1. Introduction.ppt Data Communication slide

1
Welcome to
Data Communication
Data Communication

1.3
1-1 DATA COMMUNICATION
1-1 DATA COMMUNICATION
Data communication is the exchange of data
between two devices via some transmission
medium.
Figure 1.1 Five components of data communication

1.4
Figure 1.2 Data flow (simplex, half-duplex, and full-duplex)
Data Flow: Transmission Modes

1.5
Communication Channel
Communication channel is the link or path between sender and receiver.
Communication Channels are grouped into three basic categories:
 Narrowband
 Voice Band
 Broadband
Narrowband channels range in speed from 45 to 300 bps (bits per
second). This channel is used mainly for telegraph line and low-speed
terminals.
Voice band channels can transmit data at speeds up to 9600 bps. It is
so called because its major application is for ordinary telephone voice
communication.
Broadband/wideband channels are used when large volumes of data is
to be transmitted at high speed. This system provides data transmission
rate of 1 million bps or more. These channels are used for high
speed computer-to-computer data communication.

1.6
Channel Capacity/Bandwidth
Bandwidth defines the volume of signals that can be
transmitted through a communication channel.
So, it defines how much data/information can be
transmitted
in one second. It is usually measured in Hertz (Hz) - cycle
per second.

1.7
1-2 COMPUTER NETWORK
1-2 COMPUTER NETWORK
► A computer network is a set of computers, printers,
and/or other devices capable of sending and
receiving data connected via communication links.
The computer or other devices are often referred as
nodes.

1.8
The Uses of a Computer Network
 Simultaneous access to data

Data files are shared

Shared files stored on a server

Software can be shared
 Shared peripheral device
 Printers and faxes are common shares

Reduces the cost per user

Devices can be connected to the network

Print servers control network printing
 Personal communication

Email

Instantaneous communication

Conferencing

Tele conferencing

Videoconferencing

Audio-conferencing

Data-conferencing
 Voice over IP

Phone communication over network wires

1.9
An overview of Computer
Network

1.10
Network Types
 Local Area Network (LAN)
 Contains printers, servers and computers
 Systems are close to each other
 Contained in one office or building
 Organizations often have several LANS

1.11
Network Types
 Wide Area Networks (WAN)
 Two or more LANs connected
 Over a large geographic area
 Typically use public or leased lines

Phone lines

Satellite
 The Internet is a WAN

1.12
Network Types
 Campus Area Networks (CAN)
 A LAN in one large geographic area
 Resources related to the same organization
 Each department shares the LAN

1.13
Network Types
 Metropolitan Area Network (MAN)
 Large network that connects different
organizations
 Shares regional resources
 A network provider sells time

1.14
How Networks Are Structured
 Server based network
 Node is any network device
 Servers control what the node accesses
 Users gain access by logging in
 Server is the most important computer

1.15
 Client/Server network
 Nodes and servers share data roles
 Nodes are called clients
 Servers are used to control access
 Database software

Access to data controlled by server
 Server is the most important computer

1.16
 Peer to peer networks (P2PN)
 All nodes are equal
 Nodes access resources on other nodes
 Each node controls its own resources
 Most modern OS allow P2PN

1.17
The History about Computer
Network
1966 Terms, packets and packet switching, are coined out.
A project was funded to create an experimental network.
1969 The project evolves into Advanced Research Projects
Agency Network (ARPANET).
The first four nodes of ARPANET were:
– BBN (Bolt, Beranek and Newman), a consulting
company
– SRI (Stanford Research Institute)
– The Univ. of California
– The Univ. of Utah

1.19
Network…
1971 ARPANET has 15 sites, 23 hosts
1972 FTP is outlined in 1972;
E-mail is created in 1972 by Ray Tomlinson of BBN;
Telnet protocol is proposed in his year.
1974 Vinton Cerf, propose the Transmission Control Protocol
(TCP) in the paper, “A Protocol for Packet Network
Internetworking”, which introduce the term Internet.
1977 The first wireless gateway is connected to ARPANET,
which transmits packet over radio waves.
1978 Vinton Cerf, launch the plan for Internet Protocol (IP),
which is proposed as a routing function that is separated
from TCP.
1982 TCP and IP are adopted as the main protocol suite for
ARPANET

1.20
Network…
1983 ARPANET reaches 500 and becomes a truly civilian-based
network, which marks the arrival of Internet
1988 The Internet grows to 60,000 hosts
Europe & North America are linked by fiber-optic cable
Internet Worm, the 1st
internet virus, impacts 10% of the
internet computers
1993 > 2 million hosts, 17 countries in Africa, Asia, …, joined Internet
1999 > 16 million hosts, US law establishes domain names as
property, US Internet backbone reach the speed at 2.5Gbps
2000 IPv6 is used for internet,
The push to implement wireless communication is on.

