<s>
A	O
network	B-Protocol
operating	I-Protocol
system	I-Protocol
(	O
NOS	O
)	O
is	O
a	O
specialized	O
operating	B-General_Concept
system	I-General_Concept
for	O
a	O
network	O
device	O
such	O
as	O
a	O
router	B-Protocol
,	O
switch	B-Protocol
or	O
firewall	B-Application
.	O
</s>
<s>
Historically	O
operating	B-General_Concept
systems	I-General_Concept
with	O
networking	O
capabilities	O
were	O
described	O
as	O
network	B-Protocol
operating	I-Protocol
systems	I-Protocol
,	O
because	O
they	O
allowed	O
personal	B-Device
computers	I-Device
(	O
PCs	B-Device
)	O
to	O
participate	O
in	O
computer	B-Architecture
networks	I-Architecture
and	O
shared	B-General_Concept
file	I-General_Concept
and	I-General_Concept
printer	I-General_Concept
access	I-General_Concept
within	O
a	O
local	B-General_Concept
area	I-General_Concept
network	I-General_Concept
(	O
LAN	B-General_Concept
)	O
.	O
</s>
<s>
This	O
description	O
of	O
operating	B-General_Concept
systems	I-General_Concept
is	O
now	O
largely	O
historical	O
,	O
as	O
common	O
operating	B-General_Concept
systems	I-General_Concept
include	O
a	O
network	B-Protocol
stack	I-Protocol
to	O
support	O
a	O
client	B-Operating_System
–	I-Operating_System
server	I-Operating_System
model	I-Operating_System
.	O
</s>
<s>
Early	O
microcomputer	O
operating	B-General_Concept
systems	I-General_Concept
such	O
as	O
CP/M	B-Application
,	O
MS-DOS	B-Application
and	O
classic	B-Application
Mac	I-Application
OS	I-Application
were	O
designed	O
for	O
one	O
user	O
on	O
one	O
computer	O
.	O
</s>
<s>
Packet	B-Protocol
switching	I-Protocol
networks	O
were	O
developed	O
to	O
share	O
hardware	O
resources	O
,	O
such	O
as	O
a	O
mainframe	B-Architecture
computer	I-Architecture
,	O
a	O
printer	O
or	O
a	O
large	O
and	O
expensive	O
hard	B-Device
disk	I-Device
.	O
</s>
<s>
As	O
local	B-General_Concept
area	I-General_Concept
network	I-General_Concept
technology	O
became	O
available	O
,	O
two	O
general	O
approaches	O
to	O
handle	O
sharing	O
of	O
resources	O
on	O
networks	O
arose	O
.	O
</s>
<s>
Historically	O
a	O
network	B-Protocol
operating	I-Protocol
system	I-Protocol
was	O
an	O
operating	B-General_Concept
system	I-General_Concept
for	O
a	O
computer	O
which	O
implemented	O
network	O
capabilities	O
.	O
</s>
<s>
Operating	B-General_Concept
systems	I-General_Concept
with	O
a	O
network	B-Protocol
stack	I-Protocol
allowed	O
personal	B-Device
computers	I-Device
to	O
participate	O
in	O
a	O
client-server	B-Operating_System
architecture	I-Operating_System
in	O
which	O
a	O
server	B-Application
enables	O
multiple	O
clients	O
to	O
share	O
resources	O
,	O
such	O
as	O
printers	O
.	O
</s>
<s>
Early	O
examples	O
of	O
client-server	B-Operating_System
operating	B-General_Concept
systems	I-General_Concept
that	O
were	O
shipped	O
with	O
fully	O
integrated	O
network	O
capabilities	O
are	O
Novell	B-Operating_System
NetWare	I-Operating_System
using	O
the	O
Internetwork	B-Protocol
Packet	I-Protocol
Exchange	I-Protocol
(	O
IPX	B-Protocol
)	O
network	O
protocol	O
and	O
Banyan	B-Operating_System
VINES	I-Operating_System
which	O
used	O
a	O
variant	O
of	O
the	O
Xerox	B-Protocol
Network	I-Protocol
Systems	I-Protocol
(	O
XNS	O
)	O
protocols	O
.	O
</s>
<s>
These	O
limited	O
client/server	B-Operating_System
networks	I-Operating_System
were	O
gradually	O
replaced	O
by	O
Peer-to-peer	O
networks	O
,	O
which	O
used	O
networking	O
capabilities	O
to	O
share	O
resources	O
and	O
