Contention ratios...

DeVore

Ok, I have an ulterior motive for asking this question which I'll explain over the next few days.

my question is this: Contention ratios on RADSL... I've seen 48:1 touted around...

Am I correct in saying this is "upstream bandwidth contention" ie: for every 512k they have to the internet proper there are 48 people trying to leach connectivity from that?

ie: if everyone was hammering it they would each get 10.6kbps down? or in real terms a dowload speed of 1.3 kiloBYTE per second.

Now ok, I know that 48 people all d/ling at full whack would be hard to get but I'm more checking that my understanding of the situation is correct...

Someone, anyone, (Muck!) tell me I'm wrong. Tell me thats not how it works.

Also, who is responsible for this contention ratio? VIA ? or is it force on them somehow by Eircom?

DeV.

SkepticOne

If a service is fully contended, then that is indeed how it works. Eircom's wholesale product description uses the term 'planning ratio' and the figure of 48:1 is opposite the RADSL bistream service. I've always taken this to be the contention ratio, but there was a thread about a week ago suggesting that an ISP might be able to supply extra bandwidth.

DeVore

My understanding of the wholesale product is that the ISP can provide their own connectivity to the internet. I kinda presumed that that is what VIA are doing. Neh?

With Netsource RADSL ... is the 48:1 ratio under VIA's control or Eircoms.


<opinion> I think 48:1 is criminal but I only realised recently what they/it meant... </opinion>

DeV.

spongebob

Originally posted by DeVore

ie: if everyone was hammering it they would each get 10.6kbps down? or in real terms a dowload speed of 1.3 kiloBYTE per second.

Also, who is responsible for this contention ratio? VIA ? or is it force on them somehow by Eircom?

DeV.

I do believe that I posted the self same figgers meself recently.

Eircom control the product and therefore the contention ratio, Sceptic and I and some others had a long yatter about 'how' in a thread on IOL Broadband starting about friday last.

M

Sloth

Via tried numerous times to blame my connection problems on contention at 24:1 so I can't imagine what they'd say about 48:1. I can't say I fully understand how contention works as Nildram, one of the best isps in england has 50:1 contention and still seems to offer an incredibly good service. People I know on the service have never complained about contention affecting their speeds at all.

spongebob

Originally posted by Sloth
I can't say I fully understand how contention works as Nildram, one of the best isps in england has 50:1 contention

A shedload of transparent caches in telehouse.

Sloth

Surely contention can't be that much of an issue if Nildram have such a high one. Nildram 512k users can also go over the 512 speed, I know one who almost seems to be at just below 1mb speeds even though hes on the 512 package and has pings to servers like jolt of 7ms.

MadsL

A shedload of transparent caches in telehouse.

Err... a tad unshaven there Muck ... can you translate? Is this about Squid?

disco_rob_funk

I doubt somehow that you simply divide 512k by 48; I'm sure there bandwidth at whatever communal connection point said 48 users share is way beyond that.

For feck's sake, with 10 or 15 neighbours giving it socks you're back in 56k territory; I doubt any reasonably sane telco would plough money into such a technology for such bad service.

I guess only time, and more subscribers, will tell...

STaN

Its an oversubscription. 47 other people don't share YOUR line.

Via have at least a 155Mbits per second connection to each exchange they offer service from (or buy capacity on eircoms)

its based on the statistical evidence that it is almost impossible to get every1 downloading at the same time. If you look at the ordinary users, usage graph, it will be a load of peaks and troughs.

If VIA have a 50Mb connection into an exchange they will sell connections totalling 2.4Gbps which would be ~9400 256k users for example.

The only problems that VIA will probably face in the future is P2P programs cloggin up the network as has happened to many ISPs around the world who are now scrambeling to do something to tackle them. Many ISPs in the states run 80 1mb customers off a 2Mb connection and no one experiences any drop in preformance

Dustaz

one thing i would like to know about contention is this. Where does the actual contention take place?

