Cloud Delivery and Hosting Models - Deploying and Managing a Cloud Infrastructure - page 171

exactly who is accountable during a failure or an outage. Here, we clearly distinguish among
various layers:
Infrastructure Suppliers These are suppliers of computing, networking, storage, and other
hardware and platform elements that will be used by the cloud service provider to form
its infrastructure. They are responsible for ensuring that their products and equipment are
reliable and robust.
Virtual Appliance Suppliers These suppliers provide the software-only appliances like
hypervisors and server operating systems and are responsible for ensuring the stability and
reliability of their software offering.
Network Service Provider The network service provider is responsible for availability and
keeping the network running robustly at all times.
Cloud Service Provider The cloud service provider provides the cloud computing infra-
structure and facilities and are therefore responsible for the robust and reliable delivery of
cloud services.
Cloud Consumers Cloud consumers are usually companies that offer services using a third-
party cloud infrastructure. They directly interface with the cloud service providers by making
use of the infrastructure, so they are responsible for the proper provisioning, configuring, and
operation of the cloud applications that they push to end users.
End Users End users represent the final destination of cloud services, where service
impairments and outages may be attributed to operation, configuration, and failure of
the end user device or equipment.
The different cloud service models will play a part in the determination of service outage
responsibilities as well as the terms of agreement between the parties involved in the provision
or reception of service. Also, a single organization may hold responsibilities in multiple cate-
gories, depending on the nature of their business. For example, a telecom giant like AT&T
is a network service provider, a cloud service provider, and a cloud consumer all at the same
time simply because it chooses to do business in all three categories.
Security Differences between Models
This is where most people believe the difference between the delivery models lie: security.
The argument is that on-premises, private cloud solutions are more secure than their off-
premises or public counterparts because of customization and control. This can be true in
some unique circumstances, especially if the organization deals with sensitive information
and uses proprietary safety mechanisms to protect that information.
Multitenancy Issues
Multitenancy has been considered an important factor in cloud computing scalability and
savings. It allows multiple users (tenants) to make use of the same application and database