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Eliminating Packet Loss Caused by BGP Convergence

Eliminating Packet Loss Caused by BGP Convergence. Nate Kushman Srikanth Kandula, Dina Katabi, and Bruce Maggs. The Problem:. BGP Convergence Causes You Packet Loss. Route changes cause up to 30% packet loss for more than 2 minutes [Labovitz00]

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Eliminating Packet Loss Caused by BGP Convergence

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  1. Eliminating Packet Loss Caused by BGP Convergence Nate Kushman Srikanth Kandula, Dina Katabi,and Bruce Maggs

  2. The Problem: BGP Convergence Causes You Packet Loss • Route changes cause up to 30% packet loss for more than 2 minutes [Labovitz00] • Even for domains dual homed to tier 1 providers, a failover event can cause multiple loss bursts, and one loss burst can last for up to 20s [Wang06] • Popular and unpopular prefixes experience losses due to BGP convergence [Wang05] • 50% of VoIP disruptions are highly correlated with BGP updates [Kushman06]

  3. What Kind of Solution Do We Want? • Eliminate packet loss during BGP convergence • An adopting ISP protects itself and its customers from loss even if no other ISP cooperates

  4. Transient Path Loss Problem AT&T Sprint Avi All of Patrick’s providers are using him to get to MIT Patrick Nobody offers Patrick an alternate path MIT

  5. Link Down Transient Path Loss Problem AT&T Sprint Avi Patrick knows no alternate path to MIT Patrick drops AT&T’s and Avi’s packets to MIT, and his own Patrick LOSS! MIT

  6. Link Down Transient Path Loss Problem Eventually, Patrick withdraws path from AT&T and Avi AT&T Sprint Avi AT&T and Avi stop sending packets to Patrick Patrick MIT

  7. Link Down Transient Path Loss Problem Eventually, Patrick withdraws path from AT&T and Avi AT&T Sprint Avi AT&T and Avi stop sending packets to Patrick AT&T announces the Sprint path to Patrick  Traffic flows Patrick Temporary Packet Loss MIT Significant loss happens in today’s Internet, even when connected to Tier 1s

  8. How do we solve Patrick’s problem? Tell Patrick a failover path before the link fails rather than after it, as is often the case in current BGP

  9. Link Down Help Patrick Help You! AT&T advertises to Patrick “AT&T Sprint  MIT” as a failover path Avi AT&T Sprint Link Fails  Patrick immediately sends traffic on failover path Patrick No Loss ! MIT

  10. Our Solution: Two Simple Rules Routing Rule: Each router advertises only one failover path and only to the next hop router on its primary path Forwarding Rule: When routers receive packets from the next-hop interface for their primary path they forward them along the failover path

  11. Guarantee:A router is guaranteed to see no BGP-caused packet loss during convergence, if it will have a valley-free path to the destination at convergence

  12. Link Down Helps Even When Deployed in a Single AS Currently Patrick drops packets even if he knows an alternate path Patrick R1 offers Failover path to R2 R1 Joe R2 U-turns packets – back to R1 R2 No Loss ! To MIT MIT

  13. Experimental Results • Router-Level Simulation over the full Internet • AS-graph from Routeviews and RIPE BGP Data • Use inference algorithms to annotate links with customer-provider or peer relationships • Add border routers based on the connections to other AS • Used internal MRAI of 5s and external MRAI of 30s • For each experiment: • Random destination • Take down a Random Link • Find the duration of packet loss for routers using the down link which have a path after convergence • Run for 1000 Randomly Chosen Links and Destinations

  14. Significant Benefit Running Only in AT&T Fraction of Routers Duration of Packet Loss in Seconds ~20% See 30s or More of Packet Loss

  15. Significant Benefit Running Only in AT&T Fraction of Routers Duration of Packet Loss in Seconds Setting MRAI to 0 still leaves Significant Packet Loss Twice the Number of Updates for Both AT&T and Customers

  16. Significant Benefit Running Only in AT&T Fraction of Routers Duration of Packet Loss in Seconds Less than 3% if only AT&T adopts

  17. Full Benefit Once Running Everywhere Fraction of Routers Duration of Packet Loss in Seconds Running Everywhere Eliminates All Packet Loss

  18. Little Additional Overhead 325K 312K Less than 5% more updates network wide

  19. Conclusion • Offer a failover path only to next-hop neighbor • Eliminates packet loss resulting from BGP convergence • An adopting ISP reduces loss even if no other ISP cooperates • Simple Mechanism • Solves Problem • Deployable

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