Jakarta-Bangka-Batam-Singapore (B2JS)

The Jakarta-Bangka-Batam-Singapore cable system — B2JS, for short — is a 759-kilometre domestic Indonesian submarine cable that doubles as one of the busiest international internet paths in Southeast Asia. It entered service in 2013, is owned by a single Indonesian private operator, Triasmitra (PT Mora Telematika Indonesia), and is the backbone connecting Java's internet hub at Jakarta to Singapore — the regional peering capital. Our 103 measurements over 30 days on B2JS reveal a cable that carries staggering traffic volumes for its size, with bursty congestion patterns that illustrate the limits of being the small operator on a large route.

The shortest submarine cable that matters

B2JS is short by submarine-cable standards. At 759 kilometres it is shorter than many domestic terrestrial cables. But its route is valuable disproportionately to its length: it crosses the Singapore Strait and connects Jakarta — one of Southeast Asia's two largest cities — to Singapore, which hosts the region's internet exchange points, hyperscaler data centres, and international connectivity. Practically every Indonesian ISP, content platform, and enterprise customer that wants to reach Singapore-based services, or vice versa, uses a cable crossing this corridor. B2JS is not the only one — Apricot and older consortium cables cross similar routes — but it is the one owned by an Indonesian private operator rather than a foreign hyperscaler or consortium.

The ownership is significant. Triasmitra is the trade name of PT Mora Telematika Indonesia, a mid-size Indonesian telecommunications company that owns backbone fibre across Indonesia. Building and owning B2JS gives Triasmitra direct access to Singapore without paying transit to Indonesian state-owned incumbent Telkom Indonesia, and without depending on the foreign-consortium cables that Telkom controls access to. For a mid-size Indonesian operator, B2JS is the single most important piece of infrastructure: it is the cable that lets them compete on international service without a Telkom middleman.

Our measurements

We monitor B2JS primarily between Tanah Merah (Singapore) and Jakarta (Indonesia) — the cable's southern trunk segment. Over 30 days we have 93 clean samples in this direction:

The Tanah Merah → Jakarta measurement shows a picture of a cable operating near its capacity limits. The physical minimum of 16.9 milliseconds is what the fibre can deliver: a direct packet crossing Singapore Strait to Jakarta, round-trip, through 759 kilometres of glass. But the average is 84 ms — five times the minimum — and the maximum is 246 ms, almost fifteen times the minimum. This kind of variance is not typical of an under-utilised cable; it is the signature of a cable that is regularly running close to its capacity ceiling, where queueing delays at the cable's ingress and egress routers stretch out the round-trip time for many packets well beyond the physics floor.

The high variance is structural. At 759 kilometres with (we estimate) 4 to 6 fibre pairs of early-2010s design, B2JS has a design capacity of perhaps 10 to 20 Tbps. Singapore-Jakarta traffic demand has grown many times faster than that ceiling has been upgraded. When demand approaches capacity, buffers at each end fill and individual packets experience seconds of variation in transit time. The average of 84 ms against a minimum of 17 ms is what that looks like in measured data.

Multi-directional use

B2JS is also measured from our distributed probes for reachability into Jakarta:

These latencies reach Jakarta through a chain of international cables: our probes transit to Europe, cross the Mediterranean to the Middle East, and then via Red Sea and Indian Ocean cables reach Jakarta. B2JS contributes its final 17-ms segment to this chain when the packet crosses from Singapore peering into Indonesian networks. In each of these paths, B2JS is the last cable before the destination; the 17 ms it adds is small compared to the 180-250 ms of prior international transit.

The Triasmitra paradox

B2JS exists because Triasmitra built it — at a scale where no hyperscaler consortium would have bothered, because 759 km is not a route that fits into the global trunk-cable economics. At the same time, Triasmitra is a relatively small company by telecommunications standards, without the capital to continuously upgrade B2JS to the capacity demand it now handles. The result: B2JS is enormously valuable Indonesian infrastructure (every Jakarta–Singapore data flow has some chance of transiting it) while simultaneously running at the sort of utilisation levels that produce the measurement variance our data shows.

The fix is not technically complicated: Triasmitra could commission additional fibre pairs, upgrade transponders to modern coherent transceivers, or lay a parallel cable body. But each of these requires capital that a mid-size operator spends carefully. Meanwhile, hyperscaler cables like Apricot and planned next-generation routes offer alternatives for customers willing to pay their prices. B2JS's role is therefore likely to stabilise at "affordable Indonesian path to Singapore for Indonesian ISPs," rather than transform into something larger.

Why B2JS matters

Submarine cable statistics often focus on the biggest and longest systems. B2JS is the opposite: one of the shortest cables in our monitoring, and owned by a company that most internet users outside Indonesia have never heard of. Yet it carries traffic that matters in proportion to its scale. Jakarta has more internet users than most European countries. Singapore is the interconnection point for half of Southeast Asia. The cable between them — if you own it and you are not Google — is a meaningful piece of infrastructure, even at 759 kilometres.

Try it yourself

Live latency data on the B2JS cable page. For regional context see Apricot (a 2025 hyperscaler cable connecting the same region with very different economics) and APG (the 2016 regional consortium backbone). Our measurements refresh every two hours.

Small does not mean unimportant.