<s>
For	O
data	B-General_Concept
compression	I-General_Concept
,	O
Signaling	B-Protocol
compression	I-Protocol
,	O
or	O
SigComp	B-Protocol
,	O
is	O
a	O
compression	O
method	O
designed	O
especially	O
for	O
compression	O
of	O
text-based	O
communication	O
data	O
as	O
SIP	B-Application
or	O
RTSP	B-Protocol
.	O
</s>
<s>
SigComp	B-Protocol
had	O
originally	O
been	O
defined	O
in	O
RFC	O
3320	O
and	O
was	O
later	O
updated	O
with	O
RFC	O
4896	O
.	O
</s>
<s>
A	O
Negative	O
Acknowledgement	O
Mechanism	O
for	O
Signaling	B-Protocol
Compression	I-Protocol
is	O
defined	O
in	O
RFC	O
4077	O
.	O
</s>
<s>
The	O
SigComp	B-Protocol
work	O
is	O
performed	O
in	O
the	O
ROHC	O
working	O
group	O
in	O
the	O
transport	O
area	O
of	O
the	O
IETF	O
.	O
</s>
<s>
SigComp	B-Protocol
specifications	O
describe	O
a	O
compression	O
schema	O
that	O
is	O
located	O
in	O
between	O
the	O
application	O
layer	O
and	O
the	O
transport	O
layer	O
(	O
e.g.	O
</s>
<s>
between	O
SIP	B-Application
and	O
UDP	O
)	O
.	O
</s>
<s>
One	O
strong	O
point	O
for	O
SigComp	B-Protocol
is	O
that	O
the	O
bytecode	O
to	O
decode	O
messages	O
can	O
be	O
sent	O
over	O
SigComp	B-Protocol
itself	O
,	O
so	O
this	O
allows	O
to	O
use	O
any	O
kind	O
of	O
compression	O
schema	O
given	O
that	O
it	O
is	O
expressed	O
as	O
bytecode	O
for	O
the	O
UDVM	O
.	O
</s>
<s>
Thus	O
any	O
SigComp	B-Protocol
compatible	O
device	O
may	O
use	O
compression	O
mechanisms	O
that	O
did	O
not	O
exist	O
when	O
it	O
was	O
released	O
without	O
any	O
firmware	O
change	O
.	O
</s>
<s>
Additionally	O
,	O
some	O
decoders	O
may	O
be	O
already	O
been	O
standardised	O
,	O
so	O
SigComp	B-Protocol
may	O
recall	O
that	O
code	O
so	O
it	O
is	O
not	O
needed	O
to	O
be	O
sent	O
over	O
the	O
connection	O
.	O
</s>
<s>
a	O
given	O
SIP	B-Application
session	O
)	O
,	O
a	O
compartment	O
mechanism	O
is	O
used	O
,	O
so	O
a	O
given	O
application	O
may	O
have	O
any	O
given	O
number	O
of	O
different	O
,	O
independent	O
conversations	O
,	O
while	O
persisting	O
all	O
the	O
session	O
status	O
(	O
as	O
needed/specified	O
per	O
compression	O
schema	O
and	O
UDVM	O
code	O
)	O
.	O
</s>
