About this Document
Last updated: 20 March 2026
Fusion for SIP Trunking Module (Admin View – Process & Functionality)
Module Purpose & Portal Architecture
Fusion for SIP Trunking provides an automated trunking lifecycle within the portal. It allows administrators to provision, configure, and maintain SIP trunks for different target environments, including IP PBXs, IADs, Microsoft Teams, and similar destinations. The goal is to centralise trunk configuration, reduce manual SBC operations, and align commercial entitlements with technical service delivery.
Flexible Subscription Configuration
System administrators control the availability of portal subscription configuration using the global Branding page under Settings. From this interface, they can explicitly enable or disable specific operational "subscriptions" for Tenant Administrators inclusive of:
- Addresses
- Numbers
- Subscription Orders
- Trunks Settings: Access details, Allow List, Block List, Call Barring, Call Forwarding, Calling Plan, Capacity, Details, DIDs, SIP Options.
Administrative Entry Points
In addition to standard configuration items for Fusion (Numbers, Addresses and Settings), the SIP Trunking module also includes:
- Trunks – the main operational area for creating and managing trunks
These menu areas work together rather than in isolation. In practice, the administrator first confirms entitlement and inventory, then allocates numbers, and finally configures or updates the SIP trunk itself. To support ongoing maintenance, administrators can access comprehensive Reporting pages for deep-dive license specifications, as well as an Audit page that captures all system changes hierarchically (allowing reseller administrators to review all configuration modifications at or below their assigned organizational tier).
SIP Trunk Provisioning Flow
A stepwise SIP trunk administration flow is typically executed in the following chronological sequence to ensure full regulatory and platform alignment:
- Confirm Tenant Entitlements (Step 1) Confirm that the tenant subscription contains the necessary SIP trunking and number entitlements. Ensure that the ordered products (such as Fusion seats or trunk channel capacities) are correctly applied to the subscription.
- Address & Emergency Compliance (Step 2) Validate address information to satisfy regulatory or emergency-calling compliance requirements. Regulatory Guardrail: Because every active number requires a physical location mapping for emergency dispatch services, administrators must configure these addresses (which can be bulk-created using a standard upload template) prior to trunk assignment.
- Review & Assign Numbers (Step 3) Review available numbers within the platform's number management engine. Assign the relevant DIDs where required.
- Initialize Trunk & Select Type (Step 4) Open the Trunks menu and create the required trunk asset. During creation, administrators must select the appropriate destination environment, differentiating between a standard SIP Trunk (for on-premise PBXs and IADs) and a Peer Trunk (used for direct integrations with cloud ecosystems like WebEx, Zoom, or Azure).
- Verify Synchronisation Status (Step 5) Review the synchronisation status to confirm provisioning alignment with the Session Border Controller (SBC). This gives administrators real-time lifecycle visibility and provisioning confidence before proceeding to behavioral adjustments.
- Configure High-Level Overrides (Step 6) Set the high-level trunk behaviors, such as inbound/outbound operational toggles and global disaster recovery behaviors.
- Configure Detailed Feature Tabs (Step 7) Configure detailed tabs such as capacity, DIDs, calling restrictions, and access trunks to establish fine-grained traffic control.
- Save & Validate Operational State (Step 8) Commit the completed configuration to the database, trigger the final SBC synchronization push, and validate that the active operational state reads as completely successful.
The trunk list view permanently displays the trunk type, current live SBC synchronisation status, and deletion options, providing administrators with continuous operational clarity.
High-Level Trunk Controls
At the top of the trunk configuration view, administrators can typically control overriding behavioral switches:
Disaster Recovery
When enabled, disaster recovery redirects calls to the configured recovery destination, which is defined at the number level using an external Public Switched Telephone Network (PSTN) forwarding number.
⚠️ Absolute Priority Precedence: Once activated at the trunk level, disaster recovery automatically redirects all incoming traffic to the backup target. This action takes absolute precedence over all other localized routing actions such as number rewrites, standard diverts, or user forwarding logic. Administrators should therefore treat disaster recovery as an overriding control and configure it carefully.
