ANYCAST BINDING MOBILE COMMUNICATION METHOD AND SYSTEM

Abstract: This is a method and system to efficiently do handovers for mobile IP. The mobile node registers itself with several foreign agents using a new registration type. Only one of the foreign agents is selected to forward the data packet to the mobile node. The selection algorithm may be one based on randomness, dynamic learning, message traffic congestion, or statistical information collected at the mobile node.

Description: ANYCAST BINDING MOBILE COMMUNICATION METHOD AND SYSTEM TECHNICAL FIELD Mobile communications networks are being used to support the Internet. Mobile Internet terminals (mobile nodes) require support as they move within the wireless network. The present invention efficiently solves the problem of mobile Internet connectivity while preserving bandwidth. DEFINITIONS Care-of- Address Termination point of a tunnel toward a mobile node, for data packets forwarded to the mobile node while it is away from home. There are two different types of care-of-address: a foreign agent care-of-address is an address of a foreign agent with which the mobile node is registered; co-located care-of-address is an externally obtained local address which the mobile node has associated with one of its own network interfaces. Foreign Agent A router on a mobile node's visited network that cooperates with the home agent to complete the delivery of data packets to the mobile node while it is away from home. Home Address An IP address assigned to a mobile node within its home link. Home Agent A router on a mobile node's home network that delivers data packets to departed mobile nodes, and maintains current location information on each. Host Any node that is not a router IP Internet Protocol Interface A node's attachment to a link. Link A communication facility or medium over which nodes can communicate at the link layer, such as Ethernet (simple bπdged) A link is the layer immediately below IP. Mobile Node A node that can change its point of attachment from one link to another, while still bemg reachable via its home address Mobility Binding The association of a home address with care-of-address, for the remaining lifetime of that association. Node A device that implements IP Packet An IP header plus payload Tunnel The path followed by a data packets while it is encapsulated While encapsulated a data packet is routed to a knowledgeable agent, that decapsulates the data packet and then forwards it to its ultimate destination Mobile communications networks, commonly designated as cellular networks, are rapidly expanding to support more services beyond voice service One of the new services is the running of Internet Protocols (IP) to support mobile access to the Internet When mobile users access the Internet and are moving geographically the connection must be handed over between connection nodes to maintain the connection to the Internet Handovers result from a range limitation due to the geographic limitation of communication distances between nodes within a mobile communication network Handovers are likely to occur while the terminal is moving within a wireless network with several access points Simultaneous bindings are used to ensure that handovers are as smooth as possible Using this type of binding, data packets are simultaneously routed through several access points withm the geographical area surrounding the user's last access point called a mobile node The problem with this solution is that excess bandwidth is used because the same data packet is sent through many access points to the terminal The excess data packets are simply discarded at the terminal resulting in wasted transmission capacity. It is more efficient to send data packets only once to a mobile terminal. Current Solutions to IP Mobility: One system for providing mobility to the Internet is described in a paper published in IEEE May 1997 issue at pages 84-99, by Charles E. Perkins, of Sun Microsystems. In addition, an Internet document specifies protocol enhancements that allow transparent routing of IP datagrams to mobile nodes in the Internet and can be found at h(tn://sunsile.auc.dk/RFC7rfc/ rfc2002 . html ( incorporated herein by reference in its entirety). In his May 1997 article, Mr. Perkins descπbes Agent Advertisement, Registration, and Tunneling as methods to support mobile IP. He further descπbes route optimization techniques. The following is an exceφt from Mr. Perkins paper describing the protocol, found at page 86. "Mobile IP is a way of performing three related functions: Agent Discovery - Mobility Agents advertise their availability on each link for which they provide service. Registration - When the mobile node is away from home, it registers care-of-address with its home agent " Tunneling - In order for datagrams to be delivered to the mobile node when it is away from home, the home agent has to tunnel the datagrams to the care-of-address. "The following will give a rough outline of operation of the mobile IP protocol, making use of the above-mentioned operations. Figure 1 (not shown) may be used to help envision the roles played by the entities. Mobility agents make themselves known by sending agent advertising messages. An impatient mobile node may optionally solicit an agent advertisement message. After receiving an agent advertisement, a mobile node determines whether it is on its home or a foreign network. A mobile node basically works like any other node when it is at home. When a mobile node moves away from its home network, it obtains a care-of-address on the foreign network for instance, by soliciting or listening for agent advertisement, or contacting Dynamic Host Configuration