  The growing research and industry interest in the Internet of Things and the
edge computing paradigm has increased the need for cost-efficient virtual
testbeds for large-scale distributed applications. Researchers, students, and
practitioners need to test and evaluate the interplay of hundreds or thousands
of real software components and services connected with a realistic edge
network without access to physical infrastructure.
  While advances in virtualization technologies have enabled parts of this,
network emulation as a crucial part in the development of edge testbeds is
lagging behind: As we show in this paper, NetEm, the current state-of-the-art
network emulation tooling included in the Linux kernel, imposes prohibitive
scalability limits. We quantify these limits, investigate possible causes, and
present a way forward for network emulation in large-scale virtual edge
testbeds based on eBPFs.
