Principles, Methodology and Tools for Engineering Cloud Computing Systems - Advanced Design Approaches to Emerging Software Systems - page 262

ous “Sections”, describing virtual disks, logical
networks and hardware resource requirements
of each virtual system. Virtual machines sharing
common descriptive elements can be grouped
in virtual system collections. Users may specify
a virtual machine booting sequence and the de-
ployment time configuration of virtual machine
instances is supported through the definition of a
communication protocol between host and guest
(the target virtual machine) via the use of crafted
CD/DVD images to be used as boot disks during
the start-up process. A simplified example of this
service definition language is shown in Figure 4.
There are a number of requirements however
that OVF in itself does not meet. In particular it
is focused solely on initial deployment of fixed

size services, and does not provide measures to
handle potential changes in requirements over the
lifetime of a service. It also does not handle po-
tential migration across hosts, nor issues related
to performance and service level quality. These
are crucial requirements in clouds and such lan-
guage abstractions must be introduced into the
standard.
We have proposed a number of extensions
to OVF to facilitate the deployment of OVF-
described resources in Clouds (Galan et al. 2009).
This includes attribute and section changes to in-
corporate support for service components dynamic
IDs in elastics arrays, IP dynamic addresses and
elasticity rules and bounds. We consider here two
particularly important extensions, automated scal-

Figure 4. OVF-based Cloud Service Specification Example (simplified)