TAC
TAC (Technical Assistance Center): Sometimes used interchangeably with a NOC.

TCP
Transmission Control Protocol (TCP) is one of the primary network transport protocols that enable data transfer across the Internet. It provides a connection-based transmission model, unlike UDP which provides a connectionless transmission model. Many network services and applications communicate on various TCP ports. Nagios Core and Nagios XI are capable of monitor applications and services that communicate over TCP.

Traps
See SNMP Traps.