<s>
IPX/SPX	B-Protocol
stands	O
for	O
Internetwork	O
Packet	O
Exchange/Sequenced	O
Packet	O
Exchange	O
.	O
</s>
<s>
IPX	B-Protocol
and	O
SPX	B-Protocol
are	O
networking	O
protocols	O
used	O
initially	O
on	O
networks	O
using	O
the	O
(	O
since	O
discontinued	O
)	O
Novell	B-Operating_System
NetWare	I-Operating_System
operating	B-General_Concept
systems	I-General_Concept
.	O
</s>
<s>
They	O
also	O
became	O
widely	O
used	O
on	O
networks	O
deploying	O
Microsoft	B-Application
Windows	I-Application
LANS	B-General_Concept
,	O
as	O
they	O
replaced	O
NetWare	B-Operating_System
LANS	B-General_Concept
,	O
but	O
are	O
no	O
longer	O
widely	O
used	O
.	O
</s>
<s>
IPX/SPX	B-Protocol
was	O
also	O
widely	O
used	O
prior	O
to	O
and	O
up	O
to	O
Windows	B-Application
XP	O
,	O
which	O
supported	O
the	O
protocols	O
,	O
while	O
later	O
Windows	B-Application
versions	O
do	O
not	O
,	O
and	O
TCP/IP	B-Protocol
took	O
over	O
for	O
networking	O
.	O
</s>
<s>
IPX	B-Protocol
and	O
SPX	B-Protocol
are	O
derived	O
from	O
Xerox	B-Protocol
Network	I-Protocol
Systems	I-Protocol
 '	O
IDP	O
and	O
SPP	O
protocols	O
respectively	O
.	O
</s>
<s>
IPX	B-Protocol
is	O
a	O
network-layer	B-Application
protocol	O
(	O
layer3	O
of	O
the	O
OSI	O
model	O
)	O
,	O
while	O
SPX	B-Protocol
is	O
a	O
transport-layer	B-Architecture
protocol	I-Architecture
(	O
layer4	O
of	O
the	O
OSI	O
model	O
)	O
.	O
</s>
<s>
The	O
SPX	B-Protocol
layer	O
sits	O
on	O
top	O
of	O
the	O
IPX	B-Protocol
layer	O
and	O
provides	O
connection-oriented	O
services	O
between	O
two	O
nodes	O
on	O
the	O
network	O
.	O
</s>
<s>
SPX	B-Protocol
is	O
used	O
primarily	O
by	O
client	B-Operating_System
–	I-Operating_System
server	I-Operating_System
applications	O
.	O
</s>
<s>
IPX	B-Protocol
and	O
SPX	B-Protocol
both	O
provide	O
connection	O
services	O
similar	O
to	O
TCP/IP	B-Protocol
,	O
with	O
the	O
IPX	B-Protocol
protocol	O
having	O
similarities	O
to	O
Internet	B-Protocol
Protocol	I-Protocol
,	O
and	O
SPX	B-Protocol
having	O
similarities	O
to	O
TCP	B-Protocol
.	O
</s>
<s>
IPX/SPX	B-Protocol
was	O
primarily	O
designed	O
for	O
local	B-General_Concept
area	I-General_Concept
networks	I-General_Concept
(	O
LANs	B-General_Concept
)	O
and	O
is	O
a	O
very	O
efficient	O
protocol	O
for	O
this	O
purpose	O
(	O
typically	O
SPX	B-Protocol
's	O
performance	O
exceeds	O
that	O
of	O
TCP	B-Protocol
on	O
a	O
small	O
LAN	B-General_Concept
,	O
as	O
in	O
place	O
of	O
congestion	B-Protocol
windows	I-Protocol
and	O
confirmatory	O
acknowledgements	B-Protocol
,	O
SPX	B-Protocol
uses	O
simple	O
NAKs	B-Protocol
)	O
.	O
</s>
<s>
TCP/IP	B-Protocol
has	O
,	O
however	O
,	O
become	O
the	O
defacto	O
standard	O
protocol	O
.	O
</s>
<s>
This	O
is	O
in	O
part	O
due	O
to	O
its	O
superior	O
performance	O
over	O
wide	O
area	O
networks	O
and	O
the	O
Internet	O
(	O
which	O
uses	O
IP	O
exclusively	O
)	O
,	O
and	O
also	O
because	O
TCP/IP	B-Protocol
is	O
a	O
