DOCSIS 3.1 gigabit class modem goes online in Philadelphia | Hacker News Reader

DOCSIS 3.1 gigabit class modem goes online in Philadelphia

corporate.comcast.com

37 pointschejazi59 comments

I hate to be negative about progress but I wish companies would stop deploying DOCSIS and other time division multiple access strategies like that. Because DOCSIS is TDMA based its always going to have a problem with latency jitter and performance consistency and yet cable companies like to pretend it's the same as active Ethernet. Comparing 1gbit cable to 1gbit Ethernet is like comparing a dslr and a smartphone based on their megapixels.

Progress isn't linear, they're working on all sorts of problems and they're not just deploying DOCSIS for the sake of it. This is the next best solution that Comcast and other ISPs can do with the current infrastructure they have. This is the right way of approaching the problem, deploy DOCSIS 3.1 as the next step and figure out the replacement for DOCSIS in the future. Customers want these bandwidth right now, not later.

Also, DOCSIS 3.1 has improvements for bufferbloat issue and it would stabilize the current latency issues. They're not ignoring it completely.

If we do what you suggest, we'd be stuck at 10mbps for a long time and instead, we're getting 100mbps bandwidth that does work for your typical usage of netflix, gaming, and so on in a family household. There's a limit we'll reach very soon where no one will care about more bandwidth but they will want rather stability/latency improvements. Data caps is the next biggest issue.

A lot of execs from DOCSIS community agrees that 3.1 is the last upgrade to DOCSIS standard and the next replacement would be a Fiber-based one, which will take a few decades to even figure out. I rather have DOCSIS 3.1 now and not in 10 years because you think we should not do this.

Our US congress had the chance to fix this back in 1990s and they screwed up with enforcing it properly. We could've had a better pure fiber-based national build out but it didn't work out.

"Our US congress had the chance to fix this back in 1990s and they screwed up with enforcing it properly. We could've had a better pure fiber-based national build out but it didn't work out."

Sounds a little similar to what happened in the UK, iirc. British Telecom wanted to do a full fibre deployment but the government upheld complaints of it being anti competitive, and now we have to endure copper *DSL being the default national broadband option and all the pitfalls that entails.

"Our US congress had the chance to fix this back in 1990s and they screwed up with enforcing it properly. We could've had a better pure fiber-based national build out but it didn't work out."

I'm not familiar enough with the industry to have an opinion on this, but it sounds very odd that a private corporation is so tied to government that it can't innovate on its own? How does this work? And how did it end up like this? I guess what I'm after is an ELI5 on this last part of your comment :)

You cannot break grounds without permits from the city, state, and federal governments (highway, streets, poles, etc) and then you must have an agreement from the land owners to lay the fiber through the rest to the places, think apartment buildings, rental places, and so on.

After that, you then have to schedule the construction to comply with the city regulations for quiet hours, cleanup regulations, inspections, and so on.

All of that cost a lot of money that only the federal government can handle alas the highway project we did.

For an example, we could have a federal law that said every time we rebuild the roads, there should be fiber laid in. Every new house should have new fiber by default, new water/gas pipes should have fibers laid in alongside of it, and so on.

IIRC, one city in CA already requires all new house constructions to have fiber wired up.

Exactly this. Fibre should be laid down to new housing just like Water and Gas Pipes. We used to do that with telephone wires, why not internet fibre?

Nationwide private deployment of fiber within the required parameters (i.e. universal service, network neutrality) is impossible without government intervention. The cost is simply too high and the created value is too hard to monetize.

Google Fiber?

Google Fiber doesn't deploy in any city that imposes build-out requirements, which compromises the universal service constraint. Build out requirements are also why my building and a couple of others have FIOS but nobody else does here in Baltimore. Verizon tried to build it, but the city wouldn't let it pick and choose which neighborhoods.

Google has also stated that Fiber is a way to shame ISP's into building fiber. It's not clear that an independent company that didn't have synergestic internet businesses would undertake the same capital investment.

Nearly every SP has made investments in "synergistic internet businesses." They appear to expect to extract the benefits of vertical integration in those businesses without making Google's investment in access.

Also, Google has announced the intention to bring Google Fiber to several major cities. It's not a demo, or hobby, anymore.

Switched ethernet is also practically TDMA. You can't send multiple packets in the same time. Although gigabit ethernet is full duplex, so you can receive and send in the same time.

Practically DOCSIS adds about 3-5 ms. Which is upper range of how much wifi adds latency.

Compare that to usual peripherals. Wireless mouses, about 50-100 ms latency, typical computer displays about 16-50 ms, flat screen TVs 80-200 ms.

Practically speaking modern Ethernet switches are non blocking though which allows every port to talk to every other port at full speed. With DOCSIS being TDMA there isn't a way to improve speed to the backbone (other than adding more channels / smaller time slots).

Also 3-5ms is probably at the low end since it heavily depends on the usage patterns of those on the same CMTS as you.

It's not TDMA, it's FDM. (It seems you've severely misunderstood DOCSIS.) And this is the best they can do with the existing network.

Feel free to run an Ethernet cable from my house to yours, though.

