<s>
Distributed	B-Device
switching	I-Device
is	O
an	O
architecture	O
in	O
which	O
multiple	O
processor-controlled	O
switching	O
units	O
are	O
distributed	O
.	O
</s>
<s>
There	O
is	O
often	O
a	O
hierarchy	O
of	O
switching	O
elements	O
,	O
with	O
a	O
centralized	O
host	B-Application
switch	B-Device
and	O
with	O
remote	O
switches	O
located	O
close	O
to	O
concentrations	O
of	O
users	O
.	O
</s>
<s>
Distributed	B-Device
switching	I-Device
is	O
often	O
used	O
in	O
telephone	O
networks	O
,	O
though	O
it	O
is	O
often	O
called	O
host-remote	O
switching	O
.	O
</s>
<s>
Use	O
of	O
distributed	B-Device
switching	I-Device
allows	O
for	O
the	O
majority	O
of	O
calls	O
that	O
are	O
local	O
to	O
that	O
population	O
center	O
to	O
be	O
switched	O
there	O
without	O
needing	O
to	O
be	O
transported	O
to	O
and	O
from	O
the	O
host	B-Application
switch	B-Device
.	O
</s>
<s>
The	O
host	B-Application
switch	B-Device
provides	O
connectivity	O
between	O
the	O
remote	O
switches	O
and	O
to	O
the	O
larger	O
network	O
,	O
and	O
the	O
host	B-Application
may	O
also	O
directly	O
handle	O
some	O
rare	O
and	O
complex	O
call	O
types	O
(	O
conference	O
calling	O
,	O
for	O
example	O
)	O
that	O
the	O
remote	O
itself	O
is	O
not	O
equipped	O
to	O
handle	O
.	O
</s>
<s>
Host	B-Application
switches	O
also	O
perform	O
OAM&P	B-Architecture
(	O
Operation	O
,	O
Administration	O
,	O
Maintenance	O
,	O
and	O
Provisioning	O
)	O
functions	O
,	O
including	O
billing	O
,	O
for	O
the	O
entire	O
cluster	O
of	O
the	O
host	B-Application
and	O
its	O
remote	O
switches	O
.	O
</s>
<s>
A	O
key	O
capability	O
of	O
a	O
remote	O
switch	B-Device
is	O
the	O
ability	O
to	O
act	O
in	O
emergency	O
standalone	O
(	O
ESA	O
)	O
mode	O
,	O
wherein	O
local	O
calls	O
can	O
still	O
be	O
placed	O
even	O
in	O
the	O
event	O
that	O
the	O
connection	O
between	O
that	O
remote	O
and	O
the	O
host	B-Application
has	O
been	O
lost	O
.	O
</s>
<s>
In	O
this	O
mode	O
,	O
only	O
local	O
calling	O
is	O
available	O
anyway	O
,	O
so	O
the	O
billing	O
capability	O
of	O
the	O
host	B-Application
switch	B-Device
is	O
not	O
required	O
.	O
</s>
<s>
ESA	O
is	O
increasingly	O
available	O
on	O
digital	B-Application
loop	I-Application
carrier	I-Application
platforms	O
as	O
well	O
as	O
on	O
purpose-built	O
remote	O
switches	O
in	O
order	O
to	O
improve	O
the	O
scope	O
of	O
their	O
utility	O
.	O
</s>
<s>
Many	O
data-centric	O
telecommunications	O
platforms	O
such	O
as	O
routers	B-Protocol
and	O
Ethernet	O
switches	O
utilize	O
distributed	B-Device
switching	I-Device
on	O
separate	O
cards	O
within	O
an	O
equipment	O
chassis	O
.	O
</s>
<s>
Even	O
when	O
this	O
is	O
used	O
,	O
it	O
is	O
common	O
to	O
have	O
a	O
centralized	O
switching	B-Architecture
fabric	I-Architecture
to	O
interconnect	B-General_Concept
the	O
distributed	O
switches	O
.	O
</s>
<s>
This	O
architecture	O
has	O
become	O
less	O
common	O
as	O
backplane	B-Architecture
bus	B-General_Concept
speeds	O
and	O
centralized	O
switch	B-Device
fabric	O
capacities	O
have	O
increased	O
.	O
</s>
