On which level is the virtual machine system traffic reservation defined in Network I/O Control version 3?

The uplink level represents physical NIC capacity settings and is not the layer where system traffic reservations for VM traffic are defined in NIOC v3.

In NIOC v3, introduced in vSphere 6.0, system traffic reservations for VM traffic are defined at the distributed switch level, which allows centralized bandwidth allocation and enforcement across all hosts connected to that vDS. This design enables consistent traffic management without requiring per-host configuration.

Distributed portgroups define network policies such as security and VLAN settings for groups of ports, but are not where NIOC v3 system traffic reservations are configured.

Individual host-level configuration is the model used by NIOC v2; NIOC v3 moves this responsibility up to the distributed switch level for centralized control.