| Abbreviation | Definition |
|---|---|
| ISSU | In-Service Software Upgrade |
| IST | Information Switching Technology |
| ISUP | ISDN User Port |
| IT | Information Technology |
| ITG | Intelligent Transparent And Guaranteed |
| ITG | Internet Telephony Gateway |
| ITIS | Information Technology Infrastructure Services |
| ITN | Industry Trend Networking |
| ITOC | IMS (Infrastructure Management Services) TCP/IP (Transmission Control Protocol / Internet Protocol) OTMA (Open Transaction Manager Access) Connection |
| ITOC | IMS TCP/IP OTMA Connection |
| ITOT | ISO Transport service On top of TCP |
| ITRDS | Improved Trust based Replica Detection System |
| ITSP | Information Technology Service Provider |
| ITSP | Internet Telephone Service Provider |
| ITT | Invitation To Transmit |
| IUL | Internet Unlimited, Ltd. |
| IUNC | International Universities Networking Conferences |
| IVAD | Integrated Virtual Access Data |
| IVAD | Integrated Virtual Access Datacommunications |
| IVCN | Inter-Vehicle Communication Networks |