My understanding is as follows (so please please correct me if im wrong):

I have an uncontended 512 line to the DSLAM in my exchange. So do the other 48 people on my port in the dslam. Its only once it is routed with the other ports in the dslam that the connection becomes contended. Therefore, if eircom (or via or whoever) have 155mb going out of that dslam and they only have, say 60 subscribers in that exchange, there is no problem. Its only when you get VERY busy exchanges that a problem occurs.


If that is correct (and even if its not) and still leads to questions about the contention pool. Has there been any definite answer to that?


(As a request, can we keep this thread as non-tech and 'lay-terms' as possible? the other thread was highly interesting, but im guessing that a lot of the important stuff went over a lot of peoples heads - i know i was looking up a lot of it )

STaN

one thing i would like to know about contention is this. Where does the actual contention take place?

What happens when network operators sell broadband is that it's just like selling airline seats: when you sell somebody, say, half a megabit per second of
bandwidth on their cable modem across your network, you will sell that same half megabit of bandwidth to numerous other people. So if you sell it to 50 people, there is a contention ratio of 50 to 1. Which means that if all 50 people try to use the service at the same time, they will not get half a megabit of bandwidth. Instead, they will each get 50 kilobits per second--in other words, the same amount of bandwidth as they'd get through a modem. So that's the vicious circle with broadband: the more successful it is, the more the service degrades. So, in order to get the same revenue but not upset the customers, the cable companies are going to have to put in more infrastructure, in order to get the contention ratio back to something that's acceptable. Also, when somebody starts on broadband, they just use it for their Internet connection. Fine, so anything that is faster that 56 kilobits per second is a revelation to them. But when they start to realize they can download video--and of course they are eventually going to download VOD--they are not going to be using a little bit more than 56 kilobits per second, they are going to be using the whole half a megabit per second. If 2 of them try to use half a megabit per second for their video, one of them is not going to see something very good. In fact, both of them are not going to see something very good. That's why this contention ratio thing is something that is waiting there in the wings to really catch people out.

It happens on the larger scale though. Whe eircom or whoever say its 48:1, i believe that when they reach the limit of the connection to their core network that the contention will start coming into play... i.e. the oversubscription. They will oversell 48times what is there. This is how they get their money back for charging a low fee for higher bandwidth. Otherwise they would just sell leased lines.

flamegrill

AFAIR Eircom/VIA/Esat would have 2MBit/s ports on each DSLAM.
Now Even though 2 Mbit/s doesn't sound like much, its a hell of a lot better than 512kbit/s on each DSLAM.

So as stan says, its only when the ISPs grossly over subscribe that contention will be come a problem. For the time being it wont be IMO, even if the smelly students down the road leech all day

Paul

Son of Blam

Originally posted by Sloth
Via tried numerous times to blame my connection problems on contention at 24:1

What connection problems are you having?

echomadman

So as stan says, its only when the ISPs grossly over subscribe that contention will be come a problem. For the time being it wont be IMO, even if the smelly students down the road leech all day

Heh, thats where AUPs will actually come in handy, as long as they're implemented logically.

spongebob

How is the contention divvied up on the upstream ...?

128k upstream / 48 users is about 2.6Kbit each. that means 0.33 KByte upload speed , if some poor eejit wants to d/l that 5Mb MP3 that you feel you should share out ..........then

Every 3 secs you upload 1k

Every 3000 secs you upload 1Mb

I make it a tad over 4 hours for someone to download one 5Mb mp3 file from your P2P app ...... humm. The same problem would occur if you were runing an FTP server or if you kludged the port using dyndns or similar.

I have heard elsewhere that its only the downstream thats contented but my reading of the interconnect principles does not clarify the sitiuation.

M

Capt'n Midnight

[Edited]
(So neglecting splitters and analog methods of putting two calls on the same copper - each subscriber has own copper going to exchange.)

