• TTY serial lines
• NIA-20 ethernet interface
• CI-20 cluster interface

IP version 4 is implemented in some distributions of tOPS-20.

• TELNET

• Mail

• FTP

• Client end

• Server end

DECnet is the proprietary network protocol designedby Digital EquipmentCorporation for communication between diffrent hosts runnning operatingsytems such as TOPS-20, TOPS-10, VMS, RSX etc. Implementations exist also for other operating systems,such as Sun/Solaris and GNU/Linux.

• OPR/NCP

• SET HOST

• MAIL

• Client end

• Server end

ChaosNet is an optional protocol designed primarily for communication with and between MIT CADR Lisp Machines. implementations (maybe experimental) may exist for some TOPS-20 distributions.