Terminal Interface Unit

The Terminal Interface Unit (usually referred to by the acronym, TIU) was a software package created by SRI which ran on a PDP-11 and allowed a number of users at terminals to connect to time-sharing hosts over the nascent prototype Internet, using TELNET over TCP/IP. It was initially targeted at use over the prototype Packet Radio Network, but was later eventually adapted to operate attached to the ARPANET.

It is historically important, as one of the very earliest TCP/IP implementations (although its origins date back to before the separation of TCP and IP into separate protocols). It was one of 6 prototype implementations of TCP/IP tested at the ground-breaking 'TCP Bakeoff' held at ISI on 27 January, 1979 (likely the very earliest attempt to get different TCP implementations to connect to each other), along with:

• UNIX Sixth Edition from BBN in MACRO-11 (itself a port of the TIU implementation)
• UNIX Sixth Edition from BBN in C
• TENEX for the PDP-10 from BBN
• OS/MVT for the IBM 360 from UCLA
• Multics from the MIT Laboratory for Computer Science (LCS)

It was initially able to connect to networks which used the 1822 interface, using the Stanford 1822 Interface‎, and later the the ACC MLH-DH/LSI11.

Software

The TIU was written in MACRO-11, and ran on the MOS operating system‎ (created at the time of the TIU work). The code and documentation have been saved (see links below). (The code there has been modified to operate over a local area network built at LCS, but the TCP and IP layers are essentially un-modified.)

See also

• ANTS terminal system
• ELF operating system
• Fuzzball

External links

• Terminal Interface Unit - source code
• Terminal Interface Unit - documentation (tiunv?.lpt)
• TCP Implementation Status - has entries for the implementations listed above