5 Common SIP Trunking Pitfalls and How to Avoid Them

By Brian Ferguson

SIP Trunking pitfalls

SIP Trunking has changed the way companies pay for phone service.  Today, over 66% of companies have adopted SIP Trunking and are saving up to 70% off their monthly phone bill compared to their old PRI service.  SIP Trunking is full of cost savings and calling features, but is also not without its hurdles. Let’s take a look at some pitfalls of SIP Trunking and the solutions that will help your company make a smooth transition.


The Pitfall:  Inadequate Bandwidth. SIP Trunking is completely dependent upon your company’s existing data connection.  The bandwidth available in that connection is what makes the calls happen.  Not having enough bandwidth to support the maximum concurrent calls made by your organization will result in dropped calls, busy signals, bad call quality, and, ultimately, lost customers.

The Solution: The solution to the inadequate bandwidth problem is simple: get an Internet connection with more bandwidth.  In most places, bandwidth is readily available and reasonably cheap.  In order to make sure you have enough bandwidth to support the added load of your voice calls, use this simple formula:

Number of max concurrent calls x 100kb/sec (average bandwidth per call)

This will give you the total bandwidth needed for your voice calls.  Just add this to what you currently use to run your business to get your total bandwidth needed.

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The Pitfall: Not Understanding the Reality of Your Call Volume. Many SIP Trunking providers price their services by the minute.   This pricing model is advantageous to companies with low call volume or dynamic call flows from seasonality or other sporadic events.  The main benefit is that companies only pay for what they use.  The problem lies with companies who don’t understand the reality of their call volume and end up paying more than they should.

The Solution: Before you transition to SIP Trunking, do a thorough analysis on your company’s calling history.  You’ll need to know how many minutes you use on average and how many concurrent calls you use at your busiest times.  If your call volume is high, choose a SIP provider that offers a Channelized plan that will give you unlimited minutes on a set number of trunks.


The Pitfall:  I Need My Numbers Ported Right Now! Phone numbers or DIDs are very valuable to most companies and an integral component of company branding.  The industry understands this and has made it a requirement for companies to “port” or move your phone numbers to whichever provider you choose.  What they are not required to do is to port them quickly.  As you can imagine, spending time helping you move your business to a competitor is not going to be top on the priority list for your old service provider.  This creates problems for organizations that are ready to save money, but can’t function without their numbers.

The Solution: Most providers will allow you to forward your calls from one number to another.  So, get a new number from your new provider and forward your calls from your main numbers to the new one.  Other than that….wait.  Know you’re probably going to have to wait, and just wait.


The Pitfall:  Faxing Over SIP is Not an Exact Science. For reasons not entirely clear to me, fax machines still exist.  Even with email, electronic signature technology and other options, the fax is hanging around, mostly in the medical community.  Faxing has never been an exact science, even with dedicated analog fax lines, and I think we can all relate to standing at the fax machine, hearing that painful modem noise and then receiving the dreaded Failed Fax notification sheet from the printer.  Now, take that same process off a dedicated line and plop it on your data network and you can imagine what happens.  Faxing over IP has long been a thorn in the side of IT; and a codec that was supposed to solve all the worries of the industry, T.38, has not succeeded…at all.

The Solution: If faxing is necessary and faxing over IP is a must, use a professional to help with setting it up.  There are some tricks and phone system adjustments that can be made to help.  If faxing is vital to your business, bring in some dedicated analog lines purely for fax. They’re cheap and work as well as fax can.


The Pitfall: Voice Not a Priority. It’s very likely that you have a lot happening on your data network.  Between the systems you need to do business, email, collaboration, file sharing, and, yes, some people watching YouTube videos, the traffic on your network is heavy.  Today, without SIP Trunking, if there’s too much going on, you’ll likely see pages load slower, email takes longer to send, and YouTube videos may not buffer correctly.  When you add voice with SIP Trunking and there’s a lot going on, you get dropped calls and poor call quality.  Needless to say, the stakes are higher.

The Solution: For companies moving to SIP Trunking, it’s important to take advantage of a feature found in most business-grade network routers called QoS, or Quality of Service.  QoS is is the traffic cop for your network and allows you to prioritize the traffic coming from key systems.  With QoS, you can ensure that all voice calls will be handled first and with full bandwidth while the slow down happens elsewhere.

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