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CSE561Spring 2001
Venkat Padmanabhan 1
CSE561: Graduate Computer Networking
Venkat PadmanabhanMicrosoft Research
CSE561Spring 2001
Venkat Padmanabhan 2
Prelimaries
Instructor: Venkat PadmanabhanEmail: [email protected]: MF, 12:00-1:20 PM, EE1 003Office hours: MF 1:30-2:00 PM, Sieg 226DTA: Andrew WhitakerEmail: [email protected] hours: Th 2:30-3:30 PM, Sieg 433Home page:
http://www.cs.washington.edu/education/courses/561/01sp/
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What’s this class about?
• Reading 25-30 papers spanning a wide spectrum of the networking research literature
• Learning how to critique networking research
• Learning how to do networking research through a hands-on project
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Am I ready to take this class?
• If you have taken CSE 461 or an equivalent undergraduate class elsewhere, then you’re all set.
• If you haven’t but have at least some background in computer systems, you can read through a basic textbook (e.g., the book by Peterson & Davie) without much effort.
• Minimal coverage of basic material in class
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Syllabus
Focus on the Internet-related research• Design philosophy and architecture• Medium access control (Ethernet, wireless)• Routing (BGP)• Transport (TCP)• Applications (Web/HTTP, audio/video)• Novel paradigms (multicast, active networks)• Novel networks (wireless, mobile)• Security (protocol vulnerability, DoS attacks)
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What you are expected to do
• Read and review research papers (20%)
• Actively participate in discussions in class and on the mailing list (10%)
• Take midterm exam (20%)• Define and work on a networking
research project (50%)
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Literature Review
• 25-30 research papers– all available online on the course home page– only need to review papers marked as such– “optional reading” need not be reviewed
• Review (one page max per paper)– summarize paper in just a few sentences– highlight contributions/lessons learned– point out shortcomings in assumptions, approach,
data, etc. (ignore presentation problems!)– bonus points for comparing and contrasting with
related literature (from reading list or elsewhere)
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Literature Review (contd.)
• Reviews– OK to discuss papers with others at any
time– But you must write your own review!– Hardcopy due at the start of each
lecture– You may choose to post your review on
the mailing list after the lecture period to get some discussion going
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Class Participation
• Read the papers before coming to class
• Actively participate in discussion in class and on the mailing list
• Remember: there are few absolute truths in networking. So don’t be afraid to be a contrarian.
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Mid-term Exam
• Scheduled for Friday, May 11• Focus on understanding rather than
the knowledge of facts
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Project
• Define and work on a research project that– is interesting– explores novel issues or approaches– is doable in the available time
• Groups of 2-3 students (not a rule)• You are encouraged to come up with ideas
– feel free to brainstorm on ideas with others– aim high! The best projects could lead to papers
at the top conferences (SIGCOMM,Infocom,Mobicom)
– I’ll distribute a list of potential projects in class next week
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Project (contd.)
• Project scope– implementation, simulation, measurement,
analysis, or some combination thereof– this is not about doing a literature survey
• The process– initial meeting (April 6)– 1-2 page project proposal due April 13
• problem statement, specific goals, resources you need, plan of attack, (anticipated) deliverables
• not a rigid document
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Project (contd.)
• The process (contd.)– checkpoint meetings after class on May
7– project presentations and final report
due the first week of June (exact date TBD)
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Elements of a Network
• Links carry information (bits)– Wire, wireless, fiber optic, smoke signals
…
• Switches move bits between links– Routers, gateways, bridges, CATV
headend, PABXs, …
• Hosts are the communication endpoints– PC, PDA, cell phone, toaster, …
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Example – Local Area Network
• Your home network– Ethernet is a broadcast-capable multi-access
LAN
CableModem
PC Laptop
Printer
EthernetHub
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Example – An Internetwork
• Internetwork is a network of networks• The Internet is a global internetwork in
which all participants speak a common language, IP.
