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SIGCOMM CCR Paper: When the Lights Go Out: Internet Resilience During the 2025 Iberian Power Outage
Studying how the Internet behaves when large‑scale disruptions occur is a current focus of our research group. Together with researchers at DE‑CIX, we studied the effects of the nationwide power outage on April 28, 2025 at the Iberian Peninsula by combining traffic‑level measurements, active probing, routing data and even amateur‑radio reports. The results of our work appear in the April 2026 issue of ACM SIGCOMM CCR. Understanding what stays online—and what goes dark—helps operators, policymakers and the public prepare for future crises, whether they stem from natural disasters, grid failures, or other large‑scale events.
In this paper we traffic levels from the four major Iberian Internet exchange points (e.g., from our TraffIX IXP traffic monitoring plattform), ran continuous IP‑liveness scans, examined BGP updates from RIPE RIS, and cross‑checked the results with the PSKReporter amateur‑radio platform. When the grid collapsed on 28 April 2025, traffic at all four IXPs fell within minutes to night‑time levels, yet a non‑zero baseline persisted, showing that core routing equipment kept running on backup power. By breaking down the remaining traffic we could see which services (e.g., CDN and international transit) were most robust and which (e.g., enterprise and gaming) disappeared almost entirely.
Thus, eyeball traffic is highly sensitive to power loss, with traffic at major IXPs in the Iberian Peninsula dropping by 33–70% almost immediately, reflecting widespread loss of end-user connectivity and IP liveness. At the same time, the persistence of core infrastructure traffic—especially traversing traffic not originating from or destined to the affected region—highlights the resilience of data center–hosted services.
However, our observations also reveal that this resilience has limits: a partial failure in a major data center during the power outage led to a second noticeable disruption in both IXP traffic and BGP stability. These findings emphasize that, while data centers offer protection against localized outages, their own vulnerabilities can amplify the impact of already critical incidents. By combining passive measurement, active probing, and complementary amateur radio reports, we show that Internet resilience during large-scale power outages is shaped by both infrastructure location and backup readiness. Understanding this interplay is crucial for improving preparedness and designing more robust systems for future disruptions of similar scale.
Paper
When the Lights Go Out: Internet Resilience During the 2025 Iberian Power Outage
ACM SIGCOMM Computer Communication Review, Volume 56, Issue 1, April 2026
Aktuelles
SIGCOMM CCR Paper: When the Lights Go Out: Internet Resilience During the 2025 Iberian Power Outage
Studying how the Internet behaves when large‑scale disruptions occur is a current focus of our research group. Together with researchers at DE‑CIX, we studied the effects of the nationwide power outage on April 28, 2025 at the Iberian Peninsula by combining traffic‑level measurements, active probing, routing data and even amateur‑radio reports. The results of our work appear in the April 2026 issue of ACM SIGCOMM CCR. Understanding what stays online—and what goes dark—helps operators, policymakers and the public prepare for future crises, whether they stem from natural disasters, grid failures, or other large‑scale events.
In this paper we traffic levels from the four major Iberian Internet exchange points (e.g., from our TraffIX IXP traffic monitoring plattform), ran continuous IP‑liveness scans, examined BGP updates from RIPE RIS, and cross‑checked the results with the PSKReporter amateur‑radio platform. When the grid collapsed on 28 April 2025, traffic at all four IXPs fell within minutes to night‑time levels, yet a non‑zero baseline persisted, showing that core routing equipment kept running on backup power. By breaking down the remaining traffic we could see which services (e.g., CDN and international transit) were most robust and which (e.g., enterprise and gaming) disappeared almost entirely.
Thus, eyeball traffic is highly sensitive to power loss, with traffic at major IXPs in the Iberian Peninsula dropping by 33–70% almost immediately, reflecting widespread loss of end-user connectivity and IP liveness. At the same time, the persistence of core infrastructure traffic—especially traversing traffic not originating from or destined to the affected region—highlights the resilience of data center–hosted services.
However, our observations also reveal that this resilience has limits: a partial failure in a major data center during the power outage led to a second noticeable disruption in both IXP traffic and BGP stability. These findings emphasize that, while data centers offer protection against localized outages, their own vulnerabilities can amplify the impact of already critical incidents. By combining passive measurement, active probing, and complementary amateur radio reports, we show that Internet resilience during large-scale power outages is shaped by both infrastructure location and backup readiness. Understanding this interplay is crucial for improving preparedness and designing more robust systems for future disruptions of similar scale.
Paper
When the Lights Go Out: Internet Resilience During the 2025 Iberian Power Outage
ACM SIGCOMM Computer Communication Review, Volume 56, Issue 1, April 2026
Termine
SIGCOMM CCR Paper: When the Lights Go Out: Internet Resilience During the 2025 Iberian Power Outage
Studying how the Internet behaves when large‑scale disruptions occur is a current focus of our research group. Together with researchers at DE‑CIX, we studied the effects of the nationwide power outage on April 28, 2025 at the Iberian Peninsula by combining traffic‑level measurements, active probing, routing data and even amateur‑radio reports. The results of our work appear in the April 2026 issue of ACM SIGCOMM CCR. Understanding what stays online—and what goes dark—helps operators, policymakers and the public prepare for future crises, whether they stem from natural disasters, grid failures, or other large‑scale events.
In this paper we traffic levels from the four major Iberian Internet exchange points (e.g., from our TraffIX IXP traffic monitoring plattform), ran continuous IP‑liveness scans, examined BGP updates from RIPE RIS, and cross‑checked the results with the PSKReporter amateur‑radio platform. When the grid collapsed on 28 April 2025, traffic at all four IXPs fell within minutes to night‑time levels, yet a non‑zero baseline persisted, showing that core routing equipment kept running on backup power. By breaking down the remaining traffic we could see which services (e.g., CDN and international transit) were most robust and which (e.g., enterprise and gaming) disappeared almost entirely.
Thus, eyeball traffic is highly sensitive to power loss, with traffic at major IXPs in the Iberian Peninsula dropping by 33–70% almost immediately, reflecting widespread loss of end-user connectivity and IP liveness. At the same time, the persistence of core infrastructure traffic—especially traversing traffic not originating from or destined to the affected region—highlights the resilience of data center–hosted services.
However, our observations also reveal that this resilience has limits: a partial failure in a major data center during the power outage led to a second noticeable disruption in both IXP traffic and BGP stability. These findings emphasize that, while data centers offer protection against localized outages, their own vulnerabilities can amplify the impact of already critical incidents. By combining passive measurement, active probing, and complementary amateur radio reports, we show that Internet resilience during large-scale power outages is shaped by both infrastructure location and backup readiness. Understanding this interplay is crucial for improving preparedness and designing more robust systems for future disruptions of similar scale.
Paper
When the Lights Go Out: Internet Resilience During the 2025 Iberian Power Outage
ACM SIGCOMM Computer Communication Review, Volume 56, Issue 1, April 2026