The Power of Networks Six Principles That Connect Our Lives Course Overview Chien-Chung Shen CIS@UD

Why This Course? social networks, economic networks, network services & applications, ……. 1st edition in 2000 Computer Networks - layers and protocols (TCP, IP, HTTP, etc.) October 2016

Overview “Networks” are everywhere nowadays e.g, who we are friends with on Facebook; how our emails get carried through Internet in a matter of milliseconds social, communication, economic, etc. different functions: recommending movies to watch, controlling device power levels, and viralizing video clips inner workings of these functions are six hidden principles that pop up in all different kinds of networks This course discusses these six principles of “networking” that connect our lives via basic arithmetic and supplemental materials build intuition (with algebra)

Six Principles of Networking Sharing is hard Ranking is hard Crowds are wise Crowds are not so wise Divide and conquer End to end Phrases that summarize the way “networks” are designed, built, and/or managed

Background & Lectures CISC 450/650 are NOT pre-requisite for the course Basic mathematics (algebra) Interactive lectures via questions and answers

Part 1 Sharing Is Hard

Overview How network resources can be shared among many people? Two wireless technologies cellular WiFi What resources? electromagnetic spectrum over “air” Key approaches managing interference when to communicate how loudly to communicate pricing network usage smartly

Part 2 Ranking Is Hard

Overview In Part 1, Sharing Is Hard, it is challenging to efficiently divide shared resources among users Part 2, Ranking is Hard, how to find appropriate ranking of a set of items Google’s two practices as examples Two types of “pages” ad spaces bids from buyers (merchants) search results importance and relevance PageRank algorithm

Part 3 Crowds Are Wise

Retail shopping, movie watching, and taking classes are daily activities impacted by Internet eCommence of Amazon content distribution of Netflix MOOC (massive open online course) of Coursera By doing these things online, we are contributing to an ever-increasing body of knowledge about peoples’ behaviors and preferences When navigating websites, our actions are recorded and used to change experience of those who subsequently visit the sites feedback for products on Amazon → ranking rating for movies on Netflix → recommendation

How products are ranked on Amazon how movies are recommended by Netflix How people learn from one another in MOOC Core idea → wisdom of crowds As a crowd gets larger (more information collected), collective decision made by crowd will be better higher-quality estimate on what truth is Modeling of social networks limitation of models in their explanatory and predictive capabilities underlying assumptions of models

Part 4 Crowds Are Not So Wise

Everyone’s opinions are independent Two (research) questions to ask Wisdom of crowds → aggregating information from a mass of people often results in better decisions than can be made by individuals Inherent assumption? Everyone’s opinions are independent Two (research) questions to ask In what situations will they not be independent? What happens when they aren’t?

What other people think will influence your actions watch that YouTube video because everyone was talking about it buy iPad because everyone else has one The more people you see that have followed through with such an action, the more temptation increases for you to do the same Dependence of opinions in social networks viralization social influence

Part 5 Divide and Conquer

Divide and Conquer Topics of previous chapters rely on existence of Internet How is Internet designed, built, and managed? One imperative property of Internet scalability because # of connected devices and sheer size of Internet constantly grow How to achieve scalability? efficient way to share network resources division of management responsibility (both geographically and functionally) so that subparts can be tackled more easily Scalable routing

Part 6 End to End

Congestion Control What is Internet? Internet Congestion control a cloud a black box client and server communicate without knowing the details inside Congestion control find out how congested network is: how? client sends something to server client waits for responses from server end-to-end (at C and S) by TCP Distributed coordination among devices with back & forth acknowledgements Internet

Social Networks Small world phenomenon principle that we are all linked by “short” chains of acquaintances or “six degrees of separation” Small Worlds and Six Degrees of Separation The Science of Six Degrees of Separation The six degrees: Kevin Bacon at TEDxMidwest