Transcript chapter 2 - Faculty Personal Homepage

Local Area Networks
Content
Chapter 1: Introduction & Basic Principles
Chapter 2: Topics in Data Communications
Chapter 3: Protocols and the TCP/IP Suite
Class 1
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General Course Information
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Instructor Info
General & University Info
Book & Course Material
Course Schedule
Grading & Exams
Homework
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Overview of LANs and MANs
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The Need for Networking
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Driven by the decreasing cost of computer hardware
and the dramatic increase in its capabilities
Factors driving the creation of a new set of advanced
desktop applications (with more on the way):
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Image Processing
Speech Recognition
Videoconferencing & Multimedia
Three characteristics are of greatest use in
classifying communication networks :
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Geographic Reach
Topology
Transmission Medium
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LANs, MANs, and WANs
Classification based on Geographic Reach
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Characteristics of Wide Area Networks (WANs)
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Large Geographic Area
Requires the crossing of public right-of-ways
Partially or fully relies on common carrier circuits
Slower speeds than LANs & MANs, although the spread
of fiber optic facilities is beginning to change this
Examples of WAN technologies:
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ISDN (BRI & PRI)
SONET
Frame Relay
ATM
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Comparison
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LANs, MANs, and WANs
Classification based on Geographic Reach
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Characteristics of Local Area Networks (LANs)
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Small Geographic Area
A LAN is completely owned and operated by a single
organization
The data rates of a LAN are usually an order of magnitude
higher than a WAN
Characteristics of Metropolitan Area Networks
(MANs)
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Occupy the middle ground between LANs and WANs
MANs typically adapt and extend LAN technologies to cover a
larger geographic area
Have provided greater bandwidth at lower costs within
metropolitan areas
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LANs, MANs, and WANs
Applications
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Personal Computer Local Networks
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Even with the proliferation of low cost PCs that allow
staff members to do their own processing, there are
still important reasons for networking these
computer systems
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File and data sharing
Share expensive network resources (printers, storage,
etc.)
Real-time and near real-time collaborative efforts
Easy file and data protection (networked backups)
Financially, the networking of low-cost PCs usually
necessitates a low cost network technology
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LANs, MANs, and WANs
Applications
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Back-end & Storage Area Networks (SANs)
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Used in large computer installations (e.g. mainframes)
Key requirement is high-speed bulk data transfer
between a small number of systems in a limited area
Unlike traditional server-attached storage, SANs provide
storage attached directly to the network (Increases
efficiency)
Key reasons for implementing a SAN
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Online backup systems
Load leveling across multiple systems (storage ‘farms’)
Wider accessibility of large amounts of data
These requirements drive SANs to high bandwidth and
high cost installations
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LANs, MANs, and WANs
Applications
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High-Speed Office Networks
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Newer (particularly multimedia) applications are driving
the development of higher speed LANs that are
replacing the older PC Local Networks
Use different technologies than SANs because they are
meant to service a larger number of systems dispersed
over a wider area
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LANs, MANs, and WANs
Applications
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Backbone Local Networks
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Diverse requirements in typical organizations have led
to the adoption of a multi-tiered LAN architecture
Advantages of the multi-tiered LAN over the single-LAN
architecture
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Greater reliability
Greater capacity
Lower overall cost
The core of the multi-tiered LAN architecture is the
backbone -- a high bandwidth network connecting
together lower-speed, lower-cost LANs
If the organization is geographically dispersed the
backbone may be a MAN
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LANs, MANs, and WANs
Local Network Architecture
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Information Distribution
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When setting requirements for a network installation,
user traffic patterns must be explored
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What type of data will traverse the network?
How is this data distributed?
What is to be connected (PCs, servers, mainframes, all of
the above, etc.)?
As mentioned earlier, a multi-tiered network is typically
the best approach to meeting organizational needs
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Typically a two or three tiered architecture is used
Usually evolve in one of two ways, depending on how
centralized the organization’s IT rules are:
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Bottom-up
Top-down
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LANs, MANs, and WANs
