［2019/11/21開催「IIJ Technical DAY 2019」の講演資料です］ The growth of global Internet traffic has driven a rapid expansion of the submarine cable network, both in terms of the sheer number of links and its total capacity. Despite the scale and critical role of the submarine network for both business and society at large, we lack an understanding of the relationship between network-layer measurements and its underlying physical infrastructure. This talk discusses the importance characterizing the global submarine network and the critical role it plays as a basic component of any inter-continental end-to-end connection. グローバルなインターネット・トラフィックの増大は、海底ケーブルの回線数とその総容量の両方の観点から海底ケーブルネットワークの急速な拡張をもたらしています。海底ケーブルネットワークの規模と役割が企業と社会の全体に対して重要な課題であるにもかかわらず、ネットワーク層での測定とその物理的インフラである海底ケーブルとの関係はあまり理解されていません。本セッションでは、グローバルな海底ケーブルネットワークの重要性を考察し、そのケーブルネットワークが大陸間end-to-end接続の基本的構成要素として機能している重要な役割について解説します。 ▼講演者 IIJイノベーションインスティテュート（IIJ-II） 主任研究員 Zachary Bischof （ビショフ ザカリー）

1. Untangling the world-wide mesh of
undersea cables
Zachary S. Bischof & Kenjiro Cho
IIJ Tech Day 2019

2. Collaborators
Romain Fontugne
Fabian Bustamante
Alex Liu
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3. Source: TeleGeography 3

4. A world-wide mesh of submarine cables
Over 1 million km of cable around the globe
Carrying 99% of all intercontinental traffic
Critical infrastructure for connectivity and economies
Recent rapid growth, driven by inter-data center traffic
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5. 5

6. A world-wide mesh of submarine cables
We lack a clear understanding of this
global infrastructure
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7. Why now?
Growing dependency on Internet services
More and more cables reaching end-of-life
Increasing rate of
natural disasters
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8. A large submarine network in length
Data source: TeleGeography
Missing deactivated cables
Total cable length (km)
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9. … and capacity
Data source: Greg’s Cable Map
Average bandwidth
per cable laid
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10. Larger network, higher risks
Threats
• Environmental hazards
• Human actions
Costs
• Total disconnect
• Degraded performance
Data source: RIPE Atlas
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Reconfiguration of SEA-ME-WE 4 in Oct 2017
RTT spiking to 3x
higher

11. A new research agenda
Characterizing basic connectivity
Network measurements to physical infrastructure
Connecting Internet services and users
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12. 12
Quantifying connectivity risks
Iceland
Challenge: Difficult to map region s to submarine cables
DANICE
Greenland
Connect

13. Quantifying connectivity risks
Nuuk
Qaqortoq
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Greenland
Greenland
Connect
Greenland
Connect
? ??

14. False sense of redundancy at network level
Traceroute has no visibility below Level 3
• “Unique” network paths may traverse the same submarine cable
Goal: Annotate traceroutes with
potential submarine links
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ALBA-1
1 200.14.48.132 1.049ms
2 192.168.118.89 5.829ms
...
6 63.245.90.168 35.76ms
...
16 129.105.247.95 73.717ms
17 165.124.182.216 73.553ms

15. Mapping down the stack
1) Geolocate router IPs
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2) Identify possible submarine cables
3) Check for terrestrial infrastructure between router locations and possible landings
4) Cross reference historical cable activity data with presence in traceroute data to
identify specific cable

16. Mapping down the stack
1) Geolocate router IPs
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Challenge: Recent works have shown problems with current databases
[Gharaibeh IMC ‘17, Weinberg IMC ’18, …]
Currently using RIPE’s latency-based IP geolocation service

17. Mapping down the stack
2) Identify possible submarine cables
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Latency-based: Using differential RTT [IMC ‘17] between routers to calculate maximum
distance traveled
Challenge: Variability in delay, not just propagation delay
Operator-based: Compare IPs’ AS data to known operators lists
Challenge: Cables often have tens of operators
TAT-14 owner list

18. Mapping down the stack
3) Check for terrestrial infrastructure between router locations and possible landings
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Using Open Street Map and Google Maps as a heuristic for terrestrial cables

19. Mapping down the stack
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4) Cross reference historical cable activity data with presence in traceroute data to
identify specific cable
ALBA‐1 cable to Cuba
activated in 2013 Existing satellite
connections via
ASN 22351 and 32034
New, faster routes via
ASN 6453 and 12956

20. Mapping down the stack
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SEA-ME-WE-3 outage in May 2018
Outage continued for about three
weeks, traffic shifted to run over
different networks
4) Cross reference historical cable activity data

21. Graph theory analysis
But some links are “more important” than others
• What are the traffic dominant links?
• Which links are more critical for connectivity?
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Graph of the submarine cable network
• Vertex for each cable
• Edge for terrestrial infrastructure
Centrality analysis identified SEA-ME-WE3 as the central-most
cable
• Seems to be notoriously unreliable
• At least 17 different failures on different segments

22. … and beyond
How cables relate to various services and their users
• World economy – Stock markets
• User-facing services – Multi-cloud, multi-CDN services
• National security – Sharks and Russian submarines
Ongoing work on an API service (Seawolf) for researchers, operators
• Identify possible submarine cables in user-submitted traceroutes
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23. Summary
Submarine network infrastructure
• A critical part of the Internet
• With multiple (growing) threats
Ongoing work
• Characterization of the state of submarine infrastructure
• Mapping network measurements to physical infrastructure
• Topological risk analysis
• Identifying regions particularly susceptible to failures
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