ervices that are used especially for the management layer are those we have discussed: OSI layer 4 if mpCP protocols rely on CMIS/CMIP; IIOP if they relay on CORBA and run on TCP; and TCP/UDP if the mpCP pro- tocol is SNMP. A corresponding intralayer structure for the management plane is shown in Fig. 5.22. Here we choose to show two nodes: the management system is one node; the other is an imaginary traffic-system node that takes part in all traffic layers and handles service users as well. We also indicated the separation of MOs in AFs according to the traffic system layer structure. 5.6 Summary Traffic system users Management layer AMF protocol mrCP R T protocol protocol Operators Other msCP protocols nodes Traffic system node Management system Traffic plane Management plane Fig. 5.22 The intralayer structure, seen over two nodes: the management system and a traffic sys- tem node that takes part in all traffic layers Note that this model is a reference model only. When applied to actual traffic systems, all traffic system nodes will not handle all layers (some may only handle one or two low level layers). Furthermore, only some layers may be managed by AMFs, and only some AMFs may deliver information to AFs. Also, as shown in Fig. 5.22, an AMF may use the connectivity services of one layer (here L3) but manage resources in another (here in L4). An example of that is the routing proto- col BGP (see Appendix A) in the Internet that runs on the TCP layer and manages routing tables in the IP layer. 6 Applying AMLn Introduction Basically, AMLn can be used in two ways: for specifying network systems or for analysing network systems that are not described in AMLn (which are all systems that exist today). Used as a specification tool, the resulting AMLn model is an exact model of the system to be implemented. Once implementors get used to AMLn, such a model is easily understood (compared to understanding thousands of standard pages). The model is also easily accessible for every individual in the development organizat