1. Introduction

RFC 9956 defines the Non-Queue-Building Per-Hop Behavior (NQB PHB). It isolates low-data-rate, application-limited microflows, such as interactive voice, game synchronization, DNS lookups, and some real-time IoT analytics, from Queue-Building (QB) traffic that seeks capacity and creates queue delay.

The PHB offers shallow-buffered best-effort treatment beside the Default deep-buffered best-effort service. A network node implementing NQB does not guarantee a data rate or end-to-end delay; the low delay comes from the sender's own non-queue-building behavior and from separating that behavior from bursty QB traffic.

The document recommends DSCP value 45 (decimal) for NQB traffic and updates RFC 8325 guidance for mapping Diffserv markings to IEEE 802.11/Wi-Fi treatment.