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I do quite a bit of DOCSIS consulting. There are both technical and business reasons for the gap between upstream and downstream speeds There are a few techn

by tonyb 7y ago

I do quite a bit of DOCSIS consulting. There are both technical and business reasons for the gap between upstream and downstream speeds There are a few technical reasons. There is less upstream frequency available in the upstream. 42 MHz is the standard upstream/downstream split, 85 MHz is a midsplit, 200 MHz is a high split, and the downstream goes up to 1Ghz or even 1.2Ghz. The upstream modulation runs at 64 QAM (~27Mbs) and downstream modulation runs at 256 QAM (~38 Mbps). The upstream is also more sustainable to interference and impairments. So the technology is inherently imbalanced. From a business prospective it is very difficult to cost justify. Moving the upstream/downstream split and/or upgrading to DOCSIS 3.1 is very expensive. The reality is that the typical customer use very little upstream bandwidth. It isn't uncommon for me to see a node with 24 or 32 downstream channels at 80% usage and 4 upstream channels are at 25% utilization or less. We see a downstream to upstream usage ratio of about 15:1. If you move the US/DS split that means you are taking away from available downstream frequency which means less DS data bandwidth or fewer video channels. It's hard to make a business case to invest in increasing upstream bandwidth when the data says people aren't going to use it. Newer technology like DOCSIS 3.1, Docsis FDX, Remote PHY and modern plant designs like N+0 or N+1 (which means fewer customers per node) will bring higher upstream bandwidth, but it will be awhile before we see anything close to symmetrical speeds.

