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Why learn about Networks ?
TDT4105 - IT Grunnkurs
Recently Cisco Systems conducted a survey in 14 different countries.
Approx. 3000 people completed an online survey during May and June, 2011.
Participants were College Students (age 18–24) and Employees (age 21–29)
Nettverk, Del 1
… about 40% of the students prefer Internet rather than meeting friends.…
…more than 50% indicate they could not live without the Internet…
…about 50% say that Internet is almost as important as food…
The Internet & the World Wide Web
…Internet more important than owning a car.…
How important is it to you ? Would you like to know more about it ?
Bjørn J. Villa
PhD Candidate
Institute for Telematics, NTNU
[email protected]
http://www.cisco.com/en/US/solutions/ns341/ns525/ns537/ns705/ns1120/CCWTR-Chapter1-Report.pdf
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Chapter 2.1
Connecting to the Internet
Topics
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Connecting to the Internet
How does the Internet work ?
The World Wide Web
Email and Other Ways of
Communicating
•  The Online Gold Mine:
Telephony, Multimedia etc
•  The Intrusive Internet
”The lnternet..
...a global, unifying network”
Section 2 of text book ”Using Information Technology”
supplemented with some reflections and examples
© 2010 The McGraw-Hill Companies, Inc.
All rights reserved.
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Connecting to the Internet
Connecting to the Internet
Key terms to undestand
•  Internet History
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Began with 1969’s ARPANET for US Dept. of Defense
62 computers in 1974
500 computers in 1983
28,000 computers in 1987
Early 1990s, multimedia became available on internet
Internet commercially available ~1995
By 2001, the number of Internet hosts surpassed 100 million
Bandwidth is an expression of how much data – text, voice, video and so
on Which can be sent through a communications channel in a given amount
of time
Broadband is a high speed connection that allows “several signals to be
transmitted at once”. In the context of Broadband Internet, this would mean
a connection which allows you to use it for many thing at the same time, or
even to demanding services (e.g. VoD, IPTV)
•  To connect you need
–  An access device (computer)
–  A means of connection (phone line, cable hookup, or wireless)
–  An Internet Service Provider (ISP)
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Connecting to the Internet
Connecting to Internet
•  Data Transmission Speeds
•  Modems
–  Dial up
–  Originally measured in bits per second (bps)
–  8 bits are needed to send one character, such as A or a
–  Currently measured in kilobits, megabits or gigabits per
second (Kbps, Mbps, Gbps)
•  High-speed phone lines
–  ISDN line
–  DSL line
bits ??
...01000110111!
00100111010
11100010001...!
–  Kilo- stands for a thousand, Mega- stands for million,
Giga- stands for billions
–  Mbps connections send 1 million bits per second
–  Gbps connections send 1 billion bits per second
Wired access
•  Cable Modems
–  Coax / Cable TV networks with internet
•  Fiber
–  Optics
•  Satellite
•  Wi-Fi
•  3G/4G/LTE
Wireless access
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Connecting to the Internet
Connecting to the Internet
Kjører
Mobility
CDMA
4G/LTE
Går
UMTS
GSM
GPRS
HSDPA
EDGE
IEEE
802.16e
DECT
Sitter
WLAN
(IEEE 802.11x)
Kobber
...
...
0.1
1
10
Mbit/s 100
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Bandwidth
Statistics for Norway, source: npt.no (Post og Teletilsynet)
Different technologies have different characteristics (bandwidth,
mobility.) but they can all give access to the Internet
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Chapter 2.2
How does the Internet work ?
How Does the Internet Work?
•  The internet consists of thousands of
smaller networks
•  These link educational, commercial,
nonprofit, and military organizations
•  Most are Client/Server networks
–  Client: a computer requesting data or services
–  Server or Host: a central computer supplying
data or services requested of it
© 2010 The McGraw-Hill Companies, Inc.
All rights reserved.
•  No single organization owns or
controls the Internet…..good or bad ?
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How Does the Internet Work?
How Does the Internet Work?
