[A popular service that has attracted the interest of companies and home users alikeis the sending of voice signals over an IP-based network such as the Internet.The practiceof making telephone calls over the Internet has had a number of different names,includingpacket voice,voice over packet,voice over the Internet,Internet telephony,and Voiceover IP（VoIP）.But it appears the industry has settled on the term"Voice over IP"inreference to the Internet Protocol,which controls the transfer of data over theInternet.There are currently three ways to deliver VoIP to users.The first technique isfound at the corporate level.Many companies are offering VoIP systems that operate overa local area network.These systems involve a fair amount of equipment,such as VoIP servers,special IP-enabled telephones,and routers that can direct telephone calls.Today,a largeportion of corporate sites have converted their older internal telephone systems to VoIPsystems that operate over a LAN,thus converging two systems into on E.A second commonsolution is the one often encountered at homE.Using existing telephones,a specialconverter is added between the telephone and a high-speed Internet（DSL or cable modem）connection.The converter digitizes the voice signal and creates a stream of packets thatare then sent over an IP connection.The third technique involves smart cell phones.Newercell phone technologies are all packet-based,thus requiring a telephone call to beconverted to digital packets and sending those packets over IP networks.]
From the paragraph above,a popular service that has attracted the interest ofcompanies and home users,is termed as（1）.The data transfer over the Internet iscontrolled by the（2）.At corporate level,many companies have replaced their olderinternal telephone systems with（3）that operate over a local area network.______.

A.VoIP systems

B.IP-enabled telephones

C.VoIP servers

D.routers