Tethering

Tethering, or phone-as-modem (PAM), is the sharing of a mobile device's internet connection with other wirelessly connected computers. Connection of a mobile phone or tablet computer with other devices can be done over wireless LAN (Wi-Fi), over Bluetooth or by physical connection using a cable, for example through USB.

If tethering is done over WLAN, the feature may be branded as a mobile hotspot, which allows the smartphone to serve as a portable router. Mobile hotspots may be protected by a PIN or password. The Internet-connected mobile device can act as a portable wireless access point and router for devices connected to it.

Many mobile phones are equipped with software to offer tethered Internet access. Windows Mobile 6.5, Windows Phone 7, Android (starting from version 2.2), and iOS 3.0 (or later) offer tethering over a Bluetooth PAN or a USB connection. Tethering over Wi-Fi, also known as Personal Hotspot, is available on iOS starting with iOS 4.2.5 (or later) on iPhone 4, 4S (2010), 5, iPad (3rd generation), certain Windows Mobile 6.5 devices like the HTC HD2, Windows Phone 7, 8 and 8.1 devices (varies by manufacturer and model), and certain Android phones (varies widely depending on carrier, manufacturer, and software version).

For IPv4 networks, the tethering normally works via NAT on the handset's existing data connection, so from the network point of view, there is just one device with a single IPv4 network address, though it is technically possible to attempt to identify multiple machines.

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