u What about flaky equipment going up and down u Determining the cause of

U what about flaky equipment going up and down u

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u What about flaky equipment going up and down? u Determining the cause of persistent loops? Anecdote on recent study of persistent loops u Provider has static route for customer prefix u Customer has default route to the provider CSE 222A – Lecture 4: Routing
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Pathology type Prevalence in 1995 Prevalence in 1996 Long-lived Routing loops Short-lived Routing loops Outage>30s Total 0.065% ~ 0.14% ~ same same 0.96% 2.2% 3.4% 1.5% End - to - End Routing Behavior 7 CSE 222A – Lecture 4: Routing
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Paxson Study: Path Fluttering Rapid changes between paths u Multiple paths between a pair of hosts u Load balancing policies inside the network Packet-based load balancing u Round-robin or random u Multiple paths for packets in a single flow Flow-based load balancing u Hash of some fields in the packet header u E.g., IP addresses, port numbers, etc. u To keep packets in a flow on one path CSE 222A – Lecture 4: Routing
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Paxson Study: Routing Stability Route prevalence u Likelihood of observing a particular route u Relatively easy to measure with sound sampling u Poisson arrivals see time averages (PASTA) u Most host pairs have a dominant route Route persistence u How long a route endures before a change u Much harder to measure through active probes u Look for cases of multiple observations u Typical host pair has path persistence of a week CSE 222A – Lecture 4: Routing
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Paxson Study: Route Asymmetry Hot-potato routing Other causes u Asymmetric link weights in intradomain routing u Cold-potato routing, where AS requests traffic enter at particular place Consequences u Lots of asymmetry u One-way delay is not necessarily half of the round-trip time Customer A Customer B multiple peering points Provider A Provider B Early-exit routing
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  • Fall '08
  • Vahdat,A
  • Paxson

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