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 | June 08, 2012 |


Another Year of SIP Trunking Problems

Another Year of SIP Trunking Problems You would think that since SIP trunking usage has increased, problems would be decreasing. Not so.

You would think that since SIP trunking usage has increased, problems would be decreasing. Not so.

Last year, The SIP School conducted a survey, which I discussed in my blog, "SIP Trunking Isn't Easy," of enterprises' problems implementing SIP Trunking. This year’s survey does not look better; some problems are worse.

There were nearly 500 respondents this year compared to about 400 last year. The largest number of responses, about 50%, was from the U.S. The popularity of SIP trunking continues to increase. Last year 16.6% were testing SIP trunking while this year the figure was up to 26.0%. The share of enterprises not using SIP trunks dropped from 15.45 to 8.2%. The survey attracted a significant number of enterprises with 500+ employees, 37 in 2011 compared to 290 in 2012. The number of enterprises with 50+ SIP trunking sites rose from 15 to 160 enterprises.

The survey divided the problems into three categories, as shown in the chart below, "Where are the SIP Trunking Problems?":

* With the SIP trunk provider increased considerably more than the other two categories
* On the edge with NAT and SBC issues remained the same as last year
* With the PBX and its configuration increased slightly over last year

You would think that since SIP trunking usage has increased, the providers would have their implementation and operations activities running more smoothly. The survey does not indicate the providers are doing well avoiding problems.

Where are the SIP Trunking Problems?

The SIP trunk provider has increasingly been a culprit in SIP trunk implementation and operations problems, the survey found. The next chart, "Where are the Provider Side Problems?" delineates the issues discovered by the enterprises responding to the survey. The survey indicated that Codec mismatch and One-way audio problems have decreased. Incoming call transfer failure and Call conferencing with "external" caller failures changed little from the 2011 survey.

"Where are the Provider Side Problems?"

There are three problem areas that deserve more attention:

* Trunks dropping intermittently--This should not be an operational issue. Testing and operating trials of the SIP trunk should prevent this from happening once the trunks go live. Losing a call for no apparent reason frustrates callers. Since it is intermittent, IT and the provider will have to observe many calls before they can confidently expect that the problem has been fixed. It is also difficult to recreate the problem to resolve it.

* Registration failures--These issues can be attributed to incorrect account information, mistyped passwords and/or a server failure. All of these are provider-created problems that should be prevented by better information validation and administrative procedures. If they continue, then the problems are systemic and the enterprise should consider another SIP trunk provider.

* Poor quality--If the SIP trunk connection is over MPLS, this should not occur at all. If it is over the Internet, it is surprising that the poor voice quality issue should occur since the Internet providers have been improving their performance to where this should not be an issue. It may be that there is a bandwidth restriction to the Internet occurring, or the network path continuously encounters a higher-than-expected latency. There may be a bottleneck where the enterprise enters the Internet, or possibly there is no QoS implemented on the enterprise network, NAT or SBC.

Looking at the other issues, firmware upgrades for the PBX has increased as a problem. One-way audio has increased as a problem in the edge devices like the SBC and NAT. A surprising problem is the lack of SIP licenses. Shouldn't IT know this before embarking on a SIP trunk implementation? Makes you wonder if some of the problems reported are really enterprise IT issues masked as someone else’s problem.

One of the survey recommendations is:

"When it actually comes to installation of the SIP Trunks, the one thing that really stands out is the need for correct documentation that supports the configuration of the PBX and the SBC/Edge device in order to get SIP Trunks to register and work. In our own experiences we've found that installations go way more smoothly if educated and experienced people use documentation that is clear and easy to understand and also based on settings that have been proven to work in the combinations of equipment being configured."


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