Recent Posts

Page 4 of 6« First...23456

SIP and NAT: Why is it a problem?

August 23, 2010

Why is it a problem using SIP Clients behind NAT? What is NAT? To understand why SIP Clients behind NAT are a problem, you need to first have some understanding of what NAT is and what it does. NAT stands for Network Address Translation. Unless you are using One-to-one NAT, then a NAT device may […]

Read the full article →

SIP Outbound Proxy Server Explained

August 23, 2010

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 the full article →

IP Phone Configuration: SIP Proxy Server

August 23, 2010

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 the full article →

SIP Registration Explained

August 23, 2010

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 the full article →

SIP Servers Explained

August 23, 2010

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 the full article →

Caller ID in SIP and Asterisk – Part 2

May 28, 2010

Caller ID, ANI, PAI, RPI, Privacy – what Asterisk does I didn’t plan on writing a “Part 2” to this article, but since nobody has posted any answers to my questions in Part 1, I had no option other than to test it for myself. In some ways, the answers are quite simple, but there […]

Read the full article →

Caller ID in SIP and Asterisk – Part 1

April 20, 2010

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 the full article →

Taking the plunge with SIP Trunks – Part 3

December 19, 2009

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 the full article →

Taking the plunge with SIP Trunks – Part 2

November 13, 2009

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 the full article →

Taking the plunge with SIP Trunks – Part 1

November 1, 2009

SIP Trunks are often talked about on the Asterisk wiki and forum pages; Many VoIP service providers offer them as a standard product; But just what is a SIP trunk and what can you use it for and how do you make it work with Asterisk? I will attempt to answer these questions in what […]

Read the full article →