Equipment Providers Captive Portal (Firewall)
Captive portal
The captive portal technique forces an HTTP client on a network to see a special web page (usually for authentication purposes) before using the Internet normally. A captive portal turns a Web browser into an authentication device. This is done by intercepting all packets, regardless of address or port, until the user opens a browser and tries to access the Internet. At that time the browser is redirected to a web page which may require authentication and/or payment, or simply display an acceptable use policy and require the user to agree. Captive portals are used at most Wi-Fi hotspots, and it can be used to control wired access (e.g. apartment houses, hotel rooms, business centers, "open" Ethernet jacks) as well.Since the login page itself must be presented to the client, either that login page is locally stored in the gateway, or the web server hosting that page must be "whitelisted" via a walled garden to bypass the authentication process.
More info Wikipedia
http://en.wikipedia.org/wiki/Captive_portal
and
http://www.kenitfirewall.com/
