What is the Internet

1
What is the Internet?

• Collection of interconnected networks using
  TCP/IP protocols to communicate with each other
• No single owner or controlling agency
• An environment rather than a system

2
Internet Protocols (TCP/IP)

• What are protocols? A way to overcome
  communication differences
• TCP Transmission Control Protocol
• Controls the form and route that data takes going
  across the network
• IP Internet Protocol
• Handles the addressing of Internet computers
• Packet-switching vs. Circuit-switching

3
Internet Timeline

• 1969 ARPANET
• 1972 Telnet
• 1973 FTP
• 1976 Queen Elizabeth sends e-mail
• 1977 First mailing list
• 1979 Usenet, MUD
• 1981 BITNET, CSNET
• 1982-83 TCP/IP

• 1984 DNS
• 1986 NSFNET, Freenet
• 1990 ARPANET ends, The World starts
• 1991 CIX, Gopher, WAIS, WWW
• 1992 Veronica
• 1993 Mosaic
• 1995 Java
• 1996 Internet phones

4
Internet (IP) Addresses

• When an organization connects to the Internet, it
  obtains a set of IP addresses for its computers
• Made up of 4 sets of numbers separated by periods
  or dots
• RITVAX 129.21.3.4
• Grace 129.21.4.23
• My Laptop 129.21.22.12
• Goes from least to most specific

5
Canonical Addresses

• Easier to remember alphabetic names
• Numeric addresses have corresponding canonical
  names so that you dont have to remember the
  numeric addresses.
• Minimum of 3 parts (usually 3-5)
• ritvax.rit.edu
• www.rochester.lib.ny.us
• One system can have multiple canonical names
  (www.rit.edu, grace.rit.edu)

6
Top-Level Domains

• Examples
• com commercial organizations
• edu educational organizations
• gov governmental organizations
• org other organizations
• net network resources
• mil military resources
• jp, nl, uk, ca, etc international organizations

7
Second-Level Domains

• e.g. rit.edu, internic.net, itcs.com
• .com, .edu, .org, and .net addresses are all
  managed by the InterNIC
• Number of 2nd level domains has grown from 1,000
  in 1984 to 1.5 million now
• Commercial domains (.com) are crowded, fastest
  growing
• Domains were free until 1995

8
Subnet Names

• Not always present
• Used when an organization divides their TCP/IP
  network into several parts
• e.g. it.rit.edu, cs.rit.edu, isc.rit.edu

9
Host Names

• Name identifying a computer within an
  organizations network
• Organization selects primary host names,
  end-users can select workstation names
• e.g. www.rit.edu, osfmail.isc.rit.edu,
  porsche.it.rit.edu, spot.it.rit.edu

10
Telnet (CLI)

• a tool to let you log in to remote computers
• to start, type telnet at the system prompt
  followed by the host address
• e.g., telnet grace.isc.rit.edu
• or you can just type telnet and after you see
  the telnetgt prompt, type open hostname.
• e.g., telnetgt open grace.isc.rit.edu

11
FTP (File Transfer Protocol)

• moving files from one computer to another
• to start, type ftp at the system prompt
  followed by the remote host name
• e.g., ftp ftp.rit.edu
• There are many public anonymous ftp servers which
  let you log in without having an account at the
  server

12
FTP Operation

• In a CLI, you need to understand the command
  strucutre (GUIs handle much of this for you)
• Need to understand file formats
• Plain text (ASCII)
• Binary files (programs, formatted documents,
  compressed files)

13
Finding Someone

• A single, unified Internet users directory does
  not exist at present.
• Many organizations maintain individual
  directories
• Finger can be used if you know the host (finger
  name_at_host)
• Web directories are becoming more sophisticated
  and comprehensive

14
Internet Gopher

• developed in 1991 by the University of Minnesota
  to provide a cheap and easy way for campus wide
  information distribution
• a menu-driven system that lets you browse through
  the Internet in a simple, consistent manner
• hierarchical structure of menus and submenus

15
Types of Gopher Resources

• menus
• text files
• non-text files
• e.g., pictures, sounds, or binary files
• Internet services
• e.g., telnet sessions
• searchable databases

16
Veronica

• gopher-based resource that allows you to search
  gopherspace for menu items
• the first version of veronica was developed in
  November 1992
• There are a number of veronica servers around the
  Internet
• To use it, you have to find it somewhere on a
  gopher server

17
World Wide Web

• Developed by Tim Berners-Lee in 1991 at the
  European Particle Physics Laboratory (CERN) to
  allow physicists around the world to share
  information
• Marc Andreessen, employee at NCSA, introduced the
  GUI Web browser, Mosaic, in 1993.

18
World Wide Web Technology

• Based on the concept of hypertext
• Single interface to a variety of protocols and
  standards to access the information on the
  Internet
• Has become the predominant Internet application
• 1993 annual rate of growth is 341,634
• 1995 surpasses all other applications in amount
  of data being transferred

19
World Wide Web Documents

• Documents have embedded selectable links that
  point to other documents
• Documents can be text or non-textual information
  such as audio, video, or multimedia documents
• Multimedia nature of the web allows non-text
  information to be embedded into documents, not
  just linked separately

20
World Wide Web Operation

• Data stored on servers
• Users access data with browsers
• text-based browser (e.g., lynx) can run on a
  muti-user CLI system
• GUI browser (e.g, Mosaic, Netscape, Internet
  Explorer, etc.) requires a direct Internet
  connection (dial-up or LAN)

21
World Wide Web Functions

• Display HTML pages
• Retrieve files (often using FTP)
• Access Gopher sites
• Read newsgroups
• Search for information or people
• Display still images and video
• Listen to sound files
• Activate telnet connections

22
Uniform Resource Locator (URL)

• provide a standard means of locating Internet
  documents
• simple addressing scheme unifies a wide variety
  of disparate protocols

• specify the three pieces of information
• the protocol to be used (e.g., http, ftp, gopher,
  telnet, etc.)
• the server (and optional port)
• the file path to retrieve
• e.g., http//www.rit.edu/ellics/index.htmlhttp/
  /www.itcs.com80/elawley/ftp//ftp.netscape.com/
  telnet//wally.rit.edu/gopher//gopher.cni.org/

23
HyperText Transfer Protocol (HTTP)

• the primary protocol used to distribute
  information within WWW
• a connectionless protocol
• limited to one request per connection
• the connection is broken after each request

24
HyperText Markup Language (HTML)

• derived from SGML (Standard Generalized Markup
  Language)
• define areas of text by tagging them with a
  specific format
• the tags are defined functionally, not visually
• provide the capability to create hypertext links
  between documents
• HTML can be displayed by choosing View Source
  in most browsers

25
Lynx A Web Browser

• a text-based Web browser on both UNIX and VAX
  platforms
• cannot display images or play sounds
• alternative way to access the Web if you dont
  have a dedicated connection or a SLIP/PPP dial-up
  account
• uses keyboard commands to move through the
  document