Do you have to choose between SIP and UCaaS?

SIP and cloud don’t have to be an either/or proposition. Here’s why many organizations are choosing SIP trunking — even while adopting cloud-based collaboration solutions.

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Sooner or later, everything ends up in the cloud, right?

Or does it? Not necessarily when it comes to SIP trunking.

In a recent Nemertes Research study, 89 per cent of the 645 surveyed companies continue to use SIP trunking despite having adopted a cloud-based collaboration solution.

Nemertes VP Irwin Lazar, writing about the findings on No Jitter, calls it “startling … [that] organizations are continuing to leverage SIP trunking even when adopting UCaaS.”

According to the 2018 SIP Survey (yet another study, this one based on data from 840 organizations worldwide), many companies are taking this “hybrid approach…where they retain things like call control on-premises, utilize SIP trunks for connectivity, and then connect to the cloud to add functionality such as contact centre, call recording, IVR (interactive voice response), virtual SBC (session border controller) deployment, and so on.”

With almost everything moving over to cloud these days, this hybrid phenomenon does beg the following question, as posed on No Jitter by Lazar: “If PSTN access is part of a UCaaS license, why would organizations still need to purchase SIP trunks?”

To answer that, let’s take a look at some solid reasons to stay with SIP even after shifting to UCaaS.


If you’re in the early phase of a multi-year SIP contract, ditching it for a UCaaS-only system could mean “paying higher fees or getting stuck with duplicate fees for both providers,” warns Carrie Higbie Goetz in TechTarget.

She also raises another cost-related question: If you have other services bundled in with your SIP at discounted prices — especially if they’re services you can’t get with UCaaS — will you get dinged by having to pay full price for them if you end that SIP contract?


Higbie Goetz points out that some SIP carriers offer features like priority routing and intrusion detection that may not be included with a UCaaS solution.

Lazar lists other features that might not automatically come with UCaaS, such as “APIs for phone number provisioning, global emergency services call routing (i.e., 911), SMS/MMS in-bound and out-bound services, virtual phone numbers to establish local presence in remote markets, and more.”

If those are bundled into your SIP, will you lose them after switching to UCaas?

Phone numbers

Lazar notes in his blog post that if you shift PSTN access from your SIP trunk to a UCaaS provider, you’ll have to transfer all your phone numbers over to that cloud provider’s domain. Maybe that’s no biggie for a smaller company, but Lazar suggests that for enterprises “with tens of thousands of phone numbers,” the headaches and potential downtime might not be worth it.

The bottom line is that SIP and cloud aren’t either/or propositions. You don’t have to choose between one or the other. They can — and do — work well together, as solutions that complement (rather than compete with) each other.

As the SIP Survey researchers summarized in their annual report, “a lot of companies are still operating successfully and purchasing on-site solutions where sometimes it can be cheaper to run this kind of system than to pay (cloud-based) subscription charges for lots of handsets/accounts every month.”

Images: yuoak/iStock; TECHDESIGNWORK/iStock

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