Implementing SIP Header Manipulation Rules for Carrier-Specific ANI and DNIS Translation

How-To-Articles
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Implementing SIP Header Manipulation Rules for Carrier-Specific ANI and DNIS Translation

What This Guide Covers

This guide details the architectural implementation of SIP header manipulation rules within Genesys Cloud CX to enforce strict ANI (Automatic Number Identification) and DNIS (Dialed Number Identification Service) translation logic for specific carrier interconnections. You will configure outbound translation patterns to sanitize caller IDs for compliance and inbound normalization rules to ensure downstream applications receive consistent, normalized numbers regardless of the originating carrier format.

Prerequisites, Roles & Licensing

  • Licensing: Genesys Cloud CX 3 license with Genesys Cloud Voice or Genesys Cloud Contact Center capabilities. Access to Telephony > Trunk > Edit is required.
  • Permissions:
    • Telephony > Trunk > Edit
    • Telephony > Trunk > View
    • Routing > Queue > Edit (if mapping to specific queues based on translated DNIS)
  • Technical Dependencies:
    • A configured SIP Trunk (SBC or Genesys Cloud Voice) with an active IP peer relationship.
    • Root access to the Session Border Controller (SBC) if pushing translation upstream (recommended for high-volume carriers).
    • Understanding of E.164 formatting standards (RFC 3966).

The Implementation Deep-Dive

1. Architectural Strategy: Inbound vs. Outbound Translation

Before configuring the specific rules, you must determine where the translation occurs. There are two primary architectural patterns for ANI/DNIS manipulation:

  1. Edge Translation (SBC Level): The SBC strips or adds headers before the SIP INVITE reaches Genesys Cloud.
  2. Platform Translation (Genesys Cloud Level): Genesys Cloud receives the raw headers and applies transformation rules via the SIP Header Manipulation feature set within the Trunk configuration.

The Trap: Relying solely on Genesys Cloud for heavy ANI normalization on high-volume carriers (100+ concurrent calls). Genesys Cloud processes SIP headers asynchronously relative to the media path setup. If the translation logic is complex or the header payload is malformed, it can introduce latency in the SIP handshake, leading to increased call setup times or occasional 503 Service Unavailable errors during peak load.

Recommendation: Use Genesys Cloud SIP Header Manipulation for Outbound ANI Sanitization (where consistency is critical for carrier acceptance) and for Inbound DNIS Normalization for low-to-medium volume trunks. For high-volume inbound trunks with erratic carrier formatting, enforce normalization at the SBC level and pass clean E.164 data to Genesys Cloud. This guide focuses on the Genesys Cloud platform configuration, which is the most common requirement for mid-market deployments and hybrid environments.

2. Configuring Outbound ANI Sanitization Rules

Carriers often reject calls if the P-Asserted-Identity (PAI) or From header contains non-E.164 formats, such as local 10-digit numbers, vanity numbers, or numbers with extensions appended. You must configure a translation rule to ensure the ANI is strictly E.164 (e.g., +14155551234) before the INVITE leaves the Genesys Cloud edge.

Step 2.1: Accessing the Trunk Configuration

  1. Navigate to Admin > Telephony > Trunks.
  2. Select the target SIP Trunk.
  3. Click on the SIP Header Manipulation tab.
  4. Select Outbound Rules.

Step 2.2: Defining the ANI Translation Rule

You will create a rule that intercepts the P-Asserted-Identity header. Note that while some legacy carriers rely on the From header, modern SIP standards prioritize P-Asserted-Identity for the caller ID presented to the recipient. You should manipulate both to ensure maximum compatibility, but PAI is the primary vector for fraud prevention systems.

Configuration Parameters:

  • Rule Name: Sanitize_Outbound_ANI_To_E164
  • Header Name: P-Asserted-Identity
  • Match Condition: Contains → not → + (This targets any number that does not already start with a plus sign).
  • Action: Replace
  • Replacement Value: +1[Original Header Value] (Assuming US/Canada. Adjust prefix for other regions).

