<s>
The	O
Microcom	B-Device
Networking	I-Device
Protocols	I-Device
,	O
almost	O
always	O
shortened	O
to	O
MNP	O
,	O
is	O
a	O
family	O
of	O
error-correcting	O
protocols	O
commonly	O
used	O
on	O
early	O
high-speed	O
(	O
2400	O
bit/s	O
and	O
higher	O
)	O
modems	B-Application
.	O
</s>
<s>
Originally	O
developed	O
for	O
use	O
on	O
Microcom	O
's	O
own	O
family	O
of	O
modems	B-Application
,	O
the	O
protocol	O
was	O
later	O
openly	O
licensed	O
and	O
used	O
by	O
most	O
of	O
the	O
modem	B-Application
industry	O
,	O
notably	O
the	O
"	O
big	O
three	O
"	O
,	O
Telebit	O
,	O
USRobotics	O
and	O
Hayes	O
.	O
</s>
<s>
MNP	O
was	O
later	O
supplanted	O
by	O
v.42bis	O
,	O
which	O
was	O
used	O
almost	O
universally	O
starting	O
with	O
the	O
first	O
v.32bis	O
modems	B-Application
in	O
the	O
early	O
1990s	O
.	O
</s>
<s>
Although	O
Xmodem	B-Protocol
was	O
introduced	O
1977	O
,	O
as	O
late	O
as	O
1985	O
The	O
New	O
York	O
Times	O
described	O
XMODEM	B-Protocol
first	O
,	O
then	O
discussed	O
MNP	O
as	O
a	O
leading	O
contender	O
,	O
and	O
that	O
9600	O
baud	O
modems	B-Application
"	O
are	O
beginning	O
to	O
make	O
their	O
appearance.	O
"	O
</s>
<s>
By	O
1988	O
,	O
the	O
Times	O
was	O
talking	O
about	O
9600	O
and	O
19.2K	O
,	O
and	O
that	O
"	O
At	O
least	O
100	O
other	O
brands	O
of	O
modems	B-Application
follow	O
"	O
MNP	O
(	O
compared	O
to	O
Hayes	O
 '	O
use	O
of	O
LAP-B	O
)	O
.	O
</s>
<s>
Modems	B-Application
are	O
,	O
by	O
their	O
nature	O
,	O
error-prone	O
devices	O
.	O
</s>
<s>
Noise	O
on	O
the	O
telephone	O
line	O
,	O
a	O
common	O
occurrence	O
,	O
can	O
easily	O
mimic	O
the	O
sounds	O
used	O
by	O
the	O
modems	B-Application
to	O
transmit	O
data	O
,	O
thereby	O
introducing	O
errors	O
that	O
are	O
difficult	O
to	O
notice	O
.	O
</s>
<s>
As	O
modems	B-Application
increase	O
in	O
speed	O
by	O
using	O
up	O
more	O
of	O
the	O
available	O
bandwidth	B-Algorithm
,	O
the	O
chance	O
that	O
random	O
noise	O
would	O
introduce	O
errors	O
also	O
increases	O
;	O
above	O
2400	O
bit/s	O
these	O
errors	O
are	O
quite	O
common	O
.	O
</s>
<s>
To	O
deal	O
with	O
this	O
problem	O
,	O
a	O
number	O
of	O
file	B-Protocol
transfer	I-Protocol
protocols	I-Protocol
were	O
introduced	O
and	O
implemented	O
in	O
various	O
programs	O
.	O
</s>
<s>
In	O
general	O
,	O
these	O
protocols	O
break	O
down	O
a	O
file	O
into	O
a	O
series	O
of	O
frames	O
or	O
packets	B-Protocol
containing	O
a	O
number	O
of	O
bytes	B-Application
from	O
the	O
original	O
file	O
.	O
</s>
<s>
Some	O
sort	O
of	O
additional	O
data	O
,	O
normally	O
a	O
checksum	B-Algorithm
or	O
CRC	O
,	O
is	O
added	O
to	O
each	O
packet	B-Protocol
to	O
indicate	O
whether	O
the	O
packet	B-Protocol
encountered	O
an	O
error	O
while	O
being	O
received	O
.	O
</s>
<s>
The	O
packet	B-Protocol
is	O
then	O
sent	O
to	O
