Bandwidth is becoming the driving force of technological advancement, replacing computer power, in the new economy. As with Moore's law and computing power, nearly infinite bandwidth available through telecommunications will define the direction of technological progress and areas of growth. Computer networks transfer massive amounts of data daily, with Netflix and Amazon transferring terabytes of data through highly distributed systems. Networks connect diverse devices using common protocols to enable communication between heterogeneous systems and sharing of resources. Transmission media such as twisted pair, coaxial, fiber optic, wireless, and satellite enable data transfer over computer networks in both analog and digital formats.

1. Opening Quote
In the new economy, bandwidth replaces
computer power as the driving force of
technological advance. The telecosmic
vision of nearly infinite wave-borne
bandwidth does for communications that
Moore’s law did for computing: defines
the direction of technological advance, the
vectors of growth, the sweet spots of
finance.
George Gilder (author of Microcosm and
Telecosm)

2. CSSS 5110 Textbook
CSSS 5110 2

3. Chapter 1: Computer Network
Fundamentals
Guide to Computer Network Security

4. Why Networks are Important
• By 2016, Cisco estimates that over 3,000
Petabytes of information will be transferred
over the Internet DAILY!
• Netflix accounts for around 1/3 of primetime
downstream traffic
• During the holiday 2013 season, Amazon sold
an average of 426 items per SECOND!
• As of 2012, every day on Facebook there are:
• 2.7 Billion Likes
• 300 Million Photos uploaded
• >500 Terabytes of data transmitted

5. Computer communication networks
A Computer network is a distributed system
consisting of loosely coupled computers and
other devices.
To form a network, there are communicating
rules or protocols each device in the network
must follow to communicate with another.
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Ethernet
Laptop computer
Laptop computer Workstation
Laser printer
IBM Compatible

6. Internetworking technology enables multiple,
diverse underlying hardware technologies, and
different software regimes to interconnect
heterogeneous networks and bring them to
communicate smoothly
The network elements (computing elements),
network software (operating systems and
browsers), and users all work together
exchanging information and utilizing the
resources in the network
The network elements may be of diverse
technologies and software may be as different as
possible but the whole combo works in unison.
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Computer communication networks

7. Networks
Local Area Network (LAN)
Wide Area Network (WAN)
– Circuit Switched
– Packet Switched
– Frame Relay
– Asynchronous Transfer Mode (ATM)
Wireless Network
Metropolitan Area Network (MAN)
PAN ???

8. A
Networking
Configuration
Figure 1.7 A Networking Configuration
Internet
Router
Router
Ethernet
switch
Information
server
Firewall
host
High-speed link
(e.g., SONET)
LAN PCs
and workstations
Private
WAN
ATM
Network
ATM
switch
High-speed
link
Subscriber
connection
Residential
user Internet service
provider (ISP)

9. Data Communication Media
Technology
Data movement in computer networks
is either analog or digital
– In analog format data is sent as a
continuous electromagnetic wave with a
constant frequency signal called a carrier.
– The carrier signal has three characteristics:
Amplitude modulation – each bit is represented
by a different amplitude of the carrier wave.
Frequency modulation – each bit is represented
by a different frequency of the carrier wave
Phase shift modulation – shifts in the wave
encode binary information.
– In digital encoding binary data is
represented as electrical voltage.
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10. Transmission Media
Medium – The matter or substance over
which data travels
The quality, dependability, and overall
performance of a computer network
depends on the transmission medium
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11. Transmission Media – Physical
Physical media fall into the following
types:
Copper wire – insulated copper wires.
Traditionally used because copper has
low resistance to electrical currents.
Twisted pair – a pair of wires of insulated
copper wires each wrapped around the
other.
Coaxial cables – insulated dual conductor
cables with inner conductor in the core.
Optical fiber – small medium made of
glass and plastics and conducts optical
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12. Media
Physical matter used to carry voice or data
transmissions
Guided media – transmission flows along
physical medium
Wireless (radiated) media – transmission
flows through the air

