<s>
Microsoft	B-Device
Point-to-Point	I-Device
Compression	I-Device
(	O
MPPC	O
;	O
described	O
in	O
RFC	O
2118	O
)	O
is	O
a	O
streaming	B-Operating_System
data	I-Operating_System
compression	B-General_Concept
algorithm	I-General_Concept
based	O
on	O
an	O
implementation	O
of	O
Lempel	B-Algorithm
–	I-Algorithm
Ziv	I-Algorithm
using	O
a	O
sliding	O
window	O
buffer	O
.	O
</s>
<s>
The	O
dialup	O
modem	B-Application
's	O
in-built	O
compression	B-General_Concept
(	O
V.44	O
or	O
V.42bis	O
)	O
can	O
only	O
occur	O
after	O
the	O
data	O
has	O
been	O
serially	O
transmitted	O
to	O
the	O
modem	B-Application
,	O
typically	O
at	O
a	O
maximum	O
rate	O
of	O
115,200	O
bit/s	O
.	O
</s>
<s>
MPPC	O
,	O
as	O
it	O
is	O
controlled	O
by	O
the	O
operating	B-General_Concept
system	I-General_Concept
,	O
can	O
receive	O
as	O
much	O
data	O
as	O
it	O
wishes	O
to	O
compress	O
,	O
before	O
forwarding	O
it	O
on	O
to	O
the	O
modem	B-Application
.	O
</s>
<s>
The	O
modem	B-Application
's	O
hardware	O
must	O
not	O
delay	O
data	O
too	O
much	O
,	O
while	O
waiting	O
for	O
more	O
to	O
compress	O
in	O
one	O
packet	O
,	O
otherwise	O
an	O
unacceptable	O
latency	O
level	O
will	O
result	O
.	O
</s>
<s>
It	O
also	O
cannot	O
afford	O
to	O
,	O
as	O
this	O
would	O
require	O
both	O
sizable	O
computing	O
resources	O
(	O
on	O
the	O
scale	O
of	O
a	O
modem	B-Application
)	O
as	O
well	O
as	O
significant	O
buffer	O
RAM	B-Architecture
.	O
</s>
<s>
Software	O
compression	B-General_Concept
such	O
as	O
MPPC	O
is	O
free	O
to	O
use	O
the	O
host	O
computer	O
's	O
resources	O
,	O
exceeding	O
the	O
modem	B-Application
's	O
by	O
several	O
orders	O
of	O
magnitude	O
.	O
</s>
<s>
The	O
end	O
result	O
is	O
that	O
where	O
V.44	O
may	O
achieve	O
a	O
maximum	O
of	O
4:1	O
compression	B-General_Concept
(	O
230	O
kbit/s	O
)	O
but	O
is	O
usually	O
limited	O
to	O
115.2	O
kbit/s	O
,	O
MPPC	O
is	O
capable	O
of	O
a	O
maximum	O
of	O
8:1	O
compression	B-General_Concept
(	O
460	O
kbit/s	O
)	O
.	O
</s>
<s>
MPPC	O
also	O
,	O
given	O
the	O
far	O
greater	O
computing	O
power	O
at	O
its	O
disposal	O
,	O
is	O
more	O
effective	O
on	O
data	O
than	O
V.44	O
and	O
achieves	O
higher	O
compression	B-General_Concept
ratios	O
when	O
8:1	O
is	O
n't	O
achievable	O
.	O
</s>
