Patent ID: 6473413
Filing Date: 2002-10-29
Classification: H04L,H04W

Abstract:
A method for routing datagrams across wireless networks, said wireless networks comprising a plurality of wireless LANs each located in a unique IP subnet, comprising the steps of:providing a Home Agent and a Home Access Point for a mobile station at its initial wireless LAN; providing a first Foreign Agent and a first Access Point for said mobile station at a first destination wireless LAN; receiving a reassociation request frame from said mobile station when said mobile station roams directly from said initial wireless LAN to said first destination wireless LAN; sending a handoff request frame from said first Access Point to said first Foreign Agent after finishing a reassociation procedure; using the MAC address of said mobile station to lookup the IP address of said Home Agent in the registration table of said first Foreign Agent when said mobile station has successfully registered to said first Foreign Agent; establishing a proxy IAPP table in said first Foreign Agent for said mobile station, said proxy IAPP table comprising the MAC address of said mobile station, and the source IP address of said handoff request frame; forwarding said handoff request frame to said Home Agent according to said IP address of said Home Agent found in said registration table; looking up the IP address of last Foreign Agent for said mobile station in said registration table of said Home Agent; when said IP address of the last Foreign Agent is found, forwarding said handoff request frame to said last Foreign Agent; when said IP address of said last Foreign Agent is not found, determining said last Foreign Agent being the same as said Home Agent; looking up association table and when said MAC address of said mobile station is not in said association table, broadcasting said handoff request frame in said initial wireless LAN; deleting a record of said mobile station from an association table of said Home Access Point, and then sending a unicast handoff response frame from said Home Access Point to said Home Agent in response to said broadcast handoff request frame; sending a unicast handoff response frame from said Home Agent to said first Foreign Agent according to a source IP address recorded in said proxy IAPP table of said Home Agent; sending said unicast handoff response frame from said first Foreign Agent to said first Access Point according to said source IP address recorded in said proxy IAPP table of said first Foreign Agent; and deleting a record from the handoff list of said first Access Point when said mobile station has ever sent a handoff request frame, thereby to complete a handoff request procedure.