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Summary of Lecture on Network Fundamentals and Papers Review in CS 4700/CS 5700

This lecture summary covers key topics from the Physical and Link Layers, including bit movement, synchronization, framing, and error detection. It discusses collision avoidance techniques in wired and wireless networks, as well as key concepts about media access control. The lecture also reviews significant papers on spanning trees and intradomain routing, highlighting important findings like loop-free assumptions, low memory use, and quick convergence. Additionally, it touches on real-time monitoring, operator challenges, and common network issues like message storms and router bugs.

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Summary of Lecture on Network Fundamentals and Papers Review in CS 4700/CS 5700

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  1. Lecture 7.5: Summary from Lecture 2 CS 4700 / CS 5700Network Fundamentals Revised 1/25/2014

  2. Project 1 in, Project 2 out • Project 1 will be graded this week • Project 2 • Any questions?

  3. Summary from last class • Physical layer • Move bits around • Synchronize to determine when bits start/end • Link Layer • Framing • Error detection • Media Access Control • Collision Avoidance/Detection • Wired/Wireless (sensing/DCF) • Hubs, switches, bridges and spanning trees

  4. Today’s class • Paper reviews • Spanning Tree • OSPF in operational networks • Network layer • Addressing • Routing • Packet delivery • Intradomain routing • Next week: Interdomain routing

  5. Perlman paper • This paper won her a SIGCOMM award in 2010 • Key take-aways • Not reasonable to assume topologies are loop free, and we need a way to route between LANs automatically • Low memory consumption • Scalable bandwidth consumption • Converges quickly • Tunable

  6. Perlman paper (2) • Implementation details • Timers everywhere • How else do we know when a link is down? • Also can prevent transient loops (hold down) • Loop detection/avoidance • This comes up often in networking • Deterministic behavior • Allows operators to reason about changes • Very hard to do in wide area! • Compare this with BGP when we get to it

  7. Shaikh paper • Key take-aways • Understanding the state of large-scale networks is hard • Especially when they are self-managing • Best way to monitor is to participate in the protocol • Real time is critical, so separation of functionality is critical • Offline vs online analysis • Must not adversely affect the network • Modeling the network allows us to identify anomalies • Flaps • Message storms • Etc

  8. Shaikhpaper (2) • Networking and operators • Operators are extremely cautious people • Tend to lack good tools for understanding the network • Routers are not perfect • Router bugs, flapping due to load, improper timers • Generally hard to detect if you’re not looking for it • Humans are definitely not perfect • Bad configs, e.g.

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