| TACACS+ | Terminal Access Controller Access-Control System Plus | Used for centralized access control to routers. | Security | Like a ticketing system for the entire network. | |
| TCP/IP | Transmission Control Protocol/Internet Protocol | A core protocol suite for internet data transmission. | Network & Infrastructure | Manages packet delivery and splits data into parts. | |
| TDD | Test-Driven Development | Development driven by testing. | Testing & Quality | Write the test first, then the code. Convenient if you're not lazy. It's like setting the table before taking food out of the fridge. But to each their own, of course. | |
| TLS | Transport Layer Security | An encryption protocol for secure data transmission. | Security | Replaced SSL. | SSL |
| TML | Topic Maps Language | A language for creating knowledge maps. | Data | For creating knowledge maps. | |
| TOTP | Time-based One-Time Password | A one-time password that changes every 30 seconds. | Security | Used in two-factor authentication. | |
| TSV | Tab-Separated Values | Data separated by tabs. | Data | Like CSV, but with tabs. | |
| TTL | Time To Live | The time a packet lives on the network. | Network & Infrastructure | If it expires, the packet is dropped. | |
| TUI | Text User Interface | An interface in the terminal. | General | Like GUI, but text-based. | GUI |