Semi-connected Tcp/ip in a Mobile Computing Environment

J rgen Sv rke Hansen Torben Reich Birger Andersen Department of Computer Science, University of Copenhagen (DIKU) Universitetsparken 1, 2100 Copenhagen, Denmark fcyller,silmaril,[email protected] Abstract We present a design of a communication layer for mobile computing, which hides the complexity of using and switching between di erent means of communication, supports disconnected operation, and makes scheduling of data possible on low bandwidth communication channels. Mobile hosts may either be connected directly to a LAN, or by a dial-up serial connection (GSM or ordinary telephone) to a Mobility Support Gateway (MSG) on the LAN. When the mobile host is directly connected to the LAN, regular TCP/IP communication is used. When a mobile host disconnects from the LAN, a TCP connection splits into two separate connections one on the serial link from the mobile host to the MSG and one on the wired network from the MSG to the peer host.