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Lecturer: Nguyễn Thị Thanh Vân – FIT - HCMUTE

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History of computer network
Computer network
Network topology
Network protocol
Network Components
Internet
Packet-Switched Networks problems:
o Delay, Loss, and Throughput in

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Protocol Layers and Their Service Models
OSI model

TCP/IP model

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1960’s – “How can we transmit bits across a
communication medium efficiently and reliably?”
1970’s – “How can we transmit packets across a
communication medium efficiently and reliably?”
1980’s – “How can we provide communication services
across a series of interconnected networks?
1990’s – “How can we provide high-speed, broadband
communication services to support high-performance
computing and multimedia applications across the globe?”
2000's – What do you think will dominate in the next 10
years?


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Sender

Input
Information
m

Input
Device

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Input data g
or signal
g(t)

Transmitter

Source System
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Transmitted
signal
s(t)


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Received
signal
r(t)

Output data g’
or signal
g’(t)
’

Transmission
medium

Receiver

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Output
Device

Output
Information
m’

Receiver

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Destination System
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Data encoding
Signal generation: electro-magnetic signals to be transmitted over a
transmission medium
Synchronization: timing of signals between the transmitter and receiver
Error detection and correction: ensuring that transmission errors are
detected and corrected
Flow control: ensuring that the source does not overwhelm the
destination by sending data faster than the receiver can handle
Multiplexing: make more efficient use of a transmission facility. This

technique is used at different levels of communication
Addressing: indicating the identity of the intended destination
Routing: selecting appropriate paths for data being transmitted
Message formatting: conforming to the appropriate format
Security: ensuring secure message transmission
Systems management

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communication network is a collection of devices connected by some
communications media and Network Architecture (topology and protocol)
o Example devices are:
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mainframes, minicomputers, supercomputers

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workstations, personal computers

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printers, disk servers, robots

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X-terminals

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Gateways, switches, routers, bridges

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Cellular phone, Pager, TRS

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Refrigerator, Television, Video Tape Recorder

o Communications Media

• twisted pairs, coaxial cables, fiber optics
• line-of-sight transmission: lasers, infra-red, microwave, radio
• satellite links
• Power line
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Computer Communication – the exchange of information
between computers for the purpose of cooperative action
Computer Network – a collection of computers
interconnected via a communication network

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Transportation Network
 Vehicles/People
 Street address
 Intersection
 Street, highway, path
 Traffic jam
 Stop and go traffic light
 Taking alternative path
 Collision
 HOV lane
 Following a route to school
 …

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Computer Network
Packets/Payload
IP address
Bridge/router
Link/broadband/path
Network congestion

Flow control
Alternative route
Collision of packets
Flow Priority
Routing algorithm
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Resource Sharing
o Hardware (computing resources, disks, printers)
o Software (application software)

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Information Sharing
o Easy accessibility from anywhere (files, databases)
o Search Capability (WWW)

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Communication
o Email
o Message broadcast


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Remote computing

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Distributed processing (GRID Computing)

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History of computer network
Computer network
Network topology
Network protocol
Network Components
Internet
Packet-Switched Networks problems:
o Delay, Loss, and Throughput in


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Protocol Layers and Their Service Models
OSI model
TCP/IP model

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The network topology defines the way in which devices are
connected.

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All networked nodes are interconnected, peer to peer, using

a single, open-ended cable
Both ends of the bus must be terminated with a terminating
resistor to prevent signal bounce

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Advantage:
o Easy to implement and extend
o Well suited for temporary networks that must be set up in a hurry

o Typically the least cheapest topology to implement
o Failure of one station does not affect others

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Disadvantage
o Difficult to administer/troubleshoot
o Limited cable length and number of stations
o A cable break can disable the entire network; no redundancy
o Maintenance costs may be higher in the long run
o Performance degrades as additional computers are added


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A frame travels around the ring, stopping at each node. If a
node wants to transmit data, it adds the data as well as the
destination address to the frame.

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The frame then continues around the ring until it finds the
destination node, which takes the data out of the frame.
o Single ring – All the devices on the network share a single cable
o Dual ring – The dual ring topology allows data to be sent in both

directions.

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Advantage
o This type of network topology is very organized
o Performance is better than that of Bus topology

o No need for network server to control the connectivity between

workstations
o Additional components do not affect the performance of network
o Each computer has equal access to resources

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Disadvantage:
o Each packet of data must pass through all the computers between

source and destination, slower than star topology
o If one workstation or port goes down, the entire network gets affected
o Network is highly dependent on the wire which connects different

components
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Have connections to networked devices that “radiate” out

form a common point
Each device can access the media independently
Have become the dominant topology type in contemporary
LANs (replace buses and rings)
Extended start

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Advantage:
o Compare to bus: gives far much better performance
o Easy to connect new nodes or devices

o Centralized management.
o Failure of one node or link doesn’t affect the rest of network

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Disadvantage:
o If central device fails whole network goes down
o The use of hub, a router or a switch as central device increases the


overall cost of the network
o Performance and as well number of nodes which can be added in

such topology is depended on capacity of central device

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Partial Mesh Topology :
o In this topology some of the systems are connected in the same

fashion as mesh topology but some devices are only connected to
two or three devices.
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Full Mesh Topology :
o Each and every nodes or devices are connected to each

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Advantages
o Each connection can carry its own data load.
o It is robust.

o Fault is diagnosed easily.
o Provides security and privacy.

