If you have been involved with telephony within the last decade, you will have heard of Asterisk as an open-source alternative to proprietary traditional and IP PBXs. If you’re considering Asterisk as a solution for your business, this article may be useful, as it will clarify what Asterisk is, how it can be implemented, and what kind of support you will need to ensure its viability as a solution.

If you are a voice network engineer, then it has probably happened to you. Your SIP server is all set up and you have plugged in your IP phone. Its lights come on, its screen is activated, you see the loading icon rotating, and then… nothing. For some reason, the phone will not register.

IP phone registration issues are, unfortunately, not uncommon. In this article, we examine the most common causes of registration failures, and best practices for troubleshooting and resolving them.

Wouldn’t it be great to have superhero X-ray vision that allows you to understand, in a single glance, what is going on with the voice traffic on your network? In fact, it is possible to do so using the Simple Network Management Protocol (SNMP). In this article, we take a look at this protocol and highlight the special features it has up its sleeve to help you with your VoIP monitoring needs.

Part 2 of 2

When it comes to VoIP signaling, SIP is by far the most widely-used protocol. But, there are other protocols, as well, and being familiar with them is helpful when establishing interoperability between systems or deploying specialized installations. In this article, we’ll discuss the H.323 protocol suite and the media gateway control protocol (MGCP), and look at applications for which they are best suited.

VoIP protocols, part 1

When we talk about VoIP, the most prominent and widely used protocol is Session Initiation Protocol (SIP). But SIP doesn’t operate alone. There are many other protocols involved in IP telephony that function alongside SIP or even in the place of it. It is important for a telecom engineer to be familiar with these protocols, to know what they do and how they can be leveraged on the telecommunications network.

In this article, we’ll look at the companion protocols that work in conjunction with SIP. In a future article, we will focus on protocols that can be used as alternatives to SIP.

Demystifying codecs, part 2

Different VoIP codecs digitize sound differently. Knowing which codec to use for a given application will allow you to better optimize your telephony implementations.

In this article, we examine the most commonly used codecs for VoIP, including the the G.711, G.729, G.722, G.726, iLBC and Opus codecs, and identify the situations for which each one is best suited.

Understanding how codecs work

One of the most abstract attributes of Voice over IP (VoIP) is the codec. We may wonder which codec to use in a given situation. Of course, there are general industry guidelines that help us make such decisions, but it can be unnerving to blindly follow recommendations without knowing why. For example, why should G.729 be preferred over the G.711 codec for WAN links? Why should I use G.722 when I don’t have an issue with bandwidth? What are the advantages of iLBC and Opus over the G series of codecs and when should I use them?