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In
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[
2
]
.
B
ec
au
s
e
th
e
s
e
t
h
r
ee
s
er
v
ice
r
elea
s
e
m
o
d
els
o
f
f
e
r
d
iv
er
s
e
s
tag
e
s
o
f
s
er
v
ice,
t
h
e
s
a
f
et
y
le
v
el
t
h
at
C
SP
p
r
o
m
i
s
e
to
co
n
s
u
m
er
s
s
h
o
u
ld
also
b
e
d
is
s
i
m
ilar
.
C
S
A
b
eliev
es
th
a
t
C
SP
s
h
o
u
ld
tak
e
o
n
th
e
g
r
ea
test
q
u
an
tit
y
o
f
s
ec
u
r
it
y
ac
co
u
n
tab
ilit
y
in
Saa
S
m
o
d
el
a
n
d
th
e
least
a
m
o
u
n
t
o
f
s
ec
u
r
it
y
d
ep
en
d
ab
ili
t
y
i
n
I
aa
S
m
o
d
el,
w
h
ile
i
n
P
aa
S
m
o
d
el,
s
ec
u
r
it
y
ac
co
u
n
tab
il
it
y
m
u
s
t
b
e
ca
r
ef
u
ll
y
le
v
er
ag
ed
b
y
t
h
e
C
SP
an
d
cu
s
to
m
er
s
[
2
]
.
Vir
tu
a
lizatio
n
h
as
p
r
o
f
o
u
n
d
l
y
c
h
an
g
ed
th
e
i
n
f
o
r
m
atio
n
tech
n
o
lo
g
y
(
I
T
)
in
d
u
s
tr
y
i
n
d
if
f
er
e
n
t
ar
ea
s
s
u
c
h
as
n
et
wo
r
k
,
o
p
er
atin
g
s
y
s
te
m
s
,
a
p
p
licatio
n
s
o
r
s
to
r
ag
e.
Vir
tu
aliza
t
io
n
is
a
s
u
b
j
ec
t
th
at
n
o
t
o
n
l
y
I
T
p
eo
p
le
co
n
ce
r
n
n
o
w
.
I
t
h
as
g
ai
n
ed
s
p
ac
e
o
n
th
e
ad
m
i
n
i
s
tr
ato
r
s
an
d
d
ir
ec
to
r
s
v
o
ca
b
u
l
ar
y
.
C
o
m
p
a
n
ies
h
a
v
e
ap
p
r
eh
en
d
ed
th
a
t
m
o
s
t
o
f
t
h
eir
s
y
s
te
m
s
w
er
e
o
p
er
ates
at
s
h
ar
e
o
f
1
0
p
er
ce
n
t
o
r
less
o
f
u
tili
za
tio
n
,
y
et
t
h
ese
s
y
s
te
m
s
co
n
ti
n
u
e
to
r
eq
u
ir
e
s
p
ac
e,
p
o
w
er
a
n
d
co
o
lin
g
s
y
s
te
m
a
s
a
n
y
o
th
er
m
ac
h
i
n
e.
T
u
m
b
lin
g
t
h
ese
n
ec
es
s
itie
s
w
o
u
ld
h
a
v
e
a
s
tr
aig
h
t
cr
as
h
i
n
d
r
o
p
p
i
n
g
th
e
I
n
f
o
r
m
atio
n
T
ec
h
n
o
lo
g
y
b
u
d
g
et
a
n
d
at
m
o
s
p
h
er
e
ca
r
es
as
t
h
e
ca
r
b
o
n
f
o
o
t
s
tep
.
Vi
r
tu
al
izatio
n
tech
n
o
lo
g
y
w
a
s
t
h
e
s
o
l
u
tio
n
f
o
u
n
d
b
y
m
an
y
co
m
p
an
ie
s
,
m
o
v
in
g
th
i
s
tech
n
o
lo
g
y
i
n
to
th
e
m
ai
n
s
tr
ea
m
.
A
cc
o
r
d
in
g
to
a
r
ec
en
t
I
DC
s
u
r
v
e
y
[
2
]
,
co
m
p
an
ie
s
t
h
at
h
a
v
e
d
ep
lo
y
ed
v
ir
t
u
aliza
tio
n
co
u
ld
s
ee
a
r
etu
r
n
o
f
i
n
v
est
m
e
n
t o
f
4
7
2
p
er
ce
n
t i
n
les
s
t
h
a
n
a
y
ea
r
.
T
h
e
in
cr
ea
s
ed
u
ti
lizatio
n
an
d
co
n
s
o
lid
atio
n
o
f
x
8
6
ar
ch
itect
u
r
es
h
ad
s
ig
n
i
f
ica
n
t
j
o
b
f
o
r
th
is
al
s
o
.
Ma
n
y
co
m
p
a
n
ies
u
s
e
t
h
is
ar
c
h
itect
u
r
e
s
in
ce
it
h
as le
s
s
er
co
s
t
co
n
tr
asted
w
it
h
o
th
er
s
in
th
e
m
ar
k
e
tp
lace
.
T
h
o
u
g
h
,
t
h
i
s
s
tr
u
ct
u
r
e
h
ad
h
is
to
r
icall
y
h
ar
d
w
a
r
e
s
u
p
p
o
r
t
is
s
u
es
f
o
r
v
ir
t
u
aliza
tio
n
w
h
ic
h
s
ig
n
i
f
ican
t
d
e
g
r
ad
e
th
e
p
er
f
o
r
m
a
n
ce
o
f
th
e
v
ir
t
u
al
m
ac
h
in
e
w
eig
h
a
g
ai
n
s
t
w
i
th
th
e
s
a
m
e
s
tr
u
ct
u
r
e
o
p
er
ates
o
n
a
p
h
y
s
ical
h
o
s
t.
I
n
o
r
d
er
to
s
o
lv
e
th
i
s
is
s
u
e,
A
M
D
an
d
I
n
tel
e
x
ec
u
ted
ar
ch
i
tect
u
r
al
ad
d
itio
n
s
to
d
ir
ec
tl
y
s
u
p
p
o
r
t
v
ir
tu
aliza
tio
n
i
n
h
ar
d
w
ar
e.
T
h
is
co
n
q
u
er
s
t
h
e
tr
ad
itio
n
al
v
ir
t
u
aliza
tio
n
r
estrictio
n
s
o
f
t
h
e
x
8
6
ar
ch
i
tectu
r
e,
i
m
p
r
o
v
i
n
g
s
ig
n
i
f
ica
n
t
ch
ar
ac
ter
is
tics
li
k
e
p
er
f
o
r
m
a
n
ce
an
d
s
ca
lab
ilit
y
cr
ea
tin
g
x
8
6
s
er
v
er
v
ir
t
u
aliza
tio
n
a
k
e
y
s
to
n
e
o
f
m
o
s
t
I
T
co
n
s
o
li
d
atio
n
p
r
o
jects.
T
h
e
in
cr
ea
s
i
n
g
i
n
v
est
m
en
t
an
d
i
m
p
le
m
e
n
tat
io
n
o
f
v
ir
t
u
aliza
tio
n
is
co
m
p
ar
ab
le
to
th
e
i
m
p
le
m
e
n
t
atio
n
o
f
i
n
ter
n
et
i
n
co
m
p
a
n
ie
s
at
th
e
e
n
d
o
f
th
e
las
t
d
ec
ad
e.
Ho
w
ev
er
,
i
n
th
e
s
a
m
e
w
a
y
,
s
ec
u
r
it
y
w
a
s
n
o
t
t
h
e
to
p
p
r
io
r
ity
,
E
v
e
n
th
o
u
g
h
I
n
f
o
r
m
a
tio
n
T
ec
h
n
o
lo
g
y
ad
m
in
is
tr
ato
r
s
ar
e
n
o
w
m
o
r
e
r
atio
n
al
to
t
h
is
t
h
e
m
e.
T
h
e
th
r
ea
t
o
f
t
h
is
la
test
tec
h
n
o
lo
g
y
ar
e
a
litt
le
ar
g
u
ed
al
m
o
s
t
o
n
l
y
a
t
s
ec
u
r
it
y
ac
tio
n
s
s
u
c
h
as
B
lack
Hat
a
n
d
it
co
n
tin
u
es
to
b
e
o
u
t
o
f
th
e
f
o
cu
s
o
f
m
an
y
all
u
s
io
n
an
d
ad
v
is
o
r
co
m
p
a
n
ies
t
h
at
e
m
p
lo
y
t
h
is
ex
p
er
ti
s
e.
Vir
tu
a
lizatio
n
h
a
s
b
ee
n
p
r
esen
ted
t
o
co
m
p
an
ie
s
as
an
o
u
t
-
of
-
th
e
-
b
o
x
an
s
w
er
th
at
co
m
p
a
n
ies
d
o
n
o
t
h
av
e
to
w
o
r
r
y
ab
o
u
t,
as
i
f
it
w
a
s
p
h
y
s
ical
m
ac
h
in
e
s
w
ith
t
h
e
ad
v
a
n
tag
e
s
th
at
th
e
h
ar
d
w
ar
e
v
ir
tu
a
lized
d
o
es
n
o
t
“
cr
ac
k
”
a
s
th
e
p
h
y
s
ica
l
in
f
r
astr
u
ct
u
r
e.
T
h
er
e
is
s
o
m
e
m
y
t
h
o
lo
g
y
to
s
p
l
it
w
h
e
n
co
n
d
en
s
ate
ab
o
u
t
v
ir
t
u
aliza
tio
n
s
ec
u
r
it
y
an
d
t
h
is
m
y
t
h
o
lo
g
y
h
ap
p
en
b
ec
au
s
e,
as
o
th
er
m
y
th
s
,
th
er
e
i
s
n
o
t
m
u
c
h
in
f
o
r
m
atio
n
ab
o
u
t
it.
