<s>
Internetwork	B-Protocol
Packet	I-Protocol
Exchange	I-Protocol
(	O
IPX	B-Protocol
)	O
is	O
the	O
network	B-Application
layer	I-Application
protocol	O
in	O
the	O
IPX/SPX	B-Protocol
protocol	B-Protocol
suite	I-Protocol
.	O
</s>
<s>
IPX	B-Protocol
is	O
derived	O
from	O
Xerox	B-Protocol
Network	I-Protocol
Systems	I-Protocol
 '	O
IDP	O
.	O
</s>
<s>
It	O
also	O
has	O
the	O
ability	O
to	O
act	O
as	O
a	O
transport	B-Architecture
layer	I-Architecture
protocol	O
.	O
</s>
<s>
The	O
IPX/SPX	B-Protocol
protocol	B-Protocol
suite	I-Protocol
was	O
very	O
popular	O
through	O
the	O
late	O
1980s	O
and	O
mid-1990s	O
because	O
it	O
was	O
used	O
by	O
Novell	B-Operating_System
NetWare	I-Operating_System
,	O
a	O
network	B-Protocol
operating	I-Protocol
system	I-Protocol
.	O
</s>
<s>
Due	O
to	O
Novell	B-Operating_System
NetWare	I-Operating_System
's	O
popularity	O
,	O
IPX	B-Protocol
became	O
a	O
prominent	O
protocol	O
for	O
internetworking	B-Architecture
.	O
</s>
<s>
A	O
big	O
advantage	O
of	O
IPX	B-Protocol
was	O
a	O
small	O
memory	O
footprint	O
of	O
the	O
IPX	B-Protocol
driver	O
,	O
which	O
was	O
vital	O
for	O
DOS	B-Device
and	O
Windows	O
up	O
to	O
Windows	B-Application
95	I-Application
due	O
to	O
the	O
limited	O
size	O
at	O
that	O
time	O
of	O
conventional	B-Device
memory	I-Device
.	O
</s>
<s>
Another	O
IPX	B-Protocol
advantage	O
is	O
easy	O
configuration	O
of	O
its	O
client	O
computers	O
.	O
</s>
<s>
However	O
,	O
IPX	B-Protocol
does	O
not	O
scale	O
well	O
for	O
large	O
networks	O
such	O
as	O
the	O
Internet	O
.	O
</s>
<s>
As	O
such	O
,	O
IPX	B-Protocol
usage	O
decreased	O
as	O
the	O
boom	O
of	O
the	O
Internet	O
made	O
TCP/IP	B-Protocol
nearly	O
universal	O
.	O
</s>
<s>
Computers	O
and	O
networks	O
can	O
run	O
multiple	O
network	O
protocols	O
,	O
so	O
almost	O
all	O
IPX	B-Protocol
sites	O
also	O
run	O
TCP/IP	B-Protocol
,	O
to	O
allow	O
Internet	O
connectivity	O
.	O
</s>
<s>
It	O
is	O
also	O
possible	O
to	O
run	O
later	O
Novell	O
products	O
without	O
IPX	B-Protocol
,	O
with	O
the	O
beginning	O
of	O
full	O
support	O
for	O
both	O
IPX	B-Protocol
and	O
TCP/IP	B-Protocol
by	O
NetWare	B-Operating_System
version	O
5	O
in	O
late	O
1998	O
.	O
</s>
<s>
A	O
big	O
advantage	O
of	O
IPX	B-Protocol
protocol	O
is	O
its	O
little	O
or	O
no	O
need	O
for	O
configuration	O
.	O
</s>
<s>
In	O
the	O
time	O
when	O
protocols	O
for	O
dynamic	B-Protocol
host	I-Protocol
configuration	I-Protocol
did	O
not	O
exist	O
and	O
the	O
BOOTP	B-Device
protocol	O
for	O
centralized	O
assigning	O
of	O
addresses	O
was	O
not	O
common	O
,	O
the	O
IPX	B-Protocol
network	O
could	O
be	O
configured	O
almost	O
automatically	O
.	O
</s>
<s>
A	O
client	O
computer	O
uses	O
the	O
MAC	O
address	O
of	O
its	O
network	O
card	O
as	O
the	O
node	O
address	O
and	O
learns	O
