SDI Seminar

Speaker: Dave Johnson

Transparent Mobile Host Internetworking

Date: September 16, 1993

Abstract: Mobile hosts such as notebook and palmtop computers or portable workstations cannot currently participate easily or conveniently in the Internet due to the operation of IP's addressing and routing algorithms. A host's IP address encodes the network number to which the host is connected, which prevents IP packets from reaching the host if it moves to a new location and connects to the Internet within a different network. Changing the IP address of a host when it moves is difficult or impossible (particularly while keeping existing transport level connections open), and thus a solution is needed for correctly routing packets to the host in its current location given the host's (constant) IP address. This problem is in general also not unique to IP, since any packet switching protocol using hierarchical addressing and routing faces similar problems in trying to integrate mobile hosts into the network.

This talk presents a protocol for transparently routing IP packets to mobile hosts anywhere in the Internet, and identifies some remaining open problems for providing true transparent mobile host internetworking. The protocol is simple and requires few changes to existing protocol software. In particular, no changes to non-mobile hosts or to backbone routers in the Internet are required. The protocol scales better to large numbers of mobile hosts and adds less overhead to the network than previously proposed mobile IP protocols. The protocol allows any host running the correct software to become mobile at any time, yet there is no penalty for a host being ``mobile capable,'' since the protocol automatically uses only the standard IP routing mechanisms and adds no overhead to IP when a mobile host is currently connected to its home network.