At first glance it may seem that CSPs are just taking on the cost, risk, and responsibility of on-premises data centers. It is true that CSPs relocate IT infrastructure to their own data centers, but they don’t just physically move computers to a new location. Moving existing computers to a bigger building would be more of a simple technology transfer than a technology innovation.

Cloud computing offers far more than simple infrastructure transfer. Virtualization technology made cloud computing possible. Virtualization allows one physical computer to run multiple images of operating systems (OSs) in virtual environments. Each running image is called a virtual machine (VM). A VM looks, feels, and operates just like a physical computer. When you log into a VM it is difficult, or even impossible, to determine if you’re connected to a physical or virtual computer. Virtualization allows a single computer to run multiple VMs, each with its own operating system. Users of VMs each think they are running on dedicated computers, but they actually are sharing resources among potentially thousands of other users. The cloud computing model depends on virtualization to allow a data center to support many more VMs than physical computers present in the infrastructure.

CSP customers can launch, use, and even resize VMs based on need. If a business has a busy month starting, they can use dynamic provisioning to request (and pay for) more memory, CPU power, or external storage. When business demands decrease, the business can provision resources back down to use less and pay less. The ability to provision up and down through virtualization provides CSP customers cost control and provides CSPs the ability to efficiently use their physical IT assets.

Because VMs operate within a virtualization environment, also called a hypervisor, a running instance of a complete operating system can be represented as a collection of files. Memory, processes, and data all look like files. You can store a copy of these files at a specific point in time, creating a VM snapshot, which proves extremely useful for backups and fault tolerance. Instead of relying on duplicate hardware with replicated data, businesses can recover from crashes simply by spinning up another VM and restoring the most recent snapshot. (Of course, the real recovery process is a little more involved than a few simple steps, but cloud computing makes it far easier than ever before.)

Up to now we’ve presented cloud computing as only providing complete VMs as if you added a new computer to your network. Providing newly installed operating systems as VMs is only one type of cloud service. Some businesses want to take advantage of all that CSPs can offer, but don’t want to manage their own virtual computers in someone else’s data center. Here are the main types of cloud services and what each provides:

• Infrastructure as a Service (IaaS)—This is the original service type. CSP customers can provision and launch any number of VMs that originally appear to be newly installed operating systems. It is the responsibility of the CSP customer to configure the VM and install any software they need to make use of the VM.
• Platform as a Service (PaaS)—Some businesses need more than just a new OS when they create a new VM. They may want to support application development and need development libraries, compilers, databases, and web or application services. The PaaS service type provides VMs with pre-installed and configured software that gives users a stable platform from which to start.
• Software as a Service (SaaS)—Often considered to be the highest level of cloud service type, SaaS offerings rent access to specific software applications, such as SalesForce.com. SaaS customers do not want to install or manage software—they just want to use it. All of the installation, configuration, and maintenance responsibilities fall on the CSP. This service type is generally the most expensive, but the one that requires the lowest level of customer involvement.
• Anything else as a Service (AaaS, also commonly called XaaS)—Extending the SaaS service type, many businesses offer their SaaS solutions as professional services, not just software their customers can use. The list of service offerings is always growing and currently includes services such as Security as a Service, Database as a Service, Blockchain as a Service, and Privacy as a Service.

Cloud computing’s focus is flexibility. Virtualization makes it possible to provision just the right infrastructure and software to meet specific needs. Accessible networking provides unparalleled connectivity; however, there is a tradeoff between ultimate flexibility and security.

The public cloud model is the most common view of cloud computing. A public cloud, also called the public delivery model, consists of CSP services offered to any subscribers using the Internet to connect. The CSP hosts infrastructure and software for many different types of businesses. Some of the largest public CSPs are Windows Azure, Amazon Cloud Services, and Rackspace. A public cloud provides lots of flexibility, but security and control are issues.

To restrict who can access your data and infrastructure, some businesses use a private cloud. With a private cloud, also called a private delivery model, the virtualization layer is managed by the owning organization as opposed to a CSP. The physical infrastructure could be in the organization’s data center or could be hosted by a CSP, but it is accessible only by users the owning organization authorizes. A private cloud allows the owning organization to provide more security for its data and processes than a public cloud.

The third main delivery model, the hybrid delivery model, combines the best of the public and private delivery models. A hybrid cloud includes one or more public cloud services and one or more private cloud services. Private clouds tend to be more expensive than public clouds and require more effort to manage. A hybrid cloud allows an organization to use private clouds where they need to, and use more cost-effective public cloud services for less sensitive applications and data.

Cloud computing has revolutionized the way businesses consume IT resources. CSPs can relieve many IT headaches (for a fee) but can’t solve every problem. Anytime a business moves IT assets outside its own trust boundary to another environment, identity and access become issues. You’ll encounter some of the issues and obstacles of cloud computing as you learn more about network communications, but don’t let that minimize cloud computing’s value. With a little planning and a good security policy, cloud computing can help businesses leverage IT assets and manage costs.