Peer-to-Peer Blog: Erlangs Really?

By David Byrd

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 an SIP Trunk. With the Broadvox service an 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 a.m. and 2 p.m. 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:

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

David Byrd is vice president of marketing and sales for

Broadvox

, and is responsible for marketing and channel sales programs to SMBs, enterprises and carriers as well as defining the product offering. Prior to joining Broadvox, David was the Vice President of Channels and Alliances for Eftia and Telcordia. As Director of eBusiness Development with i2 Technologies, he developed major partnerships with many of the leaders in Internet eCommerce and supply chain management. As CEO of Planet Hollywood Online he was a pioneer in using early internet technologies to build a branded entertainment and eCommerce website company partnered with Planet Hollywood. Having over twenty years of Telecom sales and marketing experience, he has held executive positions with Hewlett-Packard, Sprint and Ericsson.