xbt_assert(host_src != nullptr, "Network element %s does not seem to be ns-3-ready", src->get_cname());
xbt_assert(host_dst != nullptr, "Network element %s does not seem to be ns-3-ready", dst->get_cname());
xbt_assert(host_src != nullptr, "Network element %s does not seem to be ns-3-ready", src->get_cname());
xbt_assert(host_dst != nullptr, "Network element %s does not seem to be ns-3-ready", dst->get_cname());