Internet Technologies

1 – Internet and other

Networks
Content
 What is Internet and the World Wide Web
 Internet usage and statistics
 Introduction to computer networks
 Distributed systems
 Client-Server Architecture
 Usage of computer networks
 LAN, MAN and WAN
 Internetworks
 ARPANET
 NSFNET
 Internet Architecture
What is the Internet?
 WWW
 Video conferencing
 ftp
 telnet
 Email
 Instant messaging
 …

A communication infrastructure
Usefulness is in exchanging information
Internet Usage and Population Statistics

What are the first three continents

for Internet Penetration
(percentage of the population using Internet)?

www.internetworldstats.com. June 2010

Web access by OS and Browser

http://marketshare.hitslink.com
Generation Y, X and Baby Boomers

http://www.pewinternet.org/pdfs/PIP_Generations_2009.pdf
Teens and Gen Y dominant activities
Dominant activities for Gen X and older
Online shopping activities

http://www.pewinternet.org/pdfs/PIP_Online%20Shopping.pdf
People Online in Tourism Market

http://www.newmediatrendwatch.com
Total Sites Across All Domains August 1995 -
November 2007

100,000,000

Internet users
are ~ 2Billions

Much of the growth in sites this year has come from the increasing
number of blogging sites, in particular at Live Spaces, Blogger and
MySpace.
An active web site every 18 users! http://news.netcraft.com
Top Global Web Properties

What are the top

three
Web properties?

with respect to the

number of visitors
Top Web Sites in Italy
Capture - Recapture
 SE1= reported size
of search engine 1
 Q – set of queries
 QSE1 and QSE2 =
pages returned for Q
from two engines
 OVR – overlap of
QSE1 and QSE2

 Estimate of Web size:

 SE1/Web = OVR/QSE2
 Web = (QSE2 * SE1) / OVR
Concentration

in one day (Dec. 97)

Power-law: y=Cx-a
log(y) = log(C) – a log(x)
The simplest network?

The computers have their NIC (Network Interface Card)

with a socket (RJ-45 jack) and a wire (crossover cable)
that goes from one computer to another
Computer Networks
 A computer network is two or more computers
connected together using a telecommunication system
for the purpose of communicating and sharing resources
 Why they are interesting?
 Overcome geographic limits
 Access remote data
 Separate clients and server
 Goal: Universal Communication (any to any)

Network
Distributed Systems
 Internet is not a "computer network" – it is a
network of networks
 The World Wide Web is a distributed system
that runs on top of the Internet
 A distributed system is a collection of
independent computers that appears to its users
as a single coherent system
 Example: in the WWW everything looks like a
document (Web page)
 The distinction between CN and DS lies on the
software not on the hardware.
Client-Server Model
 A network with two clients and one server
 Server: store data on some powerful computer
 Client: access data on server and process locally
on a simpler machine
Client-Server Model (2)
 The client-server model involves requests and replies

 Examples
 e-mail
 Video conferencing
 File downloading
 Instant messaging
 Chatting
Network Applications
 Some forms of e-commerce

G2C C2C P2P

B2B and B2C

Peer-to-Peer Systems
 In peer-to-peer system there are no fixed clients
and servers

 Examples?
 Skype, Kazaa, eMule, exchanging business cards
with bluetooth, …
Transmission Technologies
 Broadcast links
 A single communication channel is shared by
all the machines on the network
 Packets sent by a machine to another brings
the address of the recipient
 Avoid collision in sharing the medium
(channel)
 Point-to-point links
 Many connections between individual pairs of
machines
 A packet is routed from one machine to
another
Networks scale
 Classification of interconnected processors by
scale.
Type of Networks
 PAN: A personal area network is a computer network (CN)
used for communication among computer devices (including
telephones and personal digital assistants) close to one person
 Technologies: USB and Firewire (wired), IrDA and
Bluetooth (wireless)
 LAN: A local area network is a CN covering a small geographic
area, like a home, office, or group of buildings
 Technologies: Ethernet (wired) or Wi-Fi (wireless)
 MAN: Metropolitan Area Networks are large CNs usually
spanning a city
 Technologies: Ethernet (wired) or WiMAX (wireless)
 WAN: Wide Area Network is a CN that covers a broad area,
e.g., cross metropolitan, regional, or national boundaries
 Examples: Internet
 Wireless Technologies: HSDPA, EDGE, GPRS, GSM.
Local Area Networks

