<s>
Radio	B-Protocol
Link	I-Protocol
Protocol	I-Protocol
(	O
RLP	O
)	O
is	O
an	O
automatic	B-Error_Name
repeat	I-Error_Name
request	I-Error_Name
(	O
ARQ	B-Error_Name
)	O
fragmentation	O
protocol	O
used	O
over	O
a	O
wireless	O
(	O
typically	O
cellular	O
)	O
air	O
interface	O
.	O
</s>
<s>
Most	O
wireless	O
air	O
interfaces	O
are	O
tuned	O
to	O
provide	O
1%	O
packet	B-Protocol
loss	I-Protocol
,	O
and	O
most	O
Vocoders	B-Application
are	O
mutually	O
tuned	O
to	O
sacrifice	O
very	O
little	O
voice	O
quality	O
at	O
1%	O
packet	B-Protocol
loss	I-Protocol
.	O
</s>
<s>
However	O
,	O
1%	O
packet	B-Protocol
loss	I-Protocol
is	O
intolerable	O
to	O
all	O
variants	O
of	O
TCP	O
,	O
and	O
so	O
something	O
must	O
be	O
done	O
to	O
improve	O
reliability	O
for	O
voice	O
networks	O
carrying	O
TCP/IP	B-Protocol
data	O
.	O
</s>
<s>
A	O
RLP	O
detects	O
packet	B-Protocol
losses	I-Protocol
and	O
performs	O
retransmissions	O
to	O
bring	O
packet	B-Protocol
loss	I-Protocol
down	O
to	O
.01	O
%	O
,	O
or	O
even	O
.0001	O
%	O
,	O
which	O
is	O
suitable	O
for	O
TCP/IP	B-Protocol
applications	O
.	O
</s>
<s>
Newer	O
forms	O
of	O
RLP	O
also	O
provide	O
framing	O
and	O
compression	O
,	O
while	O
older	O
forms	O
of	O
RLP	O
rely	O
upon	O
a	O
higher-layer	O
PPP	B-Protocol
protocols	I-Protocol
to	O
provide	O
these	O
functions	O
.	O
</s>
<s>
Because	O
a	O
RLP	O
payload	O
size	O
can	O
be	O
as	O
little	O
as	O
11	O
bytes	O
,	O
based	O
upon	O
a	O
CDMA	B-Protocol
IS-95	O
network	O
's	O
smallest	O
voice	O
packet	O
size	O
,	O
RLP	O
headers	O
must	O
be	O
very	O
small	O
,	O
to	O
minimize	O
overhead	O
.	O
</s>
<s>
A	O
RLP	O
protocol	O
can	O
be	O
ACK-based	B-Protocol
or	I-Protocol
NAK-based	I-Protocol
.	O
</s>
<s>
Most	O
RLPs	O
are	O
NAK-based	O
,	O
meaning	O
that	O
forward-link	O
sender	O
assumes	O
that	O
each	O
transmission	O
got	O
through	O
,	O
and	O
the	O
receiver	O
only	O
NAKs	B-Protocol
when	O
an	O
out-of-order	O
segment	O
is	O
received	O
.	O
</s>
<s>
When	O
the	O
transmit	O
pipeline	O
goes	O
idle	O
,	O
a	O
NAK-based	O
RLP	O
must	O
eventually	O
retransmit	O
the	O
last	O
segment	O
a	O
second	O
time	O
,	O
in	O
case	O
the	O
last	O
fragment	O
was	O
lost	O
,	O
to	O
reach	O
a	O
.01	O
%	O
packet	B-Protocol
loss	I-Protocol
rate	O
.	O
</s>
<s>
The	O
concept	O
of	O
a	O
RLP	O
protocol	O
was	O
invented	O
by	O
Phil	O
Karn	O
in	O
1990	O
for	O
CDMA	B-Protocol
(	O
IS-95	O
)	O
networks	O
.	O
</s>
<s>
Cellular	O
networks	O
such	O
as	O
GSM	O
and	O
CDMA	B-Protocol
use	O
different	O
variations	O
of	O
RLP	O
.	O
</s>
<s>
In	O
UMTS	B-Protocol
and	O
in	O
LTE	O
,	O
the	O
protocol	O
is	O
called	O
RLC	O
(	O
Radio	O
Link	O
Control	O
)	O
.	O
</s>
