<s>
Datakit	B-General_Concept
is	O
a	O
virtual	B-Protocol
circuit	I-Protocol
switch	O
which	O
was	O
developed	O
by	O
Sandy	O
Fraser	O
at	O
Bell	O
Labs	O
for	O
both	O
local-area	O
and	O
wide-area	O
networks	O
,	O
and	O
in	O
widespread	O
deployment	O
by	O
the	O
Regional	O
Bell	O
Operating	O
Companies	O
(	O
RBOCs	O
)	O
.	O
</s>
<s>
Datakit	B-General_Concept
uses	O
a	O
cell	B-Protocol
relay	I-Protocol
protocol	O
similar	O
to	O
Asynchronous	O
Transfer	O
Mode	O
.	O
</s>
<s>
Datakit	B-General_Concept
is	O
a	O
connection-oriented	O
switch	O
,	O
with	O
all	O
packets	O
for	O
a	O
particular	O
call	O
traveling	O
through	O
the	O
network	O
over	O
the	O
same	O
virtual	B-Protocol
circuit	I-Protocol
.	O
</s>
<s>
Datakit	B-General_Concept
networks	O
are	O
still	O
in	O
widespread	O
use	O
by	O
the	O
major	O
telephone	O
companies	O
in	O
the	O
United	O
States	O
.	O
</s>
<s>
Interfaces	O
to	O
these	O
networks	O
include	O
TCP/IP	B-Protocol
and	O
UDP	O
,	O
X.25	B-Protocol
,	O
asynchronous	O
protocols	O
and	O
several	O
synchronous	O
protocols	O
,	O
such	O
as	O
SDLC	B-Protocol
,	O
HDLC	O
,	O
Bisync	B-Protocol
and	O
others	O
.	O
</s>
<s>
At	O
the	O
physical	B-Application
layer	I-Application
,	O
it	O
can	O
operate	O
over	O
multiple	O
media	O
,	O
from	O
slow	O
speed	O
EIA-232	O
to	O
500Mbit	O
fiber	O
optic	O
links	O
including	O
10/100	O
Megabit	O
ethernet	O
links	O
.	O
</s>
<s>
Most	O
of	O
Bell	O
Laboratories	O
was	O
trunked	O
together	O
via	O
Datakit	B-General_Concept
networking	O
.	O
</s>
<s>
On	O
top	O
of	O
Datakit	B-General_Concept
transport	O
service	O
,	O
several	O
operating	O
systems	O
(	O
including	O
UNIX	B-Application
)	O
implemented	O
UUCP	B-Protocol
for	O
electronic	O
mail	O
and	O
dkcu	O
for	O
remote	O
login	O
.	O
</s>
<s>
Datakit	B-General_Concept
uses	O
an	O
adaptation	O
protocol	O
called	O
Universal	O
Receiver	O
Protocol	O
(	O
URP	O
)	O
that	O
spreads	O
PDU	O
overhead	O
across	O
multiple	O
cells	O
and	O
performs	O
immediate	O
packet	O
processing	O
.	O
</s>
<s>
The	O
Information	O
Systems	O
Network	O
(	O
ISN	O
)	O
was	O
the	O
pre-version	O
of	O
Datakit	B-General_Concept
that	O
was	O
supported	O
by	O
the	O
former	O
AT&T	O
Information	O
Systems	O
.	O
</s>
<s>
It	O
was	O
in	O
production	O
three	O
or	O
more	O
years	O
prior	O
to	O
the	O
Datakit	B-General_Concept
being	O
released	O
.	O
</s>
<s>
Datakit	B-General_Concept
was	O
programmed	O
similar	O
to	O
a	O
Central	O
Office	O
with	O
area	O
code	O
and	O
seven	O
digit	O
location	O
.	O
</s>
<s>
By	O
the	O
late	O
1990s	O
,	O
Datakit	B-General_Concept
was	O
clearly	O
a	O
legacy	O
technology	O
,	O
being	O
superseded	O
by	O
newer	O
technologies	O
such	O
as	O
IP	O
and	O
Ethernet	O
.	O
</s>
<s>
Lucent	O
decided	O
to	O
discontinue	O
their	O
Datakit	B-General_Concept
product	O
line	O
,	O
but	O
a	O
group	O
of	O
former	O
Lucent	O
employees	O
started	O
a	O
new	O
firm	O
,	O
Datatek	O
Applications	O
,	O
who	O
licensed	O
the	O
technology	O
from	O
Lucent	O
,	O
and	O
aimed	O
to	O
support	O
the	O
remaining	O
Datakit	B-General_Concept
users	O
and	O
provide	O
gateway	O
solutions	O
to	O
assist	O
in	O
their	O
migration	O
to	O
newer	O
technologies	O
.	O
</s>
<s>
In	O
part	O
due	O
to	O
the	O
continuing	O
decline	O
in	O
Datakit	B-General_Concept
use	O
,	O
Datatek	O
Applications	O
went	O
out	O
of	O
business	O
in	O
January	O
2018	O
.	O
</s>
