3.7.3 DSCP rewriting
DSCP updating is functionality that is used to update the DSCP, which is the six highest-order bits of the TOS field in the IPv4 header or the traffic class field in the IPv6 header. The following figures show the formats of the TOS and traffic class fields.
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As shown, the six highest-order bits of the TOS field or traffic class field of the detected frame are updated.
You can also use DSCP updating to update the DSCP of a frame that exceeds the minimum monitoring bandwidth on instruction from the bandwidth monitoring functionality. For example, you can set the DSCP value to 0 for frames that exceed the minimum monitoring bandwidth.
For handling of non-compliant frames when DSCP updating and minimum bandwidth monitoring are specified at the same time, the penalty operation specified for non-compliance has priority.
You cannot update the DSCP for the following frames:
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IPv4 and IPv6 packets exceeding the MTU
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Frames whose TTL is set to 1
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Frames whose hop limit is set to 1
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Frames with an IP option
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Frames with an IPv6 extension header
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IPv4 or IPv6 packets with an unknown receiver address