1. Professor Yashar Ganjali Department of Computer Science University of Toronto yganjali@cs.toronto.edu http://www.cs.toronto.edu/~yganjali

2. Announcements Final project proposal Guidelines have been posted on class website. Each project completed by groups of two students Use class mailing list to find teammates if you don’t know anyone in class. 1 page proposal Due: Fri. Oct 16 th at 5PM Intermediate report Key technologies 2 pages Due: Fri. Nov. 13 th at 5PM SII 199 - Computer Networks and Society2University of Toronto – Fall 2015

3. Announcements – Cont’d Final presentation In class during the last two weeks 15 minute presentation Final report Put everything together 5 pages Due: Fri. Nov. 27 th at 5pm Volunteer for lecture notes? SII 199 - Computer Networks and Society3University of Toronto – Fall 2015

4. SII 199 - Computer Networks and SocietyUniversity of Toronto – Fall 2015 The Story … Introduction to computer networks Internet vs. mail The science of networks Characteristics, graphs, scale-free networks, … Last week: Computer networks and healthcare This week: Computer networks and business 4

5. Outline New business opportunities Online shopping Digital content Online trading Search engines and online advertisement How networks benefit small and large businesses Efficiency, communication Technologies that made it possible Ethernet Virtual private networks SII 199 - Computer Networks and Society5University of Toronto – Fall 2015

6. Networks Create New Possibilities Online shopping Amazon, eBay, … Targeted advertisement Online banking Online trading Currency exchange Stocks e-Commerce Remote meetings SII 199 - Computer Networks and Society6University of Toronto – Fall 2015

7. Online Shopping Internet can help with traditional shopping Retail E.g. order furniture online Much more convenient and flexible Peer-to-peer eBay, Kijiji, Craigslist, … Check the order status, delivery, … online Electronic payments Credit cards, PayPal, … SII 199 - Computer Networks and Society7University of Toronto – Fall 2015

8. Selling Digital Content Internet has also created new possibilities eBooks, mp3s, videos, TV, … Amazon, Apple iTunes, Netflix, … These are new forms of traditional books, CDs, … Advantages Faster delivery (almost instant) Convenience Access your library from anywhere Costs less Targeted advertisements and marketing Good for advertisers and customers (?) SII 199 - Computer Networks and Society8University of Toronto – Fall 2015

9. Advertisement on the Internet New form of advertising Advertise while people are surfing the web Have access to more information Based on past browsing history you can find out about the user’s interests … and target them with more accurate ads Might be useful for the customer as well And less annoying Can cost less Compared to TV, billboards, … SII 199 - Computer Networks and Society9University of Toronto – Fall 2015

10. Online Trading Stocks, stock options, currency exchange all possible in today’s Internet The most important issues here are Network reliability: order should not be lost Delay: extremely tight guarantees for timing required It’s all about timing, timing, timing Ordinary users: seconds to minutes Trading companies: nano seconds to micro seconds SII 199 - Computer Networks and Society10University of Toronto – Fall 2015 Online Trader ISP One ISP Two

11. Delay in Computer Networks Delay has three major components: Transmission delay: how long it takes for your machine to inject the traffic into network Propagation delay: how long it takes for data to traverse the distance between source and destination Queueing delay: how long your data packets sit in queues (buffers) on Internet routers SII 199 - Computer Networks and Society11University of Toronto – Fall 2015

12. Outline New business opportunities Online shopping Digital content Online trading Search engines and online advertisement How networks benefit small and large businesses Efficiency, communication Technologies that made it possible Ethernet Virtual private networks SII 199 - Computer Networks and Society12University of Toronto – Fall 2015

13. Search Engines You can find new things by looking for keywords Not ideal but works Question. What is the ideal way? You can find new things to buy That’s why advertising on the Internet is such a big success We spend a lot of time behind computers these days Question. how do search engines know how to sort web pages? SII 199 - Computer Networks and Society13University of Toronto – Fall 2015

14. Detour: Search Engines Question. How do search engines find web pages related to your search? They have a large number of robots that constantly crawl the web. You can simply make your own crawler. Write a script that downloads a given web page. Extracts all the links. If a link has not been downloaded before Download and repeat. SII 199 - Computer Networks and Society14University of Toronto – Fall 2015 DE BC A F

15. How To Find the Best Match There might be many pages that have the given keyword. Question. How to sort these pages and find the best match? Technique # 1. Show any page that has the given keyword, sort based on how many times the keyword appears Or use font size, font shape (bold or italic, …) as guides on how important that keyword is Question. Does this work? Why? SII 199 - Computer Networks and Society15University of Toronto – Fall 2015

16. Finding the Best Match – Cont’d Technique # 2: Use the number of links to this page as a clue. The more the number of links, the higher the rank of this page. Question. Does this work? Why? Both techniques are vulnerable to attacks Someone can easily increase the rank of their page by Increasing the font size, frequency of the keywords, … Or by creating fake pages pointing to this page SII 199 - Computer Networks and Society16University of Toronto – Fall 2015

17. Use Reputation as the Criteria Basic idea: assign a credibility score to each page. Repeatedly update credibility score of each page Divide the credibility score by the number of outgoing links, and distribute it among them. SII 199 - Computer Networks and Society17University of Toronto – Fall 2015 00 00 4 2 2

