Download How to Communicate via Internet?

SEMMELWEIS UNIVERSITY
Institute of Health Informatics
Data transmission and
telecommunication. The Internet.
Tamás Tóth
9. February 2015
Agenda
• Communication: definitions and types, the
Internet
• Human-human communication via the
Internet
• Human-machine communication via the
Internet: some technical basics
• The World Wide Web
What is COMMUNICATION?
Exchanging information
Sender
Channel
Receiver
Coding
Transmission
Decoding
What is INFORMATION?
„News or facts about something.”
• Abstract term – hard to define
• According to the most definitions, information must
– be SOMETHING, although the exact nature (substance,
energy, or abstract concept) isn’t clear;
– provide NEW information: a repetition of previously
received message isn’t informative;
– be TRUE: a lie or false information is mis-information, not
information itself;
– be ABOUT something.
Related terms: DATA and KNOWLEDGE
http://www.knowledge-management-tools.net/knowledge-information-data.html
Example
http://blog.falkayn.com/2011/03/is-knowledge-all-there-is.html
Communication Types
Point-to-point
On-line
Off-line
Broadcasted
Communication Types 1.
• Offline
–The receiver has a „mailbox” which can store the
message
–The receiver might not be accessible when the message
arrives
–E.g.: mail
• Online
–There is no mailbox
–If the receiver is not available when the message
arrives, the message is lost or there is no connection
–E.g.: phone
Communication Types 2.
• Point-to-point communication
–One entity is connected to another entity
–The sender knows exactly the receiver
–E.g.: telephone line, two-way radio
• Broadcasting communication
–One entity is connected to several entities
–The sender might not know the receiver(s)
–E.g.: television, radio
New media for communication: the
INTERNET
• Worldwide system of computer networks –
a network of networks
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Network types
• LAN: Local Area Network
–Computer network in a relatively small area
–Typically the network of a building/company
• WLAN: Wireless Local Area Network
–Special type of LAN using wireless (Wifi) technology
• WAN: Wide Area Network
–A network covering a large area e.g. city, country
–The Internet is the largest (worldwide) WAN
Internet – the history
• It was conceived by the Advanced Research Projects Agency
(ARPA) of the U.S. government in 1969 and was first known as
the ARPANet.
• The original aim was to create a network that would allow
users of a research computer at one university to be able to
"talk to" research computers at other universities.
• A side benefit of ARPANet's design was that, because
messages could be routed or rerouted in more than one
direction, the network could continue to function even if parts
of it were destroyed in the event of a military attack or other
disaster.
• It has exponentially grown for civilian usage (commerce,
entertainment, education etc.)
The Internet today
• Today’s networks: server, PC, laptop, tablet,
smartphone, tv …
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The Internet as communication medium
Human-human communication
E-Mail (Electronic Mail)
• E-mail was one of the first uses of the Internet and is still one of
the most popular use.
• Off-line (but the duration of delivery can be less than a minute).
• Point to point connection, but you can send the same letter to
several address (multipoint).
• You can send:
– plain (ASCII text) or formatted (HTML) text
– binary files (images, sound) as attachment
– voice- or videomail
• E-mail client programs eg.:
– ThunderBird, Outlook
– Online mailing services: Gmail, Yahoo mail
Mailing Lists
• Off-line (e-mail). Your e-mail client enough to use this feature.
• If you subscribed, you will automatically get every e-mail has sent
to the list.
• Broadcasted. If you send a message to the address of the list,
everybody who subscribed will get your mail. (You don’t (have to)
know exactly who will get your message).
On-line Chat
• On the Internet, chatting is talking to other people who are using
the Internet at the same time you are. (on-line)
• Usually, this "talking" is the exchange of typed-in messages (low
bandwidth needed).
• It could be broadcasted - group chat (everybody has joined the
chat room can see your message) or point-point - private chat
(between two person).
• A chat can also be conducted using sound, video; assuming you
have the bandwidth access.
• Such services:
– Skype, Gtalk,
– Old services: ICQ, IRC, Chat rooms
Phone via Internet
• Internet telephony is the use of the Internet rather than the
traditional telephone company infrastructure to exchange spoken
or other telephone information.
