Finding software can be overwhelming. Software Advice has helped thousands of businesses choose the right SIP trunking software so they can reduce their phone bills and connect calls.

Showing 1-20 of 68 products

Nextiva Office

Nextiva's Business VoIP solutions offer small businesses enterprise-level telephony service that helps them to streamline company's communications and establish an in-house VoIP phone system. It offers an integrated and scalable PBX... Read more

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Recent recommendations: 77 recommendations

Platforms: MacWinLinux
Deployments: Cloud, On premise
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Virtual Office by 8x8

Virtual Office is a collection of comprehensive web-based business VoIP solutions from offered by 8x8. Enterprise grade phone service, virtual meetings, mobile applications, virtual contact centers and more are available to help companies... Read more

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Recent recommendations: 50 recommendations

Platforms: MacWinLinux
Deployments: Cloud, On premise
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Vonage Business Solutions

Vonage Business Solutions is a cloud-based communications solution suitable for small and midsize companies. The solution offers a business phone system that enables businesses to connect their VoIP phone system to internet-enabled... Read more

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Recent recommendations: 50 recommendations

Platforms: MacWinLinux
Deployments: Cloud, On premise
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net2phone

net2phone’s cloud PBX VoIP phone solution enables businesses to communicate in a variety of methods, whether voice, texting, messaging or web chat, over an array of devices, in the office and on the go. The net2phone solution features... Read more

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Recent recommendations: 7 recommendations

Platforms: MacWinLinux
Deployments: Cloud, On premise
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Twilio Voice API

Twilio's Voice API is a fully programmable VoIP system that helps companies make, manage and route calls to a browser, app, phone and more. Key features include call monitoring, call transcripts, call routing, PBX, auto dialer / predictive... Read more

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Recent recommendations: 2 recommendations

Platforms: MacWinLinux
Deployments: Cloud, On premise
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NICE inContact Hosted Call Center

NICE inContact is a SaaS-based call center software that helps businesses to maximizes the quality of leads and minimizes the cost of client interaction. The solution comprises of many features required to process inbound support requests... Read more

Platforms: MacWinLinux
Deployments: Cloud, On premise
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Versature

Versature’s cloud-based business VoIP services provide Canadian companies with unified communications and call analytics solutions to help manage their business operations. Versature’s key features include auto attendants, click-to-dial,... Read more

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Platforms: MacWinLinux
Deployments: Cloud, On premise
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Voxbone

SIP Trunks by Voxbone is a cloud-based VoIP solution for businesses across various industries such as travel, telecommunication, construction and manufacturing. Key features include online ticketing system, monitoring of network operation... Read more

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Platforms: MacWinLinux
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Five9 Cloud Contact Center

Five9, an early adopter of SIP trunking, combines a wide range of network connectivity options including SIP trunks and gateways with one of the industry's most robust selection of cloud-computing solutions. Read more

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Recent recommendations: 1 recommendations

Platforms: MacWinLinux
Deployments: Cloud, On premise
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Bandwidth

Bandwidth is a modern communications platform giving you access to voice, messaging, and 9-1-1 from the cloud. They offer you the power and reliability of a fully-owned nationwide all-IP voice network paired with a platform of enterprise-grade... Read more

Platforms: MacWinLinux
Deployments: Cloud, On premise
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ReadyTalk Hosted Voice

ReadyTalk is a cloud-based communication service provider and offers hosted voice, video and web conferencing and streaming webinars. ReadyTalk’s hosted voice solution, powered by Evolve IP, delivers cloud-based business phone services... Read more

Platforms: MacWinLinux
Deployments: Cloud, On premise
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SIP.US

SIP.US is a cloud-based business VoIP solution that provides SIP trunking services for IP-PBX systems and analog and digital telephone adapters. Key features include a Tier-1 redundant network, toll fraud protection, direct inward... Read more

Platforms: MacWinLinux
Deployments: Cloud, On premise
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XLite

X-Lite is a VoIP softphone solution that is useful for those with high-speed broadband connections or VoIP systems. The solution supports video calls, conference calls, regular phone use and instant messaging. It also offers features... Read more

Platforms: MacWin
Deployments: On premise
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Zoiper

Zoiper is an on-premise and cloud-based softphone solution that caters to service providers, call centers, VoIP integrators, mobile operators and businesses that require softphones independent of their service provider. It aggregates... Read more

Platforms: MacWinLinux
Deployments: Cloud, On premise
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NewVoiceMedia Cloud Contact Center

NewVoiceMedia’s tight integration with Salesforce is reflected in its AppExchange 5-star rating and the large number of positive reviews. The solution is designed to work in tandem with Salesforce capabilities and data to deliver... Read more

Platforms: MacWinLinux
Deployments: Cloud, On premise
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Business VoiceEdge

Comcast offers a cloud-based phone system known as Business VoiceEdge. Business VoiceEdge bundles SIP trunking service with hosted PBX applications. The PBX applications enable directory-based routing of inbound calls and communication... Read more

Platforms: MacWinLinux
Deployments: Cloud, On premise
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Evolved Office IP Phone System

Evolve IP is a cloud-based IP phone and collaboration solution suitable for businesses with over 50 employees. It caters to multiple industries including credit unions, financial services, health care, legal, restaurants and veterinary.... Read more

Platforms: MacWinLinux
Deployments: Cloud, On premise
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Phone.com

Phone.com is a cloud-based PBX business phone solution that caters to small businesses in industries such as retail, technology, services, lifestyle, health and education. It offers users SIP trunking service together with PBX service... Read more

