QoS — Quality of Service
Definition
Quality of service (QoS) is a set of switch functions that give some traffic priority over the rest when a port is congested. For Dante networks, Audinate specifies DiffServ (DSCP) markings: time-critical PTP clock events are marked CS7 (56) and receive the highest priority, audio is marked EF (Expedited Forwarding, 46) and receives medium priority, and the value CS1 (8) is reserved with low priority. A switch applies these priorities only when it is configured to trust DSCP markings and to serve its queues with strict priority. The codepoint 46 for Expedited Forwarding is defined in RFC 3246.
In the field
A managed switch with QoS disabled queues Dante packets alongside bulk transfers, so congestion adds a delay that can exceed the configured latency. Audinate requires QoS on 100 Mbit/s networks and on mixed 100 Mbit/s and gigabit networks, and recommends it on every Dante network. After configuration, the queue mapping and the DSCP trust setting are usually checked from the switch management interface or command line.
Related lessons
Sources
- RFC 3246, An Expedited Forwarding PHB : codepoint recommandé 101110 (46) pour l'EF ; remplace la RFC 2598 · rfc-editor.org
- Audinate/Yamaha, Dante Network Design Guide, QoS : sur un réseau Dante dédié, DSCP 56 (CS7), 46 (EF) et 8 (CS1) affectés aux files de priorité 4, 3 et 2 du switch, le reste en 1 · usa.yamaha.com
- Audinate FAQ, How does Dante use DSCP / Diffserv priority values when configuring QoS? CS7 (56) événements PTP critiques en priorité haute, EF (46) audio et PTP v2 en priorité moyenne, CS1 (8) réservé en priorité basse ; confiance DSCP sur le switch · getdante.com
- Audinate FAQ, How does Dante manage QoS? Switch Diffserv (DSCP) à priorité stricte et 4 files · getdante.com
- Audinate FAQ, Networks and Switches : QoS obligatoire en 100 Mbit/s et en réseau mixte, recommandée partout · support.getdante.com
- RFC 2474 : définition du champ DS (DSCP) de l'en-tête IP · rfc-editor.org