate communication path, while maintaining the primary PDP context (though it may be unused).  
         [0027]     In a preferred embodiment, primary PDP context information is stored at least on the user&#39;s MT, an SGSN, and a GGSN (for example, to access a packet switched (PS) domain). The secondary PDP context information is preferably stored at least on the user&#39;s MT, an alternate node (such as an M-WSG), and the GGSN. By using a secondary PDP context, the user&#39;s MT PDP address (e.g., a dynamic IP address) can be reused for either communication path, facilitating seamless access to a PS domain when switching between GPRS and non-GPRS access networks. A traffic flow template (TFT) is preferably used to classify packets (more generally protocol data units or PDUs) at the GGSN to be sent along the proper path in the downlink direction (i.e., from the GGSN toward the MT). The TFT preferably comprises filters, each uniquely identified by a packet filter identifier. The packet filters also preferably include evaluation precedence capability so that one communication path can be a preferred path.  
         [0028]     The present innovations provide at least one or more of the following advantages: 
        Handover delay is reduced because the call setup process exchanges one message each way (except for network setup messages);     Traffic flow is transferred only after the secondary PDP context is established, thus no packets are lost as long as the two access networks overlap;     Standards-compliant messaging is used, with no changes to existing nodes;     Secondary PDP context shares PDP address with primary PDP context, preventing disruption at handover;     Provides roaming solution between multiple overlapping networks (not just two overlapping networks) using additional TFTs;     All traffic flows between client and external node can go through the same GGSN even after handover thus avoiding any routing discrepancies; no triangle routing issues as seen in MIP;     Based on approved 3GPP standards thus allowing interoperability with all GPRS and WLANs.        
 
     
    
     BRIEF DESCRIPTION OF THE DRAWINGS  
       [0036]     The disclosed inventions will be described with reference to the accompanying drawings, which show important sample embodiments of the invention and which are incorporated in the specification hereof by reference, wherein:  
         [0037]      FIG. 1  describes the network architecture of GPRS network, WLAN and the convergence of these networks for mobile node data connectivity.  
         [0038]      FIG. 2  shows a set of network nodes consistent with implementing a preferred embodiment of the present innovations.  
         [0039]      FIG. 3  is a call flow diagram showing communication between various nodes consistent with implementing a preferred embodiment of the present innovations.  
         [0040]      FIG. 4  shows a flowchart with process steps consistent with implementing a preferred embodiment of the present innovations.  
         [0041]      FIG. 5  shows a flowchart with process steps consistent with implementing a preferred embodiment of the present innovations.  
     
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS  
       [0042]     The numerous innovative teachings of the present application will be described with particular reference to the presently preferred embodiment (by way of example, and not of limitation).  
         [0043]     In one example embodiment, the present innovations include a system and method for maintaining a consistent connection when a user moves into an area served by more than one access network for a MT. An example is presented in the context of an area served by a GPRS access network and a WLAN access network (or multiple WLANs). A first communication path is established through a first access network, and when a second access network becomes available, a second communication path is also established (while maintaining the first communication path). In the example context mentioned above, a user first connects through a primary (e.g., GPRS) access network using a primary PDP context. When access is available using a secondary (e.g., WLAN) access network, a secondary PDP context is used to establish an alternate communication path, while maintaining the primary PDP context (though it may be unused). In preferred embodiments, the GPRS connection (with the primary PDP context) should always be connected. This connection will preferably be dormant when the secondary PDP context is active. Since no GPRS network resources are used in this phase this drawback is small. When the user leaves the WLAN access area (or other conditions occur, such as signal strength falls below a threshold), the secondary PDP context is deactivated, and communications automatically resume across the primary PDP context connection.  
         [0044]      FIG. 2  shows an example context  200  consistent with implementing a preferred embodiment of the present innovations. This example includes three access networks which overlap, GPRS access network  204 , WLAN access network  212  and WLAN access network  216 . User accesses one of these networks using mobile terminal (MT)  202  from a location where two or more of the access networks overlap.  
         [0045]     In a first example embodiment, MT  202  enters an area accessible by GPRS access network  204 . The user connects to access network  204  which provides connectivity to SGSN  206  using a “primary” PDP context which is preferably requested by MT  202 . This primary PDP context information is maintained at least at MT  202 , SGSN  206 , and GGSN  208 . The PDP context includes such information as PDP type, the PDP address, QoS, NSAPI, and other information. The GGSN typically provides a PDP address (e.g., and IP address) to MT  202  during PDP activation. Though preferred embodiments include a dynamic PDP address assigned to MT  202 , a static PDP address can also be used.  
         [0046]     Once the PDP context is activated, the PDP address is available for data transfer. In this example, the primary PDP context includes a path through at least MT  202 , SGSN  206 , and GGSN  208 , for example, in communication with packet switched network  210  which is accessed through GGSN  208 .  
         [0047]     When MT  202  roams into an area served by WLAN access network  212  as well as GPRS access network  204 , MT  202  detects the WLAN and initiates connection, for example, by providing authentication credentials, IMSI, and primary PDP context session NSAPI values to M-WSG  214 . M-WSG  214  initiates a secondary PDP context setup with GGSN  208 . A TFT is used for this secondary PDP context, preferably including a packet filter defined based on some parameters such as Type of Service and Mask value. GGSN  208  applies this filter to all downlink traffic flows (i.e., traffic flowing toward MT  202 ). The GGSN thereby is able to route information across the secondary PDP context route, which includes at least (in this example), MT  202 , M-WSG  212 , and GGSN  208 .  
         [0048]     If there is a second WLAN access network  216  also overlapping the service areas of GPRS access network  204  and WLAN access network  212 , then the packet filter(s) preferably include precedence or priority so that an access route can be chosen. For example, precedence could be based on the strongest signal or on which access network was most recently detected, or it could be manually set by a user. If WLAN access network  216  is used for access, then a third PDP context is created as described above which is stored at least at MT  202 , M-WSG  214 , and GGSN  208  and which is used by GGSN  208  (using appropriate filters) to route PDUs to MT  202  via M-WSG  214  through access network  216 . These innovative concepts can therefore be generalized to any number of overlapping access networks. In preferred embodiments, the GPRS access network uses a PDP context with no defined TFT, and is therefore the default access network.  
         [0049]     As described above, the present innovations can be implemented in a GPRS network with various access technologies, such as a WLAN access network. The call flows in this case are as shown in  FIG. 3 . It is noted that this is only one context in which the present innovations can be implemented, and the following is presented only as an example embodiment for purposes of description. This example is not intended to suggest limitations to the application of the present innovations. Each of the steps indicated in the call flow diagram of  FIG. 3  are explained below:  
         [0000]     GPRS Control Connection  
         [0000]    
       