So
m
e
p
e
o
p
le
ass
u
m
e
t
h
at
h
a
v
i
n
g
,
f
o
r
in
s
ta
n
ce
,
4
v
ir
tu
al
m
ac
h
i
n
es
o
p
er
ate
s
o
n
a
p
h
y
s
ical
m
ac
h
in
e
i
s
t
h
e
s
a
m
e
as
h
av
i
n
g
4
p
h
y
s
ical
m
ac
h
i
n
e
s
an
d
s
o
th
e
co
n
ce
r
n
s
s
h
o
u
ld
b
e
th
e
s
a
m
e
(
e.
g
.
o
n
l
y
i
n
s
tal
l
p
atch
es
o
n
th
e
o
p
er
atin
g
s
y
s
t
e
m
i
n
s
id
e
t
h
e
v
ir
t
u
al
m
ac
h
in
e)
.
P
er
h
ap
s
th
is
m
y
t
h
e
x
is
t
s
b
ec
au
s
e
t
h
er
e
is
a
co
m
m
o
n
s
en
s
e
th
at
h
y
p
er
v
is
o
r
s
ar
e
im
p
en
e
tr
ab
le,
w
h
ich
i
s
f
alse
as
w
e
ar
e
g
o
in
g
to
s
ee
later
in
th
is
p
ap
er
.
So
m
e
I
T
d
ir
ec
to
r
s
ar
e
n
o
t a
w
a
r
e
o
f
th
e
s
ec
u
r
it
y
in
te
n
s
it
y
w
h
er
ea
s
u
s
in
g
v
ir
tu
a
lizatio
n
.
Fo
r
ex
a
m
p
le,
b
y
m
ea
n
s
o
f
v
ir
t
u
aliza
tio
n
it
is
f
ea
s
ib
le
to
p
au
s
e
o
r
tak
e
a
p
ictu
r
e
o
f
a
v
ir
tu
al
m
ac
h
in
e
t
h
at
h
as
r
ea
s
o
n
ab
le
in
f
o
r
m
atio
n
as
cr
y
p
to
g
r
ap
h
ic
k
e
y
s
o
r
p
ass
w
o
r
d
in
m
e
m
o
r
y
an
d
m
o
s
t
co
m
p
a
n
ie
s
d
o
n
o
t
lo
o
k
to
t
h
ese
s
n
ap
s
h
o
ts
a
s
cr
itica
l
ass
ets
as
th
e
r
u
n
n
i
n
g
v
ir
tu
a
l
m
ac
h
in
e
s
.
T
h
is
p
ap
er
p
r
esen
t
s
a
s
t
u
d
y
ab
o
u
t
v
ir
tu
al
izatio
n
,
f
o
cu
s
in
g
i
n
s
ec
u
r
i
t
y
p
r
o
b
lem
s
as
t
h
e
o
n
es
d
escr
ib
ed
o
n
th
e
p
r
ev
io
u
s
p
ar
ag
r
ap
h
.
I
t
co
v
er
s
b
o
th
s
er
v
er
an
d
d
es
k
to
p
en
v
ir
o
n
m
e
n
t
s
an
d
v
ir
t
u
aliza
tio
n
s
o
f
t
w
ar
e.
R
eg
ar
d
in
g
s
er
v
er
s
,
w
e
h
av
e
co
n
d
u
cted
a
v
u
ln
er
ab
ilit
y
s
tu
d
y
,
co
m
p
ar
i
n
g
t
w
o
v
ir
tu
a
lizatio
n
s
o
l
u
tio
n
s
,
w
h
ile
f
o
r
th
e
d
es
k
to
p
s
w
e
h
av
e
m
ad
e
a
s
tu
d
y
ab
o
u
t
h
o
w
v
ir
tu
aliza
tio
n
ca
n
b
e
u
s
ed
to
i
m
p
r
o
v
e
s
ec
u
r
it
y
f
o
r
o
n
li
n
e
b
an
k
i
n
g
an
d
e
-
co
m
m
er
ce
.
2.
E
XI
ST
I
N
G
SYS
T
E
M
AND
RE
L
AT
E
D
WO
RK
2
.
1
.
Virt
ua
liza
t
io
n
Def
i
n
i
n
g
v
ir
t
u
aliza
tio
n
i
s
n
o
t
an
ea
s
y
ta
s
k
b
ec
au
s
e
as
w
e
will
s
ee
la
ter
,
th
er
e
ar
e
d
i
f
f
er
e
n
t
t
y
p
es
o
f
v
ir
tu
a
lizatio
n
a
n
d
a
d
ef
in
itio
n
th
at
w
o
u
ld
b
e
ad
eq
u
ate
f
o
r
all
is
n
o
t
ea
s
y
to
ac
h
ie
v
e.
Si
n
g
h
[
1
3
]
d
escr
ib
es
v
ir
tu
a
lizatio
n
as
“f
r
a
m
e
w
o
r
k
o
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m
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w
o
r
th
o
f
s
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v
ice,
an
d
m
a
n
y
o
t
h
er
s
”.
W
h
ile,
th
i
s
d
escr
ip
tio
n
leav
es
o
u
t
b
ag
s
as
v
ir
tu
aliza
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t
h
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et
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licatio
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t
u
aliza
tio
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o
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s
to
r
ag
e
v
ir
t
u
aliza
tio
n
.
Ki
y
an
cl
ar
[
1
4
]
d
escr
ib
es
v
ir
tu
al
izatio
n
as
“
t
h
e
co
n
s
is
ten
t
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t
w
ar
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Evaluation Warning : The document was created with Spire.PDF for Python.
I
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1
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1328
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co
r
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I
ad
ap
ted
Sin
g
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s
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ef
i
n
itio
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s
a
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g
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h
at:
De
f
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it
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.
Vir
t
u
aliz
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i
s
as
a
f
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a
m
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d
iv
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o
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ev
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f
r
o
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t
h
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ex
ec
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en
t,
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v
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e
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r
alit
y
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s
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g
o
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o
r
m
o
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e
tec
h
n
iq
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es
s
u
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h
as ti
m
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h
ar
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g
,
e
m
u
la
tio
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p
ar
titi
o
n
i
n
g
.
2
.
2
.
CP
U
Virt
ua
liza
t
io
n
T
h
e
x
8
6
ar
ch
itectu
r
e
is
t
h
e
m
aj
o
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ity
u
s
ed
C
P
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d
esig
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in
en
ter
p
r
is
e
d
ata
-
ce
n
ter
s
t
o
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ay
.
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h
e
v
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tu
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lizatio
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ca
n
ta
k
e
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en
e
f
it
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tel
8
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ip
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o
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Feb
r
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1
9
8
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as
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ir
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o
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x
8
6
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a
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il
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ai
n
m
eth
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d
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ad
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ess
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e
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y
:
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m
o
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e
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p
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o
tecte
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m
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e.
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a
ter
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in
1
9
8
5
,
w
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th
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e
8
0
3
8
6
ch
ip
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et,
a
t
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ir
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ca
lled
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o
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also
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lled
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V8
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m
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l
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d
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ec
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it
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h
ig
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32
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atin
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te
m
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r
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tecte
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d
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ir
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e
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t
o
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th
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0
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6
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m
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y
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r
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o
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er
to
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u
p
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ltit
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c
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as
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ar
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p
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n
d
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m
e
n
ti
n
g
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s
o
r
.
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d
m
o
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e
in
th
e
x
8
6
f
am
il
y
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s
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s
4
p
r
iv
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n
u
m
b
er
ed
f
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o
m
0
to
3
.
So
m
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m
e
s
t
h
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le
v
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esig
n
ated
as
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a
n
d
th
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ter
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m
e
s
f
r
o
m
t
h
e
MU
L
T
I
C
S
s
y
s
te
m
[
1
7
]
,
in
w
h
ic
h
p
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iv
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e
le
v
els
w
er
e
ill
u
s
tr
ated
as
a
s
et
o
f
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tr
ic
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s
.
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e
ar
e
ab
o
u
t to
e
m
p
l
o
y
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e
w
o
r
d
“
r
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as
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d
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s
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p
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e
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to
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w
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ith
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in
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Fi
g
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2
,
R
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R
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3
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o
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d
h
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s
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s
.
Fig
u
r
e
2
.
P
r
iv
ileg
e
r
in
g
s
o
f
t
h
e
x
8
6
ar
ch
itectu
r
e.
Hi
g
h
p
r
iv
ile
g
e:0
; L
o
w
p
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leg
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:
3
T
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p
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o
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x
8
6
p
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s
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it
h
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n
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tr
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ac
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ess
,
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h
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en
ab
les
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e
ex
ec
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tio
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in
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d
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d
m
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o
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,
w
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s
s
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Ho
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f
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is
r
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p
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m
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m
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(
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.
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f
o
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t
u
alize
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e
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th
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o
f
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r
r
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2
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o
r
x
8
6
ar
ch
itec
tu
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es.
Ho
w
e
v
er
,
t
h
e
f
u
r
t
h
er
it
g
o
es
f
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m
th
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r
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r
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g
0
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t
h
e
m
o
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e
d
is
ta
n
t
is
f
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m
e
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u
ti
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g
d
ir
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t
h
ar
d
w
ar
e
o
p
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atio
n
s
,
r
esu
lti
n
g
i
n
a
lo
s
s
o
f
p
er
f
o
r
m
a
n
ce
an
d
i
n
d
ep
en
d
en
ce
.
Vir
tu
aliza
tio
n
m
o
v
e
s
r
in
g
0
u
p
o
n
e
lev
el
in
t
h
e
p
r
iv
ile
g
e
r
in
g
s
m
o
d
el
a
n
d
p
lace
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th
e
v
ir
tu
al
m
ac
h
i
n
e
m
o
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ito
r
i
n
t
h
e
n
e
x
t
h
i
g
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er
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r
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v
ile
g
e
r
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n
g
.
T
h
is
w
i
ll
b
e
t
h
e
r
i
n
g
0
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d
it
is
u
p
o
n
th
is
th
e
g
u
e
s
t
o
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g
s
y
s
te
m
s
r
u
n
s
,
w
h
ile
t
h
e
Vir
t
u
al
Ma
c
h
in
e
Mo
n
ito
r
co
n
tr
o
ls
t
h
e
i
n
ter
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tio
n
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h
t
h
e
u
n
d
er
l
y
in
g
h
ar
d
w
ar
e
p
latf
o
r
m
.