files	O
located	O
on	O
a	O
variety	O
of	O
computers	O
of	O
all	O
sizes	O
.	O
</s>
<s>
The	O
most	O
popular	O
peer-to-peer	O
networks	O
as	O
of	O
2020	O
are	O
Ethernet	O
,	O
Wi-Fi	O
and	O
the	O
Internet	B-Protocol
protocol	I-Protocol
suite	I-Protocol
.	O
</s>
<s>
Software	O
that	O
allowed	O
users	O
to	O
interact	O
with	O
these	O
networks	O
,	O
despite	O
a	O
lack	O
of	O
networking	O
support	O
in	O
the	O
underlying	O
manufacturer	O
's	O
operating	B-General_Concept
system	I-General_Concept
,	O
was	O
sometimes	O
called	O
a	O
network	B-Protocol
operating	I-Protocol
system	I-Protocol
.	O
</s>
<s>
Examples	O
of	O
such	O
add-on	O
software	O
include	O
Phil	O
Karn	O
's	O
KA9Q	B-Protocol
NOS	I-Protocol
(	O
adding	O
Internet	O
support	O
to	O
CP/M	B-Application
and	O
MS-DOS	B-Application
)	O
,	O
PC/TCP	B-Application
Packet	I-Application
Drivers	I-Application
(	O
adding	O
Ethernet	O
and	O
Internet	O
support	O
to	O
MS-DOS	B-Application
)	O
,	O
and	O
LANtastic	B-Operating_System
(	O
for	O
MS-DOS	B-Application
,	O
Microsoft	B-Application
Windows	I-Application
and	O
OS/2	B-Application
)	O
,	O
and	O
Windows	O
for	O
Workgroups	O
(	O
adding	O
NetBIOS	O
to	O
Windows	O
)	O
.	O
</s>
<s>
Examples	O
of	O
early	O
operating	B-General_Concept
systems	I-General_Concept
with	O
peer-to-peer	O
networking	O
capabilities	O
built-in	O
include	O
MacOS	B-Application
(	O
using	O
AppleTalk	B-Application
and	O
LocalTalk	B-Device
)	O
,	O
and	O
the	O
Berkeley	B-Operating_System
Software	I-Operating_System
Distribution	I-Operating_System
.	O
</s>
<s>
Today	O
,	O
distributed	B-Architecture
computing	I-Architecture
and	O
groupware	B-Application
applications	O
have	O
become	O
the	O
norm	O
.	O
</s>
<s>
Computer	B-General_Concept
operating	I-General_Concept
systems	I-General_Concept
include	O
a	O
networking	B-Protocol
stack	I-Protocol
as	O
a	O
matter	O
of	O
course	O
.	O
</s>
<s>
Partly	O
because	O
it	O
allowed	O
for	O
multi-vendor	O
interoperability	O
,	O
and	O
could	O
route	O
packets	O
globally	O
rather	O
than	O
being	O
restricted	O
to	O
a	O
single	O
building	O
,	O
the	O
Internet	B-Protocol
protocol	I-Protocol
suite	I-Protocol
became	O
almost	O
universally	O
adopted	O
in	O
network	O
architectures	O
.	O
</s>
<s>
Thereafter	O
,	O
computer	B-General_Concept
operating	I-General_Concept
systems	I-General_Concept
and	O
the	O
firmware	B-Application
of	O
network	O
devices	O
tended	O
to	O
support	O
Internet	B-Protocol
protocols	I-Protocol
.	O
</s>
<s>
Network	B-Protocol
operating	I-Protocol
systems	I-Protocol
can	O
be	O
embedded	O
in	O
a	O
router	B-Protocol
or	O
hardware	B-Application
firewall	I-Application
that	O
operates	O
the	O
functions	O
in	O
the	O
network	B-Application
layer	I-Application
(	O
layer	B-Application
3	I-Application
)	O
.	O
</s>
<s>
Notable	O
network	B-Protocol
operating	I-Protocol
systems	I-Protocol
include	O
:	O
</s>
<s>
Cisco	B-Protocol
IOS	I-Protocol
,	O
a	O
family	O
of	O
network	B-Protocol
operating	I-Protocol
systems	I-Protocol
used	O
on	O
Cisco	O
Systems	O
routers	B-Protocol
and	O
network	B-Protocol
switches	I-Protocol
.	O
</s>
<s>
ONOS	B-Application
,	O
an	O
open	O
source	O
SDN	O
operating	B-General_Concept
system	I-General_Concept
(	O
hosted	O
by	O
Linux	B-Operating_System
Foundation	I-Operating_System
)	O
for	O
communications	O
service	O
providers	O
that	O
is	O
designed	O
for	O
scalability	O
,	O
high	O
performance	O
and	O
high	O
availability	O
.	O
</s>
