Adding a SIP-IN line

Session Initiation Protocol (SIP) technology allows voice calls and other communication services to be carried over the internet.

You can use SIP-IN for receiving calls from the internet. SIP-OUT, for making outbound calls on the internet, isn't currently supported.

For information about how to add a standard Public Switched Telephone Network (PSTN) phone number, see Adding phone numbers.

This article contains the following topics:

About SIP-IN lines

Understanding SIP-IN technical requirements

Understanding SIP-IN line limitations

Adding a SIP-IN line

Deleting SIP-IN lines

About SIP-IN lines

When you add a SIP-IN line, you can accomplish the following:

Call escalation from an AI agent: Connect a third-party AI agent to escalate calls to Zendesk agents when the AI agent cannot resolve the customer's query. See Connecting an external AI agent using a SIP-IN line.

Bring Your Own Carrier (BYOC): Use local carriers and forward calls to Zendesk via SIP to operate your business in that country.

Call forwarding: Forward calls into Zendesk via SIP-IN without paying PSTN rates for call forwarding.

Third-party application (external IVR) forwarding: Connect with partner apps during the call flow, such as an external IVR, to enable a more complex and integrated service experience.

Understanding SIP-IN technical requirements

Use the following information to help you understand the technical requirements for SIP-IN lines:

An AI agent must be able to place a call to a SIP-IN line address, (for example, mongoose@mongoose.sip.twilio.com) configured in Admin Center. Zendesk uses Twilio’s (our service provider's) SIP. Any user can be dialed on the defined SIP URI. The phone number passed in the SIP URI From header field is used to associate an existing user profile with the ticket.

Zendesk employs IP access control lists. IP ranges from third parties can be defined in Admin Center. We don't employ any other authentication method such as username and password to authenticate SIP-IN calls.

SIP-IN lines are compatible with omnichannel routing. When a ticket is generated by the AI agent, it's routed to agents based on their availability and capacity if you've created omnichannel routing rules.

When creating a ticket to associate to a SIP call, you must set the via_id to 34 as described in the Zendesk developer documentation. This identifies it as an incoming voice call ticket in Zendesk Support. Then, when making the call, include the SIP header: X-Zendesk-Ticket-Id=<ticket number>.

Twilio voice media IPs use a single global range: 168.86.128.0/18 with a UDP port range 10000-60000

Our provider supports G.711 μ-law (PCMU) and A-law (PCMA) codecs for media.

SIP-IN lines work with your interactive voice response (IVR) trees. See Routing incoming calls with IVR.

SIP-IN lines are compatible with customer callback.

SIP-IN lines use TLS for SIP signaling and SRTP for media, if enabled in SIP line settings.

Devices in your network that communicate directly with Zendesk SIP must be configured to trust Twilio's TLS/SSL Certificate, as Twilio is our service provider. Use Twilio's bundle of trusted CA certificates.

TLS support:

TLS 1.2+

Ciphers: ECDHE-RSA-AES128-GCM-SHA256, ECDHE-RSA-AES128-SHA256, ECDHE-RSA-AES256-GCM-SHA384, ECDHE-RSA-AES256-SHA384, AES128-GCM-SHA256, AES128-SHA256, AES128-SHA, AES256-GCM-SHA384, AES256-SHA256, AES256-SHA.

And, SRTP support:

Inbound to Zendesk (origination): AES_CM_128_HMAC_SHA1_80 and AES_CM_128_HMAC_SHA1_32

Outbound from Zendesk (termination): AES_CM_128_HMAC_SHA1_80

Master Key Identifier (MKI) isn’t supported.

Understanding SIP-IN line limitations

The following limitations currently apply when you create SIP-IN lines:

Only SIP-IN is available for this release; SIP-OUT isn't currently supported for outbound calls.

Failover functionality isn't supported on a SIP-IN line.

SIP-IN lines cannot be configured using APIs. They can only be set up in Admin Center.

You can’t place outbound calls from a SIP-IN line. In the case of call overflow and agent forwarding, you’ll need to choose an external PSTN number for outbound calls.

You can’t block numbers from a SIP-IN line.

SIP requests originating from external Twilio accounts using TwiML (Twilio Markup Language) to initiate SIP calls aren't supported. This includes scenarios such as calls initiated from a Twilio IVR.

Adding a SIP-IN line

Talk admins can create SIP-IN lines.

To add a SIP-IN line

In Admin Center, click Channels in the sidebar, then select Talk and email > Talk.

Click the Lines tab, where you can review your existing phone numbers, digital lines, and SIP lines and add new ones.

Click Add Line > Add SIP line.

On the SIP configuration tab, configure the following settings:

Nickname: Enter a unique name for the SIP line. You'll need this to identify the line in reports, integrate it with your apps, and let your agents know the SIP line they are being called on.

URI: Enter the SIP URI. This address is the URI of your SIP-IN line created in Zendesk, for example mtest-zendesk@sip.twilio.com. You use this URI to send calls to Zendesk.

Secure media (TLS/SRTP): Turn this on to encrypt SIP signaling with TLS and audio with SRTP for this SIP-IN line. When enabled, non-encrypted calls to this line are rejected. This setting is per line and is off by default.

Authentication: Click Add IP address range to add a range of allowed IP addresses in the form of a CIDR (Classless Inter-Domain Routing) address. Authentication is based on the source IP address of the SIP request.

On each tab of the line settings page, configure the settings you want using the following articles as a reference:

Settings tab: See Managing line settings.

Voicemail tab: See Configuring voicemail options.

Routing tab: See Routing incoming calls to groups of agents.

Call recording tab: See Managing call recording options.

Note: Not all of the settings will be available for SIP lines.

When you're finished, click Save.

Your SIP-IN line is now set up.

Editing SIP-IN lines

After you’ve created a SIP line, you can edit its settings if you want to change anything.

To edit a SIP line

In Admin Center, click Channels in the sidebar, then select Talk and email > Talk.

From the list of SIP lines, click the gear icon ( ) next to the SIP-IN line you want to edit, and then select Edit.

Edit the settings as required using the instructions in the Adding a SIP-IN line section.

Click Save changes.

Deleting SIP-IN lines

After you’ve created a SIP line, you can delete it if you no longer need it.

To delete a SIP line

In Admin Center, click Channels in the sidebar, then select Talk and email > Talk.

From the list of SIP lines, click the gear icon ( ) next to the SIP line you want to delete, and then select Delete.

Click Delete SIP line to confirm you want to delete the SIP line.