Abstract:
The present invention supports a communication protocol for transmission of information packets between a mobile node and a virtual private network. Information packets are encapsulated and decapsulated along the route as the information packet is forwarded among the various networks on its path to the destination address; either the mobile node on a foreign network or a correspondence node on a virtual private network. A home agent on the virtual private network supports transmitting the information packets, and the information packets are transmitted from the virtual private network from the home agent or a virtual private network gateway.

Description:
RELATED APPLICATION DATA 
       [0001]    This application is related to Provisional Patent Application Ser. No. 60/426,786 filed on Nov. 15, 2002, and priority is claimed for this earlier filing under 35 U.S.C. §119(e), and this application is a continuation application of Utility patent application Ser. No. 12/879,964 filed Sep. 10, 2010, which is a continuation application of Utility patent application Ser. No. 10/712,879 filed on Nov. 13, 2003, and priority is claimed for this earlier filing under 35 U.S.C. §120. The Provisional Patent Application and prior Utility Patent Applications are incorporated by reference into this utility patent application. 
     
    
     TECHNICAL FIELD OF THE INVENTION 
       [0002]    A communication protocol for information packet transmissions from a Virtual Private Network in a mobile IP session. 
       BACKGROUND OF THE INVENTION 
       [0003]    The Internet, like so many other high tech developments, grew from research originally performed by the United States Department of Defense. In the 1960s, the military had accumulated a large collection of incompatible computer networks. Because of their incompatible data structures and transmission protocols, many of these computers could not communicate with other computers across network boundaries. 
         [0004]    In the 1960s, the Defense Department wanted to develop a communication system that would permit communication between these different computer networks. Recognizing that a single, centralized communication system would be vulnerable to attacks or sabotage, the Defense Department required that the communication system be decentralized with no critical services concentrated in vulnerable failure points. In order to achieve this goal, the Defense Department established a decentralized communication protocol for communication between their computer networks. 
         [0005]    A few years later, the National Science Foundation (NSF) wanted to facilitate communication between incompatible network computers at various research institutions across the country. The NSF adopted the Defense Department&#39;s protocol for communication, and this combination of research computer networks would eventually evolve into the Internet. 
       Internet Protocols 
       [0006]    The Defense Department&#39;s communication protocol governing data transmission between different networks was called the Internet Protocol (IP) standard. The IP standard has been widely adopted for the transmission of discrete information packets across network boundaries. In fact, the IP standard is the standard protocol governing communications between computers and networks on the Internet. 
         [0007]    The IP standard identifies the types of services to be provided to users and specifies the mechanisms needed to support these services. The IP standard also specifies the upper and lower system interfaces, defines the services to be provided on these interfaces, and outlines the execution environment for services needed in the system. 
         [0008]    A transmission protocol, called the Transmission Control Protocol (TCP), was developed to provide connection-oriented, end-to-end data transmission between packet-switched computer networks. The combination of TCP with IP (TCP/IP) forms a suite of protocols for information packet transmissions between computers on the Internet. The TCP/IP standard has also become a standard protocol for use in all packet switching networks that provide connectivity across network boundaries. 
         [0009]    In a typical Internet-based communication scenario, data is transmitted from an originating communication device on a first network across a transmission medium to a destination communication device on a second network. After receipt at the second network, the packet is routed through the network to a destination communication device. Because standard protocols are used in Internet communications, the IP protocol on the destination communication device decodes the transmitted information into the original information transmitted by the originating device. 
       TCP/IP Addressing and Routing 
       [0010]    A computer operating on a network is assigned a unique physical address under the TCP/IP protocols. This is called an IP address. The IP address can include: (1) a network ID and number identifying a network, (2) a sub-network ID number identifying a substructure on the network, and (3) a host ID number identifying a particular computer on the sub-network. A header data field in the information packet will include source and destination addresses. The IP addressing scheme imposes a consistent addressing scheme that reflects the internal organization of the network or sub-network. 
         [0011]    A router is used to regulate the transmission of information packets into and out of the computer network. Routers interpret the logical address contained in information packet headers and direct the information packets to the intended destination. Information packets addressed between computers on the same network do not pass through the router to the greater network, and as such, these information packets will not clutter the transmission lines of the greater network. If data is addressed to a computer outside the network, the router forwards the data onto the greater network. 
         [0012]    TCP/IP network protocols define how routers determine the transmission path through a network and across network boundaries. Routing decisions are based upon information in the IP header and corresponding entries in a routing table maintained on the router. A routing table contains the information for a router to determine whether to accept an information packet on behalf of a device or pass the information packet onto another router. 
         [0013]    Routing tables can be configured manually with routing table entries or with a dynamic routing protocol. A manual routing table can be configured upon initialization. In a dynamic routing protocol, routers update routing information with periodic information packet transmissions to other routers on the network. The dynamic routing protocol accommodates changing network topologies, network architecture, network structure, layout of routers, and interconnection between hosts and routers. 
       The IP-Based Mobility System 
       [0014]    The Internet protocols were originally developed with an assumption that Internet users would be connected to a single, fixed network. With the advent of cellular wireless communication systems, such as mobile communication devices, the movement of Internet users within a network and across network boundaries has become common. Because of this highly mobile Internet usage, the implicit design assumption of the Internet protocols (e.g. a fixed user location) is violated by the mobility of the user. 
         [0015]    In an IP-based mobile communication system, the mobile communication device (e.g. cellular phone, pager, computer, etc.) can be called a Mobile Node. Typically, a Mobile Node maintains connectivity to its home network through a foreign network. The Mobile Node will always be associated with its home network for IP addressing purposes and will have information routed to it by routers located on the home and foreign networks. The routers can be referred to by a number of names including Home Agent, Home Mobility Manager, Home Location Register, Foreign Agent, Serving Mobility Manager, Visited Location Register, and Visiting Serving Entity. 
         [0016]    While coupled to a foreign network, the Mobile Node will be assigned a care-of address. This is a temporary IP address assigned by the foreign network. The care-of address is used by routers on the foreign network to route information packets addressed to the Mobile Node. While residing on a foreign network, a Mobile Node may move from one location to another, changing its connectivity to the network. This movement changes the physical location of the Mobile Node and requires updating routing tables and/or care-of addressing to keep up with the movement of the Mobile Node. 
         [0017]    The Mobile Node keeps the Home Agent informed of its current location by registering a care-of address with the Home Agent. Essentially, the care-of address represents the current foreign network address where the Mobile Node is located. If the Home Agent receives an information packet addressed to the Mobile Node while the Mobile Node is located on a foreign network, the Home Agent will “tunnel” the information packet to the Mobile Node&#39;s current location on the foreign network via the applicable care-of address. In some system architectures and protocols, Foreign Agents also participate in transmission of information packets to a resident Mobile Node. Foreign Agents will receive information packets forwarded from the Home Agent to de-tunnel and forward to the Mobile Node. Further, the Foreign Agent serves as a default router for out-going information packets generated by the mobile node while connected to the foreign network. Foreign Agents and Home Agents can route information packets using successive transmission hops to route information packets from router-to-router to and from a Mobile Node. The registered care-of address identifies the location on a foreign network of the Mobile Node, and the Home Agent and Foreign Agent use this care-of address for routing information packets to and from the foreign network. 
       Virtual Private Networks 
       [0018]    A Virtual Private Network (VPN) emulates a private network over a shared physical infrastructure. By way of example, a VPN can reside within a local area network (LAN) system or on several different networks. A VPN can also span multiple computer systems. 
         [0019]    A VPN can be used to extend the communication capabilities of a corporate network to remote offices, which will support the use of the Internet, extranet, or dial-up services. In this way, connectivity to the VPN network is provided in the same manner as a dedicated private network, but there is no need to provide all the equipment and support infrastructure at a remote location. 
