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How much effect does contention have?

clatz
Grafter
Posts: 95
Registered: 21-08-2007

How much effect does contention have?

I have a 1mb connection, but notice that, especially at weekends, I am often only able to achieve speeds of 750kbs (or worse). Last night it was down to 430kbps

I have put it down to line contention with other users, but am I correct in that assumption?. Generally, during the week I get nearer to the 940kbps I expect.

Is there any way of telling how many other users share the line I use?.

The worst of it is, that it causes a lot of lag when online gaming. When I first connected to Plusnet I always got full speed.

Disappointing really.....
14 REPLIES
N/A

How much effect does contention have?

First off, check your BT exchange on the Exchange chacker. You are concerned with the "VP capacity" result only.

If this is red or amber, this is your possible problem. It should also quote a date to be fixed.

If it shows green, it could still be a problem, that BT are not aware of or hasn't made it into the database yet.

It is not possible to know how many people you are sharing with, as BT do not release this sort of detail.
lowry
Grafter
Posts: 478
Registered: 08-04-2007

How much effect does contention have?

ADSL with a 50:1 contention ratio is designed for 'bursty' usage. For example, say a user is browsing the web and downloading windows media player. There will be bursts and lulls in bandwidth usage between loading the webpages and viewing them, and there will be a short burst for the period it takes to download the Windows Media Player installer. This means that while one person is loading a webpage, there should be bandwidth for that because another person is viewing one, etc.

Say, 10 users were on a 2MBit pipe on the PlusNet network, and they were all on 512k connections. This would mean a contention ratio of 10:1 (I think), and so if all of the users on the pipe were downloading, then I may just get around 51kbit/sec downstream as contention is 'kicking in'.

The problem PlusNet had with the heavy users was that they did not have 'bursty' usage and were using their connections to download 24/7, thus causing poor performance and completely turning the idea of contention on its head.

On BT IPStream Home 500 (the wholesale product Broadband Home is based on), the advertised contention is 50:1, and you may begin to feel contention a bit if your Virtual Path at the exchange is crowded. 98% of the time you should not be experiencing slowdowns because of contention on the PlusNet network because there should always be a sufficient amount of capacity available across the BT Central pipes for all of the users. However, PlusNet could not cope with all their users going 'full tilt' so there is a contention ratio (although not specifically disclosed) for the PlusNet network aswell. It would not be very high though.

Useful Links

matt Wink
N/A

How much effect does contention have?

Oh dear - I have just used the usertools exchange checker and I was told (twice) that "This exchange is not enabled yet" Sad but, actually, it was enabled on 20th October and I've been using it since the 30th...

Is there a more up-to-date version somewhere :?:

Thanks,
Tim
lowry
Grafter
Posts: 478
Registered: 08-04-2007

How much effect does contention have?

You could try the exchange checker at www.samknows.com

matt Wink
N/A

How much effect does contention have?

Which exchange are you on?

I will check the database, as it should only say it isn't enabled, if the BT data I have says it isn't.
N/A

How much effect does contention have?

Thanks for the replies, the exchange is Pluckley (01233840xxx) - I tried www.samknows.com and it gave condition 'green' - that's good? (You can tell how much I know about this Shockedops: )

Thanks again,
Tim
N/A

How much effect does contention have?

My exchange (STEPNEY GREEN) has been on red for about 6 weeks now, and the fix date keeps slipping - it was 7th Nov, now its 22nd Dec.

I guess this is a BT thing and nothing to do with Plusnet.
lowry
Grafter
Posts: 478
Registered: 08-04-2007

How much effect does contention have?

It is a BT thing, yes. The data used for the exchange checker (as far as I understand it) is data from BT and so is nothing to do with PlusNet. The date for the fix that your exchange is getting could have been put back for a number of reasons such as the lack of availability of a suitable BT engineer or other worse-off exchanges taking priority.

matt Wink
clatz
Grafter
Posts: 95
Registered: 21-08-2007

How much effect does contention have?

Great set of answers, thanks. Also, I had never come across the SamKnows web site, what a terrific resource.

Great buch we've got here on Plusnet.

Just tried 4 more speed tests with a 1 minute interval between them (time: 20:30 STD: 01983) and this time it gave me 933, 911, 941, 950kbps. Since my first posting I had my router powered off. I wonder if you pick up different quality lines each time you reboot?

Thanks all for your help and replies.
lowry
Grafter
Posts: 478
Registered: 08-04-2007

How much effect does contention have?

Speedtests aren't the be-all and end-all and are not extremely accurate (although they are quite accurate Wink). As long as you experience between 110-120kb/sec throughput on downloads on 1MB then you should be fine. There is not that much variation between 933, 911, 941, and 950kbps so I don't think you have anything to worry about.

Remember also that a 5% speed decrease is nothing to be concerned about, but it will be more noticeable on 1MB or 2MB than on 512k. For example, say you normally got 477kbps on 512k (according to the ADSLGuide speedtest) but you experienced a 5% drop in speed, you would receive about 453kbps. You would not really notice the difference. On 2MB however, say you got 1890kbps normally but experienced a 5% drop in speed then you would get about 1795kbps. This may look quite a bit less, but proportionally it is very small.

Sorry I rambled Smiley but hopefully you see my point.

matt Wink
clatz
Grafter
Posts: 95
Registered: 21-08-2007

How much effect does contention have?

Yes Matt, I see you point and well made it was too ;-)

I'm not worried about the recent set of tests, it's when I get 450, 550 and 750kbps, which I've been experiencing recently.

Initially I thought it may be because I've just rebuilt my PC, but my other PC experiences the same throughput.

It's not a real problem because I'm not a heavey downloader (approx 7GB a month) but it affects me when I'm gaming. I've had more lag in the past two weeks than I have ever experienced before, hence why I started looking at my speeds.
the_norris
Grafter
Posts: 463
Registered: 02-08-2007

How much effect does contention have?

Could this problem be caused by the current issue with BT load balancing ADSL connection on the Centrals (Fat pipe)?


Phil
N/A

How much effect does contention have?

If it was related to the load balancing issues, then reconnecting a few times would normaly cutre that.

As for the "Pluckley" exchange, thanks for that.

I see that exchange had it's RFS pulled forward wince the last major update to the DB.

Unfortunatly, I am nice and busy for this week, and thw weekend doesn't make anything fun available either. As such, i am unable to update the database.

I will plan for a major DB update as soon as though, which usualy takes 1/2 a day because of the data involved.
N/A

How much effect does contention have?

Thanks Philip - sorry to give you extra work at a busy time Cry
Tim