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BiggA

join:2005-11-23
EARTH
reply to misfits138

Re: Just curious

They have to have the capacity to do it before just hitting the button. Theoretically, they could uncap the connection, and D2 modems would run at 38mbps, D3 at 38mbps per channel they can bond, but in reality, if they did that, you'd get the full speed at like 3 in the morning, but during prime usage times the whole network would slow down to a crawl.

They could add capacity by splitting nodes and/or adding more D3 channels. The fiber to the node usually has much more than the coax is set up for.


cramer
Premium
join:2007-04-10
Raleigh, NC
kudos:9

Actually, that check too is a simple click of a mouse. (or in every NOC I've ever worked... just look up at the traffic graph on the big screen.)

To answer the OP... Yes. It's a number in a config file. It's an "upgrade" they've performed many times over the last decade plus... 3 to 5 to 6 to 7 to 8, then then D3 upgrades lead to 10, and now 15.

(PS: all ISPs over subscribe their network. TWC is no different, and this will not deter them from upping the advertised speeds. Look around the internet and you'll find plenty of accounts of people not getting the advertised speed.)


rradina

join:2000-08-08
Chesterfield, MO
reply to BiggA

Regarding FTTN -- do we still think cable's current limits are the last mile coax? Obviously this depends on how well the cable plant has been managed but I suspect unleashing DOCSIS limits would obliterate their backbone to the Internet well before straining the last-mile coax.

The reason I suspect this is that most cable companies continue to increase speed on a steady pace. Are they really continuing to push fiber deeper and deeper into their networks or within the past few years have they reached "far enough" to where nodes are small enough to have plenty of bandwidth? (Perhaps not to deliver 1Gpbs but certainly 15Mbps and probably 38Mbps wouldn't create a crisis.)

In my area, Charter still provides 60 or 70 analog channels. Considering each uses 6mhz + guard bands, that's close to 500mhz of capacity just ready to be reclaimed! They also stream those same channels in SD digital along with lots of HD, VOD and 100Mbps HSI. Recent ratings show them having no problem delivering all of this during peak periods.

What still makes no sense to me is the CAPs. Surely it's no longer about concurrent user experience. Cable speeds are such that even extreme users would have difficulty maxing out their connections doing anything related to a typical consumer -- even if they watched constant NetFlix streams.



mikedz4

join:2003-04-14
Weirton, WV
reply to BiggA

Isn't that how @home worked before they tried to merge with excite and went the way of the dodo bird?


BiggA

join:2005-11-23
EARTH
reply to rradina

The technological limits are 100% the last-mile. Fiber, when set up correctly, has massive capacity way beyond that of DOCSIS. Of course that's not to say that there aren't systems out there with shiny new D3 gear running on older fiber backhaul that are backhaul limited. AT&T's shiny new 3G network was backhaul limited for years before they saturated the air interfaces with gig IP-RAN for fake 4G.

They have had to push fiber father out not just for internet, but also for VOD, which uses QAM channels. Comcast here has gotten rid of analog, and shortly thereafter, they added more HD VOD content, more HD channels, and more internet speed.

The caps aren't effective at what they need to do, which is manage peak traffic on the last-mile. However, they don't really know how to do better, and the investors of course push for monetization. I think the best solution would be to go back to "don't abuse it but we don't have a set cap" but don't kick the abusers off, just shape and throttle them during peak usage, and then let them hit it hard at 3 in the morning.


rradina

join:2000-08-08
Chesterfield, MO

Please read what I said again. I questioned "backbone to the Internet". I understand that relative to wires, fiber bandwidth is unlimited. From that perspective, yes, all the "technological" limitations are in the wire plant, not the fiber plant. However, my question doesn't have anything to do with comparing fiber with wires. I'm asking whether or not major cable players have at least reached a temporary equilibrium where a last-mile coax node is sufficiently small as to no longer represent a major limiting factor. Furthermore, if they eliminated DOCIS speeds, the aggregate bandwidth would combine and be limited by their Internet drains rather than their coax plant.

The reason I ask is because over the last several years I've witnessed a relentless march by cable providers to ever faster base speeds. I can remember when my package was 3Mbps, then 8Mbps, then 12Mbps and then 15Mbps. Although I'm currently stuck with a multi-year fixed-price deal, the base is now 30Mbps! All of these increases seem to have had no impact on peak performance and it makes me wonder how they do this and keep ~70 analog channels. It seems impossible unless their coax nodes are so small that the coax segment, at least for the moment, isn't limiting their capabilities.


BiggA

join:2005-11-23
EARTH

Very little of the relative bandwidth on a plant is for DOCSIS. 3-5% would be typical.

