<s>
Remote	B-Protocol
error	I-Protocol
indication	I-Protocol
(	O
REI	O
)	O
or	O
formerly	O
far	B-Protocol
end	I-Protocol
block	I-Protocol
error	I-Protocol
(	O
FEBE	B-Protocol
)	O
is	O
an	O
alarm	O
signal	O
used	O
in	O
synchronous	B-Protocol
optical	I-Protocol
networking	I-Protocol
(	O
SONET	B-Protocol
)	O
.	O
</s>
<s>
REI	O
or	O
FEBE	B-Protocol
errors	O
are	O
mostly	O
seen	O
on	O
DS3	O
circuits	O
,	O
however	O
they	O
are	O
known	O
to	O
be	O
present	O
on	O
other	O
types	O
(	O
SONET/T1s	O
etc	O
.	O
</s>
<s>
Each	O
terminating	O
device	O
(	O
router	B-Protocol
or	O
otherwise	O
)	O
monitors	O
the	O
incoming	O
signal	O
for	O
CP-bit	O
path	O
errors	O
.	O
</s>
<s>
If	O
an	O
error	O
is	O
detected	O
on	O
the	O
incoming	O
DS3	O
,	O
the	O
terminating	O
elements	O
transmit	O
a	O
FEBE	B-Protocol
bit	O
on	O
the	O
outgoing	O
direction	O
of	O
the	O
DS3	O
.	O
</s>
<s>
Network	O
monitoring	O
equipment	O
located	O
anywhere	O
along	O
the	O
path	O
then	O
measures	O
these	O
FEBEs	B-Protocol
in	O
each	O
direction	O
to	O
gauge	O
the	O
quality	O
of	O
the	O
circuit	O
while	O
in	O
service	O
.	O
</s>
<s>
The	O
errors	O
are	O
being	O
generated	O
by	O
a	O
device	O
in	O
the	O
central	O
office	O
,	O
and	O
being	O
detected	O
by	O
the	O
terminating	O
device	O
(	O
a	O
NID	O
,	O
M13	O
Mux	O
or	O
router	B-Protocol
)	O
.	O
</s>
<s>
The	O
terminating	O
device	O
then	O
sends	O
the	O
'	O
FEBE	B-Protocol
 '	O
error	O
signal	O
outbound	O
to	O
alert	O
further	O
devices	O
there	O
were	O
problems	O
.	O
</s>
<s>
So	O
,	O
errors	O
are	O
generated	O
on	O
the	O
incoming	O
side	O
of	O
the	O
loop	O
,	O
the	O
device	O
terminating	O
that	O
end	O
picks	O
up	O
the	O
errors	O
,	O
and	O
transmits	O
a	O
'	O
FEBE	B-Protocol
errors	O
 '	O
message	O
on	O
the	O
outgoing	O
side	O
.	O
</s>
<s>
An	O
error	O
detected	O
by	O
extracting	O
the	O
4-bit	O
FEBE	B-Protocol
field	O
from	O
the	O
path	O
status	O
byte	O
(	O
G1	O
)	O
.	O
</s>
<s>
An	O
ATM	O
interface	O
reports	O
detected	O
C-bit	O
parity	O
errors	O
back	O
to	O
the	O
source	O
via	O
a	O
far-end	O
block	O
error	O
(	O
FEBE	B-Protocol
)	O
.	O
</s>
<s>
(	O
DS3	O
)	O
A	O
FEBE	B-Protocol
in	O
C-bit	O
parity	O
is	O
a	O
parity	O
violation	O
detected	O
at	O
the	O
far-end	O
terminal	O
and	O
transmitted	O
back	O
to	O
the	O
near-end	O
terminal	O
.	O
</s>
