internet routing instability offense scott crosby atul singh
TRANSCRIPT
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Internet Routing Instability
OFFENSE
Scott Crosby Atul Singh
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Critique
• Poor title
• Level of contribution
• Clarity of presentation
• Correctness
• Methodology
• Claims
• Relevance
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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
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Desirableand Necessary
TopologyPolicy
Change nothing
Route updates
Change state
Undesirable
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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
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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
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Clarity
• Figure 3– Impressive graph with ~30,000 sample points– Unreadable, unnecessary – Only discusses trends – should graph trends.
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Fig 3 : Internet forwarding instability density measure at Mae-eastExchange point during 1996.
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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?
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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?
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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
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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
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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