# Is the PortSIP PBX built on Asterisk, FreeSwitch? No. **PortSIP PBX is not based on any open source PBX project**. It is a **commercial PBX platform fully developed by the PortSIP engineering team**. At the protocol layer, PortSIP PBX is built on [reSIProcate](https://github.com/resiprocate/resiprocate), a mature and widely adopted open-source SIP stack written in C++. reSIProcate provides robust implementations of **SIP, ICE, TURN**, and related real-time communication protocols. Many well-known technology companies—including **Cisco**, **Poly**, **Dialogic**, and **Logic,** have built commercial products using [reSIProcate ](https://github.com/resiprocate/resiprocate)as a foundational SIP signaling layer. *** ### Why This Architecture Matters Because PortSIP PBX is **designed and implemented entirely in-house**, rather than derived from an open source PBX framework, we are not constrained by legacy architectures or design limitations common in community-driven PBX projects. This approach allows PortSIP to: * **Rapidly innovate** with modern Unified Communications and Contact Center features * **Optimize performance at scale**, from SIP signaling to media handling * **Design true multi-tenant and cloud-native capabilities** without architectural compromises * **Deliver faster, more effective technical support**, backed directly by the engineers who built the system *** ### Trusted by Customers This level of architectural control and engineering ownership is a key reason why customers and service providers trust PortSIP PBX for mission-critical, large-scale cloud PBX, UCaaS, CPaaS, and CCaaS deployments. PortSIP combines the proven reliability of an industry-standard SIP stack with the flexibility, performance, and innovation of a **modern, fully proprietary PBX platform**. --- # Agent Instructions: Querying This Documentation If you need additional information that is not directly available in this page, you can query the documentation dynamically by asking a question. Perform an HTTP GET request on the current page URL with the `ask` query parameter: ``` GET https://support.portsip.com/portsip-communications-solution/faq/is-the-portsip-pbx-built-on-asterisk-freeswitch.md?ask= ``` The question should be specific, self-contained, and written in natural language. The response will contain a direct answer to the question and relevant excerpts and sources from the documentation. Use this mechanism when the answer is not explicitly present in the current page, you need clarification or additional context, or you want to retrieve related documentation sections.