PortSIP Call Parking Feature
What Is the Problem with Traditional Call Parking?
As described earlier, traditional call parking works well in single-tenant PBX deployments. In these environments, call parking is typically implemented by creating dedicated parking extensions (park spots), which users can monitor and retrieve calls from.
However, this model does not scale in modern cloud PBX deployments.
Challenges in a Cloud, Multi-Tenant Environment
Today’s PBX deployments are predominantly cloud-based and multi-tenant, where:
A service provider hosts a single PBX instance
The PBX serves hundreds or thousands of tenants
Each tenant operates a logically isolated virtual PBX, while sharing the same infrastructure
A single cloud PBX instance may support 1,000 to 10,000 tenants.
In a traditional call parking model:
Each tenant must create its own set of parking spots
Parking spots are implemented as PBX extensions
Each parking extension must:
Register to the PBX
Periodically send SIP
REGISTERmessagesBe monitored via Dialog Event subscriptions
Scalability impact
For example:
If each tenant creates 10 parking spots
A PBX with 1,000 tenants requires 10,000 parking extensions
This results in:
Tens of thousands of SIP registrations
Thousands of Dialog Event subscriptions
Significant consumption of CPU, memory, and network bandwidth
As tenants grow and require more parking spots, the impact multiplies further. This approach severely degrades PBX performance and is unacceptable for service providers operating at scale.
PortSIP Solution
PortSIP PBX is designed specifically for cloud PBX and service provider environments. It is a true multi-tenant PBX, where:
A single PBX instance can host thousands of tenants
Each tenant is fully isolated
System resources are used efficiently and predictably
To address the scalability issues of traditional call parking, PortSIP implements call parking in a fundamentally different way.
Key Design Principles
PortSIP’s call parking implementation:
Does not require creating parking spot extensions
Does not require SIP registration for parking spots
Does not require Dialog Event subscriptions
This design eliminates the core scalability bottlenecks found in traditional implementations.
How PortSIP Call Parking Works
Parking a Call
There is no need to create parking spots.
The target extension number itself acts as the parking reference.
To park a call to extension
103, the user simply transfers the call to:
Where:
*68is the Feature Access Code (FAC) for call parking103is the extension number associated with the parked call
Call Park Notification
Once the call is parked:
The target extension device (IP phone or softphone) receives an out-of-dialog SIP NOTIFY
The NOTIFY uses the
park-infoeventThe message includes:
Who parked the call
Where the call is parked
How the call can be retrieved
The device can parse this information and alert the user that a call is parked.
Retrieving the Call
The user retrieves the parked call by pressing the corresponding button or soft key
No polling, subscription, or manual dialing is required
Advantages of the PortSIP Call Parking Design
PortSIP’s approach provides the following benefits:
No parking spot extensions required Eliminates the need to create, register, and maintain thousands of virtual extensions.
No Dialog Event subscriptions Removes subscription overhead and long-lived SIP dialogs.
Rich NOTIFY information Devices receive detailed parking information and can present one-click retrieval to users.
Cloud-scale performance Call parking does not consume excessive CPU, memory, or bandwidth—even in very large deployments.
Service-provider friendly Suitable for large tenants and massive multi-tenant cloud PBX environments without performance degradation.
Summary
Traditional call parking models were designed for on-premise, single-tenant PBXs. PortSIP’s call parking is cloud-native by design, enabling service providers to deliver call parking at scale—without compromising system performance.
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