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How does BT contention work?

Dizzley
Grafter
Posts: 275
Registered: 17-04-2007

How does BT contention work?

It looks like I'm seeing peak time contention in the BT network.
I say that because my speeds plummet in peak hours.

All this is "network managed" by BT isn't it?

I was wondering...

If at peak times all lines will get the same managed speed "ceiling". This should of course be packet-shaped so web etc. is protected. BUT I don't think the BT infrastructure can handle that. - If that is true then the ceiling, say 800kbps, would be applied to all traffic before the ISPs can get to do their own "management".

And so at peak times, web, voip, streaming etc will all suffer. The bottleneck will be inside the BT network.

Is this what we are experiencing now at peak times in the new MaxDSL world?
Or does some QoS/packet shaping take place at BT?

Yours curiously,
14 REPLIES
Alecto
Grafter
Posts: 2,886
Registered: 30-07-2007

How does BT contention work?

Take one outdated creaking telephone network, that just about copes with 512k connections.
.
Stuff it full of 2Mb connections and watch what happens.

Then, in case this isn't slow enough, stuff it full of 8Mb connections and go and put the kettle on while waiting to download at peak time along with everybody else..

Roll on 24Mb!!
Dizzley
Grafter
Posts: 275
Registered: 17-04-2007

How does BT contention work?

The $64,000 question:
:?: Does BT contention squish even high-priority traffic like Voip at peak times? :?:

Anyone?

If so, then all efforts at managing traffic by PN have only a very indirect effect on the quality of service we all see. And "up to 8Mb" means "whatever is left in the BT pipework when everyone else has finished with it" Evil

The real limiting factor then, is between me and PN and we can do diddley-squat about it.

Go back to your shanties all you P2P users and give me my bandwidth back! Wink

Edited to give added rant factor
N/A

How does BT contention work?

BT don't care what application you're using - web, FTP, VOIP. All they are concerned about is ATM packets which run below IP. In the world of BT, Business class traffic gets priority over residential stuff.
Dizzley
Grafter
Posts: 275
Registered: 17-04-2007

How does BT contention work?

As I said: the high-value services like VOIP and even web browsing are going to be hammered just as much as P2P in peak periods.

The penny drops here at Disley Towers:

No wonder there is ISP packet shaping - BT exchange contention is the limiting factor for a browsing experience. The ISPs like PlusNet can only squeeze at their end to try to improve the QoS effects on the whole network.

If there were no exchange contention then PN's traffic management would have more of an effect on "the user experience".

ISPs who don't play the game and manage low priority traffic right down will indirectly cause the exchanges to suffer contention. Sad I would not be surprised if this kind of packet shaping is part of the agreement with ISPs when they buy BT BB wholesale.

My next question is: was it right to open MaxDSL to everyone if they needed it or not and without charging a premium? The general MaxDSL experience is going to be naff in peak periods, in other words, "when everybody wants to use the service".

Looking into the 20:1 contention products RIGHT NOW.
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How does BT contention work?

Gone for the peak option on the vote, although in fact its actually a constant 5.5-6.5 with Stable Rate of 8.
Thought this option was closest to my situation.

Very lucky, because we are in an area dominated by industry - most of whom I suspect will be using private circuits.

Can't ever see P2P disappearing, people seem addicated to it!

When oh when will network capacity be increased to cope with what we need now in terms of throughput? At this rate I can't see web video on demand etc taking off in a big way. (Unless they use huge P2P networks to deliver it)
Dizzley
Grafter
Posts: 275
Registered: 17-04-2007

How does BT contention work?

Thanks for that James. Do you never see better than 5.5-6.5Mbps out of peak hours?

I'm seeing speeds as low as 600k at peak time. I'm assuming this is peak time contention. However, my local exchange remains green on the PN Usertools exchange checker.

I would consider 5-6M acceptable but to see regular dips to below 1M is annoying. How could I ever consider using Video-on-demand or Voip seriously. It's so galling as my line is very comfortable with a realistic MSR of 8000 and SNR margin of 8.1 at 8128M sync.
N/A

How does BT contention work?

