Core Issue
If different packet marking schemes are used in different parts of a VoIP network, then it is necessary to be able relate the values to each other to ensure consistent QoS characteristics across the network.
Resolution
This table compares QoS values for IP precedence, Differentiated Services Code Point (DSCP) and Multiprotocol Label Switching (MPLS) Experimental (EXP) values along with standard values used in Cisco IOS Software for configuration. For an introduction to this topic, refer to QoS for VoIP.
Per Hop Behavior (PHB) | DSCP value | DSCP bits | IP precedence and Class of Service (COS) value (xyz000) | Comment: | MPLS EXP bits |
Default | 0 | 000000 | 0=routine | | 0 |
| 1 | 000001 |
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| 2 | 000010 |
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| 3 | 000011 |
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| 4 | 000100 |
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| 5 | 000101 |
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| 6 | 000110 |
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| 7 | 000111 |
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CS1 | 8 | 001000 | 1=priority | | 1 |
| 9 | 001001 |
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AF11 | 10 | 001010 |
| - Assured forwarding class 1 (001)
- Drop priority 010 (1)
- Dropped last in AF1 class
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| 11 | 001011 |
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AF12 | 12 | 001100 |
| - Assured forwarding class 1 (001)
- Drop priority 100 (2)
- Dropped 2nd in AF1 class
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| 13 | 001101 |
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AF13 | 14 | 001110 |
| - Assured forwarding class 1 (001)
- Drop priority 110 (3)
- Dropped first in AF1 class
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| 15 | 001111 |
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CS2 | 16 | 010000 | 2=immediate |
| 2 |
| 17 | 010001 |
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AF21 | 18 | 010010 |
| - Assured forwarding class 2 (010)
- Drop priority 010 (1)
- Dropped last in AF2 class
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| 19 | 010011 |
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AF22 | 20 | 010100 |
| - Assured forwarding class 2 (010)
- Drop priority 100 (2)
- Dropped 2nd in AF2 class
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| 21 | 010101 |
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AF23 | 22 | 010110 |
| - Assured forwarding class 2 (010)
- Drop priority 110 (3)
- Dropped first in AF2 class
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| 23 | 010111 |
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CS3 | 24 | 011000 | 3=Flash |
| 3 |
| 25 | 011001 |
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AF31 | 26 | 011010 |
| - Assured forwarding class 3 (011)
- Drop priority 1 (010)
- Dropped last in AF3 class
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| 27 | 011011 |
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AF32 | 28 | 011100 |
| - Assured forwarding class 3 (011)
- Drop priority 2 (100)
- Dropped 2nd in AF3 class
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| 29 | 011101 |
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AF33 | 30 | 011110 |
| - Assured forwarding class 3 (011)
- Drop priority 3 (110)
- Dropped first in AF3 class
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| 31 | 011111 |
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CS4 | 32 | 100000 | 4=FlashOver |
| 4 |
| 33 | 100001 |
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AF41 | 34 | 100010 |
| - Assured forwarding class 4 (100)
- Drop priority 1 (010)
- Dropped last in AF4 class
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| 35 | 100011 |
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AF42 | 36 | 100100 |
| - Assured forwarding class 4 (100)
- Drop priority 2 (100)
- Dropped 2nd in AF4 class
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| 37 | 100101 |
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AF43 | 38 | 100110 |
| - Assured forwarding class 4 (100)
- Drop priority 3 (110)
- Dropped first in AF4 class
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| 39 | 100111 |
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CS5 | 40 | 101000 | 5=critical |
| 5 |
| 41 | 101001 |
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| 42 | 101010 |
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| 43 | 101011 |
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| 44 | 101100 |
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| 45 | 101101 |
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EF | 46 | 101110 |
| Recommended Expedited Forwarding (EF) value (used for voice traffic) | |
| 47 | 101111 |
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CS6 | 48 | 110000 | 6=internet |
| 6 |
| 49 | 110001 |
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| 50 | 110010 |
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| 51 | 110011 |
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| 52 | 110100 |
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| 53 | 110101 |
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| 54 | 110110 |
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| 55 | 110111 |
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CS7 | 56 | 111000 | 7=network |
| 7 |
| 57 | 111001 |
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| 58 | 111010 |
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| 59 | 111011 |
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| 60 | 111100 |
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| 61 | 111101 |
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| 62 | 111110 |
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| 63 | 111111 |
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