It's both TDMA and FDM. Your modem can bond multiple channels on the same coax but each channel is shared amongst all the subscribes on the CMTS. Each DOCSIS revision ups the spatial efficiency of each channel but also ups the number of channels.

On a side note, my ISP incentives users to upgrade their modems by offering more bandwidth for the same money if you buy a modem that can bond more channels. For example I had a 8/3 DOCSIS 3 modem on a 60mb plan, for the same price they gave me 100mbit for upgrading to a modem that could bond 24/8. It allows them to utilize the network more efficiently

But how big is the jitter? A bit of searching suggests it's typically under a millisecond, and that's barely anything. Most modems I've seen have a baseline latency of something like 20 milliseconds.

20ms baseline latency is pathetic. Ping from a data center in Los Angeles to one in San Francisco is typically a little over half what it apparently takes your modem to send a packet upstream. 20ms is like half way across the country. Why is latency at the last mile so awful?

What is the latency typically like on stuff like Google Fiber?

Baseline on my DOCSIS 3.0 modem is as low as 5 ms when I've tested it. That anyone should care about a 5-ish ms overhead is ridiculous imo.

It's great when it's that low, my problem with DOCSIS is that it's not consistent. When there is low utilization in your neighbourhood it's fine but when everyone is home for the holidays for example it becomes unbearable.

For example, I usually get about 8ms to a server hosted in the same city as me (10ms to google) but on bad days it gets as high as 60-80ms.

I regularly tether my LTE enabled phone where I get around 20ms but it's consistent.

The DOCSIS 3.0 modems we use at our local provider have no where near that much latency. 5-8ms is typical.

On my completely regular residental broadband, built with standard ethernet almost fifteen years ago, I have 4 ms to my server in the cloud (same country, different provider). If Google Fiber is built with similar parts it should be comparable.

Am on gigabit fiber here, next hop is <1ms as it should be.

> Comparing 1gbit cable to 1gbit Ethernet is like comparing a dslr and a smartphone based on their megapixels.

In both of those cases the majority of customers doesn't care about the difference.

People that play games and get 1ms latency vs 20-30ms latency within the same town/city care, and that isn't a very small market..

What do you propose they should do? Is it compatible with their existing infrastructure? Does it play nice with existing consumer devices? What does the roll-out cost and time-frame look like?

So now you can blast through your monthly bandwidth quota in mere minutes? :P

You really have to appreciate how Comcast really tries to sound advanced with "World's First" in the headline.

Assuming the upload will again be 1/5th the download speeds, you're looking at 1Gbps down / 200 Mbps up for a total bandwidth of 1.2 Gbps. That means in a 30 day month you can use up to 388,800 GB of bandwidth. Subtract your 300 GB "courtesy bandwidth" and you're at 388,500 GB over your courtesy limit. At $10 per 50GB you'll need 7,770 separate 50GB "packages" at $10 each totaling $77,700 per month in overages.

That calculation really doesn't apply to 99% of what people use their internet connections for. It takes me 15 minutes to update Office over me 50 mbps connection. I'm not going to download twice as many updates because my net connection is twice as fast. I'm not going to buy twice as many iTunes movies or twice as many games on Steam.

Perhaps, but many people watch Netflix, and by default Netflix consumes as much bandwidth as it can in order to stream at the highest quality available. This is going to sting for those non-teksavvy Netflix users.

If this had been true then Netflix should have been digitizing analog sources dynamically, which would be all over the news. So I doubt Netflix does that, they only can use as much bandwidth as there is in their sources.

The majority of users already pull the top bitrate. The lower bitrates are only used by mobile clients and users on very bad connections.

So if someone were to ping-flood a Comcast user's home IP... that could get expensive quickly, and there is almost nothing the user could do about it. So weird, and quite unfair.

That's okay, you can just call up Comcast's customer service agents and they'll be super polite and friendly and make all sorts of wonderful promises while they fail to do anything useful at all.

I'm sure cable execs are kicking themselves for not implementing usage-based billing two decades ago. Nearly every other service is usage-based but no one complains, because they've always been usage-based.

The difference is that cable companies want it both ways. They charge you a minimum for a set amount of serivce AND they charge you if you use more than that AND you don't always get what you pay for (since it's "up to" xx mb/s)

With water if I don't use it I pay zero. If I use xxxx gallons I pay for xxxx gallons and if I turn the tap and water doesn't come out I get a bill credit at the very least.

With the internet I pay $50/ month whether I use it or not, if I pay for 100gb and I use 105gb then I pay $20 for the overage and if I have DOCSIS and everyone in my neighbourhood is using their internet then too bad for me that it doesn't work.

I think most other items are usage-based because when you use them they are gone. When you use electricity or water, more needs to be generated/cleaned.

Not so with Internet. It is more like phone service. If I make a call, nothing needs to be rebuilt for another one.

I believe it is obvious to people and that is why there is push-back.

Competition existed in the past.

From who? Dial-up SLIP/PPP and ISDN could hardly be considered competitive with a DOCSIS product. The market is far more competitive now, with increased FTTP deployments and advanced wireless.

