Cabletron Systems 9032578-05 manual Tos-precedence-rewrite = 5 tos-rewrite =

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:

ssr(config)# qos set ip tosp6to7 low any any any any 222 any any 224 7

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.

Incoming Packet:		0	1	0	0	0		1	1	1
	ToS Precedence = 2						ToS = 7

<tos> = 71

Mask (look at all bits):

Rewritten ToS byte for 10.10.10.0/24 packet:

1 1 1 1 1 1 1 1

1 0 1 1 1 1 1 0

<tos-mask> = 255

<tos-precedence-rewrite> = 5 <tos-rewrite> = 30

ToS Precedence = 5 ToS = 30

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 tos30to7 low 10.10.10.0/24 any any any 71 any any 255 5 30

SmartSwitch Router User Reference Manual 301