Next steps in interdomain

routing research(why measurements are not enough

to decide about it)

Next steps in interdomain

routing research(why measurements are not enough

to decide about it)

Steve UhligSteve UhligUniversité catholique de Louvain, Université catholique de Louvain,

BelgiumBelgiumsuh@info.ucl.ac.besuh@info.ucl.ac.be

Steve UhligSteve UhligUniversité catholique de Louvain, Université catholique de Louvain,

BelgiumBelgiumsuh@info.ucl.ac.besuh@info.ucl.ac.be

Internet-wide BGP behaviorInternet-wide BGP behavior

- Claim:Claim: BGP convergence can be slow [Labovitz BGP convergence can be slow [Labovitz

et al. SIGCOMM’98&00]et al. SIGCOMM’98&00]

- Causes of routing dynamics:Causes of routing dynamics: network network

engineering, flapping links, traffic engineering, flapping links, traffic

engineering, misconfigurations,...engineering, misconfigurations,...

- Causes of “slow” BGP convergence:Causes of “slow” BGP convergence: Internet Internet

size, CPU load, BGP timers, route flap damping size, CPU load, BGP timers, route flap damping

[Agarwal et al. PAM’04, Feldman et al. PAM’04][Agarwal et al. PAM’04, Feldman et al. PAM’04]

We don’t really know how well BGP performs We don’t really know how well BGP performs

AS-wide BGP behaviorAS-wide BGP behavior

- Impact of eBGP on traffic in tier-1 [Agrawal Impact of eBGP on traffic in tier-1 [Agrawal

et al. SIGMETRICS’05]: not much dynamics et al. SIGMETRICS’05]: not much dynamics

inside AS due to external dynamicsinside AS due to external dynamics

- Dynamics of hot-potato routing [Teixeira et Dynamics of hot-potato routing [Teixeira et

al. SIGMETRICS’04] and impact on traffic al. SIGMETRICS’04] and impact on traffic

[Teixeira et al. PAM’04]: high sensitivity of [Teixeira et al. PAM’04]: high sensitivity of

inside AS due to routinginside AS due to routing

AS routing behavior depends on chosen AS AS routing behavior depends on chosen AS

andand

measured period [Teixeira et al. CCR 2005]measured period [Teixeira et al. CCR 2005]

Inherent limitations of measurements

Inherent limitations of measurements

- Even multiple vantage points give poor Even multiple vantage points give poor

view of what’s going on [Feldmann et al. view of what’s going on [Feldmann et al.

SIGCOMM’04]SIGCOMM’04]

- Locating instabilities is hard, finding Locating instabilities is hard, finding

out what happened even harderout what happened even harder

- Studying individual ASes does not help Studying individual ASes does not help

much quantifying AS-wide routing dynamicsmuch quantifying AS-wide routing dynamics

- Studying interactions between ASes is one Studying interactions between ASes is one

next step towards understanding Internet-next step towards understanding Internet-

wide BGP behavior (mentioned by wide BGP behavior (mentioned by

Christophe already)Christophe already)

Inherent limitations of measurements

Inherent limitations of measurements

- Can measurements alone help us decide whether Can measurements alone help us decide whether

interdomain routing should be changed?interdomain routing should be changed?

I don’t think so ! But...I don’t think so ! But...

- Trying to make sense of all available BGP Trying to make sense of all available BGP

data might give some better idea if what is data might give some better idea if what is

right or wrong with BGPright or wrong with BGP

- Thinking about new routing protocols (HLP, Thinking about new routing protocols (HLP,

metarouting) also helps understand what are metarouting) also helps understand what are

the alternatives to BGPthe alternatives to BGP

Building models to go beyond measurements limitations

Building models to go beyond measurements limitations

- Building models of Internet route propagation Building models of Internet route propagation

can help understand what matters to explain can help understand what matters to explain

what we see (next step)what we see (next step)

- But simply reproducing AS paths is hard But simply reproducing AS paths is hard

[Mühlbauer et al. SIGCOMM’06][Mühlbauer et al. SIGCOMM’06]

- How do you deal with: How do you deal with:

- What is a What is a policypolicy??

- What is a What is a routing domainrouting domain??

Building models to go beyond measurements limitations

Building models to go beyond measurements limitations

- Building models of Internet requires reverse-Building models of Internet requires reverse-

engineering the Internet!engineering the Internet!

- What is the right granularity for:What is the right granularity for:

- Topology:Topology: ASes, routing domains, and routers ASes, routing domains, and routers

- Policies:Policies: multiple peerings, filtering multiple peerings, filtering

performed on peeringsperformed on peerings

- Granularity of Internet model will depend on Granularity of Internet model will depend on

what you want to do with it.what you want to do with it.