Namidairo 7y ago
You should take a look at Australia, where we try to shove hundreds of customers onto a single node (Up to 900 per node, up to 250 per segment). Edit: Although it wouldn't be fair to leave out that it's a EuroDOCSIS 3.0 setup with 16/4 downstream/upstream, with very limited 3.1 being used on a small scale.
- samstave 7y ago
  Isn't telstra just riddled with stories of corruption over time? https://www.channelnews.com.au/key-telstra-5g-partner-admits-to-bribery-corruption/ https://www.channelnews.com.au/key-telstra-5g-partner-admits...
  - nojvek 7y ago
    Telstra is the equivalent of Comcast here. They’re monipolies in large parts of the country so they can get away with a lot
    - MrMorden 7y ago
      And NBN's wholesale charges are comparable to what a retail ISP in a competitive market (e.g. Stockholm) charges for symmetric 10Gb/s FTTP. https://www.itnews.com.au/news/nbn-co-puts-future-residential-arpu-at-49-a-user-530383 https://www.itnews.com.au/news/nbn-co-puts-future-residentia...
      - wbl 7y ago
        You could run a lot of websites on that.
- mcbridematt 7y ago
  Also prior to the NBN (wholesaler) taking over the network, "take rate" (number of homes actually connected to the cable) was ~30%. Changing a network designed around that to 80% is quite a task
- anonsivalley652 7y ago
  Dave at EEVblog entered the chat ;) IIRC, Australia has limited broadband options, they're expensive and data is expensive relative to other countries. Also, isn't data transiting outside of AU more expensive than intra-national data? In the US, there's a 1 GbE variant of Comcast "cable modem" service called Xfinity that often has a 1000 GiB "data plan" (varying by state, some states have unlimited data) that imposes a charge per GiB beyond that. Where I use it, the network is all optical with copper from poles to customer. During power outages, it only lasts about a day... and we now have 3-6 day "public safety" outages in the summer.
- tonyb 7y ago
  Yikes! I mostly work with small providers that don't have the same resources as the big guys so I'm dealing with networks that are Node + 7 or more actives (vs the N+0 or N+1 the big guys do now) and anything about about 200 modems is when we start planning for node splits.
samstave 7y ago
Awesome post, thanks for that.
scurvy 7y ago
It also doesn't make sense to turn your millions of residential cable customers into DDoS cannons. Best to leave them as DDoS pea-shooters. Though on second thought, it might help out your ratios.
- cma 7y ago
  If they all get together and increase upstream then they can start selling do’s protection, like the phone companies did for spam calls.
ABeeSea 7y ago
>The reality is that the typical customer use very little upstream bandwidth. I’m not trying to disagree with this especially since you are talking about coax, but the new mmwave WiFi installations at places like Ohio state stadium have shown the opposite. The vast majority of their traffic were photo and video uploads to social media. Consumers want upload; it’s just overshadowed by streaming.
- usmannk 7y ago
  I imagine usage patterns in the home and at an event are very different.
  - OGWhales 7y ago
    But he does make a decent case that we generally upload more since the explosion of social media. Not sure by how much since people stream SO much.
- tonyb 7y ago
  That's interesting, I wouldn't have considered that but it make sense. If I'm at a football game or concert I'm much less likely to be streaming content and much more likely to be sharing content than a user at home. On an unrelated note - I've been pretty disappointed with the WiFi at The Shoe. The first game I tried to use it I couldn't event join the network, the second time I could join but it wasn't usable. It was early in the season though so they could have still be working out the bugs - I can't even imagine how much goes into supporting a system like that. Trying to get 100k devices on a WiFi network is impressive.
0x8BADF00D 7y ago
Couldn't they use something like code division multiplexing?
milankragujevic 7y ago
Just wanted to mention the info that the biggest or second biggest (depends on how you count, it's a duopoly) cable ISP in Serbia is finishing up the migration to DOCSIS 3.1, and will provide gigabit speeds to cable customers. However, the upload will still be 50 Mbps maximum. Currently the fastest they have is 300/15 Mbps, which is better than what they will offer with DOCSIS 3.1 -- 1000/50 Mbps. Most of their passive and active equipment in areas which have been fully "digitalized" is 3.1 compliant, they just need to finish the whole city and then they will start marketing the offer. Modems will have to be changed as well as equipment on the customer's side which they haven't done yet, so it will take quite some time. They "promised" it by the end of 2019. (in 2016.), seems it will be 2025. By that time the Chinese government and Telekom Srbija will have FTTH to every home.
- labawi 7y ago
  > 300/15 Mbps, which is better than .. 1000/50 Mbps. How is 300/15 better than 1000/50?
  - milankragujevic 7y ago
    It's cheaper per megabit ($120 vs $20 per month) and a better DS:US ratio. edit: the ratio is the same, I just haven't powered up my brain yet.
    - jefftk 7y ago
      The ratio is 20/1 in both cases
      - milankragujevic 7y ago
        Oh, I haven't even thought to check. Sorry.
- tonyb 7y ago
  This doesn't surprise me. Most providers that are deploying DOCSIS 3.1 today are only doing OFDM in the downstream and the upstream is still doing ATDMA (same as DOCSIS 3.0). I'm sure there are some but I don't know of anyone doing 3.1 in the upstream yet. If they did upgrade all their actives then 3.1 upstream is likely in the works. DOCSIS has some pretty amazing diagnostics and troubleshooting - I can look at a modem and say "approximately 71 ft from the modem there is a break in the cable causing an RF impairment" or "These 14 modems in the same neighborhood show the same impairment - there is likely a fault at this specific segment of cable". DOCSIS 3.1 expands on that even more and as more 3.1 CPEs get deployed operators are able to leverage that additional data to get the plant ready for 3.1 upstreams. OFDM frequencies are also not backwards compatible with 3.0 CPEs but a 3.1 CPE can bond both types of channels, so as the ratio of 3.1 CPEs increases that allows operators to shift more frequencies from legacy modulation to newer 3.1 modulation.
avip 7y ago
This kind of comment is why I read HN
fireattack 7y ago
> So the technology is inherently imbalanced. I won't call it inherently, or even "technical reason(s)". Nothing stopped the standard to split the frequency bands for up and downstream in a more way, or even swap the frequencies for each. They're simply configured/designed this way is because of the business reason.
- fireattack 7y ago
  Typo: "more even way"
tinus_hn 7y ago
Of course cable companies don’t mind turning the internet into a consumer/producer model as well.
snthd 7y ago
>The upstream is also more sustainable to interference and impairments. s/sustainable/susceptible/ ?
doomjunky 7y ago
Why isn't there any dynamic allocation of the up-/downstream channels?
- apexalpha 7y ago
  From the linked article: ". I should also note that since the cable operators' infrastructure was built around sending the same TV signals to all houses, they basically just run one cable to your neighborhood, and then use passive splitters and dumb amplifiers to split that one cable to all the houses in your neighborhood. So you don't have a dedicated coax cable directly from your house to their headend equipment, so they can't change the frequency split on a house-by-house basis."
- tonyb 7y ago
  Because of the equipment out in the plant. There are passive devices out in the field that split the upstream and downstream (such as directional couplers). Passive devices are favored over active devices whenever possible because they are much less likely to fail, are less expensive, and require less maintenance.

