<s>
The	O
Internet	B-Protocol
Content	I-Protocol
Adaptation	I-Protocol
Protocol	I-Protocol
(	O
ICAP	O
)	O
is	O
a	O
lightweight	O
HTTP-like	O
protocol	O
specified	O
in	O
which	O
is	O
used	O
to	O
extend	O
transparent	O
proxy	B-Application
servers	I-Application
,	O
thereby	O
freeing	O
up	O
resources	O
and	O
standardizing	O
the	O
way	O
in	O
which	O
new	O
features	O
are	O
implemented	O
.	O
</s>
<s>
ICAP	O
is	O
generally	O
used	O
to	O
implement	O
virus	B-Application
scanning	I-Application
and	O
content	B-Protocol
filters	I-Protocol
in	O
transparent	O
HTTP	B-Protocol
proxy	O
caches	O
.	O
</s>
<s>
Content	O
adaptation	O
refers	O
to	O
performing	O
the	O
particular	O
value	O
added	O
service	O
(	O
content	O
manipulation	O
)	O
for	O
the	O
associated	O
client	B-Protocol
request/response	O
.	O
</s>
<s>
At	O
the	O
core	O
of	O
this	O
process	B-Operating_System
is	O
a	O
cache	O
that	O
will	O
proxy	O
all	O
client	B-Protocol
transactions	O
and	O
will	O
process	B-Operating_System
them	O
through	O
web	B-Application
servers	I-Application
.	O
</s>
<s>
These	O
ICAP	O
servers	O
are	O
focused	O
on	O
a	O
specific	O
function	O
,	O
for	O
example	O
,	O
ad	O
insertion	O
,	O
virus	B-Application
scanning	I-Application
,	O
multi-AV	O
scanning	O
,	O
content	O
translation	O
,	O
language	O
translation	O
,	O
or	O
content	B-Protocol
filtering	I-Protocol
.	O
</s>
<s>
Off-loading	O
value-added	O
services	O
from	O
web	B-Application
servers	I-Application
to	O
ICAP	O
servers	O
allows	O
those	O
same	O
web	B-Application
servers	I-Application
to	O
be	O
scaled	O
according	O
to	O
raw	O
HTTP	B-Protocol
throughput	O
versus	O
having	O
to	O
handle	O
these	O
extra	O
tasks	O
.	O
</s>
<s>
To	O
support	O
all	O
3	O
content	O
encodings	O
(	O
content-length	O
,	O
chunked	O
,	O
and	O
TCP-close	O
)	O
in	O
HTTP	B-Protocol
1.1	I-Protocol
.	O
</s>
<s>
To	O
provide	O
a	O
feature	O
called	O
"	O
content	O
preview	O
"	O
that	O
allowed	O
the	O
ICAP	O
server	O
to	O
look	O
at	O
the	O
first	O
few	O
hundred	O
bytes	O
of	O
content	O
before	O
deciding	O
to	O
process	B-Operating_System
the	O
content	O
or	O
not	O
.	O
</s>
<s>
This	O
was	O
implemented	O
by	O
embedding	O
the	O
preview	O
argument	O
size	O
in	O
the	O
ICAP	O
webserver	B-Application
URL	O
when	O
configured	O
on	O
the	O
ICAP	O
client	B-Protocol
.	O
</s>
<s>
Gillies	O
prototyped	O
the	O
first	O
ICAP	O
client	B-Protocol
and	O
server	O
for	O
the	O
NetCache	B-Protocol
series	O
of	O
internet	O
caches	O
in	O
mid-2000	O
(	O
known	O
as	O
ICAP	O
0.9	O
protocol	O
)	O
and	O
produced	O
training	O
materials	O
for	O
vendors	O
.	O
</s>
<s>
The	O
client	B-Protocol
was	O
written	O
in	O
C++	O
in	O
the	O
core	O
of	O
the	O
NetCache	B-Protocol
server	O
,	O
and	O
the	O
demonstration	O
ICAP	O
Server	O
was	O
written	O
in	O
Perl	O
and	O
employed	O
the	O
Debian	O
word-replacement	O
filters	O
to	O
rewrite	O
web	O
pages	O
,	O
skipping	O
over	O
the	O
HTML	O
tags	O
,	O
and	O
translating	O
web	O
pages	O
into	O
Swedish	O
Chef	O
or	O
Jive	O
in	O
real	O
time	O
.	O
</s>