VM
Ms c
an
b
e
class
if
ied
in
t
wo
ty
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:
a.
T
y
p
e
1
:
T
h
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also
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l
l
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ati
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e
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er
v
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w
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ates
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o
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e
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t
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d
w
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e
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al
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(
Fig
u
r
e
3
(
a)
)
.
A
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atin
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h
y
p
er
v
i
s
o
r
,
allo
w
in
g
f
o
r
tr
u
e
is
o
lat
io
n
o
f
ea
c
h
v
ir
t
u
al
m
ac
h
i
n
e.
T
h
is
is
t
h
e
cla
s
s
ic
VM
ar
c
h
itect
u
r
e.
An
ex
a
m
p
le
o
f
t
h
is
i
m
p
le
m
e
n
t
atio
n
is
t
h
e
VM
w
ar
e
E
SX Ser
v
er
an
d
Xen
.
Evaluation Warning : The document was created with Spire.PDF for Python.
I
J
E
C
E
I
SS
N:
2088
-
8708
A
S
u
r
ve
y
o
n
S
ec
u
r
ity
A
s
p
ec
ts
o
f S
erver V
ir
tu
a
liz
a
tio
n
in
C
lo
u
d
C
o
mp
u
tin
g
(
O
S
r
i Na
g
esh
)
1329
b.
T
y
p
e
2
:
T
h
is
t
y
p
e
is
al
s
o
ca
lled
h
o
s
ted
VM
M
b
ec
au
s
e
t
h
e
h
y
p
er
v
is
o
r
s
o
f
t
w
ar
e
r
u
n
s
w
it
h
in
a
n
o
r
m
al
h
o
s
t
o
p
er
atin
g
s
y
s
te
m
p
r
ev
io
u
s
l
y
m
o
u
n
te
d,
u
s
u
all
y
i
n
r
i
n
g
3
(
Fig
u
r
e
3
(
b
)
)
.
T
h
is
t
y
p
e
o
f
V
MM
h
a
s
a
lo
w
er
p
er
f
o
r
m
a
n
ce
th
a
n
th
e
o
t
h
er
t
y
p
e
b
ec
au
s
e
f
ac
to
r
s
as
ca
lls
to
th
e
h
ar
d
w
ar
e
m
u
s
t
tr
av
er
s
e
m
an
y
d
iv
er
s
e
la
y
er
s
b
ef
o
r
e
th
e
o
p
er
atio
n
s
ar
e
r
etu
r
n
ed
to
th
e
g
u
es
t
o
p
er
atin
g
s
y
s
te
m
.
E
x
a
m
p
le
s
o
f
t
h
is
i
m
p
l
e
m
en
tatio
n
in
c
lu
d
e
VM
w
ar
e
W
o
r
k
s
ta
tio
n
,
S
u
n
V
i
r
tu
al
B
o
x
an
d
P
ar
allels W
o
r
k
s
tatio
n
s
.
(
a)
(
b
)
Fig
u
r
e
3
.
(
a)
T
y
p
e
1
H
y
p
er
v
is
o
r
/VMM
,
(
b
)
T
y
p
e
2
Hy
p
er
v
i
s
o
r
/VMM
2
.
3
.
M
em
o
ry
Virt
ua
liza
t
io
n
Stan
d
ar
d
o
p
er
atin
g
s
y
s
te
m
e
m
p
lo
y
s
p
a
g
e
-
tab
le
s
to
co
n
v
er
ts
ad
d
r
ess
es
w
h
ic
h
ar
e
v
ir
tu
a
l
an
d
co
n
v
er
ted
i
n
to
ad
d
r
ess
es
w
h
ic
h
p
h
y
s
ical
d
ata
i
s
p
r
o
v
id
ed
.
Vir
tu
al
m
ac
h
i
n
es
g
i
v
es
r
aise
t
o
n
e
w
o
b
s
er
v
at
io
n
s
ab
o
u
t
m
e
m
o
r
y
v
ir
t
u
aliza
t
io
n
s
in
ce
m
e
m
o
r
y
i
s
g
o
in
g
to
b
e
s
h
ar
ed
alth
o
u
g
h
is
o
latio
n
as
to
b
e
g
u
ar
an
teed
.
W
e
ca
n
co
n
s
id
e
r
th
r
ee
cla
s
s
es o
f
a
d
d
r
ess
es o
n
a
v
ir
t
u
alize
d
s
y
s
te
m
:
a.
Vir
tu
al
ad
d
r
ess
es,
w
h
ic
h
ar
e
th
e
s
a
m
e
as t
h
e
o
n
es
u
s
ed
b
y
a
co
n
v
e
n
tio
n
al
O
S
•
G
u
est p
h
y
s
ical
ad
d
r
ess
b.
Ma
ch
i
n
e
m
e
m
o
r
y
Op
er
atin
g
s
y
s
te
m
s
w
h
ic
h
ar
e
g
u
e
s
ts
w
i
ll
m
ai
n
tain
p
a
g
e
tab
l
es
th
at
tr
a
n
s
la
te
f
r
o
m
v
ir
t
u
al
a
d
d
r
ess
es
to
p
s
eu
d
o
-
p
h
y
s
ica
l a
d
d
r
ess
es,
an
d
h
y
p
er
v
is
o
r
p
r
eser
v
e
s
i
n
d
i
v
id
u
al
s
h
ad
o
w
p
a
g
e
tab
le
s
t
h
at
tr
an
s
late
f
r
o
m
v
ir
t
u
a
l
ad
d
r
ess
es to
d
ev
ice
o
r
s
y
s
te
m
ad
d
r
ess
es [
2
4
]
.
T
h
e
cu
r
r
en
t
x
8
6
C
P
Us
h
o
ld
m
e
m
o
r
y
i
n
h
ar
d
w
ar
e.
T
r
an
s
latio
n
f
r
o
m
v
ir
tu
al
to
p
h
y
s
i
ca
l
ad
d
r
ess
es
is
p
er
f
o
r
m
ed
b
y
t
h
e
m
e
m
o
r
y
m
an
ag
e
m
e
n
t
u
n
i
t
an
d
t
h
e
m
o
s
t
u
s
ed
p
ar
ts
o
f
t
h
e
p
ag
e
tab
le
s
ar
e
ca
ch
ed
in
t
h
e
tr
an
s
latio
n
lo
o
k
a
s
id
e
b
u
f
f
er
(
T
L
B
)
.
Gu
est
OS
s
ee
s
p
a
g
e
t
ab
les,
w
h
ic
h
r
u
n
o
n
a
n
e
m
u
l
ated
MM
U.
T
h
ese
tab
les
p
r
o
v
id
e
th
e
g
u
est
OS
with
t
h
e
f
al
s
e
i
m
p
r
e
s
s
io
n
th
a
t
it
ca
n
i
n
ter
p
r
et
th
e
v
ir
t
u
al
g
u
est
OS
ad
d
r
ess
es
in
t
o
p
h
y
s
ical
ad
d
r
ess
es
o
f
th
e
m
ac
h
in
e,
b
u
t
it i
s
t
h
e
h
y
p
er
v
is
o
r
t
h
at
d
ea
ls
w
it
h
i
t.
T
h
e
r
ea
l p
ag
e
tab
le
is
th
e
s
h
ad
o
w
p
ag
e
tab
le
u
s
ed
to
tr
an
s
la
te
th
e
v
ir
tu
al
ad
d
r
ess
e
s
o
f
th
e
g
u
es
t O
S i
n
to
t
h
e
r
ea
l p
h
y
s
ical
p
ag
es.
T
h
e
class
ic
i
m
p
le
m
e
n
tatio
n
o
f
h
y
p
er
v
i
s
o
r
s
m
a
in
ta
in
s
a
s
h
a
d
o
w
p
ag
e
tab
le,
w
h
ich
al
lo
w
s
to
co
n
tr
o
l
w
h
at
p
ag
e
o
f
t
h
e
m
ac
h
in
e
’
s
m
e
m
o
r
y
is
a
v
ailab
le
to
a
v
ir
t
u
al
m
ac
h
i
n
e.
J
u
s
t
l
ik
e
i
n
a
tr
ad
itio
n
al
o
p
er
atin
g
s
y
s
te
m
’
s
v
ir
t
u
al
m
e
m
o
r
y
s
u
b
s
y
s
te
m
,
w
h
e
n
t
h
e
m
e
m
o
r
y
allo
ca
ted
to
VM
s
ex
ce
ed
th
e
h
o
s
t
p
h
y
s
ical
m
e
m
o
r
y
s
ize,
th
e
h
y
p
er
v
is
o
r
ca
n
p
a
g
e
th
e
VM
to
t
h
e
d
is
k
.
T
h
is
wa
y
,
th
e
h
y
p
er
v
is
o
r
ca
n
d
y
n
a
m
icall
y
co
n
tr
o
l
h
o
w
m
u
c
h
m
e
m
o
r
y
ea
ch
VM
r
ec
ei
v
es.
Fi
g
u
r
e
4
s
h
o
w
s
E
SX
s
er
v
er
m
e
m
o
r
y
m
ap
p
in
g
.
Fig
u
r
e
4
.
E
SX Ser
v
er
Me
m
o
r
y
M
ap
p
in
g
Evaluation Warning : The document was created with Spire.PDF for Python.
I
SS
N
:
2
0
8
8
-
8708
I
J
E
C
E
Vo
l.
7
,
No
.
3
,
J
u
n
e
2
0
1
7
:
1
3
2
6
–
1
3
3
6
1330
2
.
4
.
Dev
ice
a
nd
I
/O
Virt
ua
liza
t
io
n
T
h
e
VM
M
v
ir
tu
alize
s
t
h
e
p
h
y
s
ical
h
ar
d
w
ar
e
an
d
allo
w
s
ea
c
h
v
ir
t
u
al
m
ac
h
i
n
e
a
s
et
o
f
cu
s
to
m
izab
le
v
ir
tu
a
l
d
ev
ices.
