* Crude globals *
*****************/
-extern std::map<std::string, SgFlow*> flow_from_sock;
-extern std::map<std::string, ns3::ApplicationContainer> sink_from_sock;
+extern std::map<std::string, SgFlow*, std::less<>> flow_from_sock;
+extern std::map<std::string, ns3::ApplicationContainer, std::less<>> sink_from_sock;
static ns3::InternetStackHelper stack;