13. Guided Media
Twisted-pair (TP) cable
– Insulated pairs of wires bundled together
– Wires twisted to reduce electromagnetic
interference
– Some times use additional shielding (STP)
– Commonly used for telephones, LANs
– Characteristics
Price – inexpensive
Distance – typically up to 100m
Use – Telephones, LANs

14. Guided Media
Coaxial cable
– Has a single copper core, plus
outer insulation, shielding,
and inner insulation
– Less prone to interference
– Characteristics
Price - inexpensive (but more
costly than TP)
Distance - up to 2 km (1.2
miles)
Use: Cable TV / Internet

15. Guided Media
Fiber optic cable
– Optical core made of glass
or plastic
– Data transmitted using light
from lasers or LEDs
– Resistant to interference
and corrosion
– Extremely fast data rates
– Characteristics
Price: Expensive
Distance: 500m – 100km
Use: Trunk line / Backbone,
long distance circuits (e.g.,
undersea cables)

16. Guided Media
Fiber optics
– Multimode (about 50 micron core)
– Graded index multimode
– Single mode (about 5 micron core)

17. Wireless Media
Radio
– Wireless transmission of electrical waves
through air
– Each device on network has a radio transceiver
operating at a specific frequency range
– Enables mobile network communication
– Characteristics
Distance: depends on frequency and power
Use: Wireless LANs, cellular and cordless phones,
baby monitors

18. Wireless Media
• Microwave
• High-frequency radio
communication
• Requires line of sight which
may require large antennas
and towers
• Affected by weather
• Characteristics
• Distance: ~60 km (due to
curvature of earth
• Use: Trunk line / Backbone,
long distance
• Satellite
• Special form of microwave
communication
• Long distance leads to
propagation delays

19. Media
Factors to consider in media selection
– Type of network
– Cost
– Transmission distance
– Security
– Error rates
– Transmission speeds

20. Wireless Networks
– Wireless networks fall one of the following three
categories depending on distance as follows:
Restricted proximity network: this network
involves LANs with a mixture of fixed and wireless
devices.
Intermediate/Extended network: this
wireless network is made up of two fixed LANS
component joined together by a wireless
component. The bridge may be connecting LANs
in two nearby buildings or even further.
Mobile network: This is a fully wireless network
connecting two network elements. One of these
elements is usually a mobile unit which connects
to the home network (fixed) using cellular or
satellite technology.
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21. – The three types of wireless communication are
connected using the following basic technologies:
Infrared – uses pulses of infrared light to carry
coded instructions to the receiving network
element
High-Frequency Radio – using electromagnetic
radio waves or radio frequencies (RF
transmission)
Microwave – This is a higher frequency version
of radio communication. It is capable of being
focused in a single direction
Others include laser waves
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Wireless Networks

22. Network Topologies
Computer networks, whether LANs, MANs, or
WANs are constructed based on a topology.
There are several topologies including:
– Mesh – allows multiple access links to a
network element
– Tree – except the root, every element in the
network can only be accessed through its
predecessors
– Bus – all elements are on a shared line
– Star – communication between any two
elements in the network must go through
central node
– Ring – each element in network is directly
connected to two neighbors forming a ring
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23. Network Connectivity and Protocols
These are operational
modalities/procedures for moving
packets between network transmitting
elements
There are two widely used of protocol
suites:
– OSI – Open Systems Interconnection of the
International Organization for
Standardization (ISO)
– TCP/IP – most widely used
Both of these proposed suites are
based on layered stacks of services
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24. Comparison of Network Models

25. Network Model - Layers
Layer Purpose Example Protocols /
Standards
PDU
5. Application User’s access to network, software to
perform work
Packet (or Data)
4. Transport TCP, UDP Segment
3. Network Deciding where the message goes
1. Addressing
2. Routing
IP, ICMP Packet
2. Data Link Move a message from one device to the next
1. Controls hardware
2. Formats the message
3. Error checking
Ethernet Frame
1. Physical Transmits the message 100BASE-T, 802.11ac
HTTP, SMTP, DNS, FTP,
DHCP, IMAP, POP, SSL
End-to-End Management
1. Link application layer to network
2. Segmenting and tracking
3. Flow control