more	O
mature	O
protocol	O
,	O
designed	O
specifically	O
with	O
this	O
purpose	O
in	O
mind	O
.	O
</s>
<s>
Despite	O
the	O
protocols	O
 '	O
association	O
with	O
NetWare	B-Operating_System
,	O
they	O
are	O
neither	O
required	O
for	O
NetWare	B-Operating_System
communication	O
(	O
as	O
of	O
NetWare5.x	O
)	O
,	O
nor	O
exclusively	O
used	O
on	O
NetWare	B-Operating_System
networks	O
.	O
</s>
<s>
NetWare	B-Operating_System
communication	O
requires	O
an	O
NCP	B-Protocol
implementation	O
,	O
which	O
can	O
use	O
IPX/SPX	B-Protocol
,	O
TCP/IP	B-Protocol
,	O
or	O
both	O
,	O
as	O
a	O
transport	O
.	O
</s>
<s>
Novell	O
was	O
largely	O
responsible	O
for	O
the	O
use	O
of	O
IPX	B-Protocol
as	O
a	O
popular	O
computer	O
networking	O
protocol	O
due	O
to	O
their	O
dominance	O
in	O
the	O
network	O
operating	B-General_Concept
system	I-General_Concept
software	O
market	O
(	O
with	O
Novell	B-Operating_System
Netware	I-Operating_System
)	O
from	O
the	O
late	O
1980s	O
through	O
the	O
mid-1990s	O
.	O
</s>
<s>
Novell	O
's	O
original	O
NetWare	B-Operating_System
client	O
was	O
written	O
for	O
DOS	B-Device
.	O
</s>
<s>
IPX/SPX	B-Protocol
was	O
the	O
de	O
facto	O
standard	O
for	O
DOS-era	O
multi-user	O
network	O
games	O
.	O
</s>
<s>
Many	O
games	O
 '	O
longevity	O
were	O
extended	O
through	O
tunneling	O
programs	O
like	O
Kali	B-Protocol
and	O
Kahn	O
which	O
allowed	O
them	O
to	O
be	O
played	O
over	O
the	O
internet	O
instead	O
of	O
LAN-only	O
.	O
</s>
<s>
DOSBox	B-Application
emulates	O
IPX	B-Protocol
over	O
UDP	B-Protocol
.	O
</s>
<s>
Because	O
of	O
IPX/SPX	B-Protocol
'	O
s	O
prevalence	O
in	O
LANs	B-General_Concept
in	O
the	O
1990s	O
,	O
Microsoft	O
added	O
support	O
for	O
the	O
protocols	O
into	O
Windows	B-Application
 '	O
networking	O
stack	O
,	O
starting	O
with	O
Windows	B-Application
for	O
Workgroups	O
and	O
Windows	B-Device
NT	I-Device
.	O
</s>
<s>
Microsoft	O
even	O
named	O
their	O
implementation	O
"	O
NWLink	B-Protocol
"	O
,	O
implying	O
that	O
the	O
inclusion	O
of	O
the	O
layer	O
3/4	O
transports	O
provided	O
NetWare	B-Operating_System
connectivity	O
.	O
</s>
<s>
In	O
reality	O
,	O
the	O
protocols	O
were	O
supported	O
as	O
a	O
native	O
transport	O
for	O
Windows	B-Application
 '	O
SMB/NetBIOS	O
,	O
and	O
NetWare	B-Operating_System
connectivity	O
required	O
additional	O
installation	O
of	O
an	O
NCP	B-Protocol
client	O
(	O
Microsoft	O
provided	O
a	O
basic	O
NetWare	B-Operating_System
client	O
with	O
Windows	B-Application
95	I-Application
and	O
later	O
,	O
but	O
it	O
was	O
not	O
automatically	O
installed	O
,	O
and	O
initially	O
only	O
supported	O
NetWare	B-Operating_System
bindery	O
mode	O
)	O
.	O
</s>
<s>
NWLink	B-Protocol
was	O
still	O
provided	O
with	O
Windows	B-Application
(	O
up	O
to	O
and	O
including	O
Windows	B-Application
Server	I-Application
2003	I-Application
)	O
,	O
but	O
it	O
is	O
neither	O
included	O
with	O
nor	O
supported	O
in	O