LANs, WANs, and the Internet
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Most organizations are geographically distributed & must
deal with connecting together widely dispersed LANs
Most organizations have two choices for WAN connectivity
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A private WAN
A public network or the Internet
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LANs, MANs, and WANs
LANs, WANs, and the Internet
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A private WAN
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Provides a dedicated connection from leased lines or a similar
service
Good for security & sites with high & predictable inter-site
traffic
Can be expensive, especially for smaller organizations & sites
A public network or the Internet
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Provides an inexpensive & quick solution for connectivity
Can also provide an access path for mobile workers
Performance is an issue with real-time traffic or large data
transfers
Virtual private networks (VPN) used to address security:
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Encapsulation & tunneling are the key concepts
IPsec is an example of a network layer VPN technology
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Homework & Reading
Assignment #1 -- due at class #3 (two weeks)!
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Assignment #1
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Stallings Chapter 3: 3.3, 3.5, 3.8
Search on the Web for a manufacturer of Category 7 twisted
pair cabling & document the following:
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Manufacturer Name
Cable specs: attenuation, NEXT, FEXT paramters
Basic description of the cable’s construction (a diagram helps)
Is the cable sold as part of a structured cabling system? If so,
give a brief description of what components are in the system
Install the OPNet software and complete Lab0 (“Getting
Started”). Answer the questions and also print out and
submit the graphs you generate in the final section of the
2nd lesson (“Comparing Results”).
Reading
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This Class: Stallings Chapters 1 through 3
Next Week: Chapters 4 through 6
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Chapter 2 – Topics in Data
Communications
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Data Communications Concepts
Introduction
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Essential definitions for Data Communications
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Data, Signaling, & Transmission Systems
Analog & Digital
Data are entities that convey meaning, while signaling is
the transfer of encoded data thru a transmission system
Analog versus digital signaling
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Digital signaling usually less expensive than analog but care
must be taken to properly engineer system (e.g. attenuation)
Combinations of analog & digital data and signals
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Analog data -> Analog signals
Digital data -> Analog signals (Key equipment is a modem)
Analog data -> Digital signals (Key equipment is a codec)
Digital data -> Digital signals
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Data Communications Concepts
Analog versus Digital Transmission Systems
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Analog systems transmit analog signals without regard for
the content of the signal
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Amplifiers are used to boost the energy of the signal
Amplifiers also boost the strength of any noise on the line,
introducing the possibility that the signal could be lost
Digital Transmission Systems are concerned with the
content of the signal
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Repeaters used to regenerate the signal, overcoming
attenuation
Repeaters output a new copy cleansed of any noise, so noise
is not cumulative (however, bit errors can still occur if the
signal is not regenerated before it degrades too much)
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Data Encoding Techniques
Introduction
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Encoding is the process of mapping digital data into the
appropriate signal elements for transmission
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Encoding schemes are chosen to assist the receiver in its
two key tasks:
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Encoding may be very complex or as simple as using binary
signal elements (0s and 1s)
Determining when the signal element begins and ends (so
sampling is done at the proper time)
Determining the value of the signal element (Is it a one? A
zero?)
Attenuation, data rate, & noise all play a role at receiver
With analog data the encoding scheme also plays a key
role in system performance but the details are a little
different
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Data Encoding Techniques
Analog encoding of digital data
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The basis for analog encoding is a base signal called the
carrier signal
Digital data is encoded (and decoded at the other end) by
a device called a modem
Three basic schemes for analog encoding of digital data:
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Amplitude Shift-keying (ASK)
Frequency Shift-keying (FSK)
Phase Shift-keying (PSK)
These schemes can be combined for more sophisticated
digital transmission systems that carry more data per
signal element
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Data Encoding Techniques
Analog encoding of digital data
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Amplitude-shift Keying
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Frequency-shift Keying
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Data represented by different amplitude levels of the carrier
signal
Simplest scheme, but inefficient and prone to noise
Most valuable use is in optical systems
Data represented by different frequency values near the
carrier signal frequency
Less prone to errors but requires more complex circuitry
Phase-shift Keying
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Data represented by different phase shifts to the carrier
