<s>
Desktop	B-Protocol
virtualization	I-Protocol
is	O
a	O
software	O
technology	O
that	O
separates	O
the	O
desktop	O
environment	O
and	O
associated	O
application	B-Application
software	I-Application
from	O
the	O
physical	O
client	O
device	O
that	O
is	O
used	O
to	O
access	O
it	O
.	O
</s>
<s>
Desktop	B-Protocol
virtualization	I-Protocol
can	O
be	O
used	O
in	O
conjunction	O
with	O
application	B-Operating_System
virtualization	I-Operating_System
and	O
user	O
profile	O
management	O
systems	O
,	O
now	O
termed	O
user	B-General_Concept
virtualization	I-General_Concept
,	O
to	O
provide	O
a	O
comprehensive	O
desktop	O
environment	O
management	O
system	O
.	O
</s>
<s>
In	O
addition	O
,	O
this	O
approach	O
supports	O
a	O
more	O
complete	O
desktop	O
disaster	O
recovery	O
strategy	O
as	O
all	O
components	O
are	O
essentially	O
saved	O
in	O
the	O
data	B-Operating_System
center	I-Operating_System
and	O
backed	O
up	O
through	O
traditional	O
redundant	O
maintenance	O
systems	O
.	O
</s>
<s>
Desktop	B-Protocol
virtualization	I-Protocol
implementations	O
are	O
classified	O
based	O
on	O
whether	O
the	O
virtual	O
desktop	O
runs	O
remotely	O
or	O
locally	O
,	O
on	O
whether	O
the	O
access	O
is	O
required	O
to	O
be	O
constant	O
or	O
is	O
designed	O
to	O
be	O
intermittent	O
,	O
and	O
on	O
whether	O
or	O
not	O
the	O
virtual	O
desktop	O
persists	O
between	O
sessions	O
.	O
</s>
<s>
Typically	O
,	O
software	O
products	O
that	O
deliver	O
desktop	B-Protocol
virtualization	I-Protocol
solutions	O
can	O
combine	O
local	O
and	O
remote	O
implementations	O
into	O
a	O
single	O
product	O
to	O
provide	O
the	O
most	O
appropriate	O
support	O
specific	O
to	O
requirements	O
.	O
</s>
<s>
The	O
enabling	O
layer	O
—	O
usually	O
application	B-Application
software	I-Application
—	O
is	O
called	O
a	O
hypervisor	B-Operating_System
.	O
</s>
<s>
Remote	O
desktop	B-Protocol
virtualization	I-Protocol
implementations	O
operate	O
in	O
a	O
client/server	B-Operating_System
computing	I-Operating_System
environment	O
.	O
</s>
<s>
All	O
applications	O
and	O
data	O
used	O
remain	O
on	O
the	O
remote	O
system	O
with	O
only	O
display	O
,	O
keyboard	O
,	O
and	O
mouse	O
information	O
communicated	O
with	O
the	O
local	O
client	O
device	O
,	O
which	O
may	O
be	O
a	O
conventional	O
PC/laptop	O
,	O
a	O
thin	B-Device
client	I-Device
device	O
,	O
a	O
tablet	B-Device
,	O
or	O
even	O
a	O
smartphone	B-Application
.	O
</s>
<s>
A	O
common	O
implementation	O
of	O
this	O
approach	O
involves	O
hosting	O
multiple	O
desktop	O
operating	O
system	O
instances	O
on	O
a	O
server	O
hardware	O
platform	O
running	O
a	O
hypervisor	B-Operating_System
.	O
</s>
<s>
Its	O
latest	O
iteration	O
is	O
generally	O
referred	O
to	O
as	O
Virtual	B-Protocol
Desktop	I-Protocol
Infrastructure	I-Protocol
,	O
or	O
"	O
VDI	O
"	O
(	O
note	O
that	O
"	O
VDI	O
"	O
is	O
often	O
used	O
incorrectly	O
to	O
refer	O
to	O
any	O
desktop	B-Protocol
virtualization	I-Protocol
implementation	O
)	O
.	O
</s>
<s>
Remote	O
desktop	B-Protocol
virtualization	I-Protocol
is	O
frequently	O
used	O
in	O
the	O
following	O
scenarios	O
:	O
</s>
<s>
in	O
environments	O
where	O
remote	O
access	O
and	O
data	O
security	O
requirements	O
create	O
