VOS3000 P-Asserted-Identity: Caller ID Manipulation Guide for VoIP

Configuring VOS3000 P-Asserted-Identity correctly is crucial for VoIP operators who need to control how caller ID information is presented to termination providers, regulatory bodies, and end users. The P-Asserted-Identity (PAI) header, defined in RFC 3325, is the industry-standard mechanism for asserting the identity of the calling party within trusted VoIP networks. Many termination vendors require specific PAI header configuration to accept calls, and incorrect PAI settings result in calls being rejected, caller ID not displaying correctly, or compliance violations that can jeopardize your entire operation.

This guide provides a complete walkthrough of VOS3000 P-Asserted-Identity configuration, including the related Privacy and P-Preferred-Identity headers, caller dial plans, and advanced caller ID manipulation techniques. All configuration details reference the official VOS3000 V2.1.9.07 Manual. For professional assistance, contact us on WhatsApp at +8801911119966.

Understanding VOS3000 P-Asserted-Identity Header

The P-Asserted-Identity header serves a specific purpose in SIP signaling that is fundamentally different from the standard From header. While the From header identifies the caller as claimed by the caller’s device, the PAI header asserts the caller’s identity as verified by a trusted network element — in this case, your VOS3000 softswitch. This distinction is critical because termination providers rely on the PAI header to determine the actual calling party for billing, routing, and regulatory compliance purposes. VOS3000 P-Asserted-Identity

Why P-Asserted-Identity Matters for VoIP Operators

In the VOS3000 ecosystem, the PAI header impacts several critical aspects of your VoIP business. Termination vendors increasingly require PAI headers to process calls correctly, especially for emergency services and regulatory compliance. Without proper PAI configuration, your calls may be rejected by vendors or flagged as suspicious. Additionally, the PAI header determines how your customers’ caller ID appears to the called party, which affects your customers’ business credibility and call completion rates.

Key reasons to configure VOS3000 P-Asserted-Identity correctly:

• Vendor requirements: Many termination providers require PAI headers to accept calls and bill correctly
• Regulatory compliance: Telecom regulations in many jurisdictions require accurate caller ID presentation
• Call completion: Proper PAI configuration prevents calls from being blocked by downstream providers
• Emergency services: Emergency call routing depends on accurate PAI for location identification
• Anti-spoofing: PAI with Privacy headers provides controlled caller ID presentation that prevents spoofing accusations

📋 Feature	🔵 From Header	🟢 PAI Header
Purpose	Caller’s claimed identity	Network-asserted identity
Trust level	Self-asserted (unverified)	Verified by trusted network
Used by vendors for billing	Sometimes	Primarily
RFC standard	RFC 3261	RFC 3325
Can include display name	Yes	Yes
Used with Privacy header	Rarely	Commonly paired

Configuring VOS3000 P-Asserted-Identity on Routing Gateway

The PAI configuration for routing gateways is located in the Additional Settings > Protocol > SIP section. Navigate to Operation Management > Gateway Operation > Routing Gateway, double-click a gateway, and access the Protocol > SIP settings (VOS3000 Manual Section 2.5.1.1, Page 43). These settings control how VOS3000 handles caller identity information when sending calls to your termination vendors.

P-Asserted-Identity Settings

VOS3000 provides three options for the PAI header on routing gateways, as documented in VOS3000 Manual Section 2.5.1.1 (Page 43):

• None: The PAI header is not included in outgoing SIP messages to this gateway. Use this when the vendor does not require or expect a PAI header
• Pass through: VOS3000 forwards the PAI header exactly as received from the mapping gateway (caller side). This preserves the original PAI value without modification, which is useful when the upstream device has already set the correct PAI
• Caller: VOS3000 generates a new PAI header using the caller’s number. This is the most common setting because it ensures the PAI contains the correct caller ID regardless of what the caller’s device sent

For most deployments, the “Caller” option is recommended because it guarantees that the PAI header contains the actual calling number from VOS3000’s perspective. The “Pass through” option should only be used when you trust the upstream device to provide accurate PAI values.