• Similar to traditional phone: online and point-to-point
• You can call
–Another computer (if your partner have registered to the
service, and actually online)
–Telephone (a provider connects the telephone network
to the internet on the other side, for a fee)
• Programs and services e.g..:
• Skype,
• MSN,
• Nonoh
IP telephone
• Connects computer networks and telephone
networks
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Phone via Internet
Sound Digitalization
(real-time voice transfer needs more bandwidth than typed in chat)
Podcast
• Distribution of recorded sound over the
Internet
• Client may subscribe for upcoming episodes
• The data might be downloaded to a portable
music player and listened to at a convenient
time (driving, travelling)
• Off-line and broadcasted communication
Video Transfer via Internet
• Real-time (on-line) video transfer require much wider band
than voice transfer.
• The following types of video transfer occur on the Net:
– On-line, point to point videoconference
– On-line, broadcasted audiovisual feeds (internet tv
channels, YouTube).
– Off-line, pre-recorded audio/video archives.
Real-time transfer is rarely demanded in this case.
You can download the whole file (slowly) and play
it from your local (fast) hard drive.
Streaming: playing starts before the whole video
is downloaded.
Video Transfer via Internet - Videoconference
• A videoconference is a group or a person-to-person discussion
in which participants are at different locations but can see and
hear each other as though they were together in one place.
• Most off-the-Internet videoconferences today involve the use of
a room at each geographic location with special video camera
and document presentation facilities
• On the Web, a lot of product (Skype, webinars,
msn), offers a simple form of videoconference
with each user (optionally aiming a small
video camera at herself or himself) connected to
other users in a pre-arranged chat session.
Video Transfer via Internet - Streaming Video
• Streaming video is a sequence of "moving images" that are sent
in compressed form over the Internet and displayed by the
viewer as they arrive. Streaming media is streaming video with
sound.
• The user needs a player, which is a special program that
uncompresses and sends video data to the display. (It can be a
browser plugin, or the newest browsers natively support video
playback – according to the HTML5 standard)
• Streaming video is usually sent from prerecorded video files,
but can be distributed as part of a live broadcast "feed”.
• Eg: YouTube, internet television
Bandwidth need of different services
Textual data
Voice data
• Email
• IP telephone
• Typed-in chat • Podcast
Video data
• Videoconferencing
• Online video
The Internet as communication medium
Human-machine communication
Why Human-Machine communication?
• The previous services are to facilitate the direct human
communication. The next services are to use the resources of a
far computer (run a program on it, access files, etc.)
• You can download data (text, picture, sound, video...) stored on
an Internet connected computer without other people direct
assistance.
• You have to say to the server computer what do you want to get
and the server will send it to you automatically.
• Previously of course the owner of the server has to allow the
accessing.
A few Technical Concepts
The following technical points haven’t been mentioned at the
part of e-mail, telephony, chat, etc. In general you don’t have
to know them to use that services. But now these concepts will
be more visible for the average user.
Client / Server architecture
TCP/IP protocol
DNS
URL
Client-Server Architecture
1. The client sends a
request
2. The server
processes the
request
3. The server sends a
response to the
client
Identification on the network
• IP address: identifies a device on the network
– E.g.: 193.6.211.36 (IP protocol version 4)
– 4 numbers separated by points (0-255)
• One device may have more than one (servers,
network devices)
• Not always permanent, e.g. the provider assigns it at
login
• In theory: unique identifier, but practically there are
„internal” IP addresses (used in LANs)
• Permanent, physical identifier: MAC address
– 12 hexadecimal digits, e.g.: E0-69-95-57-D0-EF
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Why internal IPs exist?
”I think there is a world market for about five
computers.”
Thomas Watson, president of IBM, 1943
• The possible IP addresses were split to groups
• One group = min. 32000 address
• A company with 10 computers occupied so many
addresses
• Few years ago, we run out of available IPs
• The ultimate solution: IPv6
• But until it is widely available, we need some tricks
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TCP/IP protocol
• Computers on the Internet communicate using
protocols. A protocol is a set of rules.
• TCP/IP is a fundamental protocol for data transfer via
the network.
