Physical-Aspects-of-Computer-Networking.pdf

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Communications Block Diagram

Physical Aspects of Computer Networking

* Property of STI Page 1 of 60

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Data Communications Block Diagram

Physical Aspects of Computer Networking

* Property of STI Page 2 of 60

1 _________________ ___________________ ___________________ ___________________ ___________________ ___________________ ___________________ ___________________ ___________________ ___________________ ___________________ ___________________ 2 _________________ ___________________ ___________________ ___________________ ___________________ ___________________ ___________________ ___________________ ___________________ ___________________ ___________________ ___________________

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Bi-directional Communication

Physical Aspects of Computer Networking

* Property of STI Page 3 of 60

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Electromagnetic Signals 

used to carry information from one end to another over a physical media

Electromagnetic Signals Representation

Physical Aspects of Computer Networking

* Property of STI Page 4 of 60

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Non-Sinusoids and its Spectra

Physical Aspects of Computer Networking

* Property of STI Page 5 of 60

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Square Wave: Fundamental + 1

Physical Aspects of Computer Networking

* Property of STI Page 6 of 60

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Square Wave: Fundamental + 2

Physical Aspects of Computer Networking

* Property of STI Page 7 of 60

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Square Wave: Fundamental + 3

Physical Aspects of Computer Networking

* Property of STI Page 8 of 60

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Square Wave: Fundamental + 4

Physical Aspects of Computer Networking

* Property of STI Page 9 of 60

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Square Wave: Fundamental + 5

Physical Aspects of Computer Networking

* Property of STI Page 10 of 60

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Physical Media’s Frequency Response

Physical Aspects of Computer Networking

* Property of STI Page 11 of 60

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The Twisted-Pair Cable 

wire-pair cables that are twisted together to minimize the wires from introducing interference to other cables or wires

Physical Aspects of Computer Networking

* Property of STI Page 12 of 60

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Structured Cabling: EIA/TIA 568-A

Physical Aspects of Computer Networking

* Property of STI Page 13 of 60

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Structured Cabling: EIA/TIA 568-B

Physical Aspects of Computer Networking

* Property of STI Page 14 of 60

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Structured Cabling: In-Building Wiring Layout

Physical Aspects of Computer Networking

* Property of STI Page 15 of 60

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Ethernet Cross-Over Cable

Physical Aspects of Computer Networking

* Property of STI Page 16 of 60

15 _________________ ___________________ ___________________ ___________________ ___________________ ___________________ ___________________ ___________________ ___________________ ___________________ ___________________ ___________________ 16 _________________ ___________________ ___________________ ___________________ ___________________ ___________________ ___________________ ___________________ ___________________ ___________________ ___________________ ___________________

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Structured Cabling: Distribution Frames

Physical Aspects of Computer Networking

* Property of STI Page 17 of 60

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Structured Cabling: Cable Distance from Power Source Minimum Separation Distance from Power Source at ≤480V Condition

< 2kVA

2 – 5kVA

> 5kVA

Unshielded Power Lines Or Electrical Equipment In Proximity To Open Or NonMetal Pathways

5in/ 12.7cm

12in/ 30.5cm

24in/ 61.0cm

Unshielded Power Lines Or Electrical Equipment In Proximity To Grounded MetalConduit Pathways

2.5in/ 6.4cm

6in/ 15.2cm

12in/ 30.5cm

Power Lines Enclosed In Metal-Conduit (Or Equivalent Shielding) In Proximity To Grounded Metal-Conduit Pathways

--

6in/ 15.2cm

12in/ 30.5cm

Transformers and/or Electric Motors

40in/1.02m

Fluorescent Lighting

12in/30.5cm

Physical Aspects of Computer Networking

* Property of STI Page 18 of 60

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Coaxial Cable 

pair of conductors lying on the same axes, hence the term “Co-Axial”

Physical Aspects of Computer Networking

* Property of STI Page 19 of 60

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Fiber-Optic Cable 

use optical signals rather than electric to carry information from one end to another



made of glass or high-grade plastic

Physical Aspects of Computer Networking

* Property of STI Page 20 of 60

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Typical Core – Cladding Ratio

Physical Aspects of Computer Networking

* Property of STI Page 21 of 60

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Fiber Optic Cables and their Bandwidth Mode

Wavelength (nm)

Size (microns)

Bandwidth (MHz/km)

Multimode

850

62.5/125

200

Multimode

850

50/125

600

Multimode

850

100/140

300

Multimode

1300

62.5/125

800

Multimode

1300

50/125

1500

Multimode

1300

100/140

500

Multimode

1550

100/140

500

Single-mode

1300

9.3/125

~ infinite

Single-mode

1550

8.1/125

~ infinite

Physical Aspects of Computer Networking

* Property of STI Page 22 of 60

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Electromagnetic Spectrum 

range of electromagnetic radiation from Radio Waves to Gamma Rays

Physical Aspects of Computer Networking

* Property of STI Page 23 of 60

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Radio Spectrum 

range of radio communications signals

Physical Aspects of Computer Networking

* Property of STI Page 24 of 60

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Radio Wave Propagation Patterns

Physical Aspects of Computer Networking

* Property of STI Page 25 of 60

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Antenna Coverage Types

Physical Aspects of Computer Networking

* Property of STI Page 26 of 60

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Radio Repeaters 

devices used to redirect or relay signals when direct transmitter and receiver communications is not possible



