# SIP Outbound

**Receiving calls from Sinch platform to your SIP infrastructure**

You can route any type of call from the Sinch platform to your SIP server.

![Diagram showing SIP Outbound flow](/assets/sip-out.3db8946443d392bebd4406eddf29ed11a41349a2ed5a8112ede0bd7e3d6ea580.c43d86dc.png)

There are two options for routing calls: SIP forwarding and Callbacks.

### SIP forwarding

You can automatically forward calls to your SIP server using the SIP forwarding option in the Sinch Build Portal (setting available under: Voice and Video >> Apps >> Settings >> Handle call events with >> SIP Forwarding).

To Configure SIP forwarding see below SIP URIs options.

Valid SIP URIs

```shell
> sip:22444032@213.213.1.213
>
> sip:22444032@yoursipserver.com
>
> sip:22444032@yoursipserver.com:5061
>
> sip:22444032@yoursipserver.com:5061;transport=tls - optionally provide transport protocol: udp (default), tcp, or tls
>
> sip:{number}@yoursipserver.com - {number} will be replaced by the Inbound Number connected to each call
```

### X-headers

If you want a private header in incoming calls to your SIP infrastructure use `callHeaders` property in [dial](/docs/voice-2.0/api-reference/svaml#dial) action in your callback response.

Example of ICE response:

```json
{
  "action": {
    "name": "connectSip",
    "callHeaders": [
      { "key": "X-My-Private-Header-1", "value": "bar" },
      { "key": "X-My-Private-Header-2", "value": "qux" }
    ]
  }
}
```

Please note that SIP header names will be prepended with `X-`, if missing (for example `My-Private-Header` => `X-My-Private-Header`).

Limitations:

* The maximum size of private SIP headers is 1024 bytes
* Max length of header name is 50 characters


### SIP Outbound example

Example SIP INVITE sent to your SIP infrastructure:

```shell
> Request-Line: INVITE sip:+123456789@52.214.25.57:5060;transport=udp SIP/2.0
>
> Via: SIP/2.0/UDP 206.146.136.0:5060;branch=z9hG4bK04d7
>
> From: <sip:+46733478561@18.194.168.245>;tag=as386cfb27
>
> To: <sip:+123456789@52.214.25.57:5060;transport=udp>
>
> Contact: <sip:+46733478561@206.146.136.0;did=27e.fecc2a1>
>
> X-My-Header: This is my header
```