The Internet Adapter (TIA). A program from Cyberspace Development which runs on a Unix shell account and acts as a SLIP emulator. A TIA emulated SLIP account is not quite the same as a real SLIP account but TIA's SLIP emulation is completely standard in terms of working with MacTCP-based software on the Macintosh (or WinSock on a Microsoft Windows machine).
You do not get your own Internet Address as you do with a real SLIP account, instead, TIA uses the IP number of the machine it runs on and "redirects" traffic back to you. You cannot set up your machine as an FTP server, for instance, since there's no IP number for an FTP client elsewhere to connect to.