The virtualization can be described in a generic way as a separation of the service request from the underlying physical delivery of that service. In computer virtualization, an additional layer called hypervisor is typically added between the hardware and the operating system. The hypervisor layer is responsible for both sharing of hardware resource and the enforcement of mandatory access control rules based on the available hardware resources. There are three types of virtualization: full virtualization, para-virtualization and operating system level (OS-level) virtualization.

1. LINUX Virtualization

Running other code under LINUX
surajsuraj

2. Environment Virtualization
Citrix/MetaFrame – Virtual desktop under Windows NT. aka Windows Remote Desktop
Protocol
VNC, Dameware – virtual console.
XWindows – virtual console
Mac OS RDP – same as Windows.
WUBI.EXE

3. Hardware Emulation
IBM – Virtual Machine (VM) OS
Also using code:
Processor virtualization
Instruction set virtualization.
Slow. Usually requires OS (re-)installation
Examples: KVM (uses QEMU), Solaris Domains, DOSBox, DOSEmu, WINE

4. Processor Virtualization
• “Native” or full virtualization: virtual machine that mediates between the guest
operating systems and the native hardware. Certain protected instructions must be
trapped and handled within the hypervisor because the underlying hardware isn't
owned by an operating system but is instead shared by it through the hypervisor.
• This form usually requires specially virtualization CPU processors (Intel, AMD) for
performance. The only constraint is that the operating system must support the
underlying hardware. Close to hardware-level performance.
• The biggest advantage of full virtualization is that a guest OS can run unmodified. OS
is usually “ported” to the hypervisor machine.
• Examples: VMWare.

5. Processor Virtualization
Paravirtualization: uses a hypervisor for shared access to the underlying hardware but
integrates virtualization-aware code into the operating system itself. Obviates the need for
any recompilation or trapping because the operating systems themselves cooperate in the
virtualization process.
Also requires specialized CPU hardware but not to the same level as “native” virtualization.
Close to “native” performance.
Guest OS is (re-)installed to run virtualized.
Examples: LINUX Xen, User Mode LINUX (UML), Microsoft Virtual PC.

6. OS Level Virtualization
• OS Level Virtualization: Virtualizes servers on top of the operating system itself -
uses a single operating system and simply isolates the independent virtual servers
from one another (code, memory, filesystems).
• Doesn’t use special virtualization hardware
• Uses a lot of underlying OS resources – memory, filesystem space.
• Original concept – BSD “chroot jail”
• Examples: LINUX: lxc “containers”. Solaris “Zones”

7. Hardware support for virtualization
• IA-32 (Intel x86) supports four rings of protection, where level 0 (the highest privilege) typically
runs the operating system, levels 1 and 2 support operating system services, and level 3 (the
lowest level) supports applications.
• In IA-32 (x86) architecture certain privileged-mode instructions do not trap, and can return
different results based upon the mode. This is problematic when attempting to virtualize different
operating systems at different levels.
• Hardware vendors have recognized this shortcoming (and others), and have produced new
designs that support and accelerate virtualization. Intel’s new virtualization technology supports
hypervisors for both the x86 32-bit (VT-x) and Itanium® (VT-I) 64-bit architectures. The VT-x
supports two new forms of operation, one for the VMM (root) and one for guest operating
systems (non-root). The root form is fully privileged, while the non-root form is deprivileged
(even for ring 0).
• AMD is producing hardware-assisted virtualization technology, under the name Pacifica which
Pacifica maintains a control block for guest operating systems that are saved on execution of
special instructions. This allows a virtual machine (and its associated guest operating system) to
run until the VMM regains control. Pacifica also amends address translation with host and guest
memory management unit (MMU) tables.
• These hardware virtualization can be used by a number of virtualization techniques, including
Xen, VMware, User-mode Linux, and others.

8. Virtualization Products
•
Bochs and QEMU are PC emulators that allow operating systems such as Windows or Linux
to be run in the user-space of a Linux operating system.
• VMware is a popular commercial full-virtualization solution that can virtualize unmodified
operating systems.
• Xen is an open source paravirtualization solution that requires modifications to the guest
operating systems but achieves near native performance by collaborating with the hypervisor.
• Microsoft Virtual PC is a paravirtualization virtual machine approach.
• User-mode Linux (UML) is another paravirtualization solution that is open source. Each guest
operating system executes as a process of the host operating system.

9. Virtualization Products
coLinux, or Cooperative Linux, is a virtualization solution that allows two operating systems to
cooperatively share the underlying hardware.
Linux-Vserver is an operating system-level virtualization solution for GNU/Linux systems with
secure isolation of independent guest servers.
The Linux KVM is virtualization technology that has been integrated into the mainline Linux
kernel (not KVM kernel, but does require PAE support). Runs as a single kernel loadable module,
a Linux kernel running on virtualization-capable hardware is able to act as a hypervisor and
support unmodified Linux and Windows guest operating systems.

10. Conclusion

Trends such as user mobility, server virtualization,
IT-as-a-Service, and the need rapidly to respond to
changing business conditions place significant
demands on the network—demands that today’s
conventional network architectures can’t handle.

Software-Defined Networking provides a new,
dynamic network architecture that transforms
traditional network backbones into rich service-
delivery platforms.

The future of networking will rely more on SDN
and the way its becoming the new norm for

11. 
Open Networking Foundation.
– https://www.opennetworking.org

Open Networking Summit.
– http://opennetsummit.org

ACM SIGCOMM Hot- SDN‐ workshop
– 2012 papers And videos available, 2013 program poste
References

12. THANK YOU