• Data is transferred as packets
– A packet contains data + control information (e.g. sender,
address, data volume)
– Packets are transferred on the network individually (even if
they belong e.g. to the same file)
Data packets and protocol levels
M
Level 3
Level 2
H2
M
H1 H2 M1 T1
M
H2
M
H1 H2 M1 T1
Level 1
H1 M2 T1
H1 M2 T1
Physical layer
Sending machine
Receiving machine
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DNS
• Domain Name System
• A hierarchical naming system for computers and other
resources connected to the Internet
• Translates human-friendly names to technical identifiers (IP)
URL – Uniform Resource Locator
•
•
•
•
A reference to a resource on the Internet
The most common usage is a web address
E.g.: http://en.example.org/wiki/Main_Page
Syntax:
• protocol://domain.name/path/file.name
• The protocol defines the type of communication/transmission,
e.g. HTTP, FTP
E-mail protocols
• E-mail services use
several protocols for
exchanging emails:
– SMTP: for sending emails
– IMAP, POP3: for
receiving e-mails
Internet provider (UPC) or
mail service (Google/Gmail)
Remote access
• Remote access is the way you can access someone else's
computer, assuming they have given you permission.
• With these client-server programs, you log on as a regular user
with whatever privileges you may have been granted to the
specific applications and data on that computer.
• The result of this request would be an invitation to log on with a
userid and a prompt for a password. If accepted, you would be
logged on like any user who used this computer every day.
• You can use applications running on the server.
• E.g. Telnet, VNC, Remote Desktop
FTP (File Transfer Protocol)
• FTP, a standard Internet protocol, is the simplest way to
exchange files between computers on the Internet. FTP is an
application protocol that uses the Internet's TCP/IP.
• FTP is commonly used to transfer Web page files from their
creator to the computer that acts as their server. It's also
commonly used to download files to your computer from other
servers. Using FTP, you can also update files at a server.
• You need to log on to an FTP server. However, publicly available
files are easily accessed using anonymous FTP.
• Commonly used FTP client programs eg.:
– CuteFTP, WsFTP,
Communication ports
• Definition: application-specific communication endpoint
• Uniquely identifies different applications which want to
communicate on the network
– Enables to share a single physical connection
• IP address and the port together identify to target application
of a request over the net
• Common ports:
– 21: FTP (upload and download files from server)
– 25: SMTP (sending emails)
– 80: HTTP (web browsing)
The Internet as the Embodiment of Human
Knowledge
World Wide Web
• A technical definition of the World Wide Web is: all the
resources and users on the Internet that are using the
Hypertext Transfer Protocol (HTTP).
• A broader definition comes from the organization that Web
inventor Tim Berners-Lee helped found, the World Wide Web
Consortium:
"The World Wide Web is the universe
of network-accessible information,
an embodiment of human knowledge."
World Wide Web
- Getting Started
• Using the Web, you have access to millions of pages of
information. Web "surfing" is done with a Web browser, the
most popular of which are Firefox, Google Chrome and
Microsoft Internet Explorer.
• A browser is an application program that provides a way to look
at and interact with all the information on the World Wide Web.
• Technically, a Web browser is a client program that uses the
HTTP (Hypertext Transfer Protocol) to make requests of Web servers
throughout the Internet on behalf of the user.
• HTML (Hypertext Markup Language) is the set of "markup" symbols
or codes. This language is used to define the content and
structure of the web pages, understand by the browsers.
World Wide Web - Searching
• Technically, if you want to get the information carried by a
Web site, you have to know the URL of that resource (text,
image, video, etc.) and type it into your browser (to address
bar).
• If you don’t know the exact address, there are search engines
which try to seek that information for you, and say where
(under what URL) will you find it (at least you have to know the
URL of an engine).
• Search engines eg.:
– www.google.com
– www.yahoo.com
– www.bing.com
The evolution of the Web
• Static websites (web 1.0)
–Read content
–Everything stored as single files
• Dynamic websites (web 1.5)
–Use of server side scripting languages, databases
–Content generated „on the fly”
• Web 2.0
–Involvement of users
–Not just read, but also create content  social
media
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SEMMELWEIS UNIVERSITY
Institute of Health Informatics
Thank you for your attention!