【正文】 data transfer service makes sure that neither side of a connection overwhelms the other side by sending toomany packets too fast. The sentence describes (A). control service data transfer helps prevent the Internet from entering a state of gridlock. When a packet switch bees congested, its buffers can overflow and packet loss can occur. The sentence describes (B). control service data transfer Internet’s connectionoriented service has a name, it is (A). the following options, which service does not be provided to an application by TCP? (C) transport control conferencing control Internet’s connectionless service is called (B). the following options, which does not use TCP? (B) telephone the following options, which does not use UDP? (D) phone conferencing multimedia are two fundamental approaches to building a network core, (B) and packet switching. current switching switching switching switching (C) networks, the resources needed along a path to provide for munication between the end system are reserved for the duration of the munication session. (A) networks, the resources are not reserved。 a session’s messages use the resources on demand, and as a consequence, may have to wait for access to munication link. a circuitswitched network, if each link has n circuits, for each link used by the endtoend connection, the connection gets (A) of the link’s bandwidth for the duration of the connection. fraction 1/n times (C), the transmission rate of a circuit is equal to the frame rate multiplied by the number of bits in a slot. network 44.(B) means that the switch must receive the entire packet before it can begin to transmit the first bit of the packet onto the outbound link. delay transmission loss network that forwards packets according to host destination addresses is called (D) network. network that forwards packets according to virtualcircuit numbers is called (C) network. the following entries, which is not a kind of access network? (D) access access access access there is exactly one packet switch between a sending host and a receiving host. The transmission rates between the sending host and the switch and between the switch and the receiving host are R1 and R2, respectively. Assuming that the switch uses storeandforward packet switching, what is the total endtoend delay to send a packet of length L? (Ignore queuing delay, propagation delay, and processing delay.) (A)＋L/R2 of the above time required to examine the packet’s header and determine where to direct the packet is part of the (B). delay delay delay delay time required to propagate from the beginning of the link to the next router is (C). delay delay delay delay sending a packet of 3000bits over a path of 5 links. Each link transmits at 1000bps. Queuing delays, propagation delay and processing delay are negligible. (6 points)(1).Suppose the network is a packetswitched virtual circuit network. VC setup time is seconds. Suppose the sending layers add a total of 500 bits of header to each packet. How long does it take to send the file from source to destination?t=5*(3000+500)/1000+=(2).Suppose the network is a packetswitched datagram network and a connectionless service is used. Now suppose each packet has 200 bits of header. How long does it take to send the file?t=5*(3000+200)/1000=16s(3).Suppose that the network is a circuitswitched network. Further suppose that the transmission rate of the circuit between source and destination is 200bps. Assuming setup time and 200 bits of header appended to the packet, how long does it take to send the packet?t=(3000+200)/200+=Chapter 2 Application Layer the following four descriptions, which one is correct? C/S architecture, clients municate with each other directly. C/S architecture, client has a fixed wellknown address. P2P architecture, peers municate with each other directly. P2P architecture, peer has a fixed wellknown address. the context of a munication session between a pair of process, the process that initiates the munication is labeled as the , the process that waits to be contacted to begin the session is labeled as the . process, server process process, receiving process process, output process process, connecting process socket is the interface between within a host. network layer and the link layer link layer and the physical layer application layer and the transport layer transport layer and the network layer the following applications, which one is a losstolerant application? transfer messaging audio the following applications, which one is a bandwidthsensitive application? application audio transfer service of TCP can’t guarantee . of all data without error of all data in the proper order rate of delivery control the following applications, which one uses UDP? application transfer the following descriptions about HTTP, which one is not correct? uses nonpersistent conn