Where is Metadata Stored?

Stateful Flow Management

Napatech SmartNIC
User Guide

There are certain principles that apply when considering where to store flow metadata.

Metadata storage principles

  • Data is always stored as close as possible to where it is needed
  • Flow records in HW contain only the information needed by the HW Fast Path
  • Flow records in SW contain any information needed by the application to ensure:
    • Lowest PCI bandwidth, because there is less metadata per packet
    • Highest scalability, because memory is less limited in the host than in HW
    • Highest flexibility, because the application can update flow records without a hardware update
    • Highest performance, because the CPUs are being used for tasks they do best
  • Hardware can provide a flow ID/PTR for every packet and flow record that is delivered to SW, ensuring the best acceleration for an application.