5 ms·

Note for comcast customers: the default on your setup is devote one fifth of your modem capacity to general xfinity wifi. So the general public can surf porn at

Note for comcast customers: the default on your setup is devote one fifth of your modem capacity to general xfinity wifi. So the general public can surf porn at your expense. Xfinity has settings to turn this off. However like Facebook privacy, comcast continuously turns this back on.

LeoPanthera 7y ago
This is misleading. It doesn't share bandwidth on the cable with your internet connection. Removing it wouldn't make your interest faster.
- lotsofpulp 7y ago
  Where is the bandwidth coming from? Coax in general is sharing bandwidth between the whole neighborhood, hence the piss poor upload speeds and latency. Obviously all bandwidth is shared at some point, but the extend to which coax is is ridiculous in my experience. They sell individuals hundreds of megabits download, 5 “megabit” upload, when the whole neighborhood might only have a few hundred megabits download capacity total. It’s a joke compared to symmetric fiber connections, and that they share even more of your connection with their xfinitywifi adds to that. Hence why one should always buy and use your own cable modem.
  - rayiner 7y ago
    This is a little bit off. Looking at an actual comcast channel map: https://pickmymodem.com/ofdm-sub-carrier-ranges-on-docsis-3-1-cable-modem https://pickmymodem.com/ofdm-sub-carrier-ranges-on-docsis-3-.... The 24 DOCSIS 3.0 channels are about a gigabit in the aggregate, and the 94 MHZ OFDM channel is about another gigabit. Compared to 2.4 gbps down for GPON. (GPON is a decade older tech, so not surprising.) There will be more people on a cable node than on a GPON (which is typically 16-32). But Comcast is N+0 on its DOCSIS 3.1 footprint (which is 75% of its network). That means they’ve removed amplifiers that extend the signal of the cable over distances, because those amplifiers get in the way of more aggressive techniques used in DOCSIS 3.1. That requires pushing fiber deeper into the network, and has the side effect of reducing how many subscribers are in each shared bus. The upload limits are more an issue of legacy channel maps than insufficient bandwidth on the wire. The upstream/downstream portions are separated into different portions of the RF spectrum, and for historical reasons the split is heavily biased toward downstream. But symmetric DOCSIS is around the corner. There is also a lot of headroom left in DOCSIS 3.1. Compatible cable modems must support a minimum 192 MHz OFDM channels, which is almost 4 gbps. 10 gbps is possible if all the bandwidth on the coax is used for data rather than TV.
    - lotsofpulp 7y ago
      Appreciate the information regarding specs. My observations are from repeated exposures on east and west coast of US to Comcast cable connections, which are noticeably slower in the evening when there is more network congestion, and have terrible latency. Various speed tests give me only a fraction of advertised bandwidth, and even then, it won’t be sustained. It feels like they’ve programmed the system to allow new connections to have a burst of bandwidth, and then taper it down. I have yet to experience a coax internet experience as reliable and pleasant to use as a symmetric fiber connection. I presume it’s because Comcast is overselling their capacity, because they’re Comcast.
      - mikeash 7y ago
        Your feeling is spot on. They definitely burst to a higher speed at the beginning of a transfer. What’s really amazing is that they’re proud of it! https://corporate.comcast.com/comcast-voices/what-is-powerboost https://corporate.comcast.com/comcast-voices/what-is-powerbo...
        rayiner 7y ago
        Apple and Intel seem pretty proud of their burst speeds too. (And battery life, which is quoted based on running the CPU at short bursts and then going idle.) And why shouldn’t they be? Consumer tech is properly optimized for burst usage. The network delivers the 10MB home page in a burst, then goes idle. The CPU bursts to 4 GHz to render it as fast as possible, then goes idle. The battery delivers 35W for half a second, then drops down to 5W. The whole system is designed around that usage profile.
        mikeash 7y ago
        The difference is that CPUs burst above the speed they can sustain. The alternative would be running slower all the time. Comcast, in contrast, just lets you use more of their otherwise idle capacity, then throttles you. The alternative would be getting the full capacity of their network all the time.
skinnymuch 7y ago
Can you show where this is true? I’ve been trying to get the WiFi part enabled. Have had a hard time on current and last router. The opposite of it being enabled by default.
u801e 7y ago
Does this apply if you're using your own modem/router?
- colanderman 7y ago
  No. (Source: I've used my own modem & router with Comcast. There's no physical way they can force your router to host an xfinitywifi SSID.)
- MrMember 7y ago
  I bought my own modem and router specifically to not deal with this garbage.

