ActualTests.Cisco.640-802.Exam.Q.and.A.08.15.08-DDU (1130589), страница 5
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SessionD. TransportE. InternetF. Data LinkG. PhysicalAnswer: AExplanation:The application layer is the highest layer (layer 7) of the OSI model, and is reserved forend user applications. Since FTP is itself an application, layer 7 is the highest layer used.Actualtests.com - The Power of Knowing640-802Incorrect Answers:B, C, D, E, F, G. In any given FTP session, all of these layers will be used at some pointbut they are incorrect because the question asked for the highest layer used by FTP.QUESTION 40:ICMP is often used in troubleshooting and verifying network. What statements aretrue regarding ICMP packets? (Choose two)A.
They acknowledge receipt of TCP segments.B. They guarantee datagram delivery.C. They can provide hosts with information about network problems.D. They are encapsulated within IP datagrams.E. They are encapsulated within UDP datagrams.F. They are encapsulated within TCP datagrams.Answer: C, DExplanation:ping may be used to find out whether the local machines are connected to the network orwhether a remote site is reachable.
This tool is a common network tool for determiningthe network connectivity which uses ICMP protocol instead of TCP/IP and UDP/IP. Thisprotocol is usually associated with the network management tools which provide networkinformation to network administrators, such as ping and traceroute (the later also uses theUDP/IP protocol).ICMP is quite different from the TCP/IP and UDP/IP protocols. No source anddestination ports are included in its packets. Therefore, usual packet-filtering rules forTCP/IP and UDP/IP are not applicable. Fortunately, a special "signature" known as thepacket's Message type is included for denoting the purposes of the ICMP packet. Mostcommonly used message types are namely, 0, 3, 4, 5, 8, 11, and 12 which represent echoreply, destination unreachable, source quench, redirect, echo request, time exceeded, andparameter problem respectively.In the ping service, after receiving the ICMP "echo request" packet from the sourcelocation, the destinationIncorrect AnswersICMP is an IP protocol so A and E are incorrect.ICMP doesn't guarantee datagram delivery so B is wrong as well.QUESTION 41:Which of the following services use TCP? (Choose three)A.
DHCPB. SMTPActualtests.com - The Power of Knowing640-802C. SNMPD. FTPE. HTTPF. TFTPAnswer: B, D, EExplanation:TCP (Transmission Control Protocol) is a reliable mechanism for data delivery. SMTP,FTP and HTTP services use TCP via ports 25, 20/21, and 80, respectively.QUESTION 42:Which of the following are types of flow control? (Choose three)A.
BufferingB. Cut-throughC. WindowingD. Congestion avoidanceE. Load balancingAnswer: A, C, DExplanation:Data transmission flow control occurs at layer 4 with the help of buffering, windowingand congestion avoidance.Reference: CCNA Cisco Certified Network Associate Study Guide, 5th Edition, ToddLammle, chapter 1, page 17.QUESTION 43:Which Layer 4 protocol is used for a Telnet connection between two Certkillerrouters?A.
IPB. ICMPC. DNSD. TCPE. UDPF. RTPAnswer: DExplanation:Actualtests.com - The Power of Knowing640-802TCP is a reliable connection-oriented protocol. TCP uses acknowledgments, sequencing,and flow control to ensure reliability. Telnet uses TCP port 23.QUESTION 44:FTP, Telnet, DNS, and SMTP are all protocols being used in the Certkiller network.Of these, which uses both TCP and UDP ports?A. TelnetB. FTPC. DNSD. SMTPE. None of the aboveAnswer: CExplanation:The following port numbers for the protocols listed above are as follows:FTP: TCP Port 20 and 21SMTP: TCP Port 25Telnet: TCP Port 23DNS: both TCP and UDP Port 53QUESTION 45:Although TCP segments are similar to UDP segments, TCP packets contains someadditional fields. Which of the following are found in a TCP header, but not in aUDP header? (Choose three)A.
ChecksumB. Sequence numberC. Destination portD. Window sizeE. Acknowledgment numberF. Source portAnswer: B, D, EExplanation:The Figure below illustrates the fields and overall format of a TCP packet.Twelve fields comprise a TCP packet.Actualtests.com - The Power of Knowing640-802TCP Packet Field DescriptionsThe following descriptions summarize the TCP packet fields illustrated in Figure 30-10:1. Source Port and Destination Port-Identifies points at which upper-layer source anddestination processes receive TCP services.2.
Sequence Number-Usually specifies the number assigned to the first byte of data in thecurrent message. In the connection-establishment phase, this field also can be used toidentify an initial sequence number to be used in an upcoming transmission.3. Acknowledgment Number-Contains the sequence number of the next byte of data thesender of the packet expects to receive.4.
Data Offset-Indicates the number of 32-bit words in the TCP header.5. Reserved-Remains reserved for future use.6. Flags-Carries a variety of control information, including the SYN and ACK bits usedfor connection establishment, and the FIN bit used for connection termination.7. Window-Specifies the size of the sender's receive window (that is, the buffer spaceavailable for incoming data).8.
