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Originally Posted by James Henry
Contention is nothing until it becomes visible.
DSL has a fundamental advantage in that the last mile is dedicated bandwidth between customer and DSLAM, and backhauls tend to be larger than the current 38 Mbps max cable offers each segment.
For example my own ISP has 1Gbps shared between its' customers on my exchange. Most of a
Not really appropriate to say that cable has a lower or higher contention ratio, the contention bottleneck on DSL is further away from the customer and easier to upgrade usually. The flipside obviously is that cable brings a higher max bandwidth to the consumer.
You've actually completely contradicted the 'commonly held wisdom' around cable and DSL. The usual argument is that while DSL offers a more stable speed cable offers a higher but less stable maximum.
The availability argument isn't really much of one. Because so little of the country is covered and enabled for broadband internet these unbundled services are as available as cable modem service, if not more so, and will certainly be more available within 6 months.
EDIT: I also think you've misunderstood what the 'up to' part means. It's actually more of a reference to the distance limits that ADSL has, IE unlike cable there is no active network so the speed achievable degrades the further one is from the operator's equipment. In cable's case if you are on 10Mbit then so long as all is working ok and the bandwidth is available you'll get 10Mbit, on DSL if you are within x KM of the exchange you'll get 10Mbit, a little further away 9, etc.
That's a cable advantage, but it's been undone somewhat by the ADSL2+ rollout and 'relatively' short lines in the UK meaning that most of the people in cable areas are usually able to get more than 10Mbit/s over ADSL2+ services.
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First of all I don't wish to discredit your knowledge on these things as you obviously know more about some of the more intricate things then I do
Lets look at it like this. DSL has two factors involed in you getting the speed. Line length and contention of pipe from DSLAM to ISP.
Cable has the single factor of contention from customer to CMTS. I would like to think core is a situation that doesn't require as much thought as the access networks, after all 'Plusnet issues' don't appear to be apparent on ntl.
So yes, a telephone loop is not shared like cable and cable does not have the same contention point. However channel bonding can negate the smaller share, even though its a wonder now to those who cannot monitor a uBR of its usage, how a DOCSIS 1.1 64QAM system can hold the the allocate users on a card and still can see 10mbit, so I cannot see why the same cannot be said when the speeds are higher offered on a system which has greater aggregate bandwidth with somewhat the same ratio. Not to mention the evil traffic shaping gear they have too
BT's 21 CN network of bringing fibre closer to the home, well ntl is already there with fibre to the node. So if we are going to compare upgrades, BT are moving fibre up to negate the effects of line length and try and offer better speeds come ADSL2+, VDSL2 or whatever else there is by then, as opposed to ntl who are making use of the existing bandwidth that is already there. In fact, even before channel bonding, I know ntl are using a second downstream in one area that isn't Guildford.
It cannot be denied that the gigabits of bandwidth available on coax networks is there, its just not being used, whether that be due to finance, technology, needed technology upgrades or dumbass management. I'm guessing possibly all four with ntl
