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Thursday 2 August 2007

Mainstream wakes up to broadband speeds [Lurks]

At long last it would seem there's something of a backlash against the ridiculous selling practises of broadband Internet in the UK. Pretty much all of them sell broadband by advertising the top rate that you might get, if you live every close to the exchange.Which released a report which the BBC is commenting on where the average speed of delivered broadband is 2.7Mbps. I would assume that this is a measured throughput so equates to an ADSL sync level of about 3.5Mbps.

Of course this is nowhere near the fiasco of wireless technologies being sold on a base signalling rate which has pretty much no relation whatsoever to throughput seen. The bottom line is you let companies get away with it, they'll keep boosting the numbers however they can.

The truly depressing state of things though, I happen to live virtually on top of my exchange and I'm one of the few that gets a full 8Mb ADSL sync from my exchange. However I get a bit less than 6Mb of actual throughput on that rate, or 700K/s max. So not only is national ADSL (let's ignore cherry picking LLU companies here) based on a seriously ancient standard when everyone else has done a great job of rolling out ADSL2, but it seems that there's some additional invisible handicap on actual bandwidth delivered applied within BT's network.

Protocol overhead wise, throughput on my line ought to be around 13% incorporating ATM and TCP overhead. This should equate, all said and done, to around about 900K/s throughput. The thing is, BT actually cap throughput on the DSLAMs in each exchange based on your sync speed. I discovered this because a common ADSL issue on speed regrades is that your sync can be regraded but you don't see a shift in bandwidth until something magical happens. It turns out that this is called a BRAS profile and it's basically a set of throughput cap limits for each possible ADSL sync rate.

This is the table of BRAS profiles which are allegedly employed by BT.

Download sync rate (kbits/s) BRAS profile limit (kbits/s) BRAS profile limit (kBytes/s)
8128 7150 893.75
7968 - 8127 7000 875.00
7392 - 7967 6500 812.50
6816 - 7391 6000 750.00
6240 - 6815 5500 687.50
5696 - 6239 5000 625.00
5120 - 5695 4500 562.50
4544 - 5119 4000 500.00
4000 - 4543 3500 437.50
3424 - 3999 3000 375.00
2848 - 3423 2500 312.50
2272 - 2847 2000 250.00
1728 - 2271 1500 187.50
1152 - 1727 1000 125.00
576 - 1151 500 62.50
288 - 575 250 31.25
0 - 288 250 31.25

This is, patently and demonstrably, complete lies. I think BT have a completely different set of figures. We're not talking about me getting my throughput numbers wrong here. It's not contention. It's not dependent on the time of day. The result is the same if I use my neighbours consumer DSL or my own business DSL. The figures in the boxes on the top row appear to be in actuality more like 5600 and 700.00.

Of course I like so many others have no choice. None of the LLU operators will be heading down to my south coastal retreat in order to get into exchange and install some expensive equipment. They're too busy hitting the big cities where the real low lying fruit lies, which seems a bit rotten to me really. Unfortunately we'll be getting the same treatment from BT with the 21CN network rollout, where ADSL finally becomes available, as being listed in the third quarter of 2009. So it would seem I will have to wait three years for any better quality broadband, although who's to say they wont cripple it in much the same way asBT are now.


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