•  The board of trustees of the Internet Society (ISOC)
oversees the standards
•  Internet Corporation for Assigned Names and
Numbers (ICANN) regulates domain names
•  American Registry for Internet Numbers (ARINN)
administers the unique IP addresses for North &
South America, Caribbean, and sub-Saharan Africa
•  Two other organizations administer the unique IP
addresses for Europe (RIPE) and the Asia-Pacific
region
•  And a whole range of other organisations…
•  Customer has an access to an ISP (Internet Service
Provider) through a POP (Point of Presence)
•  A number of ISP networks in each country
•  National and international interconnection point
•  Global Internet Backbone
•  Internet 2
–  Cooperative university/business research project
–  New standards for large-scale higher-speed data transmission
–  Requires state-of-the-art infrastructure
The Internet has historically been driven by Recommendations
and Best Practice, rather than strict Standards and Laws
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How Does the Internet Work?
•  IP Addresses
•  Protocols
–  Every device connected to the internet
has an address
–  Each IP address uniquely identifies that
device
–  The address is four sets of 3-digit
numbers (IPv4) separated by periods
–  The set of rules a computer follows to
electronically transmit data.
–  TCP/IP is the internet protocol
•  Developed in 1978
•  Used for all internet transactions
•  Packets
–  Fixed-length blocks of data for
transmission
–  Data transmissions are broken up into
packets
How Does the Internet Work?
http://www.warriorsofthe.net/
Ericsson Medialab 1999
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Example: 95.160.10.240
Each number is between 0 and 255
Static IP or dynamic IP
Since IPv4 addresses are limited, and
most PCs are not connected a lot of the
time, dynamic addresses are common
•  Each ISP has its own range of
addresses
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How Does the Internet Work?
How Does the Internet Work?
Internet is migrating from IPv4-only to also use
IPv6 around the world. A huge task…
IPv4
“Game Over”
IPv6
Source: http://www.ripe.net
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Chapter 2.3
The World Wide Web
© 2010 The McGraw-Hill Companies, Inc.
All rights reserved.
The World Wide Web
•  Browsers
–  Software for web-surfing
–  Examples: Internet Explorer, Chrome,
Safari, FireFox, Opera..
•  Website
–  The location on a particular computer
that has a unique address
–  Example: www.item.ntnu.no
–  The website could be anywhere – not
necessarily at company headquarters
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The World Wide Web
The World Wide Web
•  Uniform Resource Locator (URL)
•  Domain names
–  A character string that points to a specific piece of information
anywhere on the web
–  A website’s unique address
–  It consists of
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–  Must be unique
–  Identify the website, and (normally) the type of site it is
•  www.whitehouse.gov is NOT the same as www.whitehouse.org
•  .gov means government, .org means professional or nonprofit
organization. We alsos have .com .no .as .tv and so on.
•  A whole range of domain types, not all of which has an explicit
meaning. Some are reserved for business use
•  In Norway, starting this year (06.06.11) – NORID opened up for
registration under the priv.no domain for individuals
•  NORID (www.norid.no) is the official registry for all domains
under .no domain (Norway)
•  But remember, it’s just a name….
The web protocol, http
The domain name of the web server
The directory or folder on that server
The file within the directory, including optional extension
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The World Wide Web
The World Wide Web
•  Search Services
•  HTTP
–  The internet protocol used to access the World Wide Web
•  HTTPS
–  The secure version of HTTP
•  Hypertext Markup Language (HTML)
–  The first language used in writing and publishing web pages
–  The set of tags used to specify document structure,
formatting, and links to other documents on the web
•  Hypertext links connect one web document to
another
–  Organizations that maintain databases accessible
through websites to help you find information on
the internet
–  Examples: portals like Yahoo Search and MSN,
Google, Bing etc
–  Databases are compiled using software programs
called spiders
•  Spiders crawl through the World Wide Web
•  Follow links from one page to another
•  Index the words on that site
–  Search tools
•  Keywords, subjects…
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Chapter 2.4
Email and Other Ways of
Communicating
The World Wide Web
•  Should you trust all information you
find online?
•  There is no central authority that
verifies all internet sites
•  Guidelines to evaluate Web
resources
–  Does the information appear on a
professional site maintained by a
professional organization?
–  Does the website authority appear to be
legitimate?
–  Is the website objective, complete, and
current?
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© 2010 The McGraw-Hill Companies, Inc.
All rights reserved.
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Email & Other Ways of
Communicating over the Net
•  Email client / web-based
•  Instant messaging / RTC
(Real Time Chat)
•  Newsgroups
•  FTP – File Transfer Protocol
•  Email based discussion
groups
•  Social media…
•  ….
