For the past four years, The SIP School™ has conducted a survey of enterprise successes and problems with implementing SIP trunks. The 2014 survey found only 17.63% of the nearly 1,000 respondents worldwide have no problems with SIP trunks. That leaves 82.37% with one or more problems.
There are five potential sources for SIP trunk problems: the provider, SBC vendor, PBX vendor, VAR, and the enterprise. The SIP survey looks at the first four but not at the enterprise. The survey found that about 24% of the problems are with the provider, which changed very little from past surveys. This makes you wonder what providers are or are not doing to improve their track record.
The Survey Says
The survey questioned the respondents relating to nine problems. The table below shows the problems from most to least common. Most of the problems have changed little since the 2013 survey, except for "Trunks dropping intermittently," which decreased about 7.7%. On the other hand, "Codec mismatch," which should be much lower on the list, increased 4.4%. The total percentage figures add up to more than 100% because some respondents had more than one problem.
It appears that many of the problems are incorrect configuration settings. ITSPs provide settings necessary for successful operation, and enterprises or VARs are not doing their jobs ensuring the settings are correct. These settings include the IP address, DNS address, port numbers to be used, RTP packet rate, and codec to be used.
Avoiding the Problems
You should ensure you and the VAR have the most current documentation. This does not guarantee that problems can be avoided. Configuring the implementation is a process that should not be rushed. Double check everything beforehand.
VARs are not the most competent implementers. In another part of the survey, the respondents said that only about 17.7% of the VARs were of "great assistance showing good technical skills." By comparison, providers and equipment vendors were rated 40% to 44% with "great assistance showing good technical skills." The VARs are clearly far behind in this measure of competence.
My own view is that resellers are not getting the message. They either ignore their shortcomings or choose to remain ignorant. Maybe the resellers would get the message about improving their support if the justification was based on truck rolls and labor costs that could be reduced with better training.
Another issue is that, when ordering the SIP trunk, you must consider compatibility. If your equipment settings do not match what the provider can deliver, there is no chance of success. Thoroughly review the compatibility issues with all four participants (trunk provider, SBC vendor, PBX vendor, and VAR). Look for assumptions that may turn out to be invalid. You may not be not a SIP trunk expert, but you can ensure that the compatibility issues are resolved before the trunk is ordered. Be skeptical of all parties involved.
The Provider Implementation Checklist
There is about an 82% chance you will have one or more SIP trunk implementation problem. The list in the table above shows the most common problems in descending order of occurrence. Anticipate them. Use the table to create a checklist to verify the provider implementation.
One question that was not covered in the survey is the traffic capacity of the SIP trunk. You order the trunk by the number of simultaneous sessions it will support. When trialing an implementation, attempt to load up the SIP trunk with the maximum traffic to ensure it operates successfully under full load. This is the final test. Even if all the previous individual tests work, you may have an unexpected problem under full load.
Conclusions
SIP trunk implementations can succeed. By far, most organizations that attempt to implement SIP trunks do not revert back to legacy T1/PRI trunks. They make it work. Most organizations do not change providers but instead work with the provider to resolve problems. The SIP technology is good; it is the installers that create most of the problems.
Look for my next blog, "SIP Trunks: Equipment Problems" to round out this discussion.
