The underlying operating systems available to tap into include Windows Server 2003 and 2008 as well as Red Hat Linux 4.0 and 5.0. Novell SUSE Linux support is coming. Customers can choose between a half dozen hardware configurations -- different set-ups of memory and storage per virtual server -- to support the OS and apps.

As in many utility computing services, companies will pay for only the capacity they need. They'll be charged based on the average peak utilization of CPU and memory during a month, and the services can boost up to double that average peak use. The plan will also include a comprehensive service level agreement that includes a 99.9% uptime guarantee encompassing everything from the firewall to the network to operating system, and companies can add SLAs to application services like a managed deployment of SAP.

Synaptic Hosting will get its scale and connectivity from five of AT&T's extant "super Internet data centers" in San Diego, Singapore, Amsterdam, Annapolis, Md., and Piscataway, N.J. As more customers come on board, AT&T hopes to get even more of its existing infrastructure upgraded to handle the traffic.

Those data center configurations are today virtualized on VMWare technology, but AT&T is also working with Citrix Xen and Microsoft Hyper-V for future options. The network itself is application aware in order to minimize latency and other application specific issues.

Synaptic Hosting allows businesses to customize storage and security features to make sure the cloud has the right scale and access constraints they need. AT&T's BusinessDirect portal, already in place for other managed and hosted business services, will let customers manage and monitor their "virtual IT environment" and AT&T will offer additional personalized support. Customers will be able to manage and monitor individual virtual servers, see a map of their virtual infrastructure, check versions, manage operating system settings and so on. They can manage individual apps, or let AT&T do that for them.

Despite the flexibility, the service isn't for everyone. It's really targeted at enterprises, not small businesses. Start-ups looking to use AT&T to power their Web applications might want to look elsewhere, too. However, AT&T hopes to expand the scope and scale of its utility computing offerings. Synaptic is just the first entrant in a larger product line, but it's unclear what specific services may come next. That may be for the customers to decide.