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Cable modems: Which one?

Posted on 2001-08-01
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Last Modified: 2007-12-19
By buying my own cable modem, I save $10 a month. But -- which one? There are many to choose from and I can't find any hint as to why I might prefer one or another.

- @Home has a list of approved units. Do I have to stick to this list? In particular, I saw a good deal on a 3Com 3CR29210 but they only approve the 3CR29223.

- Looked at ebay and there are many, but I wonder if any are better than another? Are they like 56K modems -- a commodity, one pretty much as good as another? Or is there a spec I should know about?

I am using AT&T @Home in Santa Clara, CA, is that matters, and the device they furnished is an RCA DCM205. Which, interestingly, is not on their approved list!
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Question by:MRubenzahl
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by:Dufo G. Belski
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I've got AT&T also, it was called Roadrunner when I got it.  I have a 3Com which works quite well.  But consider, they cost about $200.  That's 2 and a half years.  Will you still be using a cable modem in 2 and a half years, or be on to some new technology?  That's why I did not buy one.
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by:RoadWarrior
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They are planning to upgrade the line speeds in the near future, next year or so, so if that comes your way before you've paid for the modem, you're stuck with a white elephant. Also my experiences with @home tech support indicate that you are better off having more equipment you can "blame them" for rather  than less.
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by:magarity
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I have to agree with not buying one.  I got cable modem about a year ago and looked over all the options.  I finally decided that renting the thing is a much better idea.
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by:pbessman
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If you insist on buying your own make sure it is DOCSIS compliant.  If it is not you are probably going to be out of luck.  You do have to pretty much stick with whats on their list, but for ease of installation you should really call 888-462-6300 and ask them which ones are supported in your area.

I set up customers with their own modems from time to time and was a contractor as well as an employee of @home for the last 3 years.  I would not suggest that you buy it before consulting with them.  The process of getting yours to work requires for them to be able to log it into their inventory(IT IS STILL YOUR MODEM), they do this in order to set up the router to expect your modem on the system.  If they did not do this people would be stealing cable internet service and this way they can monitor and make adjustments when needed.  If all it took was to hook the modem up there is the possibility that nodes would become flooded.
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by:pbessman
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I think the 29210 is an older modem.  We actually used those to test the lines in some places.  But, for reasons which I do not know, they never made them available to customers.
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by:magarity
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A day in the future of MRubenzahl
This is a True Story (tm):

6:00 PM:  ATT's system is acting funny.

8:30 PM:  MRubenzahl gets off hold and them up to tell them to fix it.

8:31 PM:  ATT phone answering monkey says 'Your account shows that you bought your own cable modem.  Call its manufacturer since the problem must be with it and not our system.  Thankyou for using ATT.' >click<

Next Week:  Another customer on MRubenzahl's subnet has the same problem, but since she leased instead of buying, the problem is eventually traced to the nearest router which is reset and MRubenzahl's connection is finally restored.
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by:pbessman
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That's not so, I have been on several trouble calls that were related to the cable side of the install.  The only thing they won't do is replace a crapped out customer owned modem.  If the customer had us install the network card and paid for the install we would make trouble calls for all issues.  IF the customer opted for a self install and leased their modem we would use one of our modems to verify send and receive from customers home.  Unless the full installation is paid for we will not touch a customers computer until they pay for the service call.  If the service call is paid for and the issue is resolved and determined to be a cable issue the monies are generally refunded.
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by:magarity
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"That's not so"

Maybe, maybe not.  But it *is* comical, if I do say so myself...
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by:pbessman
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"ATT phone answering monkey"  I used to be one of those monkeys.  I know it was before we had so many subscribers, hech when I left there we had just gotten our 100,000 customer.  They are way beyond that now.

