1. Field of the Invention
The present invention relates to Mobile IP network technology. More particularly, the present invention relates to a Mobile IP mobile router.
2. Description of the Related Art
Mobile IP is a protocol which allows laptop computers or other mobile computer units (referred to as xe2x80x9cMobile Nodesxe2x80x9d herein) to roam between various sub-networks at various locationsxe2x80x94while maintaining internet and/or WAN connectivity. Without Mobile IP or related protocol, a Mobile Node would be unable to stay connected while roaming through various sub-networks. This is because the IP address required for any node to communicate over the internet is location specific. Each IP address has a field that specifies the particular sub-network on which the node resides. If a user desires to take a computer which is normally attached to one node and roam with it so that it passes through different sub-networks, it cannot use its home base IP address. As a result, a business person traveling across the country cannot merely roam with his or her computer across geographically disparate network segments or wireless nodes while remaining connected over the internet. This is not an acceptable state-of-affairs in the age of portable computational devices.
To address this problem, the Mobile IP protocol has been developed and implemented. An implementation of Mobile IP is described in RFC 2002 of the Network Working Group, C. Perkins, Ed., October 1996. Mobile IP is also described in the text xe2x80x9cMobile IP Unpluggedxe2x80x9d by J. Solomon, Prentice Hall. Both of these references are incorporated herein by reference in their entireties and for all purposes.
The Mobile IP process and environment are illustrated in FIG. 1A. As shown there, a Mobile IP environment 2 includes the internet (or a WAN) 4 over which a Mobile Node 6 can communicate remotely via mediation by a Home Agent 8 and a Foreign Agent 10. Typically, the Home Agent and Foreign Agent are routers or other network connection devices performing appropriate Mobile IP functions as implemented by software, hardware, and/or firmware. A particular Mobile Node (e.g., a laptop computer) plugged into its home network segment connects with the internet through its designated Home Agent. When the Mobile Node roams, it communicates via the internet through an available Foreign Agent. Presumably, there are many Foreign Agents available at geographically disparate locations to allow wide spread internet connection via the Mobile IP protocol. Note that it is also possible for the Mobile Node to register directly with its Home Agent.
As shown in FIG. 1A, Mobile Node 6 normally resides on (or is xe2x80x9cbased atxe2x80x9d) a network segment 12 which allows its network entities to communicate over the internet 4 through Home Agent 8 (an appropriately configured router denoted R2). Note that Home Agent 8 need not directly connect to the internet. For example, as shown in FIG. 1A, it may be connected through another router (a router R1 in this case). Router R1 may, in turn, connect one or more other routers (e.g., a router R3) with the internet.
Now, suppose that Mobile Node 6 is removed from its home base network segment 12 and roams to a remote network segment 14. Network segment 14 may include various other nodes such as a PC 16. The nodes on network segment 14 communicate with the internet through a router which doubles as Foreign Agent 10. Mobile Node 6 may identify Foreign Agent 10 through various solicitations and advertisements which form part of the Mobile IP protocol. When Mobile Node 6 engages with network segment 14, Foreign Agent 10 relays a registration request to Home Agent 8 (as indicated by the dotted line xe2x80x9cRegistrationxe2x80x9d). The Home and Foreign Agents may then negotiate the conditions of the Mobile Node""s attachment to Foreign Agent 10. For example, the attachment may be limited to a period of time, such as two hours. When the negotiation is successfully completed, Home Agent 8 updates an internal xe2x80x9cmobility binding tablexe2x80x9d which specifies the care-of address (e.g., a collocated care-of address or the Foreign Agent""s IP address) in association with the identity of Mobile Node 6. Further, the Foreign Agent 10 updates an internal xe2x80x9cvisitor tablexe2x80x9d which specifies the Mobile Node address, Home Agent address, etc. In effect, the Mobile Node""s home base IP address (associated with segment 12) has been shifted to the Foreign Agent""s IP address (associated with segment 14).
