Transcript Side Arrows Background

Computer Communication & Networks
Week # 01
Semester: Spring 2016
Powerpoint Templates
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Course Instructors
Course Instructor 1:
Muhammad Waseem Iqbal (Sec B,C)
Course Instructor 2:
Khizar Hayat (Sec A)
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
Data Communications and
Networking, 5th edition
Author: Behrouz A. Forouzan
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
Textbook: William Stallings,
Data and Computer
Communication, 8th or 9th Edt.

Computer Networks by
Andrew S. Tanenbaum and
David J. Wetherall,
Prentice Hall; 5th Edition
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Course Overview
Grading Criteria:
 Assignments
 Quizzes
 Midterm
 Term Paper/Final Project + Presentation
 Final Exam
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Course Overview
Topics that we are planning to cover:
 Fundamentals of data communications & Networks
 Network Models (System Architecture)
 OSI
 TCP/IP
 Data Transmission Basics
 Digital and analog data/signals
 Transmission impairments
 Digital Transmission
 Analog Transmission
 Modulation schemes
 Data encoding schemes
 Asynchronous and Synchronous transmission
 Transmission Media
 Guided Media
 Unguided Media
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Course Overview
Topics that we are planning to cover:
 Multiplexing
 Spread Spectrum
 Switched and IP Networks
 Circuit Switched Networks
 Packet Switching
 Structure of a Switch
 Data Link Layer
 Nodes, links, services, sub-layers
 Addressing
 Error Detection and Correction
 Data Link Control
 Services (Framing, flow and error control, ...)
 Protocols (HDLC, PPP)
 LAN and Medium Access Control Protocols
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Course Overview
Topics that we are planning to cover:
 Wired (Ethernet) and Wireless LANs, Virtual LANs
 Network Layer
 Services & Performance
 IPV4 Addresses
 Network Layer Protocols (IP, ...)
 Routing Protocols
 Next Generation IP (IPv6)
 Transport Layer Protocols (UDP,TCP, SCTP)
 Application layer protocols
 Wireless LANs
 Quality of Service (QoS)
 Secure communication system (Network Security)
 ISPs
 Lab exercises using packet tracer
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ACKNOWLEDGMENTS
These lecture slides contain material from slides prepared
by Behrouz Forouzan for his book Data Communication
and Networking (4th/5th edition).
These lecture slides updated by Dr. Arshad Ali, Assistant
Professor ,CS Department, The University of Lahore
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Week 1: Course Plan
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Fundamentals of data communications
 Characteristics
 Components
 Data Representation
 Data Flow
 Data Comm. History
Fundamentals of Networks
 Network Criteria
 Physical Structure based on connection and topology
 Network Types (LAN,MAN,WAN,...)
Internet History
Internet Protocols, Standards & Administration
Some common Terminologies
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Data Communication (1)
“Data Communication is the exchange of information from
one entity to the other using a transmission medium”.
As you can clearly notice, the definition of Data
Communication, although simple, leaves many questions
unanswered:
Exchange ??????
Information ?????
Entities ???????
Transmission ????
Medium ????
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Data Communication (2)
 When we communicate, we share information
 Information sharing can be LOCAL or REMOTE
 Between individuals
 LOCAL communication occurs face to face
 REMOTE communication occurs over a long distance
 Telecommunication means communication at a distance:
telephony, telegraph and television
 Data refers to information presented in whatever form is agreed
upon by the parties creating and using the data
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Data Communication (3)
Earlier definition of Data Communication can be easily
modified as:
 Data communications are the exchange of data between two
devices via some form of transmission medium such as a
wire cable
Data Communication System
For Data Communication to occur
The communicating devices must be a part of a communication
system made up of some specific kind of hardware (Physical
equipment) and software (Programs),
This type of a system is known as a “Data Communication System”
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Characteristics of
Data Communication System
 The effectiveness of a data communications system
depends on
Delivery of data to the correct destination
Accuracy: data must be delivered accurately (as it
is)
 Timeliness: data must be delivered on time
Real time transmission of audio and video data
A data communication system must transmit
data to the correct destination in an accurate and
timely manner
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Components Of
Data Communication System (1)
Any system is made up of more than one component. Similarly,
a data communication system is made up of 5 components:
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Components Of
Data Communication System (2)
Sender is the device which sends the data messages. It can be a
computer, workstation, telephone handset etc.
