Africa's Internet weaknesses highlighted by Seacom repeater fault

6th July 2010 By: Christy van der Merwe

The Seacom undersea fibre-optic cable fault, which has led to Internet browsing frustration across Africa over the past two days, has highlighted the need for improvements to system redundancy, which would ensure rapid network restoration when faults occur.

A key element of greater resilience would be the acquisition by Internet service providers (ISPs) of capacity from multiple systems, which would enable them to re-route traffic when their primary platform fails. However, currently, ISPs are constrained by Africa's limited international connectivity, brought by submarine cables.

"Seacom is part of an African Internet build-up, so it's a work in progress. The image one must have, is that Seacom is one element of an African Internet and, as other cable systems come on line, there will be redundancy between the systems," Seacom South Africa GM Martin Sanne told Engineering News Online.

He added that the current failure, which was attracting much attention, could be called catastrophic, particularly because the other elements enabling an "African Internet" were not yet in place.

Seacom noted that one of the elements that it is working on, which should be in place within months, is the installation of routers in the Internet protocol (IP) multiprotocol label switching (MPLS) capability on to the landing points of the cable.

"With the IP MPLS in place, a switchover to other capacity actually becomes quite simple. It's not as difficult as reconfiguring a network, because you can step out of the Seacom cloud, and into another IP could by simply changing some addresses. So, you are actually accessing the Internet per se, at the landing point," Sanne explains.

In other words, should the same fault reoccur in a few months from now, Seacom assures that the scenario will be "very different" and far less disruptive.

"Putting a $600-million cable into the water is step one. The next step is to put in place the backhaul, and get to all your destinations. While putting in the backhaul, you also look at all your resilience options, and as your connectivity on the terrestrial side grows, so do all your paths and options grow as well. When the other cable systems being built come into play, it will help," said Sanne.

"We have found that generally, in South Africa, most bigger clients have some kind of redundancy anyway, which is taking capacity off more than one cable anyway,' said Sonne. It was the Seacom clients on the Eastern seaboard that needed more options.

The process of repairing the Seacom undersea cable repeater has been activated and the parts required to replace the faulty repeater were being located and tested.

Seacom on Monday confirmed that its service was down when a repeater failed on segment nine of the cable, which is offshore to the north of Mombasa, and resulting in service downtime between Mumbai, in India and Mombasa, in Kenya.

Sanne explained that a repeater failure such as this was "extremely unusual", as repeaters were robust and designed to last for 20 years without having to be touched. He added that short of the cable being physically cut, repeater failure was one of the worst problems that could affect a cable system.

To alleviate such a risk, one would need to lay a dual cable, which has huge implications for an already costly project, at $600-million to lay a single cable network like Seacom.

It is not possible for the company to state exactly what has gone wrong with the unit, until it is lifted to surface and inspected. "Because the repeater lies about 1 000m below the water level, it is a mighty task to get to it before you can actually analyse it to see what the problem is."

The repeater is a large, complex unit, essentially a large box of optical electronics. The repeaters are needed because a light signal is transmitted along the fibre cable and that light signal needs to be regenerated at certain intervals in order to ensure the quality of the signal.

The number of repeaters along a cable system depend on design concepts of the project. Some systems try to work with higher powers and less repeaters, and others deploy more repeaters at lower powers. It also depends on how many branching units a cable has, and the physical topography of where the cable has to go, and the number of landing stations.

In locating the fault, Sonne explained that one can ‘ping' the signal, or reflect the signal, so that one could determine a fibre break in the cable down to very short distances, just by taking reflective signal. "So one knows which element it is and you can localise that repeater."

Seacom has agreements with a Dubai-based company called E-Marine, and a depot there with spare parts for the cable. As soon as the company was aware of the problem where it was necessary to recover the cable, the ship was activated, and informed about what kind of fault was anticipated - in this case, a repeater fault.

E-Marine then collects the necessary equipment from the Seacom depot, and sails to the location identified by Seacom. The company then sends a robot down to recover the cable, and bring it to surface, where the repeater is then cut out of the cable, and a new repeater is inserted.

The actual repair of the cable repeater takes only a few hours, however the other elements of the process, such as sailing to the location, and lifting up the cable, are what takes time. The ship is described as a floating laboratory, with the ability to splice fibre optics on board.

Overall, the repair process is described as "very expensive".

Meanwhile, Seacom told customers that it was "actively seeking options to restore the service".

"Normal service might not be 100% possible, but to the extent that we can restore the service so that one does not actually see that there is a problem on Seacom, we will. It might limit capacity a bit, but we can restore service," said Sanne.

He stated that one of the options was to continue prodding the repeater itself, because it is not actually completely dead, so Seacom was working with it and finding out if it was tolerating other wavelengths.

"So there is still hope there - it's like a satellite out in space, where one is actually communicating with it and trying to find a way around issues that have developed.
So that is one ray of hope," said Sanne.

Another option being pursued, relates to restoration procedures, whereby the company requests other cable operators, such as the East African Marine System, dubbed Teams, and SAT-3, to reconfigure the circuits which run through the Seacom system, on to their system.

"We offer those options but they are limited by capacity - obviously they cannot take up all the capacity that goes along the Seacom cable."

Services could be restored to a level where the individual customers were fine, but they have restricted capacity. This option was also a question of cost, availability, and of how long the problem was going to carry on for.