the	O
remote	O
system	O
,	O
which	O
recomputes	O
the	O
checksum	B-Algorithm
or	O
CRC	O
of	O
the	O
data	O
and	O
compares	O
it	O
to	O
the	O
received	O
checksum	B-Algorithm
or	O
CRC	O
to	O
determine	O
if	O
it	O
was	O
received	O
properly	O
.	O
</s>
<s>
If	O
it	O
was	O
,	O
the	O
receiver	O
sends	O
back	O
an	O
ACK	B-Protocol
(	O
acknowledgement	B-Protocol
)	O
message	O
,	O
prompting	O
the	O
sender	O
to	O
send	O
the	O
next	O
packet	B-Protocol
.	O
</s>
<s>
If	O
there	O
was	O
any	O
problem	O
,	O
it	O
instead	O
sends	O
a	O
NAK	B-Protocol
(	O
not-acknowledged	O
)	O
message	O
,	O
and	O
the	O
sender	O
resends	O
the	O
damaged	O
packet	B-Protocol
.	O
</s>
<s>
For	O
one	O
,	O
the	O
additional	O
checksum	B-Algorithm
or	O
CRC	O
uses	O
up	O
time	O
in	O
the	O
channel	O
that	O
could	O
otherwise	O
be	O
used	O
to	O
send	O
additional	O
data	O
.	O
</s>
<s>
This	O
is	O
a	O
minor	O
concern	O
,	O
however	O
,	O
unless	O
the	O
packets	B-Protocol
are	O
very	O
small	O
(	O
which	O
they	O
are	O
in	O
UUCP	B-Protocol
for	O
instance	O
)	O
.	O
</s>
<s>
A	O
more	O
serious	O
concern	O
is	O
the	O
time	O
needed	O
for	O
the	O
receiver	O
to	O
examine	O
the	O
packet	B-Protocol
,	O
compare	O
it	O
to	O
the	O
CRC	O
,	O
and	O
then	O
send	O
the	O
ACK	B-Protocol
back	O
to	O
the	O
sender	O
.	O
</s>
<s>
This	O
delay	O
grows	O
in	O
relative	O
terms	O
as	O
the	O
speed	O
of	O
the	O
modem	B-Application
increases	O
;	O
the	O
latency	O
of	O
the	O
phone	O
line	O
is	O
a	O
constant	O
,	O
but	O
the	O
amount	O
of	O
data	O
that	O
could	O
be	O
sent	O
in	O
that	O
fixed	O
amount	O
of	O
time	O
grows	O
as	O
the	O
speed	O
increases	O
.	O
</s>
<s>
To	O
address	O
this	O
problem	O
,	O
newer	O
protocols	O
use	O
a	O
system	O
known	O
as	O
"	O
sliding	O
windows	O
"	O
,	O
allowing	O
the	O
sender	O
to	O
begin	O
transmitting	O
the	O
next	O
packet	B-Protocol
without	O
receiving	O
an	O
ACK	B-Protocol
message	O
;	O
only	O
if	O
the	O
ACK	B-Protocol
does	O
not	O
arrive	O
for	O
some	O
time	O
will	O
it	O
resend	O
the	O
packet	B-Protocol
.	O
</s>
<s>
MNP	O
connections	O
were	O
set	O
up	O
after	O
the	O
modems	B-Application
had	O
successfully	O
connected	O
.	O
</s>
<s>
The	O
originating	O
system	O
(	O
the	O
modem	B-Application
that	O
placed	O
the	O
call	O
,	O
or	O
sometimes	O
the	O
computer	O
it	O
was	O
connected	O
to	O
)	O
would	O
send	O
a	O
short	O
series	O
of	O
8-bit	O
characters	O
known	O
as	O
the	O
"	O
Originator	O
Detection	O
Pattern	O
"	O
(	O
ODP	O
)	O
.	O
</s>
<s>
If	O
the	O
answering	O
modem	B-Application
did	O
support	O
MNP	O
,	O
or	O
the	O
later	O
V.42	O
standards	O
that	O
superseded	O
it	O
,	O
it	O
responded	O
with	O
one	O
of	O
the	O
"	O
Answerer	O
Detection	O
Patterns	O
"	O
(	O
ADP	O
)	O
.	O
</s>
<s>
If	O
the	O
modem	B-Application
supported	O
compression	O
,	O
it	O