Receiver is the device which receives the data messages. It can be a
computer, workstation, telephone handset etc.
Message is the information to be communicated. Popular forms of
information include text, pictures, audio, video etc.
Medium is the physical path by which a message travels from sender to
receiver. Some examples include twisted-pair wire, coaxial cable, radio
waves etc.
Protocol is a set of rules that governs the data communications. It
represents an agreement between the communicating devices. Without a
protocol, two devices may be connected but not communicating. It
determines what is communicated, how it is communicated and when it is
communicated.
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Data Representation (1)
Forms of Information
 Text (represented as a bit pattern (0s or 1s))
 Different set of bit patterns are designed to represent text symbols
and each set is called a code
 Coding: process of representing symbols
 Unicode currently prevailing system uses 32 bits to represent
a symbol
 ASCII constitutes first 127 characters of Unicode
 Numbers (represented as a bit pattern (0s or 1s))
 A number is directly converted to a number to simplify math
operations
 No code like ASCII is used to represent numbers
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Data Representation (2)
Forms of Information
 Images (also represented by bit patterns)
 Composed of a matrix of pixels (picture elements)
 More pixels, better resolution, more memory
 Each pixel is assigned a bit pattern
 Audio
 recording or broadcasting of sound or music
 Different from text, numbers, or images (by nature )
 Continuous, not discrete
 Video
 recording or broadcasting of a picture or movie
 can either be produced as a continuous entity (e.g., by a TV camera), or
 can be a combination of images, each a discrete entity, arranged to convey
the idea of motion.
 Can be changed to a digital or an analog signal
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Data Flow (1)
Communication between two devices
 Simplex
 One way communication
 One device can only transmit, other can only receive
 Keyboards (introduces inputs), monitor (accepts output)
 Use of entire capacity in one direction
 Half-duplex
 each station can both transmit and receive, but not at the same time
 used in cases where there is no need for communication in both directions
at the same time
 Use of entire capacity for each direction
 Walkie-Talkies
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Data Flow (2)
Communication between two devices
 Full-duplex
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both stations can transmit and receive simultaneously
Sharing of capacity between signals in both directions
Used when communication in both directions is required
Telephone network
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History of Data Communication (1)
Telegraph 1837 by Samuel Morse
 Actually a painter
 Commission by New York City for portrait of
Lafayette in Washington DC
 "Your dear wife is convalescent”
 Next day news of his death
 Left for home and portrait was unfinished
 Burial of his wife before his arrival
 Decided to find means of rapid long distance
communication
 Concept of single wire telegraph
 Morse code ---- language of telegraph
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History of Data Communication (2)
Telephone 1876 Alexander Graham Bell
 Grandfather, father, brother working on
Speech
 Mother and wife were deaf
 So research on hearing and speech led
him experiments with hearing devices
 Award of first US patient for the
telephone (See patent drawing)
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History of Data Communication (3)
1970’s:
 Though development of databases, languages, operating systems, and
hardware was strong from 1950s to 1970s,
 But large-scale data communication systems did not emerge until the
1970s.
 Large-scale data communication systems was stimulated by 3 major
developments
 Large-scale integration of circuits reduced cost and size of
terminals and communication equipment
 New software systems that facilitated the development of data
communication networks
 Competition among providers of transmission facilities reduced the
cost of data circuits
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History of Data Communication (4)
TODAY’S EVERCHANGING & BUSY WORLD
 Today’s fast world demands better, secure and most of all FAST
ways of communication
 Gone are the days when you had to wait a couple of weeks to get a
letter from USA
 Why wait ONE week
 when you can get the information you require in just a split of
a second, using what we know by the name of “Data
Communication”.
