A majority of households today buy broadband from cable companies that operate hybrid coaxial fiber networks (HFC) that us some version of DOCISIS technology to control the networks. The largest cable companies have upgraded most of their networks to DOCSIS 3.1 that allows for gigabit download speeds.
The biggest weakness in the cable networks is the upload data links. The DOCSIS standard limits the upload path to me no larger than 1/8th of the total bandwidth uses – but it’s not unusual for the cable companies to make this path even smaller and offer products like 100/10 Mbps where the upload is 1/11th of the total bandwidth provided to customers.
This is not a new concern for the cable companies and the engineering folks at Comcast and other big cable companies have been discussing ways to improve upload bandwidth for much of the last decade. They understood that the need for uploading would someday overwhelm the bandwidth path provided – they just didn’t expect to get there so explosively as been done in reaction to the COVID-19 crisis.
Every student and employee trying to work from home is carving out an uploaded VPN when they connect to a school or work server. Customers are also using significant upload bandwidth when they join a video call on Zoom or other platforms. While carriers report 30–40% overall increases in traffic due to COVID-19, they are not disclosing that a lot of that increase is demand for uploading.
Cable companies are now faced with solving the upload crisis. Practically every prognosticator in the country is predicting that we’re not going to return to pre-COVID behavior. There is likely to be a lot of people who will continue to work from home. While students will return to the classroom eventually, this grand experiment has shown that’s it’s feasible to involve students in the classroom remotely, and so school systems are likely to continue this practice for students with long-term illnesses or other reasons why they can’t always be in the classroom. Finally, we’ve taught a whole generation of people that video meetings can work, so there is going to be a whole lot more of that. The day of traveling to attend a few hour meeting might be over.
There is one other interesting fact to consider when looking at a cable company upload data path. Cable companies have generally devalued the upload path quality and have assigned the upload path to the low frequencies on the cable network spectrum. Historically upload data speeds were provisioned on the 5-42 MHz range of spectrum. This is the spectrum in a cable system that experiences the most interference from things like microwave ovens, vacuum cleaners and passing large trucks. Cable companies could get away with this because historically most people didn’t care if it took longer to upload a file or if packets had to be retransmitted due to interference. But people connecting to WANs and video conferences care about the upload quality as well as speed.
One solution, and something that some cable providers have already done is to do what is called a mid-split upgrade that extend the spectrum for uploading to the 5-85 MHz band. This still includes a patch of the worst spectrum inside the cable system, but is a significant boost in the amount of upload broadband available. Depending upon the settop boxes being used, this upgrade can require some new customer boxes.
Another idea is to do more traditional node splits, meaning to reduce the number of customers included in a neighborhood node. Traditionally, node splits were done to improve the performance of download speeds – this was the fastest way to relieve network congestion when a local neighborhood network bogged down unduly in the evening. It’s an interesting idea to consider splitting nodes to relive pressure on the upload data path.
After those two idea the upgrades get expensive. Migrating to switched digital video could free up a mountain of system bandwidth which would allow for a larger data path, including an enlarged upload path. The downside of this kind of upgrade is that it moves outside of the DOCSIS technology and starts to look more like providing Ethernet over fiber. This is not just a forklift upgrade it changes the basic way the network operates.
The final way to get more upload speed would be an upgrade to the upcoming DOCSIS 4.0 standard. Everything I read about this makes it sound expensive. But the new standard would allow for nearly symmetrical data services and would let cable network broadband compete head-on with fiber network. It will be interesting to see if the cable companies view the upload crisis as bad enough to warrant spending huge amounts of money to fix the problem.
Unfortunately, without a viable broadband competitor in most markets, the urgency to upgrade the network is just not there. As pointed out, changing up/down stream splits impacts quite a bit of equipment and associated laboe. I wouldn’t put it past the major MSOs to implement upstream bandwidth caps with upcharges for overages.
Continuing awesomeness, thanks Doug. Your posts always have an incredible trove of super interesting information.