LeoPanthera 7y ago

This is misleading. It doesn't share bandwidth on the cable with your internet connection. Removing it wouldn't make your interest faster.

lotsofpulp 7y ago
Where is the bandwidth coming from? Coax in general is sharing bandwidth between the whole neighborhood, hence the piss poor upload speeds and latency. Obviously all bandwidth is shared at some point, but the extend to which coax is is ridiculous in my experience. They sell individuals hundreds of megabits download, 5 “megabit” upload, when the whole neighborhood might only have a few hundred megabits download capacity total. It’s a joke compared to symmetric fiber connections, and that they share even more of your connection with their xfinitywifi adds to that. Hence why one should always buy and use your own cable modem.
- rayiner 7y ago
  This is a little bit off. Looking at an actual comcast channel map: https://pickmymodem.com/ofdm-sub-carrier-ranges-on-docsis-3-1-cable-modem https://pickmymodem.com/ofdm-sub-carrier-ranges-on-docsis-3-.... The 24 DOCSIS 3.0 channels are about a gigabit in the aggregate, and the 94 MHZ OFDM channel is about another gigabit. Compared to 2.4 gbps down for GPON. (GPON is a decade older tech, so not surprising.) There will be more people on a cable node than on a GPON (which is typically 16-32). But Comcast is N+0 on its DOCSIS 3.1 footprint (which is 75% of its network). That means they’ve removed amplifiers that extend the signal of the cable over distances, because those amplifiers get in the way of more aggressive techniques used in DOCSIS 3.1. That requires pushing fiber deeper into the network, and has the side effect of reducing how many subscribers are in each shared bus. The upload limits are more an issue of legacy channel maps than insufficient bandwidth on the wire. The upstream/downstream portions are separated into different portions of the RF spectrum, and for historical reasons the split is heavily biased toward downstream. But symmetric DOCSIS is around the corner. There is also a lot of headroom left in DOCSIS 3.1. Compatible cable modems must support a minimum 192 MHz OFDM channels, which is almost 4 gbps. 10 gbps is possible if all the bandwidth on the coax is used for data rather than TV.
  - lotsofpulp 7y ago
    Appreciate the information regarding specs. My observations are from repeated exposures on east and west coast of US to Comcast cable connections, which are noticeably slower in the evening when there is more network congestion, and have terrible latency. Various speed tests give me only a fraction of advertised bandwidth, and even then, it won’t be sustained. It feels like they’ve programmed the system to allow new connections to have a burst of bandwidth, and then taper it down. I have yet to experience a coax internet experience as reliable and pleasant to use as a symmetric fiber connection. I presume it’s because Comcast is overselling their capacity, because they’re Comcast.
    - mikeash 7y ago
      Your feeling is spot on. They definitely burst to a higher speed at the beginning of a transfer. What’s really amazing is that they’re proud of it! https://corporate.comcast.com/comcast-voices/what-is-powerboost https://corporate.comcast.com/comcast-voices/what-is-powerbo...
      - rayiner 7y ago
        Apple and Intel seem pretty proud of their burst speeds too. (And battery life, which is quoted based on running the CPU at short bursts and then going idle.) And why shouldn’t they be? Consumer tech is properly optimized for burst usage. The network delivers the 10MB home page in a burst, then goes idle. The CPU bursts to 4 GHz to render it as fast as possible, then goes idle. The battery delivers 35W for half a second, then drops down to 5W. The whole system is designed around that usage profile.
        mikeash 7y ago
        The difference is that CPUs burst above the speed they can sustain. The alternative would be running slower all the time. Comcast, in contrast, just lets you use more of their otherwise idle capacity, then throttles you. The alternative would be getting the full capacity of their network all the time.

skinnymuch 7y ago

Can you show where this is true? I’ve been trying to get the WiFi part enabled. Have had a hard time on current and last router. The opposite of it being enabled by default.

u801e 7y ago

Does this apply if you're using your own modem/router?

colanderman 7y ago
No. (Source: I've used my own modem & router with Comcast. There's no physical way they can force your router to host an xfinitywifi SSID.)
MrMember 7y ago
I bought my own modem and router specifically to not deal with this garbage.