         [0020]    A service provider, or other network structure, provides the remote physical system and computer infrastructure within which the “virtual” VPN network resides. In this manner, the VPN can function much the same as a single, physical network even though there are intervening host infrastructures and communications traverse network boundaries. A number of different types of VPNs are suggested in RFC 2764, but this is by no means an exhaustive list of possible VPN constructs. The distinguishing hallmark of a VPN is a single, logical network found on a public or private computer infrastructure with the VPN residing upon one or more autonomous systems. Typically, VPN communication over the public infrastructure uses secured information packet transmission. 
       Tunneling and Secured Information Packet Transmission 
       [0021]    Tunneling is the basic methodology in IP communication by which an information packet is routed to the appropriate Internet node through an intermediate Internet address. To emulate the point-to-point connections of a private network, VPN methodology uses secure tunnels to handle information packet transmission across the public infrastructure. 
         [0022]    Typically, an information packet with network routing can be encapsulated with IP address information. Encapsulation involves adding an outer IP header to the original IP header fields. In this manner, a “tunnel” can be constructed. The outer IP header contains a source and destination IP address—the “endpoints” of the tunnel. The inner IP header source and destination addresses identify the original sender and destination addresses. 
         [0023]    The original sender and recipient addresses for the information packet remain unchanged after encapsulation, while the new “tunnel” endpoint addresses are appended onto the original information packet. This appended address information alters the original IP routing by delivering the information packet to an intermediate destination node (in mobile IP network, typically a foreign agent router), where the encapsulated information packet is “decapsulated” or “de-tunneled” yielding the original information packet. The packet is then delivered to the destination address found in the original IP address based on the associated routing table entries on network routers. 
         [0024]    The “tunnel” is established by encapsulating an information packet containing the original IP address of the mobile node (and payload data) and an IP source address with the intermediate routing IP address (i.e. care-of address) of the foreign network. In the more specialized application of VPNs, the tunnels can be secured by encryption and authentication protocols. These security protocols ensure integrity and confidentiality of information packet data transmission during a communication session. Encrypted information packet payloads are generally identified with an Encapsulated Security Payload Header (ESP), which contains data to provide confidentiality, data origin authentication, connectionless integrity, an anti-replay service (a form of partial sequence integrity), and limited traffic flow confidentiality services. 
         [0025]    By encapsulating the data with an IP header, an encrypted information packet can be routed securely over the public communication infrastructure between the foreign network, the mobile node, and the home network. During transit through the tunnel over the public communication infrastructure, the information packet data payload being transmitted is encrypted, and the encrypted data can only be deciphered using private encryption keys that permit the encryption algorithms at the mobile node and the correspondence node it is communicating with to decode the data as well as encrypt the data. A VPN gateway on the home network will usually perform encryption and decryption services at the boundary of the VPN or at the Correspondence Node. The foreign network or Mobile Node will decrypt or encrypt the information packet for communication with the home network. 
         [0026]    For Mobile IP to function in a VPN communication session, the methodology embodied by communication protocols must maintain communication connections. Implementation scenarios require a mobile host (e.g. Mobile Node) on a foreign network to maintain a secure communication link to a secured domain (e.g. a VPN). This emerging Mobile IP application within a VPN environment does not have an established communication protocol for maintaining secured information packet transmission between a roaming mobile node and its home VPN using a public infrastructure. There is a need for a communication protocol to transmit information packets between a Mobile Node and a VPN that offers flexibility. The invention simplifies and enhances the efficiency of communication between a MN and a VPN compared to other suggested methods. 
       SUMMARY OF THE INVENTION 
       [0027]    The invention is a communication protocol for maintaining a secure communication link between a mobile node and a correspondence node on a VPN using a public foreign network and communication infrastructure. A single home agent on the VPN supports communication between a correspondence node on the VPN and a mobile node linked to a public communication network. An interne key exchange (IKE) procedure is performed to setup private encryption keys for encryption and decryption of information packets on the VPN between a VPN gateway and the mobile node. 
         [0028]    Encrypted information packets are transmitted between the VPN gateway and the mobile node. Decrypted or non-encrypted information packets are routed between a correspondence node and the VPN gateway. Information packets transmitted between the mobile node and the correspondence node undergo successive encapsulation/decapsulation during routing. In the invention, no more than one home agent is required for communication. Also, optimized communication can take place without encapsulation/decapsulation at the home agent. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0029]    The objects and features of the invention will become more readily understood from the following detailed description and appended claims when read in conjunction with the accompanying drawings in which like numerals represent like elements and in which: 
           [0030]      FIG. 1  is a schematic diagram of an architecture for a mobile IP wireless communications network featuring a VPN on the home network using more than one home agent; 
           [0031]      FIG. 2  is a representation of an information packet; 
           [0032]      FIG. 3  a general representation of an original information packet and an encapsulated information packet used for tunneling; 
           [0033]      FIG. 4  is a schematic diagram of an architecture for a mobile IP wireless communications network featuring a VPN with a public home address for the mobile node using the invention; 
           [0034]      FIG. 5  is the encapsulation process of the information packet for the network of  FIG. 4  on the forward path; 
           [0035]      FIG. 5A  is the encapsulation process of the information packet for the network of  FIG. 4  on the reverse path; 
           [0036]      FIG. 6  is a schematic diagram of an architecture for a mobile IP wireless communications network featuring a VPN with a private home address for the mobile node using the invention; 
           [0037]      FIG. 7  is the encapsulation process of the information packet for the network of  FIG. 6  on the forward path; 
           [0038]      FIG. 7A  is the encapsulation process of the information packet for the network of  FIG. 6  on the reverse path; 
           [0039]      FIG. 7B  is the encapsulation process of the information packet for the network of  FIG. 6  on the reverse path using optimized communication that does not require decapsulation by the home agent; 
           [0040]      FIG. 8  is a schematic diagram of an architecture for a mobile IP wireless communications network featuring a VPN with a public home address for the mobile node and a foreign agent using the invention; 
           [0041]      FIG. 9  is the encapsulation process of the information packet for the network of  FIG. 8  on the forward path; 
           [0042]      FIG. 10  is a schematic diagram of an architecture for a mobile IP wireless communications network featuring a VPN with a private home address for the mobile node performing a hand-off from a first sub-network to a second sub-network on a foreign network using the invention; 
           [0043]      FIG. 11  is the encapsulation process of the information packet for the network of  FIG. 10  on the forward path; 
           [0044]      FIG. 12  is a schematic diagram of an architecture for a mobile IP wireless communications network featuring a VPN with a private home address for the mobile node performing a hand-off from a first sub-network to a second sub-network on a foreign network having a foreign agent using the invention; 
           [0045]      FIG. 13  is the encapsulation process of the information packet for the network of  FIG. 12  on the forward path; 
           [0046]      FIG. 14  is a schematic diagram of an architecture for a mobile IP wireless communications network featuring a VPN with a public home address for the mobile node using an optimized communication using the invention; 
           [0047]      FIG. 15  is the encapsulation process of the information packet for the network of  FIG. 14  on the forward path; and 
           [0048]      FIG. 16  is the encapsulation process of the information packet for the network of  FIG. 14  on the reverse path. 
       
    
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS 
       [0049]      FIG. 1  shows a suggested methodology for implementing mobile IP communication to a VPN different from the invention proposed by the Internet Engineering Taskforce. A foreign network  10  includes a Dynamic Host Configuration Protocol (DHCP) server  15 . The DHCP server  15  is connected to a buss line  33  by communication link  42 . A Mobile Node (MN)  30  is connected to the buss line  33  by communication link  43 . In a typical mobile IP application, the communication link  43  includes a wireless connection. The DHCP  15  and the MN  30  communicate using information packets transmitted over communication link  41 , the buss line  33 , and communication link  43 . 
         [0050]    A home network  50  for the MN  30  includes an exterior home agent (xHA)  55 . The xHA  55  connects to a buss line  53  by communication link  56 . A VPN gateway (VPN-GW)  60  connects to the buss line  53  by communication link  59 . The VPN-GW  60  is located on the boundary to a secrued domain—the VPN  80 —on the home network  50 . The VPN  60  is a security gateway that secures information packet transmission to and from the VPN  80 . The VPN-GW  60  connects to an inner home agent (iHA)  65  located within the VPN  80 . A correspondence node (CN)  70  connects to the iHA  65  using communication link  71 . 
