The Past and Present of IXPs
Malte Tashiro

What is an IXP?
■■■

Common ground to connect networks/ autonomous systems (ASes)(not actually JPNAP Tokyo)
IIJ
AS2497

Alternative to direct 1:1 connection
between networks (private peering)
Possible advantages–Reduced cost and latency–

Improved bandwidthLINE
AS38631

JPNAP
Tokyo

Cloudflare
AS13335

NTT
AS4713

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Historical Purpose“Keep local traffic local”0■■

Regions with poorconnections might have totake long routing detours
Establish regional
connectivity instead
N. Chatzis, G. Smaragdakis, A. Feldmann, and W. Willinger, “There is More to IXPs than Meets
the Eye,” ACM SIGCOMM Computer Communication Review, vol. 43, no. 5, pp. 19–28, 2013.
0

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Why do research on IXPs?
■

Part of a larger project on Internet topology■

The Internet is critical infrastructure→ We ought to understand role of all components
More knowledge improves the quality of decisions(e.g., where to establish new connections)■

Are IXPs still (only) fulfilling their historical purpose?
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PeeringDB■

Database containing peering and IXP information■

One of the go-to sources for IXP information–■

Others: PCH, Euro-IX IXPDB, HE Internet Exchange Report, ...

Why we use it: Historical data available from 6/2010

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A look at the last 13 years
Number of IXPs and members

Member count for selected IXPs

Size of IPv4 peering LANs

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Detecting dependencies with traceroute
1. ASx is not dependent

ASProbeTracerouteAS

TargetASx
AS

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Detecting dependencies with traceroute
1. ASx is not dependent
2. ASy depends on ASx

ASProbeTracerouteAS

Target

ASx

ASy

AS

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ASAS

IXP
ASx

ASy

AS

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Detecting dependencies with traceroute
1. ASx partly depends on the IXP

AS

AS

IXP
ASx

ASy

AS

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Detecting dependencies with traceroute
1. ASx partly depends on the IXP
2. ASy depends on ASx
3. ASy partly depends on the IXP

AS

AS

IXP
ASx

ASy

AS

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Detecting dependencies with traceroute
ASAS

1. ASx partly depends on the IXP
2. ASy depends on ASx
3. ASy partly depends on the IXP

IXPTechnical Detail
Dependency is expressed as aASx
value between 0 and 1.
For example (simplified):
ASx → IXP ~0.6
ASASy → ASx 1.0
ASy → IXP ~0.6
But we will stick to a binary classification (depends, or not) for now.

ASy

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IXP dependencies over the years
IXP member counts

Preliminary!

One datapoint (in January) for each year
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IXP (and AS) dependencies in the present■■■

ASes incur way more
dependencies in general
Some large Tier-1 ISPs
stand out
Same is true for IXPs,
but on a smaller scale

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Geographic footprint of IXPs■■

Countries of IXP members arealready visible in PeeringDB– Dependents are deeper in thetopology and not obvious■Members

We can identify the countries ofdependent ASes

Dependency analysis gives us a
new perspective on thegeographic footprint of IXPs

ASAS

IXP
Country C

Country A
Country B

ASAS

AS(Possible) Dependents

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A close look at DE-CIX Frankfurt■■■■

German IXPMost dependents not inGermany
Many Russian and Indian
ASes are reached via DE-CIX(from our vantage points)** are ASes with presence inmultiple countries

Who connects these dependencies?

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A close look at DE-CIX Frankfurt/

AS31133

AS20485= Members that connect dependents= Dependents that are shared between members

ASx
ASAS

DE-CIX●

AS9498AS●

Example25 members share
181 dependents
19 members combined
have 150 dependentsAS

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Regional and global IXPs
IX.br São Paulo

DE-CIX Frankfurt

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Conclusion■

IXPs keep growing and changing– Most are small and regional– Some big players are emerging■

Large IXPs do not necessarily incur dependencies■

Some IXPs have grown into international transit hubs
– Interesting to monitor their role in the future

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Image sources■Slide 3: © User:San Jose / Wikimedia Commons / CC-BY-SA-3.0 / GFDL

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