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Disadvantages:
o Installation and configuration is difficult.
o Cabling cost is more.
o Bulk wiring is required.

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Many different types of topologies which is a mixture of two
or more topologies.

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A protocol defines the format and the order of messages
exchanged between two or more communicating entities, as
well as the actions taken on the transmission and/or receipt
of a message or other event

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Physical Media
o Cable,

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Interconnecting Devices
o Router, switch, hub…

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Computers
o Server, client


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Networking Software
o Protocol, Network OS

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Applications
o Mail, web….

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Depending on the size and range of the computer network,
you can differentiate between different network
dimensions.
The most important network types include:
o Personal Area Networks (PAN): modern devices are integrated into a
o
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o
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network
Local Area Networks (LAN): more than 1 computer is to be connected
Metropolitan Area Networks (MAN): connects several LAN
Wide Area Networks (WAN): extend MAN across large geographic
areas, such as countries or continents
Global Area Networks (GAN): Internet

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History of computer network
Computer network
Network topology
Network protocol
Network Components
Internet
Packet-Switched Networks problems:
o Delay, Loss, and Throughput in




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Protocol Layers and Their Service Models
OSI model
TCP/IP model

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Introduction to Internet
The Network Edge
The Network core
o Switching Techniques: Circuit and Packet

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1961–1972: Early packet-switching principles
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1961: Kleinrock – queueing
theory shows effectiveness
of packet-switching
1964: Baran – packetswitching in military nets
1967: ARPAnet conceived by
Advanced Research Projects
Agency
1969: First ARPAnet node
operational

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1972:
o ARPAnet demonstrated

publicly
o NCP (Network Control
Protocol) first host-host
protocol
o First e-mail program
o ARPAnet has 15 nodes

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1972–1980: Internetworking, new and proprietary nets
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1970: ALOHAnet satellite
network in Hawaii
1973: Metcalfe’s PhD thesis
proposes Ethernet
1974: Cerf and Kahn architecture for interconnecting
networks
late 70s: Proprietary
architectures: DECnet, SNA,
XNA
late 70s: Switching fixed length
packets (ATM precursor)

1979: ARPAnet has 200 nodes

Cerf and Kahn’s internetworking
principles:
o Minimalism, autonomy - no
internal changes required to
interconnect networks
o Best effort service model
o Stateless routers
o Decentralized control
Define today’s Internet
architecture

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1980–1990: New protocols, a proliferation of networks
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1983: Deployment of TCP/IP
1982: SMTP e-mail protocol

defined
1983: DNS defined for
name-to-IP-address
translation
1985: FTP protocol defined
1988: TCP congestion
control

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New national networks:
Csnet, BITnet, NSFnet,
Minitel
100,000 hosts connected
to confederation of
networks

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1990s: Commercialization, the WWW
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Early 1990’s: ARPAnet
decommissioned
1991: NSF lifts restrictions on

commercial use of NSFnet
(decommissioned, 1995)
Early 1990s: WWW
o hypertext [Bush 1945, Nelson
1960s]
o HTML, http: Berners-Lee
o 1994: Mosaic, later Netscape
o Late 1990s:
commercialization of the
WWW

Late 1990’s:
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Est. 50 million computers
on Internet
Est. 100 million+ users
Backbone links running
at 1 Gbps

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Scale

 How

to manage such a large system,
 growing rapidly and uncontrollably,
 consisting of heterogeneous devices,
 managed by multiple entities
 having limited resources
 Let’s

take things one at a time
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PC

o

Server

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of connected devices:
Hosts = end systems
Running network apps

Wireless
laptop

Communication links
Smartphone
– Fiber, copper, radio,
satellite
– Transmission rate:
Wireless
bandwidth
links
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Wired
links

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Router

Mobile network

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Global ISP

Home
network

Regional ISP

Enterprise
network

Packet switches: forward packets
(chunks of data)
– Routers and switches

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Devices connected to the Internet are often referred to as
end systems.
End systems are also referred to as hosts because they
host (that is, run) application programs
They are referred to as end systems because they sit at the
edge of the Internet,


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Network:
o Mobile
o Home

o Enterprise

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The network that
physically connects an
end system to the first
(edge router) on a path
from the end system to
any other distant end
system


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Home Access: DSL, Cable, FTTH, Dial-Up, Satellite

DSL

FTTH
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Access in the Enterprise (and the Home): Ethernet and WiFi

Ethernet

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Access in the Enterprise (and the Home): Ethernet and WiFi

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the mesh of packet switches and links that interconnects the
Internet’s end systems

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Network Structure 1
o interconnects all of the access ISPs with a single global transit ISP - a

network of routers and communication links that not only spans the
globe, but also has at least one router near each of the hundreds of
thousands of access ISPs
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Network Structure 2,
o consists of the hundreds of thousands of access ISPs and multiple global

transit ISPs (the top tier and access ISPs at the bottom tier)
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Network Structure 3
o multi-tier hierarchy – Internet
o Add more points of presence (PoPs) - group of routers in the provider’s

network
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Network Structure 4
o ISPs, regional ISPs, tier-1 ISPs, PoPs, multi-homing, peering, and IXPs

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Network Structure 5
o Network Structure 4 by adding content provider networks

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The switching technique will decide the best route for data
transmission.

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Circuit Switching

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Packet Switching

Message Switching

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