+simgrid::xbt::signal<void(Link&)> Link::on_creation;
+simgrid::xbt::signal<void(Link&)> Link::on_destruction;
+simgrid::xbt::signal<void(Link&)> Link::on_state_change;
+simgrid::xbt::signal<void(Link&)> Link::on_bandwidth_change;
+simgrid::xbt::signal<void(kernel::resource::NetworkAction*, Host* src, Host* dst)> Link::on_communicate;
+simgrid::xbt::signal<void(kernel::resource::NetworkAction*, kernel::resource::Action::State)>
+ Link::on_communication_state_change;
+
+Link* Link::by_name(const std::string& name)