frequency
More efficient and noise resistant than ASK or FSK but
requires more complex circuitry
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Data Encoding Techniques
Digital Encoding of Digital Data
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The most common way to encode digital data is to use a
binary signaling scheme consisting of two voltage levels
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NRZ-L (Non-Return to Zero Level)
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Each voltage level defines the value of the digital data
Used only in very short connections
NRZ-I (Non-Return to Zero Inverted)
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A transition at the beginning of a signal unit denotes a
binary one
This type of signaling is known as differential signaling;
it is usually easier to detect a transition out of the
background noise and the signals are polarity
insensitive
Clocking and DC current are usually problems
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Data Encoding Techniques
Digital Encoding of Digital Data
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Manchester Encoding
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Example of a bi-phase coding; up to two signaling transitions
per signal element (needs more bandwidth to transmit a
given data rate)
The mid-signal transition provides clocking as well as the
data value (a zero data element is a high-to-low transition
and a one is a low-to-high transition)
Used in Ethernet LANs (IEEE 802.3)
Differential Manchester Encoding
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Another bi-phase code
The mid-signal transition provides clocking; the transition at
the beginning of the signal element represents data (a zero
data element has no transition at the beginning of a bit time
while a one does)
Used in Token Ring LANs (IEEE 802.5)
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Data Encoding Techniques
Digital Encoding of Analog Data
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Pulse Code Modulation (PCM) is an example – used in the
phone system to transmit analog data across digital
networks
Sampling rate based on the Nyquist theorem
Digitized into 8 bit samples based on a nonlinear scale
that provides good reproduction of the human voice
Other digital-to-analog encoding schemes:
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Adaptive Differential Pulse Code Modulation (ADPCM) used with voice transmission
Delta Modulation - used rarely but also for voice
transmission systems
Code Excited Linear Prediction (CELP) - used in very lowbandwidth voice and multimedia communication systems
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Multiplexing
Introduction
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Allows a transmission system to carry multiple
independent signals simultaneously for higher efficiency
Two general schemes are in use: FDM and TDM
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Frequency Division Multiplexing (FDM)
 Takes advantage of the fact that the useful bandwith of
the transmission system exceeds the required bandwidth
of a given signal
 Allows frequency spectrum to be divided & allocated to
different signal sources
 Most commonly used with analog signaling and
transmission
Time Division Multiplexing (TDM)
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Multiplexing
Techniques
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Allows a transmission system to carry multiple
independent signals simultaneously for higher efficiency
Two general schemes are in use: FDM and TDM
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Time Division Multiplexing (TDM)
 Takes advantage of the fact that the maximum bit rate
of the system exceeds the required bit rate of the digital
signal
 Each source is allocated a ‘time slot’ in the multiplexor
 Analog signals can be time division multiplexed, but it is
very uncommon
 Two varieties of TDM: statistical and fixed time-slot
Both FDM and TDM can be used in a synchronous or
asynchronous manner
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Transmission Media
Introduction
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The transmission media is the physical signal path
between the transmitter and the receiver
Can be guided (cables, waveguides, etc.) or unguided
(open air)
Our key concerns for transmission systems are data rate
and distance
Influencing factors:
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Bandwidth of the media
Transmission impairments
Interference
Number of Receivers
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Transmission Media (2)
Twisted Pair Cable
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Consists of a minimum of two copper wires twisted
together and enclosed within a protective sheath
Advantages: inexpensive, easy to work with, may
already be installed where needed
Disadvantages: limited in distance, data rate, and
bandwidth; susceptible to interference
Comes in two general varieties: shielded twisted pair
(STP) and unshielded twisted pair (UTP)
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Shielding provides more noise immunity, especially at lower
data rates
STP costs more and is more difficult to work with
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Transmission Media (3)
Twisted Pair Cable
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Category 3 and Category 5 UTP
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Rating standards devised by the Electronic Industries
Association (EIA)
The higher the category the better the cable; Cat 3
designed to support 10Mbps Ethernet while Cat 5 will
support 100Mbps Ethernet
The key difference between the two categories is the
number of twists per unit length of cable
Near-end Crosstalk (NEXT) is a key transmission
impairment to minimize in any twisted pair cabling system
While these are regarded as the most commonly found UTP
installations, there are higher performance UTP choices
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Transmission Media
Twisted Pair Cable
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High-performance Twisted Pair
