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Comment by zahma | Hacker News Reader

Surprised it’s actually symmetrical. Though I’ve never understood why, it’s always perplexed and irritated me that they typically offer upload bandwidth at a tenth of download. In the day and age of remote work, you’d think this would be illegal.

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The short but unfulfilling answer is that this is because the DOCSIS standard historically has allocated a much broader frequency range for DL than UL. Unlike other forms of communication (like cell) that can use similar frequency ranges for transmit and receive, DOCSIS tends to slice something like < 70Mhz for UL and >70Mhz to 1Ghz for DL (I'm probably remembering the details incorrectly, trust Google over me!). Switching the frequency ranges often requires different circuitry and therefore different hardware.

I would guess that unlike fiber -- rarely saturated in a consumer context -- people have ~always wanted more than what cable can provide and thus the operators needed to be strategic about the allocation of bandwidth between DL and UL, hence the asymmetry.

I would say that cell signals mostly can't use the same frequencies for sending and receiving. The newer TDD allocations at 2.5GHz and above that carriers in the US are rolling out today do use the same for transmit and receive, but most of the old frequency ranges are exclusively up or down.

The difference is that cellular licenses generally offered equal bandwidth to up and down (ex. 10MHz down and 10MHz up). That's because they were originally designed for somewhat symmetrical communication: phone conversations where you assume each party is talking (sending) and listening (receiving) reasonably equally. With DOCSIS, it was designed assuming (correctly) that there'd be a lot more download traffic than upload traffic (which still holds true even in the era of remote work).

Actually most of the capacity problems on cable networks come from upstream congestion; not downstream congestion and this has nearly always been the case. When the upstream gets congested TCP ACKs get dropped and it kills download speed.

Upstream has always been challenging on coax. The first cable modems didn't even use the coax for upstream, instead it used a separate dial up modem.

I'm not entirely sure of the details but even after that DOCSIS has always had to use much lower frequency channels for upstream which are much more limited vs downstream which tends to use higher frequencies. Potentially because it was hard to get high frequency transmitting upstream low cost CPE devices back in the day?

It's about prioritizing downstream since that's 90% of the traffic and what customers complain about the most. No normal customer complains about their upstream cap, but they will freak out over congestion or not having the fastest download speeds

That, also the relatively low frequency range was originally only there for the sake of public access and the like; they only expected a relatively small number of channels on the return path.

I didn’t generally see upstream congestion when I worked on Internet QoE at Comcast, downstream was more common. Cable modems do ACK suppression as well to help there.

It's been a technical limitation. DOCSIS 3.1 and below allocate certain frequencies to download and certain frequencies to upload. There's a lot more allocated to download because of how people typically use the connection. DOCSIS 3.1 moves to a more flexible channel structure that allows for high-split systems. Xfinity has been rolling out 75-200Mbps upload speeds with their DOCSIS 3.1 network, but DOCSIS 3.1 is still lacking for gigabit symmetrical connections.

DOCSIS 4 mostly removes that limitation and allows for the full amount of spectrum to be used for up or down.

Its because DOCSIS has a limited number of frequency channels which can be assigned as either upstream/downstream and if they're comically over-subscribing their infrastructure you can offset that a bit by allocating most channels to downstream. I guess their thinking is that most users are going to be doing download heavy tasks and not upload, so it doesn't matter.

My guess is that they prefer people to be doing download heavy tasks and not upload.

I think it's perhaps 1% preference and 99% realization of the reality.

  Up: "Hey YouTube, I'd like to watch this video."
  Down: Hundreds of MB of data from YouTube

  Up: "Hey <streaming TV>, I'd like to binge watch <XYZ>"
  Down: Hundreds of MB of data from the streaming service

Asymmetrical connections got more asymmetrical over time, limiting the utility of upload and shaping use of the internet (in most of the US) into more of a content portal or cable tv-like experience than it might otherwise be. I don't think it was purely an emergent phenomenon based on tech and consumer demand, but rather had a strategic element. I'll spare you all my tenuous reasoning, though, since I haven't got any real evidence that was the case.

Possibly because most users are using the Internet as a content portal, and that's all they want it for?

