Paradyne COMSPHERE 3920PLUS Series, Техническое справочное руководство

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Synchronous Data Compression
H-3 3920-A2-GH30-40 October 1998
DTE and DCE Frames
Data exchanged between the local and remote DCEs is according to the LAPM protocol. The
structure of a LAPM frame (DCE frame) is identical to the HDLC frame. The data from the DTE
is compressed into the information field of the DCE frame. After compression, one DTE frame is
segmented into one or several DCE frames.
SDC User Interface
When SDC is enabled, the following configuration options are available to set up the SDC feature.
V.42/MNP/Buffer
•
Sync Comp Mode
•
SDC Negotiation
•
SDC Idle Fill
•
SDC Bit Encoding
•
Sync DTE CRC
•
SDC Delay Min
•
Sync Flow Control
•
Buffer Disc Delay
•
Max Frame Size
•
Cellular Enhance
DTE Interface
•
Sync DTE Rate
•
Tx Clock Source
•
Bakup_TXClk_Src
Refer to Chapter 5, Configure Branch , for more information on the above configuration options.
SDC Configuration Options Considerations:
When the Sync Comp Mode configuration option is not set to Direct, the SDC Idle Fill
configuration option is available. The Flag_Fill setting is the default and causes the modem to fill
the time between frames with HDLC flags; the Mark_Fill setting fills the time between frame
transfers with marks.
When the Sync Comp Mode configuration option is not set to DirectMode, the SDC Bit Encoding
configuration option is available. The NRZ setting is the default and causes the modem to use the
standard Non Return to Zero bit encoding scheme. The NRZI setting causes the modem to use the
Non Return to Zero Inverted bit encoding scheme.