<s>
OpenFlow	B-Protocol
is	O
a	O
communications	O
protocol	O
that	O
gives	O
access	O
to	O
the	O
forwarding	B-Protocol
plane	I-Protocol
of	O
a	O
network	B-Protocol
switch	I-Protocol
or	O
router	B-Protocol
over	O
the	O
network	O
.	O
</s>
<s>
OpenFlow	B-Protocol
enables	O
network	O
controllers	O
to	O
determine	O
the	O
path	O
of	O
network	O
packets	O
across	O
a	O
network	O
of	O
switches	O
.	O
</s>
<s>
Also	O
,	O
OpenFlow	B-Protocol
allows	O
switches	O
from	O
different	O
vendors	O
—	O
often	O
each	O
with	O
their	O
own	O
proprietary	O
interfaces	O
and	O
scripting	O
languages	O
—	O
to	O
be	O
managed	O
remotely	O
using	O
a	O
single	O
,	O
open	O
protocol	O
.	O
</s>
<s>
The	O
protocol	O
's	O
inventors	O
consider	O
OpenFlow	B-Protocol
an	O
enabler	O
of	O
software-defined	O
networking	O
(	O
SDN	O
)	O
.	O
</s>
<s>
OpenFlow	B-Protocol
allows	O
remote	O
administration	O
of	O
a	O
layer	B-Application
3	I-Application
switch	O
's	O
packet	O
forwarding	O
tables	O
,	O
by	O
adding	O
,	O
modifying	O
and	O
removing	O
packet	O
matching	O
rules	O
and	O
actions	O
.	O
</s>
<s>
The	O
OpenFlow	B-Protocol
protocol	O
is	O
layered	O
on	O
top	O
of	O
the	O
Transmission	B-Protocol
Control	I-Protocol
Protocol	I-Protocol
(	O
TCP	O
)	O
and	O
prescribes	O
the	O
use	O
of	O
Transport	B-Protocol
Layer	I-Protocol
Security	I-Protocol
(	O
TLS	O
)	O
.	O
</s>
<s>
Earlier	O
versions	O
of	O
the	O
OpenFlow	B-Protocol
protocol	O
unofficially	O
used	O
port	O
6633	O
.	O
</s>
<s>
Some	O
network	O
control	B-Protocol
plane	I-Protocol
implementations	O
use	O
the	O
protocol	O
to	O
manage	O
the	O
network	O
forwarding	O
elements	O
.	O
</s>
<s>
OpenFlow	B-Protocol
is	O
mainly	O
used	O
between	O
the	O
switch	O
and	O
controller	O
on	O
a	O
secure	O
channel	O
.	O
</s>
<s>
The	O
Open	O
Networking	O
Foundation	O
(	O
ONF	O
)	O
,	O
a	O
user-led	O
organization	O
dedicated	O
to	O
promotion	O
and	O
adoption	O
of	O
software-defined	O
networking	O
(	O
SDN	O
)	O
,	O
manages	O
the	O
OpenFlow	B-Protocol
standard	O
.	O
</s>
<s>
ONF	O
defines	O
OpenFlow	B-Protocol
as	O
the	O
first	O
standard	O
communications	O
interface	O
defined	O
between	O
the	O
control	O
and	O
forwarding	O
layers	O
of	O
an	O
SDN	O
architecture	O
.	O
</s>
<s>
OpenFlow	B-Protocol
allows	O
direct	O
access	O
to	O
and	O
manipulation	O
of	O
the	O
forwarding	B-Protocol
plane	I-Protocol
of	O
network	O
devices	O
such	O
as	O
switches	O
and	O
routers	B-Protocol
,	O
both	O
physical	O
and	O
virtual	O
(	O
hypervisor-based	O
)	O
.	O
</s>
<s>
It	O
is	O
the	O
absence	O
of	O
an	O
open	O
interface	O
to	O
the	O
forwarding	B-Protocol
plane	I-Protocol
that	O
has	O
led	O
to	O
the	O
characterization	O
of	O
today	O
's	O
networking	O
devices	O
as	O
monolithic	O
,	O
closed	O
,	O
and	O
mainframe-like	O
.	O
</s>
<s>
A	O
protocol	O
like	O
OpenFlow	B-Protocol
is	O
needed	O
to	O
move	O
network	O
control	O
out	O
of	O
proprietary	O
network	B-Protocol
switches	I-Protocol
and	O
into	O
