From Owen Rubin – San Francisco
I have Comcast… Let me do my best “technical support” impersonation of Comcast:
Hello, Comcast technical support? Hi, my connection is intermittent and it keeps dropping.
Have you unplugged your cable modem, let it sit for 30 seconds, and plugged it back in? If not, do that now and I will wait?
Is your connection back on now? There, we fixed it!
Uh, I said it was INTERMITTIENT, of course it is on sometimes, just not all the time. And yes, I have done this MANY times.
Oh, well, have you rebooted your computer?
Yes, many times. It made no difference.
Oh, well, have you restarted your internet software and applications such as Netscape or Internet Explorer?
Well, not directly, because it is the CONNECTION that is intermittent not the applications, but I have done that over the last few days many times, and it made no difference.
Oh. Well, have you reinstalled these applications?
NO! It is not my computer, it is THE connection. It is dead no matter which computer I use.
Oh, you have multiple computers? Have you rebooted your router or edge device? Please remember we do not support routers and edge devices.
Yes, I have done this. But it is this router that reports that the connection keeps going down.
Oh, well, have you upgraded the firmware on this router?
…
It is usually at or before this same script that I usually loose it and ask the stupid question: Why is it that Comcast cannot accept that something is wrong with their equipment and not mine?
I’m am sorry sir, we cannot comment on the status or state of Comcast equipment.
Basically, if it is nothing wring on your end, you are SOL, because they NEVER admit that anything is wrong on their end.
What makes this more sad is that the system Comcast uses is the system my team and I designed at Pacific Bell in 1996 with a few revs forward in software. There are places and things that can go wrong. I often ask, when they ask me to reboot my machine, “Have you rebooted your cable modem router recently?” Have you rebooted your DHCP server lately?” “Have you checked your edge devices to the Internet to see if the connections are active?”
I can get about 3 or 4 return questions out before they basically tell me that THIS tech cannot help me, and they will escalate me to technical support level 2. And it starts ALL over again.
Just an FYI, the last two times we discovered (I discovered) that a local line repeater was going bad (was evident in the noise on the analog TV channels) and the second time, a section of their cable modem router had crashed.
From John Farr – New Mexico
Gee, all I did was plug in the ugly Qwest DSL “modem” (it even says modem on the case), plug in my Buffalo wireless router, and there was my DSL. Didn’t adjust a thing until I turned on the firewall. I’m feeling luckier by the minute.
My brother in Austin has cable Internet (Roadrunner). Totally loves it.
From Tim Robertson – SouthWest Michigan
I love my high-speed access, too, when the damn thing works. This last time, it came back up all on its own on Saturday, the day before Tech support was suppose to come. So when he called Sunday morning, I said it is working already.
Then on Monday, not only do I loose cable modem, but cable TV as well. When I call in, they start to ask the same asinine questions Owen spoke of. I cut them off, and said “the problem is NOT on my end, both internet and cable TV is out. Obviously the problem is on YOUR end.”
“We can send a tech out on Tuesday.”
“Tomorrow Tuesday”
“No, sir, next week Tuesday.”
Of course, it all came back on a few hours later.
Comcast is simply horrible. They really don’t know what they are doing, and don’t monitor anything to look for preventative problems. When a problem does come up, they are so long answering the phones, and sending a repairman to your house, it is a joke.
From Owen Rubin – San Francisco
It is not just Comcast, this goes to a blog of mine a while ago about the
lack of service in America these days. IN fact, I think I ranted on Comcast
as one of the causes.
“Your call is very important to us, please stay on the line and your call
will be answered in the order it was received.”
*(^)*&^ you! If my call was important, you would have more people answering
the phone! On not some clerk in a foreign country who has no authority to do
anything more than read a script! ARGH!
From Russ Walkowich – Maryland
Comcast (is the) only option available right now. Using 2wire- ranges between 4.21 and 4.46. Using CNET speed test, ranges between 3148.1 kbps and 5264.5 kbps.
From John Martellaro – Denver
I gotta chime in here.
Before I had Comcast, I heard all kinds of bad stories. So it was with some trepidation that I signed up for Comcast cable and high-speed Internet at our new house here in Denver.
I am paying for 6 Mbps. I typically get 8 Mbps.
Customer support has been terrific.
One time I had to call for support when it seemed all my Macs were off the air. I had a good conversation with tech support. They pinged my cable modem and said it looked good.