Protocol (DHCP) or Point-to-Point (PPP) While away from home, the mobile node registers each new care-of-address with its home agent, possibly by way of a foreign agent. Datagrams sent to the mobile node's home address are intercepted by its home agent, tunneled by its home agent to the care-of-addresses, received at the tunnel endpomt (at either a foreign agent or the mobile node itself), and finally delivered to the mobile node. In the reverse direction, datagrams sent by the mobile node are generally delivered to their destination using standard IP routing mechanisms, not necessanly passing through the home agent (but see the eighth section) " "When the home agent tunnels a datagram to the care-of-address, the inner IP header destination (i.e , the mobile node's home address) is effectively shielded from the intervening routers between its home network and its current location At the care-of-address, the oπginal datagram exits from the tunnel and is delivered to the mobile node " "It is the job of every home agent to attract and intercept datagrams that are destined to the home address of any of its registered mobile nodes The home agent basically does this by using a minor variation on Address Resolution Protocol (ARP), and to do so in the natural mode it has to have a network interface on the link indicated by the mobile node's home address However, the latter requirement is part of the mobile IP specification When foreign agents are in use, similarly, the natural mode of operation suggests that the mobile node be able to establish a link to its foreign agent Other configurations are possible, however, using protocol operations not defined by (and invisible to) mobile IP Notice that, if the home agent is the only router advertising reachability to the home network, but there is no physical link instantiating the home network, then all datagrams transmitted to mobile nodes addressed on that home network will naturally reach the home agent without any special link operations." "Figure 1 (not shown) illustrates the routing of datagrams to and from a mobile node away from home, once the mobile node has registered with its home agent. The mobile node is presumed to be using a care-of-address provided by the foreign agent: A datagram to the mobile node arrives on the home network via standard IP routing. The datagram is intercepted by the home agent and is tunneled to the care-of-address, as depicted by the arrow going through the tube. The datagram is de-tunneled and delivered to the mobile node. For datagrams sent by the mobile node, standard IP routing delivers each to its destination. In the Figure (1) sic, the foreign agent is the mobile node's default router.' Further background on mobile IP can be found in another paper by Mr. Charles Perkins, Sun Microsystems and David B. Johnson, Carnegie Mellon University prepared for by the Mobile IP Working Group of the Internet Engineering Task Force (IETF), dated 25 February 1999. Online reference: http://search.ietf.org/internet-drafts/. In their paper they describe a system for route optimization in Mobile IP. The system described allows for routing to a mobile node without going to the home agent first to reduce traffic and optimize routing. Messrs. Johnson and Perkins published another IETF paper on 25 June 1999 setting forth a mobility support protocol IPv6. In it each mobile node is always identified by its home address, regardless of its current point of attachment to the Internet. When a terminal is operating away from home it accesses the Internet via a care-of-address to give the current location. It allows IPv6 nodes to cache the binding of a mobiles node's home address to its care-of-address to send the mobile packets directly to the latter. This protocol envisions searching for neighboring nodes to handover connections but does not solve the problem of duplicate data packets being sent by several nodes to a moving user. The above reference papers descπbe systems that support mobile IP and the invention disclosed herein These papers are mcoφorated herein by reference. Currently, mobile nodes are serviced using a simultaneous binding. In a simultaneous binding a mobile node has many care-of- addresses When there is more than one care-of address active for a mobile node, the home agent is instructed to send a duplicated encapsulated datagram to each care-of address for forwarding by multiple foreign agents to the same mobile node. OBJECTS OF THE INVENTION An object of the Invention is to provide binding techniques between nodes in a mobile communications network for efficient data transmission to mobile users Another object of the invention is to save bandwidth when delivering data packets to mobile users of a mobile network Yet another object is to enable efficient access to the Internet by mobile users DISCLOSURE OF THE INVENTION This invention is a novel binding technique for mobile Internet Protocol (IP) The present use of simultaneous bindings waste bandwidth because all foreign agents forward data packets to a mobile node The excess packets are discarded wasting bandwidth In contrast, the new Anycast binding registers itself in several IP sub-networks simultaneously as before but only one of the foreign agents delivers certain data packets to the mobile node Because only one foreign agent is selected to deliver the data packet rather then many, bandwidth is saved BRIEF DESCRIPTION OF THE DRAWINGS Figure 1 is a representation of a data message transmission from an Internet Host to a mobile node Figure 2 is a representation of data message routing from the Internet Host through a single foreign agent to a mobile node BEST MODE FOR CARRYING OUT THE INVENTION