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Category 5e (or enhanced Category 5): supports 125-MHz
bandwidth on all four pairs, allowing Gigabit Ethernet to run
over UTP up to 100 meters
Category 6: supports over 200-MHz bandwidth on all four
pairs; could potentially run high data rate ATM connections
Category 7: will require special shielding and will likely
support up to 700-MHz bandwidth on each pair
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Transmission Media
Coaxial Cable
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Provides a two conductor transmission system where one
conductor is situated inside the outer hollow conductor
with an insulating dielectric in between
Because of its structural characteristics coaxial cable is
more resistant to noise than twisted pair
Harder to work with and more expensive than twisted pair
Coax systems can be grouped in three categories based
on the type of signaling used:
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Baseband: digital signaling occupies the entire spectrum of
the cable
Broadband: carrier-band analog signaling is used, allowing
multiple channels on the cable
Carrierband: carrier-band analog signaling with low-end
components; signal occupies entire spectrum of cable
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Transmission Media
Fiber Optic Cabling
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A transmission system composed of a guided medium that
allows the propagation of optical rays
A range of fiber optic cabling exists for various needs,
from ultra-pure fused silica (expensive but high data rate)
to plastic (cheap with lower data rate for short runs)
Advantages
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Huge bandwidth capacity
Smaller size and lightweight
Lower attenuation
Electromagnetic isolation (high security & minimal
interference)
Common transmitters used are LEDs for (low-cost & lowspeed systems) or Injection Laser Diodes (long-haul highspeed systems)
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Transmission Media
Fiber Optic Cabling
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Basic fiber types
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Step-index multimode: cheapest to manufacture but allows
light to travel different paths down the fiber, causing signal
distortion & lowering the maximum data rate.
Graded-index multimode: Higher grade of fiber with a
varying refractive index that limits distortion of the signal.
Singlemode: contains a core with a diameter close to the
wavelength to be transmitted; allows only a single
transmission path down the fiber which practically eliminates
distortion
Three wavelength ‘windows’ provide the best light
propagation: 850, 1300, & 1550 nm
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Most multimode systems use the 850 nm window
Long-haul transmission systems use the 1550 nm window
because loss is lower at higher wavelengths
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Transmission Media
Unguided Media
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Microwave
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Occupies the frequency spectrum from 1GHz to 30GHz; can
provide either a highly directional or omni-directional system
There are 3 main challenges to using microwave for data
transmission:
 Frequency Allocation and licensing
 Interference
 Security
Infrared
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Uses light in the infrared spectrum for data transmission
Must be used line-of-sight or in an environment that allows
infrared waves to be reflected
Less issues associated with microwave but only for
specialized uses
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Data Communication Networks
Introduction
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For most WAN and MANs, transmission of data usually
involves a number of intermediate switching nodes that
move the data between source and destination
The complete set of end nodes, data links, & intermediate
switches is known as a communications network
There is a spectrum of communication switching
techniques; the two main variations are circuit and packet
switching
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Data Communication Networks
Circuit Switching
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Communication between end nodes is via a dedicated
communications channel
Communications via circuit switching involves three
phases:
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Circuit establishment: the path is established before any
data is transferred
Data transfer
Circuit disconnect: release of resource dedicated to the
connection
The fixed capacity of the channel is allocated for the
duration of the connection; can be very inefficient with
bursty traffic
Circuit switching is best suited for synchronous data such
as voice or real-time video
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Data Communication Networks
Packet Switching
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Packet switching breaks data up into a series of packets,
each appended with enough control information to ensure
the packet transits the network successfully from source
to destination
Developed to address problems certain data sources have
with circuit switching:
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Bursty data transmission
Source and destination must operate at the same data rate
Inefficient resource allocation
Connection setup can be too slow for certain applications
In addition to addressing the above problems, packet
switching also has other benefits for data transmission:
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Under heavy load the network will accept packets but delay
increases
Priorities for transmission of the packets can be set
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Data Communication Networks
Packet Switching
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Two main varieties: datagrams or virtual circuits
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Datagram Approach: Each packet is routed independently of all
others, leading to the following consequences:
– Packets don’t take the same routes, may arrive out of sequence
– No circuit setup time, so data flow begins without delay