Advanced Scenario: Vanity Number Removal

If your outbound calls include vanity numbers (e.g., 1-800-FLOWERS), carriers will reject these. You must use a Regular Expression (Regex) match to strip alphabetic characters.

  • Header Name: P-Asserted-Identity
  • Match Condition: Regex
  • Regex Pattern: ^[^+].*$ (Matches any string not starting with +)
  • Action: Replace
  • Replacement Value: Use a static override or a complex Regex substitution if your SBC supports it. However, Genesys Cloud’s native header manipulation is limited to simple string replacement.

The Trap: Overwriting the From header without updating the P-Asserted-Identity header. Many fraud detection systems (like STIR/SHAKEN validators) cross-reference these headers. If they mismatch, the call may be labeled “SPAM Likely” or blocked entirely. Always ensure both headers are synchronized in your outbound rule set.

Step 2.3: Applying the Rule to Specific Traffic

Not all outbound traffic requires the same translation. You can scope the rule using Call Context filters if available in your Genesys Cloud version, or by creating separate Trunks for different traffic types.

  • Filter: If using Genesys Cloud Voice, you can filter by Region.
  • Filter: If using a custom SBC trunk, you can filter by IP Peer.

Create separate rules for domestic vs. international traffic, as international ANI requirements vary significantly by country (e.g., some countries require the national significant number without the country code for local presentation).

3. Configuring Inbound DNIS Normalization

Inbound calls often arrive with DNIS in various formats: E.164 (+14155551234), National Format (14155551234), or with extensions (4155551234x101). Genesys Cloud uses the DNIS to route calls to the correct IVR or Queue. Inconsistent DNIS formats will cause routing failures.

Step 3.1: Accessing Inbound Header Rules

  1. Navigate to Admin > Telephony > Trunks.
  2. Select the target SIP Trunk.
  3. Click on the SIP Header Manipulation tab.
  4. Select Inbound Rules.

Step 3.2: Defining the DNIS Normalization Rule

The goal is to convert all incoming DNIS into a consistent E.164 format before the call enters the Architect flow.

Configuration Parameters:

  • Rule Name: Normalize_Inbound_DNIS_To_E164
  • Header Name: Request-URI (The Request-URI contains the called party number in the INVITE method line, e.g., INVITE sip:+14155551234@sbc.example.com SIP/2.0).
    • Note: While To header is also present, the Request-URI is the authoritative source for the called number in SIP. Manipulating the To header alone does not change the routing key used by Genesys Cloud’s initial call admission logic.
  • Match Condition: Regex
  • Regex Pattern: sip:([^@]+)@
    • This captures the number portion between sip: and @.
  • Action: Replace
  • Replacement Value: sip:+1$1@
    • This prepends +1 to the captured group.

Refining the Regex for Complex Scenarios:

If your carrier sends numbers with leading 1s or without country codes, you need a more robust regex.

  • Regex Pattern: sip:(1?)([0-9]{10})@
    • Group 1: Optional leading 1.
    • Group 2: 10-digit number.
  • Replacement Value: sip:+1$2@
    • This discards the optional leading 1 and ensures the +1 country code is present.

The Trap: Manipulating the To header instead of the Request-URI. Genesys Cloud’s IVR engine uses the DNIS derived from the Request-URI for initial routing decisions. If you only change the To header, the IVR will still see the original, unnormalized number, leading to routing mismatches. Always prioritize Request-URI manipulation for DNIS.

4. Handling P-Asserted-Identity vs. From Header Discrepancies

Some legacy carriers send the ANI in the From header but leave P-Asserted-Identity empty or mismatched. Genesys Cloud prioritizes P-Asserted-Identity for displaying the caller ID to the agent. If PAI is missing, it falls back to From.

