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Can anyone explain to me what the marginal costs are for additional traffic, within Comcast's network? I presume that once you're powering the routers, they co

Can anyone explain to me what the marginal costs are for additional traffic, within Comcast's network? I presume that once you're powering the routers, they consume pretty equivalent power at peak and off-peak times, but maybe that's a faulty assumption?

sliverstorm 12y ago
As I understand it the marginal cost of the first N gigabytes is approximately zilch, but N+1 gigabytes is $$$$- because they now have to upgrade the infrastructure. The price tags they put on more data are almost certainly an attempt at "market allocation" rather than the actual cost of the data. In other words, the increased price on bandwidth lowers demand, hopefully to the level Comcast is targeting. Think of electricity companies, and off-peak rates. They charge more during peak load to drive the market to shift more load to off-peak times.
- al_bundling 12y ago
  > As I understand it the marginal cost of the first N gigabytes is approximately zilch, but N+1 gigabytes is $$$$- because they now have to upgrade the infrastructure. Missed out a step there. It's not zero then suddenly $$$$. It's more a question of gradual, usually low cost, equipment upgrades. All backhaul is via fiber optics, so by switching optics you go from 1G/10G/100G to multiple 1G/10G/100G waves. You might need a new router blade or a bigger chassis at some point. Only if you really messed up do you need infrastructure upgrades. This might mean splitting nodes, i.e. pulling a bit more fiber to hotspots, but that is why you have spare empty conduits and excess fiber strands in your cables. If you don't then you truly deserve all the misery you brought upon yourself.
ams6110 12y ago
I would make the same assumption. The issue is they oversubscribe their capacity. And rather than upgrade their network to actually support what they sold, they want to introduce usage caps.
- kstrauser 12y ago
  Everyone does. That's standard in the trade, because not everyone will be using their connection at the same time. There are huge savings in only buying enough bandwidth to handle, say, your 95% load and not enough to satisfy all of your customers at once. My problem is that the ISP I work at had about a 10:1 oversubscription ratio. Comcast wants to fine individual customers who exceed 70:1, so they're probably aiming for a 200:1 overall ratio. That's just highway robbery.
  - al_bundling 12y ago
    > There are huge savings in only buying enough bandwidth to handle, say, your 95% load and not enough to satisfy all of your customers at once. It's bad engineering to run your links hot at 95%. (Here's looking at you, Comcast) You want to keep link usage at under 50% in order to have adequate margin for growth, be able to fall over to your secondary links without saturating them for maintenance/repairs/emergencies and handle microbursts which don't show up on the 5 minute average timescales monitoring is done at.
    - kstrauser 12y ago
      By that, I meant 95th percentile. That's the number you'd usually add your safety padding to.
      - al_bundling 12y ago
        My bad, I misread your point, but in hindsight it's quite obvious what you meant from the context. Wording was a bit ambiguous tho.
        kstrauser 12y ago
        I knew what I meant, darn it! :-D
  - Aloha 12y ago
    Part of the problem is adding capacity in an HFC network is expensive and difficult, eventually adding more carriers is not enough, and you needs to break the broadcast domain down even further, which means adding a new node - sometimes that can be just adding cards to a cabinet, others its a new physical box that must be permitted and placed - a process that can (and often does) take years. xDSL has it easy, they can just turn up more backhaul at the CO, which is often a process that takes no more that days, if not hours.
al_bundling 12y ago
> Can anyone explain to me what the marginal costs are for additional traffic, within Comcast's network? Marginal costs within the design capacity of the network are close to zero. If the traffic happens to be external, to a network Comcast pays transit to (if such exist) and it's in a direction that's billable (transit is paid in the direction that is larger) then the wholesale rate (for that fraction of the traffic) would be billed at about 0.1 cents per GB.

sliverstorm 12y ago

As I understand it the marginal cost of the first N gigabytes is approximately zilch, but N+1 gigabytes is $$$$- because they now have to upgrade the infrastructure. The price tags they put on more data are almost certainly an attempt at "market allocation" rather than the actual cost of the data. In other words, the increased price on bandwidth lowers demand, hopefully to the level Comcast is targeting. Think of electricity companies, and off-peak rates. They charge more during peak load to drive the market to shift more load to off-peak times.

al_bundling 12y ago
> As I understand it the marginal cost of the first N gigabytes is approximately zilch, but N+1 gigabytes is $$$$- because they now have to upgrade the infrastructure. Missed out a step there. It's not zero then suddenly $$$$. It's more a question of gradual, usually low cost, equipment upgrades. All backhaul is via fiber optics, so by switching optics you go from 1G/10G/100G to multiple 1G/10G/100G waves. You might need a new router blade or a bigger chassis at some point. Only if you really messed up do you need infrastructure upgrades. This might mean splitting nodes, i.e. pulling a bit more fiber to hotspots, but that is why you have spare empty conduits and excess fiber strands in your cables. If you don't then you truly deserve all the misery you brought upon yourself.

ams6110 12y ago

I would make the same assumption. The issue is they oversubscribe their capacity. And rather than upgrade their network to actually support what they sold, they want to introduce usage caps.

kstrauser 12y ago
Everyone does. That's standard in the trade, because not everyone will be using their connection at the same time. There are huge savings in only buying enough bandwidth to handle, say, your 95% load and not enough to satisfy all of your customers at once. My problem is that the ISP I work at had about a 10:1 oversubscription ratio. Comcast wants to fine individual customers who exceed 70:1, so they're probably aiming for a 200:1 overall ratio. That's just highway robbery.
- al_bundling 12y ago
  > There are huge savings in only buying enough bandwidth to handle, say, your 95% load and not enough to satisfy all of your customers at once. It's bad engineering to run your links hot at 95%. (Here's looking at you, Comcast) You want to keep link usage at under 50% in order to have adequate margin for growth, be able to fall over to your secondary links without saturating them for maintenance/repairs/emergencies and handle microbursts which don't show up on the 5 minute average timescales monitoring is done at.
  - kstrauser 12y ago
    By that, I meant 95th percentile. That's the number you'd usually add your safety padding to.
    - al_bundling 12y ago
      My bad, I misread your point, but in hindsight it's quite obvious what you meant from the context. Wording was a bit ambiguous tho.
      - kstrauser 12y ago
        I knew what I meant, darn it! :-D
- Aloha 12y ago
  Part of the problem is adding capacity in an HFC network is expensive and difficult, eventually adding more carriers is not enough, and you needs to break the broadcast domain down even further, which means adding a new node - sometimes that can be just adding cards to a cabinet, others its a new physical box that must be permitted and placed - a process that can (and often does) take years. xDSL has it easy, they can just turn up more backhaul at the CO, which is often a process that takes no more that days, if not hours.

al_bundling 12y ago

> Can anyone explain to me what the marginal costs are for additional traffic, within Comcast's network? Marginal costs within the design capacity of the network are close to zero. If the traffic happens to be external, to a network Comcast pays transit to (if such exist) and it's in a direction that's billable (transit is paid in the direction that is larger) then the wholesale rate (for that fraction of the traffic) would be billed at about 0.1 cents per GB.