This article is for the many buyers over the years that wanted to understand how the technology of SIP Trunking for Business Phone Services works.

First, let’s start with, what is SIP trunking? SIP Trunking is a phone service that provides VoIP connectivity to your PBX. This is to make and receiving telephone calls over the internet. We don’t provide the internet connection to you, but we do provide the telephone services. Service providers like Comcast, Fairpoint and others provide the internet connectivity that VoIP works on in your business.

In many cases, SIP Trunking replaces the analog phone companies and provides greater flexibility with more features and ease of use from any location. So what actually goes into SIP Trunking? Let’s dive in depth together!

Business Phone Services


What are the elements of SIP Trunking?


This is a central device in a telecommunications network that connects phone calls from one phone line to another. This can be done on legacy networks or over the internet.


Session Border Controller
This is a device used in VoIP networks to gain control over the signal and media streams. It is used in setting up, conducting and tearing down calls. The session border controller deals with security and quality of service in the VoIP call.


This is also known as voice origination and is the part of the process that collects the calls initiated by the party calling you on a telephone exchange. Originating carriers provide the DID’s the phone numbers for SIP Trunking.



Termination & Origination Carriers
Some of the largest VoIP carriers today are Vonage, Broadvox, Earthlink. There are many carriers on the market today, and no one carrier provides 100% coverage. Each carrier has it’s own pricing plans and phones to go with your plan. Many carriers have hidden fees associated with their plans that drive price up. The carriers provide the termination and origination of your phone service.


Wholesale VoIP

Many SIP Trunk providers purchase through a wholesale provider. Most wholesalers are specific to regions, and many vary in the level of services they offer. They all vary in pricing for their services.


VoIP Bandwidth

SIP Trunk requires a certain level of bandwidth across your entire network to properly work and provide you with a quality phone call.



There are several elements to resiliency. The first part deals with the hardware in your network. It deals with the Softswitch, session border controller, routers, ethernet switches and often can be redundant. The second part is Geographic, which can be having an alternate setup in another location that is redundant. The third is Provider, this is where the customer has two separate SIP trunks from different carriers. They can use this to split the traffic, one for inbound and one for outbound or use one as your primary and the other as a backup (redundant).


These are many of the elements that go into SIP Trunking in providing business class telephone services for our customers through the Vermont and New Hampshire region.

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