– Data can easily flow around problems in the network
Virtual Circuit Approach: a preplanned route through the
network is established before any data is sent
– Requires circuit setup and teardown but routes along the
connection are shared with other packets
– A routing decision does not have to be made for every packet
– May provide enhanced services such as error & flow control,
and packet sequencing not available in a datagram
environment
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Data Communication Networks
Hybrids
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Multi-rate Circuit Switching
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Frame Relay
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Extends circuit switching to allow one or more fundamental
channels to be bundled together to provide a range of data
connection rates
Examples of multi-rate switching are ISDN and inverse
multiplexing
WAN service based on a connection-oriented packet data protocol
Frame Relay evolved from X.25; the new protocol was
streamlined by eliminating features necessary on earlier, less
reliable X.25 data communications networks
Cell Relay (ATM)
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A further evolution of connection-oriented packet data services
Unlike frame relay fixed length data units (cells) are used which
allow high-speed hardware based switching
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Comparison
Packet Switching vs. Circuit Switching
Is packet switching a “clear winner?”
 Great for bursty data
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Excessive congestion: packet delay and loss
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Resource sharing
No call setup
Protocols needed for reliable data transfer, congestion control
Q: How to provide circuit-like behavior?
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Bandwidth guarantees needed for audio/video apps
Still an unsolved problem
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Routing
Routing in Packet-Switched Networks
 Goal: move packets among routers from source to
destination
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Datagram network:
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We’ll study several path selection algorithms (chapter 5)
Destination address determines next hop
Routes may change during session
Analogy: postal service
Virtual circuit network:
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Each packet carries tag (virtual circuit ID), tag determines
next hop
Fixed path determined at call setup time, remains fixed
through call
Routers maintain per-call state
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Taxonomy
Telecommunication
networks
Circuit-switched
networks
FDM
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Packet-switched
networks
TDM
VC Based
networks
Class 1: Introduction to LANs & WANs
Datagram
networks
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Network Access
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End hosts are connected
to edge routers through
access networks
Types of access
networks:
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Residential access
Company access
Mobile access
Types of physical media
technologies for access
networks:
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Fiber
Coaxial cable
Twisted-pair telephone
wire
Radio spectrum
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Access Network
Access Network: Residential Access
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Connects home end systems to the network edge
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Means of residential access: dialup, DSL, Cable, etc.
Dial-up modem
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Typically, through an ISP
End hosts are PCs
AKA last mile
Uses POTS line  twisted pair copper wire
Calls ISP’s number
Max. data rate: 56 Kbps
Phone line is tied up when connected to ISP
Digital Subscriber Line (DSL)
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Does not tie up the phone line
Uses existing twisted-pair line
Asymmetric upstream and downstream data rates
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Downstream: 384 Kb/s—1.5 Mb/s
Upstream: 128—256 Kb/s
Hybrid Fiber Coaxial (HFC) Cable
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Utilizes distribution network of video broadcast cable
Cable modem uses two channels for data transmission
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Shared among subscribers
10 Base-T Ethernet port
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LAN access
LAN access
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Company/university local area network (LAN) connects end system to
edge router
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Ethernet:
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Shared or dedicated cable connects end system and router
10 Mbs, 100Mbps, Gigabit Ethernet
Deployment: institutions, home LANs soon
LANs: Link layer (chapter 5)
Wireless Access Networks
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Shared wireless access network connects mobile end system to router at
a base station
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Wireless LANs:
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Laptops, PDAs, etc.
Radio spectrum replaces wire
Wireless LANs are based on IEEE 802.11 b standard (11 Mbps)
Wider-area wireless access
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CDPD (Cellular Digital Packet Data): wireless access to ISP router via cellular
network
Third Generation (3G) wireless: packet-switched wide-area Internet access at
384 Kbps
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Example 1
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How long will it take to send a file of 640,000 bits from
host A to host B over a circuit-switched network.
Suppose all links in the network are TDM with:
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24 slots and
have a bit rate of 1.536Mbps
It takes 500 msec to establish an end-to-end circuit before
host A begins transmitting to B
How long will it take to send file?
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Example 1


