1. Virtualization
Virtualization is the creation of substitutes for real resources – abstraction of real resources
Users/Applications are typically unaware of the substitution (layer of abstraction)
Examples:
computing systems/servers
network storage (e.g. SAN)
network resources (e.g. VLANs, VPNs, HSRP - virtual ip address assignment).

2. System (machine) Virtualization
A virtual machine is a tightly isolated software container that can run its own operating systems and applications as if it were a physical computer.
Was first introduced by IBM in the 60’s
X86 virtualization introduced in the 90’s by VMWare
On a given h/w platform (host) – simulated (virtual) machine environments are created
Benefits:
consolidation to reduce hw costs
workloads consolidation
single consolidated view/management
portability of virtual machines
can be used for testing/training

3. System (machine) Virtualization

4. Hypervisor functionality

5. Virtualization approaches - Hosted
Hosted approach – host O/S runs virtualization software, unmodified guest O/Ss run isolated from each other (separate virtual machines)
Virtualization software is known as Type 2 hypervisor
Additional resources are required for host O/S
Example: Microsoft Virtual PC, VMWare Workstation

6. Hosted Architecture

7. Virtualization approaches - Hypervisor
Hypervisor (bare-metal or type 1) approach – there’s no host O/S. Virtual machines run on top of type 1 hypervisor directly on a hardware platform
No resources are wasted for a Host O/S
Higher virtualization efficiency can be achieved
Example: VMWare ESX Server

8. Hypervisor or Bare-metal Architecture

9. Paravirtualization
Guest O/S is modified to include a call to hypervisor to access h/w resources
Guest O/S is “aware” of running in a virtualized environment
Makes the structure of hypervisor simpler
May make virtual machine more efficient
Can be a problem when Guest O/S can’t be modified (proprietary O/S)

10. Paravirtualization

11. HW Virtualization
Virtualization on x86 machines was difficult to implement, involved a lot of overhead
Starting in 2005 both Intel and AMD introduced processors enabled for virtualization – Intel VT and AMD-V Pacifica
Both employ virtualization extensions to x86 architecture to allow more efficient virtualization

12. X86 architecture – privilege levels

13. Virtualization – ring de-privileging

14. X86 architecture – with virtualization
Paravirtualization
Binary Translation

15. X86 architecture – with HW- assisted virtualization

16. Virtual machine networking
Virtual Embedded Bridge – a software switch as part of the hypervisor

17. Virtual machine networking
External Hardware Switch – switching function performed by an external switch

18. Traditional Infrastructure

19. Virtual Infrastructure