Types:  

Passive – no signal regeneration Active – with signal regeneration

Physical Aspects of Computer Networking

* Property of STI Page 27 of 60

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Bus Topology 

connects devices directly to a laid out media through special connectors or vampire taps

Physical Aspects of Computer Networking

* Property of STI Page 28 of 60

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Ring Topology 

connects devices together through a closed-loop or ring media

Physical Aspects of Computer Networking

* Property of STI Page 29 of 60

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Star Topology 

connects devices together through a central device

Physical Aspects of Computer Networking

* Property of STI Page 30 of 60

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Modulation 





process of using a carrier signal to transport raw information signal from the transmitting end to the receiving end used in radio transmission to reduce the size of antenna also used to separate various information sources from interfering with one another within a channel 

known as frequency division multiplexing (FDM

Physical Aspects of Computer Networking

* Property of STI Page 31 of 60

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Modems 

devices that are able to both modulate and demodulate 



modulate information signals before transmission demodulate received modulated signals

Physical Aspects of Computer Networking

* Property of STI Page 32 of 60

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Analog to Digital Conversion

Physical Aspects of Computer Networking

* Property of STI Page 33 of 60

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Multiplexing (MUX) 

process of sharing a channel among various information sources  



Frequency Division Multiplexing (FDM) 



subdividing the channel into sub-channels each information source is assigned a subchannel

sub-channels are in the form of frequency ranges

Time Division Multiplexing (TDM) 

sub-channels are in the form of time-slots

Physical Aspects of Computer Networking

* Property of STI Page 34 of 60

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FDM Hierarchy FDM Level

Number of Voice Channels

Voice Channel

1

0 – 4kHz

Group

12

60 – 108kHz

Bandwidth Range

Super Group

60

312 – 552kHz

Master Group

600

564 – 3,084kHz

Jumbo Group

3,600

564 – 17,544kHz

Physical Aspects of Computer Networking

* Property of STI Page 35 of 60

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PCM Frames

Physical Aspects of Computer Networking

* Property of STI Page 36 of 60

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TDM Hierarchy: European

Physical Aspects of Computer Networking

* Property of STI Page 37 of 60

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TDM Hierarchy: North American

Physical Aspects of Computer Networking

* Property of STI Page 38 of 60

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Serial vs. Parallel Transfers

Physical Aspects of Computer Networking

* Property of STI Page 39 of 60

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Synchronous Transmission 

both transmitter and receiver use the same timing device (clock)

Physical Aspects of Computer Networking

* Property of STI Page 40 of 60

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Asynchronous Transmission 

transmitter and receiver devices use difference clocks

Physical Aspects of Computer Networking

* Property of STI Page 41 of 60

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Framing

Physical Aspects of Computer Networking

* Property of STI Page 42 of 60

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RS-232: DTE – DCE Flow Control

Physical Aspects of Computer Networking

* Property of STI Page 43 of 60

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LRC/VRC – an example

Physical Aspects of Computer Networking

* Property of STI Page 44 of 60

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LRC/VRC – with a bit-error

Physical Aspects of Computer Networking

* Property of STI Page 45 of 60

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CRC-Character Generation – an example

Physical Aspects of Computer Networking

* Property of STI Page 46 of 60

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CRC Validation – an example

Physical Aspects of Computer Networking

* Property of STI Page 47 of 60

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CRC Validation – with errors

Physical Aspects of Computer Networking

* Property of STI Page 48 of 60

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Checksum – an example

Physical Aspects of Computer Networking

* Property of STI Page 49 of 60

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IEEE Project 802

Physical Aspects of Computer Networking

* Property of STI Page 50 of 60

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Multi-Access Network 

network where simultaneous access to the medium is possible among computers

Physical Aspects of Computer Networking

* Property of STI Page 51 of 60

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Point-to-Point Network 

network where only two computers are exchanging information over the medium

Physical Aspects of Computer Networking

* Property of STI Page 52 of 60

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CSMA/CD 

contention access method that allows several devices to access the medium in a “first-come, first-served” basis

Physical Aspects of Computer Networking

* Property of STI Page 53 of 60

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CSMA/CD – with collision

Physical Aspects of Computer Networking

* Property of STI Page 54 of 60

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Token-Passing 

deterministic access method that allows several devices to access the medium in an orderly fashion

Physical Aspects of Computer Networking

* Property of STI Page 55 of 60

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MAC Address 

stands for Media Access Control (MAC)



physical identifier used to distinguish one network device from another



length is 48-bits, or 6-bytes

MAC Address Format

Physical Aspects of Computer Networking

* Property of STI Page 56 of 60

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Repeater 

also known as Hub



layer 1 network device used to: 



interconnect network devices together increase its signal strength allowing for network reach extension

Physical Aspects of Computer Networking

* Property of STI Page 57 of 60

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Interconnectivity with Hubs

Physical Aspects of Computer Networking

* Property of STI Page 58 of 60

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Bridge 

layer 2 network device used to connect two network segments together



apart from network extension, bridges allows for traffic isolation

Bridge vs. Hub – Traffic Performance Comparison Physical Aspects of Computer Networking

* Property of STI Page 59 of 60

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The Bridge Forwarding Table

Physical Aspects of Computer Networking

* Property of STI Page 60 of 60

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