responded	O
with	O
the	O
8-bit	O
version	O
of	O
the	O
string	O
E$FF[$FF]C$FF[$FF],	O
indicating	O
"	O
EC	O
"	O
,	O
or	O
"	O
Error	O
correction	O
and	O
Compression	O
"	O
.	O
</s>
<s>
The	O
final	O
step	O
in	O
the	O
handshaking	O
process	O
is	O
to	O
send	O
an	O
MNP	O
packet	B-Protocol
containing	O
the	O
"	O
SABME	O
"	O
command	O
,	O
short	O
for	O
"	O
set	O
asynchronous	O
balanced	O
mode	O
extended	O
"	O
.	O
</s>
<s>
The	O
answering	O
system	O
responds	O
with	O
a	O
modified	O
version	O
of	O
the	O
same	O
packet	B-Protocol
,	O
switching	O
bits	O
in	O
the	O
data	O
to	O
indicate	O
it	O
is	O
successful	O
.	O
</s>
<s>
From	O
that	O
point	O
on	O
,	O
the	O
two	O
systems	O
exchange	O
data	O
using	O
the	O
error	O
correcting	O
packet	B-Protocol
protocol	O
.	O
</s>
<s>
Microcom	O
's	O
idea	O
was	O
to	O
move	O
the	O
file-transfer	O
protocol	O
out	O
of	O
the	O
host	O
computer	O
and	O
place	O
it	O
in	O
the	O
modem	B-Application
instead	O
.	O
</s>
<s>
The	O
first	O
MNP	O
standard	O
,	O
retroactively	O
known	O
as	O
MNP	O
Class	O
1	O
,	O
or	O
simply	O
MNP	O
1	O
,	O
was	O
a	O
simple	O
half-duplex	O
protocol	O
similar	O
to	O
XModem	B-Protocol
in	O
nature	O
.	O
</s>
<s>
That	O
meant	O
that	O
on	O
a	O
2400	O
bit/s	O
modem	B-Application
,	O
like	O
the	O
ones	O
Microcom	O
sold	O
,	O
throughput	O
would	O
be	O
limited	O
to	O
about	O
1690	O
bit/s	O
when	O
MNP1	O
was	O
in	O
use	O
.	O
</s>
<s>
With	O
low-cost	O
processing	O
power	O
improving	O
,	O
Microcom	O
introduced	O
MNP	O
2	O
,	O
a	O
full-duplex	O
version	O
of	O
MNP1	O
that	O
allowed	O
the	O
ACK	B-Protocol
messages	O
to	O
be	O
returned	O
while	O
the	O
next	O
outbound	O
packet	B-Protocol
was	O
already	O
starting	O
.	O
</s>
<s>
This	O
eliminated	O
the	O
pause	O
while	O
the	O
modem	B-Application
waited	O
for	O
the	O
ACK	B-Protocol
to	O
be	O
returned	O
,	O
adding	O
the	O
requirement	O
that	O
the	O
system	O
needed	O
some	O
memory	O
to	O
track	O
whether	O
or	O
not	O
an	O
ACK	B-Protocol
was	O
received	O
within	O
a	O
given	O
amount	O
of	O
time	O
.	O
</s>
<s>
Since	O
the	O
inter-packet	O
delay	O
was	O
reduced	O
,	O
only	O
the	O
overhead	O
of	O
the	O
CRC	O
remained	O
,	O
improving	O
throughput	O
to	O
about	O
84%	O
.	O
</s>
<s>
In	O
normal	O
use	O
,	O
a	O
modem	B-Application
can	O
send	O
or	O
receive	O
data	O
at	O
any	O
point	O
in	O
time	O
,	O
a	O
mode	O
of	O
operation	O
known	O
as	O
"	O
asynchronous	O
"	O
.	O
</s>
<s>
The	O
modem	B-Application
can	O
determine	O
the	O
speed	O
of	O
the	O
sender	O
's	O
data	O
by	O
listening	O
to	O
the	O
bits	O
being	O
sent	O
to	O
it	O
,	O
and	O
"	O
locking	O
"	O
its	O
clock	O
to	O
the	O
speed	O
of	O
bits	O
being	O
received	O
.	O
</s>
<s>
Unfortunately	O
,	O
this	O
sort	O
of	O
clock	O
decoding	O
does	O
not	O
work	O
unless	O
there	O
are	O
at	O
least	O