Privacy Header Configuration

The Privacy header works in conjunction with the PAI header to control whether the caller’s identity should be hidden from the called party. According to the VOS3000 Manual (Page 43), there are three Privacy options:

• None: No Privacy header is included in outgoing messages. The caller ID is presented normally
• Passthrough: VOS3000 forwards the Privacy header as received from the mapping gateway. If the caller requested privacy, that request is preserved
• Id: VOS3000 adds a Privacy: id header, which requests that the called party’s network hide the caller’s identity from display

The Privacy header is particularly important for regulatory compliance. In many jurisdictions, callers have the right to withhold their caller ID, and the Privacy: id header signals this request to downstream networks. When a call with Privacy: id is received, the called party’s network should suppress the caller ID display while still using the PAI header internally for billing and emergency services.

⚙️ Setting	🟢 Recommended	📝 When to Use Other Options
P-Asserted-Identity	Caller	Pass through: upstream PAI trusted; None: vendor doesn’t use PAI
Privacy	Passthrough	None: never hide caller ID; Id: always hide caller ID
P-Preferred-Identity	None	Passthrough: preserve upstream PPI; Caller: set from caller number
Caller dial plan	As needed	When vendor requires specific number format in PAI

P-Preferred-Identity Configuration

The P-Preferred-Identity (PPI) header is similar to PAI but is used in a different context. While PAI is used by networks to assert identity, PPI is used by user agents (phones, PBXs) to indicate their preferred identity. In VOS3000, the PPI options (VOS3000 Manual, Page 43) are identical to PAI:

• None: No PPI header is included
• Passthrough: Forward the PPI header as received from the mapping gateway
• Caller: Generate a new PPI header using the caller’s number

In most VOS3000 deployments, the PPI header is set to “None” because the PAI header is the primary mechanism for identity assertion at the softswitch level. PPI is more relevant for user-agent-to-proxy communication, while PAI is for proxy-to-proxy communication. However, some vendors may require specific PPI configuration, so understanding this option is important.

VOS3000 P-Asserted-Identity Caller Dial Plan

The “Caller dial plan” setting associated with the PAI configuration allows you to transform the caller number before it is inserted into the PAI header. This is essential when your vendor requires a specific number format in the PAI header that differs from how numbers are stored in VOS3000.

Common Caller Number Transformation Scenarios

Different vendors expect different number formats in the PAI header. Here are the most common scenarios that require caller dial plan configuration:

• Country code addition: Your internal numbers may not include the country code, but the vendor requires it. A dial plan can prepend the country code (e.g., +880) to the caller number in the PAI header
• Leading zero removal: Some vendors require numbers without leading zeros. A dial plan can strip leading zeros from the caller number
• Number format conversion: Converting between E.164 format and national format as required by the vendor
• Prefix addition: Adding a specific prefix that the vendor uses to identify your traffic

🔄 Transformation	📝 Original Number	✅ PAI Number	🎯 Reason
Add country code	01712345678	+8801712345678	Vendor requires E.164
Remove leading zero	01712345678	1712345678	Vendor rejects leading 0
Add + prefix	8801712345678	+8801712345678	E.164 with plus sign
Add tech prefix	1712345678	991712345678	Vendor routing prefix

Advanced VOS3000 P-Asserted-Identity Features

Beyond the basic PAI, Privacy, and PPI settings, VOS3000 provides several advanced features that give you more control over caller identity handling.

Allow All Extra Header Fields

The “Allow all extra header fields” option (VOS3000 Manual, Page 43) enables SIP header transparency, allowing all additional header domains from the incoming SIP message to pass through to the routing gateway. When enabled, any custom or non-standard SIP headers received from the mapping gateway are forwarded unchanged. This is useful when your upstream provider sends proprietary headers that your downstream vendor expects to receive.

Allow Specified Extra Header Fields

For more granular control, the “Allow specified extra header fields” option lets you define exactly which additional header fields should be forwarded. This provides better security than allowing all headers because you can restrict passthrough to only the headers your vendor requires. Add specific header field names to the list, and only those headers will be forwarded from the incoming SIP message to the outgoing message.

