1、3. The network layer in the Internet provides _.A) comprehensive error and flow control.B) limited error control, but no flow control.C) comprehensive error control but limited flow control.4. In a virtual-circuit approach, the forwarding decision is based on the value of the _ field in the packet h
2、eader.A) source addressB) destination addressC) labelD) None of the choices are correct5. In a datagram approach, the forwarding decision is based on the value of the _ field in the packet header.6. The performance of a network can be measured in terms of _.A) delayB) throughputC) packet lossD) all
3、of the choices are correct7. Transmission delay (time) is the ratio of _.A) transmission rate to packet lengthB) transmission rate to distanceC) packet length to transmission rateD) processing time to transmission rate8. Propagation delay (time) is the ratio of _.A) transmission rate to propagation
4、speedB) propagation speed to distanceC) packet length to propagation speedD) distance to propagation speed9. When the load in the network reaches the network capacity, the packet delay _ and the network throughput reaches _.A) increases sharply; its minimumB) increases sharply; its maximumC) decreas
5、es sharply;D) decreases sharply;10. In open-loop congestion control, policies are applied _.A) to prevent congestion before it happensB) to alleviate congestion after it happensC) to either prevent congestion before it happens or to alleviate congestion after it happens11. The _ technique is one of
6、the open-loop congestion policyA) backpressureB) choke packetC) implicit signaling12. The _ technique is one of the close-loop congestion policyA) acknowledgment policyC) discarding policy13. IP is a _ protocol.A) connection-oriented unreliableB) connection-oriented reliableC) connectionless unrelia
7、bleD) connectionless reliable14.An HLEN value of decimal 10 means _.A) there are 10 bytes of optionsB) there are 10 bytes in the headerC) there are 40 bytes of optionsD) there are 40 bytes in the header15. If the fragment offset has a value of 100, it means that _.A) the datagram has not been fragme
8、ntedB) the datagram is 100 bytes in sizeC) the first byte of the datagram is byte 80016. What is needed to determine the number of the last byte of a fragment?A) offset numberB) total lengthC) both offset number and the total length17. The IP header size is _ bytes long.A) 20 to 60B) 20C) 6018. Pack
9、ets in the IP layer are called _.A) segmentsB) datagramsC) frames19. The total length field defines the total length of the datagram _.A) including the headerB) excluding the headerC) excluding the option length20. When a datagram is encapsulated in a frame, the total size of the datagram must be le
10、ss than the _.A) MUTB) MATC) MTU21. An IPv4 address is normally represented in base _ in dotted-decimal notation.A) 16B) 256C) 1022. In classful addressing, the IPv4 address space is divided into _ classes.A) 3B) 4C) 523. The number of addresses assigned to an organization in classless addressing _.
11、A) can be any numberB) must be a multiple of 256C) must be a power of 224. The first address assigned to an organization in classless addressing _.A) must be evenly divisible by the number of addresses in the organizationB) must be divisible by 128C) must belong to one of the A, B, or C classes25. In subnetting, the number of addresses in each subnet must _.A) be a power of 2B) be a mu
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