Contention on BT Infinity

I've had Infinity on Business Broadband for a few months and was told that there would be a contention rate of 20 (50 on residential).

Before several others were connected to the exchange I got nearly 40Mb (I'm on a 40Mb, 100Gb usage plan). Since others have joined it's been creeping down to 20-25Mb.

Does anyone know if the Business sector is kept to Business users, i.e. 20 Business users on one connection, or are the 20 'members' a mix of Business or Residential?

I would have thought that 20 Business users after business hours would give a better speed having less actual users?

If residential I could be mixed with a batch of gamers, film downloaders or iPlayer users.

Anyone know? Not that I can do anything about it!

Mike.

Contention - I doubt it.

If your speeds have crept down it is more likely to be noise levels causing the drop in sync speed.

BT Buisness has a "minimum speed" clause and you are guaranteed that.

Thanks for your reply MHC.

It's a pity with the new system on Business Broadband with a modem and a Hub3 that you can no longer see the noise figures, but I am only 150 metres from the cabinet so would be surprised if that was the cause.

Previously we had been just over 1 mile from the exchange and there was some grotty cable from the exchange to the cabinet; but that's been overcome now.

I can't really see how the cable from the cabinet has slowly degraded over such a short period?

Mike.

Contention ratios such as 20 and 50 went out donkey's years ago, when ADSL Max was introduced.

There is NO contention. I use BT Business and started with a 40Mbps service with a potential of just under 60Mbps. When I moved to 80/20 I stated getting around 59 which has dropped slightly to just over 58. A speed test gives me 58.xx any time day or night.

If you have fropped from 40 to 25 and get that day or night then it is unlikely to be congestion.

Which modem do you have? A Huawei or ECI? With the former you can unlock it and pull of the stats.

In reply to a post by RepairExpert:

I've had Infinity on Business Broadband for a few months and was told that there would be a contention rate of 20 (50 on residential).

Before several others were connected to the exchange I got nearly 40Mb (I'm on a 40Mb, 100Gb usage plan). Since others have joined it's been creeping down to 20-25Mb.

Does anyone know if the Business sector is kept to Business users, i.e. 20 Business users on one connection, or are the 20 'members' a mix of Business or Residential?

I would have thought that 20 Business users after business hours would give a better speed having less actual users?

If residential I could be mixed with a batch of gamers, film downloaders or iPlayer users.

Anyone know? Not that I can do anything about it!

Mike.

As others have said, Contention Ratios (The method it used) went ages ago!

Depending on what kind of cabinet you are on, you'll likely be sharing a 1Gbps connection (Or more if it's a larger one) with everyone on it.

The best thing I'd recommend you do is run the BT Wholesale Speedtest and if that goes below the acceptable limit, phoning up the support channel for BT Business and quoting that checker.

Edited by chris6273 (Thu 17-Jul-14 19:26:14)

Thanks for all your comments; I need to do a few more tests at odd times to check, and I do use the BT Wholesale site which logs it there end, as well as the TBB one and the Beta version.

I'll keep you updated in a few days; will have to get up early and try it then.

Mike.

you mean no congestion.

obviously there is contention, its not a leased line product.

In reply to a post by RepairExpert:

It's a pity with the new system on Business Broadband with a modem and a Hub3 that you can no longer see the noise figures, but I am only 150 metres from the cabinet so would be surprised if that was the cause.

Probably crosstalk. As take up increases your line will be picking up more and more interference from other lines in the same cable bundle. BT are trialling something called Vectoring which is hoped will address this issue but for now there's nothing you can do.

Edited by Andrue (Fri 18-Jul-14 09:10:20)

In this context, the thread is referring to contention in the way the OP was told and how services were originally marketed.


Yes, ultimately there is contention but not the same 20:1 or 50:1 that was specified years ago. On a main exchange it will be something like 10,000:500

?
That's 20:1.

In reply to a post by RobertoS:

?
That's 20:1.

It may work out that way, but it is actually different!

Take a simple view of using voice circuits. Five customers connected to a small exchange, and only one out going line from the exchange, you have 5:1. Customer A can make a call, when customer B tries he cannot. Add another 5 customers and if you give them another single outbound line contention remains at 5:1. However, if you make both outbound line available to all users, the contention becomes 10:2 and rte chance of customer B being able tpo make a call is significantly improves.

