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Question 10: What is the decimal equivalent of the DSCP value AF21?
A. 16
B. 17
C. 18
D. 21
Correct Answer: C
Explanation:
Assured Forwarding (AF) is a means to offer different levels of forwarding assurances for IP packets.
Four AF classes are defined, where each AF class is in each DS node allocated a certain amount of
forwarding resources(buffer space and bandwidth). Within each AF class IP packets are marked with
one of three possible drop precedence values. A congested node tries to protect packets with a lower
drop precedence value from being lost by preferably discarding packets with a higher drop
precedence value. Classes 1 to 4 are referred to as AF classes. The following table illustrates the DSCP
coding for specifying the AF class with the probability. Bits DS5, DS4 and DS3 define the class; bits
DS2 and DS1 specify the drop probability; bit DS0 is always zero. he following table illustrates the
DSCP coding for specifying the AF class with the probability. Bits DS5, DS4 and DS3 define the class;
bits DS2 and DS1 specify the drop probability; bit DS0 is always zero.
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