Peer Number Information

The “Peer number information” setting controls which field VOS3000 uses to extract the caller number from incoming SIP signals. Available options include extracting from the From header, Display field, or Remote-Party-ID header. This setting determines the source of the caller number that may be used in the PAI header when set to “Caller” mode.

Caller Number Pool for PAI

When you need to substitute the caller ID with numbers from a pool rather than using the actual caller number, VOS3000 provides the “Enable caller number pool” feature in the routing gateway additional settings (VOS3000 Manual Section 2.5.1.1, Page 51). This feature replaces the original caller number with a number from a configured pool, which then appears in both the From header and PAI header. The number sequence can be random (0) or poll (1), configured by the FORWARD_SIGNAL_REWRITE_SEQUENCE setting in softswitch.conf. The “Multiplexes” field controls how many times each pool number can be reused concurrently.

🔧 Feature	🎯 Purpose	📍 Location
Allow all extra headers	Transparent SIP header forwarding	Gateway > Protocol > SIP
Allow specified headers	Selective header forwarding	Gateway > Protocol > SIP
Peer number information	Select caller number source field	Gateway > Protocol > SIP
Caller number pool	Substitute caller ID with pool numbers	Gateway > Additional Settings
Caller dial plan	Transform number in PAI header	Gateway > Protocol > SIP

Configuring VOS3000 P-Asserted-Identity on Mapping Gateway

The mapping gateway (customer-side) also has caller identity configuration options in the Additional Settings > Protocol > SIP section (VOS3000 Manual Section 2.5.1.2, Page 57). The mapping gateway settings control how VOS3000 handles caller identity from your customers’ devices.

Mapping Gateway Caller Settings

On the mapping gateway, the key caller identity settings include:

• Caller: Determines which field of the SIP signal to extract the caller number from. Options include “From” (from the From header), “Remote-Party-ID” (from the RPID header), and “Display” (from the Display field)
• Support Privacy: Enables passthrough of the mapping gateway’s privacy domain settings
• Recognize call forward signal: Identifies forwarding-formatted calls for proper handling

The mapping gateway’s caller extraction method determines the initial caller number that VOS3000 uses internally. This number then flows to the routing gateway where the PAI configuration determines how it is presented to the vendor. If the mapping gateway extracts the wrong caller number, the PAI header on the routing gateway will also be wrong.

Troubleshooting VOS3000 P-Asserted-Identity Issues

PAI configuration problems can be difficult to diagnose because the SIP headers are not visible in the VOS3000 client interface. Here are the most common issues and how to resolve them.

Issue 1: Vendor Rejects Calls Due to Missing PAI

If your vendor requires the PAI header but you have it set to “None” on the routing gateway, calls will be rejected. The fix is straightforward: change the PAI setting to “Caller” so VOS3000 generates the PAI header with the caller’s number. Some vendors may also require the number in a specific format, which you can achieve with the Caller dial plan setting.

Issue 2: Wrong Number in PAI Header

If the PAI header contains an incorrect number, check the chain of caller number extraction. Start with the mapping gateway’s Caller setting to verify the correct source field is being used. Then check if any dial plans on the mapping gateway are transforming the number before it reaches the routing gateway. Finally, verify the Caller dial plan on the routing gateway’s PAI configuration is applying the correct transformation.

Issue 3: Caller ID Displayed When Privacy Is Requested

If a caller requests privacy but their number is still displayed to the called party, check that the Privacy setting on the routing gateway is not set to “None”. It should be “Passthrough” to honor the caller’s privacy request, or “Id” to always add the privacy header. Also verify that the mapping gateway’s “Support Privacy” option is enabled so that privacy requests from the caller’s device are forwarded.

⚠️ Problem	🔍 Likely Cause	✅ Solution
Vendor rejects calls	PAI set to None	Change PAI to Caller
Wrong number in PAI	Dial plan misconfiguration	Check caller extraction and dial plans
Privacy not honored	Privacy set to None	Set Privacy to Passthrough or Id
PAI missing country code	No caller dial plan	Add dial plan to prepend country code
Custom headers lost	Extra headers not allowed	Enable allow all/specified extra headers

Best Practices for VOS3000 P-Asserted-Identity Configuration

Following these best practices ensures your VOS3000 P-Asserted-Identity configuration works correctly and complies with industry standards.

