<s>
Fast	B-Protocol
automatic	I-Protocol
restoration	I-Protocol
(	O
FASTAR	O
)	O
is	O
an	O
automated	O
fast	O
response	O
system	O
developed	O
and	O
deployed	O
by	O
American	O
Telephone	O
&	O
Telegraph	O
(	O
AT&T	O
)	O
in	O
1992	O
for	O
the	O
centralized	O
restoration	O
of	O
its	O
digital	O
transport	O
network	O
.	O
</s>
<s>
FASTAR	O
automatically	O
reroutes	O
circuits	O
over	O
a	O
spare	O
protection	O
capacity	O
when	O
a	O
fiber-optic	B-Architecture
cable	I-Architecture
failure	O
is	O
detected	O
,	O
hence	O
increasing	O
service	O
availability	O
and	O
reducing	O
the	O
impact	O
of	O
the	O
outages	O
in	O
the	O
network	O
.	O
</s>
<s>
It	O
is	O
a	O
recovery	O
technique	O
used	O
in	O
computer	B-Architecture
networks	I-Architecture
and	O
telecommunication	O
networks	O
such	O
as	O
mesh	B-Protocol
optical	I-Protocol
networks	I-Protocol
,	O
where	O
the	O
backup	O
path	O
(	O
the	O
alternate	O
path	O
that	O
affected	O
traffic	O
takes	O
after	O
a	O
failure	O
condition	O
)	O
and	O
backup	O
channel	O
are	O
computed	O
in	O
real	O
time	O
after	O
the	O
occurrence	O
of	O
a	O
failure	O
.	O
</s>
<s>
This	O
technique	O
uses	O
a	O
central	O
controller	O
which	O
has	O
access	O
to	O
complete	O
up-to-date	O
and	O
accurate	O
information	O
about	O
the	O
network	O
,	O
the	O
available	O
resources	O
,	O
resources	O
used	O
,	O
the	O
physical	B-Architecture
topology	I-Architecture
of	O
the	O
network	O
,	O
the	O
service	O
demands	O
etc	O
.	O
</s>
<s>
After	O
this	O
new	O
route	O
(	O
backup	O
path	O
)	O
is	O
calculated	O
,	O
the	O
central	O
controller	O
sends	O
out	O
commands	O
to	O
all	O
the	O
affected	O
digital	B-Architecture
cross-connects	I-Architecture
to	O
make	O
appropriate	O
reconfigurations	O
to	O
their	O
switching	O
elements	O
in	O
order	O
to	O
implement	O
this	O
new	O
path	O
.	O
</s>
<s>
As	O
the	O
transport	O
networks	O
gradually	O
developed	O
from	O
digital	B-Architecture
cross	I-Architecture
connect	I-Architecture
system	I-Architecture
(	O
DCS	O
)	O
-based	O
mesh	O
networks	O
,	O
to	O
SONET	B-Protocol
ring	I-Protocol
networks	I-Protocol
,	O
and	O
to	O
optical	B-Protocol
mesh	I-Protocol
networks	I-Protocol
over	O
the	O
years	O
,	O
so	O
did	O
the	O
recovery	O
architecture	O
used	O
therein	O
.	O
</s>
<s>
This	O
architecture	O
was	O
implemented	O
in	O
the	O
1990s	O
with	O
the	O
introduction	O
of	O
the	O
SONET/SDH	B-Protocol
networks	O
,	O
and	O
employed	O
the	O
distributed	O
protection	O
technique	O
.	O
</s>
<s>
This	O
recovery	O
architecture	O
is	O
used	O
in	O
the	O
protection	O
of	O
optical	B-Protocol
mesh	I-Protocol
networks	I-Protocol
which	O
was	O
introduced	O
in	O
early	O
2000s	O
.	O
</s>
<s>
The	O
Restoration	O
Network	O
Controllers	O
