lecture 1: course introduction - university of california,...
TRANSCRIPT
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Lecture 1:Course Introduction"
CSE 222A: Computer Communication Networks Alex C. Snoeren
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Lecture 1 Overview" Class overview
◆ Expected outcomes ◆ Structure of the course ◆ Policies and procedures
A brief review of undergrad networking ◆ High-level concepts ◆ An end-to-end example
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CSE 222A – Lecture 1: Course Introduction" 3
Logistics" Instructor: Alex C. Snoeren
◆ Office hours Tuesdays 11-12pm or by appointment ◆ EBU3B 3114
TA: Siva Radhakrishnan ◆ Office hours Wed 1-3pm EBU3B B240A
Course Web page: ◆ http://www.cs.ucsd.edu/classes/wi13/cse222A-a/ ◆ Piazza is only for Q&A
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Prereqs" Undergrad networking course (e.g., CSE123)
◆ You are welcome to take the course without prior background, ◆ But, several parts of the course will be especially challenging
» You are responsible for doing the extra reading on your own » Peterson & Davie are your friends—our undergrad textbook
Systems programming experience ◆ The term project will likely require significant implementation ◆ This course will not teach you systems programming. The TA
will help, but you need to learn it on your own if you don’t already know it.
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Expected Outcomes" This course will teach you about network architecture
◆ We will cover some classic literature for background ◆ Focus mostly on recent developments in the field
This course will not teach you the fundamentals ◆ Layering, signaling, framing, MAC, switching, routing, naming,
Internetworking, congestion control, router design, etc. ◆ Take the undergrad course for the basics
Similarly, we will not cover Web/Cloud services ◆ CSE223B covers distributed systems design, the “cloud,” etc. ◆ You will be able to pick this up on your own with Google
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CSE 222A Class Overview" Course material taught through class lectures, paper
readings, and term project ◆ Lectures are interactive—attendance is crucial to success
Course grade based upon: ◆ Daily paper reviews ◆ In-class quiz at end of term (based on lectures/readings) ◆ Term project with paper and presentation
Piazza discussion forums ◆ The place to ask questions about lecture, papers, project, etc. ◆ My first time using it, so please let me know if it’s broken!
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Textbook" Peterson and Davie, Computer Networks: A systems
Approach, Morgan Kaufmann, 5th Edition, ISBN 978-0-12-385059-1
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Paper reviews" Written critique of each assigned reading
◆ Submitted in advance of each class through an automated conference review system (HotCRP)
◆ What are the biggest contributions of the paper? ◆ What are the main shortcomings/issues with the work? ◆ What are the implications of the described work?
You should read others’ reviews ◆ Help you see other points of view ◆ Available after you submit your review
Graded on a 3-point scale ◆ Our expectations will go up as the term progresses
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Term Project" Group project; teams of 2-3 people
◆ Your chance to explore what networking research is like ◆ The very best projects can—and do—result in publications
List of project ideas on course Website ◆ Will be posted shortly
Several milestones to keep you on track ◆ Topics of interest due Jan 22nd. ◆ Teams formed January 24th. ◆ Project proposal due February 5th.
Final exam period will be a mini conference ◆ You will prepare a report and a presentation
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Grading" Paper reviews: 15%
Quiz: 35%
Project: 40%
Participation: 10% ◆ Attendance and engagement in class discussion is crucial
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Questions" Before we start the material, any questions about the
class structure, contents, etc.?
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Networking in One Slide" Protocols & Layering
◆ Manage complexity by decomposing the tasks ◆ Standardizing syntax and semantics to support interoperability
Naming ◆ Agreeing on how to describe a host, application, network, etc.
Switching & Routing ◆ Deciding how to get from here to there ◆ Forwarding messages across multiple physical components
Resource Allocation ◆ Figuring out how to share finite bandwidth, memory, etc.
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A “Simple” Task" Send information from one computer to another
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Link
Endpoints are called hosts ◆ Could be computer, iPod, cel lphone, etc.
The plumbing is called a link ◆ We don’t care what the physical technology is:
Ethernet, wireless, cellular, etc.
Host Host
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Measures of success" How fast?
