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nasadude
join:2001-10-05
Rockville, MD | reply to heaphus
Re: Heh..
no | |
Nerdtalker
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1 edit | said by nasadude  :
no
That's somewhat an un-educated statement.
True, there isn't totally a tech-problem preventing any feasible Upstream upgrade, but there are still firm hurdles that need to be overcome.
I'd like to see an upstream speed upgrade, but from what I understand about the limitations of QPSK modulation (which can handle 2.3-4.6 Megabits of upstream depending on the width of the channel), the available upstream bandwidth seems to be the limiting technological factor regarding any upstream cap increase. 16QAM upstream modulation could be used, but it still doesn't provide a large upgrade in upstream bandwidth per channel, and it requires considerably cleaner signal.
As such, any upstream upgrade might possibly require an infrastructure upgrade. I'm not sure if Comcast is willing to spend the money just to deliver more upstream. I'd be willing to bet that's because they don't want to encourage:
• P2P usage
• Running Servers
• Making users more attractive as spam-boxes
I've been saying this for almost an entire year, we'd have more chance of finding a three-legged-ballerina than an upstream upgrade in the next year.
--
Touch a thistle timidly, and it pricks you; grasp it boldly, and its spines crumble. -William S. Halsey | |
DrTCP
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Round Rock, TX
| said by Nerdtalker :
16QAM upstream modulation could be used, but it still doesn't provide a large upgrade in upstream bandwidth per channel, and it requires considerably cleaner signal.
DOCSIS 2.0 adds QAM64 modulation and almost doubles the channel bandwidth to provide up to 30Mbps. The dirtiness of the upstream channel frequencies are taken care of by using new encodings and ECC schemes.
quote:
As such, any upstream upgrade might possibly require an infrastructure upgrade.
Cable companies including Comcast has done the upgrades already. The infrastructure is ready... | |
Yeahwhatever
@66.20.x.x
| reply to Nerdtalker
That is true, but more so than that, a common problem is still affecting cable. With the increase of just plain ol' use of the current upstream has jumped the proc usage on the routers in the OTNs to 70-90% usage! Making a split on the upstream a must just to maintain current standards. There ofcourse are plenty of ways around this; but a hurdle non the least! The problem with high % you ask? with all the load on the proc from upstream causes it to drop downstream packets just to keep up. This is just one problem that I have come accross while working for comcast.
But I too would rather have slower downstreams than current in replace of higher upstreams! | |
Nerdtalker
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| reply to DrTCP
said by DrTCP :
said by Nerdtalker :
16QAM upstream modulation could be used, but it still doesn't provide a large upgrade in upstream bandwidth per channel, and it requires considerably cleaner signal.
DOCSIS 2.0 adds QAM64 modulation and almost doubles the channel bandwidth to provide up to 30Mbps. The dirtiness of the upstream channel frequencies are taken care of by using new encodings and ECC schemes.
quote:
As such, any upstream upgrade might possibly require an infrastructure upgrade.
Cable companies including Comcast has done the upgrades already. The infrastructure is ready...
DOCSIS 2.0 is a viable solution, but its still too far off.
Comcast for one has only just begun upgrading to DOCSIS 1.1, and the majority of modems and linecards are still DOCSIS 1.x. My point still stands, they'd need to replace all of that, and what'd the only benefit be, so that the 5% of power users can P2P, host files/webpages, and use a webcam? From a business point of view, its simply not worth the time or money at this point.
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pcscdma
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| said by Nerdtalker :
DOCSIS 2.0 is a viable solution, but its still too far off.
Comcast for one has only just begun upgrading to DOCSIS 1.1, and the majority of modems and linecards are still DOCSIS 1.x. My point still stands, they'd need to replace all of that, and what'd the only benefit be, so that the 5% of power users can P2P, host files/webpages, and use a webcam? From a business point of view, its simply not worth the time or money at this point.
There are ways to use multiple upstream and downstream channels on a cable segment. DOCSIS 2.0 allows a more efficient upstream modulation using only slighly more bandwidth to get the maximum 30mb upstream data rate it provides. This also allows them to better manage node saturation with multiple upstreams. Here is somewhat of an analogy(?) or at least something to explain. Imagine the T1 being one of a few lo-speed upload channels (only one can be used at a time) and the T3 being just one hi-speed upload channel. It also can be somewhat informative to certain people from the example I purposely have chosen. The ISP in the example has a topology that does not connect any T1s together and uses one of it's T1s for a certain group of customers.
A T1 can do 1.54Mbps and that's it. A small ISP can sell 6 256/256kbps connections and never fully saturate the connection. Since BBR people are cheap ba$tard$ and refuse to pay the $100+ price for a measly 256/256, the ISPs decide to oversell the connection and hope that the customers don't notice this. This means that the ISP cannot continue to sell 256/256 to new customers using the same T1. They would start to call in and complain about how stupid it was to have your oversell ratio all fsked up.
So instead of having a few T1s that have to be managed so each segment's bandwidth is sufficient, a T3 is used and usually can be oversold using a slightly higher ratio than a lower speed connection. If one T1 was quiet with nobody using it and another one was saturated, the bandwidth could not be taken away from the other T1 to make up for the saturated one. This can be very inefficient for bandwith and money, and the ISP could get upset subscribers.
Since when were 'power users' the only people who use webcams? The Moto SB5100 is DOCSIS 2.0
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Nerdtalker
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| said by pcscdma :
said by Nerdtalker :
DOCSIS 2.0 is a viable solution, but its still too far off.
Comcast for one has only just begun upgrading to DOCSIS 1.1, and the majority of modems and linecards are still DOCSIS 1.x. My point still stands, they'd need to replace all of that, and what'd the only benefit be, so that the 5% of power users can P2P, host files/webpages, and use a webcam? From a business point of view, its simply not worth the time or money at this point.
Since when were 'power users' the only people who use webcams? The Moto SB5100 is DOCSIS 2.0
Since most of the non power users are just beginning to understand how to even connect the webcam...
You fail to understand why we aren't seeing DOCSIS 2.0 being phased in. Modems are available, but linecards and new CMTS equipment is costly.
Think about it from a business point of view, why would increasing upstream make your service more appealing to average Joe? He doesn't share files, run a webpage, or use a webcam, he only "surfs the net".
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Touch a thistle timidly, and it pricks you; grasp it boldly, and its spines crumble. -William S. Halsey | |
DrTCP
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Round Rock, TX
| said by Nerdtalker :
You fail to understand why we aren't seeing DOCSIS 2.0 being phased in. Modems are available, but linecards and new CMTS equipment is costly.
First of all, most CMTS manufacturers now have DOCSIS 2.0 line card upgrades. ISP does not need to upgrade to DOCSIS 2.0 everywhere. Cisco is the dominant player in CMTS business and they started selling DOCSIS 2.0 CMTS last year.
Secondly, you only need to upgrade those systems where total upstream utilization at any one instant is likely to exceed 10Mbps (DOCSIS 1.0/1.1). But there are other solutions you can choose before DOCSIS 2.0 path. DOCSIS 1.0/1.1 systems can allocate multiple upstreams per one downstream channel (typically a CMTS card is 4up:1down). So, CMTS can loadbalance modems to one of the 4 upstream channels even though they all use the same downstream channel (beauty of DOCSIS scalable design).
If the modems are capped to T1 this is not going to cause any problems to the user.
The advantage of DOCSIS 2.0 is that it allows better upstream frequency usage (efficient use of spectrum) for the Cable ISP. It is not really a problem for the user. DOCSIS 2.0 and DOCSIS 1.1 use the same MAC code so the difference is basically on the physical layer. | |
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