Computer Networks

1. HOW
NETWORKS
TIE
COMPUTERS
TOGETHER
Chapter 17

2. TYPE OF
NETWORK
o LAN: Local Area Network, is a
network that covers a small
geographical area
o WAN: Wide Area Network, is a
network that covers larger
geographical areas
o PAN: is a Personnel Area Network
o HAN: is a Home Area Network
o CAN: Campus Area Network
o MAN: Metropolitan Area Network

3. NETWORK
o Several computers using some network tools with a small
geographical area.
o The purpose of the network is to connect computers together,
exchange data, and provide shared access to hardware, and
software solutions. Where data are saved on the server.
o Usually Network is made of:
o Server: a computer that serves many connected
computers
o Client/Node: one of the connected computer
o Router: a device that establishes a connection
between two networks
o Modem: establish a connection between the Internet
and the network
o Data Packets
o Cable/wire

4. NETWORK IS MADE
OF - (CONT)
o Hub:Hubs connect networking devices
physically together. Hubs use twisted
pair cabling to connect devices. and act
as pathways and transmit the information
regardless if a data packet is destined for
the device connected or not.
o A switch:The switch does ‘filter and
forwarding’., each computer is connected
through a single line. However, the switch
is smarter about where it sends data that
comes in through one of its ports
• Router:A router is a device that routes
packets from one network to another. uses
IP addresses to figure out where to send
packets. It Connect two different network
together.

5. SERVERS
o Different kinds of servers
o File Server:
A specialized computer with multiple hard drives that
connect to PCs using the network (called clients or nodes)
where data are stored and retrieved by the clients.
o Clients:
Computers connected to network connected by the server.
o Internet Server:
Connect to World Wide Web (WWW).
o Print Servers:
Printers connected to everyone on the network used for
printing.

6. HOW COMPUTERS CONNECT TO EACH
OTHER (2)
o Network Interface
o To become part of a network, a
computer/device uses a network interface to
communicate with the local network’s
backbone: High-speed Internet or network
routes.
o Data packets passed in the network through
the backbone
o Many wires/Cables are used in the
backbone The combination of connector,
circuitry, wiring, and wave determines the
network’s bandwidth.

7. . HOW COMPUTERS CONNECT
TO EACH OTHER (1)
o Connection in network can be made through :
o Twisted-Pair Wiring
o The type most used to physically connect a computer to a modem or router.
o In this type of wiring, two conductors of a single circuit are twisted together for
the purposes of improving electromagnetic.
o Coaxial Cable
o Coaxial cable consists of a single copper wire, which is covered by plastic and
braided copper that shields the center wire from electrical disturbances.
o Electrical signal flows through the center conductor; like that used for cable
television.
o Fiber optic cable:
o carries 1 billion bits a second, depending on light, Hair-thin fibers
consist of two layers of pure silica glass covered with a
reflective cladding, like a tunnel lined with mirrors. Varying pulses
carry the data bouncing off the cladding
o Wireless:
o most nodes on modern networks connect to the switch or router
via Wi-Fi radio signals
o infrared light

8. TYPE OF NETWORK AND NETWORK
ARCHITECTURE
o Star Configurations: this is the most common configuration of
computers for a Local Area Network (LAN) in which all nodes are
individually connected to a central connection point, like a router or
a switch.
o Network has two types of relations
o Peer to Peer network where each PC have equal relation or a
peer-to-peer to other devices. This network exists at home or
in small offices with less than 10 employees.
o Client/server network: where there exists a server and
client and the server is in control and responds to the
client’s request

9. HOW DATA TRAVELS BETWEEN
COMPUTERS(1)
• Analogue Data, use carrier wave or carrier signal with
amplitude and frequency. It is a regular or constant waveform.
Whereas the Information wave is all the time irregular.
• Digital data is the most common way for transferring data
using a data packets.
• IP address: Internet protocol addresses is an identifier for a
computer on a TCP/IP network protocol route message
• TCP/IP : transmission control protocol: a collection of methods
to connect servers on the network and to transfer data to a
specific IP address. It is a universal standard

10. HOW WI-FI MAKES INTERNET
PORTABLE
o All Wi-Fi networks use access point (AP):
a network node connected directly to a
wired local area network or to the Internet.
o Wireless nodes, called stations, each
have a transmitter/ receiver
o When a device connects to the network,
it broadcasts a probe request identifying
itself and connect within range.
o Connection can be point to point or
extensions points.

11. HOW DATA TRAVELS BETWEEN
COMPUTERS(2)
How Digital Data Move in Packets?
The organization of data packets varies to match the type of data they contain, and they may be called frames, segments, or blocks. And
data packets include:
• Preamble—Synchronizes the network nodes
• Destination Address—A single PC or all PCs on a network, IP address
• Source Address—The address of the computer from which the packet originated, IP Address
• Data Type—Defines the format used for the data
• Data—The actual data
• CRC—Cyclical Redundancy Check, which is used to spot transmission errors or missing errors : it is an
algorithm that are calculated and compared at the data delivery

12. 4. HOW BLUETOOTH KEEPS DEVICES
CONNECTED
• Bluetooth, named for the
Danish King Harald
Bluetooth, a Scandinavian, is
a standard protocol for
unifying wireless voice and
data communications among
different devices.
• It connects all the equipment
through one universal short-
range radio link.
• It is incorporated in a radio
module, a microchip that can send
both voice and data signals for
about 30 feet/ 10 meters.

13. 4. HOW BLUETOOTH KEEPS DEVICES
CONNECTED
o Bluetooth protocol has a link manager
(LM) software.
o The LM software identifies other
Bluetooth devices, creates links with
them for voice or data, and sends and
receives data.
o After a link is established, Bluetooth
sends data in packets or
correction in case a packet is
dropped.

14. BLUETOOTH
MODES
Standby, or sniff, mode: An unconnected unit periodically
listens for messages every 1.28 seconds.
Page mode: A Bluetooth device makes itself a master by
initiating a link to another device, the slave
Inquiry mode: if the master doesn’t know what other devices
are available, ex: public printers the master transmits an
inquiry on the remaining hop frequencies. This causes
receiving devices to identify themselves and send specific
Park mode :A device wakes up at regular intervals to listen to
the link, synchronize with the rest of the devices,
Hold mode: When a device is turned off to save power, any
other Bluetooth device can wake it up.

15. 4. HOW NFC LETS SMART DEVICES
MAKE CLOSE CALLS
NFC (Near Field Communications):
o Is a short-range wireless technology that allows the exchange of data between
devices.
o It only works with short distances of about four inches at the most.
o NFC uses magnetic fields to communicate.

16. CONT. HOW NFC LETS SMART DEVICES MAKE
CLOSE CALLS
NFC devices can be passive or active:
o A passive NFC contains information that other devices
can read and can’t receive any information other
devices may have to offer.
o Examples: the nametags that unlock doors, and authorize
elevators to stop on a particular floor.
o Active NFC devices can both send and receive
information.
They can decide if another device has the right to
read the information they have, and the ability to grant
or refuse another device to change the information
they have.
Examples:
o using smartphones to exchange business cards or
playlists.

17. o The data in an NFC session could be
intercepted by other devices. For that
reason NFC communications that
involve such info as a credit card or
bank account number are sent along
secure channels and encrypted.
o Users can add antivirus software to
smartphones and store sensitive data
behind a password.
Cont. How NFC Lets Smart Devices Make Close
Calls