Monthly Archives: September 2013

Understanding Session Description Protocol (SDP)

It’s impossible to truly understand SIP without understanding its cousin, Session Description Protocol (SDP).  While SIP deals with establishing, modifying, and tearing down sessions, SDP is solely concerned with the media within those sessions.  That SIP would relegate media to another protocol is not accidental.  The creators of SIP set out to make it media […]

DTMF and RFC 2833 / 4733

Over the past couple of weeks I’ve written two installments on voice codecs (A Cornucopia of Codecs and Codecs Continued).   I mentioned some of the major characteristics of six different codecs and why you might choose one over another. However, I failed to point out something that is of great importance when making your codec […]

Codecs Continued

Last week I wrote about G.711, G.729, G.726, and G.722 in A Cornucopia of Codecs.  Many of my readers know that there are more codes to choose from.  All codecs exist for a reason, but some are clearly more popular, and frankly, useful than others.   Although you will typically encounter the four that I’ve already […]

Let’s Play (SIP) Tag

For those of you who have been waiting for me to write one of my deep-in-the-weeds blogs about some esoteric aspect of SIP, the wait is over.   As for the rest of you, now might be a good time to peruse through my previous blogs where I tackle less geeky subjects.  However, you won’t know […]

Next Generation 9-1-1

We all have a fundamental understanding as to what happens when we pick up a telephone and dial 911.  We expect that our call will be answered by an emergency response specialist close by and not by someone hundreds of miles away. However, have you ever thought about how that happens?  Have you thought about […]

A Cornucopia of Codecs

Over the past few months I’ve written a lot about the signaling aspects of IP communications and although I’ve mentioned media as the result of a SIP session, I haven’t really gone into much detail about the different types of media. Well, today I plan on rectifying that and spending some time on audio as […]

Microsoft Lync and Session Border Controllers

As with every other SIP solution for voice communications, there is a place for session border controllers (SBC) in a Microsoft Lync configuration. However, leave it to Microsoft to make their solution different enough that it warrants some discussion. SIP Trunks Let’s start with SIP trunks. As you probably already know, an SBC will sit […]

The Microsoft Lync Survivable Branch Office

Back in the dark ages of telephony (before the year 2000) it could be said that if you had a building you had a PBX.   It didn’t matter if that other building was across the street or across the country.  The wiring of an older PBX had distance limitations and although there were some tricks […]

A Quick Introduction to Microsoft Lync

My history with Microsoft telephony goes back to the early 1990’s when Microsoft and Intel jointly created and released the Telephony Services Applications Programming Interface or TAPI.  TAPI allowed Windows programs to write applications that could directly control a telephone.  A TAPI application could instruct a telephone to do anything that a user of that […]

Adding Mobile SIP Technology to Your Communications System

Last week I presented a webinar on adding mobile SIP devices to your communications network.   I give webinars on a fairly regular basis and will admit that some topics require more research than others.  However, this one was a bit of a no-brainer for me since I’ve been using mobile SIP technology for many years […]