Siemens HIPATH 8000 HIPATH 8000 Administrator's Manual page 209

Assured forwarding is used for signaling messages by default (AF31) and
less stringent than EF in a multiple dropping system.
The AF values are containing two digits X and Y (AFXY), where X is describ-
ing the priority class and Y the drop level.
Four classes X are reserved for AFXY: AF1Y (High Priority), AF2Y, AF3Y and
AF4Y (Low Priority).
Three drop levels Y are reserved for AFXY: AFX1 (low drop level), AFX2 and
AFX3 (High drop level). In the case of low drop level, packets are buffered
over an extended period in the case of high drop level, packets are prompt-
ly rejected if they cannot be forwarded.
Version
Length
Layer 3 / IP Precedence (old recommendation, replaced by Diffserv)
IP Precedence is classifying traffic flows into 8 different precedence levels.
These 3 Bits are the same as the priority Bits from Diffserv. Value 5 (BIN:
101) is used for voice by default. And value 3 (BIN: 011) is used for signaling.
These values are already configured by configuring the DiffServ values.
If a routing partner can only work with one of the two standards (DiffServ
or IP precedence, for example an older router that only works with IP pre-
cedence), than the router can translate the ToS field accordingly. This can
be set for each PSTN peer or LAN interface.
Decimal
Diffserv-
Codepoint Binary 6-Bit
EF 101110 46
AF 43 100110 38
AF 42 100100 36
AF 41 100010 34
AF 33 011110 30
AF 32 011100 28
AF 31 011010 26
AF 23 010110 22
AF 22 010100 20
AF 21 010010 18
AF 13 001110 16
AF 12 001100 12
AF 11 001010 10
ToS
1 Byte Len ID Offset TTL Proto
IP header
DiffServ
Hex (8Bit)
8-Bit ToS Field Priority
184 B8 very high
152 98
144 90 high
136 88
120 78
112 70 medium
104 68
88 58
80 50 low
72 48
64 38
48 30 very low
40 28
page 58 and page 46
Standard IPV4: Three MSB Called IP Precedence
(DiffServ Uses Six MSB Bits)
QoS
Drop level
high med low versus
x <->
x <->
x <->
x <->
x <->
x <->
x <->
x <->
x <->
x <->
x <->
x <->
x <->
page 117
Alphabetical Reference
FCS IP-SA IP-DA Data
Ethernet-
Header
IEEE802.1p
IP Precedence Binary Decimal
101 101
100 100
100 100
100 100
011 011
011 011
011 011
010 010
010 010
010 010
001 001
001 001
001 001
5
4
4
4
3
3
3
2
2
2
1
1
1
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