Published: December 3rd, 2015

“The erlang is a unit of traffic density in a telecommunications system. One erlang is the equivalent of one call (including call attempts and holding time) in a specific channel for 3600 seconds in an hour. The 3600 seconds need not be, and generally are not, in a contiguous block.

In digital telecommunications, the voice signals are compressed. This makes it possible for one channel to carry numerous calls simultaneously by means of multiplexing. In theory, there are many ways in which a channel can carry a certain number of erlangs. For example, a traffic density of 3 erlangs can consist of three simultaneous calls, each lasting for an hour (a total of 10,800 seconds); it can consist of six calls, each of which are allocated 30 minutes (1800 seconds) of time during the hour; it might consist of 180 calls, each of which occupy one minute (60 seconds) of time during an hour”.

For some it is obvious to understand Erlang calculations and how they apply to voice and PBX traffic engineering.  There are also some readers who have never used calculations to design technology solutions that they deployed and support in their daily tech support lives.

As a former network design and implementation field engineer, I used ‘Rules of Thumb” based on experience over many years to determine how many segments, switches, routers and circuits were required for the corporate data networks I was responsible for.

Now organizations are looking to deploy unified communications solutions that provide real-time voice, messaging and video desktop capabilities. People expect to use these applications across different device and locations, and have them ‘just work’!.

What disturbs us at FOX GROUP is the lack of consideration, time, attention and resources that are applied to ensure that the overall IP network will be able to support these highly network-dependent real-time based applications.   We see most organizations starting with a small UC pilot to see how people will be able to use the UC features.

Next thing we hear, they have added more and more licenses to their network environment, and yet, they have not made any significant enhancements to add more capacity, performance and network management to ensure reliable communications to occur. They also have not invested in training, documentation and support requirements to ensure that the IT organization will be able to support, troubleshoot and manage these UC applications across all of the devices, applications and systems they run through.

Why don’t people get it?

One of the consistent challenges I have faced in the 30+ years of designing, deploying and supporting enterprise voice, data and video networks is to get the support required to have reliable infrastructures, tools and processes to support the growing number of communication oriented applications.  From working with our clients as a consultant over the past 15+ years, the situation has gotten even worse!

One would have thought that as broadband capacity became more available at lower costs that organizations would finally invest in network/performance management solutions. Unfortunately, this has not been the case (with a few exceptions in some industry segments).

To put things in perspective

What we now have is organizations of all types and sizes that are trying to build a large multi-million dollar mansion, beautifully designed and furnished rooms built on either a pile of molten lava that they don’t know exists that is going to start the house on fire, or the house is built on a bunch of quick sand.

Either way, the basic foundation for the house is not stable, reliable or matched to the quality of the house being built.   In our world of networking, this means that the LAN and WAN (wired and wireless) is not well thought out, planned or installed to support the quality of the devices and people who need to use the environment.

Do not hesitate to contact Roberta Fox to discuss further. As always, I welcome your thoughts, feedback and comments. You can contact me at or 905-473-3369 x 1001.