Turned out my SonicWall TZ170 (router/firewall) had stopped delivering DHCP addresses and was hung. (Happens about once a year.) So they stood by while I rebooted it, and all was well. (I was a little embarrassed.)
Billing has been accurate.
Of course, a lot of the technical conversations, which could have started out badly, were nipped in the bud when I started with “I work for Apple…” I don’t have that leverage now, so maybe things won’t go so well.
I pay $25/month for a back up system. It’s a wireless Motorola system, and I have a small antenna on my roof about the size of a dinner plate. (Mesa Networks for rural people here in the Denver area.) It’s only 1.5 Mbps, but I have it for back up and testing. Static IP. This is unbelievably useful for debugging, sanity checking, and testing whether Comcast is hosed or it’s a general Internet problem.
If I didn’t have that, I’d re-activate my dial-up service with Earthlink and set a configuration so that my AirPort Extreme (Snow) could dial out — and then I could test my internal network and all Macs. Glad I don’t have to do that.
Anyway, that’s the Comcast report from Denver.
From Bruce Black – Massachusetts
I’ve wondered a lot about why companies simply don’t just say something like “we’ve had an equipment breakdown in that area, we expect to have the problem resolved in three hours, and we regret the inconvenience”. Would that be so hard? Things do happen, I think most people understand that. I’m a tech, you can tell me that a switch went out, a router had to be replaced, a fiber got kinked and broke, whatever, just tell me something.
Why has it become standard in this country to make it policy to convince the customer / consumer that the problem is on their end, and to adamantly refuse that the problem is on the companies’ end? And this is not just in computers and internet stuff, but it seems to be standard in everything else. Has anyone tried to call a big bank with a problem lately?
I don’t even want to get started on this business of scripted tech support, or “tiered tech support”.
From Roger Born – Mojave
mediacom in ridgecrest 10.2 – 10.6 Mbps typical. rock-solid – crashed once in four years. really, really spoiled with cable modem. almost couldn’t go back to anything else.
my son, in ontario, los angeles, uses Comcast, with almost weekly outages – mostly early morning hours. fed up, he is trying dual dsl next.
google ‘may’ help with the cable modem monopolies – eventually:
http://www.foxnews.com/story/0,2933,209702,00.html
From Beth Lock – Southern Utah
Ahem.
Luckily we’ve been with a local provider since 1998. They are fantastic, they provide satellite where the phone line infrastructure is too poor to support DSL, which we have at home, and I have satellite at work. We wouldn’t even consider cable, the only one providing is is MSM through Quest. I’m so happy Infowest has weathered the big company storm. Isn’t there local service in the big cities anymore, or is it all just the mega huge companies that have the say?
From John Farr- New Mexico
>>It’s only 1.5 Mbps
Oh, you cable guys. After 14- 26 kbps (if that) for three years, I just went to 1.5 Mbps (apparently more like 1.28 Mbps down and 670 kbps up). They say I can have DSL at 3-6 Mbps for the equivalent of a car payment each month, but 1.5 is like finally being born,
so I think I’ll wait. 
P.S. What do you DO with 8 Mbps??? Anything legal?!?
Okay, next question: how do you know your speeds?
From Tim Robertson – SouthWest Michigan
Go to http://www.2wire.com and click the “Speed Meter” button at the top of the page.
Just ran mine, getting 2.39Mbps right now. Glad I am paying for 6Mbps…
Wow, just ran it again, came in at 4.80… And again, 3.96
I usually run it about six times, and do an average. But be sure you are not checking email or downloading/uploading anything when you run the test.
From Roger Born – Mojave
John, please don’t tell anyone –
with cable, we download images like these…
http://www.dusso.com/pages/EP3/EP3main.html
hi-res images here:
http://digg.com/design/High_Resolution_Image_of_Naboo
awesome desktop images, rotating every five minutes in OS X. rather addictive, you know.
From John Martellaro – Denver
I use:
http://www.speakeasy.net/speedtest/
Just got 8.851 Mbps to S.F.
What to download?
Good for downloading Disk Images from ADC. Maybe 15 min per CD image on the average. Helps download HiDef movie trailers. I think I downloaded an episode of Lost from iTunes in about 5 min one time.
What? Illegal stuff? Never! 
From John Farr – New Mexico
All over the freaking map, from 510 kbps to 1.23 mbps.
