| ACD | Average Call Duration — Mean time a call lasts. |
| ANI | Automatic Number Identification — Identifies the caller’s number. |
| ASR | Answer-Seizure Ratio — Ratio of answered to attempted calls. |
| B2BUA | Back-to-Back User Agent — VoIP architecture for media and signaling control. |
| CDR | Call Detail Record — Metadata generated for a telecom transaction. |
| CLD | Calling Line Destination — Identifies the called party’s number in a VoIP call setup. |
| CLI | Calling Line Identification — Displays the caller’s phone number. |
| CNAM | Caller Name — Displays the name associated with the caller’s number. |
| CPE | Customer Premises Equipment — Devices installed at a customer’s location. |
| CPaaS | Communications Platform as a Service — Telecom services offered via cloud. |
| Codec | Audio compression methods (G.711, G.729, Opus) used in VoIP. |
| DID | Direct Inward Dialing — Allows external callers to reach an internal extension. |
| DNIS | Dialed Number Identification Service — Identifies the number dialed by the caller, used for routing inbound VoIP calls. |
| DS0/DS1/DS3 | Digital Signal Levels — T-carrier transmission system levels (e.g., DS1 = T1 line). |
| DTLS | Datagram TLS — Used in WebRTC encryption. |
| DTMF | Dual Tone Multi-Frequency — Signals used for dialing and input (touch-tone). |
| E.164 | Numbering Format — International telephone numbering standard. |
| E911 | Enhanced 911 — Provides caller location info to emergency services. |
| ENUM | Telephone Number Mapping — Converts phone numbers to Internet addresses. |
| FAS | False Answer Supervision — Fraudulent call charge without real connection. |
| ICE | Interactive Connectivity Establishment — Helps with NAT traversal in VoIP. |
| IVR | Interactive Voice Response — Automated telephony system for user interaction. |
| Jitter | Variation in packet arrival time that can affect voice quality. |
| Jitter Buffer | Helps to smooth audio variations in VoIP packets. |
| LATA | Local Access and Transport Area — Geographic area for call routing. |
| LEC | Local Exchange Carrier — Provides local phone service. |
| LNP | Local Number Portability — Keep phone numbers when changing providers. |
| Latency | Delay between sending and receiving data. |
| MOS | Mean Opinion Score — Subjective quality rating of voice (1–5). |
| NPA-NXX | Numbering format: NPA = area code; NXX = central office code. |
| PBX | Private Branch Exchange — Internal phone switching system in organizations. |
| PDD | Post Dial Delay — Time from call initiation to ringing. |
| POTS | Plain Old Telephone Service — Basic analog phone service. |
| PRI | Primary Rate Interface — ISDN line with multiple voice/data channels. |
| PSTN | Public Switched Telephone Network — Traditional circuit-switched network. |
| QoS | Quality of Service — Measures reliability and performance of telecom service. |
| RTP | Real-Time Transport Protocol — Used for transmitting audio/video streams. |
| Rate Center | A geographic area used to determine local vs. long-distance calls. |
| SBC | Session Border Controller — Secures and manages VoIP traffic. |
| SDC | Short Duration Calling — Often used in VoIP fraud detection and SIP trunk analysis. |
| SHAKEN/STIR | Caller ID verification to prevent spoofing. |
| SIP | Session Initiation Protocol — Initiates and manages VoIP calls. |
| SIP Proxy | A SIP server that routes and forwards SIP requests, enforcing policy and facilitating call setup. |
| SIP Trunk | Virtual VoIP trunk line — Replaces traditional PRI. |
| SIPS | SIP over TLS — Secure VoIP signaling. |
| SRTP | Secure RTP — Encrypts RTP media streams. |
| STUN/TURN | Servers to support NAT traversal in real-time communications. |
| T.38 | Protocol for Fax over IP (FoIP). |
| TLS | Transport Layer Security — Encrypts communications over IP. |
| UCaaS | Unified Communications as a Service — Integrated voice, video, messaging. |
| VoIP | Voice over Internet Protocol — Sends voice over IP networks. |
| WebRTC | Web Real-Time Communication — Browser-based real-time media exchange. |