control	O
software	O
that	O
's	O
open	O
source	O
and	O
locally	O
managed	O
.	O
</s>
<s>
A	O
number	O
of	O
network	B-Protocol
switch	I-Protocol
and	O
router	B-Protocol
vendors	O
announced	O
intent	O
to	O
support	O
or	O
are	O
shipping	O
supported	O
switches	O
for	O
OpenFlow	B-Protocol
,	O
including	O
Alcatel-Lucent	O
,	O
Big	O
Switch	O
Networks	O
,	O
Brocade	O
Communications	O
,	O
and	O
Radisys	O
among	O
others	O
.	O
</s>
<s>
Version	O
1.1	O
of	O
the	O
OpenFlow	B-Protocol
protocol	O
was	O
released	O
on	O
28	O
February	O
2011	O
,	O
and	O
new	O
development	O
of	O
the	O
standard	O
was	O
managed	O
by	O
the	O
ONF	O
.	O
</s>
<s>
In	O
December	O
2011	O
,	O
the	O
ONF	O
board	O
approved	O
OpenFlow	B-Protocol
version	O
1.2	O
and	O
published	O
it	O
in	O
February	O
2012	O
.	O
</s>
<s>
The	O
current	O
version	O
of	O
OpenFlow	B-Protocol
is	O
1.5.1	O
.	O
</s>
<s>
In	O
May	O
2011	O
,	O
Marvell	O
and	O
Larch	O
Networks	O
announced	O
the	O
availability	O
of	O
an	O
OpenFlow-enabled	O
,	O
fully	O
featured	O
switching	O
solution	O
based	O
on	O
Marvell	O
's	O
networking	O
control	O
stack	O
and	O
the	O
Prestera	O
family	O
of	O
packet	B-Protocol
processors	I-Protocol
.	O
</s>
<s>
Indiana	O
University	O
in	O
May	O
2011	O
launched	O
a	O
SDN	O
Interoperability	O
Lab	O
in	O
conjunction	O
with	O
the	O
ONF	O
to	O
test	O
how	O
well	O
different	O
vendors	O
 '	O
software-defined	O
networking	O
and	O
OpenFlow	B-Protocol
products	O
work	O
together	O
.	O
</s>
<s>
In	O
June	O
2012	O
,	O
Infoblox	O
released	O
LINC	O
,	O
an	O
open-source	B-Application
OpenFlow	B-Protocol
version	O
1.2	O
and	O
1.3	O
compliant	O
software	O
switch	O
.	O
</s>
<s>
In	O
February	O
2012	O
,	O
Big	O
Switch	O
Networks	O
released	O
Project	O
Floodlight	O
,	O
an	O
Apache-licensed	B-Application
open-source	B-Application
software	I-Application
OpenFlow	B-Protocol
Controller	O
,	O
and	O
announced	O
its	O
OpenFlow-based	O
SDN	O
Suite	O
in	O
November	O
of	O
that	O
year	O
,	O
which	O
contains	O
a	O
commercial	O
controller	O
,	O
and	O
virtual	O
switching	O
and	O
tap	O
monitoring	O
applications	O
.	O
</s>
<s>
In	O
February	O
2012	O
,	O
HP	B-Device
said	O
it	O
is	O
supporting	O
the	O
standard	O
on	O
16	O
of	O
its	O
Ethernet	B-Protocol
switch	I-Protocol
products	O
.	O
</s>
<s>
In	O
April	O
2012	O
,	O
Google	B-Application
's	I-Application
Urs	O
Hölzle	O
described	O
how	O
the	O
company	O
's	O
internal	O
network	O
had	O
been	O
completely	O
re-designed	O
over	O
the	O
previous	O
two	O
years	O
to	O
run	O
under	O
OpenFlow	B-Protocol
with	O
substantial	O
efficiency	O
improvement	O
.	O
</s>
<s>
In	O
January	O
2013	O
,	O
NEC	O
unveiled	O
a	O
virtual	O
switch	O
for	O
Microsoft	O
's	O
Windows	B-Device
Server	I-Device
2012	I-Device
Hyper-V	O
hypervisor	B-Operating_System
,	O
which	O
is	O
designed	O
to	O
bring	O
OpenFlow-based	O
software-defined	O
networking	O
and	O
network	O
virtualisation	O
to	O
those	O
Microsoft	O
environments	O
.	O
</s>
