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Conclusions
Combining data from different measurement/monitoring systems, our analysis provides insight into how the cable outages affected Internet connectivity:
- Immediately following each cable cut, networks became unreachable, either because routes were withdrawn in BGP or because back haul links went down.
- Sites that had arranged for multiple transit providers observed massive rerouting in BGP, such as moving to satellite providers. Other sites were rerouted on the sub-IP level, moving to circuits set up over other, lower bandwidth or longer distance cable systems. Both types of back-ups experienced increased latencies and congestion, significantly impacting End Users and likely causing instability in BGP.
The Mediterranean cable crisis demonstrates the importance of adequately dimensioned redundant connectivity, ideally following different geographical paths. When the first cable went out at 04:30 (UTC), the other cable was still in service. It could have been used by those ISPs who lost connectivity due to the first outage.
Appendix: Selected BGP Case Studies
Case Study 1 - Unreachable Prefixes From BGP Point of View (Egyptian Prefix)
Case Study 2 - BGP Still Carries Routes While Traffic is Black Holed (Bahrain)
Case Study 3 - BGP Rerouting of Prefixes
Case Study 4 - OmanTel: Explosion in AS Path Count, Hours of BGP Churn
Further Reading
About Submarine Cable
The International Cable Protection Committee provides a lot of background information on submarine cable systems, particularly in the Information and Publications sections of their website. The About Cables [PPT] presentation on submarine cables and their role in today's world is a good starting point.
The June 2005 issue of info@CITEL, the electronic bulletin of the Inter-American Telecommunication Commission (CITEL), features an interesting article on fibre-optic submarine cable networks: http://www.citel.oas.org/newsletter/2005/junio/submarino_i.asp
Atlantic Cable is a website dedicated to the history of the Atlantic cable and undersea communications. It features background information on the first Atlantic cable projects as well as chronological records of all major submarine communications cables ever deployed.
http://www.atlantic-cable.com/
In the News
I Love Bonnie.net have produced a write-up of the chronology of events, including pointers to the news articles that first reported the outages: http://www.ilovebonnie.net/2008/02/12/the-submarine-cables-a-complete-guide-to-the-2008-internet-outage/
Technology Review, published by MIT, also featured a good story on the events:
http://www.technologyreview.com/Infotech/20152/?a=f
Other Data Analysis
Renesys presented analysis of their BGP data in a lightning talk at NANOG42: http://www.renesys.com/tech/presentations/pdf/nanog42-lightning.pdf
SLAC analysed the data from their PingER project, an active measurement service based on ICMP echo reply. Results were published on the web: https://confluence.slac.stanford.edu/display/IEPM/Effects+of+Fibre+Outage+through+Mediterranean
References
[1] Research by Telegeography. Capacity is shown in bottom right of the maps at http://telegeography.com/products/map_cable/images/Cable_Map_big.gif and http://image.guardian.co.uk/sys-images/Technology/Pix/pictures/2008/02/01/SeaCableHi.jpg
[2] The Economist: Of cables and conspiracies, http://www.economist.com/world/international/displaystory.cfm?story_id=10653963
[3] M.E.Kordahi, S.Shapiro: Worldwide Trends in Submarine Cable System Faults, http://www.scig.net/Section11a.pdf
[4] http://iscpc.org/cabledb/Mediterranean_and_Red_Sea_Cable_db.htm