<s>
An	O
application	B-Protocol
delivery	I-Protocol
controller	I-Protocol
(	O
ADC	O
)	O
is	O
a	O
computer	B-Architecture
network	I-Architecture
device	O
in	O
a	O
datacenter	B-Operating_System
,	O
often	O
part	O
of	O
an	O
application	B-General_Concept
delivery	I-General_Concept
network	I-General_Concept
(	O
ADN	O
)	O
,	O
that	O
helps	O
perform	O
common	O
tasks	O
,	O
such	O
as	O
those	O
done	O
by	O
web	B-Application
accelerators	I-Application
to	O
remove	O
load	O
from	O
the	O
web	B-Application
servers	I-Application
themselves	O
.	O
</s>
<s>
Many	O
also	O
provide	O
load	B-Application
balancing	I-Application
.	O
</s>
<s>
ADCs	O
are	O
often	O
placed	O
in	O
the	O
DMZ	B-General_Concept
,	O
between	O
the	O
outer	O
firewall	B-Application
or	O
router	O
and	O
a	O
web	B-Operating_System
farm	I-Operating_System
.	O
</s>
<s>
An	O
Application	B-Protocol
Delivery	I-Protocol
Controller	I-Protocol
(	O
ADC	O
)	O
is	O
a	O
type	O
of	O
server	O
that	O
provides	O
a	O
variety	O
of	O
services	O
designed	O
to	O
optimize	O
the	O
distribution	O
of	O
load	O
being	O
handled	O
by	O
backend	O
content	O
servers	O
.	O
</s>
<s>
An	O
ADC	O
directs	O
web	O
request	O
traffic	O
to	O
optimal	O
data	O
sources	O
in	O
order	O
to	O
remove	O
unnecessary	O
load	O
from	O
web	B-Application
servers	I-Application
.	O
</s>
<s>
ADCs	O
are	O
intended	O
to	O
be	O
deployed	O
within	O
the	O
DMZ	B-General_Concept
of	O
a	O
computer	O
server	O
cluster	O
hosting	O
web	O
applications	O
and/or	O
services	O
.	O
</s>
<s>
In	O
this	O
sense	O
,	O
an	O
ADC	O
can	O
be	O
envisioned	O
as	O
a	O
drop-in	O
load	B-Application
balancer	I-Application
replacement	O
.	O
</s>
<s>
In	O
the	O
case	O
of	O
static	O
objects	O
,	O
the	O
ADC	O
may	O
serve	O
the	O
object	O
directly	O
from	O
its	O
own	O
internal	O
cache	B-General_Concept
or	O
direct	O
it	O
to	O
a	O
dedicated	O
static	O
object	O
repository	O
.	O
</s>
<s>
Starting	O
around	O
2004	O
,	O
first	O
generation	O
ADCs	O
offered	O
simple	O
application	O
acceleration	O
and	O
load	B-Application
balancing	I-Application
.	O
</s>
<s>
In	O
2006	O
,	O
ADCs	O
began	O
to	O
mature	O
when	O
they	O
began	O
featuring	O
advanced	O
applications	O
services	O
such	O
as	O
compression	B-General_Concept
,	O
caching	B-General_Concept
,	O
connection	B-Architecture
multiplexing	I-Architecture
,	O
traffic	O
shaping	O
,	O
application	B-Protocol
layer	I-Protocol
security	I-Protocol
,	O
SSL	B-Protocol
offload	I-Protocol
,	O
and	O
content	O
switching	O
,	O
combined	O
with	O
services	O
like	O
server	B-Application
load	I-Application
balancing	I-Application
in	O
an	O
integrated	O
services	O
framework	O
that	O
optimized	O
and	O
secured	O
business	O
critical	O
application	O
flows	O
.	O
</s>
<s>
Until	O
leaving	O
the	O
market	O
in	O
2012	O
,	O
Cisco	O
Systems	O
offered	O
application	B-Protocol
delivery	I-Protocol
controllers	I-Protocol
.	O
</s>
<s>
Market	O
leaders	O
like	O
F5	O
Networks	O
,	O
Radware	B-Protocol
,	O
and	O
Citrix	B-Application
had	O
been	O
gaining	O
market	O
share	O
from	O
Cisco	O
in	O
previous	O
years	O
.	O
</s>
<s>
Both	O
types	O
of	O
devices	O
improve	O
performance	O
,	O
but	O
the	O
latter	O
is	O
usually	O
more	O
aware	O
of	O
optimization	O
strategies	O
that	O
work	O
best	O
with	O
a	O
particular	O
application	O
framework	O
,	O
focusing	O
on	O
ASP.NET	B-Application
or	O
AJAX	B-Device
applications	O
,	O
for	O
example	O
.	O
</s>
