| Abbreviation | Definition |
|---|---|
| STM-16 | 2488.320 Mbits/ Second |
| STM-4 | 622.080 Mbits/ Second |
| STN | Small Town Network |
| STOMP | Simple Text Oriented Messaging Protocol |
| STP | Server Time Protocol |
| STP | Spanning Tree Protocol |
| STPX | Spanning Tree Protocol Extensions |
| STR | Send Terminate Request |
| STR | Short Tandem Repeats |
| STS | Seed To Succeed |
| STS | Station To Station |
| STS | Synchronous Transport Services |
| STS | Synchronous Transport Signal |
| STS | Synchronous Transport System |
| STUN | Serial TUNneling protocol |
| STUN-SDLC | Serial TUNneling protocol with Synchronous Data Link Control |
| SU | Scan Udp |
| SU | Scroll Up |
| SU | Simultaneous Users |
| sub-CA | sub-certificate authority |