conflicting	O
requirements	O
that	O
can	O
be	O
addressed	O
by	O
retaining	O
all	O
(	O
application	O
)	O
data	O
within	O
the	O
data	B-Operating_System
center	I-Operating_System
–	O
with	O
only	O
display	O
,	O
keyboard	O
,	O
and	O
mouse	O
information	O
communicated	O
with	O
the	O
remote	O
client	O
.	O
</s>
<s>
It	O
is	O
also	O
used	O
as	O
a	O
means	O
of	O
providing	O
access	O
to	O
Windows	O
applications	O
on	O
non-Windows	O
endpoints	O
(	O
including	O
tablets	B-Device
,	O
smartphones	B-Application
,	O
and	O
non-Windows-based	O
desktop	O
PCs	O
and	O
laptops	O
)	O
.	O
</s>
<s>
Remote	O
desktop	B-Protocol
virtualization	I-Protocol
can	O
also	O
provide	O
a	O
means	O
of	O
resource	O
sharing	O
,	O
to	O
distribute	O
low-cost	O
desktop	O
computing	O
services	O
in	O
environments	O
where	O
providing	O
every	O
user	O
with	O
a	O
dedicated	O
desktop	O
PC	O
is	O
either	O
too	O
expensive	O
or	O
otherwise	O
unnecessary	O
.	O
</s>
<s>
Remote	O
desktop	B-Application
software	I-Application
allows	O
a	O
user	O
to	O
access	O
applications	O
and	O
data	O
on	O
a	O
remote	B-Protocol
computer	I-Protocol
over	O
a	O
network	O
using	O
a	O
remote-display	O
protocol	O
.	O
</s>
<s>
Both	O
session	O
collections	O
and	O
virtual	B-Architecture
machines	I-Architecture
support	O
full	O
desktop	O
based	O
sessions	O
and	O
remote	O
application	O
deployment	O
.	O
</s>
<s>
Together	O
,	O
these	O
factors	O
can	O
combine	O
to	O
make	O
remote	O
desktop-based	O
remote	O
desktop	B-Protocol
virtualization	I-Protocol
more	O
attractive	O
than	O
VDI	O
.	O
</s>
<s>
Application	B-Operating_System
virtualization	I-Operating_System
improves	O
delivery	O
and	O
compatibility	O
of	O
applications	O
by	O
encapsulating	O
them	O
from	O
the	O
underlying	O
operating	O
system	O
on	O
which	O
they	O
are	O
executed	O
.	O
</s>
<s>
Instead	O
,	O
a	O
hypervisor	B-Operating_System
layer	O
intercepts	O
the	O
application	O
,	O
which	O
at	O
runtime	O
acts	O
as	O
if	O
it	O
is	O
interfacing	O
with	O
the	O
original	O
operating	O
system	O
and	O
all	O
the	O
resources	O
managed	O
by	O
it	O
when	O
in	O
reality	O
it	O
is	O
not	O
.	O
</s>
<s>
User	B-General_Concept
virtualization	I-General_Concept
separates	O
all	O
of	O
the	O
software	O
aspects	O
that	O
define	O
a	O
user	O
’s	O
personality	O
on	O
a	O
device	O
from	O
the	O
operating	O
system	O
and	O
applications	O
to	O
be	O
managed	O
independently	O
and	O
applied	O
to	O
a	O
desktop	O
as	O
needed	O
without	O
the	O
need	O
for	O
scripting	O
,	O
group	O
policies	O
,	O
or	O
use	O
of	O
roaming	O
profiles	O
.	O
</s>
<s>
The	O
term	O
"	O
user	B-General_Concept
virtualization	I-General_Concept
"	O
sounds	O
misleading	O
;	O
this	O
technology	O
is	O
not	O
limited	O
to	O
virtual	O
desktops	O
.	O
</s>
<s>
User	B-General_Concept
virtualization	I-General_Concept
can	O
be	O
used	O
regardless	O
of	O
platform	O
–	O
physical	O
,	O
virtual	O
,	O
cloud	O
,	O
etc	O
.	O
</s>
<s>
The	O
major	O
desktop	B-Protocol
virtualization	I-Protocol
platform	O
vendors	O
,	O
Citrix	O
,	O
Microsoft	O
and	O
VMware	O
,	O
all	O
offer	O
a	O
form	O
of	O
basic	O
user	B-General_Concept
virtualization	I-General_Concept
in	O
their	O
platforms	O
.	O
</s>
<s>
Desktop	O
layering	O