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Organization of computer systems is strongly influenced by the
merging of computers and communications
The old model: a single computer serving all of the organization’s
computational needs
replaced by one in which a large number of separate but
interconnected computers do the job
These separate but interconnected computers are called computer
networks
So What is a network?
A network is a set of devices (often referred to as nodes)
connected by communication transmission channels (links) that
allow people to communicate over distances, large and small
In simple words, a network is the interconnection of a set of
devices capable of communication
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A node can be a computer, printer, or any other device capable of
sending and/or receiving data generated by other nodes on the
network
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Device can be a host/end system (such as desk computer, laptop,
cellular phone) or can be a connecting device such as router (connects
a network to other networks), a switch (connects devices together), a
modem (changes the form of data)
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A link is a communications pathway that transfers data from one
device to another.
It can be a cable, air, optical fiber, or any medium which can
transport a signal carrying information
Imagine any link as a line drawn between two points (For
visualization purposes ).
For communication to occur, two devices must be connected in
some way to the same link at the same time.
The Internet and telephone networks span the globe
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Computer Networks: a collection of autonomous computers
interconnected by a single technology
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Two computers are said to be interconnected if they are able to
exchange information
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Networks are usually connected together to make larger networks
(network of networks)
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Internet: the most well-known example of a network of networks
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Network Criteria (1)
Performance
 Measured in many ways
Transit time: amount of time required for a message to
travel from one device to another
Response time: elapsed time between an inquiry and
response
 Depends on a number of factors
Number of users
Type of transmission medium
Hardware capabilities and efficiency of the software
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Network Criteria (2)
Performance
 Evaluated
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in terms of throughput and delay
We need more throughput and less delay (tradeoff)
Send more data to network, increase throughput, but
increases the delay as well due to congestion
Network throughput is the amount of data moved
successfully from one place to another in a given time period,
and
typically measured in bits per second (bps), Mbps or Gbps
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Network Criteria (3)
Reliability is measured by
 the
failure rate of network components (failure
frequency)
 availability (the time taken by a link to recover
from failure), and
 network’s robustness (to cope with errors ---continue operating despite abnormalities)
Security
 Data
protection against corruption/loss of data due
to
Errors
Malicious users
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Physical Structures
1: Based on the Type of Connection
Two possible types of connections
 Point to Point: single transmitter and receiver
◦ Provides dedicated link between two devices
◦ Example: Remote control and TV control system
 Multipoint: multiple recipients of single transmission
◦ More than two specific devices share a single link
◦ Capacity of the channel is shared
◦ Spatially shared capacity: if several can use the link
simultaneously
◦ Temporally shared capacity: If users use the link in turns
(timeshared)
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Types of connections:
point-to-point and multipoint
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Physical Structures
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Physical Topology refers to the way in which a network is
laid out physically
Two or more devices connect to a link and two or more
links form a topology
Topology is geometric representation of the relationship
of all the links and nodes (devices connected to one
another through links)
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A fully connected mesh topology (five devices)
Example: Connection of telephone regional offices
as each regional office needs to be connected with
every other regional office
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A star topology connecting four stations
Used in local area networks
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A bus topology connecting three stations
- Nodes are connected to the bus cable by drop lines and taps
- Was used in early LANs
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A ring topology connecting six stations
was used in LANs (Ethernet) introduced by IBM
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A hybrid topology:
a star backbone with three bus networks
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Categories of Networks
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Local Area Networks (LANs)
Short distances