Windows	B-Application
Vista	I-Application
.	O
</s>
<s>
Its	O
use	O
is	O
strongly	O
discouraged	O
because	O
it	O
cannot	O
be	O
used	O
for	O
Windows	B-Application
networking	O
except	O
as	O
a	O
transport	O
for	O
NetBIOS	B-Protocol
,	O
which	O
is	O
deprecated	O
.	O
</s>
<s>
For	O
the	O
most	O
part	O
,	O
Novell	O
's	O
32-bit	B-Application
Windows	I-Application
client	O
software	O
have	O
eschewed	O
NWLink	B-Protocol
for	O
an	O
alternative	O
developed	O
by	O
Novell	O
,	O
although	O
some	O
versions	O
permit	O
use	O
of	O
Microsoft	O
's	O
IPX/SPX	B-Protocol
implementation	O
(	O
with	O
warnings	O
about	O
potential	O
incompatibility	O
)	O
.	O
</s>
<s>
For	O
several	O
years	O
,	O
Novell	O
supplied	O
a	O
native	O
NetWare	B-Operating_System
client	O
for	O
OS/2	B-Application
.	O
</s>
<s>
This	O
was	O
similar	O
in	O
structure	O
to	O
the	O
client	O
for	O
DOS	B-Device
.	O
</s>
<s>
Novell	O
also	O
published	O
an	O
IPX	B-Protocol
client	O
for	O
Classic	B-Application
Mac	I-Application
OS	I-Application
called	O
MacIPX	O
.	O
</s>
<s>
This	O
was	O
not	O
only	O
used	O
by	O
the	O
Mac	O
NetWare	B-Operating_System
client	O
,	O
but	O
also	O
by	O
games	O
such	O
as	O
Doom	B-Application
and	O
Warcraft	B-Application
III	I-Application
for	O
multiplayer	O
play	O
.	O
</s>
<s>
Implementations	O
have	O
been	O
written	O
for	O
various	O
flavors	O
of	O
Unix/Linux	O
,	O
both	O
by	O
Novell	O
and	O
other	O
vendors	O
.	O
</s>
<s>
In	O
particular	O
,	O
Novell	O
's	O
UnixWare	B-Operating_System
supported	O
IPX/SPX	B-Protocol
natively	O
.	O
</s>
<s>
However	O
,	O
while	O
UnixWare	B-Operating_System
could	O
act	O
as	O
a	O
client	O
to	O
NetWare	B-Operating_System
servers	O
,	O
and	O
applications	O
could	O
optionally	O
support	O
IPX/SPX	B-Protocol
as	O
a	O
transport	O
,	O
UnixWare	B-Operating_System
did	O
not	O
provide	O
the	O
ability	O
to	O
share	O
files	O
or	O
printers	O
on	O
a	O
NetWare	B-Operating_System
network	O
without	O
an	O
additional	O
software	O
package	O
.	O
</s>
<s>
Open	B-Application
Enterprise	I-Application
Server	I-Application
-	O
Linux	B-Application
does	O
not	O
support	O
IPX/SPX	B-Protocol
.	O
</s>
<s>
The	O
Linux	B-Application
kernel	O
used	O
to	O
support	O
IPX/SPX	B-Protocol
,	O
but	O
SPX	B-Protocol
support	O
was	O
removed	O
in	O
2002	O
,	O
and	O
IPX	B-Protocol
support	O
was	O
removed	O
in	O
2018	O
.	O
</s>
<s>
The	O
open	O
source	O
FreeBSD	B-Operating_System
operating	B-General_Concept
system	I-General_Concept
includes	O
an	O
IPX/SPX	B-Protocol
stack	O
,	O
to	O
support	O
both	O
a	O
NetWare	B-Operating_System
file	O
system	O
client	O
,	O
nwfs	O
,	O
as	O
well	O
as	O
NetWare	B-Operating_System
server	O
using	O
Mars	O
NWE	O
(	O
providing	O
some	O
functionality	O
)	O
.	O
</s>
<s>
OpenBSD	B-Operating_System
dropped	O
support	O
with	O
version	O
4.2	O
,	O
and	O
4.1	O
needed	O
some	O
work	O
to	O
compile	O
with	O
IPX	B-Protocol
.	O
</s>
<s>
IPX	B-Protocol