         [0051]    The foreign network  10  and home network  50  transmit information packets back and forth using a communication link  40 . Communication link  40  connects buss line  33  and buss line  53 . Information packets routed between the MN  30  and the CN  70  use the xHA  55 , the VPN-GW  60 , and the iHA  65 . Encapsulating address headers steps are added at the iHA  65 , VPN-GW  60 , and xHA  55  on information packets transmitted between the CN  70  and the MN  30 . In this solution, two home agents are required. 
         [0052]    The general format of an information packet used on packet-based communication systems is shown in  FIG. 2 . Information packets use an encoding format of “1” and “0” data bits to build a data stream that a computer can interpret. The information packet  200  has header data  210  that includes an IP address header  220  providing routing instructions for transport over an IP communication system. The IP header  220  typically contains an IP source address  225  and an IP destination address  227 . Other header data types  228  can be included such as an Encryption Security Payload (ESP) header or User Datagram Protocol (UDP) header. The actual length and format of the IP address header  220  is dependent on the actual communication protocol being used (e.g. IPv4 or IPv6). The information packet  200  also contains a variable length data payload section  250  that contains the actual information being transmitted from the originating source to the destination source. 
         [0053]    The basic encapsulation sequence used to route information packets is shown in  FIG. 3 . The original information packet  300  contains an IP address header  310  that includes IP addresses for both the destination and the source of the information packet  300 . The data payload  320  is the actual data being transmitted. In encapsulation, an outer header  330  is added to the information packet  300 . This yields an encapsulated information packet  360  comprising an outer header  330  (typically an IP address) with the address for the tunnel entry and exit points, the IP Header  340  comprising the IP address of the destination and the source, and the payload data  350 . 
         [0054]      FIG. 4  shows one embodiment for the invention for communication between a foreign network and a VPN with a public home address for the MN. A public home address is an IP address that can be used from any IP-based communication network for Internet communication. An IP communication device connected to an IP network can communicate information packets using this public home address. 
         [0055]    A foreign network  405  includes a DHCP  410  server connected to a buss line  430  by communication link  411 . A MN  450  connects to the buss line  430  by communication link  451 . Communication link  451  for most mobile IP communication will include a wireless connection (e.g. cellular phone service connection), but in alternate embodiments this link may be a wired link with the MN  450  using some type of user plug-in connector (e.g. laptop computer through a phone modem). 
         [0056]    The foreign network  405  is connected to the MN&#39;s  450  home network  480  by communication link  433 . Communication link  433  connects the buss line  430  to a buss line  440  on the home network  480 . Communication link  441  links a VPN-GW  460  to the buss line  440 . The VPN-GW  460  is a security gateway encrypting and decrypting information packets to and from a VPN  475  organized on the HN  480 . The VPN  475  includes a HA  465  connected to the VPN-GW  460  by communication link  461 , and a CN  470  connected to the HA  465  by communication link  471 . The HA  465  also has a communication link  466  connected to buss line  440 . 
         [0057]    In this embodiment, a public home address (HOA) designates the IP address of the MN  450 . The VPN-GW  460  possesses an IP address (IP-VPN) designation. The HA  465  also possesses an IP address (HAIP) designation, and the CN  470  has an IP address (CNIP). During a registration procedure at the start of a communication session, a colocated care-of IP address is also assigned to the MN  450  by the DHCP  410  corresponding to the IP address location of the MN  450  on the foreign network  405  that is used to route information packets from the VPN  475  on the home network  480 . 
         [0058]      FIG. 5  shows the encapsulation process for the invention of the network configuration of  FIG. 4  for information packets transmitted from the correspondence node to the mobile node on the forward path. At communication startup, the MN  450  initiates a registration protocol to obtain a colocated care-of address on the foreign network  405  from the DHCP  410 . The HA  465  sets up a VPN tunnel with the VPN-GW  460  by registering a routing table association for the HOA and a VPN tunnel inner address (VPN-TIA) to use for tunneling information packets to the MN  450 . The colocated care-of address (CCOA) is also registered in a routing table association with the public home address designation (HOA) for the MN  450  on the HA  465 . 
         [0059]    Additionally, the VPN-GW  460  and the MN  450  perform internet key exchange (IKE) negotiations to exchange encryption keys, methods, and authentication information. This information is used by the security protocol to encrypt the information packet. Acceptable security algorithms for the key exchange include Message Digest 5 (MD5), Secure Hash Algorithm (SHA), and a Diffie-Hellman combination algorithm using a public and private encryption key. A number of encryption algorithms may be available, including Data Encryption Standard (DES), Triple Data Encryption Standard (3DES), Rivest-Shamir-Aldeman (RSA), ElGamal, RC2 and RC4. 
         [0060]    The HA  465  also sets up a VPN tunnel with the VPN-GW  460  to register an association for the HOA and a VPN tunnel inner address (VPN-TIA) to use for tunneling information packets to the MN  450 . This VPN-TIA can be setup during IKE negotiations, assigned manually, or by some other means. After this registration and initialization protocol, communication can occur between the MN  450  and the CN  470 . 
         [0061]    The first information packet  505  is transmitted from the CN  470  to the HA  465 . The CNIP  506  is the IP address for the CN  470  and is the source IP address for the information packet  505 . The destination IP address HOA  507  is the home address designation of the MN  450 . The payload data  508  in the information packet  505  is the actual information being transmitted. At the HA  465 , the HA  465  examines its routing table associations to determine where to forward the information packet  505 . From the information in the routing table and routing algorithm, the HA  465  encapsulates the information packet  505  to form information packet  510  for routing to the VPN  460  by appending a new source and destination IP address. 
         [0062]    The information packet  510  is transmitted from the HA  465  to the VPN-GW  460  using communication link  461 . The HAIP  511  is the IP address for the HA  465  or source IP address. The destination address VPN-TIA  512  is the tunnel inner address for the VPN-GW  460  used to route information packets transmitted within the VPN  475  to the VPN-GW  460 . The CNIP  513  and HOA  514  are the original source and destination IP address respectively and remain unchanged as does the data payload  515  compared to the CNIP  506 , HOA  507 , and data payload  508 . 
         [0063]    At the VPN-GW  460 , the information packet  510  is encrypted and an ESP  523  header added. The encrypted information packet  510  is then encapsulated to form the third information packet  520 . Information packet  520  includes the new source IP address IP-VPN  521 , which is the IP address for the VPN-GW  460 . The new destination IP address HOA  522  is the IP address for the MN  450  on the VPN  480 . The ESP  523  contains security protocol data. The HAIP  524 , VPN-TIA  525 , CNIP  526 , HOA  527 , and payload data  528  are encrypted, but otherwise remain unchanged from the HAIP  511 , VPN-TIA  512 , CNIP  513 , HOA  514 , and payload data  515  in information packet  510 . 
         [0064]    The information packet  520  is transmitted from the VPN-GW  460  back to the HA  465 . The HA  465  again examines its routing tables entries for an association for the destination address HOA  522 . The HA  465  then encapsulates information packet  520  to form the fourth information packet  530 . A new source IP address HAIP  531 , corresponding to the IP address for HA  465 , is appended. A new destination IP address CCOA  532 , corresponding to the colocated IP address of the MN  450 , is also appended. The IP-VPN  533 , HOA  534 , ESP  535 , HAIP  536 , VPN-TIA  537 , CNIP  538 , HOA  539 , and payload data  540  remain unchanged compared to the IP-VPN  521 , HOA  522 , ESP  523 , HAIP  524 , VPN-TIA  525 , CNIP  526 , HOA  527 , and payload data  528  of information packet  520 . This secured information packet  530  is then transmitted to the MN  450 , which decapsulates and decrypts the information packet  530  to recover the original information. 