The invention is set forth in the drawings and the following descπption Referπng to Figure 1 , the present method of delivering data packets uses an Internet Host 2 to deliver data packets to a mobile network where they are forwarded by home agent 4 to a set of foreign agents 6 The foreign agents 6 simultaneously broadcast the same data packet to a mobile node 8 within their geographic reach When simultaneous bindings are used to forward data packets to a mobile node 8 it uses multiple foreign agents 6 to forward the data packet to the mobile node 8 This system works but it uses a lot of bandwidth As descπbed in the papers referenced above, mobile nodes can be serviced the same as a stationary node if they are assigned a new address to identify their location Referring to Figure 2, in the present invention, the home agent 4 encapsulates the original data packet and chooses one prevailing care of address 10 using the algorithm of this invention Only one foreign agent then forwards the data packet to the mobile node 8 More specifically, referπng to Figure 2, an Internet host 2 communicates over a mobile network as before to a home agent 4 The home address of a mobile node 8 is always the same Data packets caught by the home agent 4 always include a home address of a mobile node 8 The data packets are copied and tunneled 12 to each foreign agent 6a, b, c, d using a corresponding care-of- addresses 10 in the encapsulating packets Both the Anycast Bindings 18 described herein and the presently used simultaneous bindings have many care-of-addresses 10 The difference is in the selection of only one foreign agent 6 to forward the data packet to the mobile node 8 With the new Anycast Binding 18, the home agent 4 encapsulates the original data packet and chooses one prevailing care-of-address 10 using the algorithm hereafter described With the selection of one care-of-address 10 associated with one foreign agent 6b it alone forwards certain data packets to the mobile node 8. In contrast, when simultaneous binding is used to maintain communication with a mobile node 8, the data packet is copied to all foreign agents 6a,b,c,d thereby wasting bandwidth. The mobile node 8 binds itself to a set of foreign agents 6a,b,c,d within its geographical area Anycast binding 18 selects one foreign agent 6b to deliver the data packet to the mobile node 8 as follows The home agent 4 makes the choice of the foreign agent to deliver the data packet from the set bound to the mobile node 8 if a non-hierarchical environment is in place In a hierarchical environment, an intermediate agent common to all foreign agents 6 bound to a mobile node 8 makes the choice of a foreign agent 6b to forward the data packet to the mobile node 8 The algoπthm that may choose one of the foreign agents 6 in the above environment is set forth below In its simplest form the Anycast Binding algorithm 18 selects the foreign agent 6b in a random manner from the set of foreign agents 6 bound to the mobile node 8 Another vaπation of the algorithm is to consider congestion information 14 of message traffic in the bound foreign agents 6a,b,c,d based on real time or statistical information to select the most efficient foreign agent 6 To support this decision process congestion information 14 is accessed by Anycast Binding 18 for use in its decision algoπthm Histoπcal information may also be accumulated and stored in a file 20 for access by Anycast Binding algoπthm 18 The histoπcal data may be used to predict which of the foreign agents 6 is the most efficient to service a mobile node 8 bound to it Also, a statistical file 22 may be created and accessed by the Anycast Binding algorithm 18 to select a foreign agent 6b to forward the data packet to the mobile node 8 The algorithm may include probability predictions of message traffic over a bound set of foreign agents as a basis for assigning a data packet to a foreign agent for forwarding to a mobile node 8. A mathematical representation of the algorithm follows: // //Random selection of the destination's care-of-address //in case of Anycast Binding to be used in a mobile node //destined packet. // address select coa (address destination) { return a randomly selected care-of-address from the set of active Anycast Binding of this destination; { // //Congestion information based selection of the destination's //care-of-address in case of Anycast Binding to be used in //mobile node destined packet. // address select_coa(address destination) { return a care-of-address from the set of active Anycast Bindings of this destination that belongs to the least congested route; }• A mobile node 8 capable of sending Anycast Bindings registers with every foreign agent 6 that it can hear. The mobile node also does the book keeping function on the previous hop of the received data packets. With this information the mobile node 8 has information on which foreign agent 6 is giving the most efficient service. This accumulated data is usable in constructing a decision to select foreign agents 6 based on historical usage. This data is also usable by the mobile node 8 to select the next best hop to a foreign agent 8 for the mobile node originated data transmission. There are several alternatives for implementing the signaling messages for Anycast Bindings 18. A separate Anycast binding 18 could be used, or the existing mobile IP messages can be enhanced to support Anycast Bindings 18. The best method is to use the existing mobile IP registration message and add an extension or by defining a new flag. The previous description of the invention does not limit it to alternate embodiments that may be used to practice it and is not a disclaimer of these embodiments.

