Network Router User Manual

SmartSwitch Router User Reference Manual 301
Chapter 21: QoS Configuration Guide
are rewritten to the <tos-precedence-rewrite> value and the lower five bits are rewritten to
the <tos-rewrite> value.
For example, the following command will rewrite the ToS Precedence field to 7 if the ToS
Precedence field of the incoming packet is 6:
In the above example, the <tos> value of 222 (binary value 1101 1110) and the <tos-mask>
value of 224 (binary value 1110 0000) are ANDed together to specify the ToS Precedence
field value of 6 (binary value 110). Changing the value in the <tos-mask> parameter
determines the bit in the ToS octet field that will be examined.
The following example will rewrite the ToS Precedence and the ToS fields to 5 and 30 if the
incoming packet is from the 10.10.10.0/24 network with the ToS Precedence field set to 2
and the ToS field set to 7. (In this example, the MBZ bit is included in the ToS field.) The
figure below shows how the parameter values are derived.
The <tos-mask> value determines the ToS bit to be examined, which is all eight bits in this
example. The following command configures the ToS rewrite for the example:
ssr(config)# qos set ip tosp6to7 low any any any any 222 any any 224 7
1
0000
111
11111
11 1
1
0
11111
0
Incoming Packet:
<tos> = 71
ToS Precedence = 2 ToS = 7
Mask (look at
<tos-mask> = 255
ToS Precedence = 5 ToS = 30
<tos-precedence-rewrite> = 5
<tos-rewrite> = 30
Rewritten ToS byte
for 10.10.10.0/24
packet:
all bits):
ssr(config)# qos set ip tos30to7 low 10.10.10.0/24 any any any 71 any
any 255 5 30