<s>
DOCSIS	B-Device
Set-top	I-Device
Gateway	I-Device
(	O
or	O
DSG	O
)	O
is	O
a	O
specification	O
describing	O
how	O
out-of-band	B-Protocol
data	I-Protocol
is	O
delivered	O
to	O
a	O
cable	O
set-top	O
box	O
.	O
</s>
<s>
DSG	O
is	O
an	O
extension	O
of	O
the	O
DOCSIS	B-Protocol
protocol	O
governing	O
cable	B-Device
modems	I-Device
,	O
and	O
applies	O
to	O
all	O
versions	O
of	O
DOCSIS	B-Protocol
.	O
</s>
<s>
The	O
original	O
DOCSIS	B-Protocol
protocol	O
supports	O
only	O
two	O
way	O
connectivity	O
.	O
</s>
<s>
A	O
cable	B-Device
modem	I-Device
that	O
is	O
unable	O
to	O
acquire	O
an	O
upstream	O
channel	O
will	O
give	O
up	O
and	O
resume	O
scanning	O
for	O
new	O
channels	O
.	O
</s>
<s>
Likewise	O
,	O
persistent	O
upstream	O
errors	O
will	O
cause	O
a	O
cable	B-Device
modem	I-Device
to	O
"	O
reinitialize	O
its	O
MAC	O
"	O
and	O
scan	O
for	O
new	O
downstream	O
channels	O
.	O
</s>
<s>
This	O
behavior	O
is	O
appropriate	O
for	O
traditional	O
cable	B-Device
modems	I-Device
,	O
but	O
not	O
for	O
cable	O
set-top	O
boxes	O
.	O
</s>
<s>
The	O
set-top	O
needs	O
a	O
way	O
to	O
distinguish	O
a	O
valid	O
downstream	O
(	O
containing	O
the	O
set-top	O
'	O
s	O
data	O
)	O
from	O
an	O
invalid	O
one	O
used	O
only	O
by	O
standalone	O
cable	B-Device
modems	I-Device
.	O
</s>
<s>
The	O
DSG	O
Specification	O
creates	O
two	O
new	O
SNMP	B-Protocol
management	O
information	O
bases	O
(	O
MIBs	O
)	O
to	O
manage	O
DSG	O
devices	O
.	O
</s>
<s>
One	O
MIB	O
is	O
used	O
by	O
the	O
set-top	O
,	O
the	O
other	O
by	O
the	O
cable	B-Device
modem	I-Device
termination	I-Device
system	I-Device
(	O
CMTS	O
)	O
.	O
</s>
<s>
The	O
DSG-capable	O
cable	B-Device
modem	I-Device
is	O
referred	O
to	O
as	O
the	O
DSG	O
eCM	O
(	O
Embedded	O
Cable	B-Device
Modem	I-Device
)	O
.	O
</s>
