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Was my ISP blowing smoke up my hoo-ha?

C

Crawdaddy79

Junior Member
This is DSL service.

Basically I'm paying for 1.5Mbps and I'm getting ~720kbps.

I strongly suspect I am configured for 768k service (which is offered by Verizon in my area, which incidentally Verizon shows up a few times as my domain whenever I do a traceroute). I realize my ISP is renting equipment/IPs from Verizon, I have no problems with this. I just want to know that I am configured for 1.5Mbps - and the techs were not able to answer this for me (they did not speak English very well - and/or pretended to not understand me). Finally when the trouble ticket was open for a long time, the last tech said "Yes you are configured for 1.5"

After many hours on the phone they end up saying that I am too far from the central office to get 1.5Mbps and that 700k is a good speed. They pretty much ignore everything I say about my speeds never going above 768k, and my upload being solid locked at 120-8k no matter what online test I use (I'm supposed to be getting 384).

Well, every time I connect I get a server IP and a client IP doled out to me (seen in my connection properties - they vary fairly often). I suspect the server IP is located at the central office.

When I ping this server IP 50 times, I get on average 12ms response and 0 packet loss.

I am wondering what exactly would constitute my speed getting cut in half, when neither packet loss or high latency are involved - or if the server IP isn't located the central office.

Thank you all in advance.
 
Crawdaddy79, Google for "Westell Diagnostic Icon". The result of running this software can be to tell you exactly what link speed you have negotiated with the DSLAM (what you're getting at L1), and what your noise margin and error stats (whether you have room to dial it up or not). It is possible that you have a 1.5Mb/s L1 link that has been misconfigured at the ATM VC level as a slower virtual circuit. Let's find out what you're getting from the DSLAM first.
 
Originally posted by: cmetz
Crawdaddy79, Google for "Westell Diagnostic Icon". The result of running this software can be to tell you exactly what link speed you have negotiated with the DSLAM (what you're getting at L1), and what your noise margin and error stats (whether you have room to dial it up or not). It is possible that you have a 1.5Mb/s L1 link that has been misconfigured at the ATM VC level as a slower virtual circuit. Let's find out what you're getting from the DSLAM first.
Click to expand...

I don't know much at all about DSL....but doesn't it choose datarates based on noise?

Isn't this a L1 problem?
 
Originally posted by: spidey07
I don't know much at all about DSL....but doesn't it choose datarates based on noise?
Click to expand...
Yeah, it does. The ISP will also manually cap your data rates if they detect bad S/N ratios. They HATE getting constant calls from customers about connection errors, so they'll go with a lower connection speed to avoid that problem.
 
spidey07, G.DMT ADSL starts with a configuration profile from the DSLAM that basically tells the modem what the maxes are, and it then "trains" on the line by trying frequency tests on each of a bunch of available frequency bands (the "tones") and will drop the ones that fail to carry a certain minimum SNR. Most gear in the wild will continue to drop tones if SNR performance in that tone is too bad for too long, and most gear in the wild will not try to put tones back. Even though the G.DMT signalling keeps a tone active, that doesn't mean the SNR on it is good enough for user data, that's why there's FEC (including interleaving if enabled) and ARQ layers above it.

So basically, you start with a max set by the DSLAM, and might or might not train to that max, and will drift down over time.

DSL ISPs talk a lot about distance, which is an arbitrary and wrong metric for measuring suitability of a pair to DSL signalling. What really matters is SNR headroom and usable frequency bands. With G.DMT, if you have all your tones usable (or nearly all) and a good SNR (significantly >12dB), they can probably bump the speed up a notch (if they're doing signalling the way I think they are, doubling the rate means basically eats 6dB of headroom, and below 6dB you can't reliably recover the signal). Conversely, if your SNR is low (<6dB) it will start becoming user-visible as occasional ARQ delays or even real packet loss, and bumping the speed down a notch would be a fix. I am not aware of any ISP who will automatically bump up or down like this, and you have to get to some pretty senior staff at all the DSL CLECs I'm aware of before they'll even take SNR into account when adjusting the speed up or down. They *really* want to use distance as the magic metric, to the exclusion of every more useful metric that's in front of them.

Anyway, OP is supposed to be getting 1.5M and actually getting 768k. If he was getting, say, 1.1M, that would sound like it started out at 1.5M and trained down. If he's getting 768k, that sounds like a provisioning error - which could be on the G.DMT ADSL link or it could also be in the ATM network or on the SMS. The Westell software will tell you exactly what your trained speed is, and let you figure out whether it's the DSL side or what's behind the DSLAM.
 
Originally posted by: cmetz
So basically, you start with a max set by the DSLAM, and might or might not train to that max, and will drift down over time.
Click to expand...

Thank you very much cmetz. I appreciate you putting it into terminology that I understand. The DSLAM is a modem, not a multiplexer. I find it funny that DSL is based on modem technology. Then again it makes perfect sense.

May I ask your age? Mid/late 30s or more?

Can an analogy be made in terms of training on a DSLAM and a 64k digital modem? Is there really a training stage that is constantly adjusting?

