Electrical computers and digital processing systems: multicomput – Distributed data processing – Processing agent
Reexamination Certificate
1999-06-15
2002-10-15
Lim, Krisna (Department: 2153)
Electrical computers and digital processing systems: multicomput
Distributed data processing
Processing agent
C709S203000, C709S223000, C709S225000, C709S229000, C709S250000
Reexamination Certificate
active
06466964
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to network technology. More particularly, the present invention relates to providing mobility of a node that does not support mobility.
2. Description of the Related Art
Mobile IP is a protocol which allows laptop computers or other mobile computer units (referred to herein as “Mobile Nodes”) to roam between various sub-networks at various locations—while 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 IP Routing for Wireless/Mobile Hosts (Mobile IP) Working Group, C. Perkins, Ed., October 1996. Mobile IP is also described in the text “Mobile IP Unplugged” 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.
1
. As shown, 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) connected to its home network segment (in a wired or wireless network) 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. 1
, Mobile Node
6
normally resides on (or is “based at”) a network segment
12
which allows its network entities to communicate over the internet
4
through Home Agent
8
(an appropriately configured router denoted R
2
). Note that Home Agent
8
need not directly connect to the internet. For example, as shown in
FIG. 1
, it may be connected through another router (a router R
1
in this case). Router R
1
may, in turn, connect one or more other routers (e.g., a router R
3
) 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 from the Mobile Node
6
to Home Agent
8
(as indicated by the dotted line “Registration”). 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 “mobility binding table” which specifies the care-of address (e.g., the Foreign Agent's IP address) in association with the identity of Mobile Node
6
. Further, the Foreign Agent
10
updates an internal “visitor table” 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 “packet from MN”) according to a standard internet protocol. If corresponding node
18
wishes to send a message to Mobile Node—whether in reply to a message from the Mobile Node or for any other reason—it 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 RI and ultimately to Home Agent
8
as indicated by the dotted line (“packet to MN(1)”). 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 “care of” address for Mobile Node
6
as shown by the dotted line (“packet to MN(2)”). 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 network segment
14
. The packet forwarding mechanism implemented by the Home and Foreign Agents is often referred to as “tunneling.”
As described above, a Mobile Node may register with its Home Agent after roaming to a Foreign Agent. The Mobile Node may then further roam to a second Foreign Agent. Upon de-registering, the Mobile Node then may again register with its Home Agent so that it may receive packets via the second Foreign Agent. Thus, through the registration process, a Mobile Node may receive packets sent to it by a Corresponding Node via the Foreign Agent that the Mobile Node is visiting.
Currently, Mobile IP as described in RFC
2002
requires that Mobile Nodes (e.g., laptops, cell phones) implement the Mobile IP protocol. However, major operating system vendors are not currently implementing the Mobile IP protocol in their operating system software. Similarly, proprietary operating systems typically do not implement the Mobile IP protocol. Thus, although a node may theoretically achieve mobility through the Mobile IP protocol, this feature is not commonly available to today's consumers.
In view of the above, it would be desirable to have techniques for implementing mobility in nodes without implementing mobility support (e.g., Mobile IP software) in the nodes themselves.
SUMMARY OF THE INVENTION
The present invention provides methods and apparatus for enabling a node that does not support Mobile IP to roam to various Foreign Agents so that it may receive packets sent to it by a corresponding node. This is accomplished, in part, through enabling a Foreign Agent to independently perform registration on behalf of the node. In addition, a Home Agent associated with the node independently performs de-registration on behalf of the node when the node roams to a Foreign Agent from the Home Agent or another Foreign Agent. It is important to note that this is achieved without any communication from the node indicating its desire to register or de-register. Moreover, because the node does not implement the Mobile IP protocol, it is desirable to implement a virtual Foreign Agent suc
Dommety Gopal K.
Leung Kent K.
Beyer Weaver & Thomas LLP
Cisco Technology Inc.
Lim Krisna
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