Custom VoIP Integration

TLS (SRTP) Encryption

Secures your VoIP traffic by encrypting both the signaling (via TLS) and media (via SRTP). Activate this toggle only if your VoIP provider requires it.

When to Enable It:

• Your SIP provider specifically mentions TLS or SRTP support.
• You want to ensure secure, encrypted voice communication (e.g., for compliance or privacy reasons).

When to Leave It Off:

• Your provider doesn’t support TLS/SRTP, enabling it may block calls or cause failed connections.
• You’re using basic test environments or local SIP servers without encryption.

Authentication Methods

Inbound calls require at least one authentication method. Enable IP Address and/or Credentials authentication (you can use both).

IP Address Authentication:Allow traffic from specific IP addresses, ideal if your VoIP infrastructure has a static IP.IP Address: Enter the public IP address(es) of your SIP servers so we can accept and process requests from them.

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Credentials Authentication:Use a username and password to authenticate each incoming SIP request.Username: 2–32 characters, using letters, digits, hyphens (-) and underscores (_) only.
Password: At least 12 characters, with at least one uppercase letter, one lowercase letter, and one digit. Letters and digits only — special characters are not allowed.

This method is useful if your infrastructure is cloud-based and IPs can change, or you want multi-tenant control.

Copy Your SIP Domain

After you save the inbound configuration, NLPearl generates a SIP Domain for this number. This is what tells your provider where to send incoming calls so they reach the platform.

The SIP Domain isn’t something you type. It’s created automatically and shown read-only at the top of the Inbound Configuration card, with a Copy button. It only appears once the inbound configuration has been saved, so reopen the card afterward to retrieve it.

To finish connecting inbound calls:

1. Save the inbound configuration, then reopen the Inbound Configuration card.
2. Copy the generated SIP Domain.
3. Add it to your VoIP provider / PBX as the destination for inbound calls, so your operator routes incoming calls to NLPearl.
4. If you enabled Credentials Authentication, also add the username and password you defined here to your VoIP settings so authentication succeeds.

TLS (SRTP) Encryption

Secures your VoIP traffic by encrypting both the signaling (via TLS) and media (via SRTP). Activate this toggle only if your VoIP provider requires it.

When to Enable It:

• Your SIP provider specifically mentions TLS or SRTP support.
• You want to ensure secure, encrypted voice communication (e.g., for compliance or privacy reasons).

When to Leave It Off:

• Your provider doesn’t support TLS/SRTP, enabling it may block calls or cause failed connections.
• You’re using basic test environments or local SIP servers without encryption.

SIP Trunk URL

This is the address your outbound calls will be sent to, typically provided by your VoIP provider. Enter it as a domain or IP address (this is where your calls will be routed).

User Part

This is the SIP user identity used in the “From” header of your outbound SIP requests. It’s how your VoIP system identifies the origin of the call.What to enter: You can use one of the following formats depending on your provider:

• A SIP username (e.g. caller01)
• A DID or phone number in E.164 format (e.g. +1234567890)
• An extension (e.g. 201)
• A SIP URI (e.g. caller01@example.com), less common

Data Center

Select the network edge closest to your VoIP infrastructure to optimize call routing and reduce latency. Eight regions are available:

Region	Location
North America	Virginia
North America	Oregon
Europe	Ireland
Europe	Frankfurt
Asia Pacific	Singapore
Asia Pacific	Tokyo
Asia Pacific	Sydney
South America	São Paulo

Transfer Call Using SIP Refer

This toggle enables or disables call transfers using the SIP REFER method. It is enabled by default.When enabled, it allows:

• Transferring a live call from one destination to another without media proxying
• Offloading media streams directly between endpoints
• Reducing latency and server load

If you disable SIP REFER, NLPearl’s servers stay in the media path during transfers, which results in additional costs. Leave it on unless your provider doesn’t support SIP REFER.

Authentication Methods (optional based on your VoIP)

Credentials Authentication:Use this method if your VoIP provider requires username/password credentials to authenticate outbound calls.Username: This is the identifier associated with your SIP account.Password: A secure password used to authenticate the SIP user. Make sure it meets your provider’s security requirements (e.g. minimum 12 characters, including upper/lowercase letters, a number, and a special character).

Header-Based Authentication:Use this method if your VoIP provider requires custom headers for SIP request authentication.Header Key: This is the name of the custom SIP header field expected by your provider (e.g., X-Custom-Auth, X-Access-Token, etc.).Header Value: The corresponding value used to validate the request (e.g., a token, API key, or static secret). Example: AuthZ-87!t!link

Header-based auth is typically used for advanced integrations or when SIP gateways are behind proxies/firewalls that don’t support IP or credential-based auth. Ensure this matches exactly what your provider expects, as even small typos (like case or symbols) can lead to rejections.

You can add several key-value pairs if needed, for example, to meet multi-token security policies.

• IP Address Allow List:
  IP Address: See Twilio’s SIP Trunking IP Addresses.