5 ms·

I would be curious to learn how this is done technically: would the "owner" connections and public hotspot wifi connections share the same IP or not? If the IP

by lsh123 12y ago

I would be curious to learn how this is done technically: would the "owner" connections and public hotspot wifi connections share the same IP or not? If the IP is shared then there will be some interesting issues to be resolved if someone connects to a public hotspot, fires up Torrent client, downloads tons of movies, and then the owner of the hotspot gets the takedown notice or there will be charges against the owner for downloading copyrighted material. And you can imagine other cases from child pornography to financing terrorists.

spike021 12y ago
You still need to login to the Comcast wifi using an Xfinity account, so I'd imagine activity is tracked that way.
- lsh123 12y ago
  Not sure how this would help. The server will only see IP address. The Comcast will know that a given set of users had the session open on the hotspot. But unless the hotspot sends detailed information about every packet to Comcast with session/user mapping, there is no way to map a particular request to a session/user.
  - jsz0 12y ago
    The router simply maps different networks to different SSIDs: SSID customer-net = VLAN1, nat VLAN1 192.168.1.0/24 to WAN-IP1 SSID public-net = VLAN2, nat VLAN2 192.168.2.0/24 to WAN-IP2
    - lsh123 12y ago
      Sure. Having different IPs definitely helps (this was my original question if IPs will be different or not). The login to Comcast by itself doesn't help.
      - sliverstorm 12y ago
        I believe authentication is usually handled with MAC addresses. I'm not a network engineer, but I've worked under one and professional equipment has a lot of capabilities for identifying & handling cases exactly like these; don't infer all of the network devices are as rudimentary as a WRT54G
        lsh123 12y ago
        MAC address is used in APR protocol and it doesn't go beyond your router/WAP/DHCP server. The only thing that an "external" server sees is the IP address.
        jsz0 12y ago
        ISP managed gateways provide visibility to the ARP table via SNMP or TR-69.
jsz0 12y ago
Cable modems can be configured to support multiple service flows with different classes of service. The users of the public hotspot network have a unique IP and separate service flows provisioning additional bandwidth to the modem. Presumably Comcast is also tracking an authenticated user's IP address while on public hotspots for DMCA enforcement purposes.
- jrockway 12y ago
  Though there's very little stopping you from setting up an access point called "XfinityWifi" and connecting it to whatever evil you want.
  - jsz0 12y ago
    This is a very legitimate concern. I doubt Comcast or any other ISP using these community wifi services are really prepared to deal with this problem. Any Comcast customer who runs into problems with DMCA / legal issues (via IP) will have plenty of reasonable doubt on their side.
brudgers 12y ago
Typically a cable company provided cable modem is a NAT box rather rather than having a dedicated IP. It's IP within the cable company's backbone gets encoded/decoded to an IP:port where it exits their network so that all their customers can be serviced by a static block of IP addresses (of which there are essentially no more IPv4. To share the cable modem device, the device just needs to switch packets internally.

by lsh123 12y ago

spike021 12y ago

You still need to login to the Comcast wifi using an Xfinity account, so I'd imagine activity is tracked that way.

lsh123 12y ago
Not sure how this would help. The server will only see IP address. The Comcast will know that a given set of users had the session open on the hotspot. But unless the hotspot sends detailed information about every packet to Comcast with session/user mapping, there is no way to map a particular request to a session/user.
- jsz0 12y ago
  The router simply maps different networks to different SSIDs: SSID customer-net = VLAN1, nat VLAN1 192.168.1.0/24 to WAN-IP1 SSID public-net = VLAN2, nat VLAN2 192.168.2.0/24 to WAN-IP2
  - lsh123 12y ago
    Sure. Having different IPs definitely helps (this was my original question if IPs will be different or not). The login to Comcast by itself doesn't help.
    - sliverstorm 12y ago
      I believe authentication is usually handled with MAC addresses. I'm not a network engineer, but I've worked under one and professional equipment has a lot of capabilities for identifying & handling cases exactly like these; don't infer all of the network devices are as rudimentary as a WRT54G
      - lsh123 12y ago
        MAC address is used in APR protocol and it doesn't go beyond your router/WAP/DHCP server. The only thing that an "external" server sees is the IP address.
        jsz0 12y ago
        ISP managed gateways provide visibility to the ARP table via SNMP or TR-69.

jsz0 12y ago

Cable modems can be configured to support multiple service flows with different classes of service. The users of the public hotspot network have a unique IP and separate service flows provisioning additional bandwidth to the modem. Presumably Comcast is also tracking an authenticated user's IP address while on public hotspots for DMCA enforcement purposes.

jrockway 12y ago
Though there's very little stopping you from setting up an access point called "XfinityWifi" and connecting it to whatever evil you want.
- jsz0 12y ago
  This is a very legitimate concern. I doubt Comcast or any other ISP using these community wifi services are really prepared to deal with this problem. Any Comcast customer who runs into problems with DMCA / legal issues (via IP) will have plenty of reasonable doubt on their side.

brudgers 12y ago

Typically a cable company provided cable modem is a NAT box rather rather than having a dedicated IP. It's IP within the cable company's backbone gets encoded/decoded to an IP:port where it exits their network so that all their customers can be serviced by a static block of IP addresses (of which there are essentially no more IPv4. To share the cable modem device, the device just needs to switch packets internally.