计算机网络复习题一、单项选择1.Which of following is not an application-layer protocol? ( B)A. HTTPB. TCPC.SMTPD.FTP2.The PDU of network-layer is called ( C).A. messageB. segmentC. datagramD. frame3. An HTTP client often uses the (B ) method when the user fills out a form.A.GETB. POSTC. HEADD. PUT4.The default port number of DNS is(C )A.80B.21C.53D.255.Which of the following is not a mail access protocol? ( C)A.POP3B.IMAPC.HTTPD.SMTP6.Which protocol is not a network-layer protocol? (C )A.ICMP ProtocolB.routing protocolC.PPPD.IP Protocol7.The SYN segment is used for(B ).A. TCP flow controlB. TCP connection setupC. TCP congestion controlD. Closing a TCP connection8.Which field in a TCP segment is used for flow control? ( A)A. receive windowB. sequence numberC. acknowledgementD. Internet checksum9.A (A ) is the interface between the application layer and the transport layer within a host.A. socketB. bridgeC. EthernetD. hub10.In network-layer, which protocol is used for reporting errors? ( B)A.SMTPB.ICMPC.ARPD.CSMA11.Which protocol is an intra-autonomous system routing protocol? ( D)A. ARPB. ICMPC. BGPD. RIP12.MAC address is ( B) bits long.A.32B.48C.128D.6413. ( A ) 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.A. store-and-forward transmissionB. FDMC. end-to-end connectionD. TDM14. In the following four descriptions, which one is correct? ( C )A In C/S architecture, clients communicate with each other directly.B In C/S architecture, client has a fixed well-known address.C In P2P architecture, peers communicate with each other directly.D In P2P architecture, peer has a fixed well-known address.15．Which of following is not an application-layer protocol? ( B )A. HTTPB. TCPC. DNSD. SMTP16. ( B ) header line indicates the time and date when the object was created or last modified.A. Date:B. Last-Modified:C. Connection:D.If-Modified-Since:17．A ( A ) provides logical communication between processes runningon different hosts. A ( ) provides logical communication between hosts.A. transport-layer protocol, network-layer protocolB. network-layer protocol, transport-layer protocolC. transport-layer protocol, application-layer protocolD. network-layer protocol, link-layer protocol18．Suppose TCP sender is in slow start state and the CongWin is8, then what’s the value of CongWin after one RTT? ( D )A. 9B. 10C. 4D. 1619．( B ) header allows the receiving user agent to take an appropriate action on the message.A. Content-Transfer-Encoding:B. Content-Type:C. From:D. To:20. The request message in the conditional GET must include the header line.Cst-Modifiedst-ReferencedC.If-Modified-SinceD.If –Referenced-Since21. Which of the following services is not provided by TCP? （A）A.Delay guarantees and bandwidth guaranteesB.Reliable data transferC.Congestion controlD.Flow control22. In the LAN,（C ）protocol dynamically assign IP addresses to hosts.A.DNSB.ARPC.DHCPD.IP23. ___A_ is the ability to determine the interfaces to which a frame should be directed, and then directing the frame to those interfaces.A.ForwardingB.FilteringC.RoutingD.Switching24. Which of the following is not a routing protocol?（ A）A.TCPB.RIPC.OSPFD. BGP25. For 10BaseT, the maximum length of the connection between an adapterand the hub is A meters.A.100B.200C.500D.1026. In a TCP segment, ___A_ is the byte-stream number of the first bytein the segment.A.sequence numberB.aCK numberC.checksumD.port number27. A ( A ) provides logical communication between processes runningon different hosts. A ( ) provides logical communication between hosts.A. transport-layer protocol, network-layer protocolB. network-layer protocol, transport-layer protocolC. transport-layer protocol, application-layer protocolD. network-layer protocol, link-layer protocol二、填空1. A total nodal delay includes nodal processing delay, queuing delay,transmission delay , and propagation delay.2.In the context of a communication session between a pair of processes,the process that initiates the communication is labeled as the client . The process that waits to be contacted to begin the sessionis the server .3. A process sends messages into ,and receives messages from, thenetwork through its socket .4.FTP uses two parallel TCP connections to transfer a file, they aredata connection and control connection .5. DNS protocol translates hostname to IP address.6. A transport-layer protocol provides logical communication betweenprocesses running on different hosts. A network-layer protocolprovides logical communication between hosts .7.In IPv6 datagram format, IP address is 128 bits long.8.There are three 16-bit words: 0110011001100000, 0101010101010101,1000111100001100. Their checksum is 1011 0101 0011 1101 .9.RcvBuffer=100, LastByteRcvd=58, LastByteRead=23, then RcvWindow=6510. ARP protocol can convert the IP address to MAC address.11.R TT is the time it takes for a small packet to travel from clientto server and then back to the client.12.T