Transcript Set 1 File

Introduction to Data
Communications and Networking
Chapter 1 (Set 1)
Dr. Ali Maqousi, Dr. Tatiana Balikhina
[email protected] , [email protected]
Department of Computer Networks
Faculty of Information Technology
Petra University
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DATA COMMUNICATIONS
•The term telecommunication means communication
at a distance.
•The word data refers to information presented in
whatever form is agreed upon by the parties creating
and using the data.
•Data communications are the exchange of data
between two devices via some form of transmission
medium such as a wire cable.
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Characteristics that define effectiveness of data
communications
•
•
•
•
Delivery
Accuracy
Timeliness
Jitter
A data communications system must transmit data
to the correct destination in an accurate and timely
manner.
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Five components of data communication
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Components of Data Communication System
• Message is the information (data) to be
communicated (text, numbers, images, audio, and
video).
• Sender is the device that sends the data message
(computer, mobile phone, video camera and so on).
• Receiver is the device that receives the message.
• Transmission medium is the physical path by which
a message travels from sender to receiver (twistedpare, coaxial, fiber-optic cables and radio waves).
• Protocol is an agreement between the
communicating devices on how communication is to
proceed.
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Data flow modes
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Data flow modes
• Simplex as one-way street. Only one of the two
devices on a link can transmit; the other can only
receive.
• Half-duplex, each station can both transmit and
receive, but not at the same time.
• Full-duplex (or duplex), both stations can transmit
and receive simultaneously.
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Networks
• Computer Network is a collection of
devices (nodes) interconnected by a single
technology (transmission medium link).
• Node can be a computer, printer, or any
other device capable of sending and/or
receiving data generated by other nodes on
the network.
• Interconnected computers are two or
more computers that able to exchange
information.
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Networks
Computer network example
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Networks
• Internet is the network of networks (connection of
two or more networks)
•
Intranet is a private business network.
• Most networks use distributed processing, in
which a task is divided among multiple computers.
• Distributed System is a software system built on
top of a network.
• World Wide Web is a distributed system that runs
on top of the Internet.
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Networks criteria
• Performance can be measured in many ways, including:
1)Transit time (time required for a message to travel from one
device to another);
2) Response time (elapsed time between inquiry and response).
Performance is often evaluated by two networking metrics:
Throughput and delay.
To enhance performance we need more throughput and less delay.
• Reliability is measured by :
1) accuracy of delivery;
2)frequency of failure;
3) time it takes a link recover from failure.
• Security include:
1) protecting data from unauthorized access;
2) protecting data from damage;
3) development recovery policies and procedures.
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Benefits of Computer Networks I
Business Applications
- Resource Sharing (printers, scanners,
storage devices, and sharing information,
(client-server model))
- Communication Medium (E-mail)
- Being able to place orders in real time
(Purchase)
- E-Commerce, M-Commerce
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Business Applications of Networks
A network with two clients and one server.
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Benefits of Computer Networks II
Home Network Applications
- Access to remote information (e.g. Google)
- Person to person communication
- Using social networks (e.g. Facebook)
- Interactive entertainment
- E- commerce, M-Commerce
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Network attributes: 1 - Types of connection
•
•
Point-to-point
Multipoint (or multidrop, e.g. broadcasting networks)
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Network attributes: 2 –Topology
The topology of the network is the geometric representation of the
relationship of all the links and nodes to each other.
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Categories of networks
The most common classification of networks is based on its
physical size (scale).
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Local Area Network (LAN)
LAN is a network within a single building or
campus of up to a few kilometres in size.
LANs share the following characteristics:
- their transmission media
- their size (restricted small size)
- their topology (Bus, Ring, Star)
- their setting up cost is low
- Data transfer rate is high (10Mbps,
100Mbps, 10Gbps)
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LAN example
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LAN topologies: Mesh
(1)
A fully connected mesh topology (five devices)
We need n(n-1)/2 duplex-mode point-to-point links to connect n devices
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LAN topologies: Mesh
(2)
Advantages of mesh topology:
•Eliminating traffic problem (each link is dedicated to pair of devices);
•Robustness (break in one line does not lead to break of all network);
•Privacy and security;
•Fault identification and isolation is easy.
