<s>
Cisco	B-Protocol
HDLC	I-Protocol
(	O
cHDLC	B-Protocol
)	O
is	O
an	O
extension	O
to	O
the	O
High-Level	O
Data	O
Link	O
Control	O
(	O
HDLC	O
)	O
network	O
protocol	O
,	O
and	O
was	O
created	O
by	O
Cisco	O
Systems	O
,	O
Inc	O
.	O
HDLC	O
is	O
a	O
bit-oriented	O
synchronous	O
data	B-Protocol
link	I-Protocol
layer	I-Protocol
protocol	O
that	O
was	O
originally	O
developed	O
by	O
the	O
International	O
Organization	O
for	O
Standardization	O
(	O
ISO	O
)	O
.	O
</s>
<s>
Often	O
described	O
as	O
being	O
a	O
proprietary	O
extension	O
,	O
the	O
details	O
of	O
cHDLC	B-Protocol
have	O
been	O
widely	O
distributed	O
and	O
the	O
protocol	O
has	O
been	O
implemented	O
by	O
many	O
network	O
equipment	O
vendors	O
.	O
</s>
<s>
cHDLC	B-Protocol
extends	O
HDLC	O
with	O
multi-protocol	O
support	O
.	O
</s>
<s>
Cisco	B-Protocol
HDLC	I-Protocol
frames	B-Protocol
uses	O
an	O
alternative	O
framing	O
structure	O
to	O
the	O
standard	O
ISO	O
HDLC	O
.	O
</s>
<s>
To	O
support	O
multiple	O
protocols	O
encapsulation	O
,	O
cHDLC	B-Protocol
frames	B-Protocol
contain	O
a	O
field	O
for	O
identifying	O
the	O
network	O
protocol	O
.	O
</s>
<s>
The	O
following	O
table	O
describes	O
the	O
structure	O
of	O
a	O
cHDLC	B-Protocol
frame	O
on	O
the	O
wire	O
.	O
</s>
<s>
The	O
Address	O
field	O
is	O
used	O
to	O
specify	O
the	O
type	O
of	O
packet	O
contained	O
in	O
the	O
cHDLC	B-Protocol
frame	O
;	O
0x0F	O
for	O
Unicast	O
and	O
0x8F	O
for	O
Broadcast	O
packets	O
.	O
</s>
<s>
The	O
Protocol	O
Code	O
field	O
is	O
used	O
to	O
specify	O
the	O
protocol	O
type	O
encapsulated	O
within	O
the	O
cHDLC	B-Protocol
frame	O
(	O
e.g.	O
</s>
<s>
0x0800	O
for	O
Internet	B-Protocol
Protocol	I-Protocol
)	O
.	O
</s>
<s>
The	O
Serial	O
Line	O
Address	O
Resolution	O
Protocol	O
(	O
SLARP	B-Protocol
)	O
frame	O
is	O
designated	O
by	O
a	O
specific	O
cHDLC	B-Protocol
protocol	O
code	O
field	O
value	O
of	O
0x8035	O
.	O
</s>
<s>
Three	O
types	O
of	O
SLARP	B-Protocol
frame	O
are	O
defined	O
:	O
address	O
requests	O
(	O
0x00	O
)	O
,	O
address	O
replies	O
(	O
0x01	O
)	O
,	O
and	O
keep-alive	O
frames	B-Protocol
(	O
0x02	O
)	O
.	O
</s>
<s>
The	O
following	O
table	O
shows	O
the	O
structure	O
of	O
a	O
SLARP	B-Protocol
cHDLC	B-Protocol
address	O
request	O
–	O
response	O
frame	O
.	O
</s>
<s>
The	O
following	O
table	O
shows	O
the	O
structure	O
of	O
a	O
SLARP	B-Protocol
cHDLC	B-Protocol
keep-alive	O
frame	O
.	O
</s>