by tonyb 7y ago

Namidairo 7y ago

You should take a look at Australia, where we try to shove hundreds of customers onto a single node (Up to 900 per node, up to 250 per segment). Edit: Although it wouldn't be fair to leave out that it's a EuroDOCSIS 3.0 setup with 16/4 downstream/upstream, with very limited 3.1 being used on a small scale.

samstave 7y ago
Isn't telstra just riddled with stories of corruption over time? https://www.channelnews.com.au/key-telstra-5g-partner-admits-to-bribery-corruption/ https://www.channelnews.com.au/key-telstra-5g-partner-admits...
- nojvek 7y ago
  Telstra is the equivalent of Comcast here. They’re monipolies in large parts of the country so they can get away with a lot
  - MrMorden 7y ago
    And NBN's wholesale charges are comparable to what a retail ISP in a competitive market (e.g. Stockholm) charges for symmetric 10Gb/s FTTP. https://www.itnews.com.au/news/nbn-co-puts-future-residential-arpu-at-49-a-user-530383 https://www.itnews.com.au/news/nbn-co-puts-future-residentia...
    - wbl 7y ago
      You could run a lot of websites on that.
mcbridematt 7y ago
Also prior to the NBN (wholesaler) taking over the network, "take rate" (number of homes actually connected to the cable) was ~30%. Changing a network designed around that to 80% is quite a task
anonsivalley652 7y ago
Dave at EEVblog entered the chat ;) IIRC, Australia has limited broadband options, they're expensive and data is expensive relative to other countries. Also, isn't data transiting outside of AU more expensive than intra-national data? In the US, there's a 1 GbE variant of Comcast "cable modem" service called Xfinity that often has a 1000 GiB "data plan" (varying by state, some states have unlimited data) that imposes a charge per GiB beyond that. Where I use it, the network is all optical with copper from poles to customer. During power outages, it only lasts about a day... and we now have 3-6 day "public safety" outages in the summer.
tonyb 7y ago
Yikes! I mostly work with small providers that don't have the same resources as the big guys so I'm dealing with networks that are Node + 7 or more actives (vs the N+0 or N+1 the big guys do now) and anything about about 200 modems is when we start planning for node splits.

samstave 7y ago

Awesome post, thanks for that.

scurvy 7y ago

It also doesn't make sense to turn your millions of residential cable customers into DDoS cannons. Best to leave them as DDoS pea-shooters. Though on second thought, it might help out your ratios.

cma 7y ago
If they all get together and increase upstream then they can start selling do’s protection, like the phone companies did for spam calls.

ABeeSea 7y ago

>The reality is that the typical customer use very little upstream bandwidth. I’m not trying to disagree with this especially since you are talking about coax, but the new mmwave WiFi installations at places like Ohio state stadium have shown the opposite. The vast majority of their traffic were photo and video uploads to social media. Consumers want upload; it’s just overshadowed by streaming.

usmannk 7y ago
I imagine usage patterns in the home and at an event are very different.
- OGWhales 7y ago
  But he does make a decent case that we generally upload more since the explosion of social media. Not sure by how much since people stream SO much.
tonyb 7y ago
That's interesting, I wouldn't have considered that but it make sense. If I'm at a football game or concert I'm much less likely to be streaming content and much more likely to be sharing content than a user at home. On an unrelated note - I've been pretty disappointed with the WiFi at The Shoe. The first game I tried to use it I couldn't event join the network, the second time I could join but it wasn't usable. It was early in the season though so they could have still be working out the bugs - I can't even imagine how much goes into supporting a system like that. Trying to get 100k devices on a WiFi network is impressive.

