AppleTalk is a stateful communication protocol, requiring a secured connection between the client and the server. Although it is possible to log in anonymously as a "guest," a login is still required. Other stateful protocols include FTP, IRC and Telnet as well as any other protocol that requires a client to "log in" to a resource.
Mac OS does support stateless communication protocols as well. For example, it is possible to use HTTP or other methods for sharing files using a browser on the Mac OS client. For example, Personal Web Sharing, bundled with the Mac OS operating system, allows the sharing of directory information over HTTP.