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ADSL Bandwidth Limiting?
axerzak asks:
"Does anyone know how the bandwidth on Southwestern Bells
ADSL service is limited (from the telco central switch or
customer premise)? Running Linux with GTE service allows
maximum throughput of 1.5 mbps even though only 384 kbps
is subscribed. This leads me to believe that the service
from GTE is limited from the customer premise not the
central switch. Thanx for any insight."
From what I've read, the actual bandwidth can often exceed the guaranteed rate that SWBT or whoever will sell you. However, I ran across a debate among wireless providers of high-speed Internet access (T1 speed and higher); Some of them argue that if you can sometimes give a customer higher speeds than what they paid for, it's a good thing. Others say that customers will grow accustomed to that service and become dissatisfied when they get the lower speeds that they actually paid for. I hope most ISPs take the first position rather than the second, but this might explain ISPs/Telcos decisions to limit bandwidth "artificially."
Around here (Durham, NC) GTE has what they call a CIR (Committed Information Rate). According to the gods-awful html sheet they emailed to me when I was asking about adsl with them, the CIR is:
ADSL data is transported using frame relay from your CO to GTE's Main CO and then to the ISP. These frame relay circuits are shared by other ADSL and Frame Relay customers. The Committed Information Rate (CIR) is the data rate guaranteed by GTE between you the ISP when everyone else is also actively using their ADSL service.
Basically, you have a guarantee of so much of that frame relay circuit. You may well be close enough to the switch and blessed with 3mb/s, but if their frame relay is overloaded you'll only be sure to get your CIR from the telco to the ISP.
Effectively limiting you to the CIR. From the pricing scheme, you are also basically paying for the CIR rather than the top end speed for your circuit.
The CIR, btw, for this area starts out at 16Kbps and steps up to 384 Kbps at the priciest (1.5m/768k (384)).
PacBell offers 384k/128k ADSL, however your upstream is capped at 128k(pretty standard.) If your line qualifies, your base is 384k but you can get up to, according to PacBell's page 3Mbps if you are close to the CO. I know people about a mile out that get around 1.5Mbps down. DSL speed degrades with distance so if you get more, good for you, if you don't oh well. The real limiting factor is the 128k capped uplink, I know a couple guys sharing a 384k/128k DSL line, while one is playing Tribes and the other is FTPing, the uplink becomes saturated and lag sets in pretty bad. Get SDSL where possible to avoid that. The synchronous data transfer will make your connection a lot more efficient.
While there may be techniques where bandwidth is limited artificially, there may be other circumstances. With my Pacific Bell ADSL line the download speed they were willing to guarantee was 384K BPS. But, if you are close enough to the switching station, and the line ran nice and clean, and the moon was in the seventh house..., you could get more; in my case i was close enough, etc., and i get about 1.5 Meg BPS. So, it's possible that the 384K quoted is a minimum; if you get more, they don't care, but they can't tell if you'll get more until it's running.
This leads me to believe that proximity to phone switching stations will become a factor in house prices, creating areas of slightly higher prices, the same way that mass transit stations do. I know i wouldn't want to go back to anything less when i move...
mahlen
Why do kamikaze pilots wear helmets?
It's worth pointing out that many ADSL deployments seem to run ATM PVCs from the DSLAM (DSL box at the CO) to the ISP - the PCR is the Peak Cell Rate (i.e. max burst rate) that you'll get, and the SCR is the Sustained Cell Rate that defines the guaranteed minimum rate (like frame relay Committed Information Rate).
For more information, see the ATM Forum or ADSL Forum websites.
The guaranteed speed is 384 Kb/s...
The maximum speed is 1.5 Mb/s
I think that it's limited on their side... probably through hardware, because everyone seems to have the same speed ratings for their services...
I'll be moving to Houston in about a month; it seems that SWBell and GTE are the only two telcos around that will do DSL around there. (?)
GTE doesn't cover my new neighborhood so I'm thinking about going with SWBell and nol.net dsl service.
I'm just posting to say anyone's opinions on GTE vs. SWBell, adsl, nol.net, or whatever would be greatly appreciated.
Absolutely. I'm still in the process of looking for a new apartment or house. My company is providing a sort of relocation service, and one of the items I listed was proximity to the telco's central office.