Mo
s
t
o
f
t
h
i
s
v
ir
tu
alize
d
I
/O
r
eq
u
ir
es
s
o
f
t
w
ar
e
d
r
iv
er
s
th
at
r
u
n
o
n
th
e
h
o
s
t
o
p
er
atin
g
s
y
s
te
m
to
ac
ce
s
s
th
e
r
ea
l
h
ar
d
w
ar
e.
I
f
it
is
a
t
y
p
e
2
h
y
p
er
v
is
o
r
,
th
e
n
it
w
il
l
u
s
e
t
h
e
d
ev
ice
d
r
iv
er
s
alr
ea
d
y
i
n
th
e
h
o
s
t
OS,
o
th
er
w
is
e
it
m
a
y
b
e
n
ec
e
s
s
ar
y
to
d
ev
elo
p
its
o
w
n
d
ev
ice
d
r
iv
er
s
f
o
r
th
e
h
ar
d
w
ar
e
o
n
th
e
m
ac
h
in
e,
li
k
e
i
n
t
h
e
ca
s
e
o
f
VM
w
ar
e
E
SX.
E
m
u
la
t
io
n
is
n
o
r
m
al
l
y
u
s
ed
f
o
r
a
VM
M
to
h
an
d
le
I
/O
d
ev
ices,
an
d
it
is
th
e
VM
M
th
e
r
esp
o
n
s
ib
le
to
i
m
p
le
m
e
n
t
a
s
o
f
t
w
ar
e
m
o
d
el
o
f
th
e
I
/O
d
ev
ice,
m
ak
i
n
g
b
eliev
e
th
e
g
u
e
s
t
OS
th
a
t
it
is
co
m
m
u
n
icati
n
g
to
a
h
ar
d
w
ar
e
d
ev
ice,
w
h
en
is
co
m
m
u
n
icati
n
g
w
it
h
a
s
o
f
t
w
ar
e
m
o
d
el.
T
h
e
I
/O
v
ir
t
u
aliza
tio
n
m
a
y
p
r
o
v
id
e
to
th
e
g
u
e
s
t,
v
ir
t
u
al
h
ar
d
w
ar
e
th
at
d
o
es
n
o
t
ex
i
s
t
in
th
e
r
ea
l
h
ar
d
w
ar
e,
f
o
r
in
s
tan
ce
,
e
m
u
lati
n
g
a
n
I
DE
h
ar
d
d
is
k
w
h
e
n
t
h
e
r
ea
l
h
ar
d
w
ar
e
is
S
A
T
A
.
T
h
e
d
ir
ec
t
m
e
m
o
r
y
ac
ce
s
s
(
DM
A
)
h
as
p
r
o
b
lem
s
w
h
en
u
s
ed
w
it
h
v
ir
tu
a
l
m
ac
h
i
n
es.
T
h
e
DM
A
co
n
tr
o
ller
ca
n
w
r
ite
to
th
e
en
t
ir
e
p
h
y
s
ical
m
e
m
o
r
y
in
s
tead
o
f
o
n
l
y
th
e
m
e
m
o
r
y
a
s
s
i
g
n
ed
to
th
e
g
u
e
s
t
OS.
I
n
o
r
d
er
to
d
ea
l
w
it
h
t
h
is
p
r
o
b
lem
,
I
n
tel
an
d
AM
D
ad
d
ed
I
/O
Me
m
o
r
y
Ma
n
ag
e
m
e
n
t
Un
it
(
I
OM
MU
)
.
W
ith
I
OM
MU
it
is
p
o
s
s
ib
le
to
r
estr
ict
w
h
ic
h
p
h
y
s
ical
ad
d
r
ess
a
d
ev
ice
m
a
y
ac
ce
s
s
.
2
.
5
.
T
y
pes
o
f
Virt
ua
liza
t
io
n
W
h
en
p
eo
p
le
talk
ab
o
u
t v
ir
t
u
a
lizatio
n
,
n
o
r
m
all
y
t
h
e
y
ar
e
tal
k
in
g
ab
o
u
t ser
v
er
v
ir
t
u
aliza
tio
n
.
Ho
wev
er
,
in
f
o
r
m
atio
n
tech
n
o
lo
g
y
h
as
o
th
er
f
o
r
m
s
o
f
v
ir
tu
aliz
atio
n
co
m
m
o
n
l
y
k
n
o
wn
an
d
u
s
ed
b
y
o
th
er
g
r
o
u
p
s
o
f
p
e
o
p
le.
F
o
r
s
o
m
e,
v
ir
tu
alizatio
n
m
ean
s
s
to
r
ag
e
v
ir
tu
alizatio
n
,
o
r
n
etwo
r
k
v
ir
tu
alizatio
n
o
r
ev
en
ap
p
licatio
n
v
ir
tu
alizatio
n
.
Alth
o
u
g
h
m
y
th
esis
will
o
n
ly
co
n
cer
n
ab
o
u
t
s
er
v
er
v
ir
tu
alizatio
n
,
I
will
d
o
a
b
r
ie
f
ex
p
lan
atio
n
o
f
each
o
n
e
.
2
.
5
.
1
.
Serv
er
Virt
ua
liza
t
io
n
T
h
er
e
ar
e
m
a
n
y
d
i
f
f
er
e
n
t
i
m
p
le
m
e
n
tatio
n
s
o
f
s
er
v
er
v
ir
t
u
al
izatio
n
o
n
,
an
d
f
o
r
a
b
ig
r
an
g
e
o
f
C
P
U
p
latf
o
r
m
s
a
n
d
ar
ch
i
tectu
r
e
s
.
I
n
f
o
r
m
all
y
,
s
er
v
er
v
ir
t
u
aliza
tio
n
ca
n
b
e
s
ee
n
a
s
cr
ea
tin
g
m
a
n
y
v
ir
t
u
al
s
y
s
te
m
s
w
it
h
i
n
a
s
i
n
g
le
p
h
y
s
ical
s
y
s
te
m
.
T
o
ac
co
m
p
lis
h
t
h
is
,
w
e
ca
n
ta
k
e
t
h
r
ee
ap
p
r
o
ac
h
es:
p
h
y
s
ical
la
y
er
,
v
ir
tu
a
lizatio
n
la
y
er
an
d
OS
la
y
er
.
Har
d
w
ar
e
p
ar
titi
o
n
i
n
g
d
iv
id
es
a
s
in
g
le
p
h
y
s
ical
s
er
v
er
i
n
to
p
ar
titi
o
n
s
w
h
er
e
ea
ch
p
ar
titi
o
n
is
ab
le
to
r
u
n
an
o
p
er
atin
g
s
y
s
te
m
w
h
ile
h
y
p
er
v
is
o
r
p
lac
es
a
la
y
er
o
f
s
o
f
t
w
ar
e
b
et
w
ee
n
th
e
p
h
y
s
ical
h
ar
d
w
ar
e
an
d
th
e
m
u
l
tip
le
o
p
er
atin
g
s
y
s
te
m
s
t
h
at
w
i
ll sh
ar
e
t
h
e
s
a
m
e
p
h
y
s
ical
h
ar
d
w
ar
e.
P
h
y
s
ical
L
a
y
er
:
•
Har
d
w
ar
e
p
ar
titi
o
n
i
n
g
:
T
h
e
s
er
v
er
is
p
h
y
s
icall
y
s
eg
m
e
n
te
d
in
to
d
is
tin
ct
s
m
aller
s
y
s
te
m
s
th
at
w
i
ll
ac
t
as
a
p
h
y
s
icall
y
in
d
ep
en
d
e
n
t
an
d
s
elf
-
co
n
tai
n
ed
s
er
v
er
.
No
r
m
all
y
ea
ch
o
f
t
h
e
s
e
s
m
aller
s
y
s
t
e
m
s
h
as
t
h
eir
o
wn
C
P
Us,
OS,
b
o
o
t
ar
ea
,
m
e
m
o
r
y
a
n
d
n
et
w
o
r
k
r
eso
u
r
ce
s
.
T
h
e
i
m
p
le
m
e
n
tatio
n
o
f
t
h
is
tec
h
n
i
q
u
e
i
n
clu
d
e
s
S
tatic
Har
d
P
ar
titi
o
n
in
g
,
v
P
ar
,
n
P
ar
a
m
o
n
g
o
th
er
s
[
2
7
]
.
Vir
tu
aliza
t
io
n
la
y
er
: H
y
p
er
v
i
s
o
r
tech
n
o
lo
g
y
ca
n
b
e
o
r
g
an
ize
d
in
s
o
m
e
d
is
ti
n
ct
ca
te
g
o
r
ies:
• F
u
ll
v
ir
t
u
aliza
tio
n
:
Allo
w
s
v
i
r
tu
al
i
n
f
r
astr
u
ctu
r
e
s
to
r
u
n
u
n
m
o
d
i
f
ied
o
p
er
atin
g
s
y
s
te
m
s
i
n
s
ep
ar
atio
n
.
P
r
esen
t
o
p
er
atin
g
s
y
s
te
m
(
O
S)
ex
ec
u
t
in
g
in
s
id
e
th
e
v
ir
t
u
al
m
ac
h
in
e
is
ca
lled
g
u
est
o
p
er
atin
g
s
y
s
t
e
m
.
T
h
is
ap
p
r
o
ac
h
w
a
s
p
io
n
ee
r
ed
i
n
1
9
6
7
w
it
h
I
B
M
C
P
-
4
0
an
d
C
P
-
6
7
,
p
r
ed
ec
ess
o
r
s
o
f
VM
f
a
m
i
l
y
.
I
n
o
r
d
er
to
i
m
p
le
m
e
n
t
f
u
ll
v
ir
tu
a
lizatio
n
,
it
i
s
n
ec
ess
ar
y
a
f
u
ll
co
m
b
in
at
io
n
o
f
h
ar
d
w
ar
e
an
d
s
o
f
t
w
ar
e,
h
o
w
e
v
er
n
o
t
all
ar
ch
it
ec
t
u
r
es
h
av
e
h
ar
d
w
ar
e
to
s
u
p
p
o
r
t
v
ir
t
u
aliz
atio
n
.
