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Course Overview and Introduction Nick Feamster CS 6250: Computer Networking Fall 2011.

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Presentation on theme: "Course Overview and Introduction Nick Feamster CS 6250: Computer Networking Fall 2011."— Presentation transcript:

1 Course Overview and Introduction Nick Feamster CS 6250: Computer Networking Fall 2011

2 2 Who Am I? Nick Feamster –Associate Professor –Research Area: Networking Operations and Security Office: Klaus 3348 Questions: Use Piazza Q&A Office Hours: Wednesdays 12-1 p.m. TAs: Srikanth Sundaresan, Surya Sivakumar

3 Its an Exciting Time More people –Today: 1.9B users –2020: 5B users More global –Africa, India: ~7% penetration More things More traffic –44 exabytes by 2012 Fewer wires 3 Source: internet world stats

4 Its Also a Critical Time As much as 95% of traffic is spam –Spam moving to new domains such as Twitter About 50k new phishing attacks every month Nearly 60 countries censor Internet content 4

5 New Technology and Innovation 5 …but, much of this innovation is actually coming from industry. 4.5 Billion GSM. WCDMA subscriptions (source: gsacom)

6 Meanwhile…A Crisis of Confidence We dont need a course in networking; it is all details and no principles. You cant actually deploy any new technology; Cisco holds the keys to innovation. What are the top ten classic problems in networking? I would like to solve one of them and submit a paper to SIGCOMM. After hearing that we don't have such a list: "Then how do you consider networking a discipline? So, these networking research people today aren't doing theory, and yet they aren't the people who brought us the Internet. What exactly are they doing? Networking is an opportunistic discipline. 6

7 7 Why Has It Been So Difficult? Network applications (and threats) evolve –Developments call for changes to the network itself Testing new technologies is challenging –Convince a network operator to try something out? –What if the change requires universal deployment? Deploying new technologies is more challenging –And things are getting worse, not better

8 8 How Did We Get Here? Internet design came from a different era –Single group of cooperative designers –Cohesive network –Trusted group of users The reality today is much different –Independently operated networks –Business realities –Untrusted parties with competing goals Difficult to deploy solutions that require fundamental change.

9 How can networking research turn the tables? Yesterdays networking researchers developed technologies to improve the operation of existing networks. (Reactive approach) Tomorrows networking researchers should develop technologies that enable evolution and innovation. (Proactive approach) We have the plumbers and users. We need the architects. 9

10 Our Current Thinking: Network as Artifact 10 There is a tendency in our field to believe that everything we currently use is a paragon of engineering, rather than a snapshot of our understanding at the time. We build great myths of spin about how what we have done is the only way to do it to the point that our universities now teach the flaws to students (and professors and textbook authors) who don't know better. -- John Day

11 Instead: Could we change the network as easily as applications? 11 TCP/IP Header in Lego Format.

12 Home Networking & Access Networks Problems –Performance problems are difficult to debug –Access ISPs discriminate, give poor performance –Hard to manage, troubleshoot, secure Research –Programmable gateways in homes –Perform active and passive measurements –Collect information about user behavior –Remotely control, troubleshoot, and secure –Project ongoing with FCC

13 Our tool, Collage, featured in New Scientist Anti-Censorship Problems –Censorship in 23 countries worldwide –Even in the US! –Existing techniques are not deniable Research –Exploiting different media for cover traffic (e.g., user-generated content) –Bootstrapping and incentives –Designing better resistance to coercion –Use of social networks

14 Programmable Networking Problems –Networks are difficult to configure, manage, secure –Detecting and preventing errors –Predicting the outcome of a configuration Research –Analysis of existing network configurations –Design of high-level languages for configuring and programming networks –Design and prototyping of new programmable network devices Frequently Changing Configuration Commands

15 Why Networking is Fun You can apply many different tools –Theoretical foundations –Statistics, machine learning, signal processing, data mining, etc. You can build cool systems that people use –Real, working systems that people want and need –Solving real problems (network management, anti- censorship, fighting spam, etc.) You can measure and explore –Measurement puts the science in computer science

16 Why Networking is (More) Fun Young, relatively immature field –Great if you like to make order out of chaos –Tremendous intellectual progress is still needed Defining the problem is a big part of the challenge –Recognizing a need, formulating a well-defined problem is at least as important as solving the problem. Lots of platforms for building your ideas –Programmability: Click, OpenFlow/NOX, NetFPGA –Routing software: Quagga, XORP, and Bird –Testbeds: Emulab, PlanetLab, Orbit, GENI, … –Measurements: RouteViews, traceroute, Internet2, …

