Courses/Computer Science/CPSC 203/CPSC 203 2008Winter L03/CPSC 203 2008Winter L03 Lectures/Lecture 2

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Lecture 2

The objectives of this class were to:

  • Quickly set some class etiquette standards, determine final topics list
  • Describe the Origins of the Internet, it's structure, and how that structure is evolving. Link Internet structure to its capabilities and limitations

Lecture Glossary

  • Hub - A node with many edges. In terms of web pages, a hub is considered a web page that is linked to by many other web pages.
  • TCP/IP - Transfer Control Protocol/Internet Protocol
  • HTTP - Hyper Text Transfer Protocol
  • WWW - World Wide Web
  • HTML - Hyper Text Mark-up Language
  • XML - File type: eXtensible Markup Language
  • Web 1 - A general reference to the World Wide Web during its first few years of operation. The term is mostly used to contrast the earlier days of the Web before blogs, wikis, social networking sites and Web-based applications became commonplace.
  • Web 2 - An umbrella term for the second wave of the World Wide Web, which was coined by O'Reilly Media (www.oreilly.com) and CMP Media (www.cmp.com) in their 2004 and subsequent conferences on the subject. Sometimes called the "New Internet," Web 2.0 is not a specific technology; rather, it refers to two major paradigm shifts. The one most often touted is "user-generated content," which relates more to individuals. The second, which is equally significant, but more related to business, is "thin client computing."
  • Scale-Free Network - A scale-free network is a noteworthy kind of complex network because many "real-world networks" fall into this category. In a scale-free network there are some highly connected nodes, the "hubs" that connect to many other sites. Scale free networks are resistant to random attacks but direct attacks on the hubs are more volatile and can lead to failure. See detailed notes below.
  • Email - A system for sending and receiving messages electronically over a computer network, as between personal computers.

Only Connect : Origins and Structure of the Internet

Only connect! That was the whole of her sermon.

Only connect the prose and the passion, and both will be exalted,

And human love will be seen at its height.

Live in fragments no longer.

Only connect ...

-- E.M. Forster, Howards End.


Brief History of the Internet

  • Cartoon history of the Internet (Arpnet(TCP/IP) -- Internet(Email was the "killer" app) --- Web 1.0(HTTP and HTML) ---- Web 2.0 (XMLs)
  • Some Critical People
    • Vint Cerf -- Developed TCP/IP that led to Arpnet
    • Ray Tomlinson -- Developed first email system
    • Tim Berners Lee (TBL) -- Developed HTML and HTTP protocols leading to world-wide web
    • W3C led by TBL -- Develops XML standards, Ontology Protocols, and other protocols leading to "Semantic Web"

Scale Free Networks

  • The notion of a scale free network -- follows a Power Law (see below) and has the unique property that the same pattern occurs at all network scales.
  • How a scale free network develops (growth, and preferential attachement of new nodes to existing nodes with higher connectedness)
  • Properties of scale free networks as they relate to the Internet (resistant to random attacks, theoretically vulnerable to directed attacks on hubs, in a scale free network there is no minimum threshold for viral contagion).
Scale Free Poperties I: Dynamics
  1. Growth
  2. Preferential Attachment
Scale Free Properties II : Structure
  1. "Small Worlds" Phenomena -- small characteristic path length between two random nodes.
  2. Resistant to Random Attacks
  3. Susceptible to Directed Attacks on Hubs (theoretically)
  4. No minimal viral threshold -- viruses can 'hang around' and reinfect population
Scale Free Networks and Power Laws
  • Scale Free Networks are Examples of Power Laws
  • Power laws are of the form: P(K) ~ 1/K ** B -- Yikes, MATH! What does this mean?
  • It means: P(K) is the Probability that a node in the network, connects with K other nodes. The coefficient "B" varies between 2-3 for most real networks.
  • Other Examples of scaling:
    • Plant Productivity/ Area
    • Bone length and cross-sectional area
    • The above are examples of "Allometric Relationships" where two attributes of an organism maintain a power-law relationship. See : http://en.wikipedia.org/wiki/Allometric_law
    • Fractal Branching. E.g. for the May Equation (also called the "Logistic Map"): Xt+1 = rxt(1-xt)


Lecture Resources

See http://en.wikipedia.org/wiki/Scale-free_network

and particularly the wonderful Scientific American Article: http://www.nd.edu/~networks/Publication%20Categories/01%20Review%20Articles/ScaleFree_Scientific%20Ameri%20288,%2060-69%20(2003).pdf

One of the "pioneers" in exploring the Internet as if it were an ecosystem is Bernardo Huberman. Here is a link to his book, "The Laws of the Web" and other research: http://www.hpl.hp.com/research/idl/people/huberman/


E.M. Forster poem fragment from: http://web.mit.edu/gtmarx/www/connect.html

The Laws of the Web. Patterns in the Ecology of Information. 2001. By B.A. Huberman.

Linked. How Everything is Connected To Everythiung Else and What it Means for Business, Science, and Everyday Life. 2003. By AL Barabasi.

Weaving the Web. The Original Design and Ultimate Desitny of the World Wide Web by its Inventor. 1999. Tim Berners-Lee.

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