Telemetry Retrieval Inaccuracy in Programmable Switches: Analysis and Recommendations

Sketching algorithms or sketches are attractive as telemetry capabilities on programmable hardware switches since they offer rigorous accuracy guarantees and use compact data structures. However, we find that in practice, their actual implementations can have a significant (up to 94×) accuracy drop compared to theoretical expectations. We find that the delays incurred by pulling and resetting the data plane state induce accuracy degradation. We design and implement solutions to reduce the delays and show that our solutions can help eliminate almost all the inaccuracy of existing sketch workflows.