mscGsmBcModemOutbandFlowControl 1.3.6.1.4.1.562.36.2.1.128.4.10.1.12

This attribute indicates whether inband or outband flow control conversions are being performed. The modem performs either inband or outband flow control unless V.42 layer is active, it is a fax call, or no flow control was specified by the MSC.