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[Ars] Meet DOCSIS Part 1 and 2

3K views 58 replies 28 participants last post by  mksteez 
#1 ·
Part 1

Quote:


The ideal way to build a national broadband network for access to the Internet would be with a high-bandwidth, bidirectional cable running to each individual household. But sometimes you have to work with what you've got, and in America, what we have are cable TV networks. These networks have the bandwidth, but not the bi-directional partâ€"they weren’t originally intended for two-way communication. Worse, the cables for many neighbors all connect together, so it's not possible to send a signal to just one household. And yet, cable companies manage to provide 100 Mbps bandwidth to their broadband customers using this flawed infrastructure, and they do it without compromising the preexisting cable TV service. The tech behind this magic trick goes by the name of DOCSIS, which stands for Data Over Cable Service Interface Specifications.

Part 2

Quote:


DOCSIS 3.0 gets around these limits using brute force: it bundles multiple channels. By using multiple channels at the same time for the same data stream, the data stream can be bigger than the bandwidth that a single channel allows. By default, in the downstream direction, the CMTS will send individual packets over different channels, but each packet is labeled with a sequence number so if packets arrive out of order, they can be put back into their original order before they’re given to the user. The Internet Protocol (IP) explicitly allows for out-of-order arrival of packetsâ€"but if this happens routinely, it does slow down transfers. Alternatively, the CMTS can use different channels for different types of communication, where each channel has its own interleave level that is appropriate for the type of traffic flowing over that channel

I think it's a pretty good read since I'm basically clueless when it comes to networking.
 
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#7 ·
Quote:
Originally Posted by dizzy4;13613619
My ISP is implementing DOCSIS 3.0 soon! I got a 3.0 modem to take advantage.
Mine already has DOCSIS 3.0 since ages ago but no (well priced residential) plans out to fully take advantage of it as of yet :/ On 15 m/bit 2 down but expensive. The best on my ISP is 25 m/bit down, 2 up. Unis and business plans easily go up to 100 m/bit +
 
#9 ·
I guess we're 3.0 here. The modem I got is D3.0 and Gigabit for over a year now. Suppose to get 18/2 but with speed boost speedtest.net usual gives 50-60Mbps down, sometimes more. Channel bonding FTW!

Our highest residential is 60/5 tho and has been for over a year.....just don't want to shell out $100/m when 18/2 is plenty for $40/m.
 
#10 ·
Quote:
Originally Posted by Velcrowchickensoup;13614855
Moving soon. Sacramento. Probably going to pull the trigger on Comcast Extreme 50.
What's the cap on that, if any?
Quote:
Originally Posted by Lxcivic2k1;13614896

Our highest residential is 60/5 tho and has been for over a year.....just don't want to shell out $100/m when 18/2 is plenty for $40/m.
18/2 for $40 is awesome, I'm paying $50 for 15/1.
 
#13 ·
Quote:
Originally Posted by skatingrocker17;13615138
No cap here either, I just thought almost everyone on Comcast had caps.
Huh? That doesn't sound right, they publicized a 250GB/month combined up/down cap a few years ago for all residential plans; I figured they'd carry it over to the DOCSIS 3.0-based speed tiers.
 
#15 ·
due to this thread, i just checked and they have DOCSIS 3.0 rolled out in my area
smile.gif

much has changed in the past year in our networks i guess lol... i haven't been paying attention

anyways, this is exciting for me, because ima be able to get a nice 50 or 105 mbit/down line

all of this is semi off topic. sorry.
 
#20 ·
I'm running 20/4 internet from Comcast, DOCSIS 3.0 and I get 30/4 consistent. Also, from my Comcast tech that installed, he said that speeds were planned to double at no additional cost within the next year to two because of the capability of DOCSIS 3.0. I'll gladly take 40/8 internet for same price.

I just wish the upstreams were larger. In the good old days, when cable modems were first being rolled out, my family was enrolled in the initial tests by Adelphia Cable in the Massachusetts areas, and it was crazy bandwidth at the time, and the upload speeds matched download because basically no one had it
biggrin.gif
 
#21 ·
Quote:
Originally Posted by DaClownie;13615609
I'm running 20/4 internet from Comcast, DOCSIS 3.0 and I get 30/4 consistent. Also, from my Comcast tech that installed, he said that speeds were planned to double at no additional cost within the next year to two because of the capability of DOCSIS 3.0. I'll gladly take 40/8 internet for same price.

I just wish the upstreams were larger. In the good old days, when cable modems were first being rolled out, my family was enrolled in the initial tests by Adelphia Cable in the Massachusetts areas, and it was crazy bandwidth at the time, and the upload speeds matched download because basically no one had it
biggrin.gif
how much are you paying for it?
 
#22 ·
Quote:
Originally Posted by Dream Killer;13615698
how much are you paying for it?
Uhh... I do the double play... so its like $70 for digital non-HD TV and their basic speed internet... $15 extra for the speed I run...

All said and done, I have 1 DVR box, 1 HD box, 1 DTA for a kid's room, 20/4 internet, and with taxes and fees I pay $126 a month.
 
#24 ·
Quote:
Originally Posted by labbu63;13615858
well i guess this is good news right? but a quick question what is the ping for cable usually?
When I run speedtest.net its usually in the 12-18ms range for the nearest location.
 
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