A Systems Design for a Hybrid Network Data Communications Terminal Using Asymmetric TCP/IP to Support Internet Applications
December 31, 1994
Access to the Internet is either too slow (e.g. dial-up SLIP) or too expensive (e.g. switched 56 kbps, frames relay) for the home user or small enterprise. The Center for Satellite and Hybrid Communications Networks and Hughes Network Systems have collaborated using systems integration principles to develop a prototype of a low-cost hybrid (dial-up and and satellite) network terminal which can deliver data from the Internet to the user at rates up to 160 kbps. An asymmetric TCP/IP connection is used breaking the network link into two physical channels: a terrestrial dial-up link for carrying data from the terminal into the Internet and a receive-only satellite link carrying IP packets from the Internet to the user. With a goal of supporting bandwidth hungry Internet applications such as Mosaic, Gopher, and FTP, this system has been designed to support any Intel 80386/486 PC, any commercial TCP/IP package, any unmodified host on the Internet, and any of the routers, etc. within the Internet. The design exploits the following three observations: 1) satellites are able to offer high bandwidth connections to a large geographical area, 2) a receive-only VSAT is cheap to manufacture and is easier to install than one which can also transmit, and 3) most computer users, especially those in a home environment, will want to consume much more data than they generate. IP encapsulation, or tunneling, is used to manipulate the TCP/IP protocols to route packets asymmetrically.