The present invention relates to the field of mobile computing, and, more particularly to a method, apparatus and system for extending mobile Internet Protocol (“IP”) home agent functionality to enable roaming mobile computing devices to use private (i.e. not globally routable) home Internet Protocol (“IP”) addresses.
Use of mobile computing devices (hereafter “mobile nodes”) such as laptops, notebook computers, personal digital assistants (“PDAs”) and cellular telephones is becoming increasingly popular today. These mobile nodes enable users to move from one location to another (“roam”) (within and/or across wireless networks, and within and/or across IP subnets) while continuing to maintain their connectivity to the same destination network, whenever feasible. A subnet refers to a portion of an organization's network interconnected to other subnets by a routing element. Subnets are well known to those of ordinary skill in the art and further description thereof is omitted herein. Usage paradigms such as “always-on” connectivity and real-time applications such as voice-over-IP (“VoIP”) are driving most corporate (“enterprise”) networks today to facilitate fast and secure inter-IP subnet mobile computing.
In order to support free roaming, networks are starting to adopt one or more industry-wide IP mobility standards. More specifically, the Internet Engineering Task Force (“IETF”) has promulgated an application independent set of standards for IP version 4 (Mobile IPv4, IETF RFC 3344, August 2002, hereafter “Mobile IPv4,”) and IP version 6 (Mobile IPv6, IETF Mobile IPv6, Internet Draft draft-ietf-mobileip-ipv6-24.txt (Work In Progress), June 2003, hereafter “Mobile IPv6”) to enable mobile node users to move from one location to another (crossing IP subnets) while continuing to maintain their connectivity to the same target/destination network.
The present invention is illustrated by way of example and not limitation in the figures of the accompanying drawings in which like references indicate similar elements, and in which:
Embodiments of the present invention provide a method, apparatus and system for extending mobile IP home agent (“HA”) functionality to enable mobile IP nodes to utilize private (i.e. not globally routable) home addresses to communicate with correspondent nodes on any administrative domain.. Reference in the specification to “one embodiment” or “an embodiment” of the present invention means that a particular feature, structure or characteristic described in connection with the embodiment is included in at least one embodiment of the present invention. Thus, the appearances of the phrases “in one embodiment,” “according to one embodiment” or the like appearing in various places throughout the specification are not necessarily all referring to the same embodiment.
HA 130 thereafter intercepts all IP packets from correspondent nodes (illustrated as “CN 150”) addressed to MN 140 and reroutes the packets to MN 140's COA using IP tunneling. IP tunneling is well known to those of ordinary skill in the art and further description thereof is omitted. Additionally, although CN 150 is illustrated as residing within Corporate Intranet 100, it will be readily obvious to those of ordinary skill in the art that CN 150 may reside on any foreign subnet, including subnets on networks outside Corporate Intranet 100 (e.g., External Network 175). As MN 140 moves from one foreign subnet to another, to ensure that HA 130 is able to properly route packets to MN 140, MN 140 must continuously update HA 130 with its new COA.
In the above example, HA 130 typically assigns MN 140 a publicly routable IPv4 address, i.e., an IP address that is defined by the IETF and universally accepted as an address that is recognized and/or globally routable on public networks. Using a publicly routable IP address, MN 140 may communicate with and receive communications from any node on Corporate Intranet 100 and/or External Network 175. IPv4 networks however, suffer from a shortage of routable IP addresses, and as a result, although nodes on External Network 175 may have unique IP addresses, there is significant motivation to use private addresses for MN 140's home address. A private home address may include a local address allocated by a domain administrator for use within a specific domain, but that is not otherwise recognized and/or routable on public networks.
In the mobile IP context, since MN 140 is assumed to be a roaming node, i.e., possibly moving between public and private networks, if MN 140 is assigned a private home address, it may not be consistently reachable. A private address may be used for an MN 140's home address in a limited usage model where MN 140 only needs to communicate with other nodes that belong to the same administrative domain as HA 130. The concept of administrative domains is well known to those of ordinary skill in the art and further description thereof is omitted herein. Thus, for example, MN 140 may communicate with CN 150 only if CN 150 is registered with HA 130 (i.e., the same home agent that MN 140 is registered with currently), or if CN 150 belongs to the same administrative domain as HA 130. This may be accomplished by having HA 130 reverse tunnel packets transmitted from MN 140 and CN 150 to HA 130. MN 140 may not, however, communicate with CN 150 if CN 150 is on a different administrative domain. Although communications from MN 140 to CN 150 may succeed, any responses from CN 150 (addressed to MN 140's private address) may be dropped as an intermediate router may not know how to forward the packet destined for an invalid public address. It is well known to those of ordinary skill in the art that there are no known techniques that currently enable a roaming mobile node to utilize private home addresses to communicate with correspondent nodes on any other administrative domain (including receiving responses from the correspondent node).
