Docsis 4.0 Certification Available | Hacker News Reader

Docsis 4.0 Certification Available

cablelabs.com

25 pointsdoener23 comments

DOCSIS 3.1 has been out for 10 years, and I'd be happy if Xfinity just offered me those speeds. Compared to max speeds of the standard, Xfinity offers up to 12% the download speed and 3.5% upload speed.

Why would they? What's the competition?

The problem isn't technical.

The cable monopolies are the robber barons of our time. Amazon, Google, Apple, Facebook, and, Microsoft all have competition. There is no real alternative to my cable internet provider. Satellite and 5G cellular are not effective competition and the old landline phone companies seem to have given up on expanding residential fiber.

Ireland (and I suspect other European countries) seem to have found a good model.

Right now, we have the following:

- FTTH networks (3 - POTS successor, electric company, government rollout) - cable TV networks in urban areas (docsis, fiber coming allegedly) - fixed wireless - 4g / 5g fixed installs - 4g / 5g hotspots - LEO / geostationary satellite

For most technologies (except cable), there is competition through retail companies that rely on wholesale providers for the network. Residents in urban areas typically have access to 1-2 high speed (FTTH / fast docsis) options but coverage is still variable countrywide.

In most urban areas, there are metro networks that businesses can tap into which reduces the cost of landing (diverse) fibers.

>What’s the competition?

If you’re lucky, local municipal fiber.

The competition is other local companies offering fiber. Around here, the incumbent telco offers fiber (Verizon Fios.)

And some of the problems are technical. To do those mid-split upgrades that provide more bandwidth, they'll need to replace every amplifier between the user and the HFC node. That's a lot of truck rolls. Only to find out there's tons of interference on those frequencies.... more maintenance. It's no wonder it's taken years to deploy DOCSIS 3.1.

I think the issue is that the bandwidth is shared. One of the things Xfinity is working on is moving to mid/high-split DOCSIS 3.1 which increases uplink speeds by allocating a larger frequency range to uploads. Even with mid or high-split DOCSIS 3.1, you're still sharing 450Mbps or 1.5Gbps with everyone on the same node. Without mid/high-split, you're sharing 108Mbps with everyone on your node. Another part of the network upgrade is splitting nodes and bringing fiber closer to the customer. If a node is serving fewer customers, there's less bandwidth that's shared.

The max speeds of the standard aren't really things that they can give you. Theoretically, LTE networks can give you 5Gbps, but the real-world experience is different given a shared link and signal loss/interference.

As I noted, Xfinity is updating their network to mid/high-split DOCSIS 3.1 and they're going to be increasing upload speeds to 75-200Mbps depending on your plan. They're already offering 1.2Gbps download speeds in my market. They're also supposed to start trials of DOCSIS 4 later this year.

I don't say this because Xfinity is a good company or anything, but you can't just look at the max speeds of a standard.

Notably also PON networks, the predominant last-mile fiber tech, is also shared medium with splits afaik going as high as 1:128. So for example classic GPON/EPON with nominal 1Gbps capacity can mean possibly only <10Mbps per-subscriber bandwidth allocation.

You are right, but with DOCSIS, you're generally sharing an order-of-magnitude smaller bandwidth allocation with many more users. Around here, there's 4 upstream channels available (roughly 120 megabits) shared across at least 200 homes.

Downstream is better, but it's still around a gigabit shared (32 DOCSIS channels.) Then you need to consider the RF issues that constantly plague cable networks, like ingress. Based on my personal experience, it can take months to get this fixed, if they'll even believe it's a problem. They'll open ticket for "outside plant" and not fix anything. At one point, I saw my upstream drop below a megabit! (And no, it wasn't my wiring or equipment.)

I recently switched to fiber, and it's night-and-day.

DOCSIS also carries unavoidable latency overhead in conversion to RF and back. This adds up.

I was going to write something similar. My cable company still doesn't support DOCSIS 3.1 upstreams, and it's been many, many years.

>Specifically, the DOCSIS 4.0 specification is designed to enable up to 10 gigabit per second (Gbps) downstream capacity and 6 Gbps upstream capacity.

Will we actually be able to see these speeds over existing copper?

Theoretically, copper cables can offer speeds of up to 10 Gbps. So they would be pushing the limit.

How so? What's the physical limitation based on?

I just found this: https://www.silicon-line.com/copper-cable-limitations/

Seems like signal loss is requiring bulkier and bulkier cables or shorter and shorter distances for higher bandwidths.

Nothing. Ethernet is already pushing >100G over single (twinax) copper pair.

What you can run over a few feet of twinax and what you can run over hundreds or thousands of feet of coax with multiple tiers of splitters like the DOCSIS specs are designed for are two entirely different things.

Sure, in 10 years when DOCSIS 6 comes out and your local cableco finally gets D4.

nice docsis 4.0 overview https://dgtlinfra.com/docsis-4-0-next-generation-cable/

Another nice DOCSIS 4.0 overview: https://www.tomsguide.com/features/what-is-docsis-40-everyth...

In the UK the largest cable provider, Virgin Media (owned by Liberty Global), is transitioning to fibre. I do not think there is much future for copper cables other than for short distances (which I class as within a building), or for non-broadband applications such as alarm pairs.

I think the current improvements we are seeing are less about copper competing against fiber and more about avoiding digging up the ground again to install fiber optic vs just using existing copper and upgrading the backbone instead.

I see the upper limit is 10Gbps but over what distance from the HFC junction is that possible? Are we talking a 500m, 5km, or more, and how does compared to fiber to the home?

Reply on news.ycombinator.com