Sure it's funny but they are still required to run all of the tests that they would perform to make sure it was not a setup issue.  If people take the time to learn about their computers AT&T does offer unlimited phone service to resolve issues, whether they do the install or not.  It is when the issue is that of a non pingable modem that we would be sent to the house, we would hook up one of these 3CR29210 test modems I spoke of earlier and  if we established block synch with it behind the computer we would leave.  If the customer had paid the extra 50.00 for an install or for the trouble call we would even do diagnostics on the modem.  By the way if you did not pay for the install this is a one time charge, at least it used to be and that entitled the subscfriber to full support.  If we can determine it is a modem issue we would then advice the subscriber to get a new one from their vendor.  That is another reason why it is best to go with "SUPPORTED" modems.  I have always had a leased modem as there has been some talk of added bandwidth and currently the modems that are offered for sale limit the speed.  If you read about these modems you will see that it is the modem that throttles the speeds that used to be about twice to three times as fast.  This concept actually started two years ago and in one community in Washington State, all customers were required to purchase their own modems and they were to obtain them from our participating CompUSA store.  These modems by the way were inventoried and had all the necessary info in @Homes database to make for a smooth install.
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by:magarity
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OK, OK!  You were the 1 in 100 tech support call center person who actually knew anything.  It's just that the last time I called because I could ping my ATT gateway's IP but no farther outwards on the 'net I was told to check that my cable modem was plugged in properly and try rebooting my machine.  Ugh.  And I certainly know better than to admit there's a linux machine doing firewall duty here...  "We don't support Linux.  Thankyou for using ATT" >click<
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by:RoadWarrior
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My experiences with @home support droids are similar, though not with ATT@home.
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by:MRubenzahl
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This has certainly been an interesting read. I have concluded from your reponses that I will stay with the leased arrangement and thank you all for your reasons.

Comments have been useful but no one has answered the questions I asked. AT&T @Home answered one: They confirmed that they 3Com 3CR29210 is not an approved unit. So it stay's on Fry's (local retailer) shelves.

Anyone have an answer to:

  > I wonder if any are better than another? Are they
  > like 56K modems -- a commodity, one pretty much
  > as good as another? Or is there a spec I should
  > know about?

Is there any reason I should ask that they upgrade me from my RCA DCM205? Is it as good as any? I heard there are differences but no one has been able to explain what those are and the boxes at Fry's provide no enlightenment.

Will also add my two cents, FWIW: I have found AT&T Support to be OK. About half their answers are useless -- some mind-bogglingly so (at least once, I sent back an message asking, DID YOU -READ- MY QUESTION???) but eventually, I have always gotten the right answer.
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by:magarity
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"a commodity, one pretty much as good as another?"

I read a ZDLabs test of several different models back when I was looking into buying.  I'll see if I can find the link.
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by:pbessman
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"RCA DCM205"  Do you have the box? If you have the box please tell us what downstream bandwidth this modem supports.  They are supposed to leave the box with the modem.  Check for a CD in the box, not the @home CD but an RCA CD has some really cool software on it.  This is one of my favorites actually.  In some places you can buy these.

And I certainly know better than to admit there's a linux machine doing firewall duty here...
 "We don't support Linux.  Thankyou for using ATT" They are supposed to ask if you have a Windows or Mac OS machine to work with.  I have yet to see the Mac OS X most of the machines we get are PC based.  I remember talk about Mac incorporating Linux into their systems.  Has this been done?

I actually got into a lot of trouble giving advice to people who were using unsupported software.  I am sure you can understand that Linux is an OS that is so customizable that offering support to all Kernels would be a royal pain. People insisting on running static with their ip masquerading boxes.  I set mine up DHCP. Actually, having read all of the Red Hat help pages on @Home with DHCP I find that out of 45 pages of text there are about 44 1/2 wasted pages.  There is one way that works really well.
 Anyway, when I was working for them directly I used a router as they only gave employees one IP address.  Believe it or not, I helped set up a few high level AT&T people and they only get one as well so we used these router firewall boxes.  I am currently doing that so I can run several OSs and experiment without having to configure the LAN.  
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by:pbessman
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BTW I am pretty sure that all of the RCA modems are supported.  At least I know we have used about four different kinds in installs.  I also know that their older models were software upgradeable and that allowed them to stay in cuctomers homes without needing to be replaced.  In one area we went to a few customers a day and swapped out their modems.  RCA makes probably the smallest cable modem.
  Here is info on the RCA 235R.  I have installed some of these and they are available from RCA directly for about 250. http://www.rca.com/product/viewproductcategory/0,2590,CI4,00.html? These are nice units.
Product Features:   CableLabs Certified
 Speed: Supports two-way cable transmission rates of up to 38 Mbps downstream and 10 Mbps upstream. Computer connection via the Ethernet 10/100Base-T with auto sensing or USB.
  Convenience: Offers an always-on, "ready-when-you-are" unlimited Internet access to online multimedia services.
  Security: Supports BPI+ communications privacy to support secure data exchange between modems and cable operators servers.
  Multiple Users: A single DCM235 can support up to 32 computers via the 10Base-T or 100Base-T Ethernet connection (Additional equipment required.)*
  Compatibility/Portability: The DCM235 is DOCSIS-compliant and CableLabs Certified, which ensures interoperability with all DOCSIS configured cable plants throughout North America.
  USB connection for plug and play connectivity.
  Compatible with PCs with Pentium equivalent or better, and Macintosh 601 or higher.
  Confirm service availability and access fees with your cable provider before purchasing.
  Product Dimensions:
5 4/5" H x 2 7/25" D x 6" W