[the unlikely one]
So either there is a box in the exchange that can take 50 pairs of copper (ie. hardwired 50:1 ratio - and just hope you are not sharing with a leech - but FTP should be fast between youze - if you are lucky and are the only subscriber on the box - happy days...)

[Likely]
Or each signal is digitised separately - in which case 50:1 is ratio shared across the whole exchange (remember 100Mb/ 155Mb is what is likely to be used for data)


Anyone know which it is likely to be ?


Not to worried myself
a/ zero chance of ADSL in Lucan South
b/ instead of sharing 2/0.512Mb with 50 others - am sharing an 11Mb link into the WAN - which has several uncapped low-contention BB links for the uncached stuff...

SkepticOne

Originally posted by Capt'n Midnight
So either there is a box in the exchange that can take 50 pairs of copper (ie. hardwired 50:1 ratio - and just hope you are not sharing with a leech - but FTP should be fast between youze - if you are lucky and are the only subscriber on the box - happy days...)

I've never heard of it done this way (where users are separated into blocks of 50 or whatever).

MarVeL

Just checking Midnight but where in Lucan are you? I'm down by Liffey Valley and have been told by 3 separate companies that the exchange is ready to go and just awaiting my signature and large gobs of cash.

(The phone call from eircom where they said the reason to go with them was that they were regulated was particularily fun!)

Capt'n Midnight

The other end of Lucan - near Adamstown
The nangor road has been dug up now on and off for the few years - still no sign of any BB

BTW:
I think Eircom mean "Regulated" in the engineering sense of limiting maximum flow...

MarVeL

Bummer. Hopefully NTL will be expanding out that way soonish.

On the regulation thing the sales person particularily mentioned comreg so I don't think so. They also pointed out that you don't own the modem Esat give you (although they do at least give you one)

Anyway way off topic, sorry

Martin-UTVi

Contention ratios

Ok, there are really two different contention ratios here. The more publicly stated 24:1/48:1 generally refers to the contention on the bandwidth backhauled from the user, through Eircom's DSL network and handed to the ISP. BT tend to use a 20:1 and a 50:1 ratio (SME and residential respectively). Now obviously if you do the sums, 50:1 fully loaded means you get 1.3kbytes a second. But because of the way the internet works and peoples surfing habits, this just doesn't happen. Don't forget everything you do on the internet is contended, from the sites you access to the links you use to get to those sites. Just because you have a 512kbps connection at home does not give you that amount of connectivity everywhere you go on the internet. But in general terms, the net is engineered for over-capacity and hence your access speeds should reflect your connectivity speed.

Now once the DSL traffic is handed over to the ISP, it is up to them to then carry that traffic over their network and pass it over their external IP links to then reach the "Internet". Generally ISP's use QoS on their routers to ensure that the same contention ratios used in the backhaul are applied to their external bandwidth......but again this is at the ISP's discretion. They could have no contention ratio on their DSL bandwidth, or they could have a higher one......hope this all helps....

flav0rflav

As Martin nicely explains, the backhaul from the DSLAMS( exchanges), to the ISP is the first link for contention. Eircom quote 48:1 for the radsl product. This all goes through their ATM network (fancy little packets over fiber). The handover point is the next crucial point. For the bog standard radsl, eircom suggest a 2 meg serial connection from eircom to the ISP for upto 192 users, which is also 48:1. Then it's on into the ISPs networks. With a little measuring you can figure out the speed of their links (google: bing + bandwidth). Figuring out the number of users is more difficult.

Thoughts:

The handover point has users gathered from all around the country. I think this will be the location that gives trouble first, as the DSLAMs are more evenly distributed.

The ISPs have the _option_ to connect to each individual exchange, with an optical (>45M) link. They also have an _option_ to have a single optical(>45M) handover link. Do you think they'll do that?

Internal capacity of eircom is big enough to give us loads of bandwidth without any 'upgrading'. They have min 155 meg optical links running between the exchanges, no?

