Is one of message forms via the Internet; you only have to press the
icon or button on the site and the connection with the operator will follow
immediately. This function is often used on the websites for a quick
connection.
SIP-addressing is logical, of the same type as URL in HTTP. And the most natural – to use the electronic mail as the SIP address. There are permissible varied parameters by the address: for example, it is possible to indicate the regular city telephone number, additional telephone, and the parameters of modem connection etc.