end-to-end delay
interference from bulk data traffic
processing delays
serialization delays
jitter
第1题：
A.Centrex
B.Packet encryption
C.Intelligent call routing
D.QoS
第2题：
【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
第3题：
To maintain a telephone conversation over the Internet. The voice packets must arrive at their destination in ()
A.a continuous stream
B.a burst stream
C.a delayed stream
D.a burst mode
第4题：
Refer to the exhibit. A router has a 256 kbps Frame Relay circuit connected to interface serial 0/0. As a large FTP packet is being placed into the hardware transmit queue of interface serial 0/0， a voice packet is placed into the priority queue of that interface. How， and in what order， wi the packets be transmitted？（）
第5题：
Ensuring that data is transmitted securely over an IP network is the main purpose of：（）
第6题：
When we use VolP service，the voice packets over the Internet arrive at their destination in a（ ） stream.
A.burst B.delayed C.interrupted D.continuous
第7题：
Which three statements are true about the data traffic characteristics of voice traffic？ （）
第8题：
Flow control is a function that prevents network congestion by ensuring that(66)do not over-whelm(67)with data. There are three commonly used methods for handling network congestion.(68)is used by network devices to temporarily store bursts of excess data in memory until they can be processed.(69)are used by receiving devices to help prevent their buffers from overflowing.(70)is a flow-control scheme in which the source device requires an acknowledgment from the destination after a certain number of packets have been transmitted.
A．transmitting devices
B．transmitted devices
C．receiving devices
D．received devices
第9题：
Which two statements are true about voice packets in a LAN？ （Choose two.） （）
第10题：
Which two statements are true about Voice over IP （VoIP） packet delivery in a digital infrastructure？ （）