Thanks for all your interesting replies but I have now cured the speed problem and getting 36-40Mb (my limit).

I tried my mobile android phone nearer to the modem and got 37Mb so knew the connection was OK. The main computer is in another room about 8 metres away through a double thickness wall and a large tall cupboard. It receives the BB via a USB RX on a 2 metre quality extension cable.
The modem is in exactly the same position as when installed and the RX hadn't moved (clipped to a wall shelf). However moving it just a couple of inches restored the speed. A bit of a mystery as neither units had moved position so I had wrongly discounted this as the cause.

It's amazing what a small movement positioning it can make, but I've noticed that with video senders, etc before at those SHF frequencies.

Thanks again for all your comments; I guess I was barking up the wrong tree regarding contention rates.

Mike.

So, it was a WiFi problem and not the connection!

In reply to a post by RepairExpert:

Thanks again for all your comments; I guess I was barking up the wrong tree regarding contention rates.

So after all that it was down to use of wifi for the final link? Did I miss that being mentioned somewhere? Standard advice for all issues is to start off the investigation with a wired connection.

Wifi should only ever be viewed as a convenience for mobile devices(*). It compromises reliability and throughput in exchange for not being tied to one place.

(*)Or an unfortunate situation if you really can't run a proper cable

Edited by Andrue (Fri 18-Jul-14 10:47:31)

LOL
Taking your two cases:-

1) One line, 5 customers. There is a 4:1 chance that B will not be able to make a call.

2) Two lines, 10 customers. When B tries to make his call there is a 9:1 chance that a line is in use, and an 8:1 chance that the other is in use.

He has more chance in (1).

This is nothing whatsoever to do with broadband contention anyway. That allows both A and B, or indeed all ten, to connect at the same time. The issue is the throughput speed, not the availability of connection.

I have never seen contention ratios quoted in that way.

50:1 can mean 50 users on one resource, but it can also mean 500 users on 10 resources. Both are 50:1.

I have, many times and still do see it in regular usage.

10 groups of 50 users each after 1 resource is truly 50:1 but if there are 10 resources available for 500 users it would be quoted as 500:10

In reply to a post by MHC:

I have, many times and still do see it in regular usage.

10 groups of 50 users each after 1 resource is truly 50:1 but if there are 10 resources available for 500 users it would be quoted as 500:10

That does make sense since, as your first post implied, there is a difference in performance between the two. 50:1 implies that you only get the full speed while no-one else is using it. 500:10 implies that several people can get the full speed at the same time (the equivalent of 9 other people at full speed).

Edited by Andrue (Fri 18-Jul-14 16:22:08)

Exactly.

A ratio is a ratio. End of.

If 500:10 is not the same as 50:1 then some other factor is not being stated. The ratios being compared are not of the same thing.

Contention ratios of the kind that were raised at the start of the discussion are only really applicable to fixed speed connections anyway, which is why they were ditched when ADSL Max came along. Arcane technical figures used in complex network builds, which is what the 500:10 may be about, are a different thing altogether.

I have never seen a contention ratio quoted on any type of internet service that doesnt end in :1.

The old 20:1 and 50:1 products did not have 20 and 50 people respectively sharing pipes equal to one customer's bandwidth. So BT werent following your idea either.

One such service I use is a 10:1 service and it has 100 100mbit customers sharing a 1gbit pipe.

My "arcane" was me thinking along the lines that if they supplied 10Gbps using 10 1Gbps pipes switched or load balanced or whatever for 500 leased or backhaul lines, as opposed to one 10Gbps pipe, the network architects may describe the former as 500:10 and the latter as 50:1. Purely for clarity at the design stage as to what kit is to be installed.

Both end up as 50:1 as far as their usage is concerned.

Edited by RobertoS (Fri 18-Jul-14 21:38:27)

I think it's funny this site really is full of BT fanboys.

Hearing statements like no contention on infinitii is quite funny.

There is absolutely no way BT have 1:1 bandwidth for every user. I've worked in the industry for a long time and even if the cabinet itself does not have contention the internet connections supplying the exchange or the network will certainly be running under heavy contention. Its just how the industry is able to provide low cost product to guys like you. Just because your not noticing the contention it does not mean it's not there A well setup network will be running at a very heavy contention ratio but will not be noticeable due to the usage patterns of the average user and also very effective and good queuing technology and algorithms. Things are changing though and with more content now available it's becoming harder and harder for network providers to manage contention and hence the lack of unlimited products these days bye.