This test site is more fun, cool bandwidth meter like a tach, and nifty graphics.
http://www.speedtest.net/index.php
Lets you ping different servers worldwide. Very mixed results at least as far apart as the above.
Oh well, beats 14 kbps.
From John Farr – New Mexico
I can’t believe I went to all these different speed sites and got results from 349 Kbps (!) to 1.5 Mbps. How very droll. I realized that lots of things can affect such results, but man…
What we need is a formula: say 5-10 test sites pinging the same server, run 3-5 tests on each and average, then calculate the average real-world divergence from advertised customer speeds for each type of service and draw some meaningful conclusions… [snort] … I conclude we’re ruled by pirates and thieves and that my DSL connection was only driven on Saturdays by a little old lady from Pasadena to go to her favorite mini-mart to buy Powerball numbers and cigarettes.
STILL beats 14 kbps (and there were times it was less than that).
From Claus Wolfe – United Kingdom
Guys – I am just bout to start crying 8.851 Mbps… I wished… I’d dream of…
952 kbps download T-Com / T-Online DSL
129 kbps upload ”
I seriously need to talk to my boss about upgrading my home office connection – maybe she’ll allow me a 6Mbps DSL line… only 10 Euros extra a month. 
P.S. someone asked what do you do with all that speed. For me the bottle neck is actually uploads (as everyone can see). I do remote training sessions from my office and with upload speeds like the one above it can be rather hard to transmit both the contents of my desktop (we use Macromedia Breeze, similar to WebEx) and Voice over IP… So ideally I want a bit faster download, but a lot more upload, which in Germany only comes by buying the much faster download…
I shall go on and dream a little more…
From Carmel Glover – Australia
I don’t really care all that much. If my connection ‘seems’ fast I’m happy. If it ‘seems’ slow, I’m not. Optus claims a speed of 10, but I know they’re lying. Tests I did a little while ago showed between 4 and 6, but a lot of the time I know we get only about 2. However, the connection drops out only very occasionally, so I’m fairly happy.
From Roger Born – Mojave
excellent, carmel,
you have hit on the crux of the whole issue.
there is a happy meter here, that most of us are unaware of, which indicates our connection speed, or even the lack of being connected.
my mac, when i open a window in safari, if it says YOU ARE NOT CONNECTED TO THE INTERNET, i am not happy, and i am not happy – instantly.
i guess the closest thing to a happy meter on my mac, is that little icon in the right side of the menu bar, which, if it is full on, as it is most of the time, i know i have ‘full’ connection speed (which can wildly vary, but i tend to ignore that part).
but, if that little meter dims, or shows only a bar or two, my happiness is threatened.
how odd i never knew that about myself! thank you, carmel, for making us aware of that.
From Owen Rubin – San Francisco
It is not just Comcast that has these problems, they get the most heat because they are one of the largest cable companies, so more people are effected if something goes bad.
If you truly want to know how this all works, and it is similar for all cable modem systems, read on. Otherwise, you can stop here.
———–
DOWNSTREAM or data to your house:
A cable modem works by taking a 6 MHz “TV Channel”, typically in the digital tier above 550 MHz, and modulating it with QAM 64 (64 states per clock transition) or QAM 256 (256 states per clock transition), a modem modulation scheme, which results in about 27 Mbps to 31 Mbps of available date bandwidth per channel. More than 1 channel can be allocated, and they can be allocated per node (about 480 homes) or in smaller systems, or system wide (all nodes.) Cable modem users share this bandwidth. The typical take rate is 10 homes per note, so a typical 3 Mbps of bandwidth TO your modem should be available on average. It can go higher, and caps are based on what the supplier wants to do, and were typically set to reduce expectations of very high rates one day and lower rates the next. If more people take the service, adding more channels of cable modem data solves the problem.