0x8BADF00D 7y ago

Couldn't they use something like code division multiplexing?

milankragujevic 7y ago

Just wanted to mention the info that the biggest or second biggest (depends on how you count, it's a duopoly) cable ISP in Serbia is finishing up the migration to DOCSIS 3.1, and will provide gigabit speeds to cable customers. However, the upload will still be 50 Mbps maximum. Currently the fastest they have is 300/15 Mbps, which is better than what they will offer with DOCSIS 3.1 -- 1000/50 Mbps. Most of their passive and active equipment in areas which have been fully "digitalized" is 3.1 compliant, they just need to finish the whole city and then they will start marketing the offer. Modems will have to be changed as well as equipment on the customer's side which they haven't done yet, so it will take quite some time. They "promised" it by the end of 2019. (in 2016.), seems it will be 2025. By that time the Chinese government and Telekom Srbija will have FTTH to every home.

labawi 7y ago
> 300/15 Mbps, which is better than .. 1000/50 Mbps. How is 300/15 better than 1000/50?
- milankragujevic 7y ago
  It's cheaper per megabit ($120 vs $20 per month) and a better DS:US ratio. edit: the ratio is the same, I just haven't powered up my brain yet.
  - jefftk 7y ago
    The ratio is 20/1 in both cases
    - milankragujevic 7y ago
      Oh, I haven't even thought to check. Sorry.
tonyb 7y ago
This doesn't surprise me. Most providers that are deploying DOCSIS 3.1 today are only doing OFDM in the downstream and the upstream is still doing ATDMA (same as DOCSIS 3.0). I'm sure there are some but I don't know of anyone doing 3.1 in the upstream yet. If they did upgrade all their actives then 3.1 upstream is likely in the works. DOCSIS has some pretty amazing diagnostics and troubleshooting - I can look at a modem and say "approximately 71 ft from the modem there is a break in the cable causing an RF impairment" or "These 14 modems in the same neighborhood show the same impairment - there is likely a fault at this specific segment of cable". DOCSIS 3.1 expands on that even more and as more 3.1 CPEs get deployed operators are able to leverage that additional data to get the plant ready for 3.1 upstreams. OFDM frequencies are also not backwards compatible with 3.0 CPEs but a 3.1 CPE can bond both types of channels, so as the ratio of 3.1 CPEs increases that allows operators to shift more frequencies from legacy modulation to newer 3.1 modulation.

avip 7y ago

This kind of comment is why I read HN

fireattack 7y ago

> So the technology is inherently imbalanced. I won't call it inherently, or even "technical reason(s)". Nothing stopped the standard to split the frequency bands for up and downstream in a more way, or even swap the frequencies for each. They're simply configured/designed this way is because of the business reason.

fireattack 7y ago
Typo: "more even way"

tinus_hn 7y ago

Of course cable companies don’t mind turning the internet into a consumer/producer model as well.

snthd 7y ago

>The upstream is also more sustainable to interference and impairments. s/sustainable/susceptible/ ?

doomjunky 7y ago

Why isn't there any dynamic allocation of the up-/downstream channels?

apexalpha 7y ago
From the linked article: ". I should also note that since the cable operators' infrastructure was built around sending the same TV signals to all houses, they basically just run one cable to your neighborhood, and then use passive splitters and dumb amplifiers to split that one cable to all the houses in your neighborhood. So you don't have a dedicated coax cable directly from your house to their headend equipment, so they can't change the frequency split on a house-by-house basis."
tonyb 7y ago
Because of the equipment out in the plant. There are passive devices out in the field that split the upstream and downstream (such as directional couplers). Passive devices are favored over active devices whenever possible because they are much less likely to fail, are less expensive, and require less maintenance.