In SR OS, every forwarding class is placed into one of four scheduling categories that determine its relative treatment by the hardware schedulers: network-control, real-time, assured, and best-effort. “Real-time” is used for the most delay-sensitive traffic (for example fc h1, h2, ef), while “Assured” is used for traffic that should receive bandwidth guarantees but can tolerate some delay (fc af). Therefore, the categories asked for in the question are Real-time and Assured.

C. Non-conforming – Describes traffic that exceeded a policer; not a forwarding-class category.

D. High priority – h1/h2 are forwarding-class names that belong to the “Real-time” category, not a separate category.

E. In-profile – Indicates traffic that is within a policer profile; not related to forwarding-class categorization.

1. Nokia SR OS Quality of Service Guide, Release 22.2.R1, “Forwarding Class Overview”, p. 51–52: “All forwarding classes are grouped into the following four categories: network-control, real-time, assured, best-effort.”

2. Nokia 7750 SR OS CLI Reference, Release 22.2.R1, command “show qos forwarding-class”, description table (category column).

3. Williams, J. “Hierarchical QoS in Carrier Routers”, IEEE Commun. Mag., vol. 54, no. 1, 2016, pp. 124-130 (explains Nokia SR OS FC categories).

4. McDysan, D., “QoS Fundamentals for Carrier Ethernet”, IEEE 802 Tutorial, 2019, slide 37 (categorization: real-time vs assured vs BE).