Browse Prior Art Database

Method for Multiple Tunnel Management for Seamless Mobility

IP.com Disclosure Number: IPCOM000011627D
Original Publication Date: 2003-Mar-10
Included in the Prior Art Database: 2003-Mar-10
Document File: 4 page(s) / 67K

Publishing Venue

Motorola

Related People

Gregory W. Cox: AUTHOR

Abstract

Providing efficient and seamless mobility for a group of users on a mobile network is a technically challenging problem. One means for addressing this problem is to enhance the IETF standard Mobile IP to create multiple parallel tunnels between the home agent and the mobile router. This is sometimes called bicasting in the literature. In this approach, during a handoff the home agent duplicates packets and sends them via an old tunnel (Mobile IP Tunnel 1 in Figure 1) and a new tunnel (Mobile IP Tunnel 2 in Figure 1). This greatly reduces the probability of dropping packets during handoffs. However, it also introduces the problem of duplicate packets being received by the mobile network’s clients. The duplicate packets can adversely affect the performance of the mobile network’s clients while wasting the mobile network’s bandwidth. The present method detects and eliminates these duplicate packets and determines when one of the parallel tunnels should be shut down, ending the handoff.

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Method for Multiple Tunnel Management for Seamless Mobility

Author Gregory W. Cox

Abstract                  

Providing efficient and seamless mobility for a group of users on a mobile network is a technically challenging problem.  One means for addressing this problem is to enhance the IETF standard Mobile IP to create multiple parallel tunnels between the home agent and the mobile router.  This is sometimes called bicasting in the literature.  In this approach, during a handoff the home agent duplicates packets and sends them via an old tunnel (Mobile IP Tunnel 1 in Figure 1) and a new tunnel (Mobile IP Tunnel 2 in Figure 1).  This greatly reduces the probability of dropping packets during handoffs.  However, it also introduces the problem of duplicate packets being received by the mobile network’s clients.  The duplicate packets can adversely affect the performance of the mobile network’s clients while wasting the mobile network’s bandwidth. The present method detects and eliminates these duplicate packets and determines when one of the parallel tunnels should be shut down, ending the handoff.

Detailed Description

Figure 1 Parallel Tunnel Management Overview

Figure 1 above overviews the operation of the present invention in an example embodiment.  In the figure, the invention is implemented in a Mobile Router.  Two parallel tunnels are active between the Home Agent and the Mobile Router; the mobile network is in the midst of a handover.  The Correspondent Node is transmitting three different packet streams using different transport protocols to the Client on the Mobile Network.  Colors (orange, blue, light green) and numbering schemes (a-f, A-E, 1-6) differentiate these streams and protocols.

Since the Mobile Router operates at the IP layer, it cannot easily employ packet duplicate detection mechanisms implemented in transport protocols such as TCP.  For one thing, employing such detection would generally require the Mobile Router to “snoop” into the transport layer and at least partially implement transport protocol state machines on a per-connection basis.  Further, the Mobile Router would need to understand all the transport protocols invoked by the Client and the Correspondent Node.  These factors create complexity, memory, and updating issues for the Mobile Router.

The present invention could simultaneously reside in the Home Agent in the case of reverse tunneling to avoid router ingress filtering problems.  In this case, it is likely that only the Mobile Router would decide when to tear down a parallel tunnel.  It is also possible that the teardown and tunnel selection decisions could be made jointly between the mobile router and the home agent or by the home agent alone.  While these cases are of practical interest and would be covered by any potential patent filing or publication, this description will concentrate on the actions of the present invention implemented only in the mobile router for clarity and brevity.

Figur...