         
           
              1. The mobile terminal attaches over the GSM air interface to initiate the GPRS session. The GPRS attach is made to the SGSN by providing the MT&#39;s Packet TMSI or IMSI, and the RAI. After having executed the GPRS attach, the MT is in READY state to activate the PDP contexts.  
              2. The MT sends an Activate PDP context Request message to the SGSN with all required parameters viz., NSAPI, TI, PDP type, optional PDP address, optional APN, QoS requested and any PDP configuration options. SGSN performs the security functions to authorize and authenticate user by interacting with HLR, not shown in the figure.  
              3. The SGSN sends a create PDP context request message to the corresponding GGSN. The following minimum parameters are sent in the create request; PDP Type, APN, QoS Negotiated, TEID, NSAPI, MSISDN, Selection Mode, Charging Characteristics.  
              4. GGSN validates the request and creates a new entry in its PDP context table and generates a charging Id. This allows GGSN to route PDP PDUs between the SGSN and the external packet data network. GGSN returns a create PDP context response with the approved values, including the dynamically assigned IP address.  
              5. The SGSN selects the Radio Priority and Packet flow Id based on the QoS negotiated. An activate PDP context accept message with the negotiated parameters (PDP Type, PDP Address, TI, QoS Negotiated, Radio Priority, Packet Flow Id and PDP configuration options) is sent to MT. The SGSN is now able to route PDP PDUs between the GGSN and MT. 
 
 GPRS Data Flow 
 
              6. The client uses the GGSN assigned PDP address as the IP address to communicate to other nodes. The client sends data through SGSN since the GGSN is the default gateway for the node. All packets directed towards the client are sent to GGSN. GGSN identifies the session based on the PDP address and encapsulates the packet into a GTP data packet and tunnels to SGSN. The packet is de-capsulated at SGSN and sent to the MT over the GSM air interface. 
 
 Roaming into WLAN Hotspot 
 
 The client is triggered either automatically (by detecting a preferred WLAN) or manually (explicitly initiation) to initiate a handover to WLAN. The process of setting up WLAN connection and handover of connection are as follows: 
 
 WLAN Connection Setup 
 
              7. The client associates to a WLAN access point over the 802.11x radio. AP can perform any authorization and security functions, including EAPOL, WPA, for additional security.  
              8. Client sends a request to the M-WSG to setup a connection by including the NSAPI of the existing PDP context and the IMSI values. M-WSG performs the authentication of the client through standard procedures. In this process also obtains the APN information, MSISDN, QoS parameters and GGSN address associated with this client (by interacting with HLR, not show in the figure).  
           
