What is SIP Trunking?

SIP (Session Initiation Protocol) is a protocol for streaming communication, including voice, video, and other media in real time. There are multiple services and applications which can make use of this protocol, which is used to transmit information between multiple end points. What makes SIP particularly useful for businesses and other organizations is its flexibility, which is due, in part, to SIP trunking.

What Makes SIP Special?

SIP is, essentially, a VoIP service. But it offers users the chance to transmit much more than simple audio. Not only is it possible to conduct real time video conferencing between two points using SIP, it’s also possible to simultaneously transmit files and share screens. This makes SIP a fantastic choice for multimedia communication and collaboration.

Furthermore, many SIP providers offer flexible, scalable plans. Unlike prior communication options, like PRI 23 (Primary Rate Interface), SIP is not limited to a certain number of channels. Not only can SIP accommodate an ever expanding number of users on the same call, but businesses do not have to plan ahead for changes in user numbers with most service providers. Rarely does SIP require contracts regarding user number, and pricing scales up and down according to actual use. Providers can spin up capacity during communication spikes, and automatically adjust when call volume is reduced.

In addition to a pay-for-what you use pricing model, SIP allows organizations to use the same platform for the majority of their communication channels, including video conferencing, SMS, IP messaging, voice, and file sharing. SIP applications are highly customizable and have a high level of user control, offering the opportunity to tailor applications based on organization, department, locale, target customers, etc.

Finally, SIP is extremely reliable. With reputable services, customers can expect near 100% uptime, with many vendors guaranteeing upwards of 99% uptime.

What is a SIP Trunk?

In order to understand what a SIP trunk is, it’s important to grasp that there are essentially two domains in SIP architecture: private and public.

Your organization’s “private” domain consists of local hardware, including but not limited to an onsite unified communications server or PBX (private branch exchange) system.

The public domain, on the other hand, refers to the part of the network which allows public landline access. It consists of equipment which is overseen by your SIP service provider/ITSP (internet telephone service provider).

These two domains have to be connected in order for your organization’s communications to flow seamlessly. This is accomplished using a SIP trunk.

Choosing a Service

There are a multitude of considerations when choosing a SIP trunking service.

Pricing model

There are two basic categories of pricing model: traditional and elastic. Traditional pricing models estimate the maximum usage anticipated during a contract period (often 1-3 years) More and more vendors are offering elastic pricing models, however, which is good news, especially for SMBs (small to mid-sized businesses). While enterprise level organizations may be able to accurately predict call volume, but for SMBs , unpredictable changes in call volume can be significant. When contracts are required, contract length is another important aspect to consider.

Inbound and Outbound Services

Not all organizations require both inbound and outbound SIP service. Pricing varies for each from vendor to vendor, and can be based per minute, by user numbers, or a combination of the two. Prices may also vary based on whether or not the calls are local, long distance, or toll-free.

Additional Features

SIP trunking services often offer additional features, like emergency calling, address association, call recording, call storage, and retrieving stored calls. Any of these—or none of them—may be required for your organization, so it’s important to determine which of these or other features your short-listed vendors offer.

Of course, as SIP trunking services grow increasingly necessary and attainable for businesses and other organizations of all sizes, there are more quality, competing vendors every day. With all of the options available, it can be daunting to find the service that offers everything your organization needs within your budget constraints.

TopAdvisor.com offers you the chance to compare and contrast pricing models and rates, features, and additional services from the industry’s most trusted vendors. Check out our VoIP guide for an unbiased look at SIP trunking services, and much much more!