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Introduction to Information
Networking
How to get the bits from here to there.
Or
If I was going there I wouldn’t start
from here.
What is a Network?
Devices and media used to transfer
information from place to place in
real-time.
 Examples:

• Phone System
• Cable TV System
• Internet

Today these all converge.
Basic Network Components


Hosts: Communicators. Devices that send
and receive data.
Devices: used to interconnect hosts.
• Hubs, switches routers……

Media: used to interconnect devices.
• Ethernet, Fiber, Token Ring, Coaxial, Space
(WiFi)

Shared Peripherals: Assets connected to
a host (printer, cd-tower, web camera)
Network Roles
Client: user of data
 Server: provider of data or service
 Client/Server: provider and
consumer of data.

• In the real world, all servers are also
clients. As an example, web servers use
Domain Name Servers to look up
Internet Addresses.
Source Channel and Destination
Source: needs to send a message.
 Destination: where the message
should go.
 Channel: how to get there from here.

Example 1




Fred needs to Wilma to pick up bread on
the way home.
Fred sends e-mail to Wilma.
Source=Fred; Destination=Wilma
Channel:
• Ethernet TCP/IP from Computer to Home
Router
• Home Router to ISP via cable/dsl/..
• Home ISP to Wilma’s employer’s ISP via Cloud
(magic).
• Employer’s Router to Wilma’s Computer via
Ethernet
Example 2




Betty needs to Barney to pick up bread on
the way home.
Betty sends ext message to Barney.
Source=Betty; Destination=Barney
Channel:
• SMS Cellular Connection from Betty’s Cell to
nearest available Cell Tower
• Betty’s Cell Tower to Cell Tower near Barney
via Public Switched Telephone Network (PSTN)
aka Plain Old Telephone System (POTS).
• Barney Cell Tower to Barney’s cell using SMS.
Protocols
Rules for Communication.
 Human Example: Phone Call

• Caller Dials Number
• PSTN finds receiver and creates
connection.
• Receiver Phone Rings. Receiver Picks Up
• Caller Identifies themselves.
• Both talk using the same language.

Hopefully they both listen for silence before
speaking.
Protocols are Everywhere
Encoding: preparing the message for
transfer.
 Format: Agreeing on what is where.
 Size: Setting a limit on how much
can be sent at once.
 Timing: when (access), how much
(flow control), timeouts (max wait).

Protocol Matching

All Protocols must match for
communication to occur.
• Ethernet is a protocol to physically
transfer data. Physical protocols must
match for all connecting devices.
• TCP/IP is a set of protocols to send data
over a physical network. Communication
Protocols must match at ends.
Network Stacks
Communication across networks is
difficult and needs to be chunked
into smaller manageable pieces.
 OSI has a seven layer protocol that
defines the “ideal” network.
 TCP/IP is the real-world winner of
the network protocols has a four
layer protocol.

OSI Model
Layer Name
What it does.
Application
Defines the rules.
Presentation
Data type, Encryption
Session
Open, close communication
Transport
End-to-end reliability,
slices/dices/reassembles
Network
Routing. How to get there ….
Data Link
Node-to-node, error ID.
Physical
Spits Bits. Rules for spitting bits
Mnemoic: All People Seem To Need Data Processing. There are worse!
TCP/IP Stack
Layer Name What it Does
Application
Transport
Internet
Network
Interface
Defines service rules,
encryption, encapsulation
End-to-end reliability,
chunking, sequencing
Routing
Frames data for transmission
and transmits. Is equal to the
Network Interface Card.
Data Transmission

Copper Wire
• Phone System
• Ethernet

Fiber Optic
• Long Haul
• Cable Distribution

Airwaves
• Radio/TV
• WiFi
• Bluetooth
Data Transmission Terms
Attenuation: Loss of signal over
distance
 Noise: random unwanted signals.

• Electric motors, fluorescent lights,
crosstalk

Signal Spread: high frequency
attenuates more than low.
Copper Wire

Coaxial Cable.
• Advantages
• Highly immune to RFI
• High SNR
• Disadvantages
• Cost, size, Installation,
Access

Twisted Pair
• More twists less noise
• Can be shielded but is
expensive (manufacturing
and installing)
Optical Fiber







Transmits Photons.
Core is low
attenuation.
Cladding is high
attenuation.
Boundary is reflective.
Single (60-100km)
and MultiMode (2km)
That’s about 36-62
miles versus 1.2 miles
Disadvantage: $$$$$
Wireless
Unguided Transmission.
 Higher Frequencies do not bend
 Wireless can reflect off different
surfaces. i.e. Microwave reflects off
stone and steel but passes through
wood or sheet rock.
 Prone to interference (other devices)


Common Bands: 0.9, 2.5, 5.0, & 5.8 GHZ
Using Waves to Transmit Data
f(t) = Asin(2πft + θ)
The Sine Wave
Amplitude Modulation
Frequency Modulation
Transmitting Digital Data using
Analog Signalling
PSK, a finite number of phases are
used.
 FSK, a finite number of frequencies
are used.
 ASK, a finite number of amplitudes
are used.
 QAM, a finite number of at least two
phases, and at least two amplitudes
are used.