Plenty of consumer features could exist, like sharing actual high bitrate streams of your desktop or camera to others or syncing large amounts of data to servers for backup/sharing.

You miss the point. Those features do exist, and technically savvy folks like us use them (and they work fine with my asymetric connect). But the vast majority of users want YouTube/TikTok/etc to stream without a glitch and couldn't care less about backups, and as far as "high bitrate streams", pretty sure most users are thinking "works good on my iPhone, is good enough".

Wouldn't this impact their peering agreements?

Summarizing greatly, but user upload = Comcast pays vs user download = Comcast's peers pay them.

I'd assume for last-mile ISPs, peering is a non-negligible source of revenue.

Peering is based purely on negotiating power so Comcast will get paid no matter what happens.

Most of Comcast’s internet is exchanged through transit-free peering agreements, so only about 1% of Comcast’s outbound traffic requires them to pay for IP transit. And that traffic is mainly overseas, so Comcast is effectively a Tier 1 network in the US. Which means their customers’ outbound traffic doesn’t cost them anything.

For most last-mile ISPs, peering isn’t a revenue source. Small ISPs have to pay for peering and IP transit, and large ISPs have transit-free peering agreements with most, if not all, of the internet.

However, large ISPs that enjoy regional monopolies can refuse to upgrade connections with peered networks in an attempt to force the content providers sending traffic over the peered network to instead peer directly with the ISP.

This tactic is really only feasible for ISPs who have captive customers that are unable to switch to another ISP, as the negotiation process requires the ISP to allow the service it is providing to its actual customers to degrade to such an extent that the content provider is forced to peer directly with the ISP.

I think it's not so much that they care, just marketing.

If you have 1.2Gbps total bandwidth and you can split it as you wish, which do you think looks better to customers? 1Gbps (+200Mbps upload) or 600Mbps symmetric? Easier to sell a bigger number.

It's honestly probably that silly.

In my area it's more like 1Gbps down and 30Mbps up, which is very frustrating. That's only the tip of my iceberg of complaints about Comcast here. (A competition-free market, of course.)

Upload = people able to host and do things on their own.

Media companies like NBC/Sky/Universal/Xfinity/Comcast do not want you to be creators. They want you to consume consume consume... and it doesnt count against your bandwidth if you consume from THEM.

In addition to the frequency split mentioned by others, you can get much better utilization on the downstream channels than the upstream channels. Both are shared between all users on a node, but downstream has one transmitter and upstream has many, coordination and equipment tolerances mean the upstream can't be as tightly multiplexed. (GPON runs at 2.4G down, 1.2G up for this reason)

However, even with work from home, most users aren't pushing that much data. Teleconferencing is usually many streams in, one stream out. People working with large data feeds typically get a workstation somewhere with good connectivity and remote into it, where you send keystrokes and get big pictures. I have a pretty sad upstream, and it's not been a major problem, even if when I am pushing things from my home. Although there are a few tasks I avoided from home when I had a well connected office a few days a week.

For why it's symmetrical now specifically: killing QAM TV delivery frees up a lot of bandwidth for DOCSIS. Until that was a possibility, DOCSIS competed with 200+ channels for cable companies to allocate spectrum to.

Have many major cable companies actually stopped offering (non-IP-based) TV? I hadn't heard about that.

I think US cable companies have to offer the option indefinitely because of CableCard, but they’re certainly moving to drop legacy TV delivery as much as possible.

The reason cable is asymmetrical is because cable plants weren't designed for two-way communication. Cable originally was a one way broadcast system with a tiny upstream path they eventually leveraged for Video-On-Demand/Pay-per-view (VoD/PPV).

I used to work with cable modems, and it's miraculous how they got this huge amount of performance out of their physical plant by basically hacking on their stuff until it worked. The cable industry has this thin layer of really smart guys and a huge number of porn hound meatheads.

I mean, did you know cable internet is basically token ring? Seriously. Not sure if that's for all implementations or just Comcast.

These wires were never meant to do anything close to this...but here we are.

One of the reasons this is so hard BTW is that the plant has to also support all that legacy equipment that's still connected and running. There are people with cable that haven't upgraded their box for 50 years and never will. You don't want to impact their service, period. No calls, no truck rolls.

