Glossary
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SIM
Subscriber Identity Module.The SIM provides secure storing of the key identifying a mobile
phone service subscriber but also subscription information, preferences and storage of text
messages.
SIP
Session Initiation Protocol. An application-layer control (signaling) protocol for creating,
modifying, and terminating sessions with one or more participants. Used e.g. for Internet
telephony.
SMS
Short Messaging Service
U
UTC
Coordinated Universal Time. The International Atomic Time (TAI) with leap seconds added at
irregular intervals to compensate for the Earth’s slowing rotation. Leap seconds are used to
allow UTC to closely track UT1, which is mean solar time at the Royal Observatory, Greenwich.
V
VPN
Virtual Private Network. A network that is constructed by using public wires to connect nodes.
You can create networks using the Internet for transporting data, using security mechanisms
so that only authorized users can access the network.