usage	O
has	O
declined	O
in	O
recent	O
years	O
,	O
as	O
the	O
rise	O
of	O
the	O
Internet	O
has	O
made	O
TCP/IP	B-Protocol
ubiquitous	O
.	O
</s>
<s>
Novell	O
's	O
initial	O
attempt	O
to	O
support	O
TCP/IP	B-Protocol
as	O
a	O
client	O
protocol	O
,	O
called	O
NetWare/IP	O
,	O
simply	O
"	B-Protocol
tunneled	I-Protocol
"	I-Protocol
IPX	B-Protocol
within	O
IP	O
packets	O
,	O
allowing	O
NetWare	B-Operating_System
clients	O
and	O
servers	O
to	O
communicate	O
over	O
pure	O
TCP/IP	B-Protocol
networks	I-Protocol
.	O
</s>
<s>
However	O
,	O
due	O
to	O
complex	O
implementation	O
and	O
a	O
significant	O
loss	O
in	O
performance	O
due	O
to	O
the	O
tunnelling	O
overhead	O
,	O
NetWare/IP	O
was	O
largely	O
ignored	O
,	O
except	O
as	O
a	O
mechanism	O
to	O
route	O
IPX	B-Protocol
through	O
TCP/IP	B-Protocol
-only	O
routers	O
and	O
WAN	O
links	O
.	O
</s>
<s>
NetWare5.x	O
introduced	O
native	O
support	O
for	O
NCP	B-Protocol
over	O
TCP/IP	B-Protocol
,	O
which	O
is	O
now	O
the	O
preferred	O
configuration	O
.	O
</s>
<s>
The	O
successor	O
to	O
NetWare	B-Operating_System
,	O
Open	B-Application
Enterprise	I-Application
Server	I-Application
,	O
comes	O
in	O
two	O
flavors	O
:	O
OES-NetWare	O
,	O
which	O
provides	O
legacy	O
support	O
for	O
IPX/SPX	B-Protocol
(	O
deprecated	O
)	O
,	O
and	O
OES-Linux	O
,	O
which	O
only	O
supports	O
TCP/IP	B-Protocol
.	O
</s>
<s>
Both	O
Microsoft	O
and	O
Novell	O
have	O
provided	O
support	O
(	O
through	O
Proxy	B-Application
Server/ISA	I-Application
Server	I-Application
and	O
BorderManager	B-Protocol
respectively	O
)	O
for	O
IPX/SPX	B-Protocol
as	O
an	O
intranet	O
protocol	O
to	O
communicate	O
through	O
a	O
firewall	B-Application
.	O
</s>
<s>
This	O
allows	O
a	O
machine	O
using	O
client	O
software	O
to	O
access	O
the	O
Internet	O
without	O
having	O
TCP/IP	B-Protocol
installed	O
locally	O
;	O
the	O
client	O
software	O
emulates	O
a	O
native	O
TCP/IP	B-Protocol
stack	I-Protocol
and	O
provides	O
WinSock	B-Application
support	O
for	O
local	O
applications	O
(	O
e.g.	O
</s>
<s>
web	O
browsers	O
)	O
,	O
but	O
actually	O
communicates	O
with	O
the	O
firewall	B-Application
over	O
IPX/SPX	B-Protocol
.	O
</s>
<s>
In	O
addition	O
to	O
simplifying	O
migration	O
for	O
legacy	O
IPX	B-Protocol
LANs	B-General_Concept
,	O
this	O
provides	O
a	O
measure	O
of	O
security	O
,	O
as	O
the	O
use	O
of	O
the	O
IPX	B-Protocol
protocol	O
on	O
the	O
internal	O
network	O
provides	O
a	O
natural	O
barrier	O
against	O
intruders	O
,	O
should	O
the	O
firewall	B-Application
be	O
compromised	O
.	O
</s>
<s>
One	O
area	O
where	O
IPX	B-Protocol
remains	O
useful	O
is	O
for	O
bypassing	O
VPN	B-Application
connections	I-Application
with	O
security	O
policies	O
that	O
prohibit	O
communication	O
with	O
other	O
LAN	B-General_Concept
devices	O
(	O
such	O
as	O
printers	O
and	O
network-attached	B-Application
storage	I-Application
)	O
via	O
TCP/IP	B-Protocol
.	O
</s>