> You don't want to impact their service, period. No calls, no truck rolls.

From my experience this is absolutely not true. Comcast had zero issues intentionally crippling my internet connectivity because the modem I owned only supported DOCSIS 2.

I received letters for months that I needed to upgrade my modem to support a “the best speeds”. Then I didn’t, and my speed dropped to less than a megabit per second.

I could have waived it off as a coincidence, except a couple of months later I was telling the story at a happy hour and it turns out the exact same thing happened to another guy right around the same time.

Comcast does not care if you have a shitty experience. They don’t care if you call. Me not upgrading and calling support about it is just the cost of them doing business.

You are not 50,000 people spread across the state.

Sometimes installers fuck up. But Comcast (and every cable company) endeavors to not brick all of their customers in a region.

You need about 4Mbps up for a high quality stream up to converse live in HD. A reasonable asymmetrical connection on plain Jane docsis 3.1 already offers 20-50Mbps. It being asymmetrical isn't preventing many from working remotely.

A bigger issue is how many areas are so poorly served that in the present time there is no point calling it high speed.

That said ISPs tend to scale up with down so even if you might be reasonably served with 100Mbps down if you want a reasonable up you will have to upgrade to the higher down. If you intend to work from home this doesn't seem altogether unreasonable. When working for an ISP I was always surprised about how many complainers whose remote work was "so" important paid for bad speed, delivered via bad hardware, connected to bad wifi, on another floor.

From https://www.boxcast.com/blog/internet-speeds-for-4k-live-str... :

> Even with good compression, video content still requires a significant amount of bandwidth. For example, YouTube recommends sending 34 Mbps for 4Kp30, and 50 Mbps for 4Kp60.

> In addition to needing high internet speed for 4k streaming, you need to factor in more bandwidth for your audio (typically in the 128–320 Kbps range) and a small amount more for overhead. Then double it — you should plan to always stay at 50% or less of available bandwidth in case of disruptions

This isn't terribly relevant because remote work gets done via tools like zoom at 2-4Mbps up not by live streaming 4K on youtube.

4Mbps up per person can work, but much the same way as 15Mbps down can work. It's very reasonable to want much more.

> That said ISPs tend to scale up with down

Not in my experience, on both cable and phone lines.

Every major cable ISP in the US works this way. Logically this is because they aren't upstream limited except insofar as the inherent limits of DOCSIS 3.1 providing higher upstream is a very obvious market segmentation tool to get folks to pay for higher tier plans.

For instance here is a good example of Comcasts scale in upload

https://www.connectcalifornia.com/internet-service/xfinity-p...

Astound is the same

Spectrum

https://www.reddit.com/r/Spectrum/comments/z1f5tm/dumb_quest...

Please forgive the annoying second party sources most providers have this annoying flow where you have to almost sign up for internet to see specs and such.

Huh, okay. Well I couldn't find good info of increases last time I looked, and Spectrum was running 100 and 300 at the exact same upload. Good to know I could overpay for 35 if I needed to.

The ACTUAL answer is that it separates out business from residential service - and pricing.

When I first got cable decades ago, it was symmetrical by default.

But they figured out business customers need symmetrical and are price insensitive, while residential customers really just need consumption and are very price sensitive.

The idea is that they can charge businesses more, and individuals less and get away with it.

This is just like airfares, where business customers travel during the week and want to be home for the weekend, and individuals will stay the weekend and are price sensitive.

Because actual traffic for the overwhelmingly vast majority of users is asymmetrical, and traffic engineering isn't about the 1 out of 10,000 customers who want to run a server. Even remote work is highly asymmetrical, at least looking at stats on the couple of tens of thousands of users we have WFH.

Illegal? Under what delusional definition of 'illegal' would you classify "doing what works for pretty much everyone but you"?

This may surprise you, but the majority of broadband infrastructure in this country was set up before the pandemic and the WFH explosion. When 99 44/100 percent of people consumed exponentially more bandwidth downstream than upstream.

Because highly upload capacity costs serious money and retail customers aren't willing to pay for it.

Yet every fiber provider sells 1gbps up for $70-$100…

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