Claims: CLAIMS We claim: 1. A Method for forwarding a data packet in a mobile communication network to a mobile node having the steps of: Sending a data packet in said mobile communications network to a mobile node by, selecting on foreign agent to send said data packet to said mobile node, and sending said data message via one foreign agent to said mobile node. 2. A method according to claim 1 having the further step of using a care-of-address to select a foreign agent. 3. A method according to claim 2 having the further step of creating a home address. 4. A method according to claim 3 having the further step of tunneling messages from said home address to said care-of-address. 5. A method according to claim 4 having the further step of binding a mobile node to a plurality of foreign agents. 6. A method according to claim 5 having the further step of selecting one foreign agent to send said data message to said mobility node based message congestion criteria. 7. A method according to claim 5 having the further step of selecting one foreign agent based upon historical data associated with said mobile node. 8. A method according to claim 5 having the further step of selecting one foreign agent based upon statistical data of usage of said mobile node with a plurality of foreign agents. 9. A system for forwarding data packets over a mobile communications network to communicate with an Internet Protocol comprising: a mobile communication network, a home address in said network, a care-of-address in said network, a mobility binding in said network, a plurality of foreign agent in said network, a mobile node in said network, a tunnel for forwarding data packets to said mobile node using said care-of-address as a destination for said home address, and means to select one foreign agent from said plurality of foreign agents to forward said data packet to said mobile node. 10. A system according to claim 9 further comprising an algorithm as said means for selecting one foreign agent to forward data packets to said mobile node. 11. A system according to claim 10 further comprising an algorithm based on historical usage of a foreign agent for forwarding data packets to a mobile node. 12. A system according to claim 10 further comprising an algorithm based upon statistical modeling of the usage of a foreign agent to forward data packets to a mobile node. 13. A system according to claim 10 further comprising an algorithm based upon the congestion of data packet transmissions from a foreign agent to a mobile node. 14. A system according to claim 9 further comprising a home agent to forward data messages to said mobile node. 15. A system according to claim 9 further comprising a link to connect nodes within said mobile communications network. 16. A system according to claim 9 further comprising a means to associate one care-of-address with one foreign agent. 17. A system according to claim 9 further comprising an algorithm based upon the random selection of a foreign agent to forward data packets to a mobile node. 18. A Method for forwarding a data packet in a mobile communication network to a mobile node having the steps of: creating a home agent, assigning a home address, tunneling a data packet in said mobile communications network to a care-of-address, selecting one foreign agent to send said data packet to said mobile node, and sending said data message via one foreign agent to said mobile node. 19. A method according to claim 18 wherein the step of selecting one foreign agent to send data packets to said mobile node is an algorithm based on randomness of available mobile nodes bound to a group of foreign agents. 20. A method according to claim 18 wherein the step of selecting one foreign agent to send data packets to said mobile node is an algorithm based on historical use of the mobile node a group of foreign agents. 21. A method according to claim 18 wherein the step of selecting one foreign agent to send data packets to a mobile node is an algorithm based on statistical usage of foreign agents bound to a mobile node.

Inventors: BERGENWALL MARTIN, HAVERINEN HENRY, SEPPALA JUKKA, SODERLUND TOM, BERGENWALL, MARTIN, HAVERINEN, HENRY, SEPPALA, JUKKA, SODERLUND, TOM
Applicants: BERGENWALL MARTIN, HAVERINEN HENRY, NOKIA INC, NOKIA IP, SEPPALA JUKKA, SODERLUND TOM, BERGENWALL, MARTIN, HAVERINEN, HENRY, NOKIA INC., SEPPALA, JUKKA, SODERLUND, TOM
Application year: 2000
Main classification: H04Q
IPC codes: H04L12, H04L29