(	O
RNCs	O
)	O
are	O
located	O
at	O
each	O
central	O
office	O
(	O
CO	O
)	O
in	O
the	O
fiber	B-Architecture
optic	I-Architecture
network	O
.	O
</s>
<s>
The	O
alarms	O
generated	O
by	O
the	O
affected	O
digital	B-Architecture
access	I-Architecture
and	I-Architecture
cross-connect	I-Architecture
system	I-Architecture
(	O
DACSs	O
)	O
or	O
from	O
the	O
LTE	O
are	O
sent	O
to	O
the	O
RNC	O
,	O
where	O
it	O
is	O
aged	O
to	O
find	O
out	O
if	O
the	O
alarm	O
is	O
as	O
a	O
result	O
of	O
a	O
transient	O
,	O
correlated	O
and	O
finally	O
sent	O
to	O
the	O
RAPID	O
via	O
the	O
data	O
communication	O
network	O
.	O
</s>
<s>
In	O
addition	O
,	O
the	O
DACS	O
enables	O
automatic	O
restoration	O
by	O
providing	O
the	O
central	O
processor	O
access	O
to	O
remotely	O
perform	O
cross-connects	B-Architecture
at	O
the	O
DS-3	O
level	O
.	O
</s>
<s>
When	O
a	O
fiber-optic	B-Architecture
cut	O
occurs	O
between	O
the	O
output	O
of	O
a	O
DACS	O
equipment	O
and	O
the	O
input	O
of	O
another	O
,	O
each	O
RNC	O
collects	O
alarms	O
from	O
the	O
affected	O
LTEs	O
.	O
</s>
<s>
In	O
the	O
figure	O
on	O
the	O
right	O
,	O
a	O
route	O
exists	O
between	O
node	O
A	O
and	O
node	O
Q	O
via	O
nodes	O
C	O
,	O
F	O
,	O
K	O
,	O
and	O
L	O
.	O
In	O
the	O
event	O
of	O
a	O
fiber-optic	B-Architecture
cable	I-Architecture
failure	O
between	O
nodes	O
F	O
and	O
K	O
,	O
the	O
LTE	O
(	O
FT	O
Series	O
G	O
or	O
the	O
ADM	O
)	O
in	O
these	O
two	O
offices	O
detects	O
and	O
sends	O
alarm	O
reports	O
for	O
this	O
failure	O
to	O
their	O
respective	O
RNCs	O
.	O
</s>
<s>
RAPID	O
initiates	O
a	O
time	O
window	O
to	O
ensure	O
all	O
related	O
alarms	O
generated	O
from	O
the	O
RNCs	O
of	O
the	O
affected	O
nodes	O
and	O
the	O
RNC	O
of	O
any	O
other	O
office	O
whose	O
traffic	O
uses	O
the	O
F	O
to	O
K	O
failed	O
fiber	B-Architecture
optic	I-Architecture
cable	O
.	O
</s>
<s>
Here	O
it	O
creates	O
a	O
new	O
route	O
through	O
C	O
,	O
F	O
,	O
G	O
,	O
J	O
,	O
K	O
,	O
and	O
L	O
.	O
This	O
route	O
computation	O
is	O
also	O
done	O
sequentially	O
in	O
order	O
of	O
priority	O
for	O
all	O
the	O
traffic	O
between	O
any	O
two	O
nodes	O
in	O
the	O
network	O
that	O
use	O
the	O
same	O
failed	O
fiber-optic	B-Architecture
cable	I-Architecture
.	O
</s>
<s>
This	O
service	O
or	O
traffic	O
transfer	O
process	O
is	O
performed	O
for	O
all	O
the	O
traffic	O
going	O
through	O
the	O
affected	O
fiber	B-Architecture
optic	I-Architecture
cable	O
F	O
–	O
K	O
.	O
</s>
<s>
Shared	B-Architecture
Risk	I-Architecture
Link	I-Architecture
Groups	I-Architecture
(	O
SRLGs	O
)	O
refer	O
to	O
situations	O
where	O
links	O
that	O
connect	O
two	O
distinct	O
nodes	O
or	O
offices	O
in	O
a	O
network	O
share	O
a	O
common	O
conduit	O
.	O
</s>