what	O
it	O
needs	O
to	O
know	O
about	O
the	O
network	O
topology	O
from	O
the	O
servers	O
or	O
routers	B-Protocol
–	O
routes	O
are	O
propagated	O
by	O
Routing	B-Protocol
Information	I-Protocol
Protocol	I-Protocol
,	O
services	O
by	O
Service	B-Protocol
Advertising	I-Protocol
Protocol	I-Protocol
.	O
</s>
<s>
to	O
assign	O
different	O
network	O
numbers	O
to	O
different	O
interfaces	O
of	O
servers	O
with	O
multiple	O
network	O
cards	O
(	O
Novell	B-Operating_System
NetWare	I-Operating_System
server	O
with	O
multiple	O
network	O
cards	O
worked	O
automatically	O
as	O
a	O
router	B-Protocol
)	O
,	O
</s>
<s>
to	O
start	O
router	B-Protocol
process	O
on	O
nodes	O
with	O
multiple	O
network	O
cards	O
in	O
more	O
complex	O
networks	O
.	O
</s>
<s>
Each	O
IPX	B-Protocol
packet	O
begins	O
with	O
a	O
header	O
with	O
the	O
following	O
structure	O
:	O
</s>
<s>
An	O
IPX	B-Protocol
address	O
has	O
the	O
following	O
structure	O
:	O
</s>
<s>
The	O
network	O
number	O
allows	O
to	O
address	O
(	O
and	O
communicate	O
with	O
)	O
the	O
IPX	B-Protocol
nodes	O
which	O
do	O
not	O
belong	O
to	O
the	O
same	O
network	O
or	O
cabling	O
system	O
.	O
</s>
<s>
The	O
cabling	O
system	O
is	O
a	O
network	O
in	O
which	O
a	O
data	B-Protocol
link	I-Protocol
layer	I-Protocol
protocol	O
can	O
be	O
used	O
for	O
communication	O
.	O
</s>
<s>
To	O
allow	O
communication	O
between	O
different	O
networks	O
,	O
they	O
must	O
be	O
connected	O
with	O
IPX	B-Protocol
routers	B-Protocol
.	O
</s>
<s>
A	O
set	O
of	O
interconnected	O
networks	O
is	O
called	O
an	O
internetwork	B-Architecture
.	O
</s>
<s>
Any	O
Novell	B-Operating_System
NetWare	I-Operating_System
server	O
may	O
serve	O
as	O
an	O
IPX	B-Protocol
router	B-Protocol
.	O
</s>
<s>
Novell	O
also	O
supplied	O
stand-alone	O
routers	B-Protocol
.	O
</s>
<s>
Multiprotocol	O
routers	B-Protocol
of	O
other	O
vendors	O
often	O
support	O
IPX	B-Protocol
routing	B-Protocol
.	O
</s>
<s>
different	O
network	O
numbers	O
must	O
be	O
used	O
for	O
different	O
frame	O
formats	O
even	O
in	O
the	O
same	O
cabling	O
system	O
and	O
a	O
router	B-Protocol
must	O
be	O
used	O
to	O
allow	O
communication	O
between	O
nodes	O
using	O
different	O
frame	O
formats	O
in	O
the	O
same	O
cabling	O
system	O
)	O
.	O
</s>
<s>
Network	O
addresses	O
,	O
which	O
exist	O
in	O
addition	O
to	O
the	O
node	O
address	O
,	O
but	O
are	O
not	O
part	O
of	O
the	O
MAC	O
layer	O
,	O
are	O
assigned	O
only	O
if	O
an	O
IPX	B-Protocol
router	B-Protocol
is	O
present	O
or	O
by	O
manual	O
configuration	O
in	O
the	O
network	O
.	O
</s>
<s>
The	O
network	O
address	O
covers	O
every	O
network	O
participant	O
that	O
can	O
talk	O
to	O
another	O
participant	O
without	O
the	O
aid	O
of	O
an	O
IPX	B-Protocol
router	B-Protocol
.	O
</s>
<s>
In	O
combination	O
,	O
both	O
