Broken submarine cables slow internet across Philippines

Two submarine cable segments connecting the Philippines to Singapore and Hong Kong failed on Friday, cutting 300 Gbps of capacity and forcing traffic onto longer, congested routes. Carriers say redundancy kept the internet running, albeit slower.

Internet users across the Philippines experienced widespread slowdowns Friday after two submarine cable segments connecting the country to Singapore and Hong Kong went down simultaneously.

The Department of Information and Communications Technology said it is investigating the cause. Officials listed sabotage as a possibility but said it is too early to draw conclusions.

"The internet does not trust any single road," said a network engineer familiar with the rerouting. "When paths die, traffic moves to the rest."

Submarine cables carry over 99 percent of intercontinental data traffic, according to TeleGeography. Roughly 700 cable systems span the ocean floor, with 1,900 landing points. Each cable is roughly the thickness of a garden hose, containing glass strands thinner than a human hair. Repeaters spaced along the line boost light signals across thousands of kilometers.

Cables break 150 to 200 times a year worldwide. Anchors, fishing gear, earthquakes, and equipment failure are the usual causes.

Singapore and Hong Kong serve as two of Asia's primary internet exchange hubs. Networks from across the region peer there because handing traffic to a neighbor is cheaper and faster than sending it the long way around. Losing both paths at once was like losing two major highway interchanges on the same day.

Philippine ISPs lease capacity on multiple cable systems heading toward Hong Kong, Japan, Guam, and the U.S. West Coast. When the Singapore and Hong Kong segments failed, the Border Gateway Protocol withdrew the dead route announcements and updated detour signs across the global routing table within minutes.

Traffic shifted to longer paths — Manila to Tokyo to the U.S. West Coast and back — adding latency. The same volume of data now squeezes through fewer lanes. Globe Telecom confirmed it was rerouting data traffic.

Operators locate breaks using optical time-domain reflectometry: a pulse of light travels down the fiber, and the echo from the break returns to pinpoint the fault within meters. A cable ship then sails to the coordinates, hauls the cable up with a grappling hook or underwater robot, splices in new fiber, and lowers it back to the seabed. two dozen repair ships stand by worldwide. Repairs take days to weeks depending on weather and ship position.

PLDT's disclosure illustrates how redundancy works. ISPs buy capacity — slices of a cable's throughput — like airlines buying seats on routes they don't own. Three hundred gigabits per second supports tens of thousands of simultaneous video streams. The carrier had paid for spare capacity on alternate routes for years, precisely for this scenario.

"Redundancy is insurance you buy daily and are grateful for on the worst day," the engineer said.

The internet feels like weather — something in the air. It is glass tubes on the ocean floor, a small fleet of repair ships, and routers swapping detour signs thousands of times a second.

Run traceroute or mtr against a site you use daily and read the city names in the hops. The journey is more literal than most people realize.