Page 6, draft feb 2011

def _getTrafficClassAndFlowLabel(self):
        """Page 6, draft feb 2011 """
        if self.tf == 0x0:
            return (self.tc_ecn << 6) + self.tc_dscp, self.flowlabel
        elif self.tf == 0x1:
            return (self.tc_ecn << 6), self.flowlabel
        elif self.tf == 0x2:
            return (self.tc_ecn << 6) + self.tc_dscp, 0
        else:
            return 0, 0