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Synchronous Data Compression

H-33920-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.

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Zhone 3920Plus Bedienerhandbuch Seite 329