 SNMP-based). The model also shows some node concepts defined by SNMP. Managed Managed node =SNMP network agent Management Management network station (MS) nonSNMP Proxy device agent nonSNMP device SNMP-agents Proxy agents Fig. 1.34 The LSM for the SNMP management layer. MSF=management-station function; WS=work station 1.4.5 Specifying Behavior in AMLn Models The behavior of an AMLn model is described by separate specifications that are associated to different parts of the model as attributes. Almost everything that concerns the behavior can be attributed to the model of Fig. 1.18, which is repro- duced here in Fig. 1.35 with some additional information. 5 The model shows the four primary behavior describing attributes which are all specifications of interfaces: 1. Generic meta-primitives. 2. Generic send and receive operations. 3. A number of abstract protocols that describe interfaces of the LSM. 4. A message protocol specification. Note that this model represents a control layer. For a connectivity layer, only the LPM part exists. The meta-primitives are replaced by other generic primitives, indicated by another symbol for the actor- agent interface. The actors are not state-machine handlers but actors that terminate, relay, or switch data streams. 1.4 Modeling Network Systems in AMLn Described by: Described by: Abstract protocols Element specifications LSM events State machine Described by: State machine handler (SH) Message protocol handler (SH) LPM messages Meta-primitives are: r-invokeOrder(ESMidentity, LSMevent) I-invokeOrder(ESMidentity, LSMevent) Generic operations are: +Association-control operations (optional) send, receive Fig. 1.35 Primary behaviour attributes in network system models Message protocols for control and connectivity layers will look quite differ- ently: Control layers: If meta-primitives are specified, the only thing needed is a spec- ification of the translation between meta-primitives and messages, which is the same for all LSM event. The AG-SH interface may also define a number of g