CIM 2465 Network Connectivity 1

Network Connectivity(Topic 2)

Textbook:

Networking Basics, CCNA 1 Companion Guide, Cisco Press

Cisco Networking Academy Program, CCNA 1 and 2, Companion Guide, Cisco Press, Latest Edition

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Analog Signal Vs Digital Signal

• Analog data is continuous data• The world we live in is mainly an analog

world. E.g. light, video, voice • Digital data is discrete, values are distinct

from one another.• Digital computers process data in digital

form (0 or 1)• A/D D/A conversion (e.g. modem)

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Analog Signal Vs Digital Signal

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Properties of an Analog Signal

• Amplitude

• Frequency

• Phase

• Modulation and Demondulation

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Factors AffectingTransmission of Signals

• Noise– Refers to any interference on the physical medium that makes it

difficult for the receiver to detect the data signal– Crosstalk

• Noise created on one wire as a result of current flowing over a nearby wire

• Attenuation– Attenuation in an electrical signal is a decrease in voltage as the

signal crosses the wire– Can be caused by

• Resistance of wires• Energy loss• Frequency of signal

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Digital Transmission

• Digital Transmission is a general term that refers to how computing devices transmit the binary bits from one to another

• Can be done by (Modulation)– Varying (modulating) an electrical signal as it

passes over a copper wire– Varying the power of light as sent over an

optical fiber– Varying the radio waves sent through space,

wireless communications

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Transmission Media

• Major types– Copper Wires

• Coaxial Cable, Shielded Twisted Pair (STP), Unshielded Twisted Pair (UTP)

– Optical– Wireless

• Considerations– Transmission speed– Digital or Analog transmission– Transmission distance

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Coaxial Cable

• Composed of a single copper wire, surrounded by an insulating shell, then a second conductor shield, and a plastic outer shell– Types:

• Thick Coaxial (10Base5)• Thin Coaxial (10Base2)

• Today’s modern LANs no longer use 10BASE5 and 10BASE2

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Coaxial Cable

• Advantages– Longer transmission distance than STP and UTP, few

er repeaters needed– Less expensive than fiber-optic, more expensive than

STP and UTP– High bandwidth medium that can carry thousands of

signals, support broadband transmission of cable TV, a single cable is divided into many channels for transmission. Commonly used to deliver cable-television signals and high-speed Internet access

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Coaxial Cable

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Twisted Pair Wire

• Most commonly used data transmission medium

• Its core consists of pairs of copper wires twisted together to create magnetic field and thus reduce interference

• 2 types: – Shielded Twisted Pair (STP)– Unshielded Twisted Pair (UTP)

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Shielded Twisted Pair (STP)

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Shielded Twisted Pair (STP)

• Shielding provides a cleaner electrical current by reducing attenuation and noise, thus longer cabling lengths

• More expensive, heavier, and difficult to bend when installing them (compare with UTP)

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Unshielded Twisted Pair (UTP)

• Grouped into categories based on quality

• Generally used in LAN

• Cat 5 cable• RJ45

connector

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Unshielded Twisted Pair (UTP)

• Adv– Does not require grounding like STP, easier to add co

nnectors– Thinner, more flexible to install– Same data speeds as other copper media

• Disadv– More susceptible to electrical noise and interference– Shorter cabling distance (100m when used for Ethern

et LANs)

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Twisted Pair Wire

• Advantages– Commonly available and relative low cost,

especially where telephone lines have already been installed

• Disadvantages– Subject to signal distortion, noise and

interference, and the relatively low transmission rates

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Fiber Optic Cable

• Thin wire (usually very pure glass or plastic) surrounded by a reflective cladding that is used to transmit optical signals (light)

• Copper wire cables transmit signals electrically, whereas fiber-optic cables transmit signals by means of light

• More expensive than copper wires, more skill to install

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Fiber Optic Cable

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Fiber Optic Cable

• Not susceptible to lightning, electromagnetic interference (EMI), or radio frequency interference (RFI), and does not generate EMI or RFI

• Much greater bandwidth• Greater transmission distances• Excellent signal quality

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Fiber Optic Cable

• More secure (difficult to tap)

• Thin, requires little space in a conduit

• Lightweight, easy to install

• Better resistance to environment factors, e.g. water

• Generally used to link LANs, WANs, or as backbone of large networks

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Fiber Optic Cable

• Fiber Optics Types:– Multi-mode cable

• Less expensive• Less expensive LED transmitters are used• Larger core, multiple angles of entry

– Single-mode cable• More expensive• More expensive laser transmitters are used• Significant longer cabling distances• Skinny core, only one angle of entry

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Fiber Optic Cable

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Wireless Media (1)