In the modem itself is a tuner (several actually, but one for downstream data), a QAM demodulator, and a serial to something interface, typically Ethernet, but also USB sometimes. There is also a narrow band control channel that the modem and head end system use to talk to tell your modem which channels it should be on for up and downstream data, allocate bandwidth, and report usage info, as well as other housekeeping info. (This is the channel that many hackers would send false SMNP signals across to the modem to get it to allocate more bandwidth, just on case you were wondering! )
UPSTREAM:
Typically QPSK modulation (16 states per clock transition – works better over lower power or longer dist) which results in significantly less data, over a much smaller channel. Because upstream bandwidth is very limited, these upstream channels are small. Also, the cable modem is NOT a powerful transmitter, so low frequency channels need to be used to get the signal from your modem to the head end, or at the least, the local node which can amplify the signal for you. Obviously, with so many modems taking, power must be kept low to reduce interference as well. A 6 MHz channel with QPSK is about 18 to 21 Mbps (depending on how much error correction is applied), but the typical upstream channel for cable modems is allocated in 512K to 2 MHz chunks depending on what else they do upstream on the system, like interactive TV, phone service, video on demand, etc, all of which want this same upstream bandwidth. Do the math, not a lot of bandwidth for a node of 480 homes which is why upstream is so slow. Again, multiple channels can be allocated per node or system, but it is expensive.
Cost cost cost. Drives everything.
Analog TV starts at around 50 MHz (Ch 2) and runs typically to about 550 MHz, or around Channel 72 cable. Since upstream needs to use low frequencies to make best use or low power transmitters on the up stream side in cable boxes or cable modems, that limits upstream to the 5 MHz to 45 MHz area, and this is for ALL upstream in the system. Very limited. (If we could get rid of the analog tier on cable TV, the upstream limits on cable modems would probably go away as we could easily allocate another 100 MHz of upstream bandwidth.
When you turn on the modem, you will see it search for channels. It finds a downstream channel and the out of band communications channel, and then allocates a downstream channel, and then an upstream channel. When all three are locked and talking, only then will the modem be allowed to send/receive data. At the same time, the cable modem head end “router” checks the MAC address of the cable modem, and sometimes the MAC address of the connected computer to see if both are authorized users. If not, the system closes down, or in some cases, goes into low bandwidth set-up mode until properly authorized. Lots of places for failure here, but it is designed to keep retrying.
To work very well, the cable company should have upgraded the cable system to handle 750 MHz to 1 GHz of bandwidth, with a significant rebuild of most of the system to eliminate old, noisy parts of the cable plant. Typical failures are drops in the cable signal itself such as an amplifier along the cable dies, a coupler, a local node, etc. etc. Older systems which only did a partial upgrade (to save money) may be susceptible to things that add noise to the system, and thus cause the digital parts of the system to die. QAM and QPSK have significant error correction, but if the system gets to a noise level where there are not enough bits to correct any more, you get the “cliff effect” and basically, the system stops working all together. There is no partial working digital stream. Bad connectors, even in your own house can cause ingress of signal noise and the whole system can go down because of that.
Last failure at my house it seems the squirrels ate through the coax from the pole to the house, and that caused a great deal of noise to enter the system. I NEVER watch the cable TV part, so I did not notice the problem (all the channels were full of noise) because I use satellite for TV. This open exposed wire caused misc failures all the time and at random times. The comment from the tech, “…this should never have worked at all..” made me feel really good. Seems our designs at Pacific Bell, where most of Comcast’s designs came from as they bought the systems I worked on, worked well2
The cable modem head end system is a large router that is trying to manage a lot of things as well, and can crash or hang on one up or down card, or the entire device. Often, power cycling that device solves the problem.
Lastly, on the MYTH that cable modem bandwidth is “shared” while DSL is not, this is not entirely true. Yes, cable modem data bandwidth is shared in a node amongst all users. And yes, DSL is a dedicated line from the home to the central office and not shared, but that is not the entire story. Where all the DSL lines come together into a router at the Central Office, the bandwidth is shared across a single connection to the internet. In cable modems, all the nodes share a similar router and line to the internet, so they are shared too.
However, ALL lines in a central office share the internet connection, and the speed of the DSL line is fixed and cannot really get much faster. But in a large cable plant, cable modems can be placed around the system in what are called “mini-head ends” and each of these will have an internet connection. Additionally, which one cable modem channel is only 27 Mbps of bandwidth, if can be increased to 54 Mbps if two channels are used, 81 Mbps if 3 channels are used, so a cable modem line can easily be made faster with no line change. Not true in DSL.
And typically, if set up correctly, which 90% of them are, you plug in your modem, connect it to your computer, answer some initial questions, and it just works. In my experience, installing a cable modem is 100 times easier than a DSL line. And I do not have to put any filters on all my phones either!
End of brain dump on cable data.
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