单选题What is a benefit of Internet protocol (IP) telephony?（）A Synchronizes password exchanges for call setupB Creates an encrypted tunnel for voice through a Transmission Control Protocol (TCP)/IP networkC Enables two-way voice transmission over a packet-s

TCP/IP(Transmission Control Protoco/Internet Protocol)指传输控制协议。()

TCP/IP is a communication protocol, which provides many different networking services. The TCP/IP Internet protocol suite is formed from two standards: the TCP （Transmission Control Protocol） and the IP（Internet Protocol）.

（72） means it is on the transport layer.

A.ISO

B.IP

C.OSI

D.TCP

●TCP(Transmission Control Protocol)was specifically designed to provide a reliable end-to-end byte stream over a(n) (70) ．

(70) A．IP address

B．reliable network

C．socket

D．unreliable internetwork

【A popular service that has attercted the interest of companies and has home users alike is the sending of voice signals over an IP-based network, such as the Internet. The practice of making telephone calls over the internet has had a number of different names, including packet voice, voice over packet, voice over the internet, internet telephone, and Voice over Ip（Voip）. But it appears the industry has settled on the term”Voice ove IP” in reference to the internet protocol, which controls the transfer of data over the internet. There are currently three ways to deliver VoIp to users, the first technique is found at the corporate level. Many companies are offering VoIP systerms that operate over a 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 large portion of corporate sites have converted their older internal telephone systems to VoIP systems that opreate over a LAN, thus converging two systems into one. A second common solution is the one often encountered at home. Using existing telephones, a special converter 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 that are then sent over an ip connection.The third technique involves smart cell phones. Never cell technologies are all packet-based, thus requiring a telephone call to be converted to digital packets and sending those packets over IP networks.】

From the paragraph above，a popular service that has attracetd the interest of companies and home users,is termed as （） . The data transfer over the Internet is controlled by the （） . At corporate level, many companies have replaced their older internal telephone systerms with （） that oprerate over a local area network.

A、voice over the internet B、voice over packet C、Voice over IP D、internet telephony A、packet B、internet protocol C、industry D、VoIp servers A、VoIP systems B、IP-enablde telephones C、VoIP servers D、routers

●TCP (Transmission Control Protocol) was specifically designed to provide a reliable end-to-end byte stream over a(n)(72).

(72)

A. IP address

B. reliable network

C. socket

D. unreliable internetwork

The Simple Network Management Protocol(SNMP)is an(66)protocol that facilitates the exchange of management information between(67). It is part of the Transmission Control Protocol/Internet Protocol(TCP/IP)protocol suite. SNMP enables network(68)to manage network performance, find and sole network problems, and plan for(69)An SNMP -managed network consists of three key components: managed devices ,(70),and network -management systems .

A．Physical Layer

B．Link Layer

C．Network Layer

D．Transport Layer

The Simple Network Management Protocol (SNMP)is an(71)protocol that facilitates the exchange of management information between(72). It is part of the Transmission Control Protocol/Internet Protocol (TCP/IP) protocol suite. SNMP enables network(73)to manage network performance, find and sole network problems, and plan for(74). An SNMP-man-aged network consists of three key components: managed devices,(75), and network-management systems.

A．Physical Layer

B．Link Layer

C．Network Layer

D．Transport Layer

TCP(Transmission Control Protocol) was specifically designed to provide a reliable end-to-end byte stream over a(n)

A．IP address

B．reliable network

C．socket

D．unreliable internetwork

A.Call management software

B.Media Convergence Servers (MCSs)

C.Voice gateways

D.IP telephones