In reply to a post by lektroluxe:

I think it's funny this site really is full of BT fanboys.

Shame your first and probably only post instantly devalues itself in the opening statement. It's your own time you're wasting.

In reply to a post by RobertoS:

My "arcane" was me thinking along the lines that if they supplied 10Gbps using 10 1Gbps pipes switched or load balanced or whatever for 500 leased or backhaul lines, as opposed to one 10Gbps pipe, the network architects may describe the former as 500:10 and the latter as 50:1. Purely for clarity at the design stage as to what kit is to be installed.

Both end up as 50:1 as far as their usage is concerned.

I have never seen a contention ratio on a network design, nor have I ever seen anyone care about whether a link is a single link or a few aggregated.

When aggregating together multiple links they are just rated as the sum of the bandwidth, not dealt with separately as they are bonded at layer 2.

In the case of some core links, deeper in the network and not using layer 2 bonding, a contention ratio is impossible to calculate and more to the point isn't cared about as while a group of links may be shared between 2 devices they are handling traffic going to different places and are considered as completely discrete links to be managed, and if required upgraded, separately.

Edited by deleted (Fri 18-Jul-14 22:31:47)

In reply to a post by MHC:

I have, many times and still do see it in regular usage.

10 groups of 50 users each after 1 resource is truly 50:1 but if there are 10 resources available for 500 users it would be quoted as 500:10

I can't say I have ever seen that as far as data networks go. Ratios are always quoted as lowest common denominators and regardless we aren't talking about admission control, where I could perhaps understand that, but bandwidth.

Maybe in specialist communcations systems such things are used but I can't say I've ever seen a contention ratio that didn't end in :1 used across Sky, Easynet or ntl.

Oohhhhh ROFLMAO.

Do you really mean to say you registered on this site to come in with that contribution? Accompanied by a childish insult?

Have you read the thread in full, or just the last half dozen posts?

The original point about contention was a rebuttal of the opening paragraph of the opening post. Which was:-

I've had Infinity on Business Broadband for a few months and was told that there would be a contention rate of 20 (50 on residential).

I correctly stated that those ratios went out of the window with the introduction of ADSL Max.

At no point has anyone suggested there is no contention on normal ADSLx or FTTx. The four or five people discussing contention are merely taking about the way it is expressed, with a couple accepting 500:10 as a valid description and a couple of others maintaining that is not a valid observable description. Only possibly a description at the design stage of a network. That figure is being used purely for convenience. Not as a statement of any particular real life value.

I assure you we are all well aware that ISP MSIL and internal networks are designed/budgeted at a few hundred Mbps per customer, that value varying hugely between ISPs.

As for

Things are changing though and with more content now available it's becoming harder and harder for network providers to manage contention and hence the lack of unlimited products these days

exactly the opposite is happening. All major providers now provide true unlimited download, as opposed to the "unlimited" of a few years ago that had FUPs and the like of 100GB or less.

All the major producers are also pushing hard to sell content-heavy services, witness Sky and BT Sport, Cloud storage and services and so on.

BT:- 1 x ADSLx 10GB, 2 x ADSLx unlimited, 1 x FTTC 20GB, 2 x FTTC unlimited.
Sky:- 1 x ADSLx 2GB, 1 X ADSLx unlimited, 2 x FTTC unlimited.
TalkTalk:- 3 x ADSLx unlimited, 3 x FTTC unlimited.
Plusnet:- 1 x ADSLx unlimited, 2 x FTTC unlimited.

Others that spring immediately to mind:- Zen, vivaciti, aquiss. Perhaps xilo and Freeola.

Contrary to there being a lack of unlimited products these days, there are many. Three years ago there were very few. I wonder if any have yet started budgeting at over 1kB per customer?

All I was doing was trying to imagine a scenario in which 500:10 was correct where 50:1 wasn't . As you say in your post after the one I'm replying to, and I've already said, a ratio is a ratio. It ends in 1, and if it the figures come out at 7:5 it is shown as 1.4:1 .

Given the identity of the person who avers such figures are used, I tend to believe him. What I suggested was where I thought he may encounter it, but it was just a guess. It is certainly in some arcane environment.