         [0065]      FIG. 5A  shows the encapsulation process for the invention of the network configuration of  FIG. 4  for information packets transmitted from the mobile node to the correspondence node on the reverse path. Information packet  550  is formed by MN  450  for transmission to the CN  470 . HOA  551  is the source IP address for the MN  450  on the home network  480  within the VPN  475 . The IP-VPN  552  is the destination address for the VPN-GW  460  securing the VPN  475 . ESP  553  contains data to provide confidentiality and signifies that the remaining portion of information packet  550  is encrypted. The VPN-TIA  554  is the address for the VPN tunnel inner address for the VPN  460  used in the VPN  475 . The CNIP  555  is the IP address for CN  470 . HOA  556  is the public home address for the MN  450  on the VPN  475  and the ultimate source address, and the CNIP  557  is the IP address for the CN  470  and the ultimate destination address for the information packet  550 . The data payload  558  is the data actually being transmitted to the CN  470 . 
         [0066]    Information packet  550  is received at the destination VPN-GW  460  and decaspulated to reveal the encrypted information packet  560  with the ESP  553  header appended. The ESP  553  is processed and the information packet  560  decrypted. The VPN-TIA  561  is the VPN tunnel inner address for the VPN  460  and is the source address for the information packet  560 . The CNIP  562  is the destination address for the CN  470  on the VPN  475 . The HOA  563  is the public home address for the MN  450  and the ultimate source address, and the CNIP  564  is the IP address for the CN  470  and the ultimate destination address for the information packet  560 . The data payload packet  565  is the data actually being transmitted to the CN  470 . 
         [0067]    The VPN-GW  460  forwards the information packet  560  to the HA  465 . The HA  465  decapsulates the information packet  560  to form information packet  570 . The information packet  570  includes the source IP address HOA  571 , the destination IP address CNIP  572 , and the data payload  573 . The CN  470  receives the information packet  570  and decapsulates it to reveal the data payload  573  which can then be processed by the CN  470 . 
         [0068]      FIG. 6  shows an embodiment for the invention for communication between a foreign network and a VPN with a private home address for the MN. A private home address is an IP address that can only be used within a specific sub-network. 
         [0069]    A foreign network  605  includes a DHCP  610  server connected to a buss line  630  by communication link  611 . A MN  650  connects to the buss line  630  by communication link  651 . Communication link  651  for most mobile IP communication will include a wireless connection (e.g. cellular phone service connection), but in alternate embodiments this link may be a wired link with the MN  650  using some type of user plug-in connector (e.g. laptop computer through a phone modem). 
         [0070]    The foreign network  605  is connected to the MN&#39;s  650  home network  680  by communication link  633 . Communication link  633  connects the buss line  630  to a VPN-GW  660  on the home network  680 . The VPN-GW  660  is a security gateway encrypting and decrypting information packets to and from a VPN  675  organized on the HN  680 . The VPN  675  includes a HA  665  connected to the VPN-GW  660  by communication link  661 , and a CN  670  connects to the HA  665  by communication link  671 . 
         [0071]    In this preferred embodiment, a private home address (HOA) designates the IP address of the MN  650 . The VPN-GW  660  possesses an IP address (IP-VPN) designation. The HA  665  also possesses an IP address (HAIP) designation, and the CN  670  has an IP address (CNIP). During a registration procedure at the start of a communication session, a colocated care-of IP address is also assigned to the MN  650  by the DHCP  610  corresponding to the IP address location of the MN  650  on the foreign network  605  that is used to route information packets from the VPN  675  on the home network  680 . 
         [0072]      FIG. 7  shows the encapsulation process for the invention of the network configuration of  FIG. 6  for communication from the CN to the MN on the forward path. At communication startup, the MN  650  initiates a registration protocol to obtain a colocated care-of address on the foreign network  605  from the DHCP  610 . The HA  665  sets up a VPN tunnel with the VPN-GW  660  by registering a routing table association for the HOA and a VPN tunnel inner address (VPN-TIA) to use for tunneling information packets to the MN  650 . The colocated care-of address (CCOA) is also registered in a routing table association with private home address designation (HOA) for the MN  650  on the HA  665 . 
         [0073]    Additionally, the VPN-GW  660  and the MN  650  perform internet key exchange (IKE) negotiations to exchange encryption keys, methods, and authentication information. This information is used by the security protocol to encrypt the information packet. Acceptable security algorithms for the key exchange include Message Digest 5 (MD5), Secure Hash Algorithm (SHA), and a Diffie-Hellman combination algorithm using a public and private encryption key. A number of encryption algorithms may be available, including Data Encryption Standard (DES), Triple Data Encryption Standard (3DES), Rivest-Shamir-Aldeman (RSA), ElGamal, RC2 and RC4. 
         [0074]    The HA  665  also sets up a VPN tunnel with the VPN-GW  660  to register an association for the HOA and a VPN tunnel inner address (VPN-TIA) to use for tunneling information packets to the MN  650 . This VPN-TIA can be setup during IKE negotiations, assigned manually, or by some other means. After this registration and initialization protocol, communication can occur between the MN  650  and the CN  670 . 
         [0075]    The first information packet  705  is transmitted from the CN  670  to the HA  665 . The CNIP  706  is the IP address for the CN  670  and is the source IP address for the information packet  705 . The destination IP address HOA  707  is the home address designation of the MN  650 . The payload data  708  in the information packet  705  is the actual information being transmitted. At the HA  665 , the HA  665  examines its routing table associations to determine where to forward the information packet  705 . From information in the routing table and routing algorithm, the HA  665  encapsulates the information packet  705  to form information packet  710  for routing to the VPN-GW  660  by appending a new source and destination IP address. 
         [0076]    The information packet  710  is transmitted from the HA  665  to the VPN-GW  660  using communication link  661 . The HAIP  711  is the IP address for the HA  665  or source IP address. The destination address VPN-TIA  712  is the tunnel inner address for the VPN-GW  660  used to route information packets transmitted within the VPN  675  to the VPN-GW  660 . The CNIP  713  and HOA  714  are the original source and destination IP address respectively and remain unchanged as does the data payload  715  compared to the CNIP  706 , HOA  707 , and data payload  708 . 
         [0077]    At the VPN-GW  660 , the information packet  710  is encrypted and an ESP  723  header added. The encrypted information  710  is then encapsulated to form the third information packet  720 . Information packet  720  includes the new source IP address IP-VPN  721 , which is the IP address for the VPN-GW  660 . The new destination IP address CCOA  722  is the IP address for the MN  650  on the foreign network  605 . The ESP  723  contains security protocol data. The HAIP  724 , VPN-TIA  725 , CNIP  726 , HOA  727 , and payload data  728  are encrypted, but otherwise remain unchanged from the HAIP  711 , VPN-TIA  712 , CNIP  713 , HOA  714 , and payload data  715  in information packet  710 . The information packet  720  is then transmitted from the VPN-GW  660  to the MN  650  on the foreign network  605 . The MN  650  processes the secured information packet  720  to decapsulate and decrypt the information packet  720  to recover the original information. 
         [0078]      FIG. 7A  shows an encapsulation process for the invention of the network configuration of  FIG. 6  for information packets transmitted from the mobile node to the correspondence node on the reverse path. Information packet  780  is formed by MN  650  for transmission to the CN  670 . CCOA is the colocated care-of source IP address for the MN  650  associated with the home address of the MN  650  in the routing table of the HA  665  on the home network  680  within the VPN  675 . The IP-VPN  752  is the destination address for the VPN-GW  660  securing the VPN  675 . ESP  753  contains data to provide confidentiality and signifies that the remaining portion of information packet  750  is encrypted. The VPN-TIA  754  is the address for the VPN tunnel inner address for the VPN  660  used in the VPN  675 . The CNIP  755  is the IP address for CN  670 . HOA  756  is the private home address for the MN  650  on the VPN  675  and the ultimate source address, and the CNIP  757  is the IP address for the CN  670  and the ultimate destination address for the information packet  750 . The data payload  758  is the data actually being transmitted to the CN  670 . 