Platforms: MacWinLinux
Deployments: Cloud, On premise
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eTollFree

eTollFree Predictive Dialer is an integrated cloud-based call center solution for businesses of all sizes. It works as both outbound and inbound call center software with interactive voice response built in. The customizable campaign... Read more

Platforms: MacWinLinux
Deployments: Cloud, On premise
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Digium Switchvox

Digium Switchvox provides a cloud-based and on-premise phone system that helps users in unified communications. Businesses with multiple locations deploy hybrid Switchvox systems, in which on-premise and cloud-based systems at multiple... Read more

Platforms: MacWinLinux
Deployments: Cloud, On premise
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Buyers guide


Last Updated: April 16, 2019

SIP trunking is a network service that allows businesses to connect VoIP phone systems to the traditional phone network. While this service is generally included with “per-user” licenses for cloud-based phone systems, if you have an on-premise system you’ll most likely need a SIP provider to connect calls with it.

We’ll explain what SIP trunking is, why you need it, and the primary considerations that you should factor in when deciding on a provider.

Here's what we'll cover:

What Is the Session Initiation Protocol (SIP)?
What Is a SIP Trunk
Benefits of SIP Trunking
Features of SIP Trunking Service
Important Considerations for Buyers

What Is the Session Initiation Protocol (SIP)?

Imagine the Internet as a vast network of roads and highways. On it are many types of vehicles, delivering various-sized packages (or packets, to use the technical term) containing a variety of information at a wide range of speeds. Most Internet users only ever see the contents of the vehicles traveling on the roads.

But like real roadways, the Internet has many layers below the surface. These lower layers support—and determine the quality of—the layers above them. Each layer has its own specific set of languages used to communicate within that layer. These languages are called “protocols.”

One of the lowest layers supporting the Internet is called the link layer. Within the link layer, link layer protocols organize groups of local connections into large networks. At the top, just under the surface, is the application layer. The application layer determines the quality of the “road surface” directly above it. SIP is a protocol that operates within the application layer.

Different application layer protocols are used to create different surfaces. The Internet has a wide variety of road surfaces, some favoring certain types of traffic over others: Compare a heavily loaded truck slowly climbing the rough road surface of a hill to a sports car zipping down smooth concrete. Some surfaces work better for certain purposes.

VoIP—phone conversations over the Internet—are one very particular type of traffic. They require audio to be delivered consistently with minimal delay. SIP is an application layer protocol designed to provide a very certain type of road surface for this special traffic. SIP initiates the sessions (or connections) that prepare the network to best meet the specific needs of a real-time audio connection over the Internet. 

We offer a fuller explanation in our article on the SIP protocol.

What Is a SIP Trunk?

We’ve mentioned that SIP trunking is a network service. It’s necessary because VoIP calls travel over the internet rather than the traditional phone network. This means that you need some way to connect calls between the internet and the traditional phone network, as otherwise you’d only be able to call other users with VoIP.

SIP trunking is the solution to this problem.

A SIP trunk isn’t a phone “line.” Instead, you connect to your SIP provider’s network using your internet connection. Your SIP provider utilizes specialized technologies to create a bridge between the internet and the traditional phone network, thereby connecting calls between these networks.

In some cases, you can get SIP trunking from the same company that provides your internet service, but in other cases you may need to use separate providers for SIP trunking service and internet service.

If you don’t have SIP trunking, you won’t be able to do much with a business VoIP phone system aside from admiring the server hardware. And while the traditional phone network is dying in the United States, it’s alive and well across the globe, so the need for SIP trunking isn’t going to disappear anytime soon.

Benefits of SIP Trunking

SIP trunking can cut costs in the following ways:

Lower trunking costs. Combined voice and data connections have traditionally been provided by telecoms in the form of Integrated Services Digital Network (ISDN) lines, also known as trunks. ISDN trunks come with fixed quantities of lines per trunk (for example, T1 trunks have 23 lines each). If a business needs even one additional line, it must purchase another entire trunk—meaning businesses often pay for unused capacity. SIP trunks are comprised of bandwidth, a flexible commodity, and their capacity can be increased on the fly.

Lower equipment expenses. Offices without SIP trunks use media gateways to translate between the analog PSTN and the office’s internal digital traffic. Offices using SIP trunks don’t need this expensive piece of equipment because their traffic bypasses the PSTN. A SIP trunk also makes it more practical for an office to use a cloud-based phone system rather than purchasing and maintaining an in-office hardware version.

Lower calling charges. Traditionally, and under many existing calling plans, charges are calculated based on the physical length of the PSTN line required to complete a call. Calls made via SIP trunks bypass most of the PSTN and so avoid many long-distance charges.

SIP providers also frequently offer better rates on international calls than traditional phone service providers, and most importantly, intra-office calls and calls between branch offices are frequently free when connected via SIP trunking.

SIP trunking also has a number of technological advantages:

More communications options. A SIP trunk extends, in a virtual sense, an office’s internal network to the outside world—letting remote offices, mobile employees and customers worldwide interact as if they were in the same building. Click-to-call website options for customers, application sharing and simple call transferring for work-at-home or abroad employees, for example, can all be done more easily with SIP trunks.

Meanwhile, SIP client apps can facilitate communication via a mobile device over an Internet connection, with capabilities such as voicemail, SMS messaging and more.

Features of SIP Trunking Service

The following table shows some common features of SIP trunking service:

Bursting Traditionally, if you needed more calling capacity on your phone lines, your provider took a month or longer to deliver it. SIP providers, on the other hand, can scale capacity up and down in as little as 24 hours, a vital cost-saving feature for businesses with fluctuating call volume.
Port sharing