1. Computer Networks

2. Networking
Computer network
A collection of computing devices connected in
order to communicate and share resources
Connections between computing devices can be
physical using wires or cables or wireless using radio
waves or infrared signals

3. Networking…
Node
Any device on a network
Data transfer rate (bandwidth)
The speed with which data is moved from
one place to another on a network

4. Basic Components
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5. Basic Components…
 Terminals: end user work station
 Telecommunications Channels & Media: Media
over which data are transmitted – coaxial cables,
fiber optics etc.
 Computer: carry out their information processing
assignments. Mainframe host computer/server.
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6. Basic Components…
 Telecommunication Software: controls the
telecommunication activities
 Telecommunication Processors: to enhance data
communication b/w two points – modems,
message switchers, multiplexers, front end
processors
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7. Basic Components…
 Modems: most common type; convert analog signals to
digital and vice versa.
 Message Switchers: device that receives data messages
from terminals, determine their destination and routes
them one by one to the CPU.
 Advantages – reduce long distance transmission costs since only
single line is required
 Multiplexers : collects messages from many senders, puts
them in order & transmits them thru a broadband; allows
simultaneous transmission
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8. Basic Components…
 Concentrator : a smart multiplexer, can be programmed,
more processing capability (used for load balancing)
 Controller : link groups (clusters) of terminals to a
communication channel
 Front-end processors: located near the host computer,
relieves the host computer of some of the communications
tasks, so that it can process other applications requests.
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9. Communications Media
 Channel:
 means by which data is transmitted b/w
sending and receiving devices.
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10. Types of Networks
Local-area network (LAN)
A network that connects a relatively small number of
machines in a relatively close geographical area
Ring topology connects all nodes in a closed loop on
which messages travel in one direction
Star topology centers around one node to which all
others are connected and through which all messages are
sent
Bus topology nodes are connected to a single
communication line that carries messages in both
directions

11. Types of Networks
Ethernet
The industry standard bus technology for
local-area networks

12. Types of Networks
Wide-area network (WAN)
A network that connects local-area networks over a
potentially large geographic distance
Metropolitan-area network (MAN)
The communication infrastructures that have been
developed in and around large cities
Gateway
One particular set up to handle all communication
going between that LAN and other networks

13. Types of Networks
Local-area networks connected across a distance to
create a wide-area network

14. Types of Networks
Internet
A wide area network that spans the planet
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15. Network Protocols
 An agreed-upon format for transmitting
data b/w 2 devices.
 Protocol determines the following
 Type of error checking
 Data compression method
 Message completion indicated by sender
 Message acknowledgement by receiver
 Popular protocols – TCP/IP, HTTP, FTP, SMTP, POP
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16. Network Architecture
 Refer to either h/w, s/w or a combination.
 Classification : -
 Peer-to-peer architecture – each workstation
has equivalent capabilities & responsibilities
 Client/Server architecture – each computer is
either a client or a server.
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17. Packet Transmission/Switching
Packet
A unit of data sent across a network
Router
A network device that directs a packet between networks
toward its final destination
Packet switching
Messages are divided into fixed-sized, numbered packets;
packets are individually routed to their destination, then
reassembled

18. Packet Switching
Messages
sent by
packet
switching
Take a message, break it into three packets, and
simulate this process

19. Hubs
 A hub is the place where data converges
from one or more directions and is
forwarded out in one or more directions.
 Seen in local area networks

20. Switches
 Allow different nodes of a network to
communicate directly with each other.
 Allow several users to send information over
a network at the same time without slowing
each other down using Media Access
Control address (MAC address)

21. TCP/IP
Transmission Control Protocol (TCP)
Software that breaks messages into packets, hands
them off to the IP software for delivery, and then
orders and reassembles the packets at their
destination
Internet Protocol (IP)
Software that deals with the routing of packets
through the maze of interconnected networks to
their final destination
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22. High-Level Protocols
Other protocols build on TCP/IP protocol suite
Simple Mail Transfer Protocol (SMTP) used to specify
transfer of electronic mail
File Transfer Protocol (FTP) allows a user to transfer
files to and from another computer
Telnet used to log onto one computer from another
Hyper Text Transfer Protocol (http) allows exchange
of Web documents
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Which of these have you used?

23. Firewalls- Network Security
Firewall
A gateway machine and its software that protects a
network by filtering the traffic it allows
Access control policy
A set of rules established by an organization that
specify what types of network communication are
permitted and denied
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Have your messages ever been
returned undelivered, blocked by a firewall?

24. Firewalls
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A firewall protecting a LAN