<s>
IPVS	B-Operating_System
(	O
IP	B-Operating_System
Virtual	I-Operating_System
Server	I-Operating_System
)	O
implements	O
transport-layer	B-Architecture
load	B-Application
balancing	I-Application
,	O
usually	O
called	O
Layer	B-Architecture
4	I-Architecture
LAN	B-Protocol
switching	I-Protocol
,	O
as	O
part	O
of	O
the	O
Linux	B-Operating_System
kernel	I-Operating_System
.	O
</s>
<s>
IPVS	B-Operating_System
is	O
incorporated	O
into	O
the	O
Linux	B-Operating_System
Virtual	I-Operating_System
Server	I-Operating_System
(	O
LVS	O
)	O
,	O
where	O
it	O
runs	O
on	O
a	O
host	O
and	O
acts	O
as	O
a	O
load	B-Application
balancer	I-Application
in	O
front	O
of	O
a	O
cluster	O
of	O
real	O
servers	O
.	O
</s>
<s>
IPVS	B-Operating_System
can	O
direct	O
requests	O
for	O
TCP	O
-	O
and	O
UDP-based	O
services	O
to	O
the	O
real	O
servers	O
,	O
and	O
make	O
services	O
of	O
the	O
real	O
servers	O
appear	O
as	O
virtual	O
services	O
on	O
a	O
single	O
IP	B-Protocol
address	I-Protocol
.	O
</s>
<s>
IPVS	B-Operating_System
is	O
built	O
on	O
top	O
of	O
the	O
Netfilter	B-Application
.	O
</s>
<s>
IPVS	B-Operating_System
is	O
merged	O
into	O
versions	O
2.4.x	O
and	O
newer	O
of	O
the	O
Linux	B-Operating_System
kernel	I-Operating_System
mainline	O
.	O
</s>
