Mobile point-to-point protocol

Details Mobile point-to-point protocol Mobile point-to-point protocol

1998-05-08

2004-10-05

Kizou, Hassan (Department: 2662)

Multiplex communications

Communication over free space

Having a plurality of contiguous regions served by...

C370S331000, C455S432300, C455S436000, C455S439000, C455S440000

Reexamination Certificate

active

06801509

ABSTRACT:

FIELD OF THE INVENTION
This invention relates generally to communications and, more particularly, to packet communications systems.
BACKGROUND OF THE INVENTION
One use of the Internet as a communications vehicle is as an enhanced data backbone for coupling together workgroups to provide what is referred to as a “virtual private network” (VPN). One application of a VPN is in a corporate environment such that employees, e.g., at home, can remotely access, via the Internet, corporate data networks. A VPN provides security, and authentication, for a remote user to join a closed user group notwithstanding the use of public facilities. In effect, the use of a VPN provides a WAN-like vehicle to the corporation and its employees. (Although the corporate network could also provide direct remote access, e.g., a user dials directly into the corporate network, there are economic advantages to the use of a VPN.)
To provide a VPN, tunneling protocols are used such as the “Point-to-Point Tunneling protocol” (PPTP) and the “Layer 2 Forwarding” (L2F) protocol. Generally speaking, a tunnel protocol enables the creation of a private data stream via a public network by placing one packet inside of another. In the context of a VPN, an IP packet is placed inside another IP packet. In an attempt to develop an industry standard, the Internet Engineering Task Force (IETF) is developing the “Layer 2 Tunneling Protocol” (L2TP), which is a hybrid of the PPTP and L2F protocols (e.g., see K. Hamzeh, T. Kolar, M. Littlewood, G. Singh Pall, J. Taarud, A. J. Valencia, W. Verthein;
Layer Two Tunneling Protocol “L
2
TP”;
Internet draft, March, 1998).
For a remote user, a typical form of access to a VPN is via a “plain-old-telephone service” (POTS) connection to an “Internet service provider” (ISP) that provides the VPN service. For example, a user incorporates an analog modem into a personal computer, or equivalent, and has a customer account with a particular ISP, referred to herein as the “home” ISP. (It is also assumed that the user's personal computer is properly configured to support one of the above-mentioned tunneling protocols.) The user accesses the VPN by simply making a data call to the home ISP, e.g., dialing a telephone number associated with the “home” ISP and then “logging in” to the VPN.
SUMMARY OF THE INVENTION
Access to an ISP is via a network access server (NAS). We have realized that in a Personal Communications Service (PCS) wireless environment the above-described tunneling protocols do not allow a remote user, on an existing call, to change the NAS that is providing access to a VPN. As such, the user's physical mobility may disconnect, or drop, the user from the existing VPN connection.
Therefore, and in accordance with the invention, an NAS or LAC incorporates a “hand-off” feature that allows an existing PPP connection to be transferred from one NAS to another NAS.
In an embodiment of the invention, 3 new control messages are defined for use in an NAS. Namely: (i) Continued Call Request, (ii) Continued Call Reply, and (iii) Continued Call Connect. These 3 new control messages comprise a L2TP control message header, message identifier (e.g., continued call request, etc.), and a number of fields.
As a result of the above, the user does not have to terminate the current PPP connection and then re-establish a new PPP connection.


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K. Hamzeh, T. Kolar, M. Littelwood, G. Singh Pall, J. Taarud, A. J. Valencia, and W. Verthein; “Layer Two Tunneling Protocol L2TP”; Internet Draft, Mar. 1998.

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