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Author Topic: Comcast Cable modem info  (Read 4605 times)
newt
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Posts: 1132



« on: July 22, 2011, 08:25:27 am »

Hmmm... I was replying to a post from moe and it disappeared. I'll put my post here, though it's a little out of context now:

Quote
Hello guys, I need some help.

I currently subscribe to Comcast for my internet services @ home.  I have a cable modem from them, which I lease for $7/mo.  I'm looking to buy one so that I dont have to lease it from them.  My problem is that I know squat about cable modems.  If you go here http://mydeviceinfo.comcast.net/mydev.php?tier=2&h=0&d3=0&s=&so=&e=0&sc=368 and select the "Blast!" service under the "Residential Speed Tiers", that's what I have.  Basically, my speed is about 20mbit/s down and 4mbit/s up.

I'm lookin at the list of "Approved" modems on their page, and looking for those models online, but they seem a  bit high priced.  My question is... Are modems like routers where they all go by the same standard and you can safely pick just about any one and it's a matter of brand names and stuff... or... do I have a risk of not being able to use it if I dont buy one that's listed on their list?

I'd like to learn as much as I can before I make the purchase.
Thanks in advance guys.

For me this is a great topic because if I could stop leasing my modem from Comcast/Xfinity I would be super happy.

Here's my understanding of things (as of about 2 years ago):
-If you use Comcast's phone/landline telephony service then you may not be able to purchase your own hardware because I believe they will not register a telephony device that they do not provide themselves; not to mention they used to be hard to find for purchase. I've looked into this once in the past and my conclusions were that you HAVE TO use their telephony modem or no landline through them. It also seems they've "wrapped" the lease charge up into some other telephony service charge such that you'd still be paying the ~$7/month regardless of using their hardware or not. Since none of this was direct from Comcast's mouth I could very well be wrong on some of this.

-You'd want to most recent DOCSIS version (v3, I think) to allow for the fastest bandwidth.
-I do not think that off-brand devices would be a problem, but purchasing from a place with an open-box return policy may be in order.
-I used to use a personal Linksys docsis v2 cable modem with no problems, but when we upgraded to their telephony service I was stuck having to use their hardware.
-Yes, my understanding is that basic cable modems are like routers in that they're interchangeable. On the other hand, if the cable company uses some kind of proprietary connection protocol then you may be stuck with the ISP's hardware, but I do not believe this to be the case with Comcast. When it comes to cable modems (at least with comcast), they register the device on their end and they "control" the device (i.e. they do firmware and other related updated from their end at their wishing); the home users view of the modem configuration is read-only.

This may be the best place to look for information regarding your questions:
http://www.dslreports.com/forum/comcast

I've briefly just checked it out and am seeing that folks have the potential to buy their own triple-play (telephony) modems for a large cost from (at least) Best Buy - this is news to me. I guess you've sparked something for me to research again.
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M0E-lnx
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Vectorian
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Posts: 3185



« Reply #1 on: July 22, 2011, 09:03:14 am »

I dont know what happened there. Some mod must have deleted my post thinoling iylt was just another spam post.  But back to topic.  I do not use their telephone service. Just broadband and tv.  Thanks for that link i will look at it.  I guess what i need to find out is if the docsis version has anything to do with the speed capabilities of the device.  The v3.0 devices can be pricy so i need to really be sure.   Any more comments are welcome
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newt
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Posts: 1132



« Reply #2 on: July 22, 2011, 09:45:58 am »

wikipedias table relating to DOCSIS speeds indicates that DOCSIS versions definitely have a hand in maximum throughput speeds, particularly when comparing v1/2 to v3. V1/2 have a downstream maximum throughput of ~38 Mbit/sec, whereas V3 has a maximum throughput of upto 4x 38Mbit/sec (upto ~152Mbit/sec) depending on how many "channels" your ISP is using. Upstream throughput varies from 9mbit (v1), 27mbit (v2), and upto 4x 27mbit (v3). Granted, we likely won't be seeing those speeds anytime soon, but having a device that can support those should they become available would be nice. Of course, if you can pick up a v2 device for really cheap then it may well be worth snagging that now and worry about a v3 device when (and if) those speeds become available - they'd likely be less expensive at that point anyway.
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M0E-lnx
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Vectorian
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Posts: 3185



« Reply #3 on: July 22, 2011, 10:02:57 am »

Well, if the version 1/2 can do 38 Mbit/sec and my downstream is only 20Mbit/sec I should be fine though ... by that table?
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newt
Vectorian
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Posts: 1132



« Reply #4 on: July 22, 2011, 11:28:57 am »

I agree. It should be fine using a v2 based on that table; I think you'd be too close to the threshold of v1 for consideration. For confirmation it would be good to see an alternative source of information regarding throughput of v1, v2, and v3 just to make sure what's on wikipedia is reliable.

Edit:
This is an interesting read: http://forums.comcast.com/t5/Connectivity-and-Modem-Help/Comcast-Blast-Woes-PLEASE-READ/td-p/854491

Seems to indicate that although a v2 should reach those higher speeds, some folks have not seen those speeds until after a v3 upgrade. Then again, consider the source. I'll keep looking because this all intrigues me as well.
« Last Edit: July 22, 2011, 11:41:49 am by newt » Logged
M0E-lnx
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Vectorian
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Posts: 3185



« Reply #5 on: July 22, 2011, 12:02:59 pm »

I see.

I've asked forums you posted arlier.  They seem to confirm that DOCSYS is what I need to look at and that v2 should be enough, although not future proof.  See my thread here http://www.dslreports.com/forum/r26119268-Connectivity-Cable-modem-for-Blast-Service
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newt
Vectorian
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Posts: 1132



« Reply #6 on: July 22, 2011, 01:05:25 pm »

I like the rational that 'quatrix' uses. Save $ now since it won't matter, and by the time you need a v3 they should be significantly less $$.

Just for your info I use the comcast arris tm502g docsis v2 leased cable modem, and am on their normal tier for triple-play users (I think it's lower than blast). I just did a speed test via speedtest.comcast.net to Denver and got:
19.63 Mbps down
4.06 Mbps up

The results vary a bit by server location but they are generally no less than 18mbps down and 3mbps up. Nothing to complain about here except the 250gb cap (not that I've ever come close to it, just don't like the term "cap" Cheesy )
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M0E-lnx
Administrator
Vectorian
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Posts: 3185



« Reply #7 on: July 23, 2011, 07:59:25 pm »

I agree. However i went ahead and bought me a docsys 3.0 just to he safe.  I figured im about to start a 2yr agreement so by the time the first year goes around i would have paid for the modem in lease fees.  And when its over if i dont want it i can aleays sell it im sure.  I have yet to activate it but will do soon.  I did speak to comcast and the did fonfirm thqt the docsys version is the important part when buying these.  I bought the motorola sb6120 i think it is.   Thanks guys for sharing whatever you all onew about this.    I know i can always count on the vl community for tech advise.
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