<s>
SNDCP	B-Protocol
,	O
Sub	O
Network	O
Dependent	O
Convergence	O
Protocol	O
,	O
is	O
part	O
of	O
layer	B-Application
3	I-Application
of	O
a	O
GPRS	B-General_Concept
protocol	O
specification	O
.	O
</s>
<s>
SNDCP	B-Protocol
interfaces	O
to	O
the	O
Internet	B-Protocol
Protocol	I-Protocol
at	O
the	O
top	O
,	O
and	O
to	O
the	O
GPRS-specific	O
Logical	O
Link	O
Control	O
(	O
LLC	O
)	O
protocol	O
at	O
the	O
bottom	O
.	O
</s>
<s>
In	O
the	O
spirit	O
of	O
the	O
GPRS	B-General_Concept
specifications	O
,	O
there	O
can	O
be	O
many	O
implementations	O
of	O
SNDCP	B-Protocol
,	O
supporting	O
protocols	O
such	O
as	O
X.25	B-Protocol
.	O
</s>
<s>
However	O
,	O
in	O
reality	O
,	O
IP	O
(	O
Internet	B-Protocol
Protocol	I-Protocol
)	O
is	O
such	O
an	O
overwhelming	O
standard	O
that	O
X.25	B-Protocol
has	O
become	O
irrelevant	O
for	O
modern	O
applications	O
,	O
so	O
all	O
implementations	O
of	O
SNDCP	B-Protocol
for	O
GPRS	B-General_Concept
only	O
support	O
IP	O
as	O
the	O
payload	O
type	O
.	O
</s>
<s>
The	O
SNDCP	B-Protocol
layer	O
is	O
relevant	O
to	O
the	O
protocol	O
stack	O
of	O
the	O
mobile	O
station	O
and	O
that	O
of	O
the	O
SGSN	O
,	O
and	O
works	O
when	O
a	O
PDP	O
Context	O
is	O
established	O
and	O
the	O
quality	O
of	O
service	O
has	O
been	O
negotiated	O
.	O
</s>
<s>
The	O
SNDCP	B-Protocol
layer	O
primarily	O
converts	O
,	O
encapsulates	O
and	O
segments	O
external	O
network	O
formats	O
(	O
like	O
Internet	B-Protocol
Protocol	I-Protocol
Datagrams	O
)	O
into	O
sub-network	O
formats	O
(	O
called	O
SNPDUs	O
)	O
.	O
</s>
<s>
SNDCP	B-Protocol
provides	O
services	O
to	O
the	O
higher	O
layers	O
which	O
may	O
include	O
connectionless	O
and	O
connection-oriented	O
mode	O
,	O
compression	O
,	O
multiplexing	O
and	O
segmentation	O
.	O
</s>
