dscp and ip precedence...

i am only scratching the surface of this, and i'm finding it's mostly not that complicated...

ip precedence is fairly simple, 0 to 7, with 0 being the lowest priority or best effort, and increasing the numbers the higher the priority (i do like the numbers, but i also like logic with the numbers, you'll see what i mean as we move along)

the class selector follows this logic...

cs0 is binary 000000 which translates to decimal 0 and has ip precedence 0
beautiful

cs1 increases to binary 001000 which translates to decimal 8 and has an ip precedence of 1
there are only 6 place holders, imagine the two leading zeros

if you are shaky on binary to decimal remember 128 64 32 16 8 4 2 1
                                                                                  0   0   0   0  1 0 0 0

                                            

so the ip precedence increases by 1 and follows the class selector...

hence, cs2  has an ip precedence of 2, cs3 has an ip precedence of 3, and so on up to cs7

also as the class selector increases by one, it's decimal value increases by 8 and is followed by the binary value

again cs0 is zero across the board
cs1 has increased by 1 from zero and it's ds value has increased to decimal 8 or  binary 001000

cs2 is academic... ip precedence is now 2, and it has increased by 8 so the decimal value (it's ds field value) is now 16, binary 010000

cs3, ip precedence 3, increase another 8 to decimal 24 with the binary translation 011000

cs4, 5, 6 and 7 all follow the same logic which gives cs7 an ip precedence of 7, and ds field value decimal 56 or 111000
7 times 8 is 56 or 32 + 16 + 8 + 0 + 0 + 0 = 56

see chart below... thanks to http://bogpeople.com/networking/dscp.shtml

DSCP <=> IP Precedence Conversion Table

DSCP Name	DS Field Value		IP Precedence
	Binary	Decimal
CS0	000 000	0	0
CS1	001 000	8	1
AF11	001 010	10	1
AF12	001 100	12	1
AF13	001 110	14	1
CS2	010 000	16	2
AF21	010 010	18	2
AF22	010 100	20	2
AF23	010 110	22	2
CS3	011 000	24	3
AF31	011 010	26	3
AF32	011 100	28	3
AF33	011 110	30	3
CS4	100 000	32	4
AF41	100 010	34	4
AF42	100 100	36	4
AF43	100 110	38	4
CS5	101 000	40	5
EF	101 110	46	5
CS6	110 000	48	6
CS7	111 000	56	7

CS	Class Selector (RFC 2474)
AFxy	Assured Forwarding (x=class, y=drop precedence) (RFC2597)
EF	Expedited Forwarding (RFC 3246)