Abstract

Abstract: While software network functions (NFs) promise great flexibility and easy deployment of network services, they face the challenge of unpredictable performance. We propose Bolt, a technique and tool for predicting the performance of the entire software stack of an NF comprising the core NF logic, DPDK packet processing framework, and the NIC driver. Bolt takes as input the NF implementation and generates a performance contract that provides, for any arbitrary packet scenario, a precise characterization of the NF’s performance. Under the covers, Bolt leverages a state-based demarcation of NFs and combines a pre-analysis of stateful data structures with automated symbolic execution of the stateless NF code. Performance contracts allow scrutiny of NF performance with a fine level of granularity, enabling network developers and operators to understand the performance of the NF in the face of any workload, whether typical, exceptional, or adversarial. We evaluate Bolt on four realistic NFs—-a NAT , a Maglev-like load balancer, an LPM Router, and a MAC bridge—-and show that Bolt’s performance contracts predict the dynamic instruction count and memory accesses of the NF to within a maximum of 7% of real executions, for all NFs and traffic classes analyzed.