Page 563 - Cloud computing: From paradigm to operation

XaaS 3

• Virtualization infrastructure

The main role of the virtualization infrastructure is to support hardware and software resources and
create virtual resources (e.g., VMs). The virtualization infrastructure can use a virtualization
function, called a hypervisor, to manage hardware resource efficiently. A hypervisor can abstract
physical hardware resources and assign them dynamically to a virtual desktop. In this case, the end
user's application runs on the virtual desktops provided by the virtualization infrastructure. The
virtualization infrastructure supports high availability features (e.g., multiple VMs are created from
the same VM template) with pre-defined configuration parameters.
• Virtual desktop delivery
This component is responsible for encapsulation and delivery of either access to an entire
information system environment, or the environment itself to a remote DaaS client through the
network. A protocol for virtual desktop delivery provides the communication channels between the
DaaS client and the DaaS platform in order to transfer all the interaction information. The interaction
information includes display information, control and configuration information, monitoring
information, etc.
DaaS can be serviced by either a personalized virtual desktop or by a virtual desktop from a shared
pool. In the case of a personal virtual desktop, there is a one-to-one mapping between a virtual
desktop and a cloud service user. Each user is assigned a virtual desktop that can be personalized
and customized. These changes are available to the user each time that user logs on to his or her
personal virtual desktop. For a shared virtual desktop pool, a single OS image is replicated across
many VMs and users can reuse a single VM over time. As users connect to the shared virtual pool,
they are dynamically assigned a virtual desktop. A shared virtual pool allows for uniformed
experience across all end users, while combined with simplified administration means.

6.3 Interaction between DaaS components
To illustrate the DaaS operation concepts based on Figure 6-3, the various steps of an example interaction
for DaaS are shown as follows:
• A DaaS client accesses a connection manager through a security protocol (such as secure shell or
transport layer security) and the connection manager validates the user with a user-ID and
associated password.
• The connection manager identifies a corresponding user profile and, in order to assign appropriate
virtual resources in the virtualization infrastructure, a provisioning operation helps the connection
manager to allocate the virtual resources that satisfies the user's hardware configuration and is
optimal to the computing environment.
• If there are no proper virtual resources, the connection manager requests the virtualization
infrastructure to create such virtual resources according to the hardware configuration requested
by the user or a pre-defined hardware configuration.
• After such virtual resources are assigned or created, the connection manager applies the user
profile, including installation of OS and applications, to construct a virtual desktop.
• A connection to deliver a corresponding virtual desktop is created in the virtualization infrastructure
and the information of the connection is dispatched to the connection manager.
• The connection manager sends the connection information to the DaaS client and the DaaS client
connects to the virtual desktop in the virtualization infrastructure.
• The DaaS client communicates with the virtual desktop through the network using a delivery
protocol for the virtual desktop.

• When a DaaS user terminates a virtual desktop service, the DaaS client executes a log out operation
without loss of user data.
• During the log out operation, the connection manager updates the modified user profile in a user
profile pool to keep the most recent information, and releases the VM resources.

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