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Cor blimey: Virgin Media pipes 152Mb fibre to 100,000 East Londoners

AndrueC Silver badge

it would be really great if the upload speed was even a quarter as fast as the download speed.

Sadly the architecture of cable networks imposes limitations. Because several properties are sharing a single cable something has to prevent collisions (put simply something has to stop you and your neighbour both trying to send a packet at the same time). DOCSIS3.0 helped quite a lot but it's still an uphill struggle. xDSL doesn't have this particular limitation because everyone has a dedicated cable - in theory(*) an xDSL modem can use any frequency it wants for whatever purpose it wants whenever it wants.

I think it's fair to say that xDSL is topologically more suited to bi-directional networking than cable (no surprise - given the original intent of cable). But later versions of DOCSIS have done a helluva lot to workaround the limitations of the basic architecture. There may be more to come and the guys doing the research are well aware that upload speed is important.

(*)In practice it can't. Frequency plans exist to minimise interference between cables in the same bundle and the DSLAM will almost certainly only support particular up or downstream rates.

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