I
t
w
as
n
o
t
ac
h
ie
v
ab
le
o
n
I
B
M
Sy
s
te
m
/3
7
0
u
n
til
1
9
7
2
an
d
it
w
a
s
n
o
t
n
ati
v
el
y
p
o
s
s
ib
le
in
t
h
e
x
8
6
ar
ch
itectu
r
e
[
2
8
]
u
n
til
2
0
0
5
w
h
e
n
I
n
tel
a
n
d
A
MD
a
d
d
ed
th
e
h
ar
d
w
ar
e
v
ir
tu
a
lizatio
n
ex
ten
s
io
n
s
(
I
n
t
el
VT
an
d
A
MD
-
V
r
e
s
p
ec
ti
v
el
y
)
.
Nev
er
t
h
eles
s
,
m
a
n
y
c
o
m
p
a
n
ies
tr
ied
to
ac
co
m
p
li
s
h
f
u
ll
v
ir
tu
aliza
tio
n
o
n
x
8
6
ar
ch
itectu
r
e
ev
e
n
b
ef
o
r
e
I
n
tel
VT
an
d
A
MD
-
V
ad
d
itio
n
s
.
VM
w
ar
e
u
s
e
s
a
co
m
b
i
n
atio
n
o
f
d
ir
ec
t
i
m
p
le
m
en
ta
tio
n
w
it
h
b
in
ar
y
tr
an
s
lat
io
n
tec
h
n
iq
u
es
[
2
9
]
to
ac
co
m
p
lis
h
f
u
l
l
v
ir
tu
a
lizatio
n
o
f
an
x
8
6
s
y
s
te
m
.
Fi
g
u
r
e
5
s
h
o
w
s
t
h
e
b
in
ar
y
tr
an
s
latio
n
ap
p
r
o
ac
h
to
x
8
6
v
ir
tu
aliza
tio
n
u
s
ed
b
y
VM
w
ar
e
Fig
u
r
e
5
.
T
h
e
B
in
ar
y
T
r
an
s
lati
o
n
A
p
p
r
o
ac
h
to
x
8
6
V
ir
tu
aliza
tio
n
u
s
ed
b
y
V
M
w
ar
e
Evaluation Warning : The document was created with Spire.PDF for Python.
I
J
E
C
E
I
SS
N:
2088
-
8708
A
S
u
r
ve
y
o
n
S
ec
u
r
ity
A
s
p
ec
ts
o
f S
erver V
ir
tu
a
liz
a
tio
n
in
C
lo
u
d
C
o
mp
u
tin
g
(
O
S
r
i Na
g
esh
)
1331
•
P
ar
a
v
ir
tu
aliza
tio
n
:
m
o
d
if
ies
th
e
g
u
e
s
t
k
er
n
el
s
y
s
te
m
i
n
o
r
d
er
to
p
u
r
g
e
th
e
n
ec
ess
it
y
o
f
b
in
ar
y
tr
an
s
latio
n
.
I
t
h
as
th
e
ad
v
a
n
ta
g
e
o
f
h
i
g
h
er
p
er
f
o
r
m
a
n
ce
b
u
t
h
a
s
t
h
e
d
r
a
w
b
ac
k
o
f
n
ee
d
in
g
a
m
o
d
i
f
ie
d
o
p
er
atin
g
s
y
s
te
m
k
er
n
el.
T
h
e
f
ac
t
t
h
e
v
ir
tu
a
l
p
la
tf
o
r
m
is
n
o
t
id
en
tical
to
t
h
e
r
e
al
h
ar
d
w
ar
e,
it
m
a
k
e
s
n
ec
ess
ar
y
f
o
r
t
h
e
o
p
er
atin
g
s
y
s
te
m
to
b
e
p
o
r
ted
to
th
e
ab
s
tr
ac
ted
m
ac
h
i
n
e
i
n
ter
f
ac
e.
T
h
i
s
co
u
ld
b
e
s
ee
n
as
a
v
io
latio
n
o
f
th
e
Go
ld
b
er
g
’
s
eq
u
iv
ale
n
ce
r
eq
u
ir
e
m
e
n
ts
,
b
ec
au
s
e
th
e
ar
ch
itect
u
r
e
-
d
ep
en
d
en
t
p
ar
t
o
f
t
h
e
o
p
er
atin
g
s
y
s
te
m
k
er
n
el
n
ee
d
s
to
b
e
ch
an
g
ed
[
3
0
]
.
T
h
e
n
o
n
v
ir
t
u
al
izab
le
in
s
tr
u
ctio
n
s
ar
e
r
ep
lace
d
w
it
h
h
y
p
er
ca
ll
s
th
a
t
co
m
m
u
n
icate
d
ir
ec
tl
y
w
it
h
th
e
v
ir
t
u
aliza
t
io
n
la
y
er
h
y
p
er
v
is
o
r
.
T
h
e
ar
ch
itectu
r
e
i
n
d
ep
en
d
en
t
p
ar
t
an
d
th
e
en
tire
u
s
er
m
o
d
e
s
o
f
t
w
ar
e
s
tac
k
s
ta
y
u
n
m
o
d
if
ied
.
•
E
m
u
latio
n
:
Occ
a
s
io
n
al
l
y
c
o
m
m
u
n
it
y
co
n
f
o
u
n
d
s
e
m
u
lat
io
n
w
it
h
f
u
ll
v
ir
t
u
aliza
tio
n
.
E
v
en
th
o
u
g
h
b
o
t
h
o
p
er
ate
u
n
m
o
d
i
f
ied
g
u
e
s
t
o
p
e
r
atin
g
s
y
s
te
m
s
,
t
h
e
y
ar
e
b
o
th
v
er
y
d
i
f
f
er
en
t.
I
n
e
m
u
latio
n
,
t
h
e
v
ir
tu
a
l
m
ac
h
in
e
s
i
m
u
late
s
th
e
e
n
tire
h
ar
d
w
ar
e
s
et
n
ee
d
ed
to
r
u
n
th
e
u
n
m
o
d
i
f
ied
g
u
es
t
OS
n
o
r
m
all
y
f
o
r
a
co
m
p
lete
l
y
d
i
f
f
er
e
n
t
h
ar
d
w
ar
e
ar
ch
i
tectu
r
e.
T
h
er
e
ar
e
s
o
m
e
u
til
ities
f
o
r
th
i
s
tech
n
i
q
u
e.
Op
er
atin
g
S
y
s
te
m
la
y
er
:
•
Op
er
atin
g
S
y
s
te
m
-
L
ev
e
l
Vi
r
tu
aliza
tio
n
:
T
h
is
is
a
tech
n
o
lo
g
y
t
h
at
v
ir
t
u
alize
s
s
er
v
er
s
at
th
e
OS
(
k
er
n
el)
la
y
er
.
T
h
e
p
h
y
s
ical
s
er
v
er
an
d
in
s
t
an
ce
o
f
t
h
e
OS
i
s
v
ir
tu
a
liz
ed
in
to
m
u
ltip
le
is
o
lated
p
ar
tit
io
n
s
.
E
ac
h
o
f
t
h
e
m
w
il
l
lo
o
k
li
k
e
a
r
ea
l
s
er
v
er
,
f
r
o
m
t
h
e
p
o
in
t
o
f
v
ie
w
o
f
it
s
o
w
n
er
.
T
h
e
OS
k
er
n
el
w
i
ll
r
u
n
a
s
in
g
le
O
S
an
d
p
r
o
v
id
e
its
f
u
n
ctio
n
alit
y
to
ea
ch
o
f
t
h
e
p
ar
titi
o
n
s
.
2
.
5
.
2
.
Sto
ra
g
e
Virt
ua
liza
t
io
n
Sto
r
ag
e
v
ir
t
u
aliza
tio
n
h
as
b
e
en
ar
o
u
n
d
f
o
r
a
n
u
m
b
er
o
f
y
ea
r
s
.
I
t
h
as
b
eg
i
n
n
in
g
w
it
h
th
e
u
s
e
o
f
r
ed
u
n
d
an
t
ar
r
a
y
o
f
i
n
d
ep
en
d
e
n
t
d
is
k
s
(
R
A
I
D)
.
Usi
n
g
R
A
I
D
it
is
p
o
s
s
ib
le
to
lo
g
ical
l
y
g
r
o
u
p
p
h
y
s
ica
l
d
is
k
s
an
d
p
r
esen
t
t
h
o
s
e
g
r
o
u
p
i
n
g
s
a
s
a
v
ir
t
u
al
d
is
k
to
th
e
O
S.
Us
in
g
s
to
r
ag
e
v
ir
tu
a
lizatio
n
i
t
is
p
o
s
s
ib
le
to
m
er
g
e
p
h
y
s
ical
s
to
r
ag
e
f
r
o
m
m
a
n
y
d
ev
ices
w
h
ic
h
w
ill
ap
p
ea
r
as
a
s
in
g
le
s
to
r
ag
e
p
o
o
l.
T
h
is
s
to
r
a
g
e
ca
n
b
e
clas
s
i
f
ied
as
d
ir
ec
t
attac
h
ed
s
to
r
ag
e
(
DAS)
,
n
et
w
o
r
k
attac
h
ed
s
to
r
ag
e
(
NAS)
an
d
s
to
r
ag
e
ar
ea
n
et
w
o
r
k
(
S
A
N)
.
T
h
ey
ca
n
b
e
lin
k
ed
u
s
i
n
g
F
ib
r
e
C
h
a
n
n
e
l
,
Fib
r
e
C
h
an
n
el
a
n
d
I
n
ter
n
et
S
m
all
C
o
m
p
u
ter
S
y
s
te
m
s
I
n
ter
f
ac
e
(
iSC
SI)
,
Fib
r
e
C
h
a
n
n
el
o
n
E
t
h
er
n
et
o
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t
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2
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5
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3
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w
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rk
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en
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ar
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a.
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0
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.
