Traffic-aware Inter-Domain Routing for Improved Internet Routing Stability

Zhenhai Duan

Florida State University

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Outline

• Introduction and Background

• Motivation and Intuition

• Traffic-Aware Inter-Domain Routing (TIDR)

• Performance Studies

• Summary

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Introduction and Background

• Internet consists of large number of network domains – Or Autonomous Systems (ASes)– Currently about 26K– Exchange network prefix reachability information using BGP

• In a system this big, things happen all the time– Fiber cuts, equipment outages, operator errors

• Direct consequence on routing system– Large number of BGP updates exchanged between ASes– Re-computing/propagating best routes– Events may propagated through entire Internet

• Effects on user-perceived network performance– Long network delay, packet loss, even loss of network connectivity

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Introduction and Background

• Implicit design assumption in BGP– Failure events of same importance to all users

• No explicit mechanisms to localize failure in BGP

• Internet global reachability == global propagation of failure– Is this valid?– A user (AS) in US may not be interested in failure in Asian country

• Design of BGP failed to recognize two Internet properties– Internet access non-uniformity– Prevalence of transient failures

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Motivation and Intuition

• Internet access non-uniformity– APRANET(1970, Kleinrok and Naylor)

• Top 12.6% responsible for 90% of traffic

– NSFNET(1980,Rekhter and Chinoy)• Top 10% responsible for 85% of traffic

– Fang and Peterson (1999), and Rexford(2002)• Non-uniform distribution nature of Internet traffic

• Model on network value [IEEE/SPECTRUM2006]– Zipf’s law

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Internet Access Non-Uniformity

• FSU Study– Study if Internet access locality holds from viewpoint of edge network– Bidirectional data traffic collected at border router at FSU for 16 days

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FSU Data Traffic on other Days

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BGP Updates (RouteViews Project)

Most of updates are from rest of the prefixes

Only a few updates are related to top prefixes at FSU

Motivation and Intuition

• Prevalence of transient failures– Sprint backbone measurement (2002)– BGP misconfigurations

• 50% misconfigurations lasted less than 10 minutes

• 50% < 1 minute• 80% < 10 minutes• 90% < 20 minutes

Majority of network failures are transient 9

Motivation and Intuition

Internet Access Non-Uniformity

Users (networks) normally communicates with small set of other network domains

Prevalence of Transient Failure

Majority of the network failures on the Internet are transient

TIDR

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Traffic-aware Inter-Domain Routing (TIDR)

• Prefix classified into either significant or insignificant– At AS v, with respect to neighbor n

• Treat differently propagation of sign/insign prefixes– Propagating BGP updates of sign prefixes with high priority– Aggressively slow down propagation of BGP updates of insign prefixes

• Localizing effect of transient failures on insign prefixes– Hold propagation of transient failures if valid alternative route exists

• BGP withdrawals always propagated

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vv

Insignificant

Significant

nn

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TIDR Timers

15/30SEC.

MRAI TIMER

ASAS1010MIN.MIN.

TIDR TIMER

Recovery

TIDR Design

• How to avoid traffic black-holes?– If the alternative route that is held by Timer is invalid, node will be the

black-hole that drops all the packets that it receives

– Utilizing Root Cause Information (RCI)• Similar to EPIC and RCN

• flush out all local invalid alternative routes

• Alternative route chosen can be guaranteed to be valid

• How to avoid slow propagation of long-term failure of insign pref– Every node will hold propagation of BGP update, if not design carefully

– Only one node will apply TIDR timer to insign prefixes• Nodes neighboring to failure

• First node to have valid alternative route

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TIDR Algorithm

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Performance Studies

• Used simBGP simulator• With both clique and Waxman random network topologies• Simulated both link fail-down and fail-over events

– Only dummy node announce prefixes• 20% to be significant, 80% to be insignificant

– Link failure• 20% to be long-term, 80% to be transient

• Settings– Link delay: randomly from 0.01 to 0.1 seconds– Processing delay: randomly from 0.001 to 0.01 seconds– MRAI timer: 30 seconds– TIDR timer: 10 minutes

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Fail-down Events

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Fail-Over Events

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Summary and On-going Work

• TIDR: Traffic-aware Inter-Domain Routing– Capitalizing on two important properties

• Internet access non-uniformity

• Prevalence of transient failure

– Differentiated BGP update propagation for sign and insign prefixes

• Propagating updates of sign prefixes with higher priority

• Aggressively slow down propagation of updates of insign prefix

• Performed simulation studies– Outperforms BGP and other existing enhancements