Before the frequencies were reallocated to mobile usage, Sprint ran a cable-modem-over-wireless product called Broadband Direct that was pretty nice for its time. The system had a 30+ mile range to the towers, so lots of area could be covered with few towers.

The DSL/cable discrepancy also used to be smaller, and there were more, smaller cable providers.

blast through your monthly bandwidth quota in mere minutes

It would take 40 minutes of gigabit download to hit the typical Comcast monthly limit of 300 GB. And then I guess you sit around and cry for 29 days, 23 hours, and 20 minutes.

Perhaps they'll throw in a few extra GB if you sign up for this.

While I don't like quotas, I don't understand this kind of comment.

Even people who don't use large amounts of bandwidth can't benefit from high speeds.

Quotas become more and more restrictive the higher the bandwidth is (e.g. a 1GB limit on a 2G mobile network is basically unlimited traffic due to how long it takes to fill it. The same 1GB limit on a 4G LTE+ network could be consumed in mere minutes).

> Even people who don't use large amounts of bandwidth can't benefit from high speeds. What does that sentence mean? I don't understand this kind of comment.

Sorry. There was a 't too much. It should be: Even people who don't use large amounts of bandwidth can benefit from high speeds.

My point is, when I went from 50/10 cable to gigabit fiber there was no change in how much bandwidth I was using. The things I did just went faster.

Well when someone can now use Netflix Super HD and don't know they need to go into their Netflix account and disable it, they'll suddenly be using a great deal more bandwidth than before.

yes, but unless they had so slow speeds that super HD would not work I dont see how it changes things.

I've had Comcast "Business Class" service (50/10, five statics, no caps or blocked ports) for almost five years now, after I had to move my colo box home when the ISP it was hosted at changed owners (lost a sweet discount I was getting as an ex-employee/consultant).

As someone who spent years in the ISP industry (at multiple companies) and does sysadmin/networking for a living, I never thought I would say "I'm happy with Comcast" - but I do.

Then again, I pay $150/month, quite a bit more than their normal customers... but every time I've had any sort of issue (usually on their end) it's been resolved rather quickly, without having to jump through hoops or go through scripts. I was told that the Business Class techs here in Houston are the former 3rd-tier techs for Time Warner.

It was nice, for example, when I called in to get some reverse DNS done for my static IPs, to be talking directly to the guy who was typing them in as I spoke to him.

At one point about six months after I got everything set up, I wasn't getting the full upstream that I paid for - even to Comcast's own internal systems (which eliminates the "Internet congestion" factor). After a couple of phone calls, I woke up on a Saturday to a knock on my door. Three techs, two supervisors. "We're not leaving until this is fixed, and we brought a completely unlocked modem to see just what your line will handle.."

They laughed and declined to "accidentally" leave that one for my account. :)

Numericable has been offering 800 Mbit cable in several cities in France for over a year now :-) Oh, and unmetered BTW :)

But not IPv6, which is a shame. Can't wait for Free to get their act together and wire my apartment to a better fiber connection.

Is not being IPv6 really a problem? 90% of the world isn't. Comcast has the largest IPv6 network but it's deployment is dual stack so most everyone is still using IPv4.

Has anyone experience DOCSIS services where you simply can not connect / renew IP for a few hours, and then after some reseting and messing around you will finally get your IP again.

Another concern I had is how much more complexity DOCSIS 3.1 is adding. The chip to decode easily get overheat. While subsequent version of the chip controller and devices will improve, most cable provider will use the first generation for as long as possible.

Where is G.Fast? The DSL equivalent of DOCSIS 3.1?

> Has anyone experience DOCSIS services where you simply can not connect / renew IP for a few hours, and then after some reseting and messing around you will finally get your IP again.

Sounds like the ISP doing maintenance, had that every few weeks late at night when I was still on cable.

ah, THAT explains why verizon finally rolled out fios to my section of philly in the last month or so.

So, if you want to buy your own (quality and/or to avoid their "shared/public" wifi/phone functionality), what are the current recommendations for this speed level? For residential? For business class?

(Is it still the Motorola line?)

Wonder if they activated at the Comcast Building too. Looking forward to test it out next time.

The problem in the USA is these announcements are more geared to train consumers to accept prices to go up even further on every tier level.

However this announcement specifically says they don't have to make any infrastructure changes so it will be hard for them to explain price increases.

How could 10x the bandwidth not require backend changes? Would need at least 10 gb to each neighborhood which I doubt they have now.

You're assuming they do something else. Isn't it enough to blame slowness on "congestion" and then use it to justify bandwidth caps?

"The reason it's slow is your greedy neighbors - we'll charge them more money and then you'll get the speed we promised."

Yes, I'm being overly cynical. I do not like Comcast.

> Would need at least 10 gb to each neighborhood which I doubt they have now

The backend connectivity is just a matter of exchanging the coax-fibre gateway in the roadside boxes and at the fibre terminator. No need to dig up the streets for that, and in most cases, each roadside box is connected with multiple fibre pairs so additional capacity can be deployed with ease.

Sure no one said they need to dig up the street. But they do need to make CHANGES.

Infrastructure price-per-bit has been plummeting.

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