ShadowFS: Speeding-up Data Plane Monitoring and Telemetry using P4

Programmable Data Planes (PDPs) provide software abstractions for network operators to dynamically modify the data plane behavior. This behavior can be described in specification languages, such as P4, and deployed into programmable switches our routers. The degree of innovation enabled by PDPs allowed network operators to create new protocols and applications. Despite the high degree of innovation brought to data plane packet processing, this programmability may have a negative effect on the forwarding delay and update times of flow tables. Previous works have attempted to overcome these limitations, e.g., through caching mechanisms, however they do not provide efficient replacement primitives and incur large overhead for monitored traffic. In this paper we present the design and evaluation of ShadowFS, a system to speed-up monitoring and telemetry on the data plane. ShadowFS manages the replacement of table entries using smaller caches without requiring the programmer to specify the behavior of these tables or how to steer traffic through them. Different from previous work, ShadowFS builds a new data plane program that monitors flows and replaces rules between tables automatically. Evaluation results demonstrate that ShadowFS can increase the throughput of frequently monitored flows.