17 17 Meanwhile, back in the classroom…

18 18 How Practitioners Learn Networking Certification courses –On how to configure specific pieces of equipment On the job training –Aka trial by fire

19 19 How Universities Teach Networking Undergraduates: how the Internet works Graduates: read the 20 best papers Few general principles, little hands-on experience There is a tendency in our field to believe that everything we currently use is a paragon of engineering, rather than a snapshot of our understanding at the time. We build great myths of spin about how what we have done is the only way to do it to the point that our universities now teach the flaws to students (and professors and textbook authors) who don't know better. -- John Day

20 20 How Did We Get Here? Internet design came from a different era –Single group of cooperative designers –Cohesive network –Trusted group of users The reality today is much different –Independently operated networks –Business realities (remember depeering) –Untrusted parties, often with competing goals

21 21 The Impasse How many can be easily solved? How many of these problems require fundamental change? Difficult to deploy solutions that require fundamental change.

22 22 Why We Are at an Impasse Testing new architectures is challenging –How to convince a network operator to try something out? –…especially if the change requires universal deployment Deploying new architectures is more challenging –And things are getting worse, not better Worse yet, we dont even know what those new archiectures should be (or whether they are necessary) So, we tend to teach networking courses as though the protocols, architectures, etc. are fixed. The reality is different. The network is evolving.

23 This Course: A New Approach Similar material, different organization Rather than studying layer-by-layer, we will look at different problems in networking We will study different approaches to the same problem and debate their merits Will study this in the context of different types of networks 23

24 24 Logistics Course Web page –http://www.gtnoise.net/classes/cs6250/fall_2011/http://www.gtnoise.net/classes/cs6250/fall_2011/ –Check this page regularly for updates to the syllabus, assignments, readings, etc. Course mailing list –Run through T-Square Questions to staff members (instructor, TA) –http://www.piazza.com/gatech/cs6250http://www.piazza.com/gatech/cs6250

25 Syllabus Overview 25 Introduction Transit Networks Access Networks Content and Applications Cellular & Mobile Networks Approximately two papers per lecture Read them before class Post thoughts to wiki

26 High-Level Course Structure Reading and analyzing research papers –Different ways to approach management problems –Summaries, critiques, and comparisons of the papers Lectures and Discussion –Overview of background material –Discussion and debate about the research papers (old school vs. new school) Problem Sets –Learning the platforms for evaluating your ideas –Click/Emulab, OpenFlow/NOX, and measurements Final research project –Novel research with a system-building component

27 Configuration Configuration defines the networks behavior Problem –Network configuration is low-level, vendor-specific, and error-prone –Network configuration is a significant cause of downtime Solutions –Design tools that make the network easier to manage –Refactor network design to make networks more manageable 27

28 Traffic Engineering Network operators must manage network capacity, performance, and cost Problems –Traffic is dynamic (network conditions are, too) –Determining the outcome of a configuration change is challenging Solutions –Offline tuning of configuration parameters –Online adaptation of configuration, paths, etc. 28

29 Troubleshooting Identifying the source of a problem is difficult enough… Let alone determining how to fix it! 29 Monitor x y Targets Combination of active and passive measurements Inference tools, data mining, etc. Open question: Can better architectures make troubleshooting easier?

30 Security The network is ripe for attackers who seek monetary gain, destruction, etc. Problems –Spam is 95% of all traffic –30,000+ phishing attacks every month –… Solutions –Analyze network traffic data and design better detection –Redesign the network to make these attacks more difficult to mount in the first place 30

31 Maintenance and Planning Operators must maintain high availability in the face of failures and planned maintenance Problems –Network failures can disrupt connectivity –Network resources must be reprovisioned as demands increase, etc. Solutions –Routing protocols for hitless planned maintenance –Better cost models 31

32 Other Hot Topics Programmable Hardware Configuration Languages Home Networking and Access Network Performance 32 Frequently Changing Configuration Commands

33 33 Class Components and Grading Problem sets and Labs (45%) –Hands on –First assignment will be out this week Two Quizzes (25%) –October 20 and December 1 –Covering papers and lecture material Project (30%) –Research project idea of your choosing –Should apply ideas from the class –Groups of 3-5 people –Will be adding project ideas to wiki soon

34 More Logistics… 34

35 35 Lateness Late policy: Maximum of 72 hours late throughout the term (use as you like). All problem sets and projects will be due at 11:59 p.m. on the due date. All problem sets and projects will be turned in on T-Square.

