Siperb's Go-Based Media Bridge Lets WebRTC Softphones Work With an On-Premises PBX

Siperb, a WebRTC-to-SIP softphone platform, has detailed a locally-run media bridge that allows its desktop client to connect to a customer's on-premises PBX without exposing that PBX to the public internet or routing calls through cloud infrastructure. The feature was described by founder Conrad De Wet at the OpenSIPS Summit in Bucharest.

The problem the bridge solves is a familiar one for vendors of cloud-based real-time communications software: some customers run their PBX entirely inside their own network and have no intention of connecting it to the internet. Rather than asking these customers to migrate, Siperb built a component that runs inside its desktop client itself.

Written in the Go programming language, the bridge terminates the WebRTC connection locally, on the user's own machine. From the perspective of the browser engine, it behaves like a normal WebRTC endpoint. From the perspective of the customer's PBX, it behaves like a normal SIP endpoint carrying plain, unencrypted media. In between the two, the bridge performs the work that would usually happen on cloud infrastructure: it terminates the WebSocket connection, proxies call signalling to the upstream SIP server, and handles media by altering the session description (SDP), inserting itself as the media server, removing the DTLS encryption applied by the browser, and forwarding plain media in whichever codec the upstream PBX expects, whether PCMA, PCMU or Opus.

The architecture avoids a common alternative: shipping a dedicated on-premises appliance, such as a session border controller or RTP relay, into the customer's building. That approach works but adds hardware and an ongoing maintenance burden to a deployment that was intended to be software-only. By performing termination inside the client instead, Siperb's customers can keep a pure software deployment model: the softphone application itself is capable of acting as a media-aware SBC only when the situation calls for it, with no additional box required.

Siperb also disclosed that the bridge's first working version was produced in around two days of collaborative development between its engineering team and an AI coding assistant, using a detailed specification modelled on established RTP proxy design. The team describes an ongoing feedback loop in which runtime logs are fed back to the assistant for analysis and fixes.

Siperb's founder argues that the wider industry assumption - that any system not already in the cloud is a migration problem waiting to be solved - is likely to prove wrong for a meaningful segment of customers. Organisations that intend to keep their PBX on their own premises indefinitely are, in his view, better served by vendors who design for that reality directly.

Full technical documentation on Siperb's local media bridge and on-premises SIP integration approach is available at siperb.com.

Siperb Ltd
2nd Floor College House
17 King Edwards Road
Ruislip, London
United Kingdom, HA4 7AE

Press Contact: Justin Downes, Mothercitymedia
Email: justin@mothercitymedia.com
Phone: 0784704675

Siperb is a WebRTC-to-SIP softphone platform connecting browser, desktop and mobile clients to existing PBX infrastructure, including Asterisk, FreeSWITCH and OpenSIPS deployments, through a dual-registration architecture that keeps SIP credentials off the client device. Founded to give businesses a browser-based softphone that works with the phone systems they already run, Siperb is UK-registered and serves customers migrating from legacy desk-phone setups as well as those keeping their PBX entirely on-premises.

This release was published on openPR.