For example, let’s say I’m on TWC’s Roadrunner service.
They don’t restrict me at all. So I can, if I can find enough sources to download from, run wide-open at 6Mbit/s 24/7*. I’d pay about $45 a month for this.
A fractional DS3 at 10Mbit (admittedly it’s also 10Mbit upstream) will cost you about $4400 a month according to the site I’m looking at. So…to supply all of their customers running a full speed at all times would make for a lightning-fast model bankruptcy.
Obviously your big names like TWC get a much better price on their bandwidth than that. However, I have little doubt that if everyone on Roadrunner in my segment were to get on and start downloading at 6Mbit/s the speed on the segment would plummet to absolute crap.
So, I’m guessing there’s some rule of thumb or equation that is used to determine what percentage of the available bandwidth any user will use along with how much X users will use at the peak hours of the day, etc.
Anyone have any information about this?
-Joe
*Yes, I know that the upspeed is a paltry 384Kb/s-ish. But most residential users don’t care a whole lot about their upload.
Your cable modem is assymetrical as you note, with far slower upload speeds than download. You’re also sharing your bandwidth with everyone else in your neighborhood; cable is a shared resource, and if lots of your neighbors start signing up for RoadRunner you may notice a crunch. Finally, in all likelihood you don’t have a static IP associated with that account.
The fractional DS3 is a multiplexed series of physical circuits which must be installed in the client location, and hooked up to a router. The client would deal with his own IP issues (most likely) and would not be sharing the circuits with anyone, and would have guaranteed bidirectional symmetry on the link. A very different creature entirely.
My ISP in the UK reckons an average users moves approx. 7GB of data a month.
That includes all the hardcore downloaders caning their connections - most users use significantly less than that.
Is your connection condended at all? Most UK home ADSL services are sold as a 50:1 contention, meaning you effectively share your bandwidth with 49 other users.
ADSL tends to be used as a “bursty” service, although that’s rapidly changing with streaming apps and usenet etc.
So for example… although on a 2MB connection your max speed is about 246KB/s, with contention it could be 1/50 of that and still be within the terms of contract.
Some ISPs are introducing caps and/or throttling now to combat this problem.
ISPs rely on most users not hammering their connections, but the more high-bandwidth users they get the more their profits get hit (although the British Telecom monopoly in the UK fixes prices more than in the USA).
Though there are typically no explicit download/upload limits, an ISP will often exercise a clause in the TOS that says you cannot be an excessive burden on their systems.
I have seen discussions about this in the Pit before; the beef is that they seem to arbitrarily decide how much is too much, and then they send a nastygram to the offender saying to ease off.
My customers aren’t the DSL subscribers, they’re the ISPs and other high end users. If your question is how can we set speed limits, that’s easily done in the fast packet switch. There are settings at physical port, logical port and virtual channel. All are set according to terms agreed upon at the time of contract negotiations. The switch management software is extremely versatile and there are lots and lots of traffic shaping conditions I can place on data throughput, bursting, prioritizing, and more.
The cheapest packet switching service we sell is probably frame relay. A FR DS3 (44Mbps) can cost you from 5 to $7 thousand a month, depending on your company’s buying power. A major ISP gets them even cheaper (wholesale), probably around $3500. So to break even, an ISP would have to get at least 117 subscribers per DS3. Yet if all 117 get online at the same time, there is only about 376kbps available for each subscriber, if I did my math right. The ISP is hoping that won’t happen, but ther again they don’t gurarntee through put, they only say “speeds as high as…”
Thing is, though, I understand what you’re saying here. The 117 subscribers per DS3 is just basic math.
I just figured there was some way the ISPs have of looking at it that helps them determine “If we have 100 users we will have this much bandwidth available to them because at peak hours our user base only uses X% and therefore we need to have a Y pipe to keep our CSRs from getting hammered by bitching customers.”
Hmm…not a very good sentence - but did I get my meaning across?
Ah yes, the numbers game. In the industry we call it statistical multiplexing. In order to do it properly, the provider must collect usage data about their customers. For example, it might be known that 90% of the time between peak hours of 7pm and 11pm, no more than 65% of the customer base is using the network. Of course that means 10% of the time there will be a heavier load on the network and therefore a perceived degredation of service and the provider has to be ready to take the hit on its customer satisfaction levels.
This only makes sense - I mean why roll out a DS3 into a community and promise 28 subscribers they can get full T1 throughput, when you know that most of the time no more than 18 subscribers will probably be using the service at any one time? Instead tell your subscribers that they can get “up to” 2.44Mbps (DS3÷18). If your statistical data are correct, most of the time your customes will be happy. Once in a great while, they’ll be limited to 1.5Mbps if all 28 subscribers happen to be on the system at the same time.
When network analysis detects an increasing demand on resources, the provider have to make the decision on when/if to upgrade the facilities.
Can I tack a question on in here, seeing as it looks like the people who will probably know the answer are already here?
DSL service here in South Africa is supremely expensive, and all of it is capped. I currently pay about $80 bucks a month for the DSL itself, and then I have to have an ISP account on top of it ($40 bucks for a 2 gig capped, shaped account. I currently have 3 accounts, because there’s no way 2 gig is enough for me, and I’m not even a heavy downloader - just a heavy streamer).
The part I’m wondering about is the shaped bit. I can’t seem to find a decent definition of what this means. I know that if I exceed my 2 gig limit, my connection is actually throttled - I can access websites within South Africa with no problem, but international websites are veritably inaccessible. What I’m wondering is, is a shaped connection a less dire form of that? Meaning, do I have slightly less bandwidth going out of the country than I would within the country? I’d assume this would be because there is far less internal web traffic than there is international.