Embodiments of the present invention extend HA 130's functionality to enable MN 140 to utilize a private home address to communicate with CN 150, regardless of CN 150's parent administrative domain. MN 140's home address may be statically assigned by a system administrator and/or obtained dynamically from HA 130 during registration. When MN 140 registers with HA 130, if it does not already have a home address, it may request a home address from HA 130 using a NAI extension in its registration request. HA 130 may assign a home address to MN 140 from a pool of addresses, by obtaining an address from a DHCP server and/or other such techniques. According to one embodiment of the present invention, HA 130 may be configured to assign a public or private home address to MN 140 according to predetermined policies. If, according to the policy, HA 130 assigns a private home address, HA 130 may be required to enforce the policy of having MN 140 reverse tunnel outbound mobile IP traffic through HA 130. More specifically, in order to assign a private address to MN 140, in one embodiment MN 140 must set the ‘T’ bit in its registration request to HA 130. The ‘T’ bit signifies that MN 140 will be using reverse tunneling for outbound packets. If the ‘T’ bit is not set in the registration request from MN 140, HA 130 may send MN 140 a registration reply with an appropriate reject error code that indicates the problem to MN 140.
In one embodiment, after registration and assignment of a private home address, MN 140 may send and receive packets routed via HA 130. When HA 130 receives a packet from MN 140 (in reverse tunneled format), it may decapsulate the packet and examine the destination IP address of the inner packet (e.g., to CN 150). If CN 150 is registered with HA 130 and/or belongs to the same administrative domain, HA 130 may tunnel the packet directly to CN 150. If CN 150 is not registered with HA 130 and/or belongs to a different administrative domain, in one embodiment, HA 130 may apply address and port translation to the decapsulated packet's IP and transport headers. Information pertaining to the translation may be maintained in HA 130's binding table. HA 130 may then forward the packet to CN 150 at its current address. According to one embodiment of the present invention, since HA 130 performs the mapping (i.e., address and port translation), the packet that arrives at CN 150 will include a public routable source address. CN 150 may therefore respond to MN 140 using this public routable source address, i.e., to HA 130. HA 130, in turn, may use the information in its binding table to route the packet back to MN 140.
If, however, MN 140 sends a packet destined for a node that belongs to a different administrative domain than HA 130 (e.g., CN 175) in 308, HA 130 may decapsulate the packet, modify the source IP address to HA 130's publicly routable IP address and source port address, create an entry in Binding Table 210 and forward the packet to CN 175 in 309. CN 175 may reply to the source IP address (i.e., HA 130's public address) in 310 and HA 130 may receive the reply, change the destination IP address to MNh, change the destination port to MN 140's port address, and tunnel the packet to MN 140 in 311.
The mobile nodes and home agents according to embodiments of the present invention may be implemented on a variety of data processing devices. It will be readily apparent to those of ordinary skill in the art that these data processing devices may include various types of software, and may comprise any devices capable of supporting mobile networks, including but not limited to mainframes, workstations, personal computers, laptops, portable handheld computers, PDAs and/or cellular telephones. In an embodiment, mobile nodes may comprise portable data processing systems such as laptops, handheld computing devices, personal digital assistants and/or cellular telephones. According to one embodiment, home agents may comprise data processing devices such as personal computers, workstations and/or mainframe computers. In alternate embodiments, home agents may also comprise portable data processing systems similar to those used to implement mobile nodes.
According to an embodiment of the present invention, data processing devices may include various components capable of executing instructions to accomplish an embodiment of the present invention. For example, the data processing devices may include and/or be coupled to at least one machine-accessible medium. As used in this specification, a “machine” includes, but is not limited to, any data processing device with one or more processors. As used in this specification, a machine-accessible medium includes any mechanism that stores and/or transmits information in any form accessible by a data processing device, the machine-accessible medium including but not limited to, recordable/non-recordable media (such as read only memory (ROM), random access memory (RAM), magnetic disk storage media, optical storage media and flash memory devices), as well as electrical, optical, acoustical or other form of propagated signals (such as carrier waves, infrared signals and digital signals).
According to an embodiment, a data processing device may include various other well-known components such as one or more processors. The processor(s) and machine-accessible media may be communicatively coupled using a bridge/memory controller, and the processor may be capable of executing instructions stored in the machine-accessible media. The bridge/memory controller may be coupled to a graphics controller, and the graphics controller may control the output of display data on a display device. The bridge/memory controller may be coupled to one or more buses. A host bus controller such as a Universal Serial Bus (“USB”) host controller may be coupled to the bus(es) and a plurality of devices may be coupled to the USB. For example, user input devices such as a keyboard and mouse may be included in the data processing device for providing input data.
In the foregoing specification, the invention has been described with reference to specific exemplary embodiments thereof. It will, however, be appreciated that various modifications and changes may be made thereto without departing from the broader spirit and scope of the invention as set forth in the appended claims. The specification and drawings are, accordingly, to be regarded in an illustrative rather than a restrictive sense.