The VoIP Users Conference is a weekly live discussion about VoIP, SIP, Asterisk and all kinds of telephony-related topics. The conference has been running weekly since March 2007. OnSIP CTO John Riordan was recently featured on the program to discuss OnSIP’s Busy Lamp Field.
For the past several decades, office receptionists and call center managers have relied on phone sidecars and flashing buttons to get a bird’s eye view of which their co-workers were on a call. Busy Lamp Field, the phone’s flashing lights, appear to be straightforward and common sense. However, recreating this feature for the modern work environment is not so easy, especially since businesses increasingly need geographic flexibility, the ability to connect multiple offices, remote workers, and traveling employees with smart phones.
On the program, John discusses the various solutions OnSIP implemented to architect BLF. He outlines the intricacies of RFC 4235, the protocol that allows phones to support BLF. RFC 4235 allows for full or partial state updates, depending on the phone. Some phone manufacturers require a full list of how many calls a given user is on, whereas others require a specific number (perhaps the first or last.) Once each phone's state update was identified, OnSIP's engineers were able keep track of which phones were on calls by using the publish/subscribe feature that is built into RFC 4235.
In addition to BLF, John also discusses other OnSIP interests, such as video calls, TCP/WebSocket implementation, WebRTC, and encrypted calls.