Isolation managed independently and taken care of.

Among all the services, 1 isolation of network is the
major issue. It can be either performance or management
isolation etc. Let us say, multiple network services exist
over a shared physical infrastructure, performance
problems in a service may spread out in the whole network
and may cause performance degradation of other services.
Thus, we have to ensure that Network Virtualization
provides complete isolation of any Logically Isolated
Network Partitions (LINPs) and supports diversified
applications, service and architectures.
2) Flexibility
In Network Virtualization user must be provided with
flexibility to use a random topology, forwarding or routing
functions and protocols.
3) Management
Since each network is independent from the other, it has to
be managed independently and taken care of. Also, At the
same time, the management system for the virtual
network has to collaborate with the management system of
physical infrastructure. It is therefore necessary to
carefully define which part of management can be done by
the management system of the virtual network, and how to
align it with that of physical infrastructure. Moreover, if
the isolation is not perfect, alignment with the management
systems of other virtual networks also becomes necessary.
4) Security
Network Virtualization should ensure complete isolations
from other network partitions so as to manage failure
malfunction or security issues. Security problem in one
network should not affect another network partition in same
shared physical infrastructure.
AWS is a real world example. Their cloud based
virtualization also visualizes the networking. A little closer to
home is the using VMWare, where you specify a vlan in
VSphere or workstation. Another example, a bit older school
is the partitioning of firewalls and other network devices,
where you run virtual instances of switches or routers on a
single box. EC2 allows scalable deployment of applications by
providing a web service through which a user can boot an
AMI to create a virtual machine, which Amazon calls an
“instance”, containing any desired software. AWS supports
two major types of virtualization