Overview
This document explains what Exotel SIP Trunking is, how it works, and what problems it solves.
What is SIP Trunking?
SIP (Session Initiation Protocol) Trunking allows you to make and receive phone calls over the internet instead of traditional telephone lines (PRI / ISDN).
With Exotel SIP Trunking, your PBX, Contact Center, or SIP-enabled system connects directly to the telephone network (PSTN) using Exotel’s cloud infrastructure.
This eliminates physical telephony hardware while enabling scalable, programmable voice connectivity.
What Exotel Provides
Exotel acts as the SIP gateway between your system and the telephone network.
- SIP signaling and media handling
- Routing to mobile, landline, and toll-free numbers
- High availability across multiple regions
- Optional routing to Voice AI using StreamKit
High-Level Architecture
Your system communicates with Exotel using SIP. Exotel handles connectivity to the telephone network.
Call Directions
Exotel SIP Trunking supports the following call directions.
Outbound (SIP → PSTN)
Your system initiates a call to a phone number.
Typical use cases:
- Agent outbound calling
- Dialer campaigns
- Click-to-call from applications
Outbound calls require your server’s public IP to be whitelisted.
Inbound (PSTN → SIP)
Your system receives calls from phone numbers.
Typical use cases:
- Customer support numbers
- IVR and call routing
- Contact center queues
Inbound calls are routed to an IP address or FQDN configured on the trunk.
StreamKit (Voice AI Routing)
In addition to PSTN routing, Exotel SIP Trunking can route calls to Voice AI bots using StreamKit.
This is enabled using mode: flow when mapping a phone number to a trunk.
Typical use cases:
- AI-powered IVR
- Voice bots
- Speech analytics
- Agent assist
Supported Routing Modes
Mode | Description |
|---|---|
pstn | Routes calls to the telephone network (default) |
flow | Routes calls to Voice AI using StreamKit |
The routing mode is configured per phone number.
What You Can Build with SIP Trunking
- Enterprise contact centers
- Outbound calling platforms
- Automated voice systems
- Voice AI integrations
- Hybrid human + bot call flows
What’s Next
- To make your first call, go to Quick Start
- To understand routing behavior, see Call Directions & Modes
- To configure SIP Trunking, see Setup