TOPS (file Server) - TCP/IP Support

TCP/IP Support

After the Sun purchase, TOPS was given the problem of making a client that could also access Sun file shares using NFS. Centram solved this problem by porting their file sharing protocol to TCP/IP. This was not trivial; neither Mac OS nor Windows supported TCP/IP "out of the box", so what was now the TOPS Division of Sun had to write a complete IP stack for the Mac and Windows. Centram had already written such a stack for their "TOPS Terminal", a freeware (but not open source) Telnet terminal for the Mac.

Additionally, the majority of Macintosh systems used LocalTalk (or PhoneNet) for connectivity, and could not be directly connected to the Ethernet-based Unix LANs. They worked around this problem by supporting an emerging LocalTalk-to-Ethernet bridging standard known as "KIP", short for Kinetics Internet Protocol. KIP encapsulated TCP/IP packets inside AppleTalk packets, allowing them to be sent over existing LocalTalk connections. Dedicated KIP-supporting network bridges were available that stripped off the AppleTalk packaging, re-formed the IP packets inside, and sent them out over Ethernet.

One limitation of the TCP stack was that it did not support DNS, requiring users to type in IP addresses of the peers they wanted to communicate with. In a network of mostly Macs or Windows PCs this was not an issue, as DNS was not widely used with these systems at that time. KIP also reduced the need for DNS, as it allowed a Mac's existing Address Resolution Protocol (AARP) code within AppleTalk to look up the AppleTalk address of the remote peer, and then communicate with the TOPS stack on that machine to find the corresponding IP address.

TOPS also added the new "InBox Personal Connection" e-mail system, first developed by Symantec.