1
Q
s
tan
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ar
d
,
is
a
m
eth
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o
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cr
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n
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m
en
t
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ter
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f
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n
t
n
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e
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co
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m
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t
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e
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o
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t
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k
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h
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s
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n
t
f
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ll
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d
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ts
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r
e,
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A
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s
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et
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P
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n
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l
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f
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to
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t
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ter
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ts
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ted
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n
et
w
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k
d
ev
ice.
c.
Vir
tu
al
P
r
iv
ate
Net
w
o
r
k
(
VP
N)
:
I
t
is
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p
r
iv
ate
co
m
m
u
n
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n
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t
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T
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3
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l:
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te
m
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[
4
5
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an
d
Up
d
ate
8
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o
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E
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.
5
[
4
6
]
.
Vir
tu
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Ma
ch
in
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Fil
e
S
y
s
te
m
(
VM
FS
)
:
T
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VM
FS
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h
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ta
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to
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tu
al
C
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ter
:
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e
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Vir
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ter
is
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e
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a
lized
en
ter
p
r
is
e
en
v
ir
o
n
m
en
ts
.
3
.
2
.
VM
w
a
re
E
SXi
VM
w
ar
e
E
SXi
w
a
s
a
n
n
o
u
n
ce
d
d
u
r
in
g
VM
w
o
r
ld
2
0
0
7
an
d
it
is
a
n
i
n
te
g
r
ated
v
er
s
io
n
o
f
VM
w
ar
e
E
SX
b
u
t
w
it
h
o
u
t
th
e
C
O
S.
T
h
is
is
i
m
p
o
r
tan
t
i
n
ter
m
s
o
f
s
ec
u
r
it
y
.
VM
w
ar
e
E
SXi
h
ad
R
HE
L
-
b
ased
C
OS
r
ep
lace
d
w
it
h
B
u
s
y
B
o
x
,
w
h
ic
h
i
s
a
s
i
n
g
le
b
in
ar
y
t
h
at
p
r
o
v
id
es a
m
i
n
i
m
al
s
et
o
f
s
er
v
ices.
Ma
n
y
o
f
th
e
s
ec
u
r
it
y
p
atch
es
f
o
r
VM
w
ar
e
E
SX
w
h
er
e
r
elate
d
w
it
h
s
ec
u
r
it
y
v
u
ln
e
r
ab
ilit
ies o
n
th
e
Ser
v
ice
C
o
n
s
o
le
(
e.
g
.
C
VE
-
2009
-
1
1
8
5
,
C
VE
-
2009
-
0
0
3
4
,
C
VE
-
2009
-
0
8
4
6
)
.
3
.
3
.
Xen
T
h
e
Xen
p
r
o
j
ec
t
w
as
f
ir
s
t
d
es
cr
ib
ed
in
t
h
e
p
ap
er
“
Xe
n
a
n
d
th
e
A
r
t
o
f
Vir
t
u
aliza
tio
n
”
p
r
esen
ted
a
t
SOSP
in
2
0
0
3
[
4
9
]
.
I
t
w
a
s
a
p
r
o
j
ec
t
o
r
ig
in
ated
b
y
t
h
e
S
y
s
te
m
R
e
s
ea
ch
Gr
o
u
p
at
t
h
e
Un
i
v
er
s
it
y
o
f
C
a
m
b
r
id
g
e
C
o
m
p
u
ter
L
ab
o
r
ato
r
y
an
d
w
a
s
p
ar
t
o
f
th
e
X
en
o
Ser
v
er
s
p
r
o
j
ec
ts
[
5
0
]
w
h
ic
h
h
ad
th
e
g
o
al
o
f
b
u
ild
a
p
u
b
lic
in
f
r
astru
ct
u
r
e
f
o
r
g
lo
b
al
-
s
ca
le
s
er
v
ice
d
ep
lo
y
m
e
n
t.
Xe
n
So
u
r
ce
,
I
n
c.
w
a
s
a
co
m
p
a
n
y
f
o
u
n
d
ed
b
y
I
an
P
r
att,
s
en
io
r
lect
u
r
er
at
C
a
m
b
r
id
g
e
a
n
d
lead
o
f
th
e
Xen
p
r
o
j
ec
t,
w
it
h
th
e
g
o
al
o
f
s
u
p
p
o
r
tin
g
a
n
d
d
ev
elo
p
in
g
th
e
o
p
en
s
o
u
r
ce
Xen
p
r
o
j
ec
t
an
d
to
cr
ea
te
a
co
m
m
er
cial
en
ter
p
r
is
e
v
er
s
io
n
o
f
t
h
e
s
o
f
t
w
ar
e.
I
n
2
0
0
5
,
Xen
So
u
r
ce
r
elea
s
e
Xen
3
.
0
.
Xen
is
a
n
o
p
en
-
s
o
u
r
ce
h
y
p
er
v
is
o
r
f
o
r
b
o
th
3
2
an
d
6
4
b
it
p
r
o
ce
s
s
ar
ch
itect
u
r
e
t
h
at
r
u
n
s
o
n
to
p
o
f
th
e
b
ar
e
-
m
etal.
I
t
al
lo
w
s
to
s
ec
u
r
el
y
an
d
ef
f
icie
n
tl
y
r
u
n
s
e
v
er
a
l
v
ir
tu
al
g
u
est
OS
o
n
t
h
e
s
a
m
e
h
o
s
t
at
th
e
s
a
m
e
ti
m
e.
Xe
n
as
m
an
y
f
ea
tu
r
es a
s
:
a.
Nea
r
n
ativ
e
p
er
f
o
r
m
an
ce
o
n
t
h
e
v
ir
tu
al
m
ac
h
i
n
es
b.
Fu
ll
s
u
p
p
o
r
t o
n
x
8
6
(
3
2
-
b
it)
w
ith
an
d
w
it
h
o
u
t P
h
y
s
ical
A
d
d
r
ess
E
x
te
n
s
io
n
(
P
A
E
)
c.
Fu
ll
s
u
p
p
o
r
t o
n
x
8
6
w
i
th
6
4
-
b
i
t e
x
p
an
s
io
n
d.
Su
p
p
o
r
t f
o
r
al
m
o
s
t a
ll
h
ar
d
w
ar
e
w
it
h
L
i
n
u
x
d
r
iv
er
s
a
v
ailab
le
e.
L
i
v
e
m
ig
r
atio
n
o
f
r
u
n
n
in
g
v
ir
t
u
al
m
ac
h
i
n
es b
et
w
ee
n
t
w
o
p
h
y
s
ical
h
o
s
t
s
w
it
h
ze
r
o
d
o
w
n
ti
m
e
f.
Su
p
p
o
r
t
o
f
Har
d
w
ar
e
Vir
t
u
aliza
tio
n
e
x
ten
s
io
n
s
f
r
o
m
I
n
tel
(
I
n
tel
-
VT
)
a
n
d
A
MD
(
AM
DV)
,
allo
w
i
n
g
u
n
m
o
d
if
ied
g
u
e
s
t o
p
er
atin
g
s
y
s
te
m
s
.
3
.
4
.
K
VM
KVM
s
ta
n
d
s
f
o
r
Ker
n
el
-
b
ase
d
Vir
tu
al
Ma
c
h
i
n
e
an
d
i
s
f
u
l
l
v
ir
t
u
aliza
tio
n
to
o
l
f
o
r
L
i
n
u
x
o
n
x
8
6
m
ac
h
in
e,
o
n
t
h
e
b
asis
o
f
v
ir
t
u
aliza
tio
n
in
h
ar
d
w
ar
e
ex
ten
s
io
n
s
(
I
n
tel
VT
-
X
an
d
A
MD
V)
an
d
an
ad
o
p
ted
v
er
s
io
n
o
f
QE
MU
,
u
s
i
n
g
th
e
L
i
n
u
x
Ker
n
el
as
t
h
e
H
y
p
er
v
is
o
r
[
5
3
]
.
KVM
ca
n
n
o
t
o
p
er
te
o
n
C
P
Us
w
i
th
o
u
t
t
h
e
h
ar
d
w
ar
e
v
ir
tu
al
izatio
n
e
x
ten
s
io
n
s
.
KVM
co
n
s
is
t
s
o
f
t
w
o
m
o
d
u
les:
a.
k
v
m
.
k
o
:
A
lo
ad
ab
le
k
er
n
el
m
o
d
u
le
th
at
p
r
o
v
id
es t
h
e
co
r
e
v
ir
t
u
aliza
tio
n
in
f
r
astr
u
ct
u
r
e
b.
k
v
m
-
[
in
tel
|
a
m
d
]
.
k
o
:
A
p
r
o
ce
s
s
o
r
s
p
ec
if
ic
m
o
d
u
le
f
o
r
I
n
tel
o
r
A
DM
.
Evaluation Warning : The document was created with Spire.PDF for Python.
I
J
E
C
E
I
SS
N:
2088
-
8708
A
S
u
r
ve
y
o
n
S
ec
u
r
ity
A
s
p
ec
ts
o
f S
erver V
ir
tu
a
liz
a
tio
n
in
C
lo
u
d
C
o
mp
u
tin
g
(
O
S
r
i Na
g
esh
)
1333
4.
SE
CUR
I
T
Y
O
F
VIRT
UAL
M
ACH
I
NE
S
Vir
tu
al
Ma
ch
in
e
tec
h
n
o
lo
g
y
is
m
ai
n
s
tr
ea
m
,
i
m
p
le
m
e
n
ted
o
n
ev
er
y
b
r
an
ch
o
f
th
e
i
n
d
u
s
tr
y
(
e.
g
.
T
elec
o
m
,
Fi
n
an
ce
)
,
r
u
n
n
i
n
g
c
r
itical
s
er
v
ice
s
,
w
h
ich
w
er
e
p
r
ev
io
u
s
l
y
i
m
p
le
m
e
n
ted
in
is
o
lated
s
er
v
er
s
.
O
n
e
i
m
p
o
r
tan
t
i
s
s
u
e
is
s
ec
u
r
it
y
.