         [0079]    Information packet  750  is received at the destination VPN-GW  660  and decaspulated to reveal the encrypted information packet  760  with the ESP  753  header appended. The ESP  753  is processed and the information packet  760  decrypted. The VPN-TIA  761  is the VPN tunnel inner address for the VPN  660  and is the source address for the information packet  760 . The CNIP  762  is the destination address for the CN  670  on the VPN  675 . The HOA  763  is the private home address for the MN  650  and the ultimate source address, and the CNIP  764  is the IP address for the CN  670  and the ultimate destination address for the information packet  760 . The data payload packet  765  is the data actually being transmitted to the CN  670 . 
         [0080]    The VPN-GW  660  forwards the information packet  760  to the HA  665 . The HA  665  decapsulates the information packet  760  to form information packet  770 . The information packet  770  includes the source IP address HOA  771  (e.g. the MN  650 ), the destination IP address CNIP  572  (e.g. the CN  670 ), and the data payload  573 . The CN  670  receives the information packet  770 , decapsulates it to reveal the data payload  573 , and then processes the data payload  573 . 
         [0081]      FIG. 7B  shows an encapsulation process for the invention of the network configuration of  FIG. 6  for information packets for an optimized transmission compared to that shown in  FIG. 7A  from the mobile node to the correspondence node on the reverse path. In this optimization, the information packet is routed to the destination address from the VPN-GW  660 . The information packet  780  is formed by MN  650  for transmission to the CN  670 . CCOA  781  is the colocated care-of source IP address for the MN  650  location at the foreign network  605 . The IP-VPN  782  is the destination address for the VPN-GW  660  securing the VPN  675 . ESP  783  contains data to provide confidentiality and signifies that the remaining portion of information packet  780  is encrypted. The HOA  784  is the private home address for the MN  650  on the VPN  675  and the ultimate source address, and the CNIP  785  is the IP address for the CN  670  and the ultimate destination address for the information packet  780 . The data payload  786  is the data actually being transmitted to the CN  670 . 
         [0082]    Information packet  780  is received at the destination VPN-GW  660  and decaspulated to reveal the encrypted information packet  790  with the ESP  783  header appended. The ESP  783  is processed and the information packet  780  decrypted. The HOA  791  is the private home address for the MN  650  and the ultimate source address, and the CNIP  792  is the IP address for the CN  670  and the ultimate destination address for the information packet  790 . The data payload packet  793  is the data actually being transmitted to the CN  670 . The VPN-GW  660  forwards the information packet  790  to the CN  670  without the information packet being processed by the HA  665 . The CN  670  receives the information packet  770 , decapsulates it to reveal the data payload  573 , and then processes the data payload  573 . 
         [0083]      FIG. 8  shows an embodiment for the invention for communication between a foreign network and a VPN with a public home address for the MN and a care-of address for the MN on a foreign agent. A public home address is an IP address that can be used from any IP-based communication network for Internet communication. An IP communication device connected to an IP network can communicate information packets using this public home address. 
         [0084]    A foreign network  805  includes a DHCP  810  server connected to a buss line  830  by communication link  811 . A foreign agent  820  also connects to the buss line  830  by communication link  821 . A MN  850  connects to the foreign agent  820  by communication link  851 . Communication link  851  for most mobile IP communication will include a wireless connection (e.g. cellular phone service connection), but in alternate embodiments this link may be a wired link with the MN  850  using some type of user plug-in connector (e.g. laptop computer through a phone modem). 
         [0085]    The foreign network  805  connects to the MN&#39;s  850  home network  880  by communication link  833 . Communication link  833  connects the buss line  830  to a buss line  840  on the home network  880 . Communication link  841  links a VPN-GW  860  to the buss line  840 . The VPN-GW  860  is a security gateway encrypting and decrypting information packets to and from a VPN  875  organized on the FIN  880 . The VPN  875  includes a HA  865  connected to the VPN-GW  860  by communication link  861 , and a CN  870  connects to the HA  865  by communication link  871 . The HA  865  also has a communication link  866  connected to buss line  841 . 
         [0086]    In this preferred embodiment, a public home address (HOA) designates the IP address of the MN  850 , which is assigned a foreign agent care-of address (FCOA) corresponding to the location of the MN  850  connection to the foreign network  805 . The VPN-GW  860  possesses an IP address (IP-VPN) designation. The HA  865  also possesses an IP address (HAIP) designation, and the CN  870  has an IP address (CNIP). During a registration procedure at the start of a communication session, a foreign agent care-of IP address (FCOA) is assigned to the MN  850  by the DHCP  810  or the FA  820  corresponding to the IP address location of the MN  850  on the foreign network  805  used to route information packets from the VPN  875 . 
         [0087]      FIG. 9  shows the encapsulation process for the invention of the network configuration of  FIG. 8  on the reverse communication path. At communication startup, the MN  850  initiates a registration protocol to obtain a foreign agent care-of address on the foreign network  805  from the DHCP  810  or the foreign agent  850 . The HA  865  sets up a VPN tunnel with the VPN-GW  860  by registering a routing table association for the HOA and a VPN tunnel inner address (VPN-TIA) to use for tunneling information packets to the MN  850 . The FCOA is also registered in a routing table association with public home address designation (HOA) for the MN  850  on the HA  865 . 
         [0088]    Additionally, the VPN-GW  860  and the MN  850  perform internet key exchange (IKE) negotiations to exchange encryption keys, methods, and authentication information. This information is used by the security protocol to encrypt the information packet. Acceptable security algorithms for the key exchange include Message Digest 5 (MD5), Secure Hash Algorithm (SHA), and a Diffie-Hellman combination algorithm using a public and private encryption key. A number of encryption algorithms may be available, including Data Encryption Standard (DES), Triple Data Encryption Standard (3DES), Rivest-Shamir-Aldeman (RSA), ElGamal, RC2 and RC4. 
         [0089]    The HA  865  also sets up a VPN tunnel with the VPN-GW  860  to register an association for the HOA and a VPN tunnel inner address (VPN-TIA) to use for tunneling information packets to the MN  850 . This VPN-TIA can be setup during IKE negotiations, assigned manually, or by some other means. After this registration and initialization protocol, communication can occur between the MN  850  and the CN  870 . 
         [0090]    The first information packet  905  is transmitted from the CN  870  to the HA  865 . The CNIP  906  is the IP address for the CN  870  and is the source IP address for the information packet  905 . The destination IP address HOA  907  is the home address designation of the MN  850 . The payload data  908  in the information packet  905  is the actual information being transmitted. At the HA  865 , the HA  865  examines its routing table associations to determine where to forward the information packet  905 . From the information in the routing table and routing algorithm, the HA  865  encapsulates the information packet  905  to form information packet  910  for routing to the VPN-GW  860  by appending a new source and destination IP address. 
         [0091]    The information packet  910  is transmitted from the HA  865  to the VPN-GW  860  using communication link  861 . The HAIP  911  is the IP address for the HA  865  or source IP address. The destination address VPN-TIA  912  is the tunnel inner address for the VPN-GW  860  used to route information packets transmitted within the VPN  875  to the VPN-GW  860 . The CNIP  913  and HOA  914  are the original source and destination IP address respectively and remain unchanged as does the data payload  915  compared to the CNIP  906 , HOA  907 , and data payload  908 . 
         [0092]    At the VPN-GW  860 , the information packet  910  is encrypted and an ESP  923  header appended. The encrypted information packet  910  is then encapsulated to form the third information packet  920 . Information packet  920  includes the new source IP address IP-VPN  921 , which is the IP address for the VPN-GW  860 . The new destination IP address HOA  922  is the IP address for the MN  850  on the VPN  880 . The ESP  923  contains security protocol data. The HAIP  924 , VPN-TIA  925 , CNIP  926 , HOA  927 , and payload data  928  are encrypted, but otherwise remain unchanged from the HAIP  911 , VPN-TIA  912 , CNIP  913 , HOA  914 , and payload data  915  in information packet  910 . 
