<s>
The	O
general	B-Protocol
communication	I-Protocol
channel	I-Protocol
(	O
GCC	O
)	O
was	O
defined	O
by	O
G.709	O
is	O
an	O
in-band	O
side	O
channel	O
used	O
to	O
carry	O
transmission	O
management	O
and	O
signaling	O
information	O
within	O
optical	B-Protocol
transport	I-Protocol
network	I-Protocol
elements	O
.	O
</s>
<s>
GCC0	B-Protocol
–	O
two	O
bytes	O
within	O
OTUk	B-Protocol
overhead	O
.	O
</s>
<s>
GCC0	B-Protocol
is	O
terminated	O
at	O
every	O
3R	O
(	O
re-shaping	O
,	O
re-timing	O
,	O
re-amplification	O
)	O
point	O
and	O
used	O
to	O
carry	O
GMPLS	O
signaling	O
protocol	O
and/or	O
management	O
information	O
.	O
</s>
<s>
GCC1/2	B-Protocol
–	O
four	O
bytes	O
(	O
each	O
of	O
two	O
bytes	O
)	O
within	O
ODUk	B-Protocol
overhead	O
.	O
</s>
<s>
In	O
contrast	O
to	O
SONET/SDH	B-Protocol
where	O
the	O
data	O
communication	O
channel	O
(	O
DCC	O
)	O
has	O
a	O
constant	O
data	O
rate	O
,	O
GCC	O
data	O
rate	O
depends	O
on	O
the	O
OTN	O
line	O
rate	O
.	O
</s>
<s>
For	O
example	O
,	O
GCC0	B-Protocol
data	O
rate	O
in	O
the	O
case	O
of	O
OTU1	B-Protocol
is	O
~	O
333kbit/s	O
,	O
and	O
for	O
OTU2	B-Protocol
its	O
data	O
rate	O
is	O
~	O
1.3	O
Mbit/s	O
.	O
</s>