Funny how wireless is the same way. Not necessarily a training state, but a constant adjustment of L1 parameters.
 
spidey07, the DSLAM is also a multiplexer of sorts, in that it is combining n customer tail circuits into m (usually one) back-haul circuit. It's a stretch, I know. It's doing statistical multiplexing, not TDM. The DSLAM is traditionally a L1 device. ATM over G.DMT (or whatever) on the customer tail side, and usually ATM over STS on the network side, but I believe that the Copper Mountain gear let you do an Ethernet back-haul and avoid ATM (I think some SMS functionality is built in to achieve this).

It really should not surprise you that ADSL is based on modem technology, it's all digital communications, it's just wider band. G.DMT ADSL in particular has a lot of stuff designed to handle the ugliness of the real world phone network, such as allowing a POTS circuit on the low band, kind-of handling bridge taps and other reflection sources, and the whole "filter" thing for self-installs. v.92 is relatively simple and relatively fragile. G.DMT in practice only trains down, though I think the protocol allows training up, while if memory serves v.92 modems can train up/down more.

The main difference is at L2. Modems were easy. You had PPPoE (or SLIP) over your modem channel to a router on the other end. There was a box on your end, and a box on their end, and that was it. (well, actually not... there's another network below you, but modems allow you to mostly abstract that away)

With home ADSL, you typically have PPPoE over ATM, your SOHO router routes into a PPPoE virtual circuit, and your ADSL modem is bridging Ethernet L2 into an ATM PVC. On the other end is a DSLAM terminating the ADSL L1 to an ATM circuit where your cells end up in a SVC or "smart PVC" on the network, an ASAM chewing up the PPPoE-over-ATM sessions and sending them to the right provider, and a SMS terminating those virtual circuits and providing the L3 routing and shaping functions. Business DSL often takes the PPPoE out of the picture and that helps simplify things a bit. But as you can see, there are now one (ATM) or two (PPP/PPPoE) virtual circuit layers in the mix. Which means more things for somebody to screw up. Now, for extra fun, have those different layers owned by different companies, who might not cooperate well.

(Only telco guys could have designed this architecture. It's an expensive and elaborate way to make things work worse. I know the problems that they think they were solving, but even then it's overkill.)

Wireless is a much different beast, though. In the case of wireless, you're mostly looking at signal/power management as the driver for the ugliness. Remember, the ISM bands require devices to use minimum necessary power, and any mobile device certainly appreciates that kind of behavior too. When you combine mobile stations, variable interference, and the drive to keep signal strength as low as possible, it means a lot of dynamic behaviors. I think there's a lot of technological improvement ahead in wireless because we still are relatively primitive in handling all this.
 
Originally posted by: cmetz
Crawdaddy79, Google for "Westell Diagnostic Icon". The result of running this software can be to tell you exactly what link speed you have negotiated with the DSLAM (what you're getting at L1), and what your noise margin and error stats (whether you have room to dial it up or not). It is possible that you have a 1.5Mb/s L1 link that has been misconfigured at the ATM VC level as a slower virtual circuit. Let's find out what you're getting from the DSLAM first.
Click to expand...

Well the icons didn't do much (just told me my firmware/bios/etc.) with the Westell router a friend loaned me - but I was able to look at the config and see that it's configured for 864(?)/160 - well it said "DSL transciever" and I assume that's the modem. Whether that's a configuration sent to it every time it connects, or whether it's embedded is unbeknownst to me (I was unable to modify it). I look it up on Westell's site and find that it's specifically made for Verizon (it's a 327W model).

So I decided to try my old DSL modem (a Speedstream 5260; the one originally supplied to me) and of course my speed is exactly the same. I tried the utilities and they could not talk to the modem. I also looked up how to log into it, but that seemed impossible - the only IP that relates to it is 10.0.0.1 - and that turns up an invalid address. I saw that the firmware can be hacked but I don't know if that would do me any good, or if it's even possible when I cannot communicate with it.

I'm tempted to just buy a DSL modem/router from Circuit City just to see if it would make a difference.
 
Crawdaddy79, your profile in the DSLAM is for 768/128. Verizon over-provisions to compensate for the horrible overhead of ATM and PPPoE. Now that you know you've been incorrectly provisioned in the DSLAM, harass your ISP to fix it. You'll probably need to convince them to re-provision you.
 
They refuse to acknowledge that I am misconfigured. They say it's the fastest speed I can get, and if I want more I can go with their 3Mbps solution (haven't even looked into the price, but I really don't want to stay with them at this point).

I've been with them for almost 5 years, but when I get flyers from Verizon offering the exact same 768/128 service for $20 a month it's hard to justify paying twice as much just to keep my email address.

When it's time to renew my lease on my apartment (or move to a different one), I'm definitely going with a different ISP.


About two years ago I was getting tons of packet losses and a super-slow connection and it took over a week of talking to tech support (a tracert would show exactly where the packets were getting lost, but they still wanted me to clear my cache and reset my modem)) before one finally recognized that there was a problem with the network (me and an unknown number of other customers). I should have left them then, but then they lowered my price to $40 a month so I stayed.
 
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