18. Use Reputation as the Criteria Basic idea: assign a credibility score to each page. Repeatedly update credibility score of each page Divide the credibility score by the number of outgoing links, and distribute it among them. SII 199 - Computer Networks and Society18University of Toronto – Fall 2015 00 22 4 1 2 1

19. Use Reputation as the Criteria Basic idea: assign a credibility score to each page. Repeatedly update credibility score of each page Divide the credibility score by the number of outgoing links, and distribute it among them. Question. Where do we start? This is the basic idea behind “PageRank” which is used by Google. SII 199 - Computer Networks and Society19University of Toronto – Fall 2015 13 22 4 1 2 1

20. Why This Matters Good search results means people will use your search engine That’s why Google doesn’t charge us Also, you need to find good matches between search results and advertisements Can enhance your return Question. Is it just a matter of good matching? Text vs. picture vs. animation Size of the ad Where it appears on a page SII 199 - Computer Networks and Society20University of Toronto – Fall 2015

21. Outline New business opportunities Online shopping Digital content Online trading Search engines and online advertisement How networks benefit small and large businesses Efficiency, communication Technologies that made it possible Ethernet Virtual private networks SII 199 - Computer Networks and Society21University of Toronto – Fall 2015

22. Benefits of Using Networks in Business Networks allow sharing the cost of peripherals Printers Scanners Shared data storage... Improved communication Locally Remotely Work from home Or while traveling SII 199 - Computer Networks and Society22University of Toronto – Fall 2015

23. Efficiency Data is readily available Rather than looking for a physical file Can serve customers faster And better: shared data Reduce errors and improve consistency All staff work from the same source of information Make standard manuals and guidelines available Data can be backed up and checked for consistency SII 199 - Computer Networks and Society23University of Toronto – Fall 2015

24. Outline New business opportunities Online shopping Digital content Online trading Search engines and online advertisement How networks benefit small and large businesses Efficiency, communication Technologies that made it possible Ethernet Virtual private networks SII 199 - Computer Networks and Society24University of Toronto – Fall 2015

25. What Technologies Made This Possible Ethernet is the dominant networking technology for Local Area Networks (LANs) Extremely simple to setup Most of the time, just plug your computer and it works Very inexpensive to setup and maintain Supports both wired and wireless networking Relatively high rates: 10Mb/s to 100Gb/s SII 199 - Computer Networks and Society25University of Toronto – Fall 2015

26. How Does Ethernet Work First, we need an address Remember the mail example: This is how other computers know how to find you Two ways to assign an address to your computer Manual setup We call this static IP address assignment Automatic setup We call this one dynamic IP address assignment The protocol used is called DHCP (Dynamic Host Configuration Protocol) SII 199 - Computer Networks and Society26University of Toronto – Fall 2015

27. How Do Nodes Talk in Ethernet Shared communication medium (wired or wireless) Can lead to collision Think of two or more people talking in the classroom We need some sort of coordination to avoid collision Only one person speaks at a time How do we do this in real life? SII 199 - Computer Networks and Society27University of Toronto – Fall 2015

28. How Do Nodes Talk in Ethernet – Cont’d Here is how Ethernet solves this problem Listen: if nobody else is talking you can start Otherwise wait till they finish While talking keep listening Nobody else talks  done! Somebody starts talking  collision In case of collision Choose a random time in the future Repeat Question: How long should we wait before retrying? SII 199 - Computer Networks and Society28University of Toronto – Fall 2015 Why?

29. Wireless Networking in an Office Easier to setup No need to physically connect nodes Inexpensive Very flexible Can handle many computers Different types of devices Mobility: computers can be moved easily No need to reconfigure SII 199 - Computer Networks and Society29University of Toronto – Fall 2015

30. … And The Problems Lower rate compared to wired networks 54-100Mb/s compared to 100Mb/s 1Gb/s or higher Shared medium Limited number of wireless channels available All machines are on the same medium In wired, you can have point-to-point connection Less secure Your signal can be heard by people nearby SII 199 - Computer Networks and Society30University of Toronto – Fall 2015

31. Virtual Private Networks (VPNs) Your employees might want to connect to their business network from home, or while traveling Many security concerns Virtual Private Networks make this possible Remotely connect to your work network As if you are sitting in your office Access to all resources (databases, peripherals, …) All communications are encrypted Question. How do you build a VPN? SII 199 - Computer Networks and Society31University of Toronto – Fall 2015

32. Remote Collaboration A lot of people work from home these days Long distance collaborations Researchers, students/mentors, … Tons of tools to make this possible Voice/video conferencing and presentations Online sharing of documents Collaborative writing Google docs, MS OneNote, … Energy savings, impact on environment Makes sense financially as well; gas prices going up SII 199 - Computer Networks and Society32University of Toronto – Fall 2015

33. Other Areas of Impact Outsourcing Computer networks bring resources closer Ideally, customer won’t see a difference Business-to-business services Not only you can provide service to your customers You can buy and sell products and services to other businesses E-Commerce Information diffusion Information is money Technologies for fast distribution and aggregation of news …? SII 199 - Computer Networks and Society33University of Toronto – Fall 2015

34. Summary and Discussion Computer networks have already changed the way we do business Online shopping, digital content, trading, e-Commerce, advertisements, … They provide many benefits for small and large businesses Communication, resource sharing, … What other areas can you think of? What are the technologies we need to work on today? SII 199 - Computer Networks and Society34University of Toronto – Fall 2015