Direct answer
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UCaaS stands for unified communications as a service. It's a business phone system, sold together with tools such as meetings and messaging, that a provider runs in its cloud and bills by subscription. A desk phone handles the calls. An app on a computer or mobile phone handles calls and the other tools. The provider maintains the system behind them. The parts are covered one by one in the core components of a UCaaS platform.
"Unified communications" describes the product. Calling, meetings, messaging and voicemail come from one provider and run through a shared set of apps, so a person's extension, chat and meetings belong to one account. How tightly the pieces connect depends on the service. Atlantech Online's UCaaS page gives two examples from its own: employees send instant messages from the softphone app, and a presence indicator updates from a person's phone and calendar status.
"As a service" describes who runs it. Suppose a business owns its phone system. That system is a PBX, a piece of equipment in the office that the business bought and has to maintain. With UCaaS the equivalent system sits in the provider's data centers. Atlantech's page says its hosted phone system is on its cloud and not in the customer's office.
That change in location changes who does the upkeep. The provider maintains the system and its capacity, and you add or remove users as headcount changes. The costs and control shift with it, which is the subject of how UCaaS compares to an on-premises PBX.
Moving the phone system to a provider doesn't move the whole job. People still need something to call on, whether that's a desk phone, a headset and a computer, or a mobile phone. Atlantech's page describes a softphone, which is an app that acts as a phone, and mobile apps for Android and iOS that take business calls away from the desk.
Those devices have to reach the provider, and the path between them is yours to look after. Calls from the office travel over whatever connection links the office to the provider, and before that over the office's own cabling or Wi-Fi. A person working from home or on a mobile network uses that connection instead. The provider can run its side well and a call can still break up on a congested path at your end. We work through the sizing in what UCaaS bandwidth requirements to plan for.
Then there's the setup, which follows how your business works. Someone has to decide which number rings which person, what callers hear after hours and who answers the sales line. The provider supplies the controls and can help with the first setup, but those choices come from you, and they need revisiting when the business changes.
Atlantech's two advertised price cards show how a UCaaS subscription is put together. Both are priced per user per month. The Business Line starts at $12 per user per month. Its card lists call handling features such as call forwarding, transfer, hunt groups and park and pickup, with unlimited local and domestic long-distance calling. The Premium Line starts at $18 per user per month, and its card lists voicemail, conferencing, collaboration and a softphone.
Two cards under one UCaaS heading show why the name alone doesn't describe a plan. One card is written around handling calls and the other names conferencing and collaboration. A buyer comparing plans, from this provider or any other, is comparing what each line includes, and the quote confirms it. Both prices are starting rates, so the quote also sets the final rate, along with the contract term, taxes and setup charges. Other providers publish their own rates and terms, set side by side in how much UCaaS costs per user.
VoIP is the technology that carries voice over a data network. UCaaS calling runs on it, so the two aren't alternatives. A phone-only service delivered over IP is VoIP, and so is the calling inside a UCaaS plan, which is why the difference between UCaaS and VoIP is one of scope and not of technology.
SIP trunking connects a phone system you already own to the outside telephone network over an IP data connection. It suits a business that wants to keep its PBX. Atlantech's page describes a path between the two, where SIP trunking extends a softphone to the users of an existing PBX, so the business gets some unified communications before it replaces any equipment. The trade-off between keeping the PBX and moving it is in the difference between SIP trunking and cloud PBX.
CCaaS applies the same hosted model to a contact center. The line between them is use. UCaaS supports individuals and teams, and CCaaS supports a call center, where the queuing, routing and reporting needs are substantially different. A company can run both, with most staff on UCaaS and the support team on CCaaS, and the difference between CCaaS, UCaaS and CPaaS sets the acronyms side by side.
AT&T Business