Abstract:
In mobile IP networks, when a mobile node (MN)  101  moves from one cell to another, handover occurs. The result of the handover is that the MN  101  connects to the network through a new access router (AR)  162 . The handover may occur between access routers of the same or different administrative domains. In all cases, the information related to the MN  101  has to be transferred from the old AR  185  to the new AR  162  in order to minimize the effect of the change of access routers.

Description:
BACKGROUND  
         [0001]    It is expected that Middle box like Network Address Translator (NAT) or Firewall or Proxy or ALG will not go away completely at least in near future. This box is going to exist in wireless networks due to a variety of reasons. For example, a wireless network provider would not like to expose the private addresses used in its network to the outside world. Similar problem also occurs, when a mobile user moves from a Wireless LAN (WLAN) environment (Office) to cellular network environment (Outside). Equipment&#39;s that provide services to the customers may include cache servers, proxy servers, content servers and load balancers. These equipments operate in private address space in a network provider&#39;s routing premise. This imposes a problem when the mobile user moves to the adjacent domain causing a hand-off. Currently standards are mainly looking into the issues of fast hand-offs and context transfer between access routers from one domain to another. The task of relocating context when the mobile node moves from one private address space to other private address space creates a problem especially when the mobile node has session with cache/content server which is in private address space of network provider.  
           [0002]    NAT, Firewall, Multimedia buffers, Signature Management for Intrusion detection system are all considered to be Middle box and are deployed widely in the enterprise and expected to grow. As trusted third parties are increasingly being asked to make policy decisions on behalf of the various entities participating in an application&#39;s operation, a need has developed for applications to be able to communicate their needs to the devices in the network that provide transport policy enforcement.  
           [0003]    Wireless network providers would like to use site-local private addresses in their networks. This creates a problem when the mobile node is connected to a content server and is downloading some data and hand-off occurs. It may be a good strategy to restart the session for certain applications but this strategy would not work for real-time interactive applications like gaming.  
           [0004]    The above-mentioned references are exemplary only and are not meant to be limiting in respect to the resources and/or technologies available to those skilled in the art.  
         SUMMARY  
         [0005]    The proposals in this invention include how to create a session dynamically in the middlebox in order to maintain the application context.  
           [0006]    We provide possible ways how this can be achieved using policy-based schemes or application aware signalling to inform the state change in flow.  
           [0007]    NAT, Firewall, Multimedia buffers, Signature Management for Intrusion detection system are all considered to be Middle box and are deployed widely in the enterprise and expected to grow. As trusted third parties are increasingly being asked to make policy decisions on behalf of the various entities participating in an application&#39;s operation, a need has developed for applications to be able to communicate their needs to the devices in the network that provide transport policy enforcement.  
           [0008]    Wireless network providers would like to use site-local private addresses in their networks. This creates a problem when the mobile node is connected to a content server and is downloading some data and hand-off occurs. It may be a good strategy to restart the session for certain applications but this strategy would not work for real-time interactive applications like gaming.  
           [0009]    An embodiment creates a session(s) in the middle-box by identifying the flows prior to context transfer by making use of policy mechanism or other suitable means. Our solution is valid for anyone of the three cases:  
           [0010]    1. If the mobile node is having a session with content server or cache server or proxy server or any other service entity and if that entity is from the same Autonomous System (AS).  
           [0011]    2. Or if both end points of the session are in private address space of the same AS.  
           [0012]    3. Or if both end points are on the same routing domain but after the hand-off the session requires some VPN or other special service to maintain the session across AS.  
           [0013]    For example, if a user is having a gaming session with the content server provided by his network operator (say in AS-1) and he moves to an adjacent routing domain (say AS-2) then his session will remain unaffected. It is assumed that during the context transfer both Mobile Node (MN) and the currently serving access router know each other&#39;s public addresses. Using addressing and flow information a pinhole can be created in the AS-1 and AS-2 middle-boxes. 
       
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS  
       [0014]    The disclosed inventions will be described with reference to the accompanying drawings, which show important sample embodiments of the invention, wherein:  
         [0015]    [0015]FIG. 1 shows a Reference architecture;  
         [0016]    [0016]FIG. 2 shows a context transfer message flow, according to an embodiment; and  
         [0017]    [0017]FIG. 3 shows a creation of pinhole in the NAT.  
     