Inbound / Outbound Activation
Inbound and outbound calling can be activated or deactivated independently at trunk level, allowing sharp operational control during rollout phases, tenant migrations, troubleshooting exercises, or staged service activation without requiring the deletion of the trunk configuration itself.
Trunk Configuration Tabs
Details & Settings
This tab is used for core trunk identity and presentation settings, including trunk name, billing identifier, and presentation-number formats. The chosen presentation format is saved securely inside the data model and checked actively by the system's core service logic to modify the calling digits on the fly during an active call setup. It also exposes synchronisation visibility with the SBC, allowing the administrator to confirm whether the configured settings have been provisioned successfully into the call-control environment.
Capacity
This tab controls simultaneous call limits. Capacity can be managed at trunk level or subscription level, depending on the service model and operational requirement.
While administrators can place specific limits on individual trunks to distribute channels, they must remember that the subscription-level capacity acts as the overarching framework limit shared across all trunks. Administrators should verify where the effective limit is applied before making capacity changes. If the combined traffic across all associated trunks reaches the subscription's overarching concurrent call limit (CCL), the platform edge will automatically block any subsequent calls.
DIDs
The DIDs tab allows the administrator to assign one or more numbers to a trunk. One DID can be marked as the pilot number. The underlying numbers table clearly defines the specific trunk group or entity assigned to each number. Individual DIDs can have routing-related behaviours such as:
- Rewrite – modify the number format for specific downstream routing purposes.
- Divert – commonly used during live carrier migration windows to keep services reachable while backend configurations are updating.
- Per-DID disaster recovery – redirect calls for that specific number alone to an external PSTN target, allowing administrators to handle isolated routing failures without forcing a full trunk-wide disaster recovery flip.
This gives administrators granular DID-level behaviour without requiring a separate trunk for every scenario.
Call Barring
This tab allows explicit barring of incoming and outgoing calls and is part of the earliest stages of call processing control. It is useful for hard restriction scenarios. Inbound call blocking requests are universally handled within this layer.
Block List and Allow List
These tabs operate as exceptions relative to broader call policy. A Block List can prohibit calls that would otherwise be allowed, while an Allow List can explicitly permit calls that would otherwise be blocked. This enables controlled local exceptions without requiring a full change to group-level policy.
Calling Plan
The Calling Plan classifies call destinations, for example premium numbers, by country and prefix (such as managing geographic routing blocks for specific international regions). Options are defined globally at the Group level by system administrators and then exposed down to individual tenant trunk configurations. Some high-risk or premium destination items may require explicit administrator approval and will appear in the UI with a lock indicator.
Hierarchical Feature Precedence Logic
When a call passes through the SIP trunking module, the platform evaluates rules using a strict top-down hierarchy. More specific trunk-level rules override broader group-level policies. The system processes traffic in the following exact order:
| Evaluation Order | Processing Layer | Operational Behavior |
|---|---|---|
| 1 (Highest) | Call Barring | Evaluated first. Instantly drops blocked inbound or outbound traffic. |
| 2 | Trunk Allow List | Checks for explicit local exceptions that bypass broader group-level rules. |
| 3 | Trunk Block List | Evaluates trunk-specific exceptions to drop traffic otherwise allowed by the group. |
| 4 | Group Block List | Evaluates broader, tenant-wide call blocking rules. |
| 5 (Lowest) | Calling Plan | Evaluates the dial plan prefixes and destination classifications to verify routing eligibility. |
Access Trunks
The Access Trunks tab is used to manage the underlying connection points and routing endpoints associated with a trunk. It is a critical area for resilience, failover, and detailed SBC-related configuration.
Rather than requiring administrators to manually type out network routing paths for every setup, the available **Points of Presence (PoPs) are configured once as a generic global setting for the group by system administrators.
Within the Access Trunk configuration, each individual node endpoint can expose specific properties, including:
- Name, Priority, and Weight (to manage load balancing and resilient failover sequencing)
- Locale
- Private Realm
- Access Device / Point of Presence (PoP selection)
- Inbound / Outbound permissions
- SIP Options
- White list access rules
- Transport type, such as UDP or TLS
This is the area where the bulk of service-provider-specific routing and connectivity characteristics are exposed to administration.