Analyzing violations of forwarding properties is a classic networking problem. However, existing work is either tailored to the steady state -- and not to transient states during iBGP convergence -- or does analyze transient violations but with inaccurate proxies, like control-plane convergence, or without precise control over the different impact factors. We address this gap with a measurement framework that controllably and accurately measures transient violation times in realistic network deployments. The framework relies on a programmable switch to flexibly emulate diverse topologies and gain traffic visibility at all links -- enabling accurately inferring violation times of any forwarding property. Using the framework, we analyze 50 network scenarios on a topology with 12 real routers, and show how factors like the network configuration and BGP event affect transient violation times. Further, we shed light on less-known aspects of BGP convergence, including that transient violations can start before the trigger event, or that keeping a backup route advertised at all times can increase violation times.
@article{arxiv.2503.15249,
title = {The Effects of iBGP Convergence},
author = {Roland Schmid and Tibor Schneider and Georgia Fragkouli and Laurent Vanbever},
journal= {arXiv preprint arXiv:2503.15249},
year = {2025}
}