<s>
Link	O
Access	O
Procedure	O
,	O
Balanced	O
(	O
LAPB	B-Protocol
)	O
implements	O
the	O
data	B-Protocol
link	I-Protocol
layer	I-Protocol
as	O
defined	O
in	O
the	O
X.25	B-Protocol
protocol	I-Protocol
suite	I-Protocol
.	O
</s>
<s>
LAPB	B-Protocol
is	O
a	O
bit-oriented	O
protocol	O
derived	O
from	O
HDLC	O
that	O
ensures	O
that	O
frames	O
are	O
error	O
free	O
and	O
in	O
the	O
correct	O
sequence	O
.	O
</s>
<s>
LAPB	B-Protocol
is	O
specified	O
in	O
ITU-T	O
Recommendation	O
X.25	B-Protocol
and	O
ISO/IEC	O
7776	O
.	O
</s>
<s>
LAPB	B-Protocol
is	O
used	O
to	O
manage	O
communication	O
and	O
packet	O
framing	O
between	O
data	O
terminal	O
equipment	O
(	O
DTE	O
)	O
and	O
the	O
data	O
circuit-terminating	O
equipment	O
(	O
DCE	O
)	O
devices	O
in	O
the	O
X.25	B-Protocol
protocol	O
stack	O
.	O
</s>
<s>
LAPB	B-Protocol
is	O
essentially	O
HDLC	O
in	O
Asynchronous	O
Balanced	O
Mode	O
(	O
ABM	O
)	O
.	O
</s>
<s>
LAPB	B-Protocol
sessions	O
can	O
be	O
established	O
by	O
either	O
the	O
DTE	O
or	O
DCE	O
.	O
</s>
<s>
In	O
order	O
to	O
ensure	O
that	O
the	O
bit	O
pattern	O
of	O
the	O
frame	O
delimiter	O
flag	O
does	O
not	O
appear	O
in	O
the	O
data	O
field	O
of	O
the	O
frame	O
(	O
and	O
therefore	O
cause	O
frame	O
misalignment	O
)	O
,	O
a	O
technique	O
known	O
as	O
Bit	B-Protocol
stuffing	I-Protocol
is	O
used	O
by	O
both	O
the	O
transmitter	O
and	O
the	O
receiver	O
.	O
</s>
<s>
Address	O
field	O
–	O
In	O
LAPB	B-Protocol
,	O
this	O
field	O
has	O
no	O
meaning	O
since	O
the	O
protocol	O
works	O
in	O
a	O
point	O
to	O
point	O
mode	O
and	O
the	O
DTE	O
network	B-Protocol
address	I-Protocol
is	O
represented	O
in	O
the	O
layer	O
3	O
packets	O
.	O
</s>
<s>
Therefore	O
,	O
one	O
side	O
must	O
be	O
configured	O
as	O
a	O
Layer	B-Protocol
2	I-Protocol
DTE	O
and	O
the	O
other	O
as	O
a	O
Layer	B-Protocol
2	I-Protocol
DCE	O
(	O
you	O
must	O
not	O
confuse	O
this	O
with	O
the	O
more	O
familiar	O
Layer	O
1	O
DCE	O
and	O
DTE	O
designations	O
)	O
.	O
</s>
<s>
Modes	O
of	O
operation	O
–	O
LAPB	B-Protocol
works	O
in	O
the	O
Asynchronous	O
Balanced	O
Mode	O
(	O
ABM	O
)	O
.	O
</s>
<s>
Window	O
size	O
–	O
LAPB	B-Protocol
supports	O
an	O
extended	O
window	O
size	O
(	O
modulo	O
128	O
and	O
modulo	O
32768	O
)	O
where	O
the	O
maximum	O
number	O
of	O
outstanding	O
frames	O
for	O
acknowledgment	O
is	O
raised	O
from	O
7	O
(	O
modulo	O
8	O
)	O
to	O
127	O
(	O
modulo	O
128	O
)	O
and	O
32767	O
(	O
modulo	O
32768	O
)	O
.	O
</s>
<s>
LAPB	B-Protocol
has	O
no	O
master/slave	O
node	O
relationships	O
.	O
</s>
<s>
The	O
following	O
table	O
shows	O
which	O
addresses	O
are	O
placed	O
into	O
the	O
LAPB	B-Protocol
frame	O
when	O
issuing	O
commands	O
and	O
responses	O
from	O
DTE	O
to	O
DCE	O
and	O
DCE	O
to	O
DTE	O
using	O
single	O
link	O
operation	O
or	O
multilink	O
operation	O
:	O
</s>
