Contention ratios [Archive]

beyers

30-11-2003, 03:48 PM

Can someone tell us more about contention ratios? How does it work. If the ratio is 50:1, does it mean all of us share the same 512K, for example. Then I will never get the full 512K in theory....?

What are good ratios on an international standard?

ProAsm

30-11-2003, 06:55 PM

Contention Ratio.
Lets use a 512k ADSL system for instance.

Basically the ideal Contention Ratio for any connection would be 1:1 or expressed as 512:1
This means that the Service Provider can guarentee you a 512k connection 24/7/365 but it would cost you a fortune, probably in the region of R27000 pm.

So ISP's utilize varing Contention Ratios with the average being 50:1 or expressed as 512:50 which is still excellent.
This means in ADSL terms, the DSLAM you are connected to at the exchange you will share with 50 other users.
Now if all 50 users are all downloading at the same time your download speed theoretically will drop to 512/50 = 10.24 kbits (1.28 KB/sec)

Now because the way data is transmitted on the Internet this is highly unlikely to happen.
For instance, Telkoms ADSL has a Contention Ratio of 512:40 (stand to correction here) which means the DSLAM you are connected to at the exchange holds 40 connections.
Now how many people in high density areas have ever had their ADSL drop to 1KB/sec as 40 connections there is easy to achieve.
Now although a 512:40 looks good and is according to world standards, they go and destroy that by adding a Cap - so at the end of the day you would have been better off with a 512:200 system for instance.
ISDN is in the region of 128:200 - has anyone ever complained there ?
This is where software monitors who are hoggers and who is not and spread things around a bit to even the playing field so to speak.

Basically at the end of the day, the higher the Contention Ration the cheaper the ISP can offer the system.

Why everyone is suddenly worring about Contention Ratio I dont know because at the end of the day all you want is a good and reliable connection, with good pings and decent downloads.
ISP's spend 1000's of Rands on Software to take care of this.

Some information I found and links to follow:

<blockquote id="quote">quote:<hr height="1" noshade id="quote">If the server has a 100kb connection to the net, and there is a connection of 1:1000 - and ALL 1000 sites have a page of 1kb on them, and 1000 different people from 1000 different ISP's all access a site at the exact same time, then 100% of the server bandwidth will be used.
If, however, 2000 people from 2000 different ISP's all access a site at the exact same time, then 200% of the bandwidth is used (which cant happen), so half the people are "given" the file, and then the other half are "given" the file.<hr height="1" noshade id="quote"></blockquote id="quote">
<blockquote id="quote">quote:<hr height="1" noshade id="quote">This describes the maximum number of users sharing the bandwidth on the connection between your local exchange and the Internet Service Provider.. A customer with a contention ratio of 20:1 never has to share this bandwidth with more than 19 other users<hr height="1" noshade id="quote"></blockquote id="quote">
<blockquote id="quote">quote:<hr height="1" noshade id="quote">Contention ratio is the term used to describe the situation whereby customers share capacity on a line or within a network. For example if everyone in Cork phoned someone in Dublin at the same time, not all calls would get through because there is only a limited number of circuits between Cork and Dublin. But the chances of this happening is extremely remote so the contention ratio used has little effect on the service to the customer. However if the number of circuits was further reduced people would begin to notice a reduction in the quality of service (i.e. more busy tones when they try to ring Dublin) so the balance is whats important here.
For IP traffic a contention ratio is even less of an issue (provided the ratio is not extemely high) because, unlike voice telephony, Internet traffic is 'bursty' in nature: when a customer is connected to the Internet they do not use 512kbps at all times. Browsing the web may only use a part of this bandwidth for a number of seconds then none at all until the customer loads the next page.
The 'contention ratio' is the ratio of bandwidth sold to bandwidth provided on the backbone: in eircom's case the contention ratio is 24:1 (48:1 on "starter"), meaning that for every 24 1Mbps connections sold, 1Mbps in total is provided on the backbone for them to share. 48 customers would share 2Mbps and so on. This is about the usual contention ratio for business-class DSL services worldwide .
We do not give any guarantees to customers on contended links, however the chances of them experiencing poor service on our services are low. Remember i-stream is a best effort service and should be sold as such. Remember also that this service connects them to the internet!!!. If congestion is experienced on i-stream the chances are that they have hit a slow connection some where on the internet.<hr height="1" noshade id="quote"></blockquote id="quote">
<blockquote id="quote">quote:<hr height="1" noshade id="quote">In real terms, If you are connected to a 1 MB connection with a 20:1 contention ration, this means that 1MB is provided for a group of 20 users. However, the contention ratio does not apply to one single group of users in the same area. So for 1000 users, 100MB would be available, shared between all 1000 users. Therefore the contention ratio will only affect your connection if all 1000 users on your exchange are online and saturating their downstream link. This is incredibly unlikely due to the sporadic nature of Internet traffic.
Normal Dial up connections are `negotiated' rather than contended. This means that once the maximum number of users are connected at one time, no other users can connect. This is when you would hear an engaged tone. A Contended service means that this never happens, the bandwidth simply redistributes itself depending on how many users are connected.<hr height="1" noshade id="quote"></blockquote id="quote">
http://www.idnet.net.uk/broadband/contentionratio.html
http://www.getonlinebroadband.com/faqs/faq02.html
http://www.getonlinebroadband.com/faqs/faq29.html

chopsky

30-11-2003, 07:17 PM

Earlier in the forum, Karnaugh suggested that perhaps ProAsm shouldnt have told all of us about the Contention Ratio Sentech will be offering as then we wouldnt be worrying. I think now that ProAsm has provided us with all the necessary info(as shown above), we can all be quite satisfied that Sentech are going to offer us all a great service and that there is indeed nothing to worry about.

Big up to ProAsm!
First month, Im signing on.

beyers

01-12-2003, 07:37 AM

Thanks ProAsm for the information. It is appreciated.[:)]

jus

03-12-2003, 10:08 AM

At the end of the day contention ratio is the only viable business model for broadband (and even any kind of Internet connectivity) sales from an economic standpoint. It is completely in line with international norms, and 50:1, 20:1 ratio's for residential and business respectively are standard overseas in countries such as the UK. Every ISP operates with contended bandwidth, otherwise they won't succeed as a business. Dial-up style connections are typically contended in the hundreds to one, and Diginet connections even with CIR's are in the region of 15:1 - 20:1. Obviously this differs from ISP to ISP, but in general you pay for what you get, and better ratio's or CIR's cost more.

The reality is as ProAsm said, networks and bandwidth can be carefully managed to ensure a good level of service all round, otherwise no one would buy the access.

Also, with the MyWireless system, it works the other way round to the consumers advantage at some times as well: While if the cell is heavily loaded you will not see such high bandwidth, while the cell is not being used you will probably burst to even higher speeds than you are paying for.

This is because the contention is at a cellular level (35mbit:1000 users) rather than a per-connection level.

I stand to be corrected on some of the details, though...

-jus

chopsky

03-12-2003, 11:14 AM

<blockquote id="quote">quote:<hr height="1" noshade id="quote">For instance, Telkoms ADSL has a Contention Ratio of 512:40 (stand to correction here) which means the DSLAM you are connected to at the exchange holds 40 connections.
Now how many people in high density areas have ever had their ADSL drop to 1KB/sec as 40 connections there is easy to achieve.
Now although a 512:40 looks good and is according to world standards, they go and destroy that by adding a Cap - so at the end of the day you would have been better off with a 512:200 system for instance.<hr height="1" noshade id="quote"></blockquote id="quote">

Would you rather have 512k:40 or 35mbit:1000?
Let's take a look

35mbit(35840k) / 512k = 70
70 * 40(users per 512) = 2800

Thus Telkom's ADSL in comparison = 35mbit : 2800

Now is Sentech's 35mbit:1000 really THAT bad? I think not... [^]

Zeliard

03-12-2003, 01:43 PM

35mbit:1000 is great[^], provided that the same or better "contention" ratios are maintained throughout your communication path (i.e. local/intl links). In any event, the narrow-most point will become the bottleneck.

Karnaugh

03-12-2003, 02:11 PM

The international standard for ADSL is 50:1 in general as ProASM said.

Sentech's 35Mbps:1000 works out to 70 512K connections to 1000 people, a contention ratio of 14:1.

Some other points to note...

Contention ration does not give an acurate idea of the service that you can expect at all. For instance, it may be 40:1 on ADSL, but there are only 2 peering points into the IPNet from there - Thus each half of the ADSL users are routed via Bellville and Rosebank into a ~100Mb connection. For 1:1 (IE, everyone downloading at 512Kbps similtaneosly over the same route) that would allow for 400 ADSL users. International contention gets even worse.

<hr noshade size="1">iActive internet services
http://www.iactive.co.za

jus

05-12-2003, 09:49 AM

And let me add that a 14:1 contention ratio is exceptionally good. It is way better than ADSL, ISDN, even most Diginets.

-jus

mithrandi

05-12-2003, 11:13 AM

Exactly. I might add that on my 128K ISDN connection via SAIX (which is what, 100:1 contention?), I have absolutely no problems maxing the connection almost 99% of the time I am online; and that's on international traffic. So, really, there's nothing to complain about as far as Sentech contention ratios are concerned.

mithrandi

Doomy

12-12-2003, 03:09 AM

Hi Guys,

1st time poster. Lets just say, its more in the region of 20-30:1 ratio. Currently we are trying to get it down to 20 or below, but for know count on 20-30

Doomy out.

PierreLeRiche

12-12-2003, 09:54 PM

<blockquote id="quote">quote:<hr height="1" noshade id="quote">Originally posted by mithrandi
 Exactly. I might add that on my 128K ISDN connection via SAIX (which is what, 100:1 contention?), I have absolutely no problems maxing the connection almost 99% of the time I am online; and that's on international traffic. So, really, there's nothing to complain about as far as Sentech contention ratios are concerned.

mithrandi
<hr height="1" noshade id="quote"></blockquote id="quote">

Your logic is flawed. With ISDN you pay for the time that you are online. The usage patterns are therefore completely different. DSL users are always online (as will MyWireless users), and if there's no cap they will leech like crazy. Most ISDN users are only online for a short period during the day to get their e-mail and to do light web browsing - anything more and it becomes too expensive. I have reason to believe that the percentage of people taking advantage of ISDN + R7Call to leech all night and all weekend is quite low.

Karnaugh

12-12-2003, 10:32 PM

Err no, *your* logic is flawed.

*some* DSL users use it for downloading crap loads of porn etc. Alot of them are companies that use it during the day for just pulling mail ever 15 mins or so.

Thing is for the connection to saturate, *every* person would have to be using their full line at that exact nanosecond, an unlikely event.

Also see multiplexing... [|)]

<hr noshade size="1">
"Since light travels faster than sound, people appear bright until you hear them speak."

NetLink Research

PierreLeRiche

13-12-2003, 08:11 PM

<blockquote id="quote">quote:<hr height="1" noshade id="quote">Originally posted by Karnaugh
 Err no, *your* logic is flawed.
<hr height="1" noshade id="quote"></blockquote id="quote">

*sigh* let me explain it again:

DSL users don't download because they can't (cap and port shaping). MyWireless won't have restrictions on download so you can expect the usage of a typical user to be greater than a typical DSL user and way way greater than dial-up users (who aren't even connected for 95% of the day).

The "safe" contention ratio is determined by the typical usage pattern of the users. If usage is typically very light (dial-up) then you can stack the contention ratio, but if users will use it more often (uncapped, always-on services) you have to have a lower contention ratio to have a reasonable service level (i.e. percentage throughput of the maximum).

Come on, it's not that hard to understand...

Whether the 35mbit/1000 will be enough only time will tell. Just because ISDN works well with a 200:1 contention does not guarantee anything for MyWireless.

Karnaugh

14-12-2003, 11:02 AM

Um, no, you are still wrong.

A good percentage of the users do not download because they dont need to.

<hr noshade size="1">
"Since light travels faster than sound, people appear bright until you hear them speak."

NetLink Research

PierreLeRiche

14-12-2003, 11:12 AM

<blockquote id="quote">quote:<hr height="1" noshade id="quote">Originally posted by Karnaugh
 Um, no, you are still wrong.

A good percentage of the users do not download because they dont need to.

<hr noshade size="1">
<hr height="1" noshade id="quote"></blockquote id="quote">

What's your point? Did you even read my posts, or are you just trolling?

My original post was in response to Mithrandi who claimed that because a 200:1 contention ratio works well for ISDN it would automatically mean that the MyWireless contention will be equally great (i.e. you almost always get the maximum advertised speed).

I have now explained twice why you cannot make that assumption. Are you trying to tell me that Analog dial-up, ISDN dial-up, DSL and MyWireless users all have the same usage patterns? That's rubbish...

microfast

14-12-2003, 11:29 AM

<blockquote id="quote">quote:<hr height="1" noshade id="quote">
Originally posted by Karnaugh
Um, no, you are still wrong.<hr height="1" noshade id="quote"></blockquote id="quote">
<blockquote id="quote">quote:<hr height="1" noshade id="quote">Originally posted by PierreLeRicheWhat's your point? Did you even read my posts, or are you just trolling? <hr height="1" noshade id="quote"></blockquote id="quote">

Hi PierreLeRiche,

ignore him, he had a bad day a while back, seems like it's lasting the whole month.

There's no light at the end of this fellas tunnel [:D]

jus

14-12-2003, 06:28 PM

I think the point is to compare apples with apples, and not another fruit. 35mbit:1000 still represents a better contention ratio than found with many DSL connections in first world countries.

-jus

ProAsm

15-12-2003, 12:28 AM

A point that everyone seems to misunderstand about Contention Ratios regarding Wireless networking.

Not like ADSL or ISDN which operates on a fixed line, Wireless cannot be determined on a single or a number of connections, simply because you radiate signals in many directions and it is possible to enter several cells at the same time.
So calculating 35mbit / 512 etc, or refering to 20:1 or 50:1 is not really correct.
It is therefore that Wireless Contention Ratios are calculated at the network output of the cell.

mithrandi

03-01-2004, 05:08 PM

<blockquote id="quote">quote:<hr height="1" noshade id="quote">MyWireless won't have restrictions on download so you can expect the usage of a typical user to be greater than a typical DSL user and way way greater than dial-up users (who aren't even connected for 95% of the day).<hr height="1" noshade id="quote"></blockquote id="quote">

I don't follow; I don't see why the usage profile of MyWireless users would be so incredibly different from dial-up. It probably won't be exactly the same, but I'd expect it to be reasonably similar; ie. that power users will be a fairly small minority. In fact, if the majority of users are power users, then I would expect Sentech to go bankrupt from what would then be a flawed business model.

mithrandi

musnit

06-01-2004, 06:19 PM

Not many dial up users are power users because of the costs involved....but with uncapped dsl theres just a flat rate. People can dload as much as they like so there are many more power users...im not sayin that all dsl users are power users...but probably over 40% of them are... so if theres a contention ratio of 35mbps:1000 and 400 people are constanly dloading then you would probably never get speeds higher than 35000/400 - about 90kbps???

Karnaugh

06-01-2004, 07:51 PM

Quite correct, if all the Sentech users downloaded all at the same time, the service would be useless and crawl along at 0.5Bps. Of course every single internet connectivity is exactly the same if not worse, so this is a pretty pointless argument.

<hr noshade size="1">
"Since light travels faster than sound, people appear bright until you hear them speak."

NetLink Research

freeek

06-01-2004, 07:55 PM

I have been on a 56k connection for about 6 yrs now and so have most of my friends. I download on one weekend +- 1gig and so do they.

We all considering mywireless! Im just waiting to see 2 things. local gaming pings(i don't expect great international, "local is lekker" ;) ) and the price of the modem upfront.

2 weeks 2 go!!

..- dot dot dash ;)

Perdition

06-01-2004, 09:08 PM

Sentech are not providing the modem up front, you will need to sign on with one of their partners.

freeek

07-01-2004, 12:04 AM

one of them is planetmars!

..- dot dot dash ;)

AcidRaZor

07-01-2004, 08:16 AM

freeek, you insane? or going insane?

planetmars isn't offering a modem upfront... or gimme the url before I bitchslap youz :)

freeek

08-01-2004, 12:53 AM

apparently, if you sign up with planetmars you can win win win, not sure what ;). goto www.planetmars.co.za/broadband. then go the broadband forums link. check it out

..- dot dot dash ;)

Perdition

08-01-2004, 01:21 AM

I believe it was mentioned on this forum what you could win, something like a free year (though you still have to pay for the second year!).

Still I don't think I would sign up with a company whose catch phrase is "Chicks love a phat pipe" [;)]

Strobemeister

10-01-2004, 06:52 PM

Why not? I think its a great catchphrase. Wonder if its true?[:D]

Telkom - South Africa's Handbrake to progress.

musnit

10-01-2004, 07:25 PM

<blockquote id="quote">quote:<hr height="1" noshade id="quote">Originally posted by Karnaugh
 Quite correct, if all the Sentech users downloaded all at the same time, the service would be useless and crawl along at 0.5Bps. Of course every single internet connectivity is exactly the same if not worse, so this is a pretty pointless argument.
<hr height="1" noshade id="quote"></blockquote id="quote">

and, like I said, if 40% of the users dload at the same time we would all get speeds under 90kbps...and most of the time there probably are 40% of the users downloading(I think)??? So we would hardly ever get over 90kbps???

MOnk

11-01-2004, 03:19 PM

man you ppl worry too much, you just see these figures and you get all confused. Just calm yourselves down and watch what happens, I am pretty sure sentech would not sell a service to you if they expected you to have basically no bandwidth. So just forget about the contention ratios if it still confuses you, after all action speak louder than words (or numbers ;p).

silversurfer

12-01-2004, 10:28 AM

<blockquote id="quote">quote:<hr height="1" noshade id="quote">Originally posted by MOnk
 man you ppl worry too much, you just see these figures and you get all confused. Just calm yourselves down and watch what happens, I am pretty sure sentech would not sell a service to you if they expected you to have basically no bandwidth. So just forget about the contention ratios if it still confuses you, after all action speak louder than words (or numbers ;p).
<hr height="1" noshade id="quote"></blockquote id="quote">

well said, monk =) [}:)] whatjooo playin nowdays, btw. You should get some call of duty going, come represent. [:D]

MOnk

12-01-2004, 10:55 PM

Yeah COD is da **** !!! :P sneaky sneaky rifleman .... :P

Haven't played anything online for ages, just playing good SP games for a while now :P (you know, POP, HW2, MP2, NWN, KOTOR) .... hehe more than enough to keep me busy ..... but I'll get back into online when I find a worthwhile game, CS is just not my thing anymore :p

mithrandi

12-01-2004, 11:25 PM

Tried Wolf:ET or CPMA?

antowan

13-01-2004, 06:28 AM

Hi there

Why don't you try America's Army. It is a great game with a local server on games.saix.net

FUN!!! [:D]

The fun is endless. Don't forget about Raven Shield which in terms of graphics and level of game play is probably the most advanced game in South Africa at the moment. Thus you cannot do anything but give it horns! [}:)]

Cheers
Antowan

<blockquote id="quote">quote:<hr height="1" noshade id="quote">Originally posted by mithrandi
 Tried Wolf:ET or CPMA?
<hr height="1" noshade id="quote"></blockquote id="quote">

He who does not understand the value of war at the right time, cannot comprehend the value of life at any time - Anonymous

MOnk

13-01-2004, 09:39 PM

Yeah I used to play Wolf:ET often, not sure what CPMA is although ?

Karnaugh

13-01-2004, 11:39 PM

OT...

<hr noshade size="1">
"Since light travels faster than sound, people appear bright until you hear them speak."

NetLink Research

mithrandi

14-01-2004, 12:49 PM

Yeah, yeah. Moderate me. CPMA (http://www.promode.org/) is Challenge ProMode Arena, the only way to play Quake 3.

mithrandi

Deckert

15-01-2004, 10:46 PM

man you ppl worry too much, you just see these figures and you get all confused. Just calm yourselves down and watch what happens, I am pretty sure sentech would not sell a service to you if they expected you to have basically no bandwidth. So just forget about the contention ratios if it still confuses you, after all action speak louder than words (or numbers ;p).

Or IP numbers. Every power user I've spoken to about MyWireless wants a dedicated IP address. I really don't see the big issue - they have to dish out IPs on a permanent basis *anyway*.

Let's hope we don't have to create a mywireless.co.za so complain, like Telkom's ADSL users have done. Oh, bummer, mywireless.co.za already belongs to Sentech...

--deckert

Perdition

15-01-2004, 11:00 PM

Deckert, you can ask for a static IP on the 512k package. This is the package that most SOHO and power users would choose anyway. Also I believe Sentech are bringing out business packages later this year which will more than likely include static IP's.

Deckert

16-01-2004, 02:12 PM

Perdition, it seems to be that way. But, being a power user does not make me a power downloader. Sentech should realise this - The 128k package is more than enough for me. I work on and maintain many systems remotely. Latency and reliability is the biggest issue for me. For all that I care, I can have a 32k link, as long as I get a static IP.

mbs

16-01-2004, 05:08 PM

Right - I'm with Deckert, and do much the same thing in terms of remote support for which I ***WANT*** a static IP...

Perdition

16-01-2004, 07:44 PM

I'm with both of you, I made an assumption on "power user" equating to "power downloader". I require a static IP but don't download enough to warrant 512k. I don't want to pay R800 extra per month just for a static IP and bandwidth I won't use. Perhaps if more people speak up about it Sentech will reconsider?

mbs

17-01-2004, 02:52 AM

Right - maybe RPM could consider running a poll on this site to gauge the scope of the need for Sentech to adjust their offerings suitably - RPM please respond...

rpm

17-01-2004, 05:28 AM

Hi Mbs

Please mail me a question and answers which you consider suitable. It will indeed be an interesting poll.

Regards,

RPM
rpm@myadsl.co.za

ChezAnwyne

17-01-2004, 07:33 AM

<blockquote id="quote">quote:<hr height="1" noshade id="quote">Originally posted by Deckert
Let's hope we don't have to create a mywireless.co.za so complain, like Telkom's ADSL users have done. Oh, bummer, mywireless.co.za already belongs to Sentech...<hr height="1" noshade id="quote"></blockquote id="quote">
Seems like rpm has been thinking ahead.
www.mybroadband.co.za already points to this site [:D]

rpm, care to comment on your plans with MyBroadband.co.za ?

Chez

rpm

17-01-2004, 08:49 AM

Hi ChezAnwyne

My initial intention with the site was to host a backup forum there is case this one goes down (that was during the time of constant forum downtimes). The other idea was to amalgamate MyADSL and MyBroadband to include all broadband services as our members will definitely be interested in these other services as well. This has since happened. This brings us to a more important point, namely what users would like to see happen on MyADSL. What features or new forums might be advantageous etc. The basics like no advertising on the site, open and objective discussions etc. will always hold. My initial aim with MyADSL was to deliver a service to ADSL users in SA and serve as a meeting place for these users. I think it now serves as a meeting place for all broadband users, and therefore I just wanted to prepare for a possible amalgamation of names :-)

Regards,

RPM
rpm@myadsl.co.za

mbs

17-01-2004, 03:55 PM

For RPM - while the poll may be a good idea, it has perhaps been pre-empted by FREAKAZOID's offer to raise any questions with the Sentech folks in his meeting next week - see 4th posting on
http://www.myadsl.co.za/forum/topic.asp?TOPIC_ID=1530
I'll post the question regarding static IP's for him to raise with them, amongst others that forum members may want raised...