Cloud Delivery and Hosting Models - Deploying and Managing a Cloud Infrastructure - page 173

Data Segregation

Hand in hand with multitenancy, data segregation poses a unique problem for users
of public cloud environments. As multitenants sharing the same software and database
instance, all of their data is being stored in the same location, but through some clever
data segregation techniques, it will appear to each tenant that their application is unique
and separate. That does not, however, detract from the fact that data of one tenant is
mingled with another's data. One issue here is if there is a mistake in multitenancy imple-
mentation where the wrong set of data is provided to the wrong requesting tenant, the
possibility of inadvertently sharing sensitive information is tremendous.
Again, in a private cloud solution with only a single organization using the system,
multitenancy and data segregation problems are nonissues.

Network Isolation

Network isolation is an essential component in a multitenant virtualized environment like the
cloud because without it, tenants sharing the same physical infrastructure will unintentionally,
or at times intentionally, be able to consume a large portion of the network and may be able to
intrude on the networks and data of other tenants. It's essentially the same principle as in an
apartment building: you do not rent a whole floor to a group of people and have them reside
within the same four walls; instead, you subdivide and isolate the space physically using walls.
In the case of a cloud environment, the networks and spaces are separated virtually. A proper
network design that includes security and resource control will mitigate these issues.
There are two different types of network isolation that may be applicable in different
scenarios:
Network Traffic Isolation This method can be used to provide a first-level type of security
and higher bandwidth for specific tenants or users to implement special chargeback policies
and support tiered networks. This involves isolating special kinds of network traffic such as
traffic for LAN-based backups, FTP transfers, and replication traffic.
The first aspect is the creation of individual segmented networks, which can be done physically
or logically (virtually). When it's done physically, dedicated NICs will be assigned to specific
applications. For logical isolation, applications such as VLANs are required, or you could
create multiple logical listening end points to partition physical network resources. When it's
done logically, each application will be using the same physical network resources, such as
NICs, but it will see only resources and traffic assigned to it and not that of other applications.
To do this, a cloud provider must be able to understand how bandwidth is being consumed
through monitoring and control of both physical and virtual network resources. Providers
must be able to do the following:

Identify possible bottlenecks to prevent network congestion in time and gather
security data, which may help in preventing denial of service (DoS) attacks .

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