Packet Precedences - HP FlexNetwork NJ5000 User Manual

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downstream network can either use the classification results from its upstream network or classify
the packets again according to its own criteria.
To provide differentiated services, traffic classes must be associated with certain traffic control
actions or resource allocation actions. What traffic control actions to use depends on the current
phase and the resources of the network. For example, CAR polices packets when they enter the
network. GTS is performed on packets when they flow out of the node. Queue scheduling is
performed when congestion happens. Congestion avoidance measures are taken when the
congestion deteriorates.

Packet precedences

IP precedence and DSCP values
Figure 438 ToS field and DS field
Bits:
DS-Field
(for IPv4,ToS
octet,and for
IPv6,Traffic
Class octet )
As shown in
ToS field of the IP header is redefined as the differentiated services (DS) field, where a differentiated
services code point (DSCP) value is represented by the first 6 bits (0 to 5) and is in the range of 0 to
63. The remaining 2 bits (6 and 7) are reserved.
Table 141 Description on IP Precedence
IP Precedence (decimal)
0
1
2
3
4
5
6
7
Table 142 Description on DSCP values
DSCP value (decimal)
46
10
12
14
0
1
2
3
4
5
6
7
DSCP
CU
Class Selector
Currently
codepoints
Unused
Differentiated Services
Codepoint (DSCP)
RFC 2474
Figure
438, the ToS field of the IP header contains 8 bits. According to RFC 2474, the
IP Precedence (binary)
000
001
010
011
100
101
110
111
DSCP value (binary)
101110
001010
001100
001110
401
Description
Routine
priority
immediate
flash
flash-override
critical
internet
network
Description
ef
af11
af12
af13

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