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by:mikefromcarson
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I got lost of what you are saying here. hmmmm... MRubenzahl is just asking of which modem is best and you're talking about multiple users and etc... sorry i dont want to be mean or anything but i dont get the point of what you are talking about...

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by:magarity
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I assume mike is confused about:
"Multiple Users: A single DCM235 can support up to 32 computers via the 10Base-T or 100Base-T Ethernet  connection (Additional equipment required.)*"

This spec is actually important to some people because it means that if you rent multiple IPs rather than using some sort of connection sharing scheme, the one cable modem in question can handle up to 32 IPs in your house.  Other models will have more or less capabilities to do this.  

Whether mrubenzahl needs this capability, we don't know, but just because mike doesn't understand the various features of cable modems is no reason for him to make a lame attempt at belittling pbessman.

mrubenzahl,
I can't find that zdlabs article I mentioned above.  They only tested three models, a 3COM, a Sony, and some other brand.  The 3COM won, as I recall.  Don't recall the model number, though...
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pbessman earned 100 total points
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3Com has a pretty good QC program.  For the most part from what I have seen they are "just a commodity" however, the 3com modems, as any product I have seen from 3Com are probably the most reliable.  I remember at one point long ago getting a bad batch of RCA modems out in the field.  They weren't physically defective, but somehow the modems were not identified correctly which messed up provisioning a bit for us.(The boxes are supposed to be tagged with the serial number and MAC address of the modem.  The serial numbers matched but the MAC addresses didn't.  Making this a human input error, rather than bad parts.)  The 3Coms are also probably a "better match" for the equipment as they seem to have upstream and downstream limits similar to that of the routers they are "talking" to over the cable.  Like a phone modem may have better performance if it can match the speeds of the equipment it is dealing with sometimes less is more.  For example, an ordinary phone modem may seem to be "quicker" if it is set to operate a notch below full throttle.
     I have never actually seen a "Sony" modem but it does not surprise me that they have made their way into this technology.  I just checked on Sony's website and it appears that they had a cable modem but their last archive was a news release that they would begin testing to meet the Cable Labs Certification that would be required to be DOCSIS(Data Over Cable Systems/Interoperability Specifications).  It is dated May 3, 1998.  Nothing since.

Thanks Magarity.  I appreciate the fact you are watching out for my back.

Anyway, as far as networking goes these RCA modems seem to be able to pull a lot more bandwidth than some of the others.  If a customer has subscribed to more than one IP(the limit is 5 by the way)they can seamlessly share this modem without it becoming a bottleneck a it can handle the bandwidth necessary for multiple users to share the connection.  It is also the only one that I know of that will talk to a 10/100 hub or switch at 100 rather than 10.  Most of these modems will only have a 10mb port for connection to your LAN and if your hub is a 100 rather than a 10/100 you would be out of luck as mixing those two connections does not work well.  Different 802.x protocols.

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by:magarity
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pbessman,  since you used to work at att cable, maybe you can tell me: why the heck does this cable modem's activity light sometimes run a lot even if my computer is off?
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by:MJMeucci
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there is a company named 2-Wire and they have a great cable modem that has a built in switch and firewall.  Check out their site.

www.2wire.com
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by:pbessman
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Some of the activity is testing from the cable company or even the modem itself checking its software and possibly checking to renew leases for IPs.  Other activity can be caused by viruses.  See this page for info on CODE RED Virus variations:  http://home-help.excite.com/mainpage/coderedvirus.html

If you are concerned power the modem off for a few seconds and power it back on.  Sometimes weak signals cause this activity.
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