1.21
Network Topologies
 Topology
 Logical layout of wires and equipment
 Several different types

1.22
Network Topologies
 Bus topology
 Also called linear bus
 One wire connects all
nodes
 Terminator ends the wires
 Advantages

Easy to setup

Small amount of wire
 Disadvantages

Slow

Easy to crash

1.23
Network Topologies
 Star topology

All nodes connect to a hub

Packets sent to hub

Hub sends packet to
destination

Advantages

Easy to setup

One cable can not crash
network
 Disadvantages

One hub crashing downs
entire network

Uses lots of cable

Most common topology

1.24
Network Topologies
 Ring topology
 Nodes connected in a circle
 Tokens used to transmit data

Nodes must wait for token
to send
 Advantages

Time to send data is
known

No data collisions
 Disadvantages

Slow

Lots of cable

1.25
Network Topologies
 Mesh topology
 All computers connected
together
 Internet is a mesh network
 Advantage

Data will always be delivered
 Disadvantages

Lots of cable

Hard to setup

1.26
Tree Topology
Advantage:
When one hub breaks only
stations connected to the
broken hub will be affected.

1.28
Network Hardware
 Network linking devices
 Connect nodes in the network
 Cable runs from node to device
 Crossover cable connects two computers

1.29
Network Hardware
 Hubs
 Center of a star network
 All nodes receive transmitted packets
 Slow and insecure

1.30
Network Hardware
 Switches
 Replacement for hubs
 Only intended node receives transmission
 Fast and secure

1.31
Network Hardware
 Bridge
 Connects two or more LANs together
 Packets sent to remote LAN cross

Other packets do not cross
 Segments the network on MAC addresses

1.32
Network Hardware
 Router
 Connects two or more LANs together
 Packets sent to remote LAN cross
 Network is segmented by IP address
 Connect internal networks to the Internet
 Need configured before installation

1.33
Bridge vs. Router
The purpose of both bridge and router is to connect
two or more LANs of the same type.
Bridge forwards data from one network to all other
networks connected to it with desired and no-desired
networks.
On the other hand, router sends data to the desired
machine on the desired network.
So, in case of bridge, network traffic jam occurs, but
which is not applicable for router.

1.34
Network Hardware
 Gateway
 Connects two dissimilar networks
 Most gateways contained in other devices

1.36
THE INTERNET
THE INTERNET
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.
• Internet is a worldwide system of interconnected computer
networks, which is also called a network of networks
interconnected through regional and national backbone
connections.

1.37
PROTOCOLS AND STANDARDS
PROTOCOLS AND STANDARDS
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.

1.38
Network Protocols
 Language of the network
 Rules of communication
 Error resolution
 Defines collision and collision recovery
 Size of packet
 Naming rules for computers

1.39
Network Protocols
 TCP/IP
 Transmission Control Protocol/Internet Protocol
 Most popular protocol
 Machines assigned a name of 4 numbers

IP address

209.8.166.179 is the White House’s web site
 Dynamic Host Configuration Protocol (DHCP)

Simplifies assignment of IP addresses
 Required for Internet access

1.40
Other Network Protocols
 IPX/SPX
 Internet Packet Exchange/Sequenced Packet
Exchange
 Older protocol
 Associated with Novell Netware
 Replaced by TCP/IP
 NetBEUI
 Network BIOS Extended User Interface
 Used by Windows to name computers
 Transmission details handled by TCP/IP

1.41
ISO’s OSI Reference Model
 ISO:
 International Standards Organization
 A voluntary organization founded in 1946.
 Its members are the national standards
organizations like, ANSI(US), BSI (British), IEEE
(Institute of Electrical and Electronics Engineers)
 OSI Reference Model:
 Open System Interconnected Reference Model

1.44
Modulation and Demodulation
 Modulation – the process of converting analog
signals to digital signals
 Demodulation – the reverse process of modulation,
i.e. converting digital signals back to analog signals.

1.45
Modulation and Demodulation
 Modulation – the process of converting digital signals to
analog signals
 Demodulation – the reverse process of modulation, i.e.
converting analog signals back to digital signals.
Fig. Connection of Computers Using Modems

1. Introduction.ppt Data Communication slide

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