some	O
transitions	O
between	O
1	O
and	O
0	O
in	O
the	O
data	O
;	O
a	O
long	O
stream	O
of	O
0s	O
or	O
1s	O
has	O
no	O
transitions	O
in	O
it	O
,	O
making	O
it	O
impossible	O
to	O
know	O
where	O
the	O
data	O
for	O
any	O
particular	O
byte	B-Application
starts	O
.	O
</s>
<s>
In	O
order	O
to	O
avoid	O
this	O
problem	O
,	O
additional	O
framing	O
bits	O
are	O
added	O
to	O
either	O
end	O
of	O
every	O
byte	B-Application
,	O
typically	O
one	O
bit	O
on	O
either	O
side	O
known	O
as	O
the	O
"	O
start	O
and	O
stop	O
bits	O
"	O
.	O
</s>
<s>
This	O
guarantees	O
at	O
least	O
one	O
1-to-0	O
transition	O
for	O
every	O
byte	B-Application
,	O
more	O
than	O
enough	O
to	O
keep	O
the	O
clocks	O
locked	O
.	O
</s>
<s>
However	O
,	O
these	O
bits	O
also	O
expand	O
every	O
8	O
bits	O
of	O
data	O
(	O
one	O
byte	B-Application
)	O
to	O
10	O
bits	O
,	O
an	O
overhead	O
of	O
20%	O
.	O
</s>
<s>
When	O
using	O
a	O
file	B-Protocol
transfer	I-Protocol
protocol	I-Protocol
,	O
the	O
packets	B-Protocol
themselves	O
offer	O
their	O
own	O
framing	O
.	O
</s>
<s>
The	O
packets	B-Protocol
will	O
always	O
send	O
a	O
continuous	O
stream	O
of	O
data	O
,	O
so	O
the	O
clock	O
cannot	O
"	O
drift	O
"	O
in	O
the	O
same	O
way	O
that	O
it	O
could	O
for	O
data	O
being	O
sent	O
by	O
a	O
user	O
typing	O
on	O
a	O
keyboard	O
.	O
</s>
<s>
After	O
negotiating	O
and	O
determining	O
that	O
both	O
modems	B-Application
supported	O
MNP3	O
,	O
the	O
framing	O
bits	O
were	O
turned	O
off	O
,	O
improving	O
overall	O
efficiency	O
by	O
about	O
20%	O
.	O
</s>
<s>
MNP	O
4	O
was	O
a	O
further	O
improvement	O
on	O
MNP3	O
,	O
adding	O
a	O
variable	O
packet	B-Protocol
size	O
system	O
they	O
referred	O
to	O
as	O
Adaptive	O
Packet	B-Protocol
Assembly	O
.	O
</s>
<s>
In	O
the	O
case	O
of	O
MNP	O
the	O
overhead	O
of	O
the	O
packet	B-Protocol
system	O
was	O
relatively	O
small	O
,	O
but	O
even	O
the	O
multi-byte	O
CRC	O
was	O
taking	O
up	O
space	O
better	O
used	O
for	O
data	O
.	O
</s>
<s>
Generally	O
using	O
a	O
larger	O
packet	B-Protocol
would	O
address	O
this	O
,	O
because	O
the	O
CRC	O
remains	O
the	O
same	O
fixed	O
size	O
and	O
thus	O
its	O
relative	O
overhead	O
is	O
reduced	O
compared	O
to	O
the	O
amount	O
of	O
data	O
.	O
</s>
<s>
However	O
,	O
when	O
an	O
error	O
does	O
occur	O
,	O
using	O
larger	O
packets	B-Protocol
also	O
means	O
that	O
more	O
data	O
has	O
to	O
be	O
re-sent	O
.	O
</s>
<s>
With	O
MNP4	O
the	O
two	O
modems	B-Application
constantly	O
monitor	O
the	O
line	O
for	O
dropped	O
packets	B-Protocol
,	O
and	O
if	O
a	O
certain	O
threshold	O
is	O
crossed	O
(	O
selected	O
by	O
the	O
user	O
)	O
,	O
the	O
modem	B-Application
drops	O
back	O
to	O
a	O
smaller	O
packet	B-Protocol
size	O
.	O
</s>
<s>
This	O
means	O
that	O
when	O
a	O
packet	B-Protocol
is	O
dropped	O
,	O
the	O
