The scale of core networks is astounding, and the news that Sky has recently installed a 100 Gbps fibre link between Birmingham and London underlines this. The Sky core network comprises of some 7,000 km of fibre optic cables generally running alongside the old canal infrastructure. It also underscores the ability of fibre to cope with massive amounts of traffic, since this 100 Gbps link will utilise Dense Wavelength Division Multiplexing (DWDM) to allow it to carry light at varying frequencies giving a total capacity of 7,000 Gbps (7 Tbps - Tera bits per second). To give some idea of the potential capacity this is enough capacity for 4.6 million people to be watching a different streamed HD movie at the same time.
With Sky's approach to offering a non traffic managed service to its LLU customers with unlimited packages available too, then having more than enough capacity in the core network is crucial to keeping customers happy. One interesting aspect of the Sky network, is that by keeping traffic from services like Anytime+ on its own network, the cost of providing this Video on Demand (VoD) library to its Broadband/Satellite TV bundle customers is reduced.
The firm predicts that the current 350 Gbps of traffic it sees from customers is set to double to 700 Gbps by June 2012. With some 3.2 million customers on the LLU service, this equates to 110 Kbps (Kilo bits per second) per customer, though usage patterns mean that even if all their broadband connections were online, it is unlikely they would all be actively transferring data.
It is not only the core network receiving upgrades, since March 2011 some 970 exchanges have seen capacity upgrades, and the current number of unbundled exchanges at 1,735 is set to increase to 1,932 by the end of January 2012, giving a coverage level of around 86% to 90% of UK households for its ADSL2+ based LLU service.