Smart solutions to VoIP questions
How does SIP Registration work and why is it needed? Registration – what it is and why it is necessary IP Phones (and SIP clients in general) need to register with a central server mainly because this allows the phone’s location to be known when it is required to receive an incoming call. The “location” … Read more
What are SIP Servers and why are there so many? SIP and SIP Servers – a brief explanation SIP is a general purpose Session Initiation Protocol that can be used as the basis for a range of services that extend beyond VoIP to video, Presence and beyond. It is a powerful and highly versatile protocol … Read more
Overview What’s the disaster we are trying to avoid? The assumed scenario is this: Some kind of centralised VoIP service is being offered to a number of users; the service operates on servers located at a data centre or office and the users each have a SIP client device, such as an IP phone, that … Read more
The SIP SUBSCRIBE/NOTIFY mechanism – what it is and how it works The SIP protocol includes a standardised mechanism to allow any SIP client (an IP phone being an example of a SIP client) to monitor the state of another device. Details are provided in the SIP protocol document RFC 3265. Basically, it works like … Read more
VoIP Service Providers – the core services on offer Business and home users all have to choose from roughly the same pool of companies providing VoIP services, but the things that they are looking for may not completely overlap. Let’s consider a few of the more important services provided. Cheap calls Why use VoIP? Answer … Read more
How can you make calls for free with VoIP? The cost of a telephone call Just in case you are wondering, you can’t buy a VoIP phone, plug it in, set it up and start calling any number you like for free. It is not that simple – in fact, when you start looking into … Read more