PAI Configuration by Vendor Type

🏢 Vendor Type	⚙️ PAI Setting	🔒 Privacy	📝 Notes
Standard SIP trunk	Caller	Passthrough	Most common configuration
Legacy H323 gateway	None	None	H323 does not use PAI
Emergency services	Caller	None	Must always show caller ID
Privacy-required route	Caller	Id	Always hide caller ID display

Testing PAI Configuration

After configuring VOS3000 P-Asserted-Identity, test with actual calls to verify the headers are being set correctly. Use a SIP phone or softphone to place a test call and examine the SIP messages at the vendor’s side. Verify that the PAI header contains the correct number in the expected format, and that the Privacy header is present when required. For detailed call testing instructions, see our VOS3000 call test and troubleshooting guide.

🔗 Related Resources – VOS3000 P-Asserted-Identity

• 📖 VOS3000 Prefix Conversion and Callee Rewrite Rules
• 📖 VOS3000 Prefix Settings: Rate, Area, Client and Vendor
• 📖 VOS3000 Extended Firewall Configuration Guide
• 📖 How to Stop Illegal Calls in VOS3000
• 📖 VOS3000 Troubleshooting and Support Guide
• 📥 VOS3000 Downloads – Manual and Software

Frequently Asked Questions About VOS3000 P-Asserted-Identity

❓ What is the difference between PAI and P-Preferred-Identity in VOS3000?

P-Asserted-Identity (PAI) is used by network servers (like VOS3000) to assert the identity of the calling party to other trusted network elements. P-Preferred-Identity (PPI) is used by user agents (like SIP phones) to indicate their preferred identity to the network. In VOS3000, PAI is the primary header for caller ID presentation to vendors, while PPI is rarely needed and is typically set to “None” in most deployments.

❓ Should I set PAI to “Passthrough” or “Caller”?

Use “Caller” in most cases because it ensures VOS3000 generates the PAI header from the verified caller number in its database. Use “Passthrough” only when you fully trust the upstream device to provide accurate PAI values and you want to preserve them unchanged. The risk with “Passthrough” is that incorrect or spoofed PAI values from the upstream could be forwarded to your vendor.

❓ Why does my vendor require a specific number format in the PAI header?

Vendors use the PAI header for billing, routing, and regulatory compliance. They need the number in a consistent format (usually E.164 with country code and plus sign) to correctly identify the calling party and apply the appropriate rates. Use the Caller dial plan on the routing gateway to transform the number into the format your vendor requires.

❓ How do I hide caller ID using VOS3000 P-Asserted-Identity?

Set the Privacy option to “Id” on the routing gateway to add a Privacy: id header to all outgoing calls. This signals to the called party’s network that the caller’s identity should be hidden from display. Note that the PAI header is still included (for billing and emergency purposes), but the called party’s device should not show the caller ID to the end user.

❓ Can I set different PAI configurations for different vendors?

Yes, each routing gateway in VOS3000 has its own independent PAI configuration. This means you can configure one vendor with PAI set to “Caller” and a specific dial plan, while another vendor uses “Passthrough” or “None”. This flexibility is essential when working with multiple vendors that have different caller ID requirements.

❓ Where can I get professional help with VOS3000 PAI configuration?

Our VOS3000 specialists can configure PAI headers, dial plans, and privacy settings for your specific vendor requirements. Contact us on WhatsApp at +8801911119966 for expert assistance with your VOS3000 caller ID configuration.

Configure Your VOS3000 Caller ID with Expert Help

Proper VOS3000 P-Asserted-Identity configuration ensures that your calls are accepted by vendors, comply with regulations, and present the correct caller ID to end users. The configuration options are powerful but require careful setup to work correctly across all your vendor relationships.

📱 Contact us on WhatsApp: +8801911119966

Our team provides complete VOS3000 caller ID configuration services, from PAI header setup to dial plan optimization and privacy configuration. We can help you ensure that your caller ID is correctly presented to every vendor in your routing infrastructure.

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