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Author Topic: Upload Contention Ratios  (Read 3503 times)

innov8

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« on: August 13, 2006, 11:23:02 AM »

Most of the talk on contention rations revolves around download speeds and whilst ADSL upload works slightly differently , I can't find any ISP that clearly states how the contention affects upload speeds. In particular ADSL MAX.
Do anyone know what the contention rules are on upload speeds ??
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Astral

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« Reply #1 on: August 13, 2006, 11:37:02 AM »

Hi innov8

Welcome to the site I hope you find it useful. Like the nick BTW :D

Upload is theoretically subject to the same contention, but as you are using so little bandwidth compared to the download you are unlikely to see any serious deterioration in speed. Mine only varies between about 364 to 374kbps whereas my download can vary from 2 to 6.5Mbps.

Hope that answers your question.
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innov8

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« Reply #2 on: August 13, 2006, 12:04:17 PM »

Hi Astral, glad you like the nick.

I have read the site about contention ratios and its excellent.

Do you know why most ISPs are still quoting the 20:1 and 50:1 contentions even though BTw now quote acceptable speeds instead ?

Also the acceptable speeds are only quoted up to 2Mb any reason why ?

Also Also ! I get the feeling that some ISPs like Griffin http://www.griffin.com/Products/Business/Internet/Broadband.aspx are stating BTw new "acceptable download speeds" and making look like they offer something different or better but in actual fact all IPStream ISPs are subject to the same contentions at the exchange (unless they have their own LLU equipment in the exchange). Do you think that this is just a marketing ploy , and that the other ISPs have missed this marketing trick ?
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kitz

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« Reply #3 on: August 13, 2006, 12:29:36 PM »

Astral is correct its theoretically the same, since you share x amount of available upstream bandwidth with the same number of users as you do the downstream.

Because adsl is Asymmetric..  and simply because most people use downstream with hardly any upstream (ie surfing), then upstream has never really been a major concern.

The BTw central pipes generally allow for 50%* of capacity for upstream.  So a 622Mb central will have 622Mb* downstream and 311Mb* upstream.

*The 50% is a guideline, and although 622Mb would be the maximum downstream, upstream is more flexible, and you can go over the 311Mb upstream but this would then eat into any available downstream.

The most costly expense to IPStream ISPs is BT Central costs, and therefore its downloads that cost them during peak times.  However saying that I have seen upstream on occasions being near fully utilised due to the likes of p2p traffic.

Contention rules now are *old hat* and BTw stopped quoting contention ratios in October last year, and instead now talk about acceptable throughput levels.
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kitz

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« Reply #4 on: August 13, 2006, 12:45:27 PM »

>> Do you know why most ISPs are still quoting the 20:1 and 50:1 contentions even though BTw now quote acceptable speeds instead ?

Possibly because so many users are used to seeing 20:1 and 50:1 to distinguish between the Home and Office products.
Contention ratio doesnt really mean that much these days and yes minimum acceptable speeds are a fair better way of setting customer expectation.

BT never let the backhauls run at the quoted contention levels anyhow.. and when it comes to the BT centrals- its entirely possible to have them contended at say 100:1 and still see acceptable throughput.
The earlish adopters of adsl in general could be said to be the heavier users, whilst I think its fair to say that most people getting adsl for the first time today only do so for mail/surfing and will likely only be using around 1GB pm.
Therefore more of these types of users can share without any deterioration.

>> Also the acceptable speeds are only quoted up to 2Mb any reason why ?


Cause thats what BT quote

Quote
Max services where the line operates at 2Mb or above may provide End Users, at peak times, with the same data throughput as they would have experienced on an equivalent 2Mb fixed rate Broadband service.
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>> making look like they offer something different or better

In theory minimum acceptable speeds are better than contention ratios - heck if BT did allow the VPs to run at speeds of the contention levels quoted, then things would be pretty dire.

>> Do you think that this is just a marketing ploy

/me thinks theres been too much spin as it is about contention ratios. ;)
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Astral

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« Reply #5 on: August 13, 2006, 01:08:43 PM »

Hi innov8

I held off replying to your last post cos I knew Kitz was back and you'd get a five star answer form the one who knows. Also I got to learn something as well. :D
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