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Internet Routing Instability

Internet Routing Instability. OFFENSE Scott Crosby Atul Singh. Critique. Poor title Level of contribution Clarity of presentation Correctness Methodology Claims Relevance. Poor Title. Not about stability But, its about routing traffic

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Internet Routing Instability

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  1. Internet Routing Instability OFFENSE Scott Crosby Atul Singh

  2. Critique • Poor title • Level of contribution • Clarity of presentation • Correctness • Methodology • Claims • Relevance

  3. Poor Title • Not about stability • But, its about routing traffic • Doesn’t tell desirable updates from undesirable updates • Better title : Characterization of BGP routing traffic

  4. Route updates Change state Change nothing Desirable and Necessary Undesirable Policy Topology

  5. Contribution • Measurement results must be clear for this to be a contribution • Most paths are stable • Already known from Paxon[96] • Free debugging • bad implementations • vendor screw ups

  6. Clarity • Figure 2 • Only shows 10% of the picture – Where is WWDup? • Appears uncorrected for missing data • Useless to estimate true distribution • Can’t eyeball ratio of different categories

  7. Clarity • Figure 3 • Impressive graph with ~30,000 sample points • Unreadable, unnecessary • Only discusses trends – should graph trends.

  8. Fig 3 : Internet forwarding instability density measure at Mae-east Exchange point during 1996.

  9. Correctness • '99% of routing messages are pathological'? • No data to backup their claim • Analysis of routing messages • Where’s the table of the number of each type? • Where’s the table estimating the number of unnecessary routing messages?

  10. Methodology • Only 5 sites, why is that enough? • Discount private exchanges • Do the instabilities actually effect performance? • Claim yes, but no evidence • Ugliness is not a crime • Uses prefix-pair tuple • How to deal with aggregation?

  11. Claims • ‘routing instability contributes to poor end-to-end performance?’ • Paxon[96] paper shows 1% problems • ‘high levels of instability can lead to packet loss’ • Paxon[96] shows this is rare • Unverified

  12. Relevance • Does instability matter? • If the network changes, it changes • A network with static routes would be perfectly stable • But not robust • Debug vendor X’s code • Obsolescent • new routers contain a full forwarding table in RAM • Care about end-to-end performance

  13. It’s a dirty job to critique but someone had to do it • Poor title • Level of contribution • Clarity of presentation • Correctness • Methodology • Claims • Relevance

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