Erlangs...Really?

David Byrd : Byrd's Eye View
David Byrd
Chief Marketing Officer for ANPI

Erlangs...Really?

Most IT managers find it easy to determine how much bandwidth they need for data and it is not difficult to determine the bandwidth requirement for a SIP Trunk. With the Broadvox service a SIP Trunk should have an allocation of 88KB per Concurrent Call Sessions (CCS). The standard does allow for some variability in this rate depending upon options and even Broadvox engineers will sometimes use 100KB in order to have a bit of leeway. This is referred to in some calculations as the “fudge factor”.

So, as a VAR or IT manager, you do everything right. You have a good monthly average usage number for the data. You have converted the number of phones lines correctly to CCSs and there are no configuration errors in setting up the IP PBX or the SIP Trunk. Yet, during the working day there are still problems with your VoIP call quality. It has to be the service provider, right? No, it may still be a bandwidth issue. The traditional busy hour for business voice traffic uses 10:00 am and 2:00 pm to measure peak requirements. However, with the advent of greater Internet usage, cloud computing, and unified communications these time periods can be easily lengthened or changed. The following variables need to taken into consideration:

  • Is the business a contact center that employs dialers and call holding?
  • What services are end-users allowed to access during the day? YouTube, Hulu, Facebook or any gaming sites?
  • How many computers are active at any point in time?
  • Is video conferencing one of the services in use for the company?
  • What types of applications or tasks are active during the day and are they in use for specific times or random?
  • What is the IT infrastructure architecture (client/server, cloud computing, standalone apps)?
  • Is the network connectivity via a dedicated connection, MPLS or the public internet?

These and other factors can impact the amount of usage at any given point in time. Network monitoring tools will provide better visibility in how the bandwidth is consumed during the day. Then a determination can be made as to whether to adjust the available bandwidth or restrict various types of usage. Other tools such as an Erlangs and VoIP Bandwidth Calculator may also be employed. While somewhat self explanatory, it will require knowledge of Erlangs, CODECs, busy hour, call blocking and, of course, bandwidth.

The good news about VoIP and SIP Trunking is that the technology is proven and becoming mainstream. The flipside is that IT managers and VARs need to become better at determining network usage requirements and making adjustments as required. And remember, when testing for voice quality, try to keep your personal laptop and wireless bandwidth consumption to a minimum.

See you on Monday…

 

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