How long will it take to send a file of 640,000 bits from
host A to host B over a circuit-switched network.
Suppose all links in the network are TDM with:
–
–






24 slots and
have a bit rate of 1.536Mbps
It takes 500 msec to establish an end-to-end circuit before
host A begins transmitting to B
How long will it take to send file?
Transmission rate for each circuit = 1.536 Mbps / 24 = 64 Kbps
Time to send 640 Kbits file = (640000 bits)/(64 Kbits/sec) = 10
seconds
Including circuit setup overhead, time to send file is 10.5
seconds
This calculation is independent of the # of end-to-end links and
does not include propagation delays
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Example 2
Packet Switching:
 Two forwarding mechanisms:
–
–

No segmentation  message switching
With segmentationpipelining
Example: 7.5 million bits message sent over 3 links, each
of 1.5 Mbps
–
–
Time required without segmentation = (7.5/1.5)x3=15 sec
Now segment packet into 5000 chunks each of 1500 bits


Time for whole packet = 5.002 sec
Pipelining results in reduction of delays as all links are
being utilized simultaneously
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Delay in Packet-Switched networks
Transmission delay:
 R=link bandwidth (bps)
 L=packet length (bits)
 Time to send bits into link = L/R
Propagation delay:
 d = length of physical link
 s = propagation speed in medium (~2x108 m/sec)
 Propagation delay = d/s
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Example 3
Packet Switching Calculation of delay:
 A packet of L bits
 Q links between source and destination hosts
 Each link has a data rate of R bits/sec
 Assume:
–
–
–

No queuing delays
No end-to-end propagation delays
No connection establishment is required
How long it takes to send this L bit packet from source to
destination?
–
Time to traverse the first link from source host: L/R seconds

–
Q-1 more such links are traversed before reaching destination
Thus, total delay: QL/R seconds  more delay for larger
packets
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Chapter 3 – Protocols & the TCP/IP
Suite
Class 1
57
Protocols & the TCP/IP Suite
The Need for a Protocol Architecture

Communication between a set of networked systems can
involve a very complex set of procedures

Example tasks for file transfer:
–
–
–
–
–

Communication link setup
Ensure the receiver is ready to accept data
Make sure the file management application at the receiver
is prepared to receive and store the file
Do file translation if necessary
Confirm delivery & check for errors
Networking protocols use the concept of modularity well
known in the software development arena
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Protocols & the TCP/IP Suite
The Need for a Protocol Architecture

In Networking protocol architectures, the modules are
arranged in a vertical stack
–
–
–

Each layer performs a distinct & essential set of tasks; more
‘primitive’ tasks are usually found in lower layers (‘closer’ to
the transmission medium)
Layers should be defined so changes in one layer do not
necessitate changes in the other layers
It takes at least two systems to communicate across a
network and each of these systems need the same layers
The peer layers on each system communicate with each
other; the set of rules governing it is known as a protocol
–
Syntax
Semantics
–
Timing
–
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Protocols & the TCP/IP Suite
The TCP/IP Protocol Architecture


The TCP/IP protocol suite is a large collection of public
standards approved by the IAB (IETF) and used as the
foundation for the Internet and similar private networks
Communication across a network using TCP/IP protocols
involves two general steps:
–
–

Getting the data across the network to the destination systems
Getting the data within the destination system to the right
application
Because of layering & the general steps above, the TCP/IP
protocol suite was designed with five layers (lowest to
highest):
–
Physical Layer: the physical interface between the network and
the attached system; covers the nature of the data signals,
characteristics of the transmission medium, the data rate, etc.
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Protocols & the TCP/IP Suite
The TCP/IP Layers

Network Access Layer: specifies how data is exchanged
between the attached system and the network; will include
addressing, framing, and other features such as
prioritization
–
–

Details of this layer depends on the physical layer; separating
this layer from higher layer functions allows higher layers to
be used over a wide range of network technologies
Concerned with delivering data across a single network only
Internet Layer: specifies how data can be routed across
multiple networks
–
–
–
All devices across an internet must share a common
internetworking layer to relay the data
Routers are the devices responsible for relaying data in an
internet
A global address space is an essential feature of this layer
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Protocols & the TCP/IP Suite
The TCP/IP Layers

Transport Layer: specifies a set of end-to-end services
usually common to a number of applications
communicating across an internet (error-free, sequenced
data delivery, etc.)
–
–
–

Currently there are two transport layer specifications in the
TCP/IP suite: the Transmission Control Protocol (TCP) and
the User Datagram Protocol (UDP)
TCP provides a reliable connection-oriented transport service
UDP provides a low overhead transport service with no
payload error checking, flow control, or sequencing
Application Layer: specifies the functionality of the
application itself (file transfer, remote terminal access,
etc.)
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Protocols & the TCP/IP Suite
The Operation of TCP & IP



For successful communication across an internet, each
system must have at least one globally unique address
Also, each host process needs a locally unique address
An example TCP/IP based data transfer [Figure 3.1]
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Protocols & the TCP/IP Suite
The Operation of TCP & IP

The key to operation of the protocol stack is encapsulation
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Protocols & the TCP/IP Suite
Examples of TCP/IP Applications

Electronic Mail relies on the Simple Mail Transfer Protocol
(SMTP) – this covers the addressing and delivery of messages;
other standards cover e-mail message format

File Transfer functionality relies on the File Transfer Protocol
(FTP), which provides an authenticated means for accessing and
transferring files to and from a remote system

