Cases3 cases

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1. IL-0348 Scaleway's FR-PAR region lost public internet connectivity when one 100 Gbps backbone link was saturated

   Scaleway2025

   Symptoms

   On 10 March 2025 at 16:22 UTC, public internet connectivity in Scaleway's FR-PAR region broke for all products. Most internet traffic between the FR-PAR-2 availability zone and the rest of the PAR region was blackholed for about five minutes, while VPC traffic and Dedibox RPN kept working.

   Packet lossService outageHigh latency

   Trigger

   While Scaleway's network team connected a new data center to the FR-PAR backbone, a human mistake in a router configuration rerouted more than 1 Tbps of traffic between OpCore DC3 and DC5 through a single 100 Gbps link.

   Root cause

   Operator error

   Component

   Backbone network (WAN)Object storageAuthoritative DNS servers and records

   Contributing factor

   Automation amplification

   Detection

   The router configuration error was detected quickly and rolled back within four minutes.

   Remediation

   • Rolled back the router configuration, restoring the correct configuration at 16:27 UTC

   Action items

   • Harden the peer review and production communication process for changes
   • Add failsafes and tests before network configuration is applied at backbone level
   • Deploy the fix for the Object Storage synchronisation software issue

   View case
2. IL-0531 Azure Database for MySQL Single Server and MariaDB in West US rejected every new connection for a batch of servers

   Microsoft Azure2024

   Symptoms

   From 04:26 UTC on 19 April 2024, every new connection to a subset of Azure Database for MySQL - Single Server and Azure Database for MariaDB servers in West US failed, and retries did not help. The first report came at 04:46 UTC from Azure Databricks, which told the MySQL team that multiple databases were unreachable.

   Service outageIntermittent timeouts

   Trigger

   At 04:26 UTC, during planned maintenance in West US, the DNS update that moves new incoming connections for a batch of MySQL and MariaDB servers to a new gateway ring was made, and a procedural error pointed it at a newly built gateway ring whose configuration was incomplete.

   Root cause

   Operator error

   Component

   DatabaseAuthoritative DNS servers and records

   Contributing factor

   Monitoring blind spot

   Detection

   Service telemetry did not detect the failure because the new gateway ring had no telemetry or monitoring configured yet. At 04:46 UTC Azure Databricks reported to the MySQL team that multiple databases were unreachable.

   Remediation

   • Rolled back the DNS change and moved all connections back to the previous working gateway ring after validation

   Action items

   • Add checks, testing and sign-off procedures before switching production gateway rings
   • Add Azure Databricks alerts that detect multiple databases becoming unavailable within a short time

   View case
3. IL-0221 A backbone maintenance command disconnected all Facebook data centers, and its DNS servers withdrew their BGP routes

   Meta2021

   Symptoms

   On 4 October 2021 Facebook's platforms went down worldwide: every connection in Facebook's global backbone network was lost, and the data centers were cut off from each other and from the internet. The rest of the internet could no longer find Facebook's servers, because Facebook's authoritative DNS servers had become unreachable.

   Service outageDNS resolution failuresNetwork unreachable

   Trigger

   During routine maintenance of the backbone, a command was issued to assess the availability of global backbone capacity, and it unintentionally took down all connections in the backbone network.

   Root cause

   Operator error

   Component

   Backbone network (WAN)BGP routingAuthoritative DNS servers and records

   Contributing factor

   Automation amplificationCircular dependencyLimited debug access

   Remediation

   • Sent engineers onsite to the data centers to debug the issue and restart systems
   • Brought the backbone network back online across the data center regions
   • Brought services back gradually, managing the rising load to avoid crashes from a traffic surge

   Action items

   • Find ways to simulate the global backbone being taken offline in storm drills
   • Strengthen testing, drills and overall resilience

   Lessons

   The hardening that protects Facebook's data centers against unauthorized access slowed recovery from an outage caused by Facebook's own error, and the author judges that tradeoff worth keeping. Storm drills prepared the teams to bring load back safely, although no drill had yet simulated the global backbone going offline.

   View case

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