 Two broadcast networks: (a) Bus, (b) Ring

 LAN can use cables (Ethernet protocol) or
electromagnetic waves (Wi-Fi) to transmit
information
Wireless Networks
 (a) Bluetooth configuration
 (b) Wireless LAN
Metropolitan Area Networks
 A metropolitan area network based on cable TV
Wide Area Networks
 Host are owned by users
 Subnet is owned by the telephone company or an
Internet service provider
 A subnet is composed by transmission lines
connecting two switching elements (router) – not
the hosts.
Router
Wide Area Networks (2)
 A stream of packets from sender to receiver
 A routers store-and-forward each packet
 The decision of where to send a packet is taken
according to a routing algorithm
Internetworks and Internet
 Many networks exists in the world
 In order to establish a communication between to
"different" networks (hardware e software) there
are gateways
 A collection of interconnected networks is
called internetworks or internet
 The Internet, with a capital "I", is the network of
networks which either use the TCP/IP protocol or
can interact with TCP/IP networks via gateways
(the interpreters)
 The Internet presents these networks as one,
seamless network for its users
 Internet is a particular internetwork
ARPANET
 1950 Department of Defence wanted a command-
and-control network that could survive nuclear war
 At that time, there was only the telephone network

(a) Structure of
the telephone
system –
vulnerable!
(b) Baran’s
proposed
distributed
switching
system.
The original ARPANET
 IMP (Interface Message Processors) are minicomputers
connected by 56-Kbps transmission lines (the grandfathers
of the routers)
 Each IMP is connected with (at least) 2 IMPs (why? is this
enough?)
 A host is connected to a IMP – it sends to it a message that
is split into packets (1008 bits) forwarded independently to
destination.
The Growth of ARPANET

 (a) December 1969, (b) July 1970, (c) March 1971, (d)
April 1972, (e) September 1972
 TCP/IP invented by Cerf and Khan in 1974.
NSFNET
 The NSFNET backbone in 1988
 The computers (fuzzball) where connected with TCP/IP (56
Kbps lines)
 Then to 448Kbps, then 1.5-Mbps, then 45-Mbps (ANSNET –
then sold to America Online)
 Connected to ARPANET trough a link between an IMP and a
fuzzball in the Carnegie Mellon computer room.
History of the Internet
 1969 - RFCs begun by S. Crocker (http://
rfc.sunsite.dk/)
 1972 – First email by Ray Tomlinson & Larry Roberts
 1970’s - TCP by Vint Cerf & Bob Kahn
 Evolved into TCP/IP, and UDP
 1980s – Hardware Explosion (LANs, PCs, and
workstations)
 1983 – Ethernet by Metcalfe
 DNS – Distributed and scalable mechanism for
resolving host names into IP addresses
 UC Berkeley implements TCP/IP into Unix BSD
 1985 – Internet used by researchers and developers.
 1993 – the first Web Browser (NCSA Mosaic)
History of the Internet
 Tim Berners-Lee at CERN in 1989
 Proposal for WWW in 1990
 First web page on November 13, 1990
 Hypertext - Text that contains links to other text.
 Ted Nelson’s Xanadu

 Vannevar Bush’s Memex

(http://www.theatlantic.com/unbound/flashbks/
computer/bushf.htm)
Get more info at:
 W3C http://www.isoc.org/internet/history/
 Bush 1945 – As We May Think

The memex is a
desktop machine,
consisting of:
1) A user interface
2) A repository of
documents
3) A search engine
4) A linking mechanism
5) Memex II can learn
from its experience.
Architecture of the Internet
Internet Service
Provider

Network
Point of Access
Presence Point
Important Terms
 POP (Point of Presence): an access point to the
Internet. It is a physical location that houses servers,
routers, ATM switches and digital/analog call
aggregators
 ISP (Internet Service Provider): business or
organization that provides consumers or businesses
access to the Internet and related services
 Backbone: a large collection of interconnected
commercial, government, academic and other high-
capacity data routes and core routers that carry data
across the countries, continents and oceans of the
world
 NAP (Network Access Point): 4 Network access
points where a packet switches from one backbone to
another.
IP Addresses Network

A line
represent
a connection
between 2 IP
addresses.
The length
represent the
time delay
between the 2
nodes.

http://en.wikipedia.org/wiki/Image:Internet_map_1024.jpg
How to Make the Internet a Lot Faster

 Feb. 2010 - Google announced its plans

to build an experimental fiber network
that would offer gigabit-per-second
broadband speeds to U.S. homes
 This will make possible: transfer of very large files,
streaming high-definition (and possibly 3-D) video,
video conferencing, and gaming
 BUT the transmission control protocol (TCP), the 20-
year-old algorithm that governs most of the traffic
flow over the Internet, doesn't work well at gigabit-
per-second speeds
 How it make sure it isn't losing data cause it to use
too little of the bandwidth available)(Steven Low,
Caltech).
http://www.technologyreview.com/web/24605/