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 many Wi-Fi hotspots, and 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. Depending on the feature set of the gateway, multiple web servers can be whitelisted (say for iframes or links within the login page). In addition to whitelisting the URLs of web hosts, some gateways can whitelist TCP ports. The MAC address of attached clients can also be set to bypass the login process.
Read more about Captive Portal: Software Captive Portals, Limitations
Famous quotes containing the words captive and/or portal:
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Crooning ditties treasured well
From his Afric’s torrid plains.
Sole estate his sire bequeathed,—
Hapless sire to hapless son,—
Was the wailing song he breathed,
And his chain when life was done.”
—Ralph Waldo Emerson (1803–1882)
“Some sepulcher, remote, alone,
Against whose portal she hath thrown,
In childhood, many an idle stone—
Some tomb from out whose sounding door
She ne’er shall force an echo more,
Thrilling to think, poor child of sin!
It was the dead who groaned within.”
—Edgar Allan Poe (1809–1849)