Comcast begins using subscribers’ home service as public hotspots

Comcast has begun a program where they are turning their home subscribers into public hotspots. The program has begun in Houston and has already been rolled out on 50,000 home subscriber circuits. What this means, in practice, is that every home that subscribes to Comcast and has one of their wireless routers handling the connection now broadcasts another wireless SSID called “xfinitywifi.” Now, any Comcast customer who has connected a device to xfinitywifi anywhere in the past will automatically connect to the wifi being broadcast from someone else’s home as soon as they come within range of the wireless router. This is extending the wireless connectivity of Comcast customers into neighborhoods and residential areas where, previously, wifi was likely unavailable.

While this is all well and good for the roaming Comcast customer, I’m less convinced that it’s good for the home user. Dwight Silverman, writing at the linked Houston Chronicle TechBlog tells us:

Comcast says the hotspot – which appears as “xfinitywifi” to those searching for a Wi-Fi connection – is completely separate from the home network. Someone accessing the Net through the hotspot can’t get to the computers, printers, mobile devices, streaming boxes and more sitting on the host network.

Comcast officials also say that people using the Internet via the hotspot won’t slow down Internet access on the home network. Additional capacity is allotted to handle the bandwidth.

I’m sure that’s the corporate line and there’s likely a lot of effort put into keeping this from impacting the customer that’s paying for the connection. There are ramifications to this move, however, that won’t be easily understood by the average user and appears to be left undiscussed. First let me say that it’s certainly feasible to make a second wireless SSID on a given router. In this case, the home user would be using one SSID (let’s call it “home”) while the roaming users will connect to the other one (in this case, “xfinitywifi”). But does that create a “completely separate” network? By itself, no. When a given wireless router broadcasts 2 SSID’s, this is the electronic equivalent of having 2 houses on the same street with different house numbers. Letters going to house #1 will (if the post office is on the ball) get directed properly and won’t be delivered house #2. The critical part of keeping the networks separate, however, is whether the router is using the same radio frequency to handle the traffic. In our letters on the street metaphor, while the letters for house 1 will get delivered to house 1 and not 2, they are visible to house 2 as they pass by and house 2 can gather information about the letters. Depending on the type of encryption being used on the wireless links and how complex the password is, it’s possible to crack a password within minutes. (And yes, I do know that because I’ve seen it done.)

If Comcast is truly wanting to make sure that they’re separated, that means the public part of the wifi needs to be using a completely different channel than the home part. Which means that every subscriber out there is going to be using 2 channels instead of one. That’s going to become less of a problem as 802.11n gets more widely adopted but it’s still an issue today. In densely-populated residential units like apartments and condos, that can mean a lot of radio overlap and interference, reducing the range and apparent throughput of the wifi. That’s already a problem without making every home double its radio footprint.

The second issue is the idea that this won’t affect a subscriber’s Internet access speed. As I’ve shown, above, this move will almost certainly cause more congestion in the radio spectrum that handles the wifi signals. The “additional capacity” being allotted by Comcast is discussing capacity from the router to the Internet, not from the router to the wireless devices. There’s nothing they can do about the radio spectrum – it’s a public frequency spread. And even restricting that claim to the “wired” side of this equation – by which I mean the connection from the router to the Internet – that implies that the existing connections are capable of carrying more traffic than is currently being allowed. I have no way of knowing whether that’s true and I would imagine Comcast is counting on that.

For Comcast customers, I would simply say that you should run some baseline tests using an online tool, like  Get a couple of readings on different days and different times so you can compare what you have today against what you have after they roll this out in your neighborhood. Comcast, you see, isn’t asking whether it’s OK to make your home a public hotspot. They’re just doing it. They offer you the chance to opt out but they’re not announcing that ability. If you’d like to know how to opt out, follow the link to the blog entry above and you can get details.