         [0093]    The information packet  920  is transmitted from the VPN-GW  860  back to the HA  865 . The HA  865  again examines its routing table entries for an association for the destination address HOA  922 . The HA  865  then encapsulates information packet  920  to form the fourth information packet  930 . A new source IP address HAIP  931 , corresponding to the IP address for HA  865 , is appended. A new destination IP address FCOA  932 , corresponding to the foreign agent IP address of the MN  850 , is also appended. The IP-VPN  933 , HOA  934 , ESP  935 , HAIP  936 , VPN-TIA  937 , CNIP  938 , HOA  939 , and payload data  940  remain unchanged compared to the IP-VPN  921 , HOA  922 , ESP  923 , HAIP  924 , VPN-TIA  925 , CNIP  926 , HOA  927 , and payload data  928  of information packet  920 . This secured information packet  930  is then transmitted to the FA  820  for forwarding to the MN  850 , which decapsulates and decrypts the information packet  930  to recover the original information. 
         [0094]      FIG. 10  shows an embodiment for the invention for communication between a foreign network and a VPN with a private home address for the MN performing a hand-off from a first sub-network to a second sub-network on the foreign network. A private home address is an IP address that can only be used within a specific sub-network. 
         [0095]    A foreign network  1005  includes two sub-networks. The first sub-network  1044  includes a Local Home Agent (LHA)  1040  routing information packets to a first location for a MN  1050 ′ over communication link  1052 . The second sub-network  1042  includes a DHCP  1010  server connected to a buss line  1030  by communication link  1011 . A MN  1050  connects to the buss line  1030  by communication link  1051 , which is the MN  1050  new location after a hand-off is performed. Communication link  1051  and communication link  1052  will include a wireless connection (e.g. cellular phone service connection). A communication link  1031  connects the LHA  1040  on the first sub-network to the buss line  1030  of the second sub-network on the foreign network  1005 . 
         [0096]    The foreign network  1005  connects to the MN&#39;s  1050  home network  1080  by communication link  1033  from the LHA  1040  to a VPN-GW  1060  on the home network  1080 . The VPN-GW  1060  is a security gateway encrypting and decrypting information packets to and from a VPN  1075  organized on the HN  1080 . The VPN  1075  includes a HA  1065  connected to the VPN-GW  1060  by communication link  1061 , and a CN  1070  connected to the HA  1065  by communication link  1071 . 
         [0097]    In this preferred embodiment, a private home address (HOA) designates the IP address of the MN  1050 . The VPN-GW  1060  possesses an IP address (IP-VPN) designation. The HA  1065  also possesses an IP address (HAIP) designation, and the CN  1070  has an IP address (CNIP). During a registration procedure at the start of a communication session, a colocated care-of IP address is also assigned to the MN  1050 ′ by the LHA  1040  or a DHCP (not shown) corresponding to the IP address location of the MN  1050 ′ on the sub-network  1044  that is used to route information packets from the VPN  1075  on the home network  1080 . During a hand-off procedure when shifting from MN  1050 ′ to MN  1050 , a colocated care-of IP address is assigned to the MN  1050  by the DHCP  1010  corresponding to the IP address location of the MN  1050  on the sub-network  1042  that is used to route information packets from the sub-network  1044 . 
         [0098]      FIG. 11  shows the encapsulation process for the invention of the network configuration of  FIG. 12 . At communication startup, the MN  1050 ′ initiates a registration protocol to obtain a colocated care-of address on the sub-network  1044  from the LHA  1040 . The HA  1065  sets up a VPN tunnel with the VPN-GW  1060  by registering a routing table association for the HOA and a VPN tunnel inner address (VPN-TIA) to use for tunneling information packets to the MN  1050 ′. The colocated care-of address (CCOA) is also registered in a routing table association with private home address designation (HOA) for the MN  1050 ′ on the HA  1065 . 
         [0099]    Additionally, the VPN-GW  1060  and the MN  1050 ′ perform internet key exchange (IKE) negotiations to exchange encryption keys, methods, and authentication information. This information is used by the security protocol to encrypt the information packet. Acceptable security algorithms for the key exchange include Message Digest 5 (MD5), Secure Hash Algorithm (SHA), and a Diffie-Hellman combination algorithm using a public and private encryption key. A number of encryption algorithms may be available, including Data Encryption Standard (DES), Triple Data Encryption Standard (3DES), Rivest-Shamir-Aldeman (RSA), ElGamal, RC2 and RC4. 
         [0100]    The HA  1065  also sets up a VPN tunnel with the VPN-GW  1060  to register an association for the HOA and a VPN tunnel inner address (VPN-TIA) to use for tunneling information packets to the MN  1050 ′. This VPN-TIA can be setup during IKE negotiations, assigned manually, or by some other means. The LHA  1040  routes information packets to the MN  1050 ′. After this registration and initialization protocol, communication can occur between the MN  1050 ′ and the CN  1070 . 
         [0101]    During communication, the MN  1050 ′ changes its connection to a new subnetwork  1042  on the foreign network  1005 . During hand-off registration, the LHA  1040  registers an association for the prior or old CCOA (OCCOA) and the new CCOA (NCCOA) where the MN  1050  connects in a routing table. The LHA  1040  routes received information packets addressed to the OCCOA to the NCCOA for the MN  1050  during the communication session. 
         [0102]    The first information packet  1105  is transmitted from the CN  1070  to the HA  1065 . The CNIP  1106  is the IP address for the CN  1070  and is the source IP address for the information packet  1105 . The destination IP address HOA  1107  is the home address designation of the MN  1050 . The payload data  1108  in the information packet  1105  is the actual information being transmitted. At the HA  1065 , the HA  1065  examines its routing table associations to determine where to forward the information packet  1105 . From information in the routing table and routing algorithm, the HA  1065  encapsulates the information packet  1105  to form information packet  1110  for routing to the VPN-GW  1060  by appending a new source and destination IP address. 
         [0103]    The information packet  1110  is transmitted from the HA  1065  to the VPN-GW  1060  using communication link  1061 . The HAIP  1111  is the IP address for the HA  1065  or source IP address. The destination address VPN-TIA  1112  is the tunnel inner address for the VPN-GW  1060  used to route information packets transmitted within the VPN  1075  to the VPN-GW  1060 . The CNIP  1113  and HOA  1114  are the original source and destination IP address respectively and remain unchanged as does the data payload  1115  compared to the CNIP  1106 , HOA  1107 , and data payload  1108 . 
         [0104]    At the VPN-GW  1060 , the information packet  1110  is encrypted and an ESP  1123  header added. The encrypted information packet  1110  is then encapsulated to form the third information packet  1120 . Information packet  1120  includes the new source IP address IP-VPN  1121 , which is the IP address for the VPN-GW  1060 . The new destination IP address OCCOA  1122  is the old IP address for the MN  1050 ′ on the foreign network  1005  before changing to MN  1050 . The ESP  1123  contains security protocol data. The HAIP  1124 , VPN-TIA  1125 , CNIP  1126 , HOA  1127 , and payload data  1128  are encrypted, but otherwise remain unchanged from the HAIP  1111 , VPN-TIA  1112 , CNIP  1113 , HOA  1114 , and payload data  1115  in information packet  1110 . The information packet  1120  is then transmitted from the VPN-GW  1060  to the LHA  1040  at the old colocated care-of address (OCCOA  1122 ) for the MN  1050 ′. 
