Chapter 13: Quality of Service 225
Section 13-1
Table 13-1 Mapping of IP Precedence and DSCP Fields (Continued)
IP Precedence (3 Bits) DSCP (6 Bits)
Name Value Bits
Per-Hop
Behavior
Class
Selector
Drop
Precedence
Codepoint
Name
DSCP Bits
(Decimal)
Immediate 2 010 AF 2 1: Low AF21 010 010 (18)
2: Medium AF22 010 100 (20)
3: High AF23 010 110 (22)
Flash 3 011 AF 3 1: Low AF31 011 010 (26)
2: Medium AF32 011 100 (28)
3: High AF33 011 110 (30)
Flash
Override
4 100 AF 4 1: Low AF41 100 010 (34)
2: Medium AF42 100 100 (36)
3: High AF43 100 110 (38)
Critical 5 101 EF N/A N/A EF
101 110 (46)
1
Internetwork
Control
6 110 N/A N/A N/A N/A
N/A
2
Network
Control
7 111 N/A N/A N/A N/A
N/A
2
1
IP precedence value 5 (DSCP EF) corresponds to the range of DSCP bits 101000 through 101111, or 40 to 47. However,
only the value 101110 or 46 is commonly used and is given the EF designation.
2
IP precedence values 6 and 7 consume the DSCP ranges 48 to 55 and 56 to 63, respectively. However, these values are
normally used by network control traffic and are not shown in the table for simplicity.
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