Module 4 PHYSICAL MEDIA 1 Physical Media Types

Module 4 PHYSICAL MEDIA 1

Physical Media Types Covered 7 6 5 • • Coaxial Cable Twisted Pair Fiber Optic Cable WAN Cables 4 3 2 1 2

Coaxial Cables 10 Base 2 (Thin. LAN) - 10 Mbps baseband, 2 for 200 (actually 185 meters) • • 10 Base 5 (Thick. LAN) - Maximum data transfer speed of 10 Mbps, uses baseband transmission; 500 meters maximum cable length Baseband transmission is a type of digital data transmission in which each medium (wire) carries only one signal, or channel, at a time. In contrast, Broadband transmission enables a single wire to carry multiple signals simultaneously. 3

Coax - 10 Base 2 (Thin. LAN) • Cable Type - RG-58 A/U • Impedance - 50 W • Terminated with 50 W terminators • Connection method - BNC (as opposed to the F connector used for cable TV) • Grounding - As determined by local electrical code 4

Coax - 10 Base 2 Rules • Minimum distance between two nodes: 0. 5 m (1. 64 ft) • Maximum number of nodes / segment: 30 • Maximum segment length: 185 m (606. 7 ft) 5

Coax - 10 Base 5 (Thick LAN) • Impedance - 50 W • Terminated with 50 W terminators • Connections - ‘N’ type connections to terminate. ‘Vampire’ tap for node connections. • Grounding - Grounded at one point only. 6

Coax - 10 Base 5 Rules • Minimum Distance between two nodes: 2. 5 m • Maximum number of nodes / segment: 100 • Maximum segment length: 500 m 7

WARNING Breaking any of these rules will cause excessive error conditions! 8

Twisted Pair Cable • Cable Type: Low grade telephone cable through to cat. 5. (data cables normally cat. 3 to cat. 5) • Shielding: Shielded (STP) Unshielded (UTP) • Connectors: RJ 45, Telco, IBM Type 1 connector (genderless), 9 pin. • Use: 10 Base. T, 100 Base. TX, 100 VG ANYLAN, Token Ring 9

Twisted Pair Rules • Cable must be twisted • Maximum distance depends on quality of cable, shielding and speed of transmission • Maximum cable length for Cat 3, Cat 4 and Cat 5 is 100 m 10

Fiber Optic • Cable type determined by - diameter of core, diameter of cladding (e. g. . 62. 5 /125) • Light source - Single mode- Laser, Multimode - LED • Connectors - SC, ST, MIC • Use - FOIRL, 10 Base. FL, FDDI, 100 Base. F, Fiber Channel, SONET/SDH (for WAN) Gigabit Ethernet (future) 11

FOIRL: Fiber Optic Inter-Repeater Link is a vendor independent standard means for connecting only 2 repeater units based on the IEEE 802. 3 fiber optic specification. It is being replaced by 10 Base. FL segments can be up to 2000 meters. FDDI: Fiber Distributed Data Interface handles data rates of up to 100 Mbps; typical application: used as backbone for campus and widearea networks. FDDI networks are token-passing networks, using dualring topology over fiber-optic transmission media. Fiber Channel is a technology for serially transmitting data between computer devices at a data rate of up to 1 Gbps. SONET/SDH: Synchronous Optical Network is an optical fiber-based network standard; handles 51. 8 Mbps to 2. 48 Gbps. SDH is its international equivalent. 12

Fiber Optic Rules • Maximum distance determined by type of cable and light source used. • Need to ensure cable connection is from TX on one device to RX on the other 13

Fiber Optic Safety Considerations • Never look at the output of a fiber optic transmitter • Do not handle unterminated fiber • Do not attach connectors to fiber as special skills and tools are required. 14

WAN Cables • Cable Type: Various • Shielding: Shielded & Unshielded cable • Connectors: RS 232 (‘D’ type 25, 15, 9 pin), X. 21, V. 35 • Common pairs use: TX/RX, CTS/RTS, Control/Indicate • Uses: RS 232, X. 21, V. 35 15

WAN Cable Rules Cable Distance + Cable quality = Maximum Speed 16

Cable Connectivity 17

Simple RS 232 25 pin straight through DTE/DCE DTE DCE TX PIN 2 RX RX PIN 3 TX TO PSTN/NETWORK PC 18

Logical pinout groupings DATA CONTROL Pinouts used to transfer the data (such as TX/RX) Pinouts used to control the flow of data such as RTS/CTS (used in DTE/DCE handshaking) 19

Use of straight through and cross over cabling DCE DTE TX PIN 2 RX PIN 3 RTS PIN 4 CTS PIN 5 PIN 2 PIN 3 PIN 4 PIN 5 RX TX CTS RTS MODEM PC DTE TX PIN 2 RX PIN 3 RTS PIN 4 CTS PIN 5 PIN 2 PIN 3 PIN 4 PIN 5 NOTE: More pinouts may be required TX RX RTS CTS 20

Twisted pair cable connectivity in a LAN environment MDI-X LAN card HUB PC MDI=Media Dependent Interface MDI (for LAN) is equivalent to DTE (for WAN) & MDI-X X in MDI-X=Crossed (for LAN) is equivalent to DCE (for WAN). 21

MDI to MDI-X connection MDI 1 Twisted pair cabling MDI-X 1 2 2 3 6 HUB PC 22

Use of straight through and cross over cabling MDI-X STRAIGHT CROSS O VER THROUGH PC MDI-X CABLE HUB CROSS O VER CABLE MDI STRAIGHT MDI-X MDI THROUGH PC CABLE Hubs and Switches are MDI-X devices Hosts and Routers are MDI devices SWITCH ROUTER 23

Summary • Media Types - Coaxial Cable - Twisted Pair - Fiber - WAN Cables • Safety Considerations for Fiber • Connectivity Conventions - WAN Cables = DTE/DCE - Twisted Pair LAN = MDI/MDI-X 24