         [0105]    At the LHA  1040 , the LHA  1040  examines its routing table associations for the OCCOA  1122  to determine the destination address at the new CCOA (NCCOA)  1132 . The LHA  1040  then encapsulates information packet  1120  to form the fourth information packet  1130 . A new source IP address IP-LHA  1131 , corresponding to the IP address for LHA  1040 , is appended. A new destination IP address NCCOA  1132 , corresponding to the new colocated IP address of the MN  1050 , is also appended. Except for the encryption, the IP-VPN  1133 , OCCOA  1134 , ESP  1135 , HAIP  1136 , VPN-TIA  1137 , CNIP  1138 , HOA  1139 , and payload data  1140  remain unchanged compared to the IP-VPN  1121 , OCCOA  1122 , ESP  1123 , HAIP  1124 , VPN-TIA  1125 , CNIP  1126 , HOA  1127 , and payload data  1128  of information packet  1120 . This secured information packet  1130  is then transmitted to the MN  1050 , which decapsulates and decrypts the information packet  1130  to recover the original information. 
         [0106]      FIG. 12  shows an embodiment for the invention for communication between a foreign network and a VPN with a private home address for the MN performing a hand-off from a first sub-network to a second sub-network having a foreign agent. A private home address is an IP address that can only be used within a specific sub-network (e.g. a VPN). 
         [0107]    A foreign network  1205  includes two sub-networks. The first sub-network  1204  includes a Local Home Agent (LHA)  1240  routing information packets to a first location for a MN  1250 ′ over communication link  1252 . The second sub-network  1242  includes a DHCP  1210  server connected to a buss line  1230  by communication link  1211 . A foreign agent (FA)  1235  connects to the buss line  1230  by communication link  1212 . A MN  1250  connects to the buss line  1230  by communication link  1251 , which is the MN  1250 ′ new location requiring a hand-off Communication link  1251  and communication link  1252  for most mobile IP communication will include a wireless connection (e.g. cellular phone service connection). A communication link  1231  connects the LHA  1240  on the first sub-network to the buss line  1230  of the second sub-network on the foreign network  1205 . 
         [0108]    The foreign network  1205  connects to the MN&#39;s  1250  home network  1280  by communication link  1233  from the LHA  1240  to a VPN-GW  1260  on the home network  1280 . The VPN-GW  1260  is a security gateway encrypting and decrypting information packets to and from a VPN  1275  organized on the HN  1280 . The VPN  1275  includes a HA  1265  connected to the VPN-GW  1260  by communication link  1261 , and a CN  1270  connected to the HA  1265  by communication link  1271 . 
         [0109]    In this preferred embodiment, a private home address (HOA) designates the IP address of the MN  1250 . The VPN-GW  1260  possesses an IP address (IP-VPN) designation. The HA  1265  also possesses an IP address (HAIP) designation, and the CN  1270  has an IP address (CNIP). During a registration procedure at the start of a communication session, a colocated care-of IP address is also assigned to the MN  1250 ′ by the LHA  1240  or a DHCP (not shown) corresponding to the IP address location of the MN  1250 ′ on the sub-network  1244  that is used to route information packets from the VPN  1275  on the home network  1280 . During a hand-off procedure when shifting from MN  1250 ′ to MN  1250 , a colocated care-of IP address is assigned to the MN  1250  by the DHCP  1210  or the FA  1235  corresponding to the IP address location of the MN  1250  on the subnetwork  1242  that is used to route information packets from the sub-network  1244 . 
         [0110]      FIG. 13  shows the encapsulation process for the invention of the network configuration of  FIG. 12  for the forward path. At communication startup, the MN  1250 ′ initiates a registration protocol to obtain a colocated care-of address on the sub-network  1244  from the LHA  1240 . The HA  1265  sets up a VPN tunnel with the VPN-GW  1060  by registering a routing table association for the HOA and a VPN tunnel inner address (VPN-TIA) to use for tunneling information packets to the MN  1250 ′. The colocated care-of address (CCOA) is also registered in a routing table association with private home address designation (HOA) for the MN  1250 ′ on the HA  1265 . 
         [0111]    Additionally, the VPN-GW  1260  and the MN  1250 ′ perform interne key exchange (IKE) negotiations to exchange encryption keys, methods, and authentication information. This information is used by the security protocol to encrypt the information packet. Acceptable security algorithms for the key exchange include Message Digest 5 (MD5), Secure Hash Algorithm (SHA), and a Diffie-Hellman combination algorithm using a public and private encryption key. A number of encryption algorithms may be available, including Data Encryption Standard (DES), Triple Data Encryption Standard (3DES), Rivest-Shamir-Aldeman (RSA), ElGamal, RC2 and RC4. 
         [0112]    The HA  1265  also sets up a VPN tunnel with the VPN-GW  1260  to register an association for the HOA and a VPN tunnel inner address (VPN-TIA) to use for tunneling information packets to the MN  1250 ′. This VPN-TIA can be setup during IKE negotiations, assigned manually, or by some other means. The LHA  1240  routes information packets to the MN  1250 ′. After this registration and initialization protocol, communication can occur between the MN  1250 ′ and the CN  1270 . 
         [0113]    During communication, the MN  1250 ′ changes its connection to a new subnetwork  1242  on the foreign network  1205  with a foreign agent  1235 . During hand-off registration, the LHA  1240  registers an association for the prior or old CCOA (OCCOA) and the new foreign agent care-of address where the MN  1250  connects. The foreign agent (FA)  1235  or DHCP  1210  assigns a care-of address location for use to route information packets. The LHA  1240  routes information packets addressed to the OCCOA (e.g. the MN  1250 ′ location) to the FA  1235  to forward to the MN  1250  during the communication session. 
         [0114]    The first information packet  1305  is transmitted from the CN  1270  to the HA  1265 . The CNIP  1306  is the IP address for the CN  1270  and is the source IP address for the information packet  1305 . The destination IP address HOA  1307  is the home address designation of the MN  1250 . The payload data  1308  in the information packet  1305  is the actual information being transmitted. At the HA  1265 , the HA  1265  examines its routing table associations to determine where to forward the information packet  1305 . From information in the routing table and routing algorithm, the HA  1265  encapsulates the information packet  1305  to form information packet  1310  for routing to the VPN-GW  1260  by appending a new source and destination IP address. 
         [0115]    The information packet  1310  is transmitted from the HA  1265  to the VPN-GW  1260  using communication link  1261 . The HAIP  1311  is the IP address for the HA  1265  or source IP address. The destination address VPN-TIA  1312  is the tunnel inner address for the VPN-GW  1260  used to route information packets transmitted within the VPN  1275  to the VPN-GW  1260 . The CNIP  1313  and HOA  1314  are the original source and destination IP address respectively and remain unchanged as does the data payload  1315  compared to the CNIP  1306 , HOA  1307 , and data payload  1308 . 
         [0116]    At the VPN-GW  1360 , the information packet  1310  is encrypted and an ESP  1323  header appended. The encrypted information packet  1310  is then encapsulated to form the third information packet  1320 . Information packet  1320  includes the new source IP address IP-VPN  1321 , which is the IP address for the VPN-GW  1260 . The new destination IP address OCCOA  1322  is the old IP address for the MN  1250 ′ on the sub-network  1244  before changing to MN  1250  on subnetwork  1242 . The ESP  1323  contains security protocol data. The HAIP  1324 , VPN-TIA  1325 , CNIP  1326 , HOA  1327 , and payload data  1328  are encrypted, but otherwise remain unchanged from the HAIP  1311 , VPN-TIA  1312 , CNIP  1313 , HOA  1314 , and payload data  1315  in information packet  1310 . The information packet  1320  is then transmitted from the VPN-GW  1260  to the LHA  1240  at the old colocated care-of address (OCCOA)  1322  for the MN  1250 ′. 
         [0117]    At the LHA  1240 , the LHA  1240  examines its routing table associations for the OCCOA  1322  to determine the destination address at the new foreign agent care-of address (NFCOA)  1332 . The LHA  1240  then encapsulates information packet  1320  to form the fourth information packet  1330 . A new source IP address IP-LHA  1331 , corresponding to the IP address for LHA  1240 , is appended. A new destination IP address NFCOA  1332 , corresponding to the new connection IP address of the MN  1250 , is also appended. Except for encryption, the IP-VPN  1333 , OCCOA  1334 , ESP  1335 , HAIP  1336 , VPN-TIA  1337 , CNIP  1338 , HOA  1339 , and payload data  1340  remain unchanged compared to the IP-VPN  1321 , OCCOA  1322 , ESP  1323 , HAIP  1324 , VPN-TIA  1325 , CNIP  1326 , HOA  1327 , and payload data  1328  of information packet  1320 . This secured information packet  1330  is then forwarded from the FA  1235  to the MN  1250 , which decapsulates and decrypts the information packet  1330  to recover the original information. 
