RCA THOMSON SpeedTouchTM (Wireless) Business DSL Router - Manual (Page 26)

Chapter 3
Basic QoS Concepts
E-NIT-CTC-20041213-0013 v0.5
24
Assured Forwarding
(AF) PHB Group:
The Assured Forwarding (AF) PHB group allows a provider to offer different levels of
forwarding assurances for IP packets. The delivery of IP packets is provided in four
independently forwarded AF classes (AF1x through AF4x). Each AF class is allocated
a certain amount of forwarding resources (buffer space and bandwidth) in a DS node.
Within each AF class, there are three drop probabilities: Low, Medium and High drop
precedence (the higher the precedence, the higher the probability the packet will be
dropped in case of congestion).
Packets can be selected for a PHB based on required throughput, delay, jitter, loss, or
according to priority of access to network services.
The table below illustrates the recommended DSCP coding for specifying the AF
class with the drop probability. The AF value, the decimal value and the binary value
are shown for each DSCP.
Drop Precedence Class 1
AF1 Class 2
AF2 Class 3
AF3 Class 4
AF4
Low Gold
AF11
10
(001010) Gold
AF21
18
(010010) Gold
AF31
26
(011010) Gold
AF41
34
(100010)
Medium Silver
AF12
12
(001100) Silver
AF22
20
(010100) Silver
AF32
28
(011100) Silver
AF42
36
(100100)
High Bronze
AF13
14
(001110) Bronze
AF23
22
(010110) Bronze
AF33
30
(011110) Bronze
AF43
38
(100110)
For more information on the AF PHB, refer to
RFC2597
.