Acc
o
r
d
in
g
to
Gar
tn
er
[
6
0
]
,
"
th
r
o
u
g
h
2
0
0
9
,
6
0
p
er
ce
n
t
o
f
p
r
o
d
u
ctio
n
VM
s
w
il
l
b
e
less
s
ec
u
r
e
th
a
n
th
eir
p
h
y
s
ical
co
u
n
ter
p
ar
ts
"
an
d
th
at
"3
0
p
e
r
ce
n
t
o
f
d
ep
lo
y
m
en
ts
[
w
ill
b
e
ass
o
ciate
d
]
w
it
h
a
V
M
-
r
elate
d
s
ec
u
r
it
y
in
cid
e
n
t
"
.
W
ith
v
ir
t
u
aliza
tio
n
,
a
n
e
w
s
ce
n
ar
io
is
p
r
ese
n
ted
,
w
i
th
all
t
h
e
s
er
v
er
s
co
n
s
o
lid
ated
o
n
a
s
i
n
g
le
s
er
v
e
r
r
u
n
n
in
g
t
h
r
ee
v
ir
tu
al
m
ac
h
i
n
es.
I
n
t
h
is
ca
s
e
,
a
n
e
w
t
h
r
ea
t
m
o
d
el
(
Fig
u
r
e
6
(
b
)
o
n
p
ag
e
4
6
)
allo
w
s
n
o
t
o
n
l
y
t
h
e
s
a
m
e
at
tack
s
as
t
h
e
tr
ad
itio
n
al
m
o
d
el
b
u
t
al
s
o
o
p
en
s
th
e
p
o
s
s
ib
ilit
y
to
d
o
n
e
w
attac
k
s
a
n
d
ex
p
lo
r
e
n
e
w
v
u
l
n
er
ab
ilit
ies.
Si
n
ce
ea
ch
VM
ca
n
b
e
“
e
x
ac
tl
y
t
h
e
s
a
m
e”
a
s
t
h
e
r
ea
l
o
n
e
(
i
n
th
e
s
en
s
e
th
at
i
t
ca
n
h
av
e,
f
o
r
in
s
tan
ce
,
t
h
e
s
a
m
e
n
u
m
b
er
o
f
C
P
Us,
a
m
o
u
n
t
o
f
m
e
m
o
r
y
,
p
atc
h
es
i
n
s
talled
an
d
co
n
f
i
g
u
r
atio
n
)
,
a
n
attac
k
er
ca
n
e
x
p
lo
r
e
a
v
u
l
n
er
ab
ilit
y
i
n
a
n
ap
p
licatio
n
t
h
e
s
a
m
e
w
a
y
a
s
it
w
as
d
o
n
e
o
n
t
h
e
tr
ad
itio
n
al
t
h
r
ea
t
m
o
d
el
(
ar
r
o
w
s
#
1
)
.
B
esid
es
t
h
at,
s
h
e
h
as
n
e
w
tar
g
et
s
to
ch
ec
k
f
o
r
v
u
ln
er
ab
ilit
ies.
I
f
t
h
e
v
ir
tu
a
lizatio
n
la
y
er
h
a
v
e
v
u
ln
er
ab
ilit
ies,
s
h
e
co
u
ld
lau
n
c
h
an
attac
k
f
r
o
m
a
g
u
est
OS
a
g
ai
n
s
t
t
h
e
o
th
er
s
VM
s
in
t
h
e
s
a
m
e
h
o
s
t
(
ar
r
o
w
s
#
2
)
,
o
r
co
u
ld
attac
k
t
h
e
h
o
s
t
b
y
d
o
in
g
a
d
en
ia
l
o
f
s
er
v
ice
ex
p
lo
r
in
g
th
e
h
o
s
t
v
u
l
n
er
ab
ilit
y
i
n
a
v
ir
t
u
al
d
ev
ic
e
.
Do
in
g
t
h
is
a
ttack
,
s
h
e
co
u
l
d
attac
k
t
h
e
o
t
h
er
g
u
est
s
i
n
t
h
e
s
a
m
e
h
o
s
t
(
ar
r
o
w
s
#
3
)
.
T
h
e
i
m
p
ac
t
o
f
co
m
p
r
o
m
is
e
th
e
v
ir
t
u
aliza
tio
n
la
y
er
r
ai
s
e
s
th
e
r
is
k
’
s
le
v
el,
s
in
ce
i
t
is
a
cr
itical
ass
e
t
s
h
ar
ed
b
y
all
t
h
e
v
ir
tu
a
l
m
ac
h
i
n
es.
H
o
w
e
v
er
,
th
e
attac
k
ca
n
b
e
r
e
m
o
te
to
o
(
a
r
r
o
w
#
4
)
.
(
a)
(
b
)
Fig
u
r
e
6
.
(
a)
T
r
ad
itio
n
al
th
r
ea
t m
o
d
el
,
(
b
)
Ne
w
t
h
r
ea
t
m
o
d
el
5.
ANALY
Z
E
O
F
S
E
CUR
I
T
Y
VULN
E
RAB
I
L
I
T
I
E
S I
N
VI
RT
UA
L
I
Z
A
T
I
O
N
5
.
1
.
At
t
a
ck
es f
ro
m
t
he
G
ues
t
t
o
t
he
H
o
s
t
T
h
er
e
ca
n
b
e
s
o
m
e
e
x
ter
n
al
o
r
in
ter
n
al
f
ac
to
r
s
t
h
at
ca
n
co
m
p
r
o
m
i
s
e
is
o
latio
n
as
m
i
s
s
i
m
p
le
m
en
tatio
n
co
n
f
i
g
u
r
atio
n
o
r
s
o
m
e
b
u
g
in
th
e
v
ir
tu
al
izatio
n
s
o
f
t
w
ar
e.
An
y
attac
k
s
ca
n
b
e
m
ad
e
if
i
s
o
latio
n
b
et
w
ee
n
th
e
Vir
tu
al
Ma
c
h
i
n
e
a
n
d
t
h
e
h
o
s
t
w
h
ic
h
m
a
y
b
e
d
an
g
er
o
u
s
.
An
y
o
n
e
m
a
y
b
e
co
m
p
r
o
m
is
ed
ca
u
s
e
s
d
an
g
er
o
u
s
ef
f
ec
ts
.
T
h
at
attac
k
is
ca
lled
”
VM
escap
e”
an
d
h
ap
p
en
s
w
h
e
n
a
p
r
o
g
r
am
ca
n
b
y
p
ass
t
h
e
v
i
r
tu
al
m
ac
h
i
n
e
la
y
er
f
r
o
m
in
s
id
e
a
VM
an
d
g
et
ac
ce
s
s
to
th
e
h
o
s
t
m
ac
h
in
e.
T
h
e
h
o
s
t
m
ac
h
in
e
is
t
h
e
r
o
o
t
o
f
all
t
h
e
VM
s
,
an
d
s
o
if
a
p
r
o
g
r
am
escap
es
f
r
o
m
th
e
v
ir
tu
al
m
ac
h
in
e
s
p
r
iv
i
leg
e
s
it
w
ill
g
et
r
o
o
t,
allo
w
i
n
g
to
co
n
tr
o
l
a
ll
th
e
VM
s
an
d
t
h
e
tr
af
f
ic
b
et
w
ee
n
t
h
e
m
.
T
h
i
s
k
i
n
d
o
f
at
tack
ar
e
n
o
r
m
al
l
y
p
o
s
s
ib
le
b
y
e
x
p
lo
iti
n
g
b
u
g
s
o
n
t
h
e
VM
M
co
m
b
i
n
ed
w
it
h
i
m
p
r
o
p
er
l
y
co
n
f
ig
u
r
atio
n
o
f
t
h
e
h
o
s
t/
g
u
est
i
n
ter
ac
tio
n
.
Ho
w
e
v
er
,
cu
r
r
e
n
t
VM
Ms
d
o
n
o
t
o
f
f
er
p
er
f
ec
t
is
o
latio
n
,
alt
h
o
u
g
h
t
h
e
y
clai
m
to
.
Ma
n
y
b
u
g
s
h
a
v
e
b
ee
n
f
o
u
n
d
in
all
p
o
p
u
lar
VM
Ms,
s
o
m
e
o
f
th
e
m
allo
w
i
n
g
”VM
escap
e”
,
lik
e
th
e
VM
war
e
W
o
r
k
s
tatio
n
6
C
VE
-
2007
-
4
4
9
6
[
6
2
]
b
u
g
d
is
co
v
er
ed
b
y
R
a
f
al
W
o
j
tczu
k
w
h
ic
h
allo
w
s
au
th
e
n
ticated
u
s
er
s
w
it
h
ad
m
in
i
s
tr
ati
v
e
p
r
i
v
ile
g
es
o
n
a
g
u
est
o
p
er
atin
g
s
y
s
te
m
to
co
r
r
u
p
t
m
e
m
o
r
y
an
d
p
o
s
s
ib
l
y
e
x
ec
u
te
ar
b
itra
r
y
co
d
e
o
n
th
e
h
o
s
t o
p
er
atin
g
s
y
s
te
m
v
ia
u
n
s
p
ec
i
f
ied
v
ec
to
r
s
.
5
.
2
.
Re
m
o
t
e
M
a
na
g
em
ent
V
uln
e
ra
bil
it
ies
I
t
is
c
o
m
m
o
n
i
n
t
h
e
c
u
r
r
en
t
VM
E
n
v
ir
o
n
m
e
n
ts
to
h
a
v
e
a
m
an
a
g
e
m
e
n
t
co
n
s
o
les
t
h
at
m
an
ag
e
s
t
h
e
v
ir
tu
a
l
m
ac
h
i
n
es.
No
r
m
all
y
,
co
m
m
er
cial
p
r
o
d
u
cts
h
a
v
e
t
h
eir
o
w
n
.
Fo
r
in
s
tan
ce
,
VM
war
e
u
s
es
V
M
w
ar
e
v
Sp
h
er
e
to
m
a
n
ag
e
th
e
H
y
p
e
r
v
is
o
r
,
w
h
i
le
C
i
tr
ix
Xen
Ser
v
e
r
ca
n
u
s
e
Xe
n
C
e
n
ter
.