LocalNet 2
LocalNet 1
ISP 2 ISP 1
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Key Features of the Internet
• Distributed– decentralized operation, global reach
• Large-scale– 110 million hosts (Jan 2001) and growing
• Heterogeneous– links, end-points
• Intelligent end-points– supercomputers, PCs, PDAs
• Multi-purpose– Web, audio/video conferencing, telnet
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Network Components
Say you want download a file from host A onto host B.
What problems do you need to solve?
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Host Discovery
Locating the remote host
• The “naming” problem– provides a level of indirection between
names and addresses
• Domain Name System (DNS)– the “telephone directory” of the Internet
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Medium Access Control
Putting bits on the wire• The network carries packets, not bits
– framing to create packets out of bits
• Physical medium may be shared– example: Ethernet, wireless– medium access control (MAC) to arbitrate
amongst several contenders
• Actually, the network only carries electrical or optical signals– modulation to convert digital data into analog
signals
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Routing
How do a packet find its way through the network?
• Internet is distributed– no central “brain”– routing happens in a decentralized manner
• Internet is not owned by any one organization– hierarchical routing architecture– intra-domain and inter-domain
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Transport Protocol
How do you ensure reliable transmission of the file over an unreliable network?
• Links and routers are a shared resource– a packet may be dropped when the resource is
over-utilized (or even otherwise!)– resources need to be apportioned “fairly”
• Need to perform loss recovery and congestion control
• Transmission Control Protocol (TCP)– responsible the vast majority of Internet traffic
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Interaction of Transport Protocols with Applications
One size doesn’t fit all• Transfer size
– a protocol designed for large file transfers may be too heavyweight for exchanging short messages
• Reliability– necessary for ordinary file transfer– not necessary for live streaming audio
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Multicast
Several clients may want to download a file at the same time
• Repeated unicast would be inefficient• Need to multicast the file
– avoid sending a packet over a link repeatedly
• Multicast makes existing problems harder, especially because of heterogeneity– routing– loss recovery– congestion control
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Resource Discovery
Say you have a choice of where to download the file from
• Best to download it from “nearest” source– this is exactly the goal of content
distribution networks (e.g., Akamai)
• But Internet “distance” is not a static metric and is hard to measure
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Security
It ain’t a friendly world out there!• Eavesdropping on conversations• Masquerading as another entity
– man-in-the-middle attack
• Non-compliance with the protocols• Deliberate overconsumption of
resources– denial of service attack
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Mobility
Hosts and/or networks may be mobile• Examples:
– a person carrying a laptop from work to home– a planeload of people
• Maintaining Internet connectivity in the face of mobility– mobility impacts most of the other components
(discovery, routing, transport, applications, security)
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Lecture Roadmap
1. Internet design principles and architecture
2. Medium Access Control3. Internet routing4. Router architectures5. Transport protocols: congestion control6. Transport protocols: interaction with
applications7. Router support for congestion control8. Multicast routing
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Lecture Roadmap (contd.)
9. Multicast transport and applications10.Naming11.Resource discovery and selection12.Host and network mobility13.Wireless networks (medium access
control)14.Wireless networks (TCP interactions)15.Network and protocol vulnerability16.Active networks
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Topics Not Covered
• Quality of service• Real-time communication• Traffic measurement and analysis• Ad-hoc networks• … and many others
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Next Lecture: Internet Design Principles and Architecture
• History and evolution of the Internet• Current architecture• Defining principles:
– layering– datagram service– statistical multiplexing– decentralized architecture – end-to-end principle
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Next Lecture (contd.)
• Papers to read– D. Clark,
The Design Philosophy of the DARPA Internet Protocols, ACM SIGCOMM 1988
– .H. Saltzer, D.P. Reed, D.D. Clark, End-to-End Arguments in System Design, ACM TOCS, November 1984
• The optional papers are also classics!• No reviews due