14-Designingin90 - Designing the Internet in 75 Minutes....

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1 Designing the Internet in 75 Minutes…. EE122 Fall 2011 Scott Shenker http://inst.eecs.berkeley.edu/~ee122/ Materials with thanks to Jennifer Rexford, Ion Stoica, Vern Paxson and other colleagues at Princeton and UC Berkeley
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Grading the Homeworks • Going very slowly, my apologies • Two graders, trying to work out inconsistencies 2
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The Midterm • Average score ~106 (80%) • Will be handed back at end class • Key will be published soon – A few stragglers… • Regrading requests: – Sent to me (not TAs) – Cover sheet explaining why you think you deserve credit – Regrade will be over entire test c (except for two cases mentioned later) 3
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Problems 1 and 2 • Overall, scores reasonably high 4
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Problem 3 • IPv6 headers the most frequently missed question • IP checksum is only over header The key was wrong on this, so it was misgraded! – Answer should be “none of the above” Submit a regrade (1/2 point) • DHCP all broadcast (I said “know this”) • Order of packet headers – Not sure if you don’t know, or if question was unclear – Learn this for final…. • Packet from NAT to A should not have NAT’s address in the source field 5
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Problem 4 • More mistakes on startup than on tear-down • DNS should come first, then TCP. 6
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Problem 5 • If packet arrives on port where switch would forward packet, switch drops it 7
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Problem 6 • Justine, in a few minutes 8
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Problem 7 • Class did quite well, some minor problems 9
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Problem 8 • Most common mistake: – The prefixes to port 6 • Many people didn’t have a clue….( get one for final ) • The hardest problem to grade – Partial credit was difficult to assess Ask for a regrade if your prefixes were close to right, but I didn’t give you much credit 10
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SPLIT HORIZON + POISON REVERSE Never announce a path back to the node you got it from.
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! ! ! ! ! ! ! ! ! ! ! ! ! ! ! 4 B’s path to A: BDEA B announces “6” to C.
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! ! ! ! ! ! ! ! ! ! ! ! ! ! ! 4 B’s path to A: BCDEA B announces ” to C.
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SPLIT HORIZON + POISON REVERSE Never announce a path back to the node you got it from.
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Beanbags….
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This note was uploaded on 01/09/2012 for the course ELECTRICAL 122 taught by Professor Shenker during the Spring '11 term at University of California, Berkeley.

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14-Designingin90 - Designing the Internet in 75 Minutes....

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