| How's does it all really work? 25 users per node and each node providing 38 megbits?
Is this up and down? or 38 for download? is there a different scheme? |
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 SOLdesignDid I drink a shot of Irrational Whore?Premium
join:2002-07-29
Woodland Hills, CA | where do you get 25 users per node? did someone give you those figures?
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-I need a beer. Soon. |
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 EagleMasterPeople Need A Life Other Than InternetPremium,MVM
join:2003-02-10
Glen Richey, PA | reply to justice1776
Kinda wondering that myself. |
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 MacLeechThe one and onlyPremium
join:2001-07-14
SoCal
kudos:3
| reply to justice1776
said by justice1776:
25 users per node...
The number of users per node depends on subscription rate, number of homes passed per node, and general system design architecture. Homes passed per node can be anywhere from 100-2000 and subscription rate depends on competition, marketing, and system performance. Most cable companies design for 10-25% subscription rates for cable modem customers.
So this means anywhere from 10-500 modem customers per node depending on system architecture in most cases.
said by justice1776:
...and each node providing 38 megbits?
Is this up and down? or 38 for download?
The bandwidth limits are not technically per node, they are per port on the CMTS. Ports is this case refer to the physical connections on the CMTS (modem controller in the cable office headend) in which 1 or several nodes can connect to. Number of ports on a CMTS can vary widely depending on manufacturer and design, but normally for every downstream port there are 4-8 upstream ports.
As far as bandwidth, DOCSIS 1.0, 1.1, & 2.0 can do a little less than 30 mbps per downstream port using QAM 64 modulation and about 38 mbps using QAM 256 modulation. Upstream is limited to about 5 mbps per upstream port using DOCSIS 1.0, 10 mbps using DOCSIS 1.1, and 30 mbps using DOCSIS 2.0.
Altogether, this means anywhere from 10-1000 customers might be sharing the bandwidth of 1 pair of ports (keep in mind every node connects to at least 1 downstream port and 1 upstream port) and a single CMTS might serve 10 to 20,000 customers.
Obviously more customers per port per CMTS is more cost effective, but pushing it too far can cause bandwidth overload.
Try this article, its older but gives a good feel for the situation:
»www.spectrum.ieee.org/WEBONLY/pu···ode.html
Here's a few good sites for an overall explanation:
»computer.howstuffworks.com/cable-modem.htm
»cable-modems.org/tutorial/
»cabledatacomnews.com/cmic/
For a technical description of what a modem does to get online:
»www.scte.org/chapters/cascade/DO···il_2.pdf
Here's an ACLU comissioned report on open access which details how cable systems work in the appendix:
»www.aclu.org/Files/getFile.cfm?id=10520
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Adelphia SoCal, Cable modem manual (PDF), CATV Broadband Training Online
[text was edited by author 2003-04-19 16:35:33] |
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SOLdesignDid I drink a shot of Irrational Whore?Premium
join:2002-07-29
Woodland Hills, CA | niiiiiiiice! Mac rocks
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-I need a beer. Soon. |
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EagleMasterPeople Need A Life Other Than InternetPremium,MVM
join:2003-02-10
Glen Richey, PA | reply to justice1776
Mac is da man of all men for that stuff.
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SOLdesign and Hobgoblin in a barrel. |
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 RR ConductorNWP RR Inc.,serving NW CAPremium
join:2002-04-02
Redwood Valley, CA
kudos:1 | reply to MacLeech
Thanks for all the info Mac! That diagram would need to be adjusted for our area though, we only have one headend, and that's the one in Ukiah. The Ukiah headend serves the entire county of Mendocino(Ukiah, Willits, Redwood Valley, Calpella, Fort Bragg, Little River, Mendocino, Albion, Caspar), and is both a local and regional one, did I get all that right Mac?
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Find the true meaning of Easter, »www.lds.org/library/display/0,49···,00.html |
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keo ekeRazorbackPremium
join:2002-11-20
Georgia | reply to justice1776
I only see ONE headend in Mac's diagram and 4 hub sites. |
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RR ConductorNWP RR Inc.,serving NW CAPremium
join:2002-04-02
Redwood Valley, CA
kudos:1
| Here we go again lol
[text was edited by author 2003-04-19 22:06:42] |
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MacLeechThe one and onlyPremium
join:2001-07-14
SoCal
kudos:3 | reply to keo eke
said by keo eke:
I only see ONE headend in Mac's diagram and 4 hub sites.
The diagram is a very general representation of an HFC (read type needed for DOCSIS modems to work) network. Its not specific to any one cable company or area. Nothing I posted earlier is specific to any Adelphia system.
Its all very general "How cable modem networks work" type stuff.
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Adelphia SoCal, Cable modem manual (PDF), CATV Broadband Training Online |
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 swcoxAdelphia High Speed InternetPremium
join:2001-11-21
Greeneville, TN | Yeah, we're slightly different here than that diagram...
We have one headend, feeding over 700 nodes. Each node feeds one active. It's called "Node Plus One" architecture. You don't have all those cascading amps to worry with!
(we don't miss the cascades at all!)
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Policy is often cited to avoid responsibility and decision-making. |
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 Crazyf00LGlorified Version of a Pellet Gun
join:2002-11-04
Coudersport, PA | reply to justice1776
We discuss this a lot in the TAC about the wide variety of equipment and the way the network actually works...there are lots of different types of equipment working together almost as one...it is quite amazing if you think about it...
But most people don't even have the beginning of a clue..they just know if it works or not.
Looks like we will be hitting 800,000 customers here some time soon...That's quite an event for a company that is bankrupt I would say. Someone is going to eventually have to admit that Adelphia has come a long way in the past 3 months... |
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RR ConductorNWP RR Inc.,serving NW CAPremium
join:2002-04-02
Redwood Valley, CA
kudos:1 | Their Powerlink has come a long ways, but their digital cable(at least here in Nor Cal)has a long, long ways to go to even be comparable to satellite in choice and quality.
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Find the true meaning of Easter, »www.lds.org/library/display/0,49···,00.html |
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| Funny you should mention that bro.
I've been wondering with all the upgrades and seeing the excessive amounts of new bandwidth being added.. what could all that extra bandwidth be for?
Maybe VOIP? VOD?
I'm sure there a lot more upgrades going on with the Digital TV system as there are with Powerlink.
Sincerly
Jax |
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Meeble
join:2002-09-19
Champaign, IL | said by JacksGhost:
Maybe VOIP? VOD?
I'd settle for being able to play a game now and again with less than 150 ping and having my digital cable stations come in under less than 15 seconds before I'd have a need for VOIP 
on the digital cable side - anyone else encounter this. we had like 5 ppv stations removed to add the 'adult' stations back in our lineup and ever since then I noticed that 3 of the ppv stations left always have a 'No Event Scheduled' 24/7. Just curious if everyone sees this now and if maybe they have no events because they are being allocated to something else instead of ppv movies soon? |
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