Email & Other Ways of
Communicating over the Net
Time spent on Social Networking growing, and is
becoming the main tool of communication
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Chapter 2.5
The Online Gold Mine: Telephony,
Multimedia, Webcasting, Blogs, ECommerce & the Social Web
(=Internet based services)
Email & Other Ways of
Communicating over the Net
•  Independant of which methods used to communicate
you should always enforce some degree of Netiquette
•  Netiquette – appropriate online behavior
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Before you ask a question, consult the FAQ
Avoid flaming
Don’t SHOUT – use all capital letters
Be careful with jokes
Don’t send huge file attachments unless requested
© 2010 The McGraw-Hill Companies, Inc.
All rights reserved.
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Internet based services
•  Internet Telephony
–  Uses the internet to make phone calls
–  Long-distance calls are either very inexpensive or
free
•  With no PC, dial a special phone number to packetize
your call
•  With a PC that has a sound card, microphone,
Internet connection, and internet telephone software
such as Netscape Conference or Microsoft
NetMeeting
–  Currently inferior in quality to normal phone
connections
–  Also allows videoconferencing
Internet based services
•  Multimedia on the Web
–  Allows you to get images, sound, video,
and animation
–  May require a plug-in, player, or viewer
•  A program that adds a specific feature to a
browser so it can view certain files
•  Example: Adobe Acrobat Reader,
RealPlayer, QuickTime
–  Multimedia Applets
•  Small programs that can be quickly
downloaded and run by most browsers
•  Java is the most common Applet language
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Email & Other Ways of
Communicating over the Net
Internet based services
•  E-Commerce
–  Conducting business activities online
–  B2B Commerce is business-to-business e-commerce
–  Online Finance now involves online banking, stock trading
online, and e-money such as PayPal
–  Online auctions link buyers with sellers
•  eBay is the most well-known example of person-toperson auctions
•  Question:
•  How many companies do you know of which do not rely on,
or at least use the Internet as part of their operation today ?
Source: Limelight Networks, Sept 2010
Video based services are dominating
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Chapter 2.6
The Intrusive Internet
The Intrusive Internet
•  The internet was founded as a
collaborative tool based on trust
•  Not everyone on the internet is honest
•  Snooping
–  Email is not private
© 2010 The McGraw-Hill Companies, Inc.
All rights reserved.
•  Corporate management has the right to view
employees’ email
•  Email that travels over the internet may be captured
and monitored and read by someone else
•  Not all ISPs protect their customers’ privacy
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The Intrusive Internet
The Intrusive Internet
•  Spam: Electronic Junk Mail
•  Spoofing
–  Using fake email sender names so the message
appears to be from a different source, so you will
trust it.
–  If you don’t know the sender, don’t open it.
–  Unsolicited email that takes up your time
and may carry viruses or spyware
–  Delete it without opening the message
–  Never reply to a spam message
–  When you sign up for something, don’t give
your email address
–  Use spam filters
–  Fight back by reporting new spammers
•  Phishing
–  Using trusted institutional names to elicit
confidential information
–  Some common schemes look like they are from
your bank or from eBay and ask you to “update”
your account.
–  Don’t do it – the legitimate company already
knows your account information!
–  If you want to update your information, CALL the
number in the phone book, not the number in the
email!
•  Don’t be a spammer yourself….
Where did the term come from ?
Monthy Python – Spam
http://www.youtube.com/watch?v=anwy2MPT5RE
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The Intrusive Internet
•  Pharming
–  Redirecting you to an imposter web page.
–  Redirects you to an imposter web page even when you
type the correct URL
–  How ?
•  Malicious software on your PC.
•  “Hostile” DNS servers
–  Remember, behind the URL an IP address exists. This
translation is dynamically done by a server normally
assigned to you during connection time. So if present in
a new environment….
The Intrusive Internet
•  Cookies
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Little text files left on your hard disk by some websites you visit
Can include your log-in name, password, and browser preferences
Can be convenient
But they can be used to gather information about you and your
browsing habits
Velkommen tilbake til
www.finn.no !
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The Intrusive Internet
The Intrusive Internet
•  Spyware
–  Applications that download without your knowledge
–  They hide on your PC and capture information
about what is on the PC and what you are doing
–  That information is then transmitted to the spyware
master’s website on the internet
–  Information may be used against you to steal your
identity, get credit cards in your name, or for other
crimes
Do you often install SW from the Internet ?
Are you sure you know (all) what these do ?
Not in place yet…
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The Intrusive Internet
End, Networks, Part I
You can never trust a site 100%...