My logic is 50:1 is the same as 500:10
There is equal likelihood in both cases
50:1 is a 2% chance

500:10 is still a 2% chance

Similar 5000:100 is still the same probability.

It's the same as 1/4 is also 2/8 is also 4/16 is also 25/100. They're all the same.

So in summary with my logic I believe your view on this That said I do appreciate what you have to say as a general rule.
Just my two cents. & whoever said we are all BT fanboys made me laugh.

in network design maybe it is quoted as he said.

But I think the reason the lowest value is used is to give the provider some flexibility.

As things do work better when larger shared pipes are used even with the same contention ratio, so the provider I mentioned with the shared gbit pipes may in future change them to 10gbit pipes and stick 1000 customers on instead of 100. If they were quoting 100:10 ratio's to customers tho that would mean they would need to change what they selling whilst quoting a simple 10:1 they dont, they just make the network switch.

Edited by Chrysalis (Sat 19-Jul-14 15:25:21)

In reply to a post by RobertoS:

Given the identity of the person who avers such figures are used, I tend to believe him. What I suggested was where I thought he may encounter it, but it was just a guess. It is certainly in some arcane environment.

Purely as a ratio it is the same thing but as an implementation it definitely isn't. 50x1Mb/s users on 1Mb/s backhaul will not experience the same service level as 500x1Mb/s users on 10Mb/s backhaul.

What I don't know (and didn't say anything about) is if/when anyone chooses to quote the implementation figures rather than simply giving the ratio. If we assume that no sensible network designer would ever go with a genuine ':1' ratio then the difference does become rather moot.

This does make good sense. Very good way to explain it.

Purely as a ratio it is the same thing but as an implementation it definitely isn't. 50x1Mb/s users on 1Mb/s backhaul will not experience the same service level as 500x1Mb/s users on 10Mb/s bac

Yep it's a very different situation. That being said I haven't seen ISPs using these kind of ratios when selling broadband for a long time now so perhaps it's not that important to the end user nowadays to concern themselves with the logic.

I think we are agreed that the first line of the OP, which is where this started, is drivel by the sales/support person who said it. I wouldn't be surprised if it isn't still in the scripts .

In reply to a post by Andrue:

Purely as a ratio it is the same thing but as an implementation it definitely isn't. 50x1Mb/s users on 1Mb/s backhaul will not experience the same service level as 500x1Mb/s users on 10Mb/s backhaul.

What I don't know (and didn't say anything about) is if/when anyone chooses to quote the implementation figures rather than simply giving the ratio. If we assume that no sensible network designer would ever go with a genuine ':1' ratio then the difference does become rather moot.

Capacity planning doesn't work on ratios in my experience it works on expected peak utilisation per customer.

In reply to a post by ukhardy07:

My logic is 50:1 is the same as 500:10
There is equal likelihood in both cases
50:1 is a 2% chance

500:10 is still a 2% chance

Similar 5000:100 is still the same probability.

Not actually true. Statistical contention means it's less likely that 10 users out of 500 are maxing out their connections than 1 user out of 50.

Virgin Media are a case in point. They allocate tons of bandwidth to each customer compared with many but because it takes so few customers saturating their bandwidth to cause issues they are way more prone to issues than LLU operators or whomever.

This puts it beautifully.

But isn't the difference between fixed speed and rate adaptive being forgotten in parts of this discussion? (As I think I've mentioned before, unless I scrapped it at the review stage).

In reply to a post by RobertoS:

But isn't the difference between fixed speed and rate adaptive being forgotten in parts of this discussion? (As I think I've mentioned before, unless I scrapped it at the review stage).

No idea. Was just answering that one specific point about how, say, 500Mb of capacity sold on a 10Mb pipe is preferably to 50Mb sold on a 1Mb pipe.

Rate adaption is why, amongst other reasons, as I mentioned in a different post capacity planning is done in kbps per customer at peak utilisation time rather than based around contention ratios.

In reply to a post by Ignitionnet:

Rate adaption is why, amongst other reasons, as I mentioned in a different post capacity planning is done in kbps per customer at peak utilisation time rather than based around contention ratios.

Quite . That's the whole point of the thread, as opposed to the off-topic bit.

It's amazing what a small movement positioning it can make, but I've noticed that with video senders, etc before at those SHF frequencies.