amount	O
of	O
data	O
that	O
has	O
to	O
be	O
re-sent	O
is	O
smaller	O
,	O
leading	O
to	O
better	O
throughput	O
.	O
</s>
<s>
On	O
good	O
quality	O
lines	O
,	O
using	O
larger	O
packets	B-Protocol
means	O
that	O
the	O
overhead	O
of	O
the	O
CRC	O
is	O
reduced	O
.	O
</s>
<s>
Packets	B-Protocol
could	O
be	O
between	O
64	O
and	O
256	O
bytes	B-Application
,	O
and	O
allowed	O
the	O
user	O
to	O
force	O
it	O
to	O
a	O
particular	O
size	O
if	O
they	O
wished	O
.	O
</s>
<s>
MNP4	O
also	O
introduced	O
Data	O
Phase	O
Optimization	O
,	O
a	O
simple	O
change	O
to	O
the	O
protocol	O
that	O
allowed	O
some	O
of	O
the	O
packet-framing	O
information	O
to	O
be	O
dropped	O
after	O
the	O
link	O
was	O
set	O
up	O
,	O
further	O
reducing	O
protocol	O
overhead	O
.	O
</s>
<s>
The	O
combination	O
of	O
these	O
features	O
,	O
along	O
with	O
MNP3	O
's	O
lack	O
of	O
byte-framing	O
,	O
allowed	O
for	O
a	O
further	O
increase	O
in	O
throughput	O
efficiency	O
.	O
</s>
<s>
An	O
even	O
more	O
radical	O
change	O
was	O
made	O
for	O
MNP	O
5	O
,	O
introducing	O
on-the-fly	O
data	B-General_Concept
compression	I-General_Concept
in	O
the	O
modem	B-Application
.	O
</s>
<s>
With	O
MNP5	B-Device
,	O
the	O
data	O
received	O
from	O
the	O
computer	O
are	O
first	O
compressed	O
with	O
a	O
simple	O
algorithm	O
,	O
and	O
then	O
passed	O
into	O
the	O
MNP4	O
packetizing	O
system	O
for	O
transmission	O
.	O
</s>
<s>
As	O
a	O
result	O
,	O
a	O
2400	O
bit/s	O
modem	B-Application
would	O
appear	O
to	O
transfer	O
text	O
at	O
~	O
4000	O
bit/s	O
.	O
</s>
<s>
This	O
dramatic	O
increase	O
in	O
throughput	O
allowed	O
Microcom	O
modems	B-Application
to	O
remain	O
somewhat	O
competitive	O
with	O
models	O
from	O
other	O
companies	O
that	O
were	O
otherwise	O
nominally	O
much	O
faster	O
.	O
</s>
<s>
For	O
instance	O
,	O
Microcom	O
generally	O
produced	O
1200	O
and	O
2400	O
bit/s	O
modems	B-Application
using	O
commodity	O
parts	O
,	O
while	O
companies	O
like	O
USRobotics	O
and	O
Telebit	O
offered	O
models	O
with	O
speeds	O
up	O
to	O
19200	O
bit/s	O
.	O
</s>
<s>
However	O
,	O
this	O
improvement	O
in	O
performance	O
was	O
only	O
available	O
if	O
modems	B-Application
on	O
both	O
ends	O
supported	O
MNP	O
.	O
</s>
<s>
That	O
made	O
the	O
system	O
only	O
really	O
attractive	O
for	O
sites	O
installing	O
the	O
modems	B-Application
at	O
both	O
ends	O
of	O
the	O
links	O
;	O
for	O
dial-up	O
services	O
like	O
bulletin	B-Application
board	I-Application
systems	I-Application
(	O
BBS	O
)	O
there	O
was	O
no	O
compelling	O
reason	O
to	O
use	O
a	O
Microcom	O
device	O
when	O
the	O
end-user	O
was	O
unlikely	O
to	O
have	O
one	O
.	O
</s>
<s>
Even	O
in	O
the	O
cases	O
where	O
the	O
user	O
was	O
in	O
control	O
of	O
both	O
ends	O
of	O
the	O
link	O
,	O
Microcom	O
's	O
"	O
proprietary	O
"	O