I'll have to have a crack in the morning if I get out of bed early enough to beat the users in!

I think I did see it once or twice around the 7.5 mark, and perhaps sometimes higher, but perhaps that was during the training period.

Stats for ref:

DSL Status
Connection Status Connected
Upstream Rate (Kbps) 832
Downstream Rate (Kbps) 8128
US Margin 17
DS Margin 11
Modulation MMODE
LOS Errors 0
DS Line Attenuation 27
US Line Attenuation 24
Path Mode Fast Path
N/A

How does BT contention work?

Quote
When oh when will network capacity be increased to cope with what we need now in terms of throughput? At this rate I can't see web video on demand etc taking off in a big way. (Unless they use huge P2P networks to deliver it)

Basically, capacity will never be increased. Not until the price of centrals are no longer artificially kept high, which will be after LLU has taken off, at least.
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How does BT contention work?

Quote
I'm seeing speeds as low as 600k at peak time. I'm assuming this is peak time contention. However, my local exchange remains green on the PN Usertools exchange checker.

You're lucky disley...

Since beginning my ride on the MaxDsl roller-coaster I've had the feeling that peak-times are worse than ever. The image below shows the extent that it's dropped too over the past 24hrs. I'm quite a distance from the exchange and was always told 512 would be my max, but since MaxDsl kicked in I was happy to be syncing between 1200 - 1400 even though only getting a maximum of around 1000 kbps download speed. Since last night from around ten o'clock though it's dropped off to the high 400s (woohoo!). Not just at peak time from the looks of things either, I'm currently synced at 1344 but getting 480 or so download speed.

My exchange shows green on the PlusNet checker too, although it's not been updated since the 10 April or so. Interestingly, I tried the PlusNet BB faults checker and it stops me going through the complete procedure when it flags up the same exchange as RED and having an extremely high contention at the moment (6:30pm tonight).



Just have to sit it out for the moment and see how things settle along with the masses of other poking-around-in-the-dark Plusnetters. Sad

Cheers,
Brian
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How does BT contention work?

everything says its gone through the system however im still only syncing at my original speed, had to post a support ticket blah.

DSL Status
Connection Status Connected
Upstream Rate (Kbps) 288
Downstream Rate (Kbps) 2272
US Margin 28
DS Margin 31
Modulation MMODE
LOS Errors 0
DS Line Attenuation 18
US Line Attenuation 17
Path Mode Fast Path

I dont suffer with contention at any time, just so happens i live in a small village, long time waiting to obtain broadband where i live but atleast better than what seems to be large towns and cities as you all mutilate the exchanges and suffer speed loss.

Rural britain pwns u
N/A

How does BT contention work?

I'm wondering if there is a problem with the plus.net exchange status checker. It has not been updated since April 10th for me too - and all the ones before that were at a weekly interval. The prodigy tester available at: http://www.prodigynet.co.uk/menu.php?page=support/linecheck shows that the exchange is on Amber. However, this adsl specific checker: http://www.prodigynet.co.uk/menu.php?page=support/linecheck which shows more information shows share capacity on my exchange.
willhome
Grafter
Posts: 272
Registered: 06-08-2007

How does BT contention work?

personally on my exchange yes my maxdsl goes from 6+mbps to 1.5-2.5 peak hours...

but i dont see this causing problems. my gaming pings stay low, VOIP/ts is solid clear and low pings and web http is just as fast as it was on 2mb.

only thing different i feel at peak hours is my connection for downloading files is slower
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Contention

PAYG and Premier contention is 50:1 on IPSream Max with BT and managed to 20:1 at Plusnet or so I am told - this being the case the explanation of contention in the help pages needs updating!, or is someone at Plusnet telling porkies?
Shockedops:
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How does BT contention work?

To thos considering it: I wouldn't rush to pay out more for the so-called 20:1 contention products, Plus.net have informed me, after I queried why my line was so damn slow after being 'Max'd' , that contention is no longer how they manage traffic.

I then asked them what beneft we business subscribers got for paying over double the fee of the home users and they have so far avoided responding.

I would get some clarification from them in writing before volunterring to pay more!!