• Infrared

• Radio wave– Bluetooth– Wifi– Mobile Phone network (e.g. GSM, 3G)– Microwave– Satellite

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Wireless Media (2)

• WLAN Components– PCs with WLAN NICs– Access Points (APs), which act as a LAN hub for wirel

ess devices

• Infrastructure mode– Uses APs, with the PCs sending and receiving data to

and from the AP

• Ad-hoc mode– Formed by any two wireless devices, find and associa

te with each other

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Wireless Media (3)

• To install a WLAN that works with the existing LAN infrastructure– At least one AP– A straight-through cable to connect AP to an e

xisting LAN switch– Wireless NICs in end-user devices to commun

icate with the APs

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Wireless Media (4)

• WLAN Organization and Standards– IEEE defines WLAN standards 802.11– Wi-Fi alliance (www.wi-fi.org)

Standard Spectrum Used Max Data Rate

802.11a 5GHz 54Mbps

802.11b 2.4GHz 11Mbps

802.11g 2.4GHz 54Mbps

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LAN Cabling

• Considerations– Ethernet Types– Media– Speed– Distance– Connector

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LAN UTP Cabling Standards

Category Purpose Comments

1 Telephones Not suitable for data

2 Token Ring Supports 4Mbps Token Ring

3 Telephones and 10BASE-T

4 Token Ring Supports 16Mbps Token Ring

5 Ethernet 10BASE-T and 100BASE-T

5e Ethernet Supports Gigabit Ethernet

6 Ehernet Officially supports 1Gbps, working for 10Gbps support

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Ethernet LAN Media and Connectors

Ethernet Types Media Max Segment Length

Connector

10BASE2 50-ohm coax(Thinnet)

185m BNC

10BASE5 50-ohm coax

(Thicknet)

500m Attachment unit interface (AUI)

10BASE-T Cat 3,4,5 UTP 100m RJ45

100BASE-TX Cat 5 UTP 100m RJ45

100BASE-FX 62.5/125 micron multimode fiber

400m Duplex media interface connector (MIC), ST, or SC

1000BASE-T Cat 5 UTP 100m RJ45

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UTP Cable Pinouts

• Key concepts– Ethernet devices (at 10 and 100Mbps Ethenet) use on

e pair of wires to transmit data– Ethernet devices (at 10 and 100Mbps Ethenet) use a

nother pair of wires to receive data– Two pairs of wires are required

• Types– Straight-Through Cable– Crossover Cable– Console Connection and Rollover Cable

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Straight-Through Cable

• To connect an end-user device and a LAN hub or switch

• PC’s NIC uses– Pin 1, 2 to transmit– Pin 3, 6 to receive

• LAN hubs, switches (the other end)– Pin 3, 6 to transmit– Pin 1, 2 to receive

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Straight-Through Cable• TIA/EIA-T568-B or A on BOTH ends of the cable

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TIA/EIA 568-A

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Crossover Cable

• To connect two devices that both want to send on the same pins (two devices of similar ‘type’, e.g. two PCs)

• BOTH sides use– Pin 1, 2 to transmit– Pin 3, 6 to receive

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Crossover Cable• One side is T568-A and T568-B one the other (10BaseT,

100BaseT)• Special arrangement for 1000BaseT

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How to choose?

• Two groups of devices– PC, router, server, AP (use pins 1 and 2 to transmit)– Switch, hub, bridge, repeater (use pins 3 and 6 to transmit)

• When connecting two devices that are similar in regard to which pins they use to transmit, use a crossover cable– e.g. Switch to Switch, Switch to Hub, Hub to Hub, Router to Rout

er, PC to PC, Router to PC

• When connecting two devices that differ in regard to which pins they use to transmit, use a straight-through cable– e.g Switch to Router, Switch to PC, Hub to PC

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Basic Models for PC Communications (1)

• Peer-to-peer– A computer acts as a peer with other computer by acti

ng both as a client and a server– E.g. Sharing a folder in a Windows workgroup– Adv

• Simple to install• No special hardware required• Most OS support peer-to-peer networking• No network administrators required

– Disadv• Security• Loss control

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Basic Models for PC Communications (2)

• Client/Server– A computer acts as either a client or a server– Server usually is more powerful, and requires a more

expensive network operating system (NOS)– Adv

• Centralized control• Security control• Easier data backup

– Disadv• Cost• Network administrators required• If server fails, ….

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Comparing Peer-to-Peer and Client/Server

Comparison Point P-to-P C/S

Requires a dedicated server

Requires a more expensive NOS

Requires a dedicated network administrator

End users must be trained in network administration

More secure

Easier to back up data

Scales well

Single point of failure