<s>
Linux	B-Operating_System
Virtual	I-Operating_System
Server	I-Operating_System
(	O
LVS	O
)	O
is	O
load	B-Application
balancing	I-Application
software	O
for	O
Linux	B-Operating_System
kernelbased	O
operating	O
systems	O
.	O
</s>
<s>
LVS	O
is	O
a	O
free	B-License
and	I-License
open-source	I-License
project	O
started	O
by	O
Wensong	O
Zhang	O
in	O
May	O
1998	O
,	O
subject	O
to	O
the	O
requirements	O
of	O
the	O
GNU	B-License
General	I-License
Public	I-License
License	I-License
(	O
GPL	B-License
)	O
,	O
version	O
2	O
.	O
</s>
<s>
The	O
mission	O
of	O
the	O
project	O
is	O
to	O
build	O
a	O
high-performance	O
and	O
highly	B-General_Concept
available	I-General_Concept
server	O
for	O
Linux	B-Operating_System
using	O
clustering	B-Architecture
technology	O
,	O
which	O
provides	O
good	O
scalability	O
,	O
reliability	O
and	O
serviceability	O
.	O
</s>
<s>
The	O
major	O
work	O
of	O
the	O
LVS	O
project	O
is	O
now	O
to	O
develop	O
advanced	O
IP	O
load	B-Application
balancing	I-Application
software	O
(	O
IPVS	B-Operating_System
)	O
,	O
application-level	O
load	B-Application
balancing	I-Application
software	O
(	O
KTCPVS	O
)	O
,	O
and	O
cluster	O
management	O
components	O
.	O
</s>
<s>
IPVS	B-Operating_System
:	O
an	O
advanced	O
IP	O
load	B-Application
balancing	I-Application
software	O
implemented	O
inside	O
the	O
Linux	B-Operating_System
kernel	I-Operating_System
.	O
</s>
<s>
The	O
IP	B-Operating_System
Virtual	I-Operating_System
Server	I-Operating_System
code	O
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>
<s>
KTCPVS	O
:	O
implements	O
application-level	O
load	B-Application
balancing	I-Application
inside	O
the	O
Linux	B-Operating_System
kernel	I-Operating_System
,	O
still	O
under	O
development	O
.	O
</s>
<s>
LVS	O
can	O
be	O
used	O
for	O
building	O
highly	O
scalable	O
and	O
highly	B-General_Concept
available	I-General_Concept
network	O
services	O
,	O
such	O
as	O
web	O
,	O
email	O
,	O
media	O
and	O
VoIP	B-Application
services	O
,	O
and	O
integrating	O
scalable	O
network	O
services	O
into	O
large-scale	O
reliable	O
e-commerce	O
or	O
e-government	O
applications	O
.	O
</s>
<s>
The	O
LVS	O
components	O
depend	O
upon	O
the	O
Linux	B-Operating_System
Netfilter	B-Application
framework	O
,	O
and	O
its	O
source	O
code	O
is	O
available	O
in	O
the	O
net/netfilter/ipvs	O
subdirectory	O
within	O
the	O
Linux	B-Operating_System
kernel	I-Operating_System
source	O
.	O
</s>
<s>
LVS	O
is	O
able	O
to	O
handle	O
UDP	O
,	O
TCP	B-Protocol
layer-4	O
protocols	O
as	O
well	O
as	O
FTP	O
passive	O
connection	O
by	O
inspecting	O
layer-7	O
packets	O
.	O
</s>
<s>
The	O
userland	O
utility	O
program	O
used	O
to	O
configure	O
LVS	O
is	O
called	O
ipvsadm	B-Operating_System
,	O
which	O
requires	O
superuser	B-Application
privileges	O
to	O
run	O
.	O
</s>
<s>
Setting	O
up	O
a	O
virtual	O
HTTP	B-Protocol
server	O
with	O
two	O
real	O
servers	O
:	O
</s>
<s>
The	O
first	O
command	O
assigns	O
TCP	B-Protocol
port	O
80	O
on	O
IP	B-Protocol
address	I-Protocol
192.168.0.1	B-Protocol
to	O
the	O
virtual	O
server	O
.	O
</s>
<s>
The	O
chosen	O
scheduling	O
algorithm	O
for	O
load	B-Application
balancing	I-Application
is	O
round-robin	B-Algorithm
(	O
-s	O
rr	O
)	O
.	O
</s>
<s>
The	O
second	O
and	O
third	O
commands	O
are	O
adding	O
IP	B-Protocol
addresses	I-Protocol
of	O
real	O
servers	O
to	O
the	O
LVS	O
setup	O
.	O
</s>
