> ## Documentation Index
> Fetch the complete documentation index at: https://docs.contactswing.ai/llms.txt
> Use this file to discover all available pages before exploring further.

# Inbound SIP Calls

Learn how to set up and manage inbound SIP calls. This guide shows you how to configure inbound calling effectively.

## What is SIP?

**Session Initiation Protocol (SIP)** is a protocol for starting, managing, and ending real-time voice and video calls over the internet. SIP uses VoIP (Voice over Internet Protocol), so you can make calls online instead of using traditional phone lines.

## Why use SIP?

SIP offers several advantages over traditional calling:

* **Cost-effective**: Make calls over the internet and reduce long-distance charges.
* **Scalable**: Add or remove phone numbers without extra hardware.
* **Flexible**: Make and receive calls from computers, mobile devices, or VoIP phones.
* **High call quality**: Enjoy better audio with a stable internet connection.
* **Business integration**: Connect SIP with CRM, call centers, and other tools for efficiency.

***

## SIP domain for incoming calls

Send calls to this SIP domain:

```
bluespace.sip.twilio.com
```

***

## Call routing

Configure your phone number to an assistant. For example, if assistant ID 443 is linked to `+12359845123`, initiate the SIP call to:

```
+12359845123@bluespace.sip.twilio.com
```

Our system automatically identifies the number and routes the call to **Assistant 443** for handling. 🤖

***

## Important note

The assistant must be an **inbound assistant** to receive calls using phone/SIP.