Every connection through the NoC has an associated quality of service (QoS) requirement. The set of desired NoC connections together with their corresponding QoS requirements constitute a traffic specification. The traffic specification is used internally by the NoC compiler to compute a configuration for the NoC.
A QoS requirement includes the following two components:
- Traffic class
- Defines how traffic on the connection is prioritized in the NoC compiler and in the hardware. The traffic class is set at the NMU and is for all paths starting from that NMU.
- Read and write bandwidth requirements
- Describe how much data bandwidth the connection is expected to consume in each direction. Bandwidth requirements are associated with the egress port (NoC slave); each connection might have different read and write bandwidth requirements. Bandwidth can be expressed in units of MB/s or Gb/s.
The final performance of the NoC is subject to the accuracy of the QoS information provided. The NoC does not rate-limit traffic based on the QoS specification, so a master port that exceeds the QoS specification provided negatively impacts the performance of the other Best Effort connections it shares resources with.