network	O
and	O
node	O
address	O
form	O
a	O
80	O
bit	O
unique	O
identifier	O
for	O
each	O
IPX	B-Protocol
node	O
across	O
connected	O
logical	O
networks	O
.	O
</s>
<s>
Network	O
number	O
00:00:00:00	O
refers	O
to	O
the	O
current	O
network	O
,	O
and	O
is	O
also	O
used	O
during	O
router	B-Protocol
discovery	O
.	O
</s>
<s>
It	O
's	O
also	O
the	O
default	O
in	O
case	O
no	O
router	B-Protocol
is	O
present	O
,	O
but	O
can	O
be	O
changed	O
by	O
manual	O
configuration	O
,	O
depending	O
on	O
the	O
IPX	B-Protocol
implementation	O
.	O
</s>
<s>
Broadcast	B-Protocol
network	O
number	O
is	O
FF:FF:FF:FF	O
.	O
</s>
<s>
The	O
value	O
FF:FF:FF:FF:FF:FF	O
may	O
be	O
used	O
as	O
a	O
node	O
number	O
in	O
a	O
destination	O
address	O
to	O
broadcast	B-Protocol
a	O
packet	O
to	O
"	O
all	O
nodes	O
in	O
the	O
current	O
network	O
"	O
.	O
</s>
<s>
The	O
presence	O
of	O
a	O
socket	O
number	O
in	O
the	O
IPX	B-Protocol
address	O
allows	O
the	O
IPX	B-Protocol
to	O
act	O
as	O
a	O
transport	B-Architecture
layer	I-Architecture
protocol	O
,	O
comparable	O
with	O
the	O
User	B-Protocol
Datagram	I-Protocol
Protocol	I-Protocol
(	O
UDP	B-Protocol
)	O
in	O
the	O
Internet	B-Protocol
protocol	I-Protocol
suite	I-Protocol
.	O
</s>
<s>
The	O
IPX	B-Protocol
network	O
number	O
is	O
conceptually	O
identical	O
to	O
the	O
network	O
part	O
of	O
the	O
IP	B-Protocol
address	I-Protocol
(	O
the	O
parts	O
with	O
netmask	B-Protocol
bits	O
set	O
to	O
1	O
)	O
;	O
the	O
node	O
number	O
has	O
the	O
same	O
meaning	O
as	O
the	O
bits	O
of	O
IP	B-Protocol
address	I-Protocol
with	O
netmask	B-Protocol
bits	O
set	O
to	O
0	O
.	O
</s>
<s>
The	O
difference	O
is	O
that	O
the	O
boundary	O
between	O
network	O
and	O
node	O
part	O
of	O
address	O
in	O
IP	B-Protocol
is	O
variable	O
,	O
while	O
in	O
IPX	B-Protocol
it	O
is	O
fixed	O
.	O
</s>
<s>
As	O
the	O
node	O
address	O
is	O
usually	O
identical	O
to	O
the	O
MAC	O
address	O
of	O
the	O
network	O
adapter	O
,	O
the	O
Address	O
Resolution	O
Protocol	O
is	O
not	O
needed	O
in	O
IPX	B-Protocol
.	O
</s>
<s>
For	O
routing	B-Protocol
,	O
the	O
entries	O
in	O
the	O
IPX	B-Protocol
routing	B-Protocol
table	I-Protocol
are	O
similar	O
to	O
IP	B-Protocol
routing	B-Protocol
tables	I-Protocol
;	O
routing	B-Protocol
is	O
done	O
by	O
network	O
address	O
,	O
and	O
for	O
each	O
network	O
address	O
a	O
network:node	O
of	O
the	O
next	O
router	B-Protocol
is	O
specified	O
in	O
a	O
similar	O
fashion	O
an	O
IP	B-Protocol
address/netmask	O
is	O
specified	O
in	O
IP	B-Protocol
routing	B-Protocol
tables	I-Protocol
.	O
</s>
<s>
There	O
are	O
three	O
routing	B-Protocol
protocols	O
available	O
for	O
IPX	B-Protocol
networks	O
.	O
</s>
<s>
In	O
early	O
IPX	B-Protocol
networks	O
,	O
a	O
version	O
of	O
Routing	B-Protocol
Information	I-Protocol
Protocol	I-Protocol