Now, suppose that Mobile Node 6 wishes to send a message to a corresponding node 18 from its new location. A message from the Mobile Node is then packetized and forwarded through Foreign Agent 10 over the internet 4 and to corresponding node 18 (as indicated by the dotted line xe2x80x9cpacket from MNxe2x80x9d) according to a standard internet protocol. If corresponding node 18 wishes to send a message to Mobile Nodexe2x80x94whether in reply to a message from the Mobile Node or for any other reasonxe2x80x94it addresses that message to the IP address of Mobile Node 6 on sub-network 12. The packets of that message are then forwarded over the internet 4 and to router R1 and ultimately to Home Agent 8 as indicated by the dotted line (xe2x80x9cpacket to MN(1)xe2x80x9d). From its mobility binding table, Home Agent 8 recognizes that Mobile Node 6 is no longer attached to network segment 12. It then encapsulates the packets from corresponding node 18 (which are addressed to Mobile Node 6 on network segment 12) according to a Mobile IP protocol and forwards these encapsulated packets to a xe2x80x9ccare ofxe2x80x9d address for Mobile Node 6 as shown by the dotted line (xe2x80x9cpacket to MN(2)xe2x80x9d). The care-of address may be, for example, the IP address of Foreign Agent 10. Foreign Agent 10 then strips the encapsulation and forwards the message to Mobile Node 6 on sub-network 14. The packet forwarding mechanism implemented by the Home and Foreign Agents is often referred to as xe2x80x9ctunneling.xe2x80x9d
In addition to providing connectivity to a mobile node, it may be desirable to provide for the mobility of one or more networks moving together, such as on an airplane or a ship. RFC 2002 section 4.5 discusses the possibility of implementing mobile routers.
In one approach suggested in RFC 2002 section 4.5, a Home Agent is configured to have a permanent registration for each fixed node. FIG. 1B is a diagram of a Mobile IP mobile router and associated environment in which a Home Agent is configured to have a permanent registration for each fixed node. As shown, a mobile router 20 may support multiple nodes 22, 24, 26 which may be fixed with respect to the mobile router 20. In order to receive communication from a corresponding node 28, messages must be routed to the appropriate fixed node 22, 24, or 26. As the RFC suggests, a Home Agent 30 may be configured to have a permanent registration for each fixed node. By way of example, the permanent registration may indicate the mobile router""s address as the care-of address. Thus, a separate mapping table may associate the IP address of each of the fixed nodes 22, 24, and 26 with the mobile router 20. However, this is problematic since the mapping table is typically configured while the mobile router 20 is coupled to the Home Agent 30. In other words, the routing table is static. Suppose a person boards an airplane and wishes to connect a laptop to the airplane""s xe2x80x9cmobile networkxe2x80x9d via the mobile router 20. If a new node 32 is added to the mobile router 20 after the airplane leaves the airport, the IP address of this new node may not be added to the mapping table. As a result, communication cannot be received by this new node 32 via the mobile router 20. In addition, since the mobile router 20 may accommodate thousands of devices, or nodes, there would potentially be an enormous number of entries to store in such a mapping table for these nodes. Moreover, such a mapping table may include entries for multiple mobile routers. Accordingly, such a mapping table would consume a substantial amount of memory as well as be cumbersome to search.
In another approach suggested in RFC 2002, the mobile router 20 may advertise connectivity to the entire xe2x80x9cmobile network.xe2x80x9d FIG. 1C is a diagram of a Mobile IP mobile router and associated environment in which the mobile router advertises 34 connectivity to each node associated with the mobile router. The RFC states that this may be performed using normal IP routing protocols through a bi-directional tunnel to its Home Agent 30. However, the RFC provides no implementation details.
In view of the above, it would be desirable to have improved techniques for implementing a Mobile IP mobile router.
Methods and apparatus for providing Mobile IP mobile router functionality are provided. This is accomplished through identifying networks associated with the mobile router which may then be used to update the appropriate tables. Thus, the Home Agent does not need to separately track each node associated with the mobile router.
In accordance with one aspect of the invention, the Home Agent receives a registration request packet. The registration request packet may include a care-of address for the mobile router. Networks associated with the mobile router are then identified. The Home Agent then updates a routing table to associate the identified networks with the care-of address. In addition, the Home Agent updates a mobility binding table with the care-of address for the mobile router.
In accordance with another aspect of the invention, at least one network linked to the mobile router is listed in an extension appended to the registration request. Upon receipt of such request, the Home Agent identifies networks associated with the mobile router from the extension. The Home Agent then updates a routing table to associate the care-of address with the identified networks and updates a mobility binding table with the care-of address. In addition, the Foreign Agent may update a visitor table with an entry for each of the networks listed on the extension to associate those networks with the mobile router.
In accordance with yet another aspect of the invention, routing information is exchanged between the Home Agent and the mobile router. A routing table associated with at least one of the Home Agent and the mobile router is updated as appropriate to include the exchanged routing information. By way of example, networks associated with the mobile router may be obtained from the exchanged routing information and the appropriate routing tables may be updated to associate the networks with the care-of address for the mobile router. In addition, the Home Agent updates its mobility binding table with the care-of address. If the care-of address is the address of a Foreign Agent, a visitor table may be updated to associate the networks with the mobile router.