Gary Audin
Gary Audin is the President of Delphi, Inc. He has more than 40 years of computer, communications and security...
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Gary Audin | November 25, 2016 |


SIP Trunk Providers Still Learning

SIP Trunk Providers Still Learning As The SIP School's sixth-annual SIP survey shows, many of the same problems from the same sources persist year after year.

As The SIP School's sixth-annual SIP survey shows, many of the same problems from the same sources persist year after year.

You would think by now that SIP trunking would be a commodity, that installation should be almost plug and play, and that SIP trunking services providers should know what to do and how to resolve any problems that occur. It turns out this is not the case, according "The SIP Survey 2016" results.

In its sixth year, "The SIP Survey 2016" is conducted by The SIP School. The survey has proven to be extremely popular, with 929 professionals -- SIP users and SIP Internet telephony service providers (ITSPs) -- responding in 2016. By country, the breakdown of survey respondents is:

  • U.S. -- 49%
  • Canada -- 8%
  • U.K. -- 6%
  • India -- 5%
  • Mexico --3%
  • Others -- 29%

The survey results are not particularly encouraging. Many of the same problems from the same sources persist year after year. It makes me wonder if anyone's reading the survey results. It appears that the lessons reported are not necessarily learned by those involved in SIP trunk implementations.

SIP Trunk Interests
Where the respondents consider themselves in the SIP trunking environment is important to understand. Some survey responses have changed since 2015, as shown below.

Comparing 2016 results to 2015 results...

  • The first point of interest is that 60% of respondents are not SIP trunk providers.
  • A bit of a surprise is that 38.54% of respondents are using SIP trunks, down from 40.35% in 2015.
  • In 2015, 7.83% of respondents were researching SIP trunking. In 2016, 6.57% are researching SIP trunking.
  • Those ready to deploy SIP trunks rose from 2.19% in 2015 to 2.58% in 2016.

Note that 40.15% of respondents, up from 37.43% last year, are with SIP trunk service providers. In the remainder of the survey, The SIP School zeroed in on SIP users, so the ITSPs did not respond to questions on SIP trunk problems.

Problems Persist
As shown in the graphic below, SIP trunk providers are still the major culprits when it comes to problems in SIP trunk implementations. The provider problems did decrease slightly from 34.82% in 2015 to 33.63% this year, but that's not a significant change. One of the positive conclusions is that the number of organizations that had no problems with SIP trunking increased significantly, from 16.83% in 2015 to 21.73% in 2016 -- or one out of five implementations. Another significant point is that the number of respondents who did not have SIP trunks decreased from 11.03% in 2015 to 4.46% in 2016, which leads to a more accurate view of what's happening with SIP trunking.

The next major culprit of SIP trunk problems is the edge device, primarily the session border controller. SBC problems increased from 21.28% in 2015 to 23.51% in 2016, whereas PBX issues stayed nearly the same, rising less than 1% year to year. (Note, I will inspect these equipment vendors in my next post.)

The nearly 22% of respondents who indicated they never have any problems with SIP trunks mentioned a variety of reasons for their successes. Beyond good luck, their verbatim responses include:

  • Good ITSP planning and support
  • Knowledgeable internal staff (certifications from the SIP School help)
  • Good planning, support [by] an excellent Engineering team and very granular testing of all call operational scenarios and types
  • Lots of network bandwidth (there never seems to be enough)
  • We have only had minor headaches, mostly with call quality
  • Good support, decent testing with a SIPconnect- based service
  • Provider delivers RFC compliant SIP and documentation for hooking it up with our SBCs

Perennial Pain Points
I find it irritating and frustrating that the same problems with SIP trunk providers exist year after year. Some of problems seem to have even worsened, as reflected in the graphic below.

One problem that persists with a high degree of failure is one-way audio, increasing as an issue from 2015 to 2016 -- 43.43% of respondents last year compared to 45.45% this year. The second-most prevalent problem is codec mismatch, which increased from 29.71% to 32.73% from 2015 to 2016. Another problem is no audio, relatively consistent from 2015 (23.49%) to 2016 (23.64%).

These three problems are really configuration issues. The providers either don't have good documentation, are not training people properly, or someone is tweaking the configurations to solve another issue and creating new problems (for more on training, see my earlier post, "Get SIP Certified for Success").

The next three problems are disturbing, and reflect on SIP trunk providers' internal operations. While the percentage of respondents indicating that trunks dropping intermittently did decrease significantly, from 42.86% to 30.91%, trunk registration failures and ITSP server failures increased significantly, from 16.57% to 20.91% for the former and from 19.45% to 25 .45% for the latter. This indicates that SIP trunk providers' internal organizations and infrastructure need work.

The percentage of respondents that experienced poor voice quality, latency, jitter, and packet loss, dropped considerably year over year, from 55.71% in 2015 to 32.73% in 2016. This is encouraging, even though a third of respondents dealing with these issues means there are still a lot of poor-quality phone calls.

The last two items, incoming call transfer failure and conference call conferencing with external callers, failed a modest amount of time.

Wisdom From Experiences
Before a SIP trunk deployment, conducting a network assessment is a best practice recommendation. You'll want to determine if your network is really ready for the quality requirements of a SIP trunk implementation, and using WAN assessment tools or engaging a consulting service to test your existing links is a good idea. Your prospective provider may even be able to perform the assessment.

The assessment should highlight potential issues, including link instability, router problems, and bandwidth limitations. MPLS networks can deliver high quality of service, but can be expensive. Software-defined WAN options, which can compete with the MPLS on cost, are worth investigating. However, the SD-WAN provider needs to deliver an "assured" service.

For more on SIP trunking, see:


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