         
       
     
         [0058]     9. The M-WSG sends activate secondary PDP context request to the same GGSN that has the primary PDP context with the parameters; QoS Negotiated, TEID, NSAPI, Primary NSAPI, TFT, PDP Configuration Options. The Primary NSAPI indicates the NSAPI of the existing primary PDP context. The TFT value (defined in 3GPP spec. 24.008) that encompasses all possible TOS values, as defined in the following filter table, is sent.  
                                                       Component               Identifier   Precedence   Type (   TOS field   TOS Mask                   0x01   0x00   0x70   0x00   0x01       0x02   0x01   0x70   0x01   0x01       0x03   0x02   0x70   0x02   0x02       0x04   0x03   0x70   0x04   0x04       0x05   0x04   0x70   0x08   0x08       0x06   0x05   0x70   0x10   0x10       0x07   0x06   0x70   0x20   0x20                  
        10. GGSN validates the create secondary PDP context request and uses the same packet data network as used by the already-activated PDP context for that PDP address. This new entry is added to the PDP context table including the TFT associated with it. The GGSN returns a create PDP context response with TEID, QoS negotiated, Cause, PDP Configuration Options, APN restriction message to the M-WSG.     11. The M-WSG marks the PDP address value and the TEID value associated with the GTP tunnel. A message is sent to client to indicate the successful connection setup over the WLAN. 
 
 WLAN Handover Mechanism 
    12. The client has two flow paths to the same GGSN with different priority levels and there is no change in the IP address of the client, thus no effect to the higher layer protocols. Since WLAN has higher precedence, all the traffic is directed towards the WLAN connection. The packets are sent over WLAN to M-WSG, which tunnels them to the GGSN. GGSN de-capsulate the packets and routes to external network. Packets destined for the client arriving at the GGSN, are matched against the filters defined in the TFT that has the smallest evaluation precedence index. This procedure is repeated until a match is found. Since the filters defined encompass all possible TOS value, the packet will be tunneled over the secondary PDP context to M-WSG. The packet is de-capsulated at M-WSG and forwarded to the client over the WLAN connection. This way the entire traffic stream is handed over to the WLAN connection seamlessly. 
 
 Roaming Out of WLAN Hotspot 
    13. When the MT roams out of the WLAN hotspot, client sends a disconnect request with the session identifier.     14. M-WSG sends a delete PDP context request with the context parameters, TEID, NSAPI, Teardown Indicator, to the GGSN.     15. The GGSN removes the PDP context from its context table, clears the filters defined in the associated TFT and returns a Delete PDP Context Response message to the M-WSG.     16. M-WSG cleans up associated session and GTP context information and sends a delete session response to the client. The figure also shows the scenario where the WLAN connection is terminated from the network side (from M-WSG).     17. Client disassociates with the AP and the WLAN connection is removed from the interface index. 
 
 Handover to GPRS 
    18. At this point of time, the connection to external network over the primary PDP context is still present. The packets are transferred between the MT and the network over the GPRS connection, thus handing over the flow back to GPRS.        
 