I have GTE and My friends in pac bell area (like one or two suburbs over) get it for half price at (guaranteed 340/128, uncapped) while i get only 128/64 :(
bastard monopolists
everyone goto www.handsofftheinterent.com!!!
lets bring in some real competion!
For example, the least expensive service involves getting one single dynamic IP address. There is currently nothing in place to stop you from checking out multiple IP adresses. In fact, people are doing that right now. And SWBell is completely aware of it and are tracking it. The guy I talked to said they're not doing anything about it right now (beyond monitoring), but likely will in the future.
A friend of mine who just got ADSL from SWBell is also getting very speedy transfers - in excess of the advertised top speed for the service he bought. I can't help to think that these two situations are linked and after the intial roll-out time is done (SWBell is still frantically running around and trying to get all this to work) they'll begin to limit service closer to what they've in fact sold to their customers.
384K is actually the lowest `guaranteed' speed. 1.5 MB is the highest speed you can get downward from them on that specific ADSL configuration.
I have USWest RADSL with a local ISP. The first weeks of service my Cisco DSL Modem was "Trained" for, and getting, 1.5Mb/s. I only pay for 256Kb/s so I asked a USWest tech about it. He told me my ISP sends the speed my Modem should be set to, to USWest when the service was created. Then USWest sets the speed each time my modem comes on-line by sending this "Training" signal down the wire.
:)
I now get a solid 512Kb/s, (maybe I should have kept my mouth shut
Your bandwidth is limited via ATM PCR to 1.544Mbps if you bought the basic, 6.0Mbps if you bought advanced.
However, since it's ATM and you get a PVC worth that much bandwidth, you'll probably find your DSL line is faster than your 8-port 100Base-TX hub workgroup hub...
"Nothing was broken, and it's been fixed." -- Jon Carroll
Agreed...
Using USWest's Megabit with an independent local ISP. The Cisco 675 has always showed the line trained at 768K down 256K up. (Paying for 256K down, 128K up). The first two weeks I was using it with my ISP it seemed I was getting throttled right down to 256K. After about two weeks the throttle became 512K. I'm not sure if that's a judicious decision by my ISP based on observing my bandwidth usage for a couple of weeks or just the way things have worked out. I don't upload enough to have measured my actual throughput that direction.
The bandwidth throttle for DSL lines is configured on the router of the ISP. Uswest simply makes the connections. Same deal with ATM lines, etc. If you're lucky, the ISP can forget to throttle it back at all, and you'll get the full 1.5Mbps.
Of course, USWest could be the ISP as well...
So in my setup (Portland, Oregon) I am definately throttled at the CO and most likely by the ISP as well.
.......
Choochus
I'm using SWB ADSL and I am sure I live fairly far ~17 kilo-feet from the switch. THe max distance is supposed to be 19 kilo-feet so I feel pretty lucky to be getting anything above 384 Kbs.
If you have a home security system, MAKE SURE that your ADSL signal is NOT running through it. Normally, all phone lines go to the security system first and then back to the house lines so that it can preempt any calls in progress if needed to alert the monitoring service.
In my case, before the security system was even turned on, it knocked over 240 Kbs off my line speed. Once the system was turned on, my ADSL modem wouldn't even sync to SWBells signal. (The security system seemed to also be adding about 50v DC to the line!)
Today was a frustrating day rewiring things in an attic in HOUSTON of all places, but, in the end, I ended up "cleaning" my signal and now I enjoy about 1100 Kbs or about 120 KBs! Not bad for 17Kft!
Good luck
Just as a note.. My company does ADSL Installs for World Web Internet Service Provider (wwisp.com). Having dealth with ADSL and all its round abouts and with Bell (ugh) I can surely tell you that in most cases the bandwith is limited at the ISP side. It is then limited by the telco to 1.5Mbps (at least in B'ham) by the DSLAM on the ATM circuit side. It may be different in other regions using other CO side equipment. BellSouth uses Alcatel. Hope this helps a little. Ed McLain Technology Unlimited, Inc. Birmingham's Premiere Network Solutions Provider. Linux*Windows 9x/NT/2000*Macintosh
Edward McLain
Technology Unlimited, Inc.
Birmingham's Premiere Network Solutions Provider
Linux / Windows NT \ Macintosh
Ed.
To Be or not to Be.. It's all the same at the end.