Afrihost: Contention ratios fluctuate and are impossible to manage or declare

[Willie Trombone]

I've been trying to get details on contention ratios for the various uncapped ISP products, but I was told by Afriman today that it's an impossible thing to figure out, see below for my conversation (I had been told differently by Cybersmart support a couple of days ago)

Good morning Afriman, can you let us know what Afrihost's uncapped products contention ratios are? Are they static or do they fluctuate? Thank you!

I don't see how any ISP can maintain static contention ratios - the nature of contention is that it can't be static

We don't really work with these kind of stats, becuase they are essentially different from second to second and don't really add any meaningful input to managing the network (in our opinion)

Wow... that's the first time I've heard that said. I was told by Cybersmart that their contention ratios are 15:1 on their home uncapped and 5:1 on business uncapped. Is there a top end that Afrihost commit to? So your business uncapped accounts have the same contention ration as the home uncapped accounts?

What I mean is that how can we guarantee how many users will be connected at any point in time and how much bandwidth they demand at any point in time? We'd rather avoid such claims - becuase it's actually pretty difficult to substantiate your actual contention ratio even at one specific point in time. And then that figure would be meaningless 5 minutes later.

We prefer to just avoid the contention ratio stats altogether as we don't believe they are truly helpful to clients.

I totally disagree with the final statement. I'd love to see what my contention ratio is at any point that I'm experiencing speed issues - it's just one factor that could shed light...
...in addition, how can ISP's have lower contention ratios for different products if it's an immesurable thing? Perhaps it's impossible to guarantee contention ratio, but is it not something they could at least show us by logging in to the control panel perhaps? Also, is contention ratio relative to your DSLAM or exchange?

 

[supersunbird]

I don't think they properly understand what's contention ratio is.

Its how many users you have divided by your allocation of bandwidth to that group of users (hope I am correct lol).

Edit: Say you have 100 1mbps user accounts, but you only have a 10mbps capacity to provide the service to them, it means your contention ratio is 10:1. That stays static and doesn't fluctuate (unless you sign up more accounts and don't provision new capacity for them)

 

[Willie Trombone]

Either way, it should give users an indication of whether an ISP is oversubscribed or not, and I certainly don't want to sign up with an oversubscribed ISP... perhaps THAT'S the problem, not that it's impossible to fathom.

 

[Hush9300]

If you want fixed contention ratios sign up for a leased line...

 

[Willie Trombone]

If you want fixed contention ratios sign up for a leased line...

I think we all know that's not going to happen
So you agree with Afriman that it's pointless to declare contention ratios at any point in time (like on a ticker somewhere)? And I see Afriman didn't answer the question about business uncapped users having a lower contention ratio than home uncapped users... Can we assume that they're the same? If not, how come they are different (it sounds like Afriman is saying that everyone is in the same pool). If they are different, is that accidental or intentional?

 

[Hush9300]

I think we all know that's not going to happen
So you agree with Afriman that it's pointless to declare contention ratios at any point in time (like on a ticker somewhere)? And I see Afriman didn't answer the question about business uncapped users having a lower contention ratio than home uncapped users... Can we assume that they're the same? If not, how come they are different (it sounds like Afriman is saying that everyone is in the same pool). If they are different, is that accidental or intentional?

Everyone under a specific account type (Home Uncapped, Business Uncapped, Capped) is in the assigned bandwidth pool...

Look at it this way.

1) 50 subscribers on 4Mbps lines using a 40Mbps pipe. Contention ratio is 5:1

2) 100 subscribers on 4Mbps lines using a 80Mbps pipe. Contention ratio is 5:1

3) 200 subscribers on 4Mbps lines using a 160Mbps pipe. Contention ratio is 5:1

In option 1 it would take 10 subscribers maxing out their lines for congestion to kick in, in option 2 - 20 subscribers and option 3 - 40 subscribers... What happens to the rest of the subscribers?

So while contention ratios are fixed, service quality is still highly dependent on the amount of users contending for the fixed amount of bandwidth at any given time...

I think you are under the impression that a contention ratio of 5:1 means that there is only 5 subscribers contending for the bandwidth. This is only true for leased lines as far as I know.

 

[Willie Trombone]

Everyone under a specific account type (Home Uncapped, Business Uncapped, Capped) is in the assigned bandwidth pool...

Look at it this way.

1) 50 subscribers on 4Mbps lines using a 40Mbps pipe. Contention ratio is 5:1

2) 100 subscribers on 4Mbps lines using a 80Mbps pipe. Contention ratio is 5:1

3) 200 subscribers on 4Mbps lines using a 160Mbps pipe. Contention ratio is 5:1

In option 1 it would take 10 subscribers maxing out their lines for congestion to kick in, in option 2 - 20 subscribers and option 3 - 40 subscribers... What happens to the rest of the subscribers?

