Telecommunications – Radiotelephone system – Zoned or cellular telephone system
Reexamination Certificate
2000-02-28
2003-02-18
Trost, William (Department: 2683)
Telecommunications
Radiotelephone system
Zoned or cellular telephone system
C455S437000, C455S525000, C370S331000, C370S332000
Reexamination Certificate
active
06522880
ABSTRACT:
FIELD OF INVENTION
The present invention relates to data communications in mobile networks. More specifically, it relates to the hand over of a data connection from one cell to another without tearing down the data connection.
BACKGROUND OF THE INVENTION
The Internet Protocol (“IP”) is an addressing protocol designed to route traffic within a network or between networks. The Internet Protocol is used on many computer networks including the Internet, intranets and other networks. Internet Protocol addresses are typically assigned to “immobile” nodes on a network and the IP address of each node is used to route datagrams to the node through a server connected to the node. An immobile node may be moved to a different server on the computer network, but is typically associated with a static physical location (e.g., 3Com Corporation in Santa Clara, Calif.).
In contrast, mobile nodes may connect to various physical locations on a computer network. A mobile node has its own network address and a semi-permanent relationship with a home agent or server to which the mobile node may occasionally be connected to send and receive datagrams. However, the mobile node can also connect to a foreign agent through which it sends and receives datagrams. An example of one protocol that facilitates communication with mobile nodes over the Internet is the Mobile Internet Protocol (Mobile IP), which allows “mobile” nodes to transparently move between different Internet Protocol sub-networks (“subnets”). Mobile IP is described in Request for Comment (RFC) 2002 IP Mobility Support, C. Perkins, October 1996, herein incorporated by reference, available from the Internet Engineering Task Force (IETF) at www.ietf.org.
Other protocols are also used to support mobile node communications. Often, protocols typically utilized in non-mobile applications, such as the Internet Protocol (IP) and the Point to Point protocol (PPP), are layered on top of a lower level mobile protocol, such as the Radio Frequency Link Protocol (RLP) defined by the International Telephone Union (ITU). However, the use of these non-mobile applications can create inefficiencies as mobile nodes move from one service area to another and connections are broken and reformed accordingly.
Internet Protocol addresses are typically assigned to mobile nodes based on their home Internet Protocol subnet. The home subnet is connected to an external network (e.g., the Internet or an intranet) with a “home agent” that serves as the subnet's gateway router. As is known in the art, the gateway connects computer networks using different networking protocols or operating at different transmission capacities. As is known in the art, a router translates differences between network protocols and routes data packets to an appropriate network node or network device. When a mobile node “roams,” (i.e., dynamically changes its physical location), it periodically transmits “agent solicitation” messages to other gateway routers. A mobile node also listens for “agent advertisement” messages from other gateway routers. When a mobile node receives an agent advertisement message indicating that it is now on a foreign subnet, it registers with the foreign gateway router or “foreign agent” and its home agent. The registration with the home agent indicates that the mobile node is away from “home” (i.e., away from its home subnet). The registration with the foreign agent allows the mobile node to receive data on the foreign subnet.
FIG. 1
shows an architecture
10
that illustrates an example of the connection of a mobile node
20
to public IP network
70
. Public IP network
70
includes two foreign agents
30
and
40
that act as tunnel initiators responsive to the establishment of a link with mobile node
20
. The network also includes a tunnel endpoint server
50
that is the home agent for mobile node
20
in this example.
When mobile node
20
receives an agent advertisement broadcast from tunnel initiator
30
, the mobile node establishes a first link
22
with tunnel initiator
30
. Link
22
is a radio frequency communication link between mobile node
20
and tunnel initiator
30
. An example of a protocol for link
22
is the Radio Frequency Link Protocol (RLP). Tunnel initiator
30
is a foreign agent for mobile node
20
and, as part of establishing link
22
, receives infonnation regarding a home agent from mobile node
20
. Note that the information received by tunnel initiator
30
from mobile node
20
also includes the Mobile Identification Number (MIN) for mobile node
20
. Using the mobile node's home agent information, tunnel initiator
30
establishes L2TP tunnel
56
to tunnel endpoint server
50
, which is the home agent for mobile node
20
.
One example of a tunnel initiator or endpoint device is a network access server, such as that described in the patent to Dale M. Walsh et al., U.S. Pat. No. 5,528,595, which is fully incorporated by reference herein and describes an integrated network access server suitable for use in the present invention. Such a device has been commercialized widely by 3Com Corporation (previously U.S. Robotics Corp.) under the trade designation Total Control™ Enterprise Network Hub. Network access servers similar in functionality, architecture and design are available from other companies, including Lucent Technologies and Cisco Systems. The invention is suitable for implementation in network access servers from the above companies, and in other similar devices.
In protocols that support client mobility, mobile node
20
typically senses that it has lost contact with tunnel initiator
30
when it times out waiting for an advertisement message from tunnel initiator
30
. Mobile node
20
will then look for an advertisement message from a new foreign agent, such as tunnel initiator
40
. When mobile node
20
receives an advertisement message from a foreign agent, tunnel initiator
40
in this case, it sends a registration message that initiates set-up of link
24
and set-up of tunnel connection
66
. For further details relating to one example of how mobile nodes move from one foreign agent to another, see RFC 2002 regarding Mobile IP.
Registration of the mobile node
20
typically involves authentication, authorization and accounting (AAA). AAA server
80
interacts with foreign agents and other AAA servers, such as one connected to the mobile node's home network, to authorize, authenticate and perform accounting for the mobile client. To perform AAA services, the registration request from mobile node
20
to the tunnel initiator acting as the foreign agent will include a Network Access identifier (NAI), such as a Mobile Identification Number (MIN) or Electronic Serial Number (ESN), in an authentication extension of the r egistration request message. The tunnel initiator will forward the NAI to AAA server
80
that will perform the authentication and authorization, such as a Challenge and Accept Protocol (CHAP) or a cryptographic authentication. Mobility management may also be integrated with the AAA services in AAA server
80
, wherein AAA server
80
helps manage registration of the mobile node and handoff of connections between foreign agents.
The AAA server
80
can also be configured to perform tunnel endpoint identification for mobile nodes. In this case, the tunnel initiator queries the AAA server
80
with the MIN supplied by the mobile node
20
to obtain an address for a tunnel endpoint for the connection. The AAA server
80
maintains a database containing entries that match MIN values with tunnel endpoint addresses. The AAA server
80
searches the database for an entry corresponding to the MIN value in the query from the tunnel initiator. The AAA server then returns the tunnel endpoint address from the corresponding entry in a reply message to the tunnel initiator.
The Radio Link Protocol, Code Division Multiple Access (CDMA) protocol, and other mobility protocols allow a mobile node to dynamically change its network connectivity in a manner that is transparent to protocol layers above the Inte
Senthilnathan Janakiraman
Verma Rohit
3Com Corporation
McDonnell & Boehnen Hulbert & Berghoff
LandOfFree
Method and apparatus for handoff of a connection between... does not yet have a rating. At this time, there are no reviews or comments for this patent.
If you have personal experience with Method and apparatus for handoff of a connection between..., we encourage you to share that experience with our LandOfFree.com community. Your opinion is very important and Method and apparatus for handoff of a connection between... will most certainly appreciate the feedback.
Profile ID: LFUS-PAI-O-3124897