SIP Trunking: A Reality Check

By Graham Francis and Robert Reams

SIP trunking is one of the fastest moving and most talked about elements of VoIP in the world of telecommunications, and not without good reason. It offers benefits ranging from low-cost calling, centralization of lines into a business and fast disaster recovery (or failover). Its also a platform for carrying unified communications across boundaries creating a working environment that could never have been dreamed of using older technologies.

However, as manufacturers, service providers and enterprise customers are finding out, SIP trunking is not always an easy service to implement and certainly not an easy one to support if things go wrong.

First, there are still significant issues that arise when implementing SIP trunks, and these issues must be faced head-on to make installations go smoothly. They have to be as clean as existing digital and analog installations because thats what the customer is expecting.

SIP trunking is hitting problems when installed quickly and without careful thought for quality of service and ongoing service management.

At The SIP School, we are in touch with many telecom installation companies. A recent conversation with the CEO of one such company counters the notion that all is well in the move to SIP trunks. He said: I have a contact in a large service provider company that has told me hes never been so busy taking SIP trunks out of customer sites and replacing them with ISDN lines.”

As the conversation developed, we learned there are companies that are not planning, testing and monitoring installations. They are simply putting systems in, getting SIP trunks connected, testing for dial tone and moving onto the next client. Customers are experiencing poor quality, dropped calls and SIP trunks simultaneously dropping then reconnecting. So many problems occurred, the customers simply said, Enough is enough! Lets rip everything out and go back to what works!” 

This frustration is borne from lack of ownership when problems arise. Installation companies are pointing the finger at the ITSPs while the ITSPs blame the installation companies.

There are issues that occur during the installation and configuration of SIP trunks, but to make things as painless as possible, there are some simple things that can be done relatively quickly.

First, its wise to do your research before moving forward. Get case studies from ITSPs and the manufacturers. Talk to them about their installation experiences and discuss issues they have come across and how they overcame them. Talk to them about interoperability testing and conforming to standards. Get recommendations. Good research early on will help you decide which companies to work with.

If you represent an enterprise looking for a SIP trunking solution, ask ITSPs to respond to your business requests. Determine if they meet your clients needs from service level agreements (SLAs) to support for the smallest of sites in the remotest of locations, even international sites.

ITSPs should also be willing to let you trial SIP trunking for free for a reasonable period of time. If so, then test the trunks using various call scenarios, such as call transfers, conferencing and so on. Also, test the ITSPs support people at various times of the day. Call them at 6 p.m. on a Friday to gauge their response time and level of knowledge.

When it comes to SIP trunk installation, you absolutely need the correct documentation for configuration of the PBX and the session border controller (SBC)/edge device to get SIP trunks to register and work. In our experience, installations go more smoothly if educated and experienced people use documentation that is clear, easy to understand and based on settings that have been proven to work in the combinations of equipment being configured. For example, if you are installing SIP trunks from Verizon, connecting to an AudioCodes SBC and then into an Avaya PBX, its important to check that they interoperate. If so, get the configuration documentation into the hands of the installers. Make it easy for people to get it right the first time.

Once SIP trunks are in and working, its not the end of the story. To ensure they continue to operate and function at their best, its wise to continuously monitor their performance and ensure that whenever any software upgrades are made to the PBX or SBC that they do not affect service. Talk to manufacturers before making any changes that may affect operation of the SIP trunks.

There is such momentum now that it is clear people will one day be using SIP trunking services exclusively. How quickly this happens, however, is up to the people providing the services.

Graham Francis is CEO of

The SIP School


Vocale Ltd

., a training, networking and Web services company. Robert Reams is senior manager of partner enablement for value-added distributor

Westcon Group


Looking for More?

Join Graham Francis and Robert Reams for the session The Secrets of SIP Trunking for Sales Professionals” at the Fall 2011 Channel Partners Conference & Expo, Aug. 24-26 in Chicago. For more information, visit

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