This attribute specifies the V.42bis data compression direction to be
supported. The value for compression direction is negotiated at link
setup by the data link protocol by way of the Exchange
Identification (XID) negotiation of parameter P0 (compression
direction).
During XID negotiation of parameter P0, both sides (IWF and
mobile or IWF and PSTN) agree on the compression direction.
This attribute has one of the following values:
noCompression: No compression is present.
compInitrResp: The data sent by the IWF to the other entity is
compressed.
compRespInitr: The data received by the IWF from the other entity
is compressed.
compBoth: The data sent and received by the IWF is compressed.
Changes to this attribute do not affect existing calls.