Fundamentals of Telecommunications Week 67: Internets

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Fundamentals of TelecommunicationsWeek 6-7
Internets Intranets

• Elizabeth Lane Lawley, Instructor

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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
• Packet-switched network using primarily virtual
  circuit communications

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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

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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

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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)

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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

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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

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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

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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

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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.

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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 surpassed all other applications in amount
  of data being transferred

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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

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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)

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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

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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/

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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

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HyperText Markup Language (HTML)

• Derived from SGML (Standard Generalized Markup
  Language)
• Uses tags to indicate formatting characteristics
  them with a specific format
• Tags are defined functionally, not visually
• Tags can indicate a link to another document or
  resource
• Tagged text can be displayed by choosing View
  Source in most browsers

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Tools for Searching

• Search Engines
• Subject Guides/Catalogs
• Referral and Clipping Service

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Search Engines Characteristics

• Index full-text of documents (or a selected
  segment)
• Data can be gathered by "robots" or "spiders"
  without human intervention
• Can add and index documents more quickly
• Seldom evaluative

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Search Engines Differences

• Comprehensiveness (and methods for counting
  documents)
• Frequency of updating
• Portions of documents indexed
• Ability to "weight" searches
• Search language/syntax
• Evaluative component

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Search Engines WWW Examples

• Alta Vista
• Excite
• InfoSeek
• Lycos

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Search Engines Other Examples

• FTP Files Archie
• Gopher Documents Veronica
• Usenet News DejaNews, Reference.com
• People
• Four11
• Switchboard
• Individual organization directories

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Search Engines Search Strategies

• Selecting terms
• Combining terms (Boolean Logic)AND, OR, NOT,
  NEAR, etc
• Narrowing a search that yields too many "hits
• Broadening a search that yields too few "hits

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Subject Guides Characteristics

• Evaluative
• Only titles, annotations are searchable
• Similar items are grouped together
• Items are suggested and checked by real people,
  not automated tools

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Subject Guides Differences

• Comprehensiveness (number of resources)
• Breadth of coverage (number of topics)
• Currency of entries
• Quality of annotations/evaluation

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Subject Guides WWW Examples

• YAHOO
• Snap!
• Wallace Library Guides
• Infoseek Guide

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Subject Guides Search Strategies

• Search on a known example to determine subject
  heading
• Try multiple sites
• Look at "other sites" links on the items
  retrieved

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Referral Services Characteristics

• "Learn" your likes and dislikes
• Suggest resources based on your profile
• Use similar users to help determine your
  preferences

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Referral Services Examples

• firefly

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Clipping Services Characteristics

• Similar to search engines
• You set up "profile", matching items are
  identified
• Can be collected for you to retrieve, or mailed
  to you directly

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Clipping Services Examples

• InfoSeek
• NewsPage
• NewsHound
• reference.com

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News Services Examples

• CNN (Standard Custom)
• USA Today
• New York Times
• National Public Radio

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The Overlooked Information Resource People

• Mailing Lists
• Usenet Newsgroups
• Informal Networks

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Evaluating Online Information

• Credibility of source
• Credibility of guide
• Currency of content

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Print References

• Books
• Journals
• Newsletters
• Advertisements

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Using and Organizing Online Resources

• Check sources
• Cite appropriately
• Keep lists
• Bookmark lists
• PIM programs
• Specialty programs (e.g. GrabNet, SmartMarks, etc)