Hokkaido-Sakhalin Cable System (HSCS): latency up to 2.5× normal, 30 Apr 2026
What we measured
| Cable | Hokkaido-Sakhalin Cable System (HSCS) |
| Segment | Ishikari, JP → Nevelsk, RU |
| Detected | 2026-04-30 20:30 UTC |
| Resolved | 2026-05-01 22:00 UTC |
| Duration | 1d 1h |
| Observed latency | 1.5 ms |
| Baseline | 88.2 ms · 2.54× |
| Increase | +100% |
| Severity | warning |
Who is affected
Countries where Hokkaido-Sakhalin Cable System (HSCS) 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 |
|---|---|---|---|
| Japan resilience index: 100 · resilient |
1 of 53 cables (2% of submarine diversity) | 5 Villages 6 Islands, APCN-2, Apricot +49 more | median 225 ms today vs 203 ms over 30 days (468 routes) - unchanged |
| Russia resilience index: 100 · resilient |
1 of 13 cables (8% of submarine diversity) | BCS North - Phase 2, Energy Bridge Cable, Far East Submarine Cable System +9 more | median 59 ms today vs 55 ms over 30 days (1801 routes) - unchanged |
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 2026043004: warning - ratio 2.54x
- Alert #102 resolved: RTT 1.48ms (baseline 88.18ms), 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.