T
h
ese
c
o
n
s
o
les
b
r
in
g
n
e
w
f
ac
ilit
ies
f
o
r
ad
m
i
n
is
tr
ato
r
s
to
m
an
a
g
e
th
e
ir
m
ac
h
in
e
s
,
b
u
t
also
o
p
en
n
e
w
v
u
ln
er
ab
ilit
ies
.
C
o
m
p
r
o
m
is
i
n
g
a
m
an
a
g
e
m
e
n
t
co
n
s
o
le
allo
w
s
an
attac
k
er
to
co
n
tr
o
l
all
th
e
v
ir
tu
al
m
ac
h
i
n
e
s
m
a
n
ag
ed
b
y
i
t.
T
h
is
k
in
d
o
f
tech
n
o
lo
g
y
g
e
n
er
all
y
r
elate
d
w
it
h
th
e
VM
M
u
s
in
g
HT
T
P
/
HT
T
P
S
w
h
o
s
e
m
ea
n
i
n
g
is
t
h
e
VM
M
i
s
h
av
in
g
s
er
v
ice
r
u
n
n
in
g
ac
ce
p
tin
g
HT
T
P
co
n
n
ec
tio
n
.
Xen
,
f
o
r
in
s
ta
n
ce
,
h
as
t
h
e
Xen
A
P
I
HT
T
P
I
n
ter
f
ac
e
t
h
at
h
ad
a
Evaluation Warning : The document was created with Spire.PDF for Python.
I
SS
N
:
2
0
8
8
-
8708
I
J
E
C
E
Vo
l.
7
,
No
.
3
,
J
u
n
e
2
0
1
7
:
1
3
2
6
–
1
3
3
6
1334
C
r
o
s
s
-
s
ite
s
cr
ip
tin
g
(
XSS)
s
u
s
ce
p
tib
ilit
y
,
w
h
ich
p
er
m
i
tted
r
u
n
n
i
n
g
a
s
cr
ip
t
co
d
e
in
a
u
s
er
’
s
b
r
o
w
s
er
s
es
s
io
n
i
n
co
n
tex
t
o
f
a
n
af
f
ec
ted
s
ite.
H
y
p
er
VM
[
6
6
]
is
a
m
u
lti
-
tier
ed
,
m
u
lti
-
s
er
v
er
,
m
u
lti
-
v
ir
t
u
aliza
t
i
o
n
s
o
f
t
w
ar
e
w
h
ich
allo
w
s
to
cr
ea
te
an
d
m
an
a
g
e
d
if
f
er
e
n
t
Vir
tu
a
l
Ma
ch
i
n
es
(
Xen
o
r
Op
en
VZ
)
ea
ch
w
it
h
ea
ch
Vir
tu
al
P
r
iv
ate
Ser
v
er
(
VP
S)
h
av
i
n
g
i
ts
o
w
n
o
p
er
atin
g
s
y
s
te
m
.
5
.
3
.
Denia
l o
f
Serv
ice
A
Den
ial
o
f
Ser
v
ice
(
Do
S)
h
as
t
h
e
g
o
al
to
m
a
k
e
a
co
m
p
u
t
er
r
eso
u
r
ce
n
o
t
av
a
ilab
le
to
it
s
i
n
ten
d
ed
u
s
er
s
.
I
n
v
ir
t
u
al
m
ac
h
i
n
e
ar
c
h
itectu
r
e,
r
eso
u
r
ce
s
a
s
C
P
U,
m
e
m
o
r
y
,
s
to
r
ag
e
an
d
n
et
w
o
r
k
ar
e
co
m
m
o
n
a
m
o
n
g
th
e
h
o
s
t
a
n
d
th
e
g
u
es
ts
.
I
t
i
s
t
h
en
p
r
o
b
ab
le
f
o
r
a
g
u
est
m
ac
h
i
n
e
to
f
o
r
ce
a
d
en
ial
o
f
s
er
v
ice
(
in
ten
tio
n
al
o
r
n
o
t)
to
o
th
er
s
g
u
es
t
w
h
ic
h
w
o
u
ld
also
in
f
lu
e
n
ce
th
e
h
o
s
t
b
y
ca
p
tiv
ati
n
g
all
th
e
p
o
ten
tial
r
eso
u
r
ce
s
o
f
th
e
s
y
s
te
m
.
W
h
en
o
th
er
g
u
e
s
ts
at
te
m
p
t
to
r
eq
u
est
a
r
eso
u
r
ce
,
th
e
s
y
s
te
m
w
il
l
d
en
y
t
h
at
ac
ce
s
s
s
in
ce
t
h
er
e
is
n
o
r
eso
u
r
ce
av
ailab
le.
VM
w
ar
e
h
as
b
ee
n
s
h
o
w
n
to
s
u
f
f
er
f
r
o
m
s
e
v
er
al
Do
S
v
u
l
n
er
ab
ilit
ies(4
.
2
)
.
A
g
o
o
d
ap
p
r
o
ac
h
to
p
r
ev
en
t
t
h
is
attac
k
f
r
o
m
a
g
u
e
s
t
is
to
li
m
it
t
h
e
r
eso
u
r
ce
s
V
Ms
ca
n
ac
ce
s
s
.
Mo
s
t
o
f
t
h
e
c
u
r
r
en
t
v
ir
tu
al
izatio
n
tech
n
o
lo
g
ies
h
av
e
t
h
e
m
ec
h
a
n
is
m
s
n
ec
e
s
s
ar
y
to
li
m
it
t
h
e
r
es
o
u
r
ce
s
allo
ca
ted
to
ea
ch
g
u
es
t
m
ac
h
i
n
e.
W
ith
t
h
e
co
r
r
ec
t c
o
n
f
ig
u
r
atio
n
o
f
t
h
e
h
o
s
t v
ir
t
u
aliza
tio
n
,
th
i
s
attac
k
ca
n
b
e
m
i
n
i
m
ized
.
6.
CO
NCLU
SI
O
N
T
h
is
p
ap
er
is
a
r
esu
lt
o
f
s
tu
d
y
w
o
r
k
ab
o
u
t
v
ir
tu
al
m
ac
h
i
n
es,
t
h
eir
p
r
in
cip
al
ch
ar
ac
ter
is
tics
a
n
d
d
if
f
er
e
n
ce
s
,
an
d
th
e
s
ec
u
r
it
y
i
m
p
ac
t
o
f
th
eir
u
ti
lizatio
n
.
W
e
in
itiall
y
s
tu
d
ied
th
e
h
is
t
o
r
y
o
f
t
h
e
v
ir
t
u
al
m
ac
h
in
e
s
,
f
o
llo
w
in
g
th
e
ir
ev
o
lu
tio
n
f
r
o
m
th
e
o
r
ig
i
n
s
,
in
1
9
6
0
s
u
n
til
n
o
w
ad
a
y
s
w
it
h
i
ts
i
m
p
le
m
en
ta
tio
n
in
t
h
e
x
8
6
ar
ch
itect
u
r
e.
W
e
also
p
r
esen
ted
t
h
e
d
i
f
f
er
e
n
t
co
m
p
o
n
e
n
ts
o
f
v
ir
tu
a
lizatio
n
,
f
o
cu
s
i
n
g
o
n
th
e
p
r
o
b
lem
o
f
th
e
x
8
6
ar
ch
itect
u
r
e
th
a
t
n
at
iv
el
y
d
id
n
o
t
s
u
p
p
o
r
t
v
ir
tu
a
l
izatio
n
an
d
h
o
w
s
o
m
e
v
ir
tu
aliza
tio
n
s
o
f
t
w
ar
e
co
m
p
a
n
ies
w
o
r
k
ed
ar
o
u
n
d
th
i
s
p
r
o
b
lem
.
W
e
h
a
v
e
m
ad
e
a
s
tu
d
y
ab
o
u
t
t
h
e
c
u
r
r
en
t
s
tate
o
f
ar
t
o
f
th
e
m
ain
s
er
v
er
v
ir
t
u
aliza
tio
n
p
r
o
d
u
cts,
d
escr
ib
in
g
t
h
eir
p
r
in
cip
al
ch
ar
ac
ter
is
tics
a
n
d
s
y
s
te
m
s
s
u
p
p
o
r
ted
.
T
h
e
u
s
e
o
f
v
ir
t
u
aliza
tio
n
b
r
in
g
s
m
a
n
y
ad
v
an
ta
g
e
s
,
s
u
c
h
as
r
ed
u
ctio
n
o
f
th
e
h
ar
d
w
ar
e
r
eso
u
r
ce
s
n
ee
d
ed
w
it
h
d
ir
ec
t
i
m
p
ac
t
o
n
co
s
t
ef
f
icie
n
c
y
,
b
u
t
also
s
ec
u
r
it
y
ad
v
an
tag
e
s
.
T
h
e
latter
b
en
ef
it
is
co
m
m
o
n
l
y
u
s
ed
to
s
p
r
ea
d
th
e
w
o
r
d
o
n
v
ir
tu
a
lizatio
n
,
b
u
t
w
e
w
a
n
ted
to
d
em
y
s
ti
f
y
t
h
i
s
m
y
t
h
,
p
r
esen
ti
n
g
s
o
m
e
o
f
t
h
e
s
ec
u
r
it
y
p
r
o
b
lem
s
th
at
s
er
v
er
v
ir
tu
aliza
tio
n
b
r
o
u
g
h
t
a
n
d
th
eir
i
m
p
ac
t.
W
e
ch
o
o
s
e
t
w
o
o
f
th
e
m
ain
s
er
v
er
v
ir
tu
a
lizatio
n
p
r
o
d
u
cts
co
m
m
o
n
l
y
u
s
ed
b
y
co
m
p
a
n
ies
a
n
d
u
n
iv
er
s
itie
s
an
d
co
n
d
u
cted
a
v
u
ln
er
ab
ilit
y
a
n
al
y
s
i
s
,
u
s
i
n
g
as
r
ef
er
e
n
ce
t
h
e
C
VE
s
r
ep
o
r
ted
.
T
h
e
co
n
clu
s
io
n
f
r
o
m
th
at
a
n
al
y
s
i
s
i
s
t
h
at
b
o
th
p
r
o
d
u
cts
s
h
o
w
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