IP Precedence conversion table:
7
|
6
|
5
|
4
|
3
|
2
|
1
|
0
|
2^5
|
2^4
|
2^3
|
2^2
|
2^1
|
2^0
|
x
|
x
|
32
|
16
|
8
|
4
|
2
|
1
|
x
|
x
|
DSCP conversion table:
7
|
6
|
5
|
4
|
3
|
2
|
1
|
0
|
2^5
|
2^4
|
2^3
|
2^2
|
2^1
|
2^0
|
x
|
x
|
32
|
16
|
8
|
4
|
2
|
1
|
x
|
x
|
IP Precedence use only the 3 left-most bits, hence we will
start calculate only from bit 5 up to bit 7, Were DSCP uses only the 6
left-most bits, so calculation starts from bit 2 up to bit 7.
Example #1: DSCP to decimal
Let’s say we have AF41, first we will need to translate it
to decimal using the following formula:
(8 x X) + (2 x Y) - where X is the first number and Y is the
second number.
(8 x 4) + (2 x 1) = 32 + 2 = 34
So AF41 equals, in decimal, to 34
Now let’s use the conversion table to convert it to binary:
7
|
6
|
5
|
4
|
3
|
2
|
1
|
0
|
2^5
|
2^4
|
2^3
|
2^2
|
2^1
|
2^0
|
x
|
x
|
32
|
16
|
8
|
4
|
2
|
1
|
x
|
x
|
We need to use the 7th bit and the 3nd
bit to get 34, so in binary it will be:
10001000
Example #2: IP Precedence to decimal
Let’s say we got CS3, since IPPrec is using only 3 bits, CS3
in binary is 011
Now let’s put this value on the IPPrec table:
7
|
6
|
5
|
4
|
3
|
2
|
1
|
0
|
2^5
|
2^4
|
2^3
|
2^2
|
2^1
|
2^0
|
x
|
x
|
32
|
16
|
8
|
4
|
2
|
1
|
x
|
x
|
We got 16 + 8 which equals to 24 in decimal
ToS Conversion
In order to convert any DSCP/IPPrec decimal to ToS value
just multiple it in 4.
So AF41 equals to 34, 34 x 4 = 136
CS3 equals to 24, 24 x 4 = 96
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