TC minimum and maximum "classid" and "flowid" Playing a lot with TC on Linux, I one time wondered what is the min and max value of the "classid" and "flowid". Looking to the man page, I found: IDs consist of a major number and a minor number, separated by a colon - major : minor . Both major and minor are hexadecimal numbers and are limited to 16 bits . There are two special values: root is signified by major and minor of all ones, and unspecified is all zeros. Well, to get more precise, I also put here what is the relationship between hexadecimal and bits : Hexadecimal numerals are widely used by computer system designers and programmers. As each hexadecimal digit represents four binary digits ( bits ), it allows a more human-friendly representation of binary-coded values. One hexadecimal digit represents a nibble (4 bits), which is half of an octet or byte (8 bits) I hope this helped to understand several details we someti