26. Copyright 2011John Wiley & Sons, Inc. 1 - 26
Message Transmission Using
Layers

27. Protocols
Used by network model layers
Sets of standardized rules to define how to
communicate at each layer and how to
interface with adjacent layers
receiver
sender
Layer N
Layer N-1
Layer N+1
Layer N
Layer N-1
Layer N+1

28. 1 - 28
Message Transmission Example

29. Network Models
• Layers allow simplicity of networking in some ways
• Easy to develop new software that fits each layer
• Relatively simple to change the software at any level
• Matching layers communicate between different computers
and computer platforms
• Accomplished by standards that we all agree on; e.g., physical
layer at the sending computer must match up with the same layer
in the receiving computer
• Advantages of Layers
• Networking functionality is modular and the software/hardware at
any layer can be more easily substituted; e.g., substitute wired
for wireless at the physical layer
• Easier to troubleshoot or make changes to one layer at a time
• Application developers only need to worry about the application
layer in their programs
• Disadvantages of Layers
• Inefficient because the encapsulation/de-encapsulation at each
layer requires processing
• Inefficient because encapsulation in a PDU increases overhead at
each layer

30. Network Services
Networks work effectively when
network services move data in the
network. These services fall into two
categories:
– Connection services to facilitate the
exchange of data between the two network
communicating end-systems with as little
data loss as possible and in as little time as
possible.
– Switching services to facilitate the
movement of data from host to host across
the length and width of the network mesh
of hosts, hubs, bridges, routers and
gateways
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31. • Two connection services are provided by most
digital networks:
• Connected-oriented services – offer prior
connection controls in a form of three-way
handshake
• Connectionless service – no handshake is needed
no prior information and no warnings
• Two switching services are provided:
• Circuit switching – The network must reserve all
resources needed for the communication session
before any communication begins. Example:
telecommunications sessions.
• Packet switching networks are referred to as Packet
networks. There are two types of these networks
• Virtual circuit networks – logical connection is
needed before a packet is sent
• Datagram and networks
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Network Services

32. Network Connecting Devices
The computing elements in a network
(LAN, WAN) are interconnected using
connecting devices commonly referred
to as nodes
There are several types:
– Hub – the simplest connecting devices. It
takes in inputs and retransmits them
verbatim
– Bridge – it is similar to the hub, however,
bridges filter incoming data packets for
addresses before the packets/frames are
re-transmitted
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33. – Switch – a newer version of a bridge with high
a performance capacity and can accommodate
higher numbers of interfaces
– Router – general-purpose nodes that
interconnect two or more heterogeneous
networks; dedicated special purpose
computers with their own Address Resolution
Protocol (ARP) and IP addresses
– Gateway – this is a more versatile device that
can provide translation of and between
networking technologies such as OSI and
TCP/IP
Gateways can connect two or more autonomous
networks
They perform all functions of a router and more
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Network Connecting Devices

34. Network Technologies
• Network technologies in each network
category.
• LAN Technologies
• Star-based Ethernet (IEEE 802.3) LAN
• Wireless (IEEE 802.11ac)
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35. – WAN Technologies:
Integrated Services Digital Network (ISDN)
X.25
Other WAN Technologies
– Frame Relay is a packet-switched network with the ability to
multiplex many logical data conversions over a single connection. It
provides flexible efficient channel bandwidth using digital and fiber
optics transmission. It has many similar characteristics to X.25
network except in format and functionality.
– Point-to-point Protocol (PPP) is the Internet Standard for
transmission of IP packets over serial lines. The point-to-point link
provides a single, pre-established communications path from the
ending element through a carrier network, such as a telephone
company, to a remote network. These links can carry datagram or
data-stream transmissions.
– xDirect Service Line (xDSL) is a technology that provides an
inexpensive, yet very fast connection to the Internet.
– Switched Multi-megabit Data Service (SMDS) is a connectionless
service operating in the range of 1.5-100Mbps; any SMDS station
can send a frame to any other station on the same network.
– Asynchronous Transfer Mode (ATM) – Quality of Service.
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Network Technologies