36 36 Collaboration Policy See the Georgia Tech Honor Code Sign up in groups of five to work on problem sets and projects. Use the wiki to declare your groups Working together on assignments is encouraged, but you must –turn in your own assignments –write your own code, analysis –acknowledge your collaborators

37 How to Read

38 You Spend a Lot of Time Reading Reading papers for grad classes (like this one!) Reviewing papers for conferences/journals Giving colleagues feedback on their papers Keeping up with work related to your research Staying broadly educated about the field Transitioning into a new research area Learning how to write better papers So, it is worthwhile to learn to read effectively

39 Why Read Research Papers? Read for a conference or a class Keep current in your own field Get up to speed in a new field –Learn about a sub-field (e.g., wireless) –Learn about another discipline that may offer solutions to a problem

40 Step 1: Deciding What to Read Purpose: Learn about hot topics of current research in an area. (searching for problems, etc.) Approach: Scan papers in latest conference proceedings Purpose: Get up to speed on sub-field Approach: Transitive closure of related work of papers in a top conference Purpose: Learn about an area that is further afield Approach: Ask expert colleagues

41 Step 2: Deciding How to Read Always top down –First: Abstract, introduction, conclusion –Rest of paper if necessary If you want to do follow-up research If you want to better understand the methods/conclusions Next steps depend on specific purpose

42 Reading the News Conference proceedings –Goal: Grasp main idea of a collection of a large number of papers. Keep informed about problems and recent solutions Top-Down Method –Skim table of contents: Papers are clustered intosessions which typically identify the main areas –Consider authors –Prioritize by (1) area of interest (2) reputable authors

43 How to Conduct a Literature Survey Create the seed –Recent paper from top conference –Survey paper, if one exists –Seminal paper, if it is different from the above Perform transitive closure of cited work –Read related work sections of above papers

44 Keeping Notes One-sentence summaries are infinitely better than nothing at all Primitive approach: Single file of notes Better: Database with BibTeX –There are some existing tools for bibliography management –Will also help you more quickly construct related work sections for your papers

45 Keshavs Three-Pass Approach: Step 1 A ten-minute scan to get the general idea –Title, abstract, and introduction –Section and subsection titles –Conclusion –Bibliography What to learn: the five Cs –Category: What type of paper is it? –Context: What body of work does it relate to? –Correctness: Do the assumptions seem valid? –Contributions: What are the main research contributions? –Clarity: Is the paper well-written? Decide whether to read further…

46 Keshavs Three-Pass Approach: Step 2 A more careful, one-hour reading –Read with greater care, but ignore details like proofs –Figures, diagrams, and illustrations –Mark relevant references for later reading Grasp the content of the paper –Be able to summarize the main thrust to others –Identify whether you can (or should) fully understand Decide whether to –Abandon reading the paper in any greater depth –Read background material before proceeding further –Persevere and continue on to the third pass

47 Keshavs Three-Pass Approach: Step 3 Several-hour virtual re-implementation of the work –Making the same assumptions, recreate the work –Identify the papers innovations and its failings –Identify and challenge every assumption –Think how you would present the ideas yourself –Jot down ideas for future work When should you read this carefully? –Reviewing for a conference or journal –Giving colleagues feedback on a paper –Understanding a paper closely related to your research –Deeply understanding a classic paper in the field

48 Other Tips for Reading Papers Read at the right level for what you need –Work smarter, not harder Read at the right time of day –When you are fresh, not sleepy Read in the right place –Where you are not distracted, and have enough time Read actively –With a purpose (what is your goal?) –With a pen or computer to take notes Read critically –Think, question, challenge, critique, …

49 How to Read For This Class Read critically Questions: –Is the question important? –Does this system make the right division of labor? –Is the placement of function appropriate? –Are there other disciplines that can be brought to bear on this problem? –Does the system design (or approach) make sense? 49

50 Next Three Classes: Crash Review The Host –Discovery: DNS, ARP, lookup, interconnection, naming and addressing –Resource sharing: TCP The Data Plane –Router internals: Scheduling, forwarding, packet classification, etc. –Forwarding tables, lookup, etc. The Control Plane –Spanning tree protocols, routing protocols (intradomain, interdomain, etc.) 50


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