Designed to provide local interconnectivity
Wide Area Networks (WANs)
Long distances
Provide connectivity over large areas
Metropolitan Area Networks (MANs)
Provide connectivity over areas such as a city, a campus
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Local Area Networks (LAN)
 a privately owned network that operates within and nearby
a single building like a home, office, campus
 widely used to share resources such as printers
Enterprise LAN: when used by companies
 Wireless LAN standard: IEEE 802.11 (Known as WiFi)
Speed anywhere from 11 to 100 Mbps
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Local Area Networks (LAN)
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Wired LAN use different transmission technologies like Copper wires,
optical fiber
Restricted in size
Speed from 100 Mbps to 1 Gbps, Low delay (ms,ns)
Most common wired LAN standard: 802.3 (called Ethernet)
Each computer speaks the Ethernet protocol and connects to a box
called a switch with a point-to-point link
switches can be plugged into each other using their ports to build
larger networks
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An isolated LAN connecting
12 computers to a hub in a closet
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Wide Area Networks (WAN)
 may cover continent or planet
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most communication links are point-to-point
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usually organized as a “subnet” to which hosts have access
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switching elements are generically referred to as routers
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Machines connected to any LAN are called hosts
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Communication subnet or just subnet connects the rest
of the network and hosts
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Wide Area Networks (WAN): Communication architecture
 Transmission lines: transmission media
Move bits between hosts
Copper wire, optical fiber or radio links
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Switching elements (specialized computers)
Connect two or more transmission lines
◦ Provide message forwarding
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Wide Area Networks (WAN):
 A stream of packets from sender to receiver
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WANs: a switched WAN and
a point-to-point WAN
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An internetwork made of
two LANs and one point-to-point
WAN
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A heterogeneous network made of
four WANs and two LANs
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Metropolitan Area Networks (MAN)
 a network with a size between a LAN and a WAN
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normally covers the area inside a town or a city
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designed for customers who need a high-speed
connectivity, normally to the Internet, and have endpoints
spread over a city or part of city
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usually based on LAN technology
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Metropolitan Area Networks (MAN)
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Example: cable TV-based network that originally was designed for
cable TV, but today can also be used for high-speed data connection to
the Internet
both television signals and Internet being fed into the centralized
cable head-end for subsequent distribution to people’s homes
Another example: WiMAX (standardized as IEEE 802.16)
 30 to 40 Mbps data rates, with updates to 1 Gbps
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THE INTERNET
An internet is two or more networks that can communicate
with each other . The most notable internet is called
Internet (composed of thousands of interconnected
networks)
 The Internet has revolutionized many aspects of our daily
lives.
 It has affected the way we do business as well as the way we
spend our leisure time.
 The Internet is a communication system that has brought a
wealth of information to our fingertips and organized it for
our use.
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INTERNET HISTORY
Stand-alone computers till mid 60s were unable to
communicate with one another
ARPA (in DoD) was interested to find a way to connect
computer to facilitate their funded researchers for sharing
findings
Reducing cost and efforts
In 1967 in a small meeting, ARPA presented its idea for
ARPANET (a small network of connected computers)
1969: ARPANET’s idea became reality when four nodes at
four different Universities were connected
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INTERNET HISTORY
Main idea of TCP was given by Vint Cerf and Bob Kahn
in 1972
Soon after, TCP was divided into two protocols, TCP
and IP commonly known as TCP/IP
1983: authorities abolished the original ARPANET
protocol and TCP/IP became official protocol for
ARPANET
Running of TCP/IP is necessary if one wants to use the
Internet to access a computer on a different network
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INTERNET TODAY
The Internet today is made up of many wide- and local-area
networks joined by connecting devices and switching stations.
It is difficult to give an accurate representation of the Internet
Internet users use the services of ISPs (International,
national, regional, local)
Run by private companies instead of Govts.
