UCaaS is an idea in which UC services can be hosted 'in the cloud' - just like SaaS enterprise applications for salesforce automation, customer service or human resources management. As with on-premise UC deployments, UCaaS gives employees a single interface from which to access all the communications tools they use on a day-to-day basis - multiple phone numbers (landlines and mobile), email, instant messaging, teleconferencing and so on. And like on-premise UC, UCaaS should also be able to take advantage of 'presence' technologies, which tell users whether the person they're trying to contact is online and the best way to reach them. And with both on-premise and hosted UC, communications will 'follow' employees - so if they're away from the office, voice calls arriving at their desktop are instantly transferred to their mobile phone, along with emails and instant messages. 

The difference between on-premise UC and the hosted UC model is that, with UCaaS, organisations can achieve the kind of connectivity they need without the need to purchase and install dedicated hardware and networking equipment and invest in the help they need to integrate these technologies with existing communications systems.

Instead, organisations pay a monthly, per-user subscription charge to have these services available from employees' desktops or mobile devices, via a web browser.  According to research from US-based market analyst firm, The Radicati Group, the benefits of buying UC as a service include less burden for onsite IT teams, lower implementation costs, access to the most up-to-date technologies, predictable costs, and flexibility. 

In theory, a UCaaS environment, offering the full gamut of telephony, messaging and presence technologies, resides on the servers of a third-party provider and is accessed by customers over the Internet. For example, it may combine a telephony system such as Cisco CallManager VOIP with Microsoft Exchange and Office Communication Server (OCS) to provide all three. 

A good provider will also mirror the environment over its own hardware resources to provide robust failover and disaster recovery capabilities. In practice, the picture's a little more complicated than that, because many organisations already have significant premises-based installations of one or more of these elements (telephony, messaging, presence). For example, many organisations have already outsourced their email systems to partners, but continue to run their telephony environment (such as an IP PBX) in-house. In response, some partners will now provide integrations between hosted and in-house systems to create a hybrid solution, with the hope that customers eventually migrate to a fully hosted UC service. 

Another issue is latency. According to Brent Kelly of Wainhouse Research, the data elements of a UC solution (such as the presence/IM engine, email/calendaring servers, shared workspace servers) can be easily provided by a virtualised, third-party environment. The real-time elements, primarily voice and video, are more difficult to migrate to a hosted service, "because a virtual environment can add latency and jitter to the time-sensitive media flows on which IP voice and video rely".

Right now, Kelly adds, most suppliers with an offering are running the real-time components on dedicated hardware, either hosted in their own data center or in a hybrid fashion, with some UC elements hosted and some located on the customer's premises.

The UCaaS message plays particularly well as a message with smaller organisations, excited by the opportunity of giving employees access to sophisticated UC functions for the price of a monthly per-seat subscription. But larger organisations that have so far held back from implementing UC internally because of technological or financial concerns are interested, too. 

Earlier this year, IT market analyst firm Freeform Dynamics asked enterprises across Europe how UC had been embraced by their organisation. Among organisations with 5,000-plus employees, 32 per cent have fully or partially implemented UC across their business. For businesses with 1,000-5,000 people, that figure slips to around 22 per cent. But companies are certainly buying UC as a service. According to Radicati Group figures, the worldwide UC as SaaS market is expected to reach 136 million subscribers (including both business and consumer customers) by 2012, from 46 million in 2008. That demand will generate sales of $28.7 billion, compared to $6.9 billion in 2008.

As discussed, UC (whether on-premise or hosted) needs to provide three elements - telephony, messaging and presence - integrated into a single interface. But the UCaaS market is moving fast, with providers quickly adding new features beyond these core capabilities. These include fixed-mobile convergence, collaboration and conferencing and integration with core business applications, particularly in comms-rich areas such as customer service and support. Companies need to find a third-party provider whose portfolio offers a close fit with the needs of their business at a per-user price that fits their budget. They'll need to ask other questions, too: