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Reselling DSL? I looking as cost to sales ratio... How many DSL users can a Single Full T-1 line handle?

Posted on 2005-03-31
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Im looking into reselling ADSL in my neighborhood and was curious if anyone has done the math or knows of a average that a T-1 line can handle? You figure that not all users will be up 24/7 surfing simotaniously, so given that how many 1.5/down 768/up users can a Single T-1 handle? I googled the hell out of this and nothing. If in the know, maybe i could get an average of a DS3, T3, and Fiber(cheap fiber). Thanks in advance...
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Question by:c0rrupti0n
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9 Comments
 
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Expert Comment

by:lrmoore
ID: 13676427
Well, considering that a T1 is only 1.45Mb either way....
I don't know that a typical oversubscription ratio would be for DSL users, but get 3 or 4 people trying to stream audio, download files, and swap MP3's at the same time and you've just about shot your wad.
In the frame-relay world, we use a 4 or 6 to 1 oversubscription rate.
T3 is equal to 28 T1's, but at 45Mb, it's a wide enough path that you should be able to sustain several hundred subscribers.
Fiber can sustain up to >1Gb if you can afford it. Redundancy and failover have to be considered if you're going to provide your subscribers any type of service level agreement or guarantee of service.
From a cost perspective:
T1 = $600+ /month, expect 6-12 weeks for install of service
T3 = $12,000 /month, expect 6 months to year wait for the service
Fiber = you might get it a lot cheaper if you are in an area serviced by outfits like Yipes! communications.
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by:c0rrupti0n
ID: 13677207
Could you explain "In the frame-relay world, we use a 4 or 6 to 1 oversubscription rate."?

And I see speakeasy.net offers a 300 dollar Full T1 and a few other providers offer T3 at 2k and fiber OC-3 (50meg Burstable) at 2100.00

Just wondering your thoughts on those prices? Are there things I should be aware of when it comes to being provided a t1 or fiber line other than it being guaranteed to be up 99% and true bandwidth?

I was thinking of picking up the OC3(50m) at 2100/m.

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lrmoore earned 600 total points
ID: 13684172
What a steal of a deal for the OC3! That's about 1/10th of what i would expect from a Tier 1 provider (ATT/MCI/Sprint)
Make sure that includes the 'local loop' charge or you will be in for a big surprise.
What does the monthly charge jump to if you go over your 50m limit? For how long?
99% uptime is absolutely not acceptible. "five 9's" is the standard for telephone service. This means 99.999% uptime.
99% = 5000 unplanned minutes of downtime per year with zero penalty. You can go days at a time with no service, and no penalty to the provider.
Compare 99.999% = 5 minutes /year of unplanned downtime

Frame-relay uses 'statistical multiplexing' to allow for one T1 at main site to support multiple PVC's to remote sites. Typically a remote site has 256/512k fractional T1. We can allow for a full T1 at main (1.44Mb) to support up to 24 remote sites at a 4/1 oversubscription ratio, and if the utilization is not too high on that, we can go up to a 6/1 ratio and support up to 36 remotes at 256k each.

DSL is ATM technology at the core and does not use the same statistical multiplexing model, so I don't think it works the same way.

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Expert Comment

by:td_miles
ID: 13690072
I would think that if you don't know the answers to these questions, then maybe you should find someone who does before you worry about setting up an ISP ? Oversubcription ratios often help to determine the "quality" of an ISP, as does where the bandwidth the ISP uses comes from. If you are purchasing from a tier1 provider, then you will pretty much get the bandwidth you pay for. If you buy from a tier2 (or lower) then there is also the chance that your provider is oversubscribing their bandwidth.

As per some of the other questions that people have already brought up, some others to ask if you have thought about:

* business plan ?
* business structure ?
* redundancy ?
* target audience ?
* competition ?
* marketing ?
* finance ?
* billing ?
* support ?
* insurance ?

Plus many others. If you're doing it for a few friends/family, then maybe most of those question won't matter, but if you are going to setup a proper business and offer services to the general public then there are a lot of things you need to think about. I'm not trying to put you off starting a business, but you should do so from an informed perspective.
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by:c0rrupti0n
ID: 13691002
td miles: I wasnt planning to impliment this yesterday or anything. Am I doing my research as we speak now about this topic? Or Am I not? I appreciate you being so concerned about my proper business structure, however these are the kind of questions that are quite obvious and didnt need direction on. I simply wanted to know from a technical stand point on related costs and as well as bandwidth costs an such...

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Expert Comment

by:td_miles
ID: 13693634
cool, well all I can say then is good luck :)

I'm sure you can google as well as I can, but here are a few bits:

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http://www.yak.com.au/support/adsl_info.php
A high grade business connection may have a contention ratio of 8-1 or less while a cheap residential service could be as high at 130-1.
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http://archives.neohapsis.com/archives/openbsd/2002-01/2560.html
for a dialup environment, you can figure that 7:1 to 10:1 oversubscription
of the modem pool is ok; for concurrent users, the same factor can be
applied with some success to oversubscription of bandwidth. keep in mind
that while Cable/DSL customers are "always on", they aren't "always on".
their usage will probably be more frequent than a dial subscriber, but that
box sits idle most of the day.
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http://www.open.com.au/radiator/WISPCookbook.pdf
Typical residential service would offer best effort service. Historically, this service requires about 12-15 Kbps per subscriber
Typical small business service would include 256 Kbps and, often, a 512 kbps service. These services are usually oversubscribed 4 to 1.
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http://www.nwfusion.com/newsletters/isp/0522isp1.html
GTE, which has done some of the most thorough real-world DSL testing, says that 10-to-1 over subscription still provides full throughput to customers 95% of the time, even if they are all surfing the Internet simultaneously.
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http://www.nextgencommunications.net/wisp/2004/09/dependence-on-oversubscription.html
As Internet usage is bursty by nature we have been able to cram 100 +/- users on to a T1 pipe.
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http://www.northwestwisp.com/technical.htm
Typically a DSL line is oversubscribed by ratios between 4:1 to 25:1.
----

The first quote seems a bit out. 130:1 would be very unrealistic I think (except maybe in some countries that have very low international pipes).

Maybe you can call up a few ISP's in your area and ask them what their ratio is. You'll probably find that the more unwilling an ISP is to quote this figure to you, the more likely they areusing a high ratio.

So, decide on what sort of service you wish to provide, who your target audience is and then look at your oversubscription ratio. If you attract a lot of users who leave their PC's on all the time with file sharing apps running, then rather than using an average of 10-20% of their connection speed, these users will be using 100% all of the time. This is the reason that ISP's don't like these apps/users. Rather than having a fixed ratio, you may do better to simply monitor your bandwidth usage and add more bandwidth as it exceeds a threshold (I think 70% was what one of the above links suggest). It is also pointed out (in ISP cookbook) that having both business & residential customers help you get most out of your bandwidth as business will be active during the day and residential most likely to be active during the evening. This will maximise the usage of your purchased upstream bandwidth.

Where I live (AU) some ISP's use port prioritisation/shaping to skew things so that file sharing apps can't hog bandwidth. This gives a better experience for those who are just browsing at the expense of slower downloads for those who are trading MP3's. It also allows the ISP to go with a higher ratio, as "normal" users don't notice it as much when people crank up the P2P.

HTH.
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by:c0rrupti0n
ID: 13710929
I thank you both for the help, If I could split the points I would...
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by:td_miles
ID: 13711632
ummm, you can:

http://www.experts-exchange.com/help.jsp#hi19
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Can I split the points?

Yes. Scroll down to the bottom of the question, just above the text box, and click the "Split Points" link. Select the radio button of the comment who you want to Accept as the Accepted Answer. Only one button can be selected. Set the point value (a text box above the comment) of how much you want this person to receive of the points. Then set the point values for each of the experts comments to whom you want to allocate points and these will be considered Assisted Answers in helping you resolve the issue. Double check your information and then click the Submit button at the bottom of the page. One note: the total points of the splits must equal the amount you asked the question for itself, and no person can receive fewer than 20 points.
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Don't worry about trying to get this question changed, just remember next time :)
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by:c0rrupti0n
ID: 13712469
Oh damn, sorry dude... I got yeah covered next time...
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