SIP Outbound Proxy Server Explained

Why do IP Phones require a setting for ‘Outbound Proxy Server’? Outbound Proxy Server When you look at the configuration options on most IP phones, you will see a field called “Outbound Proxy” or “Outbound Proxy Server”. In this field you can enter an IP address, a host.domain name or just a domain name (as … Read more


IP Phone Configuration: SIP Proxy Server

What is the ‘SIP Proxy Server’ setting on an IP phone? It might be called something different on your IP phone In their wisdom, each manufacturer has made different decisions about the naming of data parameters on their IP phones. So if you look at a Snom phone it uses different names to those on … Read more


SIP Registration Explained

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


SIP Servers Explained

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


Caller ID in SIP and Asterisk – Part 1

Caller ID, ANI, PAI, RPI, Privacy – can Asterisk cope? Equipment receiving calls, whether a humble handset or a sophisticated Call centre ACD system, likes to know the identity of the caller. It may simply display the caller’s number on an LCD display, look it up in a directory so the caller’s name can be … Read more


Taking the plunge with SIP Trunks – Part 3

Outbound calls; Matching a DDI/DID; Diagnosing problems; Internet bandwidth. Configuration for Outbound calling Part 2 looked only at the configuration for receiving inbound calls, but the SIP Trunk configuration form in Trixbox/FreePBX has to also include the settings for making outbound calls. It may not even work at all if you only use the inbound … Read more


Taking the plunge with SIP Trunks – Part 2

Recap In part 1, I explained how a SIP Trunk is really just a virtual connection between your Asterisk PBX and the VoIP service provider. Standard SIP signalling is used on the trunk, but more than one simultaneous call is allowed and you may have more than one DDI number. Basic requirements to enable your … Read more