Multiplex communications – Communication over free space – Having a plurality of contiguous regions served by...
Reexamination Certificate
1999-07-16
2004-05-18
Pezzlo, John (Department: 2662)
Multiplex communications
Communication over free space
Having a plurality of contiguous regions served by...
C370S401000, C370S469000
Reexamination Certificate
active
06738362
ABSTRACT:
BACKGROUND OF THE INVENTION
A. Field of the Invention
This invention relates generally to systems that provide mobile Internet Protocol (IP) networking, wherein a mobile communications device such as a portable laptop computer or personal digital assistant may communicate with a host computer on an IP network. More particularly, the invention relates to the architecture and arrangement of communications devices functioning as home agents and foreign agents that are used in such a system.
B. Description of Related Art
Public packet switched networks can be used to carry traffic to and from a mobile communications device, such as a laptop computer or personal digital assistant equipped with a cellular telephone modem. The basic architecture of mobile IP data networking is known in the art and described in several publications, including the Request for Comments document RFC 2002 (1996) and in the textbook of Charles E. Perkins,
Mobile IP Design Principles and Practices
, Addison-Wesley Wireless Communications Series (1998), both of which are fully incorporated by reference herein. Persons skilled in the art of mobile IP data networking are familiar with the contents of both of these documents and the devices used to implement mobile IP data networking in practice.
Basically, and with reference to
FIG. 1
, in Mobile IP communication, a wireless mobile node
10
communicates with a target host
12
on an IP network
14
by means of two devices, a “foreign agent”
16
and a “home agent”
18
. Typically, foreign agent functionality is incorporated into a router or network access server chassis located on a mobile node's visited network
20
. A radio access network linking the mobile node to the foreign agent
16
is not shown for purposes of simplicity in the present discussion. The foreign agent
16
provides routing services for the mobile node while it is registered with the home agent
18
. The foreign agent
16
de-tunnels and delivers datagrams to the mobile node
10
that were tunneled by the mobile node's home agent
18
. In the present specification, the term “tunneling” refers to packet re-addressing, such as performed by the home agent.
The traffic exchanged between the foreign agent
16
and the home agent
18
includes control traffic
22
, e.g., registration request and registration reply messages and session control messages, and data traffic
24
. The control traffic
22
terminates at the home agent. The data traffic
24
is routed from the mobile node's home network
26
to a second network
14
for delivery to the target host. The target host could be connected to the home network by any arbitrary number of intermediate IP networks, or could be on the mobile node's home network
26
.
The home agent
18
is typically implemented in a router on a mobile node's home network
26
. The home agent maintains current location information for the mobile node, through a variety of possible mechanisms, such as described in the patent application of Richard J. Dynarski, et al., “Dynamic Allocation of Wireless' Mobile Nodes Over an Internet Protocol (IP) Network”, Ser. No. 09/233,381, which is incorporated by reference herein. When one or more home agents are handling calls for multiple mobile nodes simultaneously, the home agent(s) are providing, in essence, a service analogous to virtual private network services. Each mobile node is typically associated with a separate home network and the routing path from that home network, through the home agent, to the foreign agent and mobile node is like a virtual private network for the mobile node.
Thus, from the above discussion, it can be seen that the home agent performs two separate and distinct tasks for the foreign agent and mobile node. First, the home agent
18
must perform an authentication and registration process to determine whether the mobile node is authorized to access the home network
26
. This may involve checking the identification of the mobile node (such as, through use of the mobile node's unique serial number or manufacturing number), password authentication, and possibly checking that the mobile node's account is current and paid in full. The home agent registration and authentication functions may be performed in conjunction with, or with the assistance of, a second device, such as an authentication, authorization and accounting server such as a RADIUS server. See the patent application of Yingchun Xu, Ser. No. 08/887,313 filed Jul. 3, 1997 for further details.
Second, the home agent
18
has to tunnel data from the target host to the foreign agent, and provide tunneling services in the reverse direction, i.e., provide packet re-addressing for traffic from the foreign agent to the host
12
. To coordinate tunneling in the reverse direction, the home agent provides a forwarding “care/of” address to the foreign agent to tell the foreign agent
16
where to tunnel traffic from the mobile node so that it can be sent to the host. This forwarding address is typically contained in a registration reply message sent to the foreign agent notifying the foreign agent that the mobile node is authenticated to communicate in the home network. In the prior art, the home agent is also the device that receives the tunneled traffic from the foreign agent for routing onto the home network, and therefore the forwarding address is the home agent's IP address.
The foreign agent also has to perform two distinct tasks for the mobile node, similar to that of the home agent. First, the foreign agent has to handle the registration and session control aspects for the mobile node, including sending registration request messages to the home agent and processing a registration reply message. Second, the foreign agent has tunneling responsibilities for forwarding data packets to the home agent for ultimate distribution to the destination, and de-tunneling data from the home agent and forwarding the data to the mobile node.
The known prior art for providing mobile IP networking services has embraced the concept of a single home agent, in a single chassis, for a given network. However, some larger scale providers of Mobile IP networking services may require multiple home agents on their networks in order to meet demand for mobile IP network services for a large distributed customer base. One possible approach to meeting the expected demand for home agent services is to provide multiple home agents, each home agent embodied in a separate chassis or device. Another approach is to provide a single home agent, but design the home agent such that it has an internal architecture to support multiple networks (e.g., multiple virtual private networks). This latter approach is not considered very attractive, in that management of the home agent would be cumbersome. Furthermore, the home agent would not be particularly fault tolerant, in that any mechanical or software problem in the home agent would potentially affect a large number of virtual private networks. In all the known prior art, the individual devices configured as home agents have implemented both home agent functions within the same device, i.e., registration functions and tunneling/routing functions as described above. Similarly the prior art has embraced the concept of performing both the registration and tunneling responsibilities for a foreign agent in a single device, e.g., network access server.
SUMMARY OF THE INVENTION
The present invention represents an improvement to the above approaches contemplated by the prior art. The present invention contemplates distributing the home agent functionality across multiple devices, with one device devoted to handing the registration and authentication functions, and another device devoted to the routing and tunneling functions of a home agent. The present inventors have appreciated that the: former functions, i.e., registration and authentication, are not particularly computationally intensive, and that a single general purpose computing device can handle a very large number of simultaneous registr
Harper Matthew
Mortsolf Timothy G.
Peirce, Jr. Kenneth L.
Xu Yingchun
McDonnell Boehnen & Hulbert & Berghoff LLP
Pezzlo John
UTStarcom Inc.
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