How to add Programmability to your existing SIP network

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If you are looking to explore SIP functionality, we recommend following the SIP Quickstart to get you up and running in a few clicks!

Are you interested in learning how to make calls using SIP with Twilio programmability? This guide will show you how to use Programmable Voice to receive SIP inbound phone calls from your SIP infrastructure to Twilio

Twilio Programmable SIP Domain makes it possible to create Enterprise Grade features, contact center feasible functionality in minutes. It's possible to add to programmable logic to your calls to make your business applications more intelligent. Twilio also offers global reach with its rich and reliable PSTN network.

Steps to make an inbound SIP calls

Configure SIP Domain
Configure your SIP Endpoint
Make an inbound SIP call from Twilio Registered Endpoint

Let's get started!

Configure SIP Domain

To receive SIP traffic from your network, configure a SIP Domain in Twilio. In this example, we use a Twilio Registered Endpoint to send SIP traffic to Twilio, so the following procedure enables SIP Registration and associates a credential list.

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The SIP registration steps in the following SIP Domain procedure are only required if you're using a Twilio Registered Endpoint. If you're not, skip them.

Configure a Credential List.
Twilio ConsoleLegacy Console
Open Twilio Console and go to Voice > SIP Domains > Credential Lists.

Select Create Credential List.

Enter a Credential list friendly name of Endpoint.

In the Add credentials section, enter a Username (this can be an E.164 number, extension number, or name) of UserA and a Password of yourpassword.

Select Save.

These credentials are used by your SIP Endpoints to authenticate with Twilio.
Open the legacy Console and go to Programmable Voice > Credential Lists.

Select the + icon to create a Credential List.

Add a Friendly Name of Endpoint, a Username (this can be an E.164 number, extension number, or name) of UserA, and a Password of yourpassword, then select Create.

These credentials are used by your SIP Endpoints to authenticate with Twilio.
Configure a SIP Domain.
Twilio ConsoleLegacy Console
Open Twilio Console and go to Voice > SIP Domains.

Select Create SIP Domain.

In the Properties section, enter a SIP domain friendly name of T1 and a SIP URI of Trunk1. SIP URIs must be unique across Twilio — if Trunk1 is taken, choose another name.

In the Voice authentication section, select the Endpoint credential list from Credential lists.

Select Create.

On the SIP Domain details page, find the SIP registration section and select Edit SIP registration.

Set Enable SIP registration to Enabled.

Select the Endpoint credential list from Credential lists.

Select Save.
Open the legacy Console and go to Programmable Voice > Domains.

Select the + icon to create a SIP Domain.

Add a Friendly Name of T1 and a unique SIP URI of Trunk1. SIP URI names must be unique, so you might have to find a name that is available.

Scroll down to Voice Authentication and associate the Endpoint Credential List that you created.

Scroll down to SIP Registration and select Enabled.

In the SIP Registration Authentication section, associate the Credential List that you created, then select Save.

Configure SIP Endpoint

A SIP Endpoint can be a desk phone or a softphone. In this guide we use a softphone and configure it to register with the SIP Registrar.

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If you're not using a Twilio Registered Endpoint, skip this section.

Download and install SIP Endpoint. Zoiper is used for example
Provide login name - UserA@Trunk1.sip.us1.twilio.com (do add us1 region parameter to your sip domain) and password
- Username and password from your Credential List in Twilio Console or the legacy Console.
- Yourdomain from your SIP Domain in Twilio Console or the legacy Console. For example, Trunk1.sip.us1.twilio.com (do add us1 region parameter to your sip domain while configuring zoiper).
Click "Next/continue" to confirm the Domain.
Optional settings can be skipped
Done! You see in Zoiper that it is "Registered" and has "Tick" next to your login name.
You can also verify the successfully registered endpoints in the Registered SIP Endpoints section of your SIP Domain page in Twilio Console.

Make an inbound SIP call from Twilio Registered Endpoint

It is possible to add programmable logic to your call when the call is received by Twilio. For example, we will have the code that greets the caller and make a call to your cellphone.

With Twilio you can make calls only from a verified phone number or from Twilio number. If you plan to use a number other than Twilio phone number, then go to Verified callerID page and click + to ensure your number is valid and verified.

We will now write the TwiML for our application. Because this is a static application, we will use a TwiML Bin. Visit the TwiML Bin page and click the + icon to add a new bin.

Set the Friendly Name as Greet and call and copy and paste the TwiML below:

1<?xml version="1.0" encoding="UTF-8"?>
2<Response>
3  <Say>Thank you for doing the tutorial. Will now call your cellphone</Say>
4  <Dial callerId="+1233451789">+15557650987</Dial>
5</Response>
6

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Make sure to add a verified number for callerId to dial.

Create the TwiML Bin and copy the URL, see below

TwiML Bin properties showing SID and URL with copy button.

With our TwiML Bin created, now we need to wire it up to our SIP Domain.

Open the SIP Domains page in Twilio Console or the legacy Console and select the domain you created.
Scroll down to "Voice Configuration" paste the copied URL from above to "Request URL" and click "Save"

Now go to zoiper SIP client and dial your cellphone. You will hear the greeting in zoiper and it will ring your cellphone. Congratulations, you have made your inbound SIP call.

Where to next?

Great work!

Happy hacking!