So while contention ratios are fixed, service quality is still highly dependent on the amount of users contending for the fixed amount of bandwidth at any given time...

I think you are under the impression that a contention ratio of 5:1 means that there is only 5 subscribers contending for the bandwidth. This is only true for leased lines as far as I know.

So it is possible to calculate and declare then? All I am interested in (and very interested in) are who the oversubscribed ISPs are... and who I should be buying my bandwidth from. Not too much to ask surely.

 

[Hush9300]

So it is possible to calculate and declare then? All I am interested in (and very interested in) are who the oversubscribed ISPs are... and who I should be buying my bandwidth from. Not too much to ask surely.

A contention ratio is not going to tell you who is oversubscribed as my example proves.

In each of the examples, even the one with the least amount of subscribers, it only takes a handful of those users to cause congestion theoretically speaking.

Contention ratios should be used as a means of network planning by the ISP's. It is irrelevant for you as a consumer because it's highly probable that there are many more people contending.

 

[bekdik]

Are there not 2 contentions?

One as per ISP and the other as per Dslam?

 

[Paul Hjul]

the "contention ratio" is very much a weakest point in the chain figure. IIRC Telkom is required to provide a 1:20 contention ratio (or better) on exchanges so with ISPs (including Telkom Internet) having a better contention ratio on their network components the explanation for exchange congestion is made

My guess is that the "weakest link" for Afrihost ADSL provisioning is exchanges followed by their IPConnect capacity. With 13Gbps (which I believe is what they've got) a 1:10 contention ratio will allow them to serve 130 000 odd customers with 1Mbps uncapped or 13 000 odd customers with 10Mbps uncapped and a huge number of figures in between ... Without proper insight I suspect that Afrihost's provisioning assumes about 1:12 odd contention ratio on IPConnect and a 1:20 odd contention ratio on international connectivity and that these figures will generally match other ISPs in the industry. However the problem of exchange congestion remains and there is a very sharp double edged sword at play: the IPConnect charge has to come down or offer more value (so upgrades) but the total revenue Telkom wholesale gets on ADSL operations really is the ADSL line rental and IPConnect which makes financing on upgrades a mishpot exercise. Now new entrants might well be able to make a decent job of ADSL provisioning but they need to pay for the copper between premises and their infrastructure - the so called Line Access Deficit. Some ISPs have presented cases that appear to wish for free access on a NakedDSL approach but this is nonsensicle - it means that LLU is necessary but wont bring down prices, it means that Telkom needs to get a lot more buy in to an ADSL ecosystem of find itself sitting with a big financial headache; it also means that at the moment there is a trade off between lower barriers to entry and less exchange congestion.

 

[Willie Trombone]

I think that explains some things in my head, but I'm baffled at Cybersmart's claim that their business product has a 5:1 contention ratio while their home uncapped is at 15:1. Does that make any difference at all if the weakest link is the 20:1 at the DSLAM (assuming it's nearing capacity)?

 

[Paul Hjul]

Well Telkom has many exchanges at much better contention ratios and business users on a 5:1 contention ratio where there is an MSAN will benefit. I think Cybersmart is using contention ratio figures as a marketing spin but it is something that can bring in customers.

 

[Hush9300]

I think that explains some things in my head, but I'm baffled at Cybersmart's claim that their business product has a 5:1 contention ratio while their home uncapped is at 15:1. Does that make any difference at all if the weakest link is the 20:1 at the DSLAM (assuming it's nearing capacity)?

It's a red herring and used purely for marketing purposes I guess.

They're entitled to do so but it doesn't make much difference if everybody on said packages is vying for the same bandwidth.

 

[Willie Trombone]

Openweb do it too...

Freedom has a higher contention ratio compared to other Capped products.

It is also a promotional account, thus it might not be available forever.

BUT, if you signup now, you will have the price locked in for life!

 

[madrynn]

I'd like to know both contention ratios, that of the "internet" pipe from the DSLAM at my local exchange, and that on the isp side.

I know it probably not as simple as reasoning that with a 1:5 contention ratio on a 1mb line = 20kbs per user at worst case, but it would give a good reference point for customers to rate the service on and realize what they are paying for (apart from the shaping policies).

The only reason I can think of for not releasing the contention details and claiming that its not fixed or does not matter is that isp's (and Telkom) sell accounts (and lines) without having to upgrade anything until the internet breaks and people complain.

Kinda like milking the cow till it nearly drops before feeding it, so to speak... makes for a sick cow and crap milk... but at least it's "cheap".