6. Operational Considerations

The assigned NQB DSCP is 45 decimal, with Default remaining DSCP 0. Nodes that do not support the NQB PHB are RECOMMENDED to treat NQB-marked traffic the same as Default traffic and SHOULD NOT re-mark it, so downstream hops that do support NQB can still identify it.

Operators should be careful when aggregating other DSCPs into NQB. Aggregating traffic that does not meet NQB sender behavior can damage the shallow-buffered service and weaken incentives for correct marking.

For cross-domain use, networks that agree to support NQB SHOULD use DSCP 45 unless a Traffic Conditioning Agreement records another DSCP. Where traffic enters a non-DS-capable downstream domain and could otherwise gain unintended treatment, RFC 9956 recommends safeguards. One option is to re-mark NQB traffic to DSCP 0 by default, and equipment for such environments SHOULD support changing or disabling that behavior. Another is to use traffic protection; if so, the function MUST re-mark offending traffic to DSCP 0 or another Class Selector DSCP, or discard it, to protect the downstream domain.

If policing or shaping is applied to an NQB aggregate toward a non-DS-capable domain, the policer or shaper rate SHOULD be set to the greater of 5% of the interconnection rate or 5% of the typical interconnection rate. Traffic policing SHOULD allow about 100 ms of burst tolerance. Traffic shaping SHOULD allow about 10 ms of burst tolerance and should not buffer more than 50 ms.

For lower-rate links, operators SHOULD consider traffic protection or MAY disable NQB where compliant NQB rates are too high relative to the link. If the link rate is below 10% of typical path rates, disabling the NQB PHB and carrying NQB DSCP traffic with the Default PHB, without re-marking it to DSCP 0, is RECOMMENDED.