is	O
a	O
method	O
of	O
desktop	B-Protocol
virtualization	I-Protocol
that	O
divides	O
a	O
disk	O
image	O
into	O
logical	O
parts	O
to	O
be	O
managed	O
individually	O
.	O
</s>
<s>
Layering	O
can	O
be	O
applied	O
to	O
local	O
physical	O
disk	O
images	O
,	O
client-based	O
virtual	B-Architecture
machines	I-Architecture
,	O
or	O
host-based	O
desktops	O
.	O
</s>
<s>
Remote	O
desktop	B-Protocol
virtualization	I-Protocol
can	O
also	O
be	O
provided	O
via	O
cloud	B-Architecture
computing	I-Architecture
similar	O
to	O
that	O
provided	O
using	O
a	O
software	B-Architecture
as	I-Architecture
a	I-Architecture
service	I-Architecture
model	O
.	O
</s>
<s>
This	O
approach	O
is	O
usually	O
referred	O
to	O
as	O
cloud-hosted	B-Architecture
virtual	O
desktops	O
.	O
</s>
<s>
Cloud-hosted	B-Architecture
virtual	O
desktops	O
are	O
divided	O
into	O
two	O
technologies	O
:	O
</s>
<s>
Desktop	B-Protocol
as	I-Protocol
a	I-Protocol
service	I-Protocol
(	O
DaaS	O
)	O
,	O
which	O
provides	O
a	O
higher	O
level	O
of	O
automation	O
and	O
real	O
multi-tenancy	O
,	O
reducing	O
the	O
cost	O
of	O
the	O
technology	O
.	O
</s>
<s>
The	O
DaaS	O
provider	O
typically	O
takes	O
full	O
responsibility	O
for	O
hosting	O
and	O
maintaining	O
the	O
computer	O
,	O
storage	O
,	O
and	O
access	O
infrastructure	O
,	O
as	O
well	O
as	O
applications	O
and	O
application	B-Application
software	I-Application
licenses	O
needed	O
to	O
provide	O
the	O
desktop	O
service	O
in	O
return	O
for	O
a	O
fixed	O
monthly	O
fee	O
.	O
</s>
<s>
Cloud-hosted	B-Architecture
virtual	O
desktops	O
can	O
be	O
implemented	O
using	O
both	O
VDI	O
and	O
Remote	O
Desktop	O
Services-based	O
systems	O
and	O
can	O
be	O
provided	O
through	O
the	O
public	O
cloud	O
,	O
private	O
cloud	O
infrastructure	O
,	O
and	O
hybrid	O
cloud	O
platforms	O
.	O
</s>
<s>
Local	O
desktop	B-Protocol
virtualization	I-Protocol
implementations	O
run	O
the	O
desktop	O
environment	O
on	O
the	O
client	O
device	O
using	O
hardware	B-General_Concept
virtualization	I-General_Concept
or	O
emulation	B-Application
.	O
</s>
<s>
For	O
hardware	B-General_Concept
virtualization	I-General_Concept
,	O
depending	O
on	O
the	O
implementation	O
both	O
Type	O
I	O
and	O
Type	O
II	O
hypervisors	B-Operating_System
may	O
be	O
used	O
.	O
</s>
<s>
Local	O
desktop	B-Protocol
virtualization	I-Protocol
is	O
well	O
suited	O
for	O
environments	O
where	O
continuous	O
network	O
connectivity	O
cannot	O
be	O
assumed	O
and	O
where	O
application	O
resource	O
requirements	O
can	O
be	O
better	O
met	O
by	O
using	O
local	O
system	O
resources	O
.	O
</s>
<s>
However	O
,	O
local	O
desktop	B-Protocol
virtualization	I-Protocol
implementations	O
do	O
not	O
always	O
allow	O
applications	O
developed	O
for	O
one	O
system	O
architecture	O
to	O
run	O
on	O
another	O
.	O
</s>
<s>
For	O
example	O
,	O
it	O
is	O
possible	O
to	O
use	O
local	O
desktop	B-Protocol
virtualization	I-Protocol
to	O
run	O
Windows	O
7	O
on	O
top	O
of	O
OS	B-Operating_System
X	I-Operating_System
on	O
an	O
Intel-based	B-Device
Apple	I-Device
Mac	I-Device
,	O
using	O
a	O
hypervisor	B-Operating_System
,	O
as	O
both	O
use	O
the	O
same	O
x86	B-Operating_System
architecture	I-Operating_System
.	O
</s>
