Bangladesh could learn a lesson from Pakistan about building a diverse and more survivable connection to the Internet. The two countries had very different experiences as a result of a recent submarine cable cut. Where Pakistan's PTCL and Transworld have spent years building diversity into their International connectivity strategy, in Bangladesh the story is very different.|
At 08:41:51 UTC on Wednesday, 6 June 2012, the Sea-Me-We-4 submarine cable suffered a break 60 kilometers from the coast of Singapore, its eastern terminus. While the cause of the failure has not been publicly released, the resulting impact on South Asian Internet transit has been fascinating to follow.
Each time a major submarine cable breaks, it becomes very apparent which Internet providers were critically dependent on that physical piece of Internet infrastructure. Despite the efforts of the Bangladesh Submarine Cable Company to acquire a second submarine cable to serve its market, the Internet in Bangladesh is currently entirely dependent on SMW4 for fast access to the global Internet, the only other alternative being slow satellite links.
While Bangladesh's dependence on SMW4 is common knowledge in South Asian telecom circles, this incident revealed regional Internet provider Singapore Telecom (SIngTel) was also dependent on this piece of cable to serve its customers in South Asia and the Middle East.
As for Bangladesh, in the graphic to the right, we see SingTel (AS7473) and Indian provider Bharti Airtel (AS9498) disappear as providers for the local incumbent, namely, Bangladesh Telecommunications Company Limited (BTCL, AS17494). After the segment of SMW4 heading east to Singapore is cut, BGP routes shift to Telecom Italia, which provides on the SMW4 segment heading west.
The graphics shown below, derived from traceroute data, illustrate the impact on latencies to Bangladesh via BTCL from the west (New York) and east (Hong Kong). For the most part, these measurements show Internet traffic moving from SingTel to Telecom Italia on its way to BTCL. Each dot represents a cluster of measurements that share the same overall latency at approximately the same time. The colors represent the provider hand-off that was traversed. For example, "6762 17494" represents measurements that crossed Telecom Italia (AS6762) to get to BTCL (AS17494). Notice how service degrades (i.e., latencies both increase and become quite erratic) as this alternative is put into play, presumably due to increased congestion on the surviving path..
Despite the headlines, the major story isn't that Bangladesh has been disconnected from the Internet — they are still connected, just via overloaded cables. Rather, the real story is that SingTel has largely become unreachable from many providers in South Asia and the Middle East.
As we see below, networks routed via SingTel from its biggest customers in the region almost completely disappeared. (One notable exception is that Pakistani incumbent, PTCL maintains a greatly reduced set of routes to SingTel).
Market Intelligence users monitoring SingTel saw them dropping customers and market share in the South Asia region, as shown in the following screen shots.
In Pakistan, PTCL (AS17557) and their chief competitor, Transworld (AS38193), were both impacted by the loss of SingTel via SMW4. While neither provider suffered significant outages, they both had to shift traffic to their surviving providers, as shown in the following graphics. The number of routes PTCL sent to SingTel was cut in half with Telecom Malaysia (AS4788) picking up the slack. In contrast, Transworld turned to Indian provider Reliance Communications (AS15412) to handle the nearly 1500 networks formerly routed to SingTel.
When we analyze latencies into Pakistan from around the world, we see that the cable cut had little impact on latencies from the west to either of these Pakistani providers with international connectivity.
However, looking from the east, we observe dramatic increases in latencies to Pakistan via the respective surrogates for SingTel. Traceroutes from Singapore to PTCL via TMnet hairpin through Europe, while traceroutes to Transworld via Reliance loop the long way around the world to get to Pakistan from Singapore. Latencies of 110 — 150 ms are slow but acceptable for many kinds of international Internet applications, like VoIP, but as roundtrip latencies go above 300ms they lead to very poor performance causing many online applications to degrade or fail.
As mentioned earlier, this incident did not only impact providers in South Asia, service to Kuwait and UAE through UAE-based provider Etisalat (AS8966) was also impacted, as shown below.
The impact of a cable break near the terminus of a nearly 19,000km cable has been far reaching and wide spread. Bangladesh isn't the only country in South Asia with diminished Internet capacity. Service providers throughout the region have been forced to react. While SingTel is hoping for a quick return to service for SMW4 for customers in South Asia and the Middle East, officials in Bangladesh have stated that service may not return to normal until mid-July.
Perhaps SingTel is working on alternatives to SMW4? And perhaps the Bangladesh Telecommunication Regulatory Commission will be inspired to take action to increase Bangladesh's telecoms diversity? We have some suggestions, give us a call.