Lecture 3 - Wired Transmission Media.pdf

LECTURE 3 WIRED TRANSMISSION MEDIA OVERVIEW Transmission Media Wired...

LECTURE 3 WIRED TRANSMISSION MEDIA OVERVIEW Transmission Media Wired Wireless Copper Fibre Bluetooth WiFi Microwave Coaxial Twisted Pair Multi Mode Single Mode Thinnet Thicknet Shielded Unshielded BASIC DEFINITIONS DIGITAL ANALOG Discrete states Continuous states BASIC DEFINITIONS (CONT’D) Data transfer rates are measured in bits per second (bps) 1 Kbps = 1,000 bps 1 Mbps = 1,000,000 bps (1,000 Kbps) 1 Gbps = 1,000,000,000 bps (1,000 Mbps) Bandwidth: maximum data transfer rate possible Throughput: actual data transfer rate; less than or equal to Bandwidth BASIC DEFINITIONS (CONT’D) BROADBAND BASEBAND Multiple streams / lanes Single stream / lane BASIC DEFINITIONS (CONT’D) Electromagnetic Interference (EMI): caused by the presence of electrical and/or magnetic signals Radio Frequency Interference (RFI): caused by the presence of radio signals Attenuation: signal loss caused by degradation of signal over distance COPPER Soft, malleable, and ductile metal Very high thermal and electrical conductivity Conductor of heat and electricity Data transmitted as analog COAXIAL Thick copper wire surrounded by three layers: plastic jacket braided shield plastic (PVC or Teflon) Layers reduce EMI and RFI COAXIAL CABLES THIN ETHERNET (“THINNET”) THICK ETHERNET (“THICKNET”) 10 Base 2 10 Base 5 10 Mbps 10 Mbps Baseband Baseband ~200m (185 m) 500m 5 mm or 2/10” diameter, Radio Grade 58 ½” diameter, Radio Grade 8 (RG-8) (RG-58) 1,024 nodes per segment 30 nodes per segment COAXIAL CONNECTORS F-TYPE CONNECTOR (75 OHM) BNC CONNECTOR (50 OHM) TWISTED PAIR Individually insulated copper wires twisted in pairs Twists reduce crosstalk as well as EMI and RFI Limited to 100 m TWISTED PAIR CABLES SHIELDED (STP) UNSHIELDED (UTP) TWISTED PAIR CONNECTORS TELEPHONE JACK E.G. RJ-11 RJ-45 PREVIOUS TWISTED PAIR CATEGORIES Cat 1: 2 pairs (4 wires); voice grade (POTS) Cat 2: 4 pairs (8 wires); 4 Mbps (Early Token Ring) Cat 3: 4 pairs (8 wires); 10 Mbps (10 Base T) Cat 4: 4 pairs (8 wires); 16 Mbps (Newer Token Ring) CURRENT TWISTED PAIR CATEGORIES Cat 5: 100 MHz / 2 pairs; 100 Mbps (100 Base TX) Cat 5e: 100MHz / 4 pairs; 1,000 Mbps (1000 Base T) Cat 6: 250 MHz / 2 pairs; 1,000 Mbps (1000 Base TX) Cat 6a: 500 MHz / 4 pairs; 10,000 Mbps (10G Base T) COLLISION DOMAINS All nodes on a physical segment that hear all communication Hubs are 1 Collision Domain BROADCAST DOMAINS All nodes on a physical segment that hear all broadcasts Switches are 1 Broadcast Domain CARRIER SENSE MULTIPLE ACCESS WITH COLLISION DETECT (CSMA/CD) Node listens to wire (Carrier Sense) Node transmits data If another node transmits data, there is a collision (Collision Detect) Nodes send a jam signal and wait using the back-off algorithm FIBRE Flexible, transparent strand of glass (silica) or plastic slightly thicker than a human hair Transmits light between the two ends Allow longer distances and higher bandwidths than copper cables Data transmitted as digital FIBRE-OPTIC Glass or plastic core (distance vs cost) surrounded by a glass or plastic cladding, plastic, armour coating (usually Kevlar) and PVC or Teflon Immune to EMI and RFI Expensive and difficult to implement and support FIBRE-OPTIC CABLES MULTIMODE FIBRE (MMF) SINGLE-MODE FIBRE (SMF) FIBRE-OPTIC CONNECTORS Angled Physical Contact (APC) vs Ultra Physical Contact (UPC) Straight Tip (ST) vs Subscriber or Square Connector (SC) Small Form Factor Connectors: Mechanical Transfer Registered Jack (MTRJ) vs Local Connector (LC) MEDIA CONVERTERS TO BE CONTINUED… THE TCP/IP MODEL