Not really amazing. At 2.4gHz you are looking at a wavelength 12.4cm. Imagine a sinewave in front of you with a full cycle every 12.4cm. Apart from the amplitude, there are two zero signal points in that short distance.

Picking up on the wavelength aspect in Professor973's posting-
"Not really amazing. At 2.4gHz you are looking at a wavelength 12.4cm.";
and you mentioning that the USB dongle was attached to a shelf. it may be that you had placed other items on the shelf; or in the transmission path, which caused such attenuations.

This would particularly be the case if such objects were metallic; or contained water.

Water absorbs RF emissions particularly at 2.4 GHz, hence that band, shared with WiFi, is allocated for the magnetrons in microwave cookers.

From Wikipedia

https://en.wikipedia.org/wiki/Microwave
"
Heating and power application
A microwave oven passes (non-ionizing) microwave radiation (at a frequency near 2.45 GHz) through food, causing dielectric heating primarily by absorption of the energy in water.
"

In reply to a post by professor973:

Imagine a sinewave in front of you with a full cycle every 12.4cm. Apart from the amplitude, there are two zero signal points in that short distance.

Ermm... no.

Only at an instant of time (ie a snapshot of the e-m radiation) or if you've got obstructions causing a standing wave pattern to occur.

The instantaneous field strength at any given point varies sinusoidally with time and the measured field strength at that point will be constant.

Edited by billford (Sun 20-Jul-14 08:46:09)

I was not intending to get into the electronic and magnetic components of RF. just trying to explain in simple terms the small wavelength and the effect of moving a small distance on signal. Possibly I am too used to drumming y(t) = A\sin(2 \pi f t + \varphi) = A\sin(\omega t + \varphi) into my RAE students!

Edited by professor973 (Sun 20-Jul-14 12:04:56)

In reply to a post by professor973:

Possibly I am too used to drumming y(t) = A\sin(2 \pi f t + \varphi) = A\sin(\omega t + \varphi) into my RAE students!

I used to find your fantasy that you somehow are a lecturer with students mildly amusing, but as the years have passed it is becoming tedious.

Please yourself you pathetic [censored] . I am equally [censored] off with you calling me a liar. How about you check with the RSGB. Why do I have to prove anything to an anorak like you, so you go off to qrz.com and check my call. You will need to register on the site. You can then look up Steve M1ACB, a FDARS club member who will confirm the students I put through the club. My late wife M0CEQ was one, but she cannot say a lot now. So off you go, take a look, then shut the [censored] up.
Go take a look sonny Jim. I have never hid from anyone. http://www.qrz.com/db/M0AUR

Edited by professor973 (Sun 20-Jul-14 23:51:53)

In reply to a post by professor973:

How about you check with the RSGB.

I checked:

In reference to rsgb.org/main/internet-guidelines/:

The following message contents fall outside the ethos of the Society and would be unacceptable:

Comments that are considered likely to disrupt, provoke, attack, impersonate or offend others. For the avoidance of doubt this includes comments that contain swear words or language that might offend, or content that is racist, sexist, sexually explicit or abusive.

Edited by deleted (Sun 20-Jul-14 23:49:52)

[censored]

Morning Bill

Regarding Standing Waves, I observed an Audio set about 1980, in a school with long corridors.

A glass had been broken on a Fire Emergency Push Switch in a major extension.

No actual fire!

The Fire Brigade made a temporary repair; and I was replacing that with a proper glass etc.


In doing so, the Alarm was started up again etc, so I had to make my way back to the Control Panel in the main building, about 300 yards all told.

The Alarms were of a constant almost sinusoidal frequency, rather than a wailing, variable frequency.

As I walked along the main corridor, I noted that there were several "dead spots" where the Alarms could hardly be heard on a quiet Sunday morning, whilst further along the volume was ear-piercing and almost overwhelming.

---------

Many years earlier, I had noted a similar effect in a factory. It was a typical, modern, large almost open-plan factory, with simple partition walled offices around the sides, no ceilings to those offices.

I was seated where I could see out of the door; and I realised that the staff in the main area, were trooping fairly fast towards the exit.

We vacated the office; but had to walk a few paces before we could hear the Alarm.

Another person working in another of the offices, confirmed that the alarm could not be heard in that one either.

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

So Standing Waves of any sort can be gye-queer things!