<s>
A	O
client	B-License
access	I-License
license	I-License
(	O
CAL	O
)	O
is	O
a	O
commercial	O
software	B-License
license	I-License
that	O
allows	O
client	B-Protocol
computers	I-Protocol
to	O
use	O
server	B-Application
software	I-Application
services	O
.	O
</s>
<s>
For	O
example	O
,	O
an	O
instance	O
of	O
Windows	B-Device
Server	I-Device
2016	I-Device
for	O
which	O
ten	O
User	O
CALs	O
are	O
purchased	O
allows	O
10	O
distinct	O
users	O
to	O
access	O
the	O
server	O
.	O
</s>
<s>
Commercial	O
server	B-Application
software	I-Application
,	O
such	O
as	O
Windows	B-Application
Server	I-Application
2003	I-Application
and	O
SQL	O
Server	O
2005	O
require	O
licenses	O
that	O
are	O
more	O
expensive	O
than	O
those	O
which	O
are	O
purchased	O
for	O
desktop	O
software	O
like	O
Windows	B-Application
Vista	I-Application
.	O
</s>
<s>
A	O
CAL	O
legally	O
permits	O
client	B-Protocol
computers	I-Protocol
to	O
connect	O
to	O
commercial	O
server	B-Application
software	I-Application
.	O
</s>
<s>
They	O
usually	O
come	O
in	O
the	O
form	O
of	O
a	O
certificate	B-License
of	I-License
authenticity	I-License
(	O
CoA	O
)	O
and	O
a	O
license	O
key	O
,	O
which	O
is	O
sometimes	O
attached	O
to	O
the	O
certificate	O
itself	O
.	O
</s>
<s>
The	O
various	O
editions	O
of	O
most	O
of	O
Microsoft	O
's	O
server	B-Application
software	I-Application
usually	O
include	O
a	O
small	O
number	O
of	O
CALs	O
,	O
and	O
this	O
allows	O
the	O
software	O
to	O
be	O
used	O
by	O
either	O
a	O
few	O
users	O
or	O
a	O
few	O
computers	O
,	O
depending	O
on	O
the	O
CAL	O
licensing	O
mode	O
.	O
</s>
<s>
Some	O
of	O
Microsoft	O
's	O
server	B-Application
software	I-Application
programs	O
do	O
not	O
require	O
CALs	O
at	O
all	O
,	O
as	O
is	O
the	O
case	O
of	O
Windows	O
Server	O
Web	O
Edition	O
.	O
</s>
<s>
Microsoft	B-Application
SQL	I-Application
Server	I-Application
can	O
be	O
licensed	O
for	O
CALs	O
,	O
or	O
alternatively	O
by	O
CPU	B-Device
cores	O
.	O
</s>
<s>
With	O
user	O
CALs	O
,	O
each	O
CAL	O
allows	O
one	O
user	O
to	O
connect	O
to	O
the	O
server	B-Application
software	I-Application
whenever	O
they	O
need	O
to	O
.	O
</s>
<s>
With	O
user	O
CALs	O
,	O
each	O
user	O
can	O
connect	O
to	O
the	O
server	B-Application
software	I-Application
from	O
any	O
number	O
of	O
devices	O
.	O
</s>
<s>
One	O
CAL	O
enables	O
one	O
device	O
to	O
connect	O
to	O
and	O
use	O
the	O
server	B-Application
software	I-Application
,	O
regardless	O
of	O
how	O
many	O
users	O
connect	O
from	O
that	O
particular	O
device	O
.	O
</s>
<s>
CALs	O
usually	O
enable	O
connectivity	O
to	O
server	B-Application
software	I-Application
regardless	O
of	O
the	O
edition	O
of	O
the	O
software	O
.	O
</s>
<s>
For	O
example	O
,	O
CALs	O
purchased	O
to	O
enable	O
client	O
connectivity	O
with	O
Windows	B-Application
Server	I-Application
2003	I-Application
Enterprise	O
Edition	O
can	O
be	O
used	O
with	O
Windows	B-Application
Server	I-Application
2003	I-Application
Datacenter	O
Edition	O
.	O
</s>
<s>
For	O
example	O
,	O
Windows	O
Server	O
2012	O
CALs	O
can	O
not	O
only	O
be	O
used	O
to	O
access	O
servers	O
running	O
on	O
Windows	O
Server	O
2012	O
,	O
but	O
they	O
can	O
be	O
used	O
to	O
access	O
one	O
of	O
the	O
servers	O
running	O
Windows	O
Server	O
2008	O
,	O
Windows	O
Server	O
2008	O
R2	O
,	O
Windows	B-Application
Server	I-Application
2003	I-Application
and	O
any	O
previous	O
versions	O
at	O
any	O
given	O
time	O
.	O
</s>
<s>
Terminal	B-Protocol
Services	I-Protocol
is	O
a	O
function	O
of	O
Microsoft	O
Windows	O
that	O
allows	O
several	O
types	O
of	O
connections	O
to	O
the	O
server	O
components	O
of	O
the	O
system	O
.	O
</s>
<s>
Windows	O
Server	O
versions	O
prior	O
to	O
2003	O
do	O
not	O
necessarily	O
require	O
the	O
use	O
of	O
specialized	O
Terminal	B-Protocol
Services	I-Protocol
CALs	O
;	O
rather	O
,	O
clients	O
which	O
are	O
of	O
at	O
least	O
the	O
same	O
or	O
lower	O
version	O
of	O
the	O
operating	O
system	O
are	O
allowed	O
access	O
automatically	O
.	O
</s>
<s>
For	O
example	O
,	O
Windows	O
NT	O
4.0	O
clients	O
may	O
connect	O
to	O
Windows	O
NT	O
4.0	O
terminal	O
servers	O
but	O
not	O
Windows	B-Application
2000	I-Application
or	O
later	O
;	O
Windows	B-Application
2000	I-Application
or	O
Windows	O
XP	O
clients	O
may	O
connect	O
to	O
Windows	O
NT	O
4.0	O
or	O
Windows	B-Application
2000	I-Application
terminal	O
servers	O
.	O
</s>
<s>
The	O
system	O
for	O
enforcing	O
the	O
number	O
of	O
TS	O
CALs	O
(	O
"	O
Microsoft	O
Enforced	O
Licensing	O
"	O
)	O
used	O
on	O
versions	O
later	O
than	O
NT	O
was	O
abused	O
by	O
the	O
"	O
FLAME	O
"	O
malware	O
,	O
leading	O
to	O
a	O
patch	O
in	O
2012	O
restricting	O
the	O
Certificate	O
Creation	O
system	O
used	O
for	O
Terminal	B-Protocol
Services	I-Protocol
.	O
</s>