he Internet mail system has three components which they are useragent, SMTP , mail server .13.T here are currently a number of popular mail access protocols,including POP3 , IMAP , and SMTP.14.DNS protocol can convert the hostname to IP address.15.This job of delivering the data in a transport-layer segment to thecorrect socket is called demultiplexing . The job of gathering data chunks at the source host from different sockets, encapsulating each data chunk with header information to create segments, and passing the segments to the network layer is called multiplexing.16.F iltering is the ability of a switch to determine whether a frameshould be forwarded to some interface or should just be dropped.Forwarding is the ability to determine the interfaces to which a frame should be directed, and then directing the frame to those interfaces.17.C onsider the data D is 01110010001, if use even parity checkingapproach, the parity bit is 1 , if use odd parity checking approach, the parity bit is 0 .18.T he units of data exchanged by a network-layer protocol are called(datagram ).19.There are two classes of packet-switched networks: (virtual circuit)networks and datagram networks.20.Provided RcvBuffer=200,LastByteRcvd=150,LastByteRead=80, thenRcvWindow=( 130 ).21.T he two most important network-layer functions in a datagram networkare ( forwarding ) and ( routing ).has a ( 32 )bit address , and MAC address is ( 48 ) bits.22.I PV423.T he ( ARP ) protocol can translate IP address into MAC address,and the ( DNS ) protocol can translate hostname into IP address 三、判断对错1．The propagation delay is the amout of time required to push all of the packet’s bits into the link.(F)2．The size of the TCP RcvWindow never changes throughout the duration of the connection.(F)3．Ethernet’s multiple access protocol is CDMA.(F)4．The Internet is a kind of vircuit curcuit network.(F) 5．Currently, the Internet does not provides a service that makes promises about how long it will take to deliver the data from sender to receiver.(T)6．TCP and UDP don’t guarantee a minimum transmission rate, but theyprovide delay guarantees. (F)7．HTTP uses TCP as its underlying transport protocol rather than running on top of UDP.(T)8．The sequence number for a segment is therefore the byte-stream number of the first byte in the segment.(T)9．Both routers and switches are plug and play devices. (F)10．TCP provides flow control by having the sender maintain a variable called the receive window.(T)11．With persistent connections, the server leaves the TCP connection open after sending a response.(T)12．The Last-modified: header in the HTTP response message indicates when the object in the response message was last modified.(F) 13．The job of delivering the data in a transport-layer segment to the correct socket is called multiplexing.( F)14． A datagram may be handled by different link-layer protocols on the different links in the path.( T)四、Consider the following plot of TCP congestion window size as a function of time.Fill in the blanks as follow:a) The initial value of Threshold at the first transmission round is __12 __.b) The value of Threshold at the 11st transmission round is ___ 8 _.c) The value of Threshold at the 21st transmission round is __ 7 __.d) After the 9th transmission round, segment loss detected by _timeout_.e) After the 19th transmission round, segment loss detected by _3 duplicate ACKs__. f) During __ 5 __ transmission round, the 18th segment is sent.五、For the given topology of the network, use Dijstra ’s shortest path algorithm to compute the shortest path from B to all network nodes. Give a shortest path tree and node B ’s routing table.Answer:0 0 0 Congestion window size Transmission roundN ’D(A),P(A) D(C),P(C) D(D),P(D) D(E),P(E) D(F),P(F) B5,B 1,B ∞ ∞ ∞ B,C3,C 6,C ∞ 3,C B,C,A4,A 5,A 3,C B,C,A,F4,A 4,F B,C,A,F,D4,F B,C,A,F,D,EDest.Next Top AC B－ CC DC EC FC六、Suppose that you send a mail to ****************.cn.Your mailbox is************.cn.The mail includes a excel attachment. Subject is “Problemabout exam ”, What might the header lines (including MIME lines) look like?Answer:From:************.cnTo:****************.cnSubject: Problem about examMIME-version : 1.0 Content-transfer-encoding: base64Content-type: application/MSexcel七、Consider the data D ＝101110000, that the receiving node receives from thenetwork. The generator G ＝1001. Use CRC method and compute whether thereis a bit-error. If there is an error, please give the value of the remainder R .1 E D C F 12 2 1 A B八、Now we had known IP address is 203.100.113.80/22,Please compute :1) Network address，2) Broadcast address，3) How many hosts are there in the network? 4) First host IP address，5)Last host IP addressAnswer:1)Network address is 203.100.112.02)Broadcast address is 203.100.115.2553)there are 1022 hosts in the network4)First host IP address is 203.100.112.15)Last host IP address is 203.100.115.254。