modems	B-Application
were	O
less	O
interesting	O
than	O
models	O
from	O
other	O
companies	O
that	O
offered	O
much	O
higher	O
"	O
real	O
world	O
"	O
throughputs	O
.	O
</s>
<s>
In	O
order	O
to	O
create	O
a	O
market	O
for	O
Microcom	O
modems	B-Application
,	O
starting	O
with	O
MNP5	B-Device
they	O
took	O
the	O
radical	O
step	O
of	O
licensing	O
the	O
entire	O
MNP	O
suite	O
for	O
free	O
.	O
</s>
<s>
The	O
idea	O
was	O
that	O
this	O
would	O
dramatically	O
increase	O
the	O
number	O
of	O
modems	B-Application
with	O
MNP	O
installed	O
,	O
making	O
"	O
real	O
"	O
Microcom	O
modems	B-Application
more	O
attractive	O
.	O
</s>
<s>
Moreover	O
,	O
newer	O
standards	O
with	O
improved	O
performance	O
would	O
offer	O
even	O
better	O
performance	O
when	O
there	O
was	O
a	O
Microcom	O
modem	B-Application
at	O
both	O
ends	O
of	O
the	O
link	O
.	O
</s>
<s>
The	O
introduction	O
of	O
the	O
greatly	O
improved	O
LAPM	B-Protocol
compression	O
system	O
in	O
the	O
v.42bis	O
standard	O
outpaced	O
Microcom	O
's	O
own	O
advancements	O
,	O
diluting	O
the	O
value	O
of	O
a	O
"	O
real	O
"	O
Microcom	O
model	O
almost	O
to	O
zero	O
.	O
</s>
<s>
Using	O
v.42bis	O
and	O
commodity	O
parts	O
,	O
a	O
huge	O
number	O
of	O
low-cost	O
modems	B-Application
with	O
even	O
better	O
performance	O
that	O
Microcom	O
's	O
were	O
soon	O
available	O
.	O
</s>
<s>
The	O
introduction	O
of	O
the	O
v.32	O
led	O
to	O
a	O
number	O
of	O
standard	O
9600	O
bit/s	O
modems	B-Application
,	O
almost	O
all	O
of	O
which	O
offered	O
MNP5	B-Device
.	O
</s>
<s>
To	O
further	O
differentiate	O
themselves	O
from	O
what	O
was	O
becoming	O
a	O
commodity	O
market	O
(	O
although	O
not	O
truly	O
so	O
until	O
the	O
introduction	O
of	O
the	O
v.32bis	O
SupraFAXModem	B-Device
14400	I-Device
in	O
1991	O
)	O
,	O
Microcom	O
created	O
MNP	O
6	O
.	O
</s>
<s>
MNP6	O
's	O
main	O
feature	O
was	O
Statistical	O
Duplexing	O
,	O
which	O
could	O
dedicate	O
more	O
or	O
less	O
of	O
the	O
bandwidth	B-Algorithm
to	O
one	O
side	O
or	O
the	O
other	O
of	O
the	O
modem	B-Application
link	O
.	O
</s>
<s>
For	O
instance	O
,	O
if	O
one	O
machine	O
was	O
sending	O
a	O
large	O
file	O
,	O
the	O
other	O
end	O
would	O
only	O
send	O
back	O
a	O
small	O
amount	O
of	O
information	O
,	O
the	O
ACK	B-Protocol
and	O
NAK	B-Protocol
messages	O
.	O
</s>
<s>
In	O
this	O
case	O
the	O
modems	B-Application
would	O
give	O
as	O
much	O
of	O
the	O
channel	O
as	O
possible	O
to	O
the	O
sender	O
,	O
offering	O
one-way	O
bandwidth	B-Algorithm
up	O
to	O
19,200	O
bit/s	O
.	O
</s>
<s>
This	O
did	O
not	O
actually	O
require	O
any	O
changes	O
to	O
the	O
modulation	O
system	O
:	O
normally	O
a	O
9600	O
bit/s	O
modem	B-Application
had	O
a	O
full	O
9600	O
bit/s	O
channel	O
in	O
both	O
directions	O
,	O
for	O
a	O
total	O
of	O
19200	O
bit/s	O
;	O
MNP	O
6	O
