Method appendTiPd

SGSNGGSN/GPRSL3Messages.cpp:1262–1274

3GPP 24.007 11.2.3.1.3 Transaction Identifier. First bit is the TIflag that must be set for a message reply. And I quote: "A message has a TI flag set to "0" when it belongs to transaction initiated by its sender, and to "1" otherwise." Transaction id values > 7 requre an extension byte.

// and to "1" otherwise."
// Transaction id values > 7 requre an extension byte.
void L3SmDlMsg::appendTiPd(ByteVector &msg)
{
	unsigned tiFlag = isSenseCmd() ? 0 : 0x8;
	// Note: nibbles are reversed, as always for L3 messages.
	if (mTransactionId < 7) {
		msg.appendField(tiFlag|mTransactionId,4);	// Transaction id.  The 0x8 indicates this is a command.
		msg.appendField(GSM::L3GPRSSessionManagementPD,4);	// protocol discriminator.
	} else {
		msg.appendField(tiFlag|0x7,4);	// Magic value indicates additional transaction id field present.
		msg.appendField(GSM::L3GPRSSessionManagementPD,4);	// protocol discriminator.
		msg.appendByte(0x80|mTransactionId);	// The 0x80 is a required but meaningless extension indicator.
	}
}


void L3SmMsgActivatePdpContextAccept::smWriteBody(ByteVector &msg)