    
     DETAILED DESCRIPTION  
       [0018]    An embodiment of the invention may be very simple to implement and does not rely on any external data. When the mobile node moves from the old Autonomous System (AS) to the new AS, the context transfer occurs and at the same time authorization of the mobile user takes place. Using the context and authorization information, the application specific context is retained and the flow is maintained between client and server  
         [0019]    [0019]FIG. 1 shows the reference architecture showing the entities that are involved during the hand-off operation when the mobile node moves from one AS to another AS. The hand-off and context transfer may be done by using either candidate access router discovery [ 4 ] or policy based mechanism [ 3 ]. Here our focus is on specific flows which requires interaction with middle-box entities or the entities which requires special services like VPN when handoff occurs across AS.  
         [0020]    In FIG. 1, MN  101  is currently in AS 1   150  and has ongoing session(s) with Content/cache server (CS)  103  and with Core Network (CN)  170 , which is outside the AS 1   150  system. Since CS  103  is also CN  170  the key difference is that the CS  103  and MN  101  endpoints are within AS 1   150  and may have site local address assignment and uses private address(es). To illustrate this scenario with an example, assume that AS 1   150  is centered on a Nokia office and mobile node  101  has two radio interfaces, a first one, which can talk to wireless LAN, and another interface is cellular interface. Currently the mobile node  101  (user) is having a session with the content server with in the office premise using the wireless LAN network interface. Since the MN  101  is inside the office there may not need for any security because they are administered and physically protected network. The moment when the user is leaving the office and entering outside world (say AS-2) the hand-off occurs between the wireless LAN network and cellular network. The session has to be protected by applying some VPN and other service specific attributes. In this example we have show AS building and vicinity) is surrounded by AS-2, but this type of scenario may happen across two Internet Service Providers (ISPs).  
         [0021]    Other information, like static capabilities of the MN  101  are stored in the AAA server  180 , the policy server  190  can retrieve this information from the AAA  180  server of the MN home network. In the following, we describe the problem of inter domain hand-off.  
         [0022]    For example, when the MN  101  is in the AS 1   150 , the static capabilities of the MN  101  are retrieved by PS 1   190  from AAA1 server  180  and dynamic capabilities (or negotiated profiles) are kept with the access router AR 1   185  that is currently serving the MN  101 . When the MN  101  moves toward AS 2   160 , it receives identification information on a broadcast channel, which may contain link layer information of BS 2   161  or IP address of AR 2   162  or Autonomous System (AS) number associating some link local address or any combination information. With these information the context transfer occurs between two AS. The context transfer does not cover how to create a pinhole and how to apply flow specific characteristics to the middle-box.  
         [0023]    Our proposal contains two steps, if the MN  101  has a ongoing session and whose endpoints lie with in AS 1   150 , that has to moved seamlessly without interrupting the application flow, this is done by creating a pin-hole in the middle-box for the ongoing session. Second both the CS  103  and MN  101  is to be informed through out-of-band signaling for those flows.  
         [0024]    [0024]FIG. 1 shows a reference architecture. During the context transfer process, both the policy servers know each other&#39;s NAT addresses. It is the responsibility of the policy server to figure out endpoint addresses of an ongoing session. For example if both the session endpoints lie in the same AS, the pinhole has to be created on the fly during the context transfer process.  
         [0025]    The sequence of operations performed by the policy server in an AS domain are as shown in FIG. 2.  
         [0026]    Message Flow in AS1 domain: For illustration purpose, we split the message exchanges into two parts, one that happens in the AS-1 routing domain and the other in the new AS-2 domain. FIG. 2 and FIG. 3 depicts exchange of messages before and after hand-off respectively.  
         [0027]    The sequences of message exchange in AS-1 before hand-off are as shown in FIG. 3. Content server or application server waits for a connection request from a client (See message—1).  
         [0028]    Client issues a connect system call  201 ; Both client and Server create a table entry, e.g. client table  220  and server table  230 . Client and Server perform normal read/write operations e.g. client read/write  203  and server read/write  233 .  
         [0029]    [0029]FIG. 2: Session between MN  101  and Content server before the hand-off.  
         [0030]    The sequences of message exchange in the AS-1 during hand-off are as follows:  
         [0031]    1. After the policy server  330  has identified the flow, which requires pinhole creation in the middlebox, policy server  330  sends a signalling message to the NAT device  320  with complete state information. This includes src-ip  311 , dst-ip  312 , src-port  313 , dst-port  314 , and other sliding window parameters  315 .  
         [0032]    NAT  320  creates an entry in the NAT table as if the session has been started and initializes the state variables. Also, if the session needs special services (e.g. VPN), then the additional service specific parameters are exchanged.  
         [0033]    NAT  320  also creates a session with the NAT/AS-2 during this process.  
         [0034]    2. Policy server  330  then forward the destination IP address of the AS NAT  321  to the Content server  340 .  
         [0035]    3. Content server  340  now updates the sock_entry table  350 .  
         [0036]    4. Now the packets from the application are directed through NAT  320  to the new AS-2  
         [0037]    Similar message flow happens in the AS-2 domain, where the policy server informs the NAT and also the mobile node.  
         [0038]    Although described in the context of particular embodiments, it will be apparent to those skilled in the art that a number of modifications and various changes to these teachings may occur. Thus, while the invention has been particularly shown and described with respect to one or more preferred embodiments thereof, it will be understood by those skilled in the art that certain modifications or changes, in form and shape, may be made therein without departing from the scope and spirit of the invention as set forth above and claimed hereafter.