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Stakeholders involved in SIP Trunk deployments

The rapid adoption of SIP Trunks is bringing multiple benefits to organisations and there are many reasons why companies decide to use them. This article is made to help in the identification and understanding of the stakeholders involved in any SIP Trunk implementation. Understanding the role of each stakeholder facilitates the deployment and helps to solve any eventual issues.


The SIP Trunk Provider

They are the actual “Phone Lines” provider. When they set up the SIP Trunks, the identification factors are called the “Credentials”.

Typical Information that is provided to identify them is:

  • The allocated VoIP Phone Numbers (including any Direct Indial Range)
  • The Primary SIP Trunk / Username Login
  • Password
  • Domain/proxy, e.g. voice@provider.com
  • Outbound Proxy, e.g. trunk.provider.com.au
  • Registered time Out, e.g. 1800 seconds
  • The Indial Number Range

The SIP Trunk Provider will normally require the end user to provide some call samples of the numbers called for both incoming and outgoing calls and the date and time. With this information, they can investigate from their end.


The Internet Provider

They provide the delivery method and for want of a better word, the “Highway” upon which the SIP Voice data packets run on.

The internet provider can also check to see that you have sufficient bandwidth and data plan to ensure that you have enough capacity. For example, you could have a 50 Gb service, but if it is often used at capacity or close to capacity, there may not be any room for the voice packets.

What this means is that, when this is the case, voice packets can get dropped and so the call would obviously be disconnected.


The IT Provider and Maintainer

They provide an important role as they are the “middle man” at the junction between the Internet Provider, the SIP Trunk Provider, and the Phone System and end user. The administer, the Router, Switches.

SIP Trunks also have the added complication that the voice packets run along the data connection and can be affected by a variety of factors such as network’s and router’s QoS (Quality of Service) issues, whereby the voice calls are meant to have priority over the data packets.

This is where it then involves the IP Maintainer, and they would run some tests to check the network, the VLAN (if it is enabled), the LAN Interface, the firewall to ensure port forwarding is enabled, and the router to make sure QoS is enabled.


The Phone System Provider

They will commonly provide a VoIP enabled Phone System that will be able to accommodate the SIP Trunks, so that the end user can make or receive phone calls.

If all these parties are not in sync with each other and understand what each of the other parties do, then experience has shown that the client will experience issues with their SIP Trunk phone lines. These issues could be and not limited to: Call dropouts, static on the line, poor quality audio and inability to make or receive calls.

The common misconception is that when your phone calls drop out it is to do solely with the Phone System. However, SIP phone lines are similar in purpose to the older PSTN and ISDN phone lines provided by carriers such as Telstra and Optus. If there is a break in the delivery of the phone lines and call traffic by the carriers, then the call would be disconnected.

In regards to SIP Trunk issues, the actual Phone System does not necessarily disconnect the calls arbitrarily. If the Phone System is not working, you won’t have any power to the phones and their LCD Screens will be blank. The most common cause is likely to be loss of power to the Phone System, so you need to check if the power is connected and working. Secondly, the Phone System maintainer can dial into your Phone System and check the error logs to help diagnose what the issue might be.



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