Paradyne 3800PLUS - Manual (Page 201)

Synchronous Data Compression
I-3 3980-A2-GB30-40 October 1998
Table I-1
SDC Negotiation Configuration Scenarios
Originating Modem Answering Modem Negotiation Results
SDC enabled with LAPM_Buffer
negotiation. SDC enabled. SDC connection.
SDC enabled with LAPM_Discon
negotiation. SDC enabled. SDC connection.
SDC enabled with LAPM_Buffer
negotiation. SDC disabled. Buffer mode connection. *
SDC enabled with LAPM_Discon
negotiation. SDC disabled. Disconnect. **
SDC disabled. SDC enabled with LAPM_Buffer
negotiation. Buffer mode connection. *
SDC disabled. SDC enabled with LAPM_Discon
negotiation. Disconnect. ***
* If during the negotiation phase, the modem with SDC enabled receives data from the remote modem indicating that it
has SDC disabled, the link will not be established between the two modems. For example, the link will not be
established if the remote modem is configured for Async mode with an EC mode of V42/MNPorBfr, V42/MNPorDsc,
LAPM_Buffer, or LAPM_Discon.
** On a leased line, the originating modem sends an endless EC negotiation sequence with the SDC request parameter.
Data cannot be successfully transmitted.
*** On a leased line, the answering modem waits indefinitely for an EC negotiation sequence with an SDC request
parameter. Data cannot be successfully transmitted.
Table I-2
SDC Performance Measurements
Group DTE Rate Compression Ratio Line Efficiency
TX The number of bits per second
received from the DTE. This
number takes into account only the
data between the opening and
closing flags of the HDLC frames.
Flags and DTE interframe time fill
are ignored. The ratio between the number of
bits in the input and output of the
compression algorithm. The
calculation does not include the
overhead of the LAPM frame or the
DTE flags and DTE interframe time
fill. The ratio between the number
of bits per second sent on the
line, and the line rate. The
calculation does not include the
DCE interframe time fill.
RX The number of bits per second
sent to the DTE. This number
takes into account only the data
between the opening and closing
flags of the HDLC frames. Flags
and DTE interframe time fill are
ignored. The ratio between the number of
bits in the output and input of the
decompression algorithm. The
calculation does not include the
overhead of the LAPM frame or the
DTE flags and DTE interframe time
fill. The ratio between the number
of bits per second received
from the line, and the line rate.
The calculation does not
include the DCE interframe
time fill.