simply	O
allowed	O
more	O
or	O
less	O
of	O
that	O
bandwidth	B-Algorithm
to	O
be	O
given	O
to	O
one	O
side	O
or	O
the	O
other	O
,	O
instead	O
of	O
leaving	O
it	O
fixed	O
at	O
9600	O
both	O
ways	O
.	O
</s>
<s>
This	O
basic	O
concept	O
was	O
already	O
widely	O
used	O
in	O
the	O
industry	O
,	O
having	O
formed	O
the	O
basis	O
for	O
Hayes	O
's	O
Express	O
96	O
protocol	O
,	O
USRobotics	O
 '	O
HST	O
Telebit	O
's	O
PEP	O
,	O
and	O
(	O
briefly	O
)	O
the	O
CompuCom	B-Device
SpeedModem	I-Device
.	O
</s>
<s>
With	O
the	O
introduction	O
of	O
additional	O
modulation	O
modes	O
,	O
notably	O
v.32	O
and	O
later	O
additions	O
,	O
the	O
modems	B-Application
on	O
either	O
end	O
of	O
the	O
link	O
had	O
to	O
spend	O
an	O
increasing	O
amount	O
of	O
time	O
negotiating	O
a	O
common	O
standard	O
.	O
</s>
<s>
For	O
instance	O
,	O
a	O
v.32bis	O
modem	B-Application
would	O
first	O
send	O
tones	O
into	O
the	O
line	O
to	O
try	O
to	O
get	O
a	O
14.4	O
link	O
;	O
if	O
that	O
failed	O
after	O
a	O
time	O
,	O
it	O
would	O
try	O
9600	O
,	O
2400	O
and	O
finally	O
1200	O
bit/s	O
.	O
</s>
<s>
Although	O
this	O
eliminated	O
compatibility	O
with	O
older	O
1200	O
bit/s	O
modems	B-Application
,	O
by	O
this	O
point	O
in	O
time	O
they	O
were	O
extremely	O
rare	O
.	O
</s>
<s>
Once	O
the	O
connection	O
was	O
made	O
,	O
which	O
occurred	O
quickly	O
,	O
both	O
modems	B-Application
sent	O
a	O
small	O
identification	O
string	O
to	O
the	O
remote	O
modem	B-Application
.	O
</s>
<s>
Both	O
modems	B-Application
then	O
examined	O
the	O
string	O
and	O
selected	O
the	O
fastest	O
common	O
mode	O
.	O
</s>
<s>
MNP	O
7	O
introduced	O
new	O
compression	B-General_Concept
algorithms	I-General_Concept
with	O
a	O
claimed	O
improvement	O
to	O
3:1	O
compression	O
on	O
text	O
files	O
.	O
</s>
<s>
Unlike	O
earlier	O
versions	O
like	O
MNP4	O
,	O
MNP10	O
constantly	O
monitored	O
line	O
quality	O
and	O
adjusted	O
packet	B-Protocol
size	O
back	O
up	O
if	O
conditions	O
improved	O
.	O
</s>
<s>
In	O
1991	O
Microcom	O
licensed	O
MNP10	O
to	O
Rockwell	O
International	O
for	O
use	O
in	O
their	O
extremely	O
popular	O
modem	B-Application
chip	O
sets	O
.	O
</s>
<s>
Since	O
almost	O
all	O
modems	B-Application
with	O
the	O
exception	O
of	O
USR	O
's	O
models	O
used	O
the	O
Rockwell	O
chipset	O
from	O
about	O
1995	O
,	O
MNP10	O
became	O
fairly	O
widely	O
deployed	O
(	O
if	O
not	O
used	O
)	O
.	O
</s>
<s>
USR	O
eventually	O
added	O
MNP10	O
to	O
their	O
V.everything	O
series	O
modems	B-Application
,	O
effectively	O
making	O
it	O
universal	O
.	O
</s>
<s>
MNP10EC	O
had	O
a	O
limited	O
life	O
span	O
,	O
as	O
the	O
cell	O
networks	O
turned	O
to	O
a	O
variety	O
of	O
all-digital	O
systems	O
that	O
no	O
longer	O
required	O
a	O
modem	B-Application
to	O
connect	O
to	O
a	O
computer	O
.	O
</s>