Checksum-Indicates whether the header was damaged in transit.9. Urgent Pointer-Points to the first urgent data byte in the packet.10. Options-Specifies various TCP options.11. Data-Contains upper-layer information.User Datagram Protocol (UDP)The User Datagram Protocol (UDP) is a connectionless transport-layer protocol (Layer 4)that belongs to the Internet protocol family. UDP is basically an interface between IP andupper-layer processes. UDP protocol ports distinguish multiple applications running on asingle device from one another.Unlike the TCP, UDP adds no reliability, flow-control, or error-recovery functions to IP.Because of UDP's simplicity, UDP headers contain fewer bytes and consume lessnetwork overhead than TCP.UDP is useful in situations where the reliability mechanisms of TCP are not necessary,such as in cases where a higher-layer protocol might provide error and flow control.UDP is the transport protocol for several well-known application-layer protocols,including Network File System (NFS), Simple Network Management Protocol (SNMP),Domain Name System (DNS), and Trivial File Transfer Protocol (TFTP).The UDP packet format contains four fields, as shown in the figure below.
These includeActualtests.com - The Power of Knowing640-802source and destination ports, length, and checksum fields.A UDP packet consists of four fields.Source and destination ports contain the 16-bit UDP protocol port numbers used todemultiplex datagrams for receiving application-layer processes. A length field specifiesthe length of the UDP header and data.
Checksum provides an (optional) integrity checkon the UDP header and data.Reference: http://www.cisco.com/univercd/cc/td/doc/cisintwk/ito_doc/ip.htm#xtocid21QUESTION 46:DRAG DROPYou work as a network administrator at Certkiller .com.Your boss, Mrs. Certkiller, is interested in the OSI layers. Match the items with theappropriate layers. Note that not all options are used.Actualtests.com - The Power of Knowing640-802Answer:QUESTION 47:Certkiller is installing IP phones in a new office. The phones and office computersconnect to the same device.
To ensure maximum throughout for the phone datasessions, the company needs to make sure that the phone traffic is on a differentnetwork from that of the office computer data traffic. What is the best networkdevice to which to directly connect the phones and computers and what technologyshould be implemented on this device? (Choose two)A. VLANB. SubinterfaceC. STPD. HubE. SwitchF. RouterG. Wireless Access PointH.
VTPAnswer: A, EQUESTION 48:The corporate head office of Certkiller has a teleconferencing system that uses VOIPActualtests.com - The Power of Knowing640-802(voice over IP) technology. This system uses UDP as the transport for the datatransmissions. If these UDP datagrams arrive at their destination out of sequence,what will happen?A. UDP will send an ICMP Information Request to the source host.B.
UDP will pass the information in the datagrams up to the next OSI layer in the orderthat they arrive.C. UDP will drop the datagrams.D. UDP will use the sequence numbers in the datagram headers to reassemble the data inthe correct order.E. UDP will not acknowledge the datagrams and wait for a retransmission of thedatagrams.Answer: BExplanation:VOIP systems utilize UDP because it is faster and uses less overhead. In addition, thereliable transport mechanism used in TCP is useless to VOIP because if a packet getsdropped and needs to be resent, it will be already too late.UDP provides a service for applications to exchange messages.
Unlike TCP, UDP isconnectionless and provides no reliability, no windowing, and no reordering of thereceived data. However, UDP provides some functions of TCP , such as data transfer,segmentation, and multiplexing using port numbers, and it does so with fewer bytes ofoverhead and with less processing required. UDP data transfer differs from TCP datatransfer in that no reordering or recovery is accomplished.
Applications that use UDP aretolerant of lost data, or they have some application mechanism to recover data loss.Reference: CCNA Self-Study CCNA INTRO exam certification Guide (Cisco Press,ISBN 1-58720-094-5) Page 161.QUESTION 49:Part of the Certkiller network is shown below:You work as a network technician for Certkiller and are responsible for thisnetwork.
Based on the diagram shown above, how many collision domains arethere?Actualtests.com - The Power of Knowing640-802A. SixB. FourteenC. FourD. TwoE. ThreeF. OneG. EightAnswer: DExplanation:The multi-segment configuration guidelines apply only to a single Ethernet "collisiondomain." A collision domain is formally defined as a single CSMA/CD network in whichthere will be a collision if two computers attached to the system transmit at the sametime. An Ethernet system composed of a single segment or multiple segments linked withrepeaters is a network that functions as a single collision domain.FIGURE 1 Repeater hubs create a single collision domainThe figure shows two repeater hubs connecting three computers. Since only repeaterconnections are used between segments in this network, all of the segments andcomputers are in the same collision domain.In the next figure, the repeaters and DTEs are instead separated by a router (packetswitch) and are therefore in separate collision domains, since routers do not forwardcollision signals from one segment to another.
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