21CN - 24 or 20Mbps

Ardua · Aug 30, 2011, 11:03:35

Why do some ISPs offer a 20Mbps service on a 21CN connection and others a 24Mbps service? The various number speed checkers come up with the same result.

Gary · Aug 30, 2011, 11:06:36

No idea, although there is a push to make ISP's state the speed in more realistic terms, 20Mbps is far more realistic than 24 I would imagine over 21CN.

zappaDPJ · Aug 30, 2011, 11:44:04

I'd actually be very surprised if 20Mbps was realist for the majority of connections. Statistics I've seen in the past suggest there are very few getting above 14Mbps with average user attaining no more than 8Mbps. That was a while ago so things might have improved but not by very much I'd think.

Ardua · Aug 30, 2011, 12:34:22

My question was more general. I just wonder why there is a discrepancy in the advertising for what would appear to be an identical 21CN service? I am pretty sure that what comes out of the line is the same. Or put it another way, if I move from IDNet (24Mbps) where I get a connection rate of 17.4Mbps will my connection rate fall on, say, a Zen (20Mbps) service? The IDNet and Zen speed checkers give an identical range of results.

arobertson676 · Aug 30, 2011, 12:39:14

All the services that ISPs offer can technically support 24Mbps. But providers providing up to 20Mb/s second cap it. If you synced at 20Mbps and you upgraded to a 24Mb/s service you would achieve 24Mb/s,

Niall · Aug 30, 2011, 14:54:57

Oddly, when the BT engineer phoned me yesterday morning, he actually referred to 21cn as a 20mb service.

pctech · Aug 30, 2011, 15:50:18

Theoretical max for ADSL2+ is 24 Meg but you'd never get that speed.

Niall · Aug 30, 2011, 15:56:31

If BT themselves refer to it as a 20mb service, it suggests it never could!

pctech · Aug 30, 2011, 16:02:47

24 Meg would require no ATM or TCP/IP header, error correction or control bits which is not possible.

Ardua · Aug 30, 2011, 16:06:19

Quote from: Niall on Aug 30, 2011, 15:56:31
If BT themselves refer to it as a 20mb service, it suggests it never could!

Now I am confused. If I have learnt anything from my time on this forum, the max IP is 88.2% of the connection speed. So theoretically, the max IP on a 24Mbps service is 21.2Mbps and 17.64 Mbps on a 24Mbps service. However, if a particular line cannot support either of those 2 IPs, is the difference between 24 and 20 just an academic point.

Niall · Aug 30, 2011, 16:08:05

Honestly, I've had my head battered with ADSL info over the last month, so I'm the last person to ask about anything. I'm just parroting what the engineer said.

I shall now run away, crying, from this thread

Lance · Aug 30, 2011, 16:14:00

Its an academic point as it's unlikely you'll get either 20mb or 24mb unless you live next door to the exchange.

My assumption is that any 20mb service is simply a capped 24mb adsl2+ line as that will be the underlying BT wholesale product.

Ardua · Aug 30, 2011, 16:27:06

Quote from: Lance on Aug 30, 2011, 16:14:00
Its an academic point as it's unlikely you'll get either 20mb or 24mb unless you live next door to the exchange.

My assumption is that any 20mb service is simply a capped 24mb adsl2+ line as that will be the underlying BT wholesale product.

I will cut to the chase. I am thinking of moving away from IDNet - either now or when FTTC arrives in my area in 3 months time. I have a short list of 3 ISPs which offer packages - both ADSL2+ and FTTC - which would suit my usage. However, one of the ISPs only offers a 20Mbps ADSL2+ service but has a well-regarded technical support department, and I just want to make sure that I will not get a 16% reduction in my current connection speed if I was to move to them. I suspect not as my present connection rate is only 17.5Mbps.

Edit:

An interesting FAQ which provides the answer to my original question. I will comment no further.

http://www.zen.co.uk/enterprise/broadband/enterprise-broadband/up-to-20mbps-broadband-faqs.aspx

pctech · Aug 30, 2011, 16:34:18

No you won't get a reduction if your sync rate stays as is.

Steve · Aug 30, 2011, 18:52:08

Although profiles exist for greater than 20mbps in reality only a very small proportion would achieve anything greater than 20 so I think it may well be a marketing decision to advertise as upto 20Mbps and cap the maximum download at that level.

Ardua · Aug 30, 2011, 19:45:48

Quote from: Steve on Aug 30, 2011, 18:52:08
Although profiles exist for greater than 20mbps in reality only a very small proportion would achieve anything greater than 20 so I think it may well be a marketing decision to advertise as upto 20Mbps and cap the maximum download at that level.

That is not quite how Zen's FAQ reads Steve. There is no capping they are just lowering customer expectation based on ADSL2+ experience and OFCOM's push for more accuracy about expected speeds. It will be interesting to see if other ISPs follow suit.

pctech · Aug 30, 2011, 21:18:42

That's what they have said also in response to questions on their own forum (which is not half as lively as this one)

Better to under promise and over deliver.

Lance · Aug 30, 2011, 22:11:15

I'd still be surprised is the average is anything like 20mb. I would prefer all customers to advertise the package based on a ofcom determined average, along with the max speed for the package.

Simon_idnet · Aug 31, 2011, 04:36:36

The theoretical maximum sync speed of ADSL Max is 8Mbps (but you need to be close to the Exchange to achieve that).
The theoretical maximum sync speed of ADSL2+ is 24Mbps (you need to be VERY close to the Exchange to achieve that).

We took the view that it made sense to advertise both services using the same criteria and that the industry-standard advertising for ADSL Max has established that we should therefore use the modulation capability.

My own line at home syncs at 21Mbps. We've seen customer lines connecting at 24Mbps.

Niall · Aug 31, 2011, 13:40:46

Oddly, when I was on the upto 8mb service, I got 7.6, but now I'm on the 21cn I 'only' get 14mb. I thought it'd have been higher, but then again it's not straightforward ratio based is it, it's down to the quality of the line you're on.

pctech · Aug 31, 2011, 15:20:19

Quote from: Simon_idnet on Aug 31, 2011, 04:36:36

We've seen customer lines connecting at 24Mbps.

The customer lived on top of the exchange

.Griff. · Aug 31, 2011, 15:32:55

Be have a "24Mb" club on their forums and judging by the number of people (along with line stats to back it up) posting in there it makes me laugh when people purport the "myth" that you need to live next door to the exchange in order to achieve such sync speeds.

Granted there's plenty more, lots more infact, that don't achieve anywhere near those speeds but the whole "no-one gets those kind of speeds" is simply misleading.

Niall · Aug 31, 2011, 17:04:50

I've got a mate in London that whilst on Be, had 22mb. That was just before they started having problems though, then he moved out the area. Now he has an awful line, but a tasty missus

Ardua · Aug 31, 2011, 17:18:15

Having posed the question and seen Zen's and Simon-IDNet's answers, my connection is clearly trying to make its own point. Having had it disconnected for most of the day because of some ongoing domestic electrical work, on re-connection the CR has reached an all time high of 18Mbps: an increase of 700Kbps. This equates to a 10Mbps increase in 6 months of ADSL2+. I am about 1Km from my exchange and I have not touched a thing in 5 months. I will let you know when I pass 20Mbps

Simon · Aug 31, 2011, 17:54:57

We'll put the flags out.