Sirius South cable: latency up to 2.3× normal, 11 May 2026
What we measured
| Cable | Sirius South |
| Segment | Blackpool, GB → Dublin, IE |
| Detected | 2026-05-11 17:01 UTC |
| Resolved | 2026-05-11 18:31 UTC |
| Duration | 1h 30m |
| Observed latency | 21.4 ms |
| Baseline | 38.2 ms · 2.3× |
| Increase | +138% |
| Severity | warning |
Who is affected
Countries where Sirius South comes ashore, how much of their submarine diversity this cable represents, and what our measurements into them show.
| Country | Dependence on this cable | Other submarine cables | What the measurements show |
|---|---|---|---|
| Ireland resilience index: 100 · resilient |
1 of 16 cables (6% of submarine diversity) | AEC-1, Beaufort, CeltixConnect-1 (CC-1) +12 more | median 73 ms today vs 62 ms over 30 days (180 routes) - slower |
| United Kingdom resilience index: 100 · resilient |
1 of 68 cables (1% of submarine diversity) | 2Africa, Amitie, Apollo +64 more | median 103 ms today vs 74 ms over 30 days (1011 routes) - slower |
Dependence is structural (share of the country's submarine cables), not a traffic share: real traffic distribution across cables is not public.
Path analysis
Traffic kept the same route. Latency rose without a visible path change, which points at congestion or a fault on the existing route rather than a reroute.
Cross-probe verdict. Other measurements did not confirm the event. We treat this as a probable false positive and label it as such.
Timeline
- Alert 2026051101: warning - ratio 2.3x
- Alert #115 improving: 1/3 consecutive OK
- Alert #115 resolved: RTT 21.44ms (baseline 38.17ms), 3 consecutive OK
Detection method
Latency is sampled continuously from our probe network. An alert opens when round-trip time to a monitored endpoint holds above its rolling baseline, and closes automatically once it returns. Full method is described on the methodology page.