Configuration Strategy:

  1. Create an Inbound Rule for P-Asserted-Identity.
  2. Match Condition: Is Empty
  3. Action: Copy From Header
  4. Source Header: From

This rule ensures that if the carrier fails to provide PAI, Genesys Cloud copies the value from the From header into PAI, ensuring the agent sees the correct caller ID.

The Trap: Copying a malformed From header into PAI. If the From header contains a display name (e.g., "John Doe" <sip:14155551234@carrier.com>), copying the entire string into PAI will break SIP parsing. You must use a Regex to extract only the URI portion.

  • Regex Pattern: <sip:(.+?)>
  • Replacement Value: sip:$1

Validation, Edge Cases & Troubleshooting

Edge Case 1: The “Double Plus” ANI Error

The Failure Condition:
Outbound calls fail with 403 Forbidden or 483 Too Many Hops from the carrier. The carrier logs show the ANI as ++14155551234.

The Root Cause:
Your translation rule prepends +1 to numbers that do not start with +. However, some softphones or UC clients (like Microsoft Teams or Zoom Phone) may already send the number in E.164 format (+14155551234). If your rule logic is flawed (e.g., checking for 1 instead of +), it may add another + or 1.

The Solution:
Refine the Match Condition in your Outbound ANI Rule.

  • Current Rule: Contains → not → 1 (Incorrect)
  • Correct Rule: Regex → ^[^+].*$ (Matches any string not starting with +)
  • Ensure the replacement value does not duplicate the country code if it is already present. Use a conditional rule if possible, or ensure the source data is consistently non-E.164 before hitting the trunk.

Edge Case 2: DNIS Routing Mismatch in Architect

The Failure Condition:
Calls arrive in Genesys Cloud, but the IVR flow fails to route them to the correct queue. The Architect flow uses a Set Interaction Variable action to check if DNIS == "+14155551234". The call drops or goes to default.

The Root Cause:
The SIP Header Manipulation rule failed to execute, or the regex did not capture the DNIS correctly due to additional parameters in the Request-URI (e.g., sip:+14155551234;user=phone@sbc.example.com). The semicolon and parameters break simple regex captures.

The Solution:
Update the Regex pattern to ignore parameters.

  • Regex Pattern: sip:(\+?[0-9]+);.*@
  • Replacement Value: sip:+1$1@
  • Verify the rule is applied by checking the Call Detail Records (CDR). In the CDR, look at the Called Party field. If it still shows the raw carrier format, the rule did not apply. Check the SIP Header Manipulation logs in the Genesys Cloud Admin console for error messages indicating regex syntax errors.

Edge Case 3: STIR/SHAKEN Signature Mismatch

The Failure Condition:
Calls are delivered but labeled “SPAM Likely” on the recipient’s device.

The Root Cause:
You modified the ANI in Genesys Cloud, but the STIR/SHAKEN signature was generated by the carrier based on the original ANI. Genesys Cloud’s header manipulation changes the SIP header after the signature verification (if performed at the SBC) or creates a mismatch between the signed identity and the presented identity.

The Solution:
STIR/SHAKEN signing must occur after the final ANI is determined.

  1. Preferred: Perform ANI normalization at the SBC level, then sign the call. Pass the signed INVITE to Genesys Cloud. Genesys Cloud should not modify the ANI for outbound calls that are already signed.
  2. Alternative: If Genesys Cloud must modify the ANI, ensure the SBC re-signs the call after Genesys Cloud processes it. This requires a complex SBC configuration where the SBC strips the signature, allows Genesys Cloud to modify the header, and then the SBC re-applies the signature. This is rarely feasible in real-time.
  3. Best Practice: Do not modify ANI for outbound calls that are subject to STIR/SHAKEN signing within Genesys Cloud. Instead, ensure the upstream application (CRM, Dialer) sends the correct E.164 ANI to begin with. Use Genesys Cloud header manipulation only for inbound normalization or for outbound calls to carriers that do not require STIR/SHAKEN.

Official References