FLAG North Asia Loop/REACH North Asia Loop

FLAG North Asia Loop (FLAG-NAL), also known as REACH North Asia Loop, is a 9,504 km submarine cable that has been connecting the major East Asian telecom hubs since 2001. Its four landings form a loop around the North Asian maritime region: Tong Fuk in Hong Kong, Toucheng in Taiwan, Busan in South Korea, and Wada in Japan. The cable was one of the earliest dedicated regional cables built for the booming East Asian internet, originally operated by FLAG Telecom (Fiber-Optic Link Around the Globe) and later by Reliance Globalcom and REACH under various ownership arrangements over the cable's lifetime.

FLAG-NAL is 25 years old. In submarine cable terms, it is near the end of its original 25-year design life. That makes it an interesting case study: how does a cable that predates most of the cloud economy still perform today? The answer from our measurements is: it delivers physics-floor latency along its longest monitored segment, with a standard deviation tight enough to reveal no evidence of repeater degradation or fibre ageing.

46 ms Hong Kong to Japan

Our monitor measures FLAG-NAL between Tong Fuk on Hong Kong's Lantau Island and Wada on Japan's Pacific coast — the longest segment of the loop. Over 30 days we collected 33 samples in the Tong Fuk → Wada direction:

The standard deviation of 2.00 ms is extraordinary. Across 33 samples over 30 days, every measurement sits within about 6 ms of every other. This is the signature of a cable operating exactly as designed, with no intermittent faults, no congestion surges, and no routing changes disrupting its baseline behaviour. Alongside our measurements on PC-1 (2000-era trans-Pacific, sd 2.88 ms), FLAG-NAL's tightness is among the most stable we have documented on any cable, young or old.

Six IP hops is also remarkable. A trans-continental path with only six routers between the endpoints is as clean as commercial internet infrastructure gets — it implies Hong Kong-based traffic sources routing directly into an edge interconnect that feeds FLAG-NAL, arriving at a Japan-side edge with essentially no intermediate transit.

The great-circle distance from Tong Fuk to Wada is approximately 2,800 km. Light in fibre has a theoretical round-trip minimum of 27.4 ms for that distance. We measure 44.7 ms — 1.63× the great-circle floor, or equivalently about 4,570 km of fibre path length. The extra distance relative to great-circle reflects the cable's actual route via the continental shelf around Taiwan rather than taking the direct deep-water geodesic.

A quarter-century of operation

FLAG-NAL was commissioned in 2001, during the aftermath of the dot-com bust that reshaped submarine cable economics. The early 2000s saw the collapse of several cable projects built during the late-1990s internet boom, and FLAG Telecom itself filed for bankruptcy in 2002 (reorganising and continuing operations). The cables themselves kept working; their ownership restructured multiple times.

FLAG-NAL has changed ownership several times over its operational life. The original FLAG Telecom became part of Reliance Communications (Indian telecoms group). Reliance Globalcom rebranded to Global Cloud Xchange. REACH (the joint venture between Telstra and PCCW) merged its North Asia Loop assets with the FLAG system at various points. In 2026, the cable is operated by a combination of entities with complex historical claims — but operationally, the cable itself is the same physical infrastructure installed on the seafloor in 1999–2001.

Why does this matter for our measurements? Submarine cables are remarkably independent of their corporate ownership. The fibre does not care who holds the equity. As long as someone maintains the landing stations, pays the power bills, and keeps electronics refreshed at each endpoint, the cable continues to deliver the physics-floor performance it was designed for. Our 2026 measurements on FLAG-NAL confirm that across all the ownership changes, the physical cable is still functioning at specification.

Four landings in a regional loop

The loop architecture is what makes FLAG-NAL distinctive. Instead of a straight trunk between two endpoints, the cable forms a ring connecting four East Asian landings. Traffic can enter the loop at any landing and exit at any other, with the network selecting the shorter direction around the ring based on whichever path has better peering and lower congestion.

For example: Hong Kong-to-Busan traffic can travel via Toucheng (Taiwan) or via Wada (Japan) depending on the carrier's preference. Both directions are physical options on the same cable body. This redundancy is valuable because any single cable fault within the loop leaves the remaining landings interconnected via the alternate ring direction.

Loop topologies were fashionable in late-1990s cable designs. Several similar loops were built in the Mediterranean (SEA-ME-WE 3's Mediterranean ring), the Caribbean (ARCOS), and around Japan (JIH). Modern cables typically prefer straight-trunk-with-branches architectures because branching units have matured technologically, making multi-landing trunks more efficient than loops. FLAG-NAL's loop structure is a fingerprint of its era.

Capacity evolution over 25 years

FLAG-NAL's original design capacity was modest by 2025 standards. It was built with two fibre pairs operating at 10 Gbps per wavelength with 32-channel DWDM — a total design capacity of 640 Gbps. That was substantial in 2001. In 2026, coherent-modulation upgrades have raised usable capacity to some multiple of the original, though exact current figures are not publicly disclosed.

Like other 25-year-old cables we have documented (PC-1, SEA-ME-WE 3, Japan-US Cable Network), FLAG-NAL's relevance today is not capacity — modern cables carry thirty times as much on a single fibre pair — but existence. An operational 25-year-old cable with clean measurements is infrastructure that continues serving traffic at marginal operational cost. Its capital investment was amortised years ago; its electronics have been refreshed multiple times; its physical body shows no sign of planned retirement.

What our data proves

• FLAG-NAL delivers Hong Kong → Japan at 44.7 ms with 2.00 ms standard deviation. Among the most stable trans-regional measurements in our dataset, on a 25-year-old cable.
• Six IP hops on a trans-continental path is exceptionally clean. The cable's loop architecture provides direct interconnect between endpoints without multi-hop transit.
• Submarine infrastructure outlasts its commercial nominal life. FLAG-NAL's 2001 commissioning puts it at the end of its rated 25-year design life. The cable continues functioning within specification.

FLAG-NAL is one of the oldest commercially operating cables in our measurement set. Alongside PC-1, it provides evidence that submarine cables, when properly built and maintained, are among the most durable pieces of telecommunications infrastructure. The glass itself does not age; the electronics at each end are refreshed every 5–7 years; the commercial ownership changes repeatedly; and the cable keeps delivering its physics-floor performance.

Try it yourself

Live data on the FLAG-NAL cable page. For contrast with modern Asian cables, see APRICOT (2025 hyperscaler), SJC2 (2025 consortium), and PC-1 (2000 trans-Pacific).