As regards direction, all the links except the adsl lines are symmetric full duplex (most likely) so the contention upstream would be better? 12:1 (512/128 = 4).

ps. To setup your own radsl isp:
1) pay 8000 euro for 'training' on how to use eircoms web based line ordering system.
2) Pay Colt/Cable&Wireless/? X amount for a 2 meg link to the internet.
3) Connect internet link to eircom handover point link. Pay eircom 150 euro for each customer install, and 27 euro per customer per month.

Martin-UTVi

3) Connect internet link to eircom handover point link. Pay eircom 150 euro for each customer install, and 27 euro per customer per month.

Also, don't forget to pay Eircom for the 2meg/45meg connectivity.....

SkepticOne

If I understand this correctly, even if bandwidht to the ISP were free (obviously not the case), Eircom would still impose 48:1 ratios since they controll access into the exchanges and the DSLAMs. The ISP does not have the option of engaging a different telco and connecting directly to the exchanges in which Eircom have DSLAMs. Eircom are stifling competition in this regard.

spongebob

Originally posted by flav0rflav


Thoughts:

The handover point has users gathered from all around the country. I think this will be the location that gives trouble first, as the DSLAMs are more evenly distributed.


There are 11 or so reagional handover points (3 in dublin and another 8)


The ISPs have the _option_ to connect to each individual exchange, with an optical (>45M) link. They also have an _option_ to have a single optical(>45M) handover link. Do you think they'll do that?


Its mandatory to take a 45Mb or higher backhaul if you take the ADSL product, RADSL is 2Mb per region .


Internal capacity of eircom is big enough to give us loads of bandwidth without any 'upgrading'. They have min 155 meg optical links running between the exchanges, no?


Of course, Eircom still like to whinge at Comreg that every new service requires them to bury and light another STM1 to every region.......twaddle.


As regards direction, all the links except the adsl lines are symmetric full duplex (most likely) so the contention upstream would be better? 12:1 (512/128 = 4).


the 45Mb and above are symettric, I am not sure about the 2Mb


ps. To setup your own radsl isp:
1) pay 8000 euro for 'training' on how to use eircoms web based line ordering system.
2) Pay Colt/Cable&Wireless/? X amount for a 2 meg link to the internet.
3) Connect internet link to eircom handover point link. Pay eircom 150 euro for each customer install, and 27 euro per customer per month.

Have you seen the schedule of rack space charges (ventilated and unventilated room) and the cost of the COW per houe as he stands there looking at ya.

M

Martin-UTVi

The ISP does not have the option of engaging a different telco and connecting directly to the exchanges in which Eircom have DSLAMs

Not necessarily true. An ISP/Telco could roll out their own DSL network in Eircom's exchanges around the country offering a different set of service levels.....but it would be hellishly expensive (I think Esat tried this....). At the end of the day, someone somewhere has to pay for the connectivity, DSLAM equipment, ATM network, IP backhaul etc. And I reckon if Eircom tried to cover their cost based on a 1:1 or 10:1 ratio, it would put the price of DSL up.

I don't think what we're discussing in this (and associated) thread should shock or surprise anyone. It really is the real world of broadband connectivity. I've never discussed my NTL cable modem contention with them (in apartment where I don't have BT line so can't go with UTVi :mad: ), or even looked to see what it is......because when I do any downloading it *generally* comes through at 35k+ a second. Now if I start to insist on a certain QoS etc., I certainly don't expect to be paying the same price....Contention is a fact of life on the internet and applies to everything, but due to the nature of peoples usage and bandwidth utilisation (e.g. reading boards.ie or responding here means I am not maxing my 100mbit full duplex network connection....) it doesn't matter than much. I know some people will argue that they do a lot of downloading....but believe me, you are in the minority. Most peoples net usage does not saturate their connectivity 24/7.

