ADTRAN AOS Version R10.1.0 Command Reference Manual page 3308

Command Reference Guide
According to RFC 2474, the DS field contains the following bits:
* The previously unused bits in the DS field are now used for congestion control and are not discussed in this document.
Equipment following the DiffServ model (DS-compliant nodes) must use the entire six-bit DSCP value to
determine the appropriate PHB. The PHBs are defined as the following:
• Default PHB
• Class selector PHB
• Assured forwarding PHB (RFC 2597)
• Expedited forwarding PHB (RFC 2598)
Default PHB
All DS-compliant nodes must provide a default PHB to offer best-effort forwarding service. For default
PHBs, the DSCP value is 0. Any packet that does not contain a standardized DSCP should be mapped to
the Default PHB and handled accordingly.
Class Selector PHB
In the class selector PHB, the first three bits in the DSCP value are used for backwards compatibility to
systems implementing IP precedence. In this scenario, all but the first three bits of the DS field are set to 0.
This compatibility requires DS-compliant nodes to provide the same data services as are provided by
nodes implementing IP precedence. The following table is a comparison of IP precedence values to their
corresponding DSCP values.
60000CRG0-35E
0 1 2 3
Differentiated Services Code Point
IP Precedence
Value (bits)
0 (000)
1 (001)
2 (010)
3 (011)
4 (100)
5 (101)
6 (110)
7 (111)
Copyright © 2012 ADTRAN, Inc.
4 5 6 7
Unused*
DSCP Value (bits)
0 (000000)
8 (001000)
16 (010000)
24 (011000)
32 (100000)
40 (101000)
48 (110000)
56 (111000)
Route Map Command Set
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