CCNA 640-802 Ver 22-09-2008 page5
QUESTION 41
Which of the following services use TCP? (Choose three)
A. DHCP
B. SMTP
C. SNMP
D. FTP
E. HTTP
F. TFTP
Answer: B, D, E
Explanation:
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. Buffering
B. Cut-through
C. Windowing
D. Congestion avoidance
E. Load balancing
Answer: A, C, D
Explanation:
Data transmission flow control occurs at layer 4 with the help of buffering, windowing and congestion avoidance.
QUESTION 43
Which Layer 4 protocol is used for a Telnet connection between two Certkiller routers?
A. IP
B. ICMP
C. DNS
D. TCP
E. UDP
F. RTP
Answer: D
Explanation:
TCP 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. Telnet
B. FTP
C. DNS
D. SMTP
E. None of the above
Answer: C
Explanation:
The following port numbers for the protocols listed above are as follows: FTP: TCP Port 20 and 21
SMTP: TCP Port 25
Telnet: TCP Port 23
DNS: both TCP and UDP Port 53
QUESTION 45
Although TCP segments are similar to UDP segments, TCP packets contains some additional fields. Which of theNfollowing are found in a TCP header, but not in a UDP header? (Choose three)
A. Checksum
B. Sequence number
C. Destination port
D. Window size
E. Acknowledgment number
F. Source port
Answer: B, D, E
Explanation:
The Figure below illustrates the fields and overall format of a TCP packet. Twelve fields comprise a TCP packet.
TCP Packet Field Descriptions
The following descriptions summarize the TCP packet fields illustrated in Figure 30-10:
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 and upper-layer processes. UDP protocol ports distinguish multiple applications running on a single 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 less network 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 include source 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 to demultiplex datagrams for receiving application-layer processes. A length field specifies the length of the UDP header and data. Checksum provides an (optional) integrity check on the UDP header and data.
QUESTION 46
DRAG DROP
You work as a network administrator at Certkiller .com. Your boss, Mrs. Certkiller, is interested in the OSI layers. Match the items with the appropriate layers. Note that not all options are used.
Answer:
QUESTION 47
Certkiller is installing IP phones in a new office. The phones and office computers connect to the same device. To ensure maximum throughout for the phone data sessions, the company needs to make sure that the phone traffic is on a different network from that of the office computer data traffic. What is the best network device to which to directly connect the phones and computers and what technology should be implemented on this device? (Choose two)
A. VLAN
B. Subinterface
C. STP
D. Hub
E. Switch
F. Router
G. Wireless Access Point
H. VTP
Answer: A, E
QUESTION 48
The corporate head office of Certkiller has a teleconferencing system that uses VOIP (voice over IP) technology. This system uses UDP as the transport for the data transmissions. 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 order that they arrive.
C. UDP will drop the datagrams.
D. UDP will use the sequence numbers in the datagram headers to reassemble the data in the correct order.
E. UDP will not acknowledge the datagrams and wait for a retransmission of the datagrams.
Answer: B
Explanation:
VOIP systems utilize UDP because it is faster and uses less overhead. In addition, the reliable transport mechanism used in TCP is useless to VOIP because if a packet gets dropped and needs to be resent, it will be already too late. UDP provides a service for applications to exchange messages. Unlike TCP, UDP is connectionless and provides no reliability, no windowing, and no reordering of the received 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 of overhead and with less processing required. UDP data transfer differs from TCP data transfer in that no reordering or recovery is accomplished. Applications that use UDP are tolerant of lost data, or they have some application mechanism to recover data loss.
QUESTION 49
Part of the Certkiller network is shown below:
You work as a network technician for Certkiller and are responsible for this network. Based on the diagram shown above, how many collision domains are there?
A. Six
B. Fourteen
C. Four
D. Two
E. Three
F. One
G. Eight
Answer: D
Explanation:
The multi-segment configuration guidelines apply only to a single Ethernet "collision domain." A collision domain is formally defined as a single CSMA/CD network in which there will be a collision if two computers attached to the system transmit at the same time. An Ethernet system composed of a single segment or multiple segments linked with repeaters is a network that functions as a single collision domain.
FIGURE 1 Repeater hubs create a single collision domain
The figure shows two repeater hubs connecting three computers. Since only repeater connections are used between segments in this network, all of the segments and computers are in the same collision domain. In