Disadvantages of mesh topology:
•Large amount of cabling and I/O ports are required;
•Wiring can be greater than available space;
•It is expensive.
Mesh mainly is used to connect servers of a hybrid topology
network that can include several other topologies.
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LAN topologies: Star
(1)
Star topology uses point-to-point connections (station-hub).
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LAN topologies: Star
(2)
In a Star topology, each station is directly connected to a
central controller – hub.
The hub acts as exchange: device sends data to hub, which
then relays the data to other device.
Advantages of star topology:
•Less expensive than mesh;
•Less cabling;
•Easy maintenance.
Disadvantages of star topology:
•One single point of failure – hub.
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LAN topologies: Star
(3)
An isolated LAN connecting 12 computers to a hub in a
closet
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LAN topologies: Bus
(1)
Bus topology is multipoint. One large cable acts as a backbone
to link all devices in a network.
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LAN topologies: Bus
(2)
In a bus topology, all stations are attached to a liner
transmission medium (bus) through appropriate hardware
interface (tap).
Advantages of bus topology:
•easy to install;
•efficient use of wiring;
Disadvantages of bus topology:
•One single point of failure – backbone cable.
•Difficult maintenance.
IEEE 802.3 (Ethernet) is an example of bus topology.
(IEEE stands for Institute of Electrical and Electronics Engineers)
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LAN topologies: Ring
(1)
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LAN topologies: Ring
(2)
In a Ring topology, each station on the network is connected to
two other stations, forming a loop or ring.
It uses token (signal circulating in a ring) to control transmission.
Advantages of ring topology:
•To add or delete a device requires changing only two
connections.
•Fault isolation is simplified
•No conflict in the transmission of data.
Disadvantages of ring topology:
- if one connection fails, the rest of the network will fail.
To avoid this a dual ring could be used.
IEEE 802.5 ( IBM Token Ring) & FDDI (Fiber Distributed
Data Interface) are examples.
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LAN topologies: Hybrid
A hybrid topology: a star backbone with three bus networks
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Metropolitan Area Network (MAN)
(1)
MAN is a network with a size between a LAN and a
WAN. It normally covers a city.
Examples of a MAN:
1) part of the telephone company network that can provide a
high-speed DSL line to the customer;
2) cable TV network.
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Metropolitan Area Network (MAN)
(2)
MAN based on cable TV
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Wide Area Network (WAN)
(1)
Relation between hosts on LANs and the subnet.
The main differences between WAN and LAN are:
- LAN is fully controlled by the owner whilst the WAN needs
the involvement of another authority like Telephone
Company.
- The transfer rate of LAN is higher than the transfer rate of
WAN.
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Wide Area Network (WAN)
(2)
WAN network spans a large geographical
area, it contains a collection of hosts that are
connected by a communication subnet.
Host is a machine that is used to run user
(i.e., application) program and is owned by the
customers.
Subnet consists of transmission lines and
switching elements, and its job is to carry
messages from host to host.
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Wide Area Network (WAN)
(3)
A stream of packets from sender to receiver.
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Wide Area Network (WAN)
(4)
Subnet is typically owned and operated by a
telephone company or Internet service
provider.
Transmission lines move bits between
machines, they can be made of copper wire,
optical fiber, or even radio links.
Switching elements are specialized
computers that connect three or more
transmission lines and they called Routers.
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Wide Area Network (WAN)
(5)
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Wireless Networks
(1)
- Users have a dream to connect their
notebooks to the network without having to be
plugged into a telephone wall socket.
- To achieve a true mobility there is a need
to use a radio (or infrared) signals for
communication.
Three main categories:
1- System interconnection
2- Wireless LANs
3- Wireless WANs
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Wireless Networks
(a) Bluetooth configuration
(b) Wireless LAN
(2)
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Wireless Networks
(3)
- System interconnection, it is about
interconnecting the components of a computer
using a short-range radio that uses the
master-slave paradigm.
