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SIP Trunking: Connecting Offices and Applications Across the Continent

Sonya Fullarton, a Solutions Architect with Mitel, explains how SIP trunking is more than a just an effective and cost-efficient way of converging voice and data networks.


Sonya Fullarton (left), Solution Architect for Mitel, speaks with Brownlee Thomas, Principal Analyst Serving Sourcing & Vendor Management Professionals at Forrester Research, and Allstream’s Grant Bykowy, about Mitel’s successful SIP trunking implementation.

Mitel, a global provider of business communications solutions and software, has been focusing on bringing SIP trunking to organizations for 10 years. With its extensive US operations already connected by SIP trunking, the company recently worked with Allstream to run extensive test plans on its Canadian campus in preparation for SIP implementation.

ExpertIP spoke with Sonya Fullarton, a Solution Architect with Mitel, about the company’s work with SIP trunking.

Why was it important for Mitel to run comprehensive tests for SIP trunking on its Canadian campus?

While SIP is a standard, there is enough flexibility in the standard to require testing to ensure that both sides are configured correctly in order to be compatible. Testing is also important to identify any integration issues between the SIP trunks, the data network and firewalls in order to optimize voice quality and manage bandwidth usage.

How did SIP trunking implementation benefit Mitel’s US operations?

Mitel benefited from both cost savings and improved communications as a result of the SIP implementation. Rather than having a locally maintained PBX in each site with under-utilized trunks, Mitel was able to provide a centrally managed Unified Communication and Collaboration (UCC) Solution to its US employees. Each employee maintains a direct number in their area, but the trunk usage is aggregated over multiple locations so that the trunks are used more efficiently. In addition to the cost savings provided by aggregating trunks and reducing the total number of trunk channels, Mitel saves money on long distance charges with SIP trunks.

Has SIP trunking improved the company’s business continuity capabilities?

Yes. Each component in the solution, including the SIP trunks is resilient so that there is no single point of failure. If there is a failure in a solution component the phones can fail over to another PBX and the PBX can have alternate routes to different trunking. There are different paths set up so you can have redundancy at each level and ensure that you can both make calls and receive calls at any time. Those calls are not dependent on having power in a particular city because you can have your backup in a different city. And if you have a problem with your desk phone, you can set it up so that your calls come in to your cell phone. You don’t ever have to miss a call.

It sounds like Mitel is using SIP trunking to connect more than just voice applications.

A single SIP trunk group can be used to provide service to employees in a number of regions. The SIP trunks are connected to Mitel Border Gateways and to Mitel Communications Directors. These systems are integrated with applications such as Unified Messaging, Contact Centers, web collaboration and conferencing, and a Unified Communicator Advanced (UCA) client for presence, chat, video and other information sharing. Calls over the SIP trunks, and internal calls are simultaneously presented to the user’s desk phone, home teleworker phone, mobile phone, and UCA soft phone so they are reachable at any time. UCA can be used by each employee to customize when calls are presented to any specific device based on presence, calendar status, and user preference.

Why is SIP trunking becoming such a desirable communications solution?

There are a number of reasons. SIP is a standard signaling protocol, and it allows organizations to connect their IP-PBX to services and devices from different providers. SIP trunks can be used to connect an organization to the PSTN replacing traditional phone lines or trunks. SIP can also be used in combination with traditional TDM trunks on a specialized IP-PBX to allow an organization to expand or test SIP while maintaining their existing service. They can even create a hybrid solution that maintains a mix of VoIP and TDM in the same solution, or to move to a software only communications solution. The Mitel Communications Director (MCD), for instance, can be installed on standard servers in an organization’s data center, or run as a virtualized application.  SIP trunks do not require specialized telephony hardware.

SIP trunking solutions also offer greater flexibility and cost savings for organizations than traditional TDM trunks. The number of SIP trunks purchased can be tuned to the needs of the organization. In addition, the phone numbers assigned to these trunks are not limited to the local area code. A single group of SIP trunks can be shared among users in a number of locations, and even by users working from home. Companies can use these capabilities to both lower their cost and be more efficient.

To find out more about Mitel’s successful SIP trunking implementation and testing protocols, read expertIP’s coverage of the Ottawa Experts Panel

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