ip_dscp This specifies the dscp (differentiated services code point) value to be used in the IP header's type of service (TOS) field according to RFC 2474. Allowed values are 0-63 and symbolic dscp names cs0, cs1, cs2, cs3, cs4, cs5, cs6, cs7, af11, af12, af13, af21, af22, af23, af31, af32, af33, af41, af42, af43 and ef. Value 0 disables the dscp support. Use of TOS field then depends on the used transport. If ip_dscp is set to a value not equal to zero, and an appropriate socket option (IP_TOS) is available, the value is put into the upper six bits of the TOS header field.