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Author Topic: BT or other ISP package for long line length near or beyond adsl limit  (Read 11420 times)

setecio

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Re: BT or other ISP package for long line length near or beyond adsl limit
« Reply #15 on: January 08, 2008, 10:24:18 AM »

mmm ???

I asked Zen to check the line and it came back as red on the 250 and green on the max (Zen 800 lite) , so they said they would try the max adsl product and not the 250 as the tests indicated there was more chance of getting a successful adsl connection on the max. They said BT's tests were accurate.

This confuses me  ???

I thought the max only went down to 512 and the purpose of the 250 was to go lower and achieve a connection, albeit at a lower speed but still a connection where 512 won't connect. Why would 250 be red if max was green ?

 ???

Any thoughts ?
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soms

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Re: BT or other ISP package for long line length near or beyond adsl limit
« Reply #16 on: January 08, 2008, 11:19:04 AM »

I think Max can sync down to some very low speeds. Certainly down to 256k I would think.

I have only had a little experience of this when our line was playing up with the BT home hub and we were getting weird speeds like 344kbps downstream.

I recon, but cannot confirm that you can get speeds down to between 100kbps and 200kbps. No doubt some of the better informed here will know the lowest official Max IP profiles which roughly correlate to sync speed.
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Astral

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Re: BT or other ISP package for long line length near or beyond adsl limit
« Reply #17 on: January 08, 2008, 11:24:28 AM »

Quote
Why would 250 be red if max was green ?

It may be that none of the lines on your exchange are so long that 250 was the best service that could be provided. If that is the case BT wouldn't put the kit in to provide that service if there was going to be no demand. This is purely a guess I have to say.
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roseway

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Re: BT or other ISP package for long line length near or beyond adsl limit
« Reply #18 on: January 08, 2008, 11:39:32 AM »

There are specific requirements which must be met before a fixed-speed connection will be implemented by BT. But ADSL Max is a 'suck it and see' service, and they'll give it a try almost anywhere.
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  Eric

guest

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Re: BT or other ISP package for long line length near or beyond adsl limit
« Reply #19 on: January 08, 2008, 02:15:07 PM »

Max has a minimum sync rate of 160kbps, which is a profile of 135kbps.
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kitz

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Re: BT or other ISP package for long line length near or beyond adsl limit
« Reply #20 on: January 08, 2008, 02:56:11 PM »

The lowest sync on max is 160 kbps -  256 kbps  which will give you an IP profile of 135 kbps. (throughput speed).
Theres a full list of the possible max sync speeds on the bottom of the IP profile page.

Max allows fluctuating speeds depending on the conditions at the time, *
whilst the 250/500 service although fixed downstream is also classified as rdsl, because it can "borrow" from the upstream to be able to maintain the downstream sync.  Upstream can rate on these products can adapt between 64-288 kbps.


--------------------

*although max generally is thought of being rate adaptive, in the cases of some poorer lines it is possible for the BTw process to "cap" the downstream speed in order to maintain stability. 
There was a case on this forum, where this had happened to a user..  and it confused both us and the ISP at the time since the only indication that this had occurred was that the line suddenly became "FAST" rather than "INTERLEAVED". - linky.

------------

>> Warning - while you were typing a new reply has been posted. You may wish to review your post.
Sorry I started typing this ages ago - but got distracted by my daughter who's poorly and "demanded" my attention.
I see rizla has posted the profile already - but I still posted cause it also has some additional info.


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guest

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Re: BT or other ISP package for long line length near or beyond adsl limit
« Reply #21 on: January 08, 2008, 03:19:26 PM »

I got it from the table on your site anyway :)
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setecio

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Re: BT or other ISP package for long line length near or beyond adsl limit
« Reply #22 on: January 08, 2008, 04:03:44 PM »

So, to check I'm understanding this correctly, initially it doesn't matter whether they go for a 250 or a max service as both will be equally likely to connect if adsl is possible on the line. The difference is that a max service may turn out to be less stable on poorer lines, in which case changing to a 250 service, if possible, should prove more stable.

Therefore it is, as Zen did say, better to start with the max service, since it may pleasantly connect at 512 or faster. If it doesn't connect, then 250 won't connect either, since the only advantage of a 250 service is long term stability, not a higher likelihood to achieve a connection.

Would that be correct ?
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kitz

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Re: BT or other ISP package for long line length near or beyond adsl limit
« Reply #23 on: January 08, 2008, 11:01:31 PM »

Hmmm  thats about the gist of it yes.

However...  theres a big BUT...  in that max dsl doesnt always work well with some long lines - and its not always the best solution.

1) The IP profile can be a PITA on unstable connections and you can find your speeds being artificially lowered for several days due to the IPprofile.
2) Because of the way Maxdsl works, then there are a few things that the DLM can do to try and stabilise a line.  One of those is increasing the target SNR.
- If for any reason the DLM decides that it wants to increase your Target SNR to say 12 or 15dB.. then I'd hate to think of the effect it could have on sync speeds that are going to be pretty low to start with. :(

I kept my mouth shut first time round... because if that what BT are recommending then who am I really to argue with them :/

In all fairness Max perhaps would be interesting to see just what your line could sync at first..  but the bit where it can often fall down on longer lines is because of the DLM process if that kicks in.  Possibly BT have realised this and hence why the seldom seen capped maxdsl services.  If and when, or how that kicks in I really dont know I'm afraid.

So max could be better to start with - but then it does depend on how your line performs.. and even BT wont know that until it's connected.
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Azzaka

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Re: BT or other ISP package for long line length near or beyond adsl limit
« Reply #24 on: January 09, 2008, 08:20:12 AM »

Sorry i'm late,

Basically DSL Max is likely to carry the signal further and hence you can get an 8000lite and not a 250kb line. However, if your order dsl and keep it for any period and then find it becomes unstable, the line will likely be marked as NO DSL and a False Green will be issued.

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mr_chris

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Re: BT or other ISP package for long line length near or beyond adsl limit
« Reply #25 on: January 09, 2008, 11:45:25 AM »

Basically DSL Max is likely to carry the signal further

If this line syncs successfully on Max but low-ish like 200kbps, would Zen consider keeping the line on MaxDSL but charging for a Home250 account? :)
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Chris

kitz

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Re: BT or other ISP package for long line length near or beyond adsl limit
« Reply #26 on: January 09, 2008, 01:25:44 PM »

Thanks azzaka :)


>>> If this line syncs successfully on Max but low-ish like 200kbps, would Zen consider keeping the line on MaxDSL but charging for a Home250 account

This is something that occured to me yesterday - then with my own dsl going off yesterday eve I forgot again, but mentioned it on the phone to chris last night.


It would obviously depend on setecio's usage requirements but:-
Zens home 250 unlimited is 17.99 where as the 8000 Active is 24.99

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Also if the line initially syncs at 250/512 and is reasonably stable - but then the DLM and IP profile start mucking around...
and if the DLM starts putting a silly high target SNR on the line would zen perhaps consider doing a modify order to a rdsl 250?

I know my own ISP will certainly do this with long lines and 512/1Mb accounts - its just that they dont do a specific 250 account.
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Azzaka

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Re: BT or other ISP package for long line length near or beyond adsl limit
« Reply #27 on: January 09, 2008, 03:55:37 PM »

If the sync speed is only about 200-300kb/s the we can try to cap it on an 8mb line and call it a home250 account. However if we can get 512kb out of it then, we'll cap- it and call it  an 8000 account.
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kitz

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Re: BT or other ISP package for long line length near or beyond adsl limit
« Reply #28 on: January 11, 2008, 02:29:51 PM »

Excellent!

Thank you :)
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