Capt'n Midnight

ps. To setup your own radsl isp:
1) pay 8000 euro for 'training' on how to use eircoms web based line ordering system.
2) Pay Colt/Cable&Wireless/? X amount for a 2 meg link to the internet.
3) Connect internet link to eircom handover point link. Pay eircom 150 euro for each customer install, and 27 euro per customer per month.

So suppose you want to setup an ISP for 10 clients..

So eircom would want 150 for the install and 324 rental for each user - ie. a cost of 374 for the first year - that would easily cover a wireless install.
And they want 8000 up front ("hello money" ?) - that would well cover a basic wireless station http://www.vbnets.com/tutorials/startawisp.php

AND you would have to pay for the link to the handover point.

AND then you have to pay for the bandwidth too..

BUT - hang on a mo.. you would enough change from the 8000 to pay for a year of LEAP at 4:1 (which for 10 clients works out at 40:1) http://www.leap.ie/


Note: If you want to go commercial there are license implications and costs.

SkepticOne

Originally posted by Martin-UTVi
Not necessarily true. An ISP/Telco could roll out their own DSL network in Eircom's exchanges around the country offering a different set of service levels.....but it would be hellishly expensive (I think Esat tried this....). At the end of the day, someone somewhere has to pay for the connectivity, DSLAM equipment, ATM network, IP backhaul etc. And I reckon if Eircom tried to cover their cost based on a 1:1 or 10:1 ratio, it would put the price of DSL up.

Yes, but measures like the fibre rings project will have fibre running up against Eircom's exchanges containing DSLAMs. These rings will link up with competing regional fibre owned by the ESB, etc. All this subsidised fibre will be wasted because Eircom will insist that the access seeker must connect at specific points and use its backhaul facilities bypassing whatever may already be there.

flav0rflav

Originally posted by Muck

There are 11 or so reagional handover points (3 in dublin and another 8)

Its mandatory to take a 45Mb or higher backhaul if you take the ADSL product, RADSL is 2Mb per region .

Have you seen the schedule of rack space charges (ventilated and unventilated room) and the cost of the COW per houe as he stands there looking at ya.

M

The docs say that for radsl, you only need one single handover point, at 2M per 192 users.

The costs for installing equipment in eircom's exchanges are certainly high. I couldn't find info from BT as a comparison. Did you know that is the US properties values around the incumbent telco exchanges increased significantly. You only need to get that serial link out of the building.

The contention doesn't bother me, it's the fact that we pay more than most other Euro countries, for less options.

BT wholesale prices
512k, 50:1 - e18
1024k, 50:1 - e25
1024k, 20:1 - e40
2048k, 20:1 - e53

eircom wholesale prices
512k, 48:1 - e27
512k, 24:1 - e55
1024k, 24:1 - e89

BT mentioned has one of the most expensive in europe, leading to poor uptake of DSL in UK.

spongebob

Originally posted by SkepticOne
Yes, but measures like the fibre rings project will have fibre running up against Eircom's exchanges containing DSLAMs. These rings will link up with competing regional fibre owned by the ESB, etc. All this subsidised fibre will be wasted because Eircom will insist that the access seeker must connect at specific points and use its backhaul facilities bypassing whatever may already be there.

No. ESAT rolled out their own fibre, subsidised by the Government to the tune of IEP10m or so . They have fibre into each Eircom regional pop .....which is where the initial wholesale breakout is done.....except for one I think, Priory Park in Dublin. 10 out of 11 so. There was a delay in Portlaoise at some point too.

Therefore they have no need for the ATM slab of backhaul and would simply need a virtual 2Mb pipe in the Regional POP to which Eircom presents 'up to 192' Virtual RADSL ports of 512k .

They dont need a real 2Mb pipe to Dublin. The real 2Mb pipe is already in the building. Of course the rel 2Mb pipe hadnt been installed with teh intention of accepting sS7 signalling, it was in there as backhaul for LLU copper that had been concentrated at a DSLAM belonging to ESAT themselves....which is also still in that building.

M

M