Computer Science 425 Distributed Systems CS 425 / CSE 424 / ECE 428 Fall 2010

1. Computer Science 425Distributed SystemsCS 425 / CSE 424 / ECE 428Fall 2010 Indranil Gupta (Indy) August 24-December 7, 2010 Lecture 1-29 Website: http://www.cs.uiuc.edu/class/fa10/cs425/  2010, I. Gupta, K. Nahrtstedt,S. Mitra,N. Vaidya, M. T. Harandi, J. Hou

2. Our First Aim in this Course was…(first lecture)…. (First lecture slide) To Define the Term Distributed System

3. Can you name some examples of Distributed Systems? (First lecture slide) • Client-Server (NFS) • The Web • The Internet • An ad-hoc network • A sensor network • DNS • Gnutella or BitTorrent (peer to peer overlays) • A datacenter, e.g., The Planet, or Amazon EC2/S3 • (The Solar System?) • (Society?) • (Food Chain?)

4. What is a Distributed System? (First lecture slide)

5. FOLDOC definition (First lecture slide) A collection of (probably heterogeneous) automata whose distribution is transparent to the user so that the system appears as one local machine. This is in contrast to a network, where the user is aware that there are several machines, and their location, storage replication, load balancing and functionality is not transparent. Distributed systems usually use some kind of client-server organization.

6. Textbook definitions (First lecture slide) • A distributed system is a collection of independent computers that appear to the users of the system as a single computer [Andrew Tanenbaum] • A distributed system is several computers doing something together. Thus, a distributed system has three primary characteristics: multiple computers, interconnections, and shared state [Michael Schroeder]

7. A working definition for us (First lecture slide) A distributed system is a collection of entities, each of which is autonomous, programmable, asynchronous and failure-prone, and communicating through an unreliable communication medium. • Our interest in distributed systems involves • design and implementation, maintenance, study, algorithmics • Entity=a process on a device (PC, PDA) • Communication Medium=Wired or wireless network • What Evidence/Examples have we seen?

8. Problems we have Seen and Solved Since Then • Failure Detectors • Time and Synchronization • Global States and Snapshots • Multicast Communications • Mutual Exclusion • Leader Election • Impossibility of Consensus • Peer to peer systems – Gnutella and Chord • Cloud Computing • Networking and Routing • Sensor Networks • Measurements from real systems

9. Problems we have Seen and Solved in this Class • Failure Detectors • Time and Synchronization • Global States and Snapshots • Multicast Communications • Mutual Exclusion • Leader Election • Impossibility of Consensus • Peer to peer systems – Gnutella and Chord • Cloud Computing • Networking and Routing • Sensor Networks • Measurements from real systems Basic Theoretical Concepts Bridge to Systems What Lies Beneath

10. Problems we have Seen and Solved in this Class (2) • RPCs & Distributed Objects • Concurrency Control • Replication Control • Gossiping • Self-stabilization • Distributed File Systems • Distributed Shared Memory • Byzantine Fault-tolerance • Security Basic Building Blocks Distributed Services (e.g., databases) Basic Theoretical Concepts Distributed Apps that people use directly Easy programming Necessary properties

11. Problems we have Seen and Solved in this Class (3) How to get good grades (and regrades, and jobs in some cases) • Midterm • HW’s and MP’s • A new cloud computing application from scratch! Something to boast about to your friends (and in interviews!)

12. A range of Challenges for Designers (First lecture slide) • Heterogeneity • Openness • Security • Scalability • Failures • Concurrency • Transparency What are these?

13. What we Have Learned Since Then • Heterogeneity – protocols should run in spite of heterogeneous nodes, e.g., supernodes in Kazaa, variety of nodes in a cloud • Openness – each service/protocol can build on other services/protocols, e.g., layered or stacked architecture • Security – it should be possible to add-in security to any existing protocol/system, e.g., encryption and signatures • Scalability – clouds and peer to peer systems need to scale in overhead as the size of the system increases • Failures – any protocol should be tolerant to the failure of nodes and of communication • Concurrency – the more this is, the better the performance, but is a tradeoff with consistency requirements • Transparency – clouds, distributed file systems, transactions, virtual synchrony, sequential consistency, etc. provide an abstraction of one property while allowing sufficient flexibility at run-time

14. Problems we have Seen and Solved in this Class(and relation to other courses) Core Material of this course • Failure Detectors • Time and Synchronization • Global States and Snapshots • Multicast Communications • Mutual Exclusion • Leader Election • Impossibility of Consensus • Peer to peer systems – Gnutella and Chord • Cloud Computing • Measurements from real systems • Networking and Routing • Sensor Networks Related to CS 525 Related to CS 438

15. Problems we have Seen and Solved in this Class (and relation to other courses) Core Material of this course • RPCs & Distributed Objects • Concurrency Control • Replication Control • Gossiping • Self-stabilization • Distributed File Systems • Distributed Shared Memory • Byzantine Fault-tolerance • Security Related to CS 411/CS 511 Related to CS 525 Related to CS 423/CS 523 Related to CS 421/CS 433 Related to CS 523

16. Problems we have Seen and Solved in this Class (and relation to other courses) Related to all courses • Midterm • HW’s and MP’s

17. CS525: Advanced Distributed Systems(taught by Indy) CS 525, Spring 2011 • Looks at hot topics of research in distributed systems: clouds, p2p, sensor networks, and other distributed systems • If you liked CS425’s material, it’s likely you’ll enjoy CS525 • Project: Spring 2011 is a special “Entrepreneurial” semester for CS525 • Your project will build a distributed system for a new startup company idea (your own!) and perform associated research with it • You (as student) own IP for your project!  you can found your own company (if you so wish) based on your CS525 project • Space is limited, so please sign up soon! • Both graduates and undergraduates welcome! (let me know if you need my consent). • Class size is around 20-30

18. Questions?

19. A working definition for us A distributed system is a collection of entities, each of which is autonomous, programmable, asynchronous and failure-prone, and communicating through an unreliable communication medium. • Our interest in distributed systems involves • design and implementation, maintenance, study, algorithmics • Entity=a process on a device (PC, PDA) • Communication Medium=Wired or wireless network [Is this definition still ok, or would you want to change it?]

20. Etc. • Regular TA (Imranul) office hours on Wed Dec 8 and special office hours on Thursday (10.30am-12noon). • Indy’s office hours – none this Thursday, special office hours this Friday 4pm-5pm (Dec 10). • Final Exam • MONDAY Dec 13 1:30-4:30pm MEB 253. Includes all material since the start of the course • Allowed to bring a cheat sheet to the exam (A4 size, two sides only, at least 1 pt font) • Final will be similar in structure to Midterm • Revising homework problems, and midterm problems, (and if possible other problems in the textbook) will be ample preparation for the final exam

21. Course Evaluation • Main purpose: to give us feedback on how useful this course was to you (and to improve future versions of the course) • I won’t see these evaluations until after you see your grades • Use pencil only • Make sure you answer 1 and 2 (You may omit item 5 about student gender (top box)). • Please write your detailed feedback on the back – this is valuable for future versions of the course! • Need a volunteer: • Please collect all reviews, and drop envelope in campus mail box • Return the box of pencils to Siebel Center Academic Office (beside 1st floor elevator)

22. Thank You