It's really hard to know if they have enough backbone capacity. But we do know it's easy to add. Just add more fiber.


rradina

join:2000-08-08
Chesterfield, MO

Yes, easier than replacing coax with fiber but how cost prohibitive is it? Does removing DOCSIS speed limits mean they have to double or triple their capacity to the Internet (i.e. add capacity from their upstream providers -- Verizon, Qwest, AT&T, Level3, C&W etc.) or in other cases, their own existing fiber WANs that feed traffic to a major Internet access cities (NYC, WDC, CHI, SF, etc.)

For instance, Charter in St. Louis appears to have built its own private WAN between STL and KC so it can serve other plants they own in the state and connect with Qwest in KC. It also appears that they have built their own WAN between STL and Chicago to trade traffic in that major hub. Although St. Louis is well connected and Charter used ATT several years ago, it appears they have bypassed local interconnects in favor of trading a lot of traffic in Chicago. I can only guess they invested considerable capital in building these links and I wonder if the constraint is now managing the capacity of these links if they were to remove DOCSIS governors.


BiggA

join:2005-11-23
EARTH

I don't think there is any way to reliably run an uncapped system. One user could use up all the bandwidth on it.

Fiber is expensive, and while telcos have to do it, or else fail (U-Verse), because copper pair wire has so little bandwidth left in it, cable operators don't, as they would be much wiser to push 8-channel bonding, new versions of DOCSIS, 1ghz plants, SDV, and all-digital before they need a new medium to deliver their service.

The constraints on DOCSIS are all in the RF plant. Backhaul is easy to add. They can, and will, add DOCSIS speed and capacity as competition makes it necessary (as it has with FIOS).

The takeaway is that Comcast is much more comfortable pushing more bandwidth, more channels of DOCSIS, and more fiber farther out into the last mile than they are competing with price, and they want to keep it that way.


rradina

join:2000-08-08
Chesterfield, MO

".. no reliable way to run an uncapped system. One user could use up all the bandwidth..."

That statement doesn't make sense to me. What do you mean by this? DOCSIS 2 is only capable of around ~40Mbps. The current crop of D3 modems are only capable of about 300Mbps but only if current chipsets maximum channels are exploited. Surely FTTN that serves 300 houses with a 50% penetration rate (150 customers) isn't going to be exhausted by one user even if everyone is configured with 100Mbps capability. 1) It's doubtful even a heavy user will be able to max out such a connection on one site because the other end is governed. They would have to use a multi-site download or some other kind of other file transfer mechanism that specializes in using multiple sockets to maximize throughput. 2) If the 150 customers are served by bonding different sets of some 20 channels, it's statistically unlikely that multiple exceptional customers such as this will collide.


cramer
Premium
join:2007-04-10
Raleigh, NC
kudos:9

... isn't going to be exhausted by one user even if everyone is configured with 100Mbps capability.

By definition, that's A CAP. Uncapped means zero obstruction to using the full bandwidth of the system. If it's capable of 40, you can use all 40. If it's capable of 300, you can use all 300.

If you don't think this is bad, or even possible, please stop by my office and I'll show you just how bad it can get thanks to ONE user! The *ONLY* thing that will put a limit in such a system is the speed of the remote side of the connection. (or connections) ISPs limit per user connection speeds and deploy queing methods to more evenly/fairly divide their finite bandwidth.

rradina

join:2000-08-08
Chesterfield, MO

You misunderstood what I meant by removing the throttle. We're also both probably using the wrong term for CAP since that's usually associated with a quantity of bytes over a period of time and not the speed at which they are transferred.

If one user can jeopardize the system, there are deep, deep issues that go beyond what we can discuss here.


BiggA

join:2005-11-23
EARTH
reply to cramer

Exactly. People used to uncap modems, and the cable companies cracked down on it, as if it became more widespread, it could have really screwed cable systems up... And yeah, one user could screw with a system if they were sucking the full bandwidth of all the channels.


rradina

join:2000-08-08
Chesterfield, MO

But that's in the past, isn't it? Isn't all that stuff now controlled by the CMTS? (i.e. PowerBoost?) If so, that means there's no excuse, other than poor management, for one user to lay waste to the "system" (whatever that means). At worst they can impact a node but if properly managed, the CMTS should be able to use pretty basic algorithms to balance what's available across all the node's active users. I say let them have it all...unless, as I've been postulating, the last mile is, for the moment, capable enough that if they did this, the problem would reveal itself upstream.


BiggA

join:2005-11-23
EARTH

Yes, Comcast does it farther upstream, but it's still a form of capping. It's necessary for a stable system.