         [0068]      FIG. 4  shows an overview of steps included in a preferred embodiment of the present innovations. Steps in this flowchart are generally consistent with those given in the example of  FIG. 3  and as indicated.  
         [0069]     First, a client with a mobile terminal initiates a primary PDP context setup after attaching to a GPRS access network (step  402 ). (Cf. steps  1 - 2  of  FIG. 3 .) The SGSN next performs the GTP tunnel setup by sending a create PDP context request to the GGSN (step  404 ). The network performs authorization and authentication as described in the 3GPP spec TS. 24.008. An IP address is assigned to the client (step  406 ). (Cf. steps  3 - 5  of  FIG. 3 .) The client can communicate with the external network (in this example, a packet switched network) using the GGSN assigned PDP address. All the traffic flows between the GGSN and the client through the SGSN (step  408 ). (Cf. step  6  of  FIG. 3 .) Upon entering a WLAN coverage area, the client detects the presence of the WLAN and initiates the connection setup over WLAN network by providing the authentication credentials, including IMSI, and primary PDP context session NSAPI values to the M-WSG (step  410 ). (Cf. step  7  of  FIG. 3 .) The M-WSG performs authorization/authentication of the subscriber and initiates a secondary PDP context setup (step  412 ). The NSAPI value provided by the client is passed as the linked NSAPI value and a higher value of this is sent as NSAPI for the secondary PDP context. The TFT used for this secondary PDP context has a packet filter defined based on the Type of Service and Mask value. The filter is chosen to pick all possible values of the TOS byte, thus matching all traffic flows. GGSN applies this filter for all traffic destined toward the client. (Cf. steps  8 - 11  of  FIG. 3 .) At this point, all traffic flows over the secondary PDP context (step  414 ) until the client leaves the area served by the access network associated with the secondary PDP context. (Cf. step  12  of  FIG. 3 .)  
         [0070]      FIG. 5  shows another process flow depicting an aspect of the present innovations, namely, the handback procedure for when the client or MT leaves the WLAN coverage area (in the above examples). This flowchart corresponds to steps  13 - 18  of  FIG. 3 ) First, the client leaves the WLAN coverage area (step  502 ), or some other pre-determined condition occurs, such as the WLAN signal strength falling below a threshold, or another access network becoming available. The client disconnects from the M-WSG (step  504 ), and the M-WSG sends a delete secondary PDP context request to the GGSN (step  506 ). The GGSN removes the secondary PDP context and all subsequent traffic is sent over the primary PDP context (step  508 ), which has remained throughout the call or session (though it may have been unused or dormant).  
         [0071]     All publications and patent applications mentioned in this specification are indicative of the level if skill of those in the art to which this invention pertains. All publications and patent applications are herein incorporated by reference to the same extent as if each individual publication or patent application was specifically and individually indicated to be incorporated by reference.  
         [0072]     3 G Mobile Networks , S. Kasera, N. Narang, McGraw-Hill, 2005.  
         [0000]     Abbreviations:  
         [0073]     The following is a list of abbreviations and meanings determined from the application. These abbreviations are intended only as a source of clarity and not intended to limit the scope of the application.  
                                   Abbreviation   Words Represented By Abbrievation                   3GPP   3rd Generation Partnership Project       AP   Access Point       APN   Access Point Name       BSC   The Base Station Controller       BSS   The Base Station Subsystem       CN   Correspondent Node       COA   Care of Address       ESS   Electronic Switching System       FA   Foreign Agent       GGSN   Gateway GPRS Support Node       GPRS   General Packet Radio Services       GSM   The Global System for Mobile Communications       GSN   GPRS Support Nodes       GTP   GPRS Tunneling Protocol       HA   Home Agent       IMSI   International Mobile Subscriber Identity       IPv4   Version 4 of the Internet Protocol       IPv6   Version 6 of the Internet Protocol       LAN   Local Area Network       MIP   Mobile IP       MT   Mobile Terminal       MSISDN   Mobile Station Integrated Services Digital Network       MT   Message Transfer       NSAPI   Network Service Access Point Identifier       PDP   Packet Data Protocol       PDU   Protocol Data Unit       QoS   Quality of Service.       SGSN   Serving GPRS Support Node       TEID   Terminal Equipment ID       TFT   The Traffic Flow Template       TI   Tunnel Identifier       TOS   Type of Service       TS   Technical Specification       UMTS   Universal Mobile Telecommunications System       WGS   Wireless Gateway Server       Wi-Fi   Wireless Fidelity       WLAN   Wireless Local Area Network                  
 
 Modifications and Variations 
 
         [0074]     As will be recognized by those skilled in the art, the innovative concepts described in the present application can be modified and varied over a tremendous range of applications, and accordingly the scope of patented subject matter is not limited by any of the specific exemplary teachings given.  
         [0075]     For example, the present innovations can be implemented, consistent and within the scope of the concepts disclosed herein, using any number of network types to maintain consistent connectivity while moving into and out of a network coverage area. Likewise, various access technologies can be used, including but not limited to WiFi, GPRS, and CDMA communication technologies.  
         [0076]     Another example, that the present innovations can be implemented using, consistent and within the scope of the concepts disclosed herein, is the EDGE network and/or WiMAX technology to enable constant connectivity.  
         [0077]     Another example, that the present innovations can be implemented using, consistent and within the scope of the concepts disclosed herein, is use of a router or other device to act as the proxy GSN as a standalone unit away from the GGSN.  
         [0078]     Another example, that the present innovations can be implemented using, consistent and within the scope of the concepts disclosed herein, is use of integrated telecommunications system to act as the proxy away from the GGSN.  
         [0079]     Another example, that the present innovations can be implemented using, consistent and within the scope of the concepts disclosed herein, is use of a proxy as a data distribution point where data is separated into two separate streams and the streams are optimized by the proxy for specific connections.  
         [0080]     Further, these innovative concepts are not intended to be limited to the specific examples and implementations disclosed herein, but are intended to include all equivalent implementations, such as (but not limited to) using different types of network protocols (known or unknown at this time) or other devices to replace the example devices used to describe preferred embodiments of the present innovations. This includes, for example, changing the network, in some minor way, such as by substituting protocol variables.  
         [0081]     None of the description in the present application should be read as implying that any particular element, step, or function is an essential element which must be included in the claim scope: THE SCOPE OF PATENTED SUBJECT MATTER IS DEFINED ONLY BY THE ALLOWED CLAIMS. Moreover, none of these claims are intended to invoke paragraph six of 35 USC section 112 unless the exact words “means for” are followed by a participle. Moreover, the claims filed with this application are intended to be as comprehensive as possible: EVERY novel and non-obvious disclosed invention is intended to be covered, and NO subject matter is being intentionally abandoned, disclaimed, or dedicated.