Remote Terminal Access functionality relies on the TELNET
protocol; it emulates a variety a hardwired terminals over a
network connection

Other important TCP/IP Applications include the World Wide
Web (HTTP or the Hypertext Transfer Protocol), Network News
(NNTP or the Network News Transfer Protocol), and Directory
Services (LDAP or the Lightweight Directory Access Protocol)
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Protocols & the TCP/IP Suite
The OSI Protocol Architecture


The ISO (an international standards body) has also
developed a network protocol reference standard called
the OSI model
While useful to know and important in the context of
some international networks, the OSI model has not
flourished for two primary reasons:
–
–
The TCP/IP have matured and equipment using these
protocols were widely adopted before the OSI model was
finished
The OSI model and standards developed using it tend to be
very complex, making them harder to implement and
operate
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Protocols & the TCP/IP Suite
The OSI Protocol Architecture

The OSI model consists of seven layers (from bottom up):
–
–
–
–
–
–
–
Physical: concerned with the transmission and signaling across
the physical media (same as TCP/IP model)
Data Link: provides reliable transfer on a physical link by
formatting data in frames; providing timing, error, & flow control
Network: provides a universal switching/routing layer to insulate
upper layers from differing data link & physical layers
Transport: provides reliable, transparent end-to-end delivery of
data; may also provide end-to-end error recovery & flow control
Session: establishes, manages, and terminates connections
between communicating applications
Presentation: specifies how data should be represented between
communicating applications
Application: provides user access to networked resources
through a specific functional program
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Protocols & the TCP/IP Suite
Internetworking


It is very common for an organization to have different
varieties of LANs as well as geographically dispersed
networks
A quick review of Internetworking Terms
–
–
–
–
–
–
–
Communication Network
Internet (internet)
Intranet
End System
Intermediate System
Bridge
Router
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Protocols & the TCP/IP Suite
Routers


Routers are key pieces of equipment that allow
internetworking across dissimilar networks
Essential functions for a router:
–
–
–

Provide links between physically distinct (and heterogeneous)
networks
Decide when and where to forward packets to attached
networks
Provide these functions in such a way that no modifications
are required to the attached networks
Networking issues routers must deal with:
–
–
–
–
Layer 2 Addressing Schemes
Maximum Packet sizes
Interfaces
Reliability
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Protocols & the TCP/IP Suite
An Internetworking Example [Figure 3.5]
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Protocols & the TCP/IP Suite
Appendix: IP, TCP, and UDP

IP version 4 (IPv4)
–
–
The current version of the network layer protocol used in the
Internet
IPv4 header fields:
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Protocols & the TCP/IP Suite
Appendix: IP version 6 (IPv6)

Next generation version promises a number of improvements:
–
–
–

HUGE address space, with support for a many addressing schemes
Different header structure and options to speed processing
Built-in Quality of Service and security functionality
IPv6 Header fields:
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Protocols & the TCP/IP Suite
Appendix: the Transmission Control
Protocol (TCP)



Provides a sophisticated connection-oriented transport
service to networked applications on an IP network
TCP provides reliable and sequenced streaming delivery of
application-layer data
TCP Header fields:
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Protocols & the TCP/IP Suite
Appendix: the User Datagram Protocol
(UDP)




Provides a basic low-overhead connectionless transport
service to networked applications on an IP network
UDP provides unreliable delivery of application-layer data
in which delivery or duplication of data is not guaranteed
UDP is good for applications that provide their own
enhanced delivery services as well as multicast and
streaming applications
UDP Header fields:
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Homework & Reading
Assignment #1 -- due at class #3 (two weeks)!

Assignment #1
–
–
Stallings Chapter 3: 3.3, 3.5, 3.8
Search on the Web for a manufacturer of Category 7 twisted
pair cabling & document the following:




–

Manufacturer Name
Cable specs: attenuation, NEXT, FEXT paramters
Basic description of the cable’s construction (a diagram helps)
Is the cable sold as part of a structured cabling system? If so,
give a brief description of what components are in the system
Install the OPNet software and complete Lab0 (“Getting
Started”). Answer the questions and also print out and
submit the graphs you generate in the final section of the
2nd lesson (“Comparing Results”).
Reading
–
–
This Class: Stallings Chapters 1 through 3
Next Week: Chapters 4 through 6
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