CS312 - Data Communications & Computer Networks MACS, USP. Hugh Anderson February 10, 2000 Preface In the study of any structured discipline, it is necessary to: • appreciate the background to the discipline, • know the terminology, and practice • understand elements of the framework (hence the word structured). Data communication is no different, so we begin by looking to the past, and studying the ’history’ of data communication. Data communication is just one kind of communication, so we continue with general communication theory (Fourier, Nyquist and Shannon). We also look at the equipment in current use before considering elements of data communications within a framework, known as the OSI reference model. i Contents 1 Background 1 1.1 Prehistory . 1 1.2 Recent history . 4 1.3 Communication theory . 7 1.3.1 Analog & digital . 7 1.3.2 Fourier analysis . 8 1.3.3 Shannon and Nyquist . 10 1.3.4 Baseband and modulated signals . 11 1.4 Media . 11 1.5 Computer hardware . 14 1.5.1 1.5.2 Parallel port . 15 1.5.3 Serial port . 16 1.5.4 Keyboard . 17 1.5.5 SCSI port . 17 1.5.6 Macintosh LLAP . 18 1.5.7 Monitor cable . 18 1.5.8 1.6 Backplane & IO busses . 14 I 2 C . 19 Standards organizations . 20 2 OSIRM 22 2.1 The layers . 23 2.2 Example . 24 2.3 Sample protocols . 26 ii CONTENTS iii 3 Layer 1 - Physical 27 3.1 Sample ’layer 1’ standards . 27 3.1.1 Token ring cabling . 28 3.1.2 Localtalk cabling . 28 3.1.3 UTP cabling . 29 3.1.4 Fibre optic cabling . 29 3.1.5 Thin and thick ethernet cabling . 30 3.2 Addressing . 31 3.3 Spectrum . 31 3.4 Signals and cable characteristics . 32 3.5 Noise . 35 3.6 Electrical safety . 36 3.7 Synchronization . 37 3.8 Digital encoding . 38 3.9 Modems . 38 3.10 Diagnostic tools . 40 4 Layer 2 - Datalink 4.1 42 Sample standards . 44 4.1.1 HDLC . 44 4.1.2 Ethernet . 44 4.1.3 PPP . 44 4.1.4 LLAP . 45 4.2 Addressing . 45 4.3 Modes . 46 4.4 Framing . 46 4.4.1 Bit stuf?ng . 47 4.4.2 Byte stuf?ng . 47 4.5 Error detection . 47 4.6 Error correction . 48 4.6.1 Hamming . 48 CONTENTS 4.6.2 iv Feed forward error correction . 49 4.7 Datalink protocols . 49 4.8 Sliding windows . 51 4.9 MAC sublayer . 52 4.9.1 CSMA/CD . 53 4.10 Diagnostic tools . 54 5 Layer 3 - Network 56 5.1 Sample standards . 57 5.2 Addressing . 59 5.2.1 IP Addressing . 59 5.2.2 IP network masks . 60 5.2.3 IPX addressing . 60 5.2.4 Appletalk Addressing . 61 5.3 IP packet structure . 61 5.4 Allocation of IP Addresses . 63 5.5 Translating addresses . 63 5.6 Routing . 64 5.6.1 5.7 Routing Protocols . 64 Con?guration . 67 5.7.1 5.7.2 5.8 Addressing . 67 Routing . 68 Diagnostic tools . 69 6 Layers 4,5 - Transport, Session 70 6.1 Sample transport standards . 71 6.2 Session standards and APIs . 72 6.3 Addressing . 73 6.4 Transport layer . 74 6.4.1 6.4.2 6.5 TCP . 75 UDP . 76 Session layer