The Internet today is a set of pier that provide services to the
whole world
Invention of new applications has made the Internet so
popular
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INTERNET TODAY
World Wide Web: Invented in 1990s has added the commercial
application to the Internet
 Multimedia: advances in multimedia applications such as VoIP
(telephony), video over IP (skype), view sharing (YouTube)
Has increased number of users and amount of time each user
spends on the network
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Hierarchical organization of the Internet
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Protocols, Standards and Administration
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Protocols
◦ a set of rules that govern data communications. It determines what is
communicated, how it is communicated and when it is communicated

The key elements of a protocol are
◦ Syntax
 Structure or format of the data
 Indicates how to read the bits
◦ Semantics
 Interprets the meaning of the bits
 Knows which fields define what action
◦ Timing
 When data should be sent and what
 Speed at which data should be sent or speed at which it is being
received
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Protocols, Standards and Administration
Standards are essential
 in creating and maintaining an open and competitive market for
equipment manufacturers and
 in guaranteeing national and international interoperability of
data and telecommunications technology and processes
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Standards provide guidelines to manufacturers, vendors,
government agencies, and other service providers to ensure the
kind of interconnectivity necessary in today's marketplace and in
international communications
Data communication standards
◦ De facto: by fact or convention (not approved but adopted)
◦ De jure: by law or regulation
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Protocols, Standards and Administration
Standards Organizations
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Standards are developed through the cooperation of
◦ standards creation committees (ISO, ITU-T, CCIIT, ANSI, IEEE,
EIA)
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Forums (work with universities and users to test, evaluate, and standardize
new technologies and present their conclusions to the standard bodies): , and
government regulatory agencies (FCC in USA)
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Protocols, Standards and Administration
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An Internet standard is a thoroughly tested specification and
formalized regulation that must be followed
◦ specification attains Internet standard status through a strict procedure
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A specification begins as an Internet draft, a working document (a
work in progress) with no official status and a 6-month lifetime.
Upon recommendation from the Internet authorities, a draft may be
published as a Request for Comment (RFC)
Each RFC is edited, assigned a number, and made available to all
interested parties.
RFCs go through maturity levels and are categorized according to
their requirement level.
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Protocols, Standards and Administration
RFCs maturity levels
 Proposed standard
 Draft standard
 Internet standard
 Historic
 Experimental
 Informational
RFCs requirement levels
 Required
 Recommended
 Elective
 Limited use
 Not recommended
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Protocols, Standards and Administration
RFCs maturity levels
 Proposed standard: stable and well understood specification; of
sufficient interest to the research community; tested and
implemented by several different groups
 Draft standard status from proposed; after at least two successful
independent and interoperable implementations
 Internet standard status is after successful demonstrations of
successful implementation
 Historic significant from historic perspective; either superseded or
never passed the necessary maturity levels
 Experimental describes work related to an experimental situation
that does not affect the operation the Internet
 Informational contains general, historical, or tutorial information
related to the Internet
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Protocols, Standards and Administration
RFCs requirement levels
 Required: if it must be implemented by all Internet systems
to achieve minimum conformance; like IP and ICMP
 Recommended: not required for minimum conformance;
recommended because of its usefulness; like FTP and
TELENET
 Elective: A system can use it for its own benefit (neither
required not recommended)
 Limited use: to be used only in limited situations; most RFCs
fall under this category
 Not recommended: inappropriate for general use; normally a
deprecated historic RFC falls under this category
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Protocols, Standards and Administration
Internet Administration
 Internet Society (ISOC): provide support for the Internet
standards process and promotes research and other scholarly
activities related to the Internet
 Internet Architecture Board (IAB): technical advisor to the
IOSC with main purpose to oversee the continuing development
of TCP/IP and serves in a technical advisory capacity to
research members. Its two primary components
◦ Internet Engineering Task Force (IETF): forum of working groups
collected into areas and each area concentrates on a specific topic like
applications, protocols, routing, security, network management etc
◦ Internet Research Task Force (IRTF): forum of working groups
which focuses on long-term research topics related to Internet
protocols, applications, architectures and technology
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