◆ Bandwidth measured in bits per second ◆ Often talk about KBps or Mbps – Bytes vs bits
How long was the wait? ◆ Delay (one-way or round trip) measured in seconds
How efficiently? ◆ Overhead measured in bits or seconds or cycles or…
Any mistakes? ◆ Error rate measured in terms of probability of flipped bit
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How long to send a message?" Transmit time T = M/R + D
◆ 10 Mbps Ethernet LAN (M=1KB) » M/R=1ms, D ~=5us
◆ 155 Mbps cross country ATM link (M=1KB) » M/R = 50us, D ~= 40-100ms
Where are the bits in the mean time? ◆ In transit inside the network
R*D is called the bandwidth delay product ◆ How many bits can be “stored” be stored in transit ◆ Colloquially, we say “fill the pipe”
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Is Not Really So Simple"
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UCSD
CENIC
Sprint
Quest
AT&T
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Layering: A Modular Approach" Sub-divide the problem
◆ Each layer relies on services from layer below ◆ Each layer exports services to layer above
Interface between layers defines interaction ◆ Hides implementation details ◆ Layers can change without disturbing other layers
Interface among peers in a layer is a protocol ◆ If peers speak same protocol, they can interoperate
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Protocol Standardization" Communicating hosts speaking the same protocol
◆ Standardization to enable multiple implementations ◆ Or, the same folks have to write all the software
Internet Engineering Task Force ◆ Based on working groups that focus on specific issues ◆ Produces “Request For Comments” (RFCs)
» Rough consensus and running code » After enough time passes, promoted to Internet Standards
Other standards bodies exist ◆ ISO, ITU, IEEE, etc.
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TCP/IP Protocol Stack"
HTTP
TCP
IP
Ethernet interface
HTTP
TCP
IP
Ethernet interface
IP IP
Ethernet interface
Ethernet interface
SONET interface
SONET interface
host host
router router
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Application Layer
Transport Layer
Network Layer
Link Layer
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Encapsulation"
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HTTP
TCP
IP
Ethernet interface
HTTP
TCP
IP
Ethernet interface
Payload
Headers
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Data Link
Physical
Applications
The Hourglass Model
“Thin Waist”
FTP HTTP TFTP NV
TCP UDP
IP
NET1 NET2 NETn …
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Transport
Internet Protocol Suite"
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Physical layer"802.11b Wireless Access Point
Ethernet switch/router
To campus backbone
2.4Ghz Radio DS/FH Radio (1-11Mbps)
Cat5 Cable (4 wires) 100Base TX Ethernet 100Mbps
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Link Layer (e.g. Ethernet)" Break message into frames Media Access Control (MAC)
◆ Can I send now? Can I send now?
Send frame
Receiver
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Connecting links" Routers/Switches: moves bits between links
◆ Circuit switching: guaranteed channel for a session (Telephone system)
◆ Packet switching: statistical multiplexing of independent pieces of data (Internet)
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Putting this all together" ROUGHLY, what happens when I click on a Web page
from UCSD?
www.google.com
? My computer
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Internet
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Web request (HTTP)" Turn click into HTTP request
GET http://www.google.com/ HTTP/1.1 Host: www.google.com Connection:keep-alive …
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Name resolution (DNS)"
Where is www.google.com?
What’s the address for www.google.com
My computer (132.239.9.64)
Oh, you can find it at 66.102.7.104
Local DNS server (132.239.51.18)
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Data transport (TCP)" Break message into packets (TCP segments) Should be delivered reliably & in-order
GET http://www.google.com HTTP/1.1 Host: www.google.com Connection:keep-alive …
GET htt 1 p://www. 2 google.c 3
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Global Network Addressing" Address each packet so it can traverse network and
arrive at host
My computer (132.239.9.64)
www.google.com (66.102.7.104)
GET htt 1 66.102.7.104 132.239.9.64
Destination Source Data
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Resource Allocation: Queues"
Sharing access to limited resources ◆ E.g., a link with fixed service rate
Simplest case: first-in-first out queue ◆ Queue/serve packets in the order they arrive ◆ Drop packets when the queue is full
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For Next Class…" Browse the course web
◆ http://www.cs.ucsd.edu/classes/sp13/cse222A-a/
Read P&D Chapters 1 and 2
Read and review Saltzer, Reed, and Clark ’84 ◆ Submit review in HotCRP – available by tomorrow
Start thinking about term project ideas/groups ◆ Suggestions available later this week