(	O
RIP	O
)	O
was	O
the	O
only	O
available	O
protocol	O
to	O
exchange	O
routing	B-Protocol
information	I-Protocol
.	O
</s>
<s>
Unlike	O
RIP	O
for	O
IP	B-Protocol
,	O
it	O
uses	O
delay	O
time	O
as	O
the	O
main	O
metric	O
,	O
retaining	O
the	O
hop	O
count	O
as	O
a	O
secondary	O
metric	O
.	O
</s>
<s>
Since	O
NetWare	B-Operating_System
3	O
,	O
the	O
NetWare	B-Protocol
Link	I-Protocol
Services	I-Protocol
Protocol	I-Protocol
(	O
NLSP	O
)	O
based	O
on	O
IS-IS	B-Protocol
is	O
available	O
,	O
which	O
is	O
more	O
suitable	O
for	O
larger	O
networks	O
.	O
</s>
<s>
Cisco	O
routers	B-Protocol
implement	O
an	O
IPX	B-Protocol
version	O
of	O
EIGRP	B-Protocol
protocol	O
as	O
well	O
.	O
</s>
<s>
IPX	B-Protocol
can	O
be	O
transmitted	O
over	O
Ethernet	O
using	O
one	O
of	O
the	O
following	O
4	O
frame	O
formats	O
or	O
encapsulation	O
types	O
:	O
</s>
<s>
802.3	O
(	O
raw	O
)	O
encapsulation	O
comprises	O
an	O
IEEE	O
802.3	O
frame	O
header	O
(	O
destination	O
MAC	O
,	O
source	O
MAC	O
,	O
length	O
)	O
immediately	O
followed	O
by	O
IPX	B-Protocol
data	O
.	O
</s>
<s>
It	O
is	O
used	O
in	O
legacy	O
systems	O
,	O
and	O
can	O
be	O
distinguished	O
by	O
the	O
first	O
two	O
bytes	O
of	O
the	O
IPX	B-Protocol
header	O
always	O
containing	O
a	O
value	O
of	O
0xFFFF	O
,	O
which	O
cannot	O
be	O
interpreted	O
as	O
valid	O
LLC	O
Destination	O
and	O
Source	O
Service	B-Protocol
Access	I-Protocol
Points	I-Protocol
in	O
this	O
location	O
of	O
the	O
frame	O
.	O
</s>
<s>
802.2	O
(	O
LLC	O
or	O
Novell	O
)	O
comprises	O
an	O
IEEE	O
802.3	O
frame	O
header	O
(	O
destination	O
MAC	O
,	O
source	O
MAC	O
,	O
length	O
)	O
followed	O
by	O
an	O
LLC	O
header	O
(	O
DSAP	B-Protocol
0xE0	O
,	O
SSAP	B-Protocol
0xE0	O
,	O
control	O
0x03	O
)	O
followed	O
by	O
IPX	B-Protocol
data	O
.	O
</s>
<s>
The	O
0xE0	O
fields	O
of	O
the	O
LLC	O
header	O
indicate	O
"	O
NetWare	B-Operating_System
"	O
.	O
</s>
<s>
802.2	O
(	O
SNAP	B-Protocol
)	O
comprises	O
an	O
IEEE	O
802.3	O
frame	O
header	O
,	O
an	O
LLC	O
header	O
(	O
DSAP	B-Protocol
0xAA	O
,	O
SSAP	B-Protocol
0xAA	O
,	O
control	O
0x03	O
)	O
,	O
a	O
SNAP	B-Protocol
header	I-Protocol
(	O
OUI	O
0x000000	O
,	O
type	O
0x8137	O
)	O
,	O
and	O
IPX	B-Protocol
data	O
.	O
</s>
<s>
The	O
0xAA	O
fields	O
of	O
the	O
LLC	O
header	O
indicate	O
"	O
SNAP	B-Protocol
"	O
,	O
and	O
the	O
OUI	O
0x000000	O
in	O
the	O
SNAP	B-Protocol
header	I-Protocol
indicates	O
an	O
encapsulated	O
EtherType	B-Protocol
.	O
</s>
<s>
Ethernet	O
II	O
encapsulation	O
comprises	O
an	O
Ethernet	O
II	O
frame	O
header	O
(	O
destination	O
MAC	O
,	O
source	O
MAC	O
,	O
EtherType	B-Protocol
0x8137	O
)	O
followed	O
by	O
IPX	B-Protocol
data	O
.	O
</s>
<s>
In	O
non-Ethernet	O
networks	O
only	O
802.2	O
and	O
SNAP	B-Protocol
frame	O
types	O
are	O
available	O
.	O
</s>
