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COURIER HIGH SPEED MODEMS
APPENDIX
A.
LINK NEGOTIATION (HANDSHAKING) AND ERROR
CONTROL
This
appendix
includes detailed information
on
how
USRobotics
HST
and
V.32
bis
modems
negotiate
with
remote
modems
for
the rate
and
other characteristics of each connection. You
may
find it helpful if
you
are
having
difficulty connecting
with
another
modem.
In
addition,
you'll find information
on
error
control
and,
especially useful,
some
statistics
and
guidelines
on
using
the
modem
for
the
best
throughput.
The following text relies
on
familiarity
with
two
terms
used
in
this
manual,
ARQ
and
DTE. ARQ (automatic
repeat
request)
designates a connection
under
error
control. DTE (data
terminating
equipment)
means
the
computer
or
terminal to
which
the
modem
is attached. DTE
rate
is
the
same
as
serial
port
rate.
LINK NEGOTIA T/ON (HANDSHAKING)
HST Mode
During
high-speed link negotiation, timing
and
procedures
differ for HST
or
V.32
bis
modulation,
as follows.
Serial
port
rate: 57.6K/38.4K/19.2K/9600
bps
(57.6K, 38.4K,
or
19.2K
required
for 16.BK
or
14.4K connections)
Modem
settings:
Bl,
&Bl,
&Hl/
&H2/
&H3,
&M4/
&MS,
&NO
1.
The
modems
begin
handshaking
by
training (synchronizing)
at
2400
bps
and
exchanging information
on
their
error
control,
data
compression,
and
speed
capabilities.
2.
Once
the
modems
enable
error
control,
handshaking
proceeds
as
follows.
If
the
remote
modem
is
operating
at
2400
bps
or
lower, the
Courier
stays
at
2400
bps
or
falls back
to
match
the
remote
modem's
slower rate.
If
the
remote
modem
is HST-compatible
and
operating
at
a
higher
speed,
both
modems
shift
up
and
train
at
9600 bps.
From
there,
depending
on
the
speed
of
the
remote
modem,
Link Negotiation and Error Control A-1
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