         [0118]      FIG. 14  shows an embodiment for the invention for an optimized communication between a MN and a VPN with a public home address for the MN. A public home address is an IP address that can be used from any IP-based communication network for Internet communication. An IP communication device connected to an IP network can communicate information packets using this public home address. 
         [0119]    A foreign network  1405  includes a DHCP  1410  server connected to a buss line  1430  by communication link  1411 . A MN  1450  connects to the buss line  1430  by communication link  1451 . Communication link  1451  for most mobile IP communication will include a wireless connection (e.g. cellular phone service connection), but in alternate embodiments this link may be a wired link with the MN  1450  using some type of user plug-in connector (e.g. laptop computer through a phone modem). 
         [0120]    The foreign network  1405  is connected to the MN&#39;s  1450  home network  1480  by communication link  1433 . Communication link  1433  connects the buss line  1430  to a buss line  1440  on the home network  1480 . Communication link  1441  links a VPN-GW  1460  to the buss line  1440 . The VPN-GW  1460  is a security gateway encrypting and decrypting information packets to and from a VPN  1475  organized on the home network  1480 . The VPN  1475  includes a HA  1465  connected to the VPN-GW  1460  by a direct, hard-wired communication link  1461 . In this embodiment, the VPN-GW  1460  and HA  1465  can be located inside the same “box.” A CN  1470  connects to the HA  1465  by communication link  1471 . The HA  1465  also has a communication link  1466  to buss line  1441 . 
         [0121]    In this preferred embodiment, a public home address (HOA) designates the IP address of the MN  1450 . The VPN-GW  1460  possesses an IP address (IP-VPN) designation. The HA  1465  also possesses an IP address (HAIP) designation, and the CN  1470  has an IP address (CNIP). During a registration procedure at the start of a communication session, a colocated care-of IP address is also assigned to the MN  1450  by the DHCP  1410  corresponding to the IP address location of the MN  1450  on the foreign network  1405  that is used to route information packets from the VPN  1475  on the home network  1480 . 
         [0122]      FIG. 15  shows the encapsulation process for the invention of the network configuration of  FIG. 14  for the forward path communication from the CN to the MN. At communication startup, the MN  1450  initiates a registration protocol to obtain a colocated care-of address on the foreign network  1405  from the DHCP  1410 . The HA  1465  sets up a VPN tunnel with the VPN-GW  1460  by registering a routing table association for the HOA and a VPN tunnel inner address (VPN-TIA) to use for tunneling information packets to the MN  1450 . The colocated care-of address (CCOA) is also registered in a routing table association with public home address designation (HOA) for the MN  1450  on the HA  1465 . 
         [0123]    Additionally, the VPN-GW  1460  and the MN  1450  perform internet key exchange (IKE) negotiations to exchange encryption keys, methods, and authentication information. This information is used by the security protocol to encrypt the information packet. Acceptable security algorithms for the key exchange include Message Digest 5 (MD5), Secure Hash Algorithm (SHA), and a Diffie-Hellman combination algorithm using a public and private encryption key. A number of encryption algorithms may be available, including Data Encryption Standard (DES), Triple Data Encryption Standard (3DES), Rivest-Shamir-Aldeman (RSA), ElGamal, RC2 and RC4. 
         [0124]    The HA  1465  also sets up a VPN tunnel with the VPN-GW  1460  to register an association for the HOA and a VPN tunnel inner address (VPN-TIA) to use for tunneling information packets to the MN  1450 . This VPN-TIA can be setup during IKE negotiations, assigned manually, or by some other means. After this registration and initialization protocol, communication can occur between the MN  1450  and the CN  1470 . 
         [0125]    The first information packet  1505  is transmitted from the CN  1470  to the HA  1465 . The CNIP  1506  is the IP address for the CN  1470  and is the source IP address for the information packet  1505 . The destination IP address HOA  1507  is the home address designation of the MN  1450 . The payload data  1508  in the information packet  1505  is the actual information being transmitted. At the HA  1465 , the HA  1465  examines its routing table associations to determine where to forward the information packet  505  and forwards the information packet  1505 , without having to perform an encapsulation for the wired connection  1461 , to the VPN-GW  1460 . The information packet  1510  is identical to the information packet  1505 , and includes CNIP  1513 , HOA  1514 , and data payload  1513 , which are identical to the CNIP  1506 , HOA  1507 , and data payload  1508 . 
         [0126]    At the VPN-GW  1460 , the information packet  1510  is encrypted and an ESP  1523  header added. The encrypted information packet  1510  is then encapsulated to form the third information packet  1520 . Information packet  1520  includes the new source IP address IP-VPN  1521 , which is the IP address for the VPN-GW  1460 . The new destination IP address HOA  1522  is the IP address for the MN  1450  on the VPN  1480 . The ESP  1523  contains security protocol data. The CNIP  1524 , HOA  1525 , and payload data  1526  are encrypted, but otherwise remain unchanged from the CNIP  1511 , HOA  1512 , and payload data  1513  in information packet  510 . 
         [0127]    The information packet  1520  is transmitted from the VPN-GW  1460  back to the HA  1465 . The HA  1465  again examines its routing tables entries for an association for the destination address HOA  1522 . The HA  1465  then encapsulates information packet  1520  to form the fourth information packet  1530 . A new source IP address HAIP  1531 , corresponding to the IP address for HA  1465 , is appended. A new destination IP address CCOA  1532 , corresponding to the colocated IP address of the MN  1450 , is also appended. The IP-VPN  1533 , HOA  1534 , ESP  1535 , CNIP  1536 , HOA  1537 , and payload data  1540  remain unchanged compared to the IP-VPN  1521 , HOA  1522 , ESP  1523 , CNIP  1524 , HOA  1525 , and payload data  1526  of information packet  1520 . This secured information packet  1530  is then transmitted to the MN  1450  using communication link  1466 . After arriving at the MN  1450 , the MN  1450  decapsulates and decrypts the information packet  1530  to recover the original information. 
         [0128]      FIG. 16  shows the encapsulation process for the invention of the network configuration of  FIG. 14  for information packets transmitted from the mobile node to the correspondence node on the reverse path. Information packet  1601  is formed by MN  1450  for transmission to the CN  1470 . HOA  1602  is the source IP address for the MN  1450  on the home network  1480  within the VPN  1475 . The IP-VPN  1603  is the destination address for the VPN-GW  1460  securing the VPN  1475 . The ESP  1604  header contains data to provide confidentiality and signifies that the remaining portion of information packet  1601  is encrypted. The HOA  1605  is the ultimate public home address for the MN  1450  on the VPN  1475  and the ultimate source address, and the CNIP  1606  is the IP address for the CN  1470  and the ultimate destination address for the information packet  1601 . The data payload  1607  is the data actually being transmitted to the CN  1470 . 
         [0129]    Information packet  1601  is forwarded to VPN-GW  1460  and decaspulated to reveal the encrypted information packet  1610  with the ESP  1604  header appended. The ESP  1604  is processed and the information packet  1610  decrypted. The information packet  1610  includes the source HOA  1611  public home IP address for the MN  1450 , the destination CNIP  1612  IP address for the CN  1470 , and data payload  1613 . The information packet  1610  is forwarded to the CN  1470  where it is decapsulated to reveal the data payload  1613  which can then be processed by the CN  1470 . 
         [0130]    While the invention has been particularly shown and described with respect to preferred embodiments, it will be readily understood that minor changes in the details of the invention may be made without departing from the spirit of the invention. Having described the invention, we claim: