R
- Radio Frequency (RF)
- RADIUS (Remote Authentication Dial-In User Service)
- Random Access Memory (RAM)
- Rate Adaptation
- Rate Center
- Rate Limiting
- Real-Time Control Protocol (RTCP)
- Real-Time Operating System (RTOS)
- Reboot
- Redial
- Redundancy
- Registration
- Registration Server
- Registry
- Relay
- Remote Access
- Remote Management
- Remote Monitoring
- Remote Office
- Remote Procedure Call (RPC)
- Resampling
- Resilience
- Resiliency
- Resource Allocation
- Resource Reservation Protocol (RSVP)
- Retransmission
- RFC (Request for Comments)
- Ring Group
- Ring Tone
- Ring-Back
- Ring-Down Circuit
- Ringback
- Ringback Server
- Ringback Tone
- Ringing
- Ringing Voltage
- Robocall
- Rogue Access Point
- Rollover Lines
- Routed Network
- Router
- Routing Table
- RTP (Real-Time Transport Protocol)
