t Switched Services 3.4 Modelling Telecom Resource Systems 3.4.1 Introduction 3.4.2 Resources in Circuit Switched Networks 3.4.3 Resources in Packet Switched Networks, Introduction 3.4.4 Resources in X.25 Networks 3.4.5 Resources in ATM Networks 3.4.6 Resources in IP Networks 3.5 Logical Network Structures 3.5.1 Introduction 3.5.2 Units in Resource System Modelling, Summary 3.5.3 Units in Process Control System Modelling, Summary 3.5.4 Logical Network Structures 3.5.5 Notations for Logical Networks 3.6 Summary 4 Physical Network Modelling 4.1 Introduction Contents 4.2 Properties of Physical Networks 4.3 Physical Network Structures 4.3.1 Physical Substructures 4.3.2 Physical Network Levels and Variants 4.4 General Packet Radio Service, a Case Study 4.4.1 Introduction 4.4.2 GPRS Physical Network Level 0 4.4.3 GPRS Physical Network Level 2 4.4.4 The GPRS Standard 4.5 Implementing Network Service Interfaces 4.5.1 The Network Service Interface Transform 4.5.2 Implementing Service Access Points 4.6 Summary 5 Protocol Network Modelling Introduction 5.2 An Example: The GSM Process Control System 5.2.1 The Logical Network 5.2.2 GSM Protocol Networks 5.2.3 Summary 5.3 Discrimination 5.3.1 Introduction 5.3.2 Discrimination Levels 5.3.3 Discrimination Qualifiers 5.3.4 Connection and Association Handling 5.4 Message Handling 5.4.1 Introduction 5.4.2 Operation Handling 5.4.3 Format Handling 5.4.4 Encoding 5.4.5 Adaption Handling 5.5 The EIA553 Case Study 5.5.1 Introduction 5.5.2 The Structure of EIA553 5.5.3 The Integrator Protocol 5.5.4 The Broadcast Data-Handling Protocol 5.6 Relaying in Protocol Networks 5.6.1 Introduction 5.6.2 Relaying Chains 5.6.3 Protocol Conversion XVIII Contents 5.7 Protocol Specification Methods 5.7.1 Introduction 5.7.2 Abstract Protocol Design 5.7.3 The Universal Message Format 5.7.4 The Intelligent Message Generator 5.7.5 Private Data Types 5.8 Summary 6 Process Control System Modelling 6.1 Introduction 6.2 A Service Network Modelling Case 6.2.1 Introduction 6.2.2 Service Resource Modelling 6.2.3 O