On the Flow-Tools email list, Craig Weinhold published a cheat sheet for how to treat IP Packet ToS (Type of Service) bits:
Continue reading "ToS/DSCP Cheat Sheet" »**** Pre-1998 The IPv4 ToS byte was part of the original 1981 definition of Internet Protocol in RFC 791, which specified a 3-bit precedence value and 3-bits of ToS attributes. In the tables below, "tos" values refer to the entire byte. In 1992, RFC 1349 added a fourth ToS attribute. 0x80 0x40 0x20 0x10 0x08 0x04 0x02 0x01 +-----+-----+-----+-----+-----+-----+-----+-----+ | PRECEDENCE | TOS attributes | - | +-----+-----+-----+-----+-----+-----+-----+-----+ PRECEDENCE TOS attributes name dec tos bin name dec tos bin network 7 224 111 min-delay 8 16 1000 internet 6 192 110 max-throughput 4 8 0100 critical 5 160 101 max-reliability 2 4 0010 flash-override 4 128 100 min-monetary-cost 1 2 0001 flash 3 96 011 normal 0 0 0000 immediate 2 64 010 priority 1 32 001 routine 0 0 000 **** Post-1998 RFC 2474 reworked the ToS as a 6-bit Differentiated Services Code Point (DSCP) and, soon after, RFC 3168 allocated the lowest two bits for Error Congestion Notification (ECN, an IP analogy of frame-relay FECN and ATM EFCI). 0x80 0x40 0x20 0x10 0x08 0x04 0x02 0x01 +-----+-----+-----+-----+-----+-----+-----+-----+ | DSCP | ECN | +-----+-----+-----+-----+-----+-----+-----+-----+ DSCP name dec tos binary name dec tos binary AF11 10 40 001010 CS1 8 32 001000 AF12 12 48 001100 CS2 16 64 010000 AF13 14 56 001110 CS3 24 96 011000 AF21 18 72 010010 CS4 32 128 100000 AF22 20 80 010100 CS5 40 160 101000 AF23 22 88 010110 CS6 48 192 110000 AF31 26 104 011010 CS7 56 224 111000 AF32 28 112 011100 EF 46 184 101110 AF33 30 120 011110 default 0 0 000000 AF41 34 136 100010 AF42 36 144 100100 AF = assured forwarding AF43 38 152 100110 EF = expedited forwarding CS = class selector ECN (unrelated to QoS) 00 Not-ECT Not ECN-Capable Transport 01 ECT(0) ECN-Capable Transport 10 ECT(1) ECN-Capable Transport 11 CE Congestion Experienced