Chapter One
Introduction to data communication
And Networking
1
Outlines
• Model for data communication
• Protocols and architectures used in data communication
OSI and TCP/IP
• Introduction to network devices (switch, hub, router…)
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Introduction
• 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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• A
Network:
A
group
of
devices
that
can
communicate with each other over links.
– It’s a connection between two or more devices.
– Which is connected by a communication links.
• A node can be computer, printer or any other devices
which is capable of sending and receiving information at
each other.
– Each device is called a host.
– Each host has a unique address.
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Components of a data communication system
1. protocol
2. Message
3. Medium
4. Sender
5. Receiver
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Model for data communication
Source
• Generates data to be transmitted
Transmitter
• Converts data into transmittable signals
Transmission System
• Carries data
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Receiver
•Converts received signal into suitable data form
Destination
•Takes incoming data
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Simplified Data Communications Model
Protocols and architectures used in data communication
OSI and TCP/IP
• A protocol is a set of rules or procedures for transmitting
data between electronic devices, such as computers.
• it a set of mutually accepted and implemented rules at
both ends of the communications channel for the proper
exchange of information.
• It is a digital language through which we communicate
with others on the Internet.
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• Rules are defined for each step and process during
communication between two or more computers.
• Networks have to follow these rules to successfully
transmit data.
• Protocols are needed in every field like society, science
& technology, Data Communication, media and etc.
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• In order for computers to exchange information, there
must be a pre-existing agreement as to how the
information will be structured and how each side will
send and receive it.
• Without a protocol, a transmitting computer, for example,
could be sending its data in 8-bit packets while the
receiving computer might expect the data in 16-bit
packets.
• Protocols are established by international or industry
wide organizations.
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• Perhaps the most important computer protocol is OSI
(Open Systems Interconnection), a set of guidelines for
implementing
networking
communications
between
computers.
• Among the most important sets of Internet protocols are
TCP/IP
(Transmission
Control
Protocol/Internet
Protocol), HTTPS (Secure Hypertext Transmission
Protocol), SMTP (Simple Mail Transfer Protocol), and
DNS (Domain Name System).
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Levels of a Protocol
• There are mainly three levels of a protocol, they are as
follows:
• Hardware Level: In this level, the protocol enables the
hardware devices to connect and communicate with each
other for various purposes.
• Software Level: In the software level, the protocol
enables different software to connect and communicate
with each other to work collaboratively.
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• Application Level: In this level, the protocol enables the
application programs to connect and communicate with
each other for various purposes.
• Hence protocols can be implemented at the hardware,
software, and application levels.
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Types of Protocols
• Protocols can be broadly divided into the following two
types:
– Standard Protocols
– Proprietary Protocols
• Standard Protocols:
• A standard protocol is a mandated protocol for all
devices.
– It supports multiple devices and acts as a standard.
– Standard protocols are not vendor-specific
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– i.e. they are not specific to a particular company or
organization.
– They are developed by a group of experts from different
organizations​ .
• These protocols are publicly available, and we need not
pay for them.
• Some of the examples of Standard Protocols are FTP,
DNS, DHCP, SMTP, TELNET, TFTP, etc.
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• FTP(File transfer protocol): is basically used for
transferring files to different networks.
– There may be a mass of files such as text files, multimedia
files, etc.
– This way of file transfer is quicker than other methods.
• SMTP(Simple mail transfer protocol): manages the
transmission and outgoing mail over the internet.
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• Proprietary Protocols​:
– Proprietary protocols are developed by an individual
organization for their specific devices.
– We have to take permission from the organization if we
want to use their protocols.
– It is not a standard protocol and it supports only specific
devices.
– We may have to pay for these protocols.
– Some of the examples of Proprietary Protocols are
IMessage, Apple Talk, etc.
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OSI and TCP/IP
• Open Systems Interconnection (OSI) protocols: are a family
of standards for information exchange.
• They consist of a set of rules that should represent a standard
for physical connections, cabling, data formats, transmission
models.
• These protocols were developed and designed by the
International Organization of Standardization (ISO).
• In 1977 the ISO model was introduced, which consisted of
seven different layers.
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• Each layer of the ISO model has its own protocols and functions.
• The OSI protocol stack was later adapted into the Transmission
Control Protocol (TCP)/ internet protocol (IP) stack.
• TCP/IP helps you to determine how a specific computer should be
connected to the internet and how you can transmit data between
them.
– It helps you to create a virtual network when multiple computer networks
are connected together.
• TCP/IP stands for Transmission Control Protocol/ Internet
Protocol.
