1 CS 268: Computer Networking L-1 Intro to Computer Networks 2 Outline • Administrivia • Layering2 3 Dramatis Personae • Professor: Randy H. Katz • Web: http://www.cs.Berkeley.edu/~randy • Facebook: http://www.facebook.com/randy.katz • Email: [email protected] • Office hours: M 3:00-4:00, W 1:00-2:00, 413 Soda Hall • Sorry, no Teaching Assistant! • Course Info • Web: http://www.cs.Berkeley.edu/~randy/Courses/CS268.F09 • Blog: http://cs268computernetworking.blogspot.com/ • Group: http://www.facebook.com/group.php?gid=145286190238 4 Goals and Objectives • Understand state-of-the-art in network protocols, architectures, and applications • Understand process of networking research • Typical constraints and thought processes used in networking research • Different from undergraduate networking (EECS 122) • i.e., training network programmers vs. training network researchers3 When Thinking About Research … “Look for what is so obvious to everyone else that it’s no longer on their radar, and put it on yours. Seek to uncover assumptions so implicit, they are no longer being questioned. Question them.” • Rodney Brooks, Co-director of CSAIL, MIT Particularly relevant advice for network research • Is the current network architecture and decisions appropriate for wireless networks, sensor networks, real-time networks, enterprise networks, datacenter networks, etc.? 6 Web Page • Check regularly!! • Course schedule • Reading list • Lecture notes • Announcements • Project ideas • Exams4 CS 268 Blog Assignments • For each lecture, you will create a “public review” of paper(s) due for that class that: • Briefly summarizes paper (1-2 paragraphs) • Provides background/related material (1-2 paragraphs) • Critiques paper and suggests discussion topics (2-3 paragraph) • Try to be positive… • Why or why not keep this paper in syllabus? • What issues are left open for future research? • What are the important implications of the work? • Select another student’s blog entry to critique before class; change each class meeting 7 8 Materials on Course Syllabus Page • Research papers • Links to pdfs on Web page • Two papers per class meeting • Combination of classic and recent work • ~40 papers • Lecture “Notes” • ppt posted, but I will minimize its in-class usage • Seminar/discussion style and participation counts! • Recommended textbooks • For those who need to review their networking background • Peterson & Davie/4ed or Kurose & Ross/4ed5 Laptop Policy • Closed Laptops! • Focus on in class discussion —this worked very well last year • I will minimize use of powerpoint myself —white board • Check your email/twitter/facebook updates at the mid-lecture break 10 Course Grading • Class + paper blog participation (20%) • Ensures you read the papers before class • Two person research project (40%) • Substantial independent research project • You learn a lot by working together • Several class meetings dedicated to projects • Two Quizzes (40%) • Closed book, in-class • Ensures you understood the papers6 11 Class Topic Coverage • Little on physical and data link layer • Little on undergraduate material • Supposedly you already know this, though some revisiting/overlap is unavoidable • Focus on the why, not the what • Focus on network to application layer • We will deal with: • Protocol rules and algorithms • Investigate protocol trade-offs • Why this way and not another? 12 Lecture Topics Traditional • Layering • Internet architecture • Routing (IP) • Transport (TCP) • Queue management (FQ, RED) • Naming (DNS) Recent Topics • Botnets • Datacenter networking • Multicast • Mobility/wireless • Network energy • Network measurement • Overlay networks • P2P applications Modified from F08 based on feedback from last year’s class: QoS, SensorNets, “Future Network” Architecture eliminated7 13 Outline • Administrivia • Layering 14 What is the Objective of Networking? • Communication between applications on different computers • Must understand application needs/demands • Traffic data rate • Traffic pattern (bursty or constant bit rate) • Traffic target (multipoint or single destination, mobile or fixed) • Delay sensitivity • Loss sensitivity8 15 Back in the Old Days… 16 Packet Switching (Internet) Packets9 17 Packet Switching • Interleave packets from different sources • Efficient: resources used on demand • Statistical multiplexing • General • Multiple types of applications • Accommodates bursty traffic • Addition of queues 18 Characteristics of Packet Switching • Store and forward • Packets are self contained units • Can use alternate paths – reordering • Contention • Congestion • Delay10 19 Internet[work] Internet[work] • A collection of interconnected networks • Host: network endpoints (computer, PDA, light switch, …) • Router: node that connects networks • Internet vs. internet 20 Challenge • Many differences between networks • Address formats • Performance – bandwidth/latency • Packet size • Loss rate/pattern/handling • Routing • How to translate between various network technologies?11 21 How To Find Nodes? Internet Computer 1 Computer 2 Need naming and routing 22 Naming What’s the IP address for www.cmu.edu? It is 128.2.11.43 Translates human readable names to logical endpoints Local DNS Server Computer 112 23 Routing R R R R R H H H H R R H R Routers send packet towards destination H: Hosts R: Routers 24 Meeting Application Demands • Reliability • Corruption • Lost packets • Flow and congestion control • Fragmentation • In-order delivery • Etc…13 25 What if the Data gets Corrupted? Internet GET windex.html GET index.html Solution: Add a checksum Problem: Data Corruption 0,9 9 6,7,8 21 4,5 7 1,2,3 6 X26 What if Network is Overloaded? Problem: Network Overload • Short bursts: buffer • What if buffer overflows? • Packets dropped • Sender adjusts
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