Example:
- Bluetooth is a short-range wireless
network that allows digital components to
connect to a computer by merely being
brought within range.
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Wireless Networks
(4)
- Wireless LAN, it is a system where every
computer has a radio modem and antenna
with which it can communicate with other
systems.
- Wireless LANs are used in small offices,
homes, older office building , conference
rooms and other places.
- IEEE 802.11 (WiFi) is a standard for
wireless LANs.
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Wireless Networks
(5)
Wireless LAN
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Wireless Networks
(6)
- Wireless WAN, it is similar to wireless
LAN system, but with lower bandwidth and is
used in a wide area systems.
- Three generations of Wireless WAN :
the first one was analog and for voice only
the second one was digital and for voice only
the third one is digital and for both voice and
data
- IEEE 802.16 (WiMAX) is a standard for
wireless WANs.
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Home Networks
- Every device in the home will be capable of
communicating with every other device, and all of them
will be accessible over the Internet.
- Examples of devices that are capable of being
networked:
1- Computers (PC, Notebook, PDA)
2-Entertainment (TV, DVD, Camera...)
3-Telecommunications (telephone, intercom...)
4-Appliances (microwave, refrigerator, lights…)
5- Telemetry (smoke alarm, thermostat, babycam…)
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Internetworks
Internetwork or internet is a collection of interconnected networks
that provides universal service among heterogeneous communication
networks.
A heterogeneous
network made of four
WANs and two LANs
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The Internet
(1)
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.
History of Internet:
Beginning in 1969. It was called ARPANET.
TCP/ IP is a protocol suite in the Internet.
The main Internet applications are:
E-mail, News, Remote Login, File transfer, World
Wide Web (WWW)
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The Internet
(2)
Hierarchical organization of the Internet
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The Internet
(3)
- The Internet today is run by private companies, not the
government.
- The national Internet service providers are backbone networks
created and maintained by specialized companies.
- These backbone networks are connected by complex
switching stations (normally run by a third party) called network
access points (NAPs).
- Local ISPs can be connected to a regional or national
service provider.
- Most end users are connected to the local ISPs.
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The Internet
(4)
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Networking Standards
(1)
In this section, we define two widely used terms: protocols and
standards. First, we define protocol, which is synonymous with
rule. Then we discuss standards, which are agreed-upon rules.
A protocol is a set of rules that governs data communication; the
key elements of a protocol are syntax, semantics, and timing.
- The term syntax refers to the structure or format of the data,
meaning the order in which they are presented.
- The word semantics refers to the meaning of each section of bits.
How is a particular pattern to be interpreted, and what action is to be
taken based on that interpretation?
- The term timing refers to two characteristics: when data should be
sent and how fast they can be sent.
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Networking Standards
(2)
Standards are necessary to ensure that products from different
manufacturers can work together as expected.
Advantages of standards
• A standard assures that there will be a large market for a
particular piece of equipment or software.
• A standard allows products from multiple vendors to
communicate.
Disadvantages of standards
•
•
A standard tends to freeze the technology.
There are multiple standards for the same thing.
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Networking Standards
(3)
Standards are developed through the cooperation of standards
creation committees, forums, and government regulatory
agencies.
The ISO, ITU-T, ANSI, IEEE, and IETF are some of the
organizations involved in standards creation.
ISO - International Organization for Standardization
ITU-T - International Telecommunication Union-Telecommunication
Standards Sector
ANSI - American National Standards Institute
IEEE - Institute of Electrical and Electronics Engineers
IETF - Internet Engineering Task Force
- Forums are special-interest groups that quickly
evaluate and standardize new technologies.
- A Request for Comment (RFC) is an idea or concept
that is a originator to an Internet standard.
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Networking Standards
(4)
The 802 working groups. The important ones are
marked with *. The ones marked with  are hibernating.
The one marked with † gave up.
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