– It is specifically designed as a model to offer highly reliable and end-to-end
byte stream over an unreliable internetwork.
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OSI Model Explained
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• The following are the OSI protocols used in the seven
layers of the OSI Model:
• Layer 1, the Physical Layer
– This layer deals with the hardware of networks such as
cabling.
– It defines the mechanical and electrical standards of interface
devices and the types of cables used to transmit digital signals
(e.g. optical fiber, coaxial cable, wireless, etc.).
– The major protocols used by this layer include Bluetooth,
PON, OTN, DSL, IEEE.802.11, IEEE.802.3, L431 and TIA
449.
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•Transmitting individual bits from one node to the next.
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• Layer 2, the Data Link Layer
– This layer receives data from the physical layer and compiles it
into a transform form called framing or frame.
– The principal purpose of this layer is to detect transfer errors by
adding headers to data packets.
– The protocols are used by the Data Link Layer include: ARP,
CSLIP, HDLC, IEEE.802.3, PPP, X-25, SLIP, ATM, SDLS and
PLIP.
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• It is responsible for node-to-node delivery of data.
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• Layer 3, the Network Layer
– This is the most important layer of the OSI model, which
performs real time processing and transfers data from nodes to
nodes.
– Routers and switches are the devices used for this layer that
connects the notes in the network to transmit and control data
flow.
– The network layer assists the following protocols:
– Internet Protocol (IPv4), Internet Protocol (IPv6),
IPX, AppleTalk, ICMP, IPSec and IGMP.
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• Layer 4, the Transport Layer
– The transport layer works on two determined communication
modes: Connection oriented and connectionless.
– This layer transmits data from source to destination node.
– It uses the most important protocols of OSI protocol family,
which are: Transmission Control Protocol (TCP), User
Datagram Protocol (UDP), SPX, Datagram Congestion Control
Protocol (DCCP) and Stream Control Transmission Protocol
(SCTP).
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• Layer 5, the Session Layer
– The session layer creates a session between the source
and the destination nodes and terminates sessions on
completion of the communication process.
– The protocols used are: PPTP, SAP, L2TP and
NetBIOS.
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• Layer 6, the Presentation Layer
– The functions of encryption and decryption are defined on this
layer.
– It ensures that data is transferred in standardized formats by
converting data formats into a format readable by the application
layer.
– The following are the presentation layer protocols: XDR, TLS,
SSL and MIME.
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• Layer 7, the Application Layer
– This layer works at the user end to interact with user
applications.
– QoS (quality of service), file transfer and email are the
major popular services of the application layer.
– A few examples of application layer protocols are the
Hypertext Transfer Protocol (HTTP), File Transfer
Protocol (FTP), Post Office Protocol (POP), Simple
Mail Transfer Protocol (SMTP), and Domain Name
System (DNS).
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Difference between TCP/IP and OSI Model
• Here are some important differences between the OSI
and TCP/IP model:
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Introduction to network devices
• A network is a set of devices (often referred to as
nodes) connected by communication links.
• 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.
• A link can be a cable, air, optical fiber or any
medium which can transport a signal carrying
information.
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• Network devices, or networking hardware, are physical devices that are
required for communication and interaction between hardware on a
computer network.
• Types of network devices
• The common network device are:
– Hub
– Switch
– Router
– Bridge
– Gateway
– Modem
– Repeater
– Access Point
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Switch
• A Switch is a networking device
that has the ability to link
multiple devices together on one
computer network.
• It uses a data link layer to
connect the devices.
• When it comes to switching, we
prefer
the
packet
switching
method to dispatch the data
packet over the web.
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Hub
• A Hub is a networking connector
device that aids in connecting
multiple devices to a single
network.
• It is a common connection point
that is also known as a network
hub.
• It is a physical layer network
device that connects a series of
LANs.
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Router
• A router is a device for computer networking devices that
helps in connecting two or more packet-switched
networks.
• The major role of the router is to perform the two
functions.
• It supports in handling the traffic between the networks
by dispatching data packets, and permits several devices
to use the same internet connection.
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Exercise (Individual)
1. Discuss on the following network devices;
a)
Gateway
b) Bridge
c)
Modem and
d) Repeater
2. Explain the following protocols: HTTP, SMTP, DHCP,
FTP, Telnet, SNMP, SMPP, POP, DNS, PPTP, SAP,
L2TP, NetBIOS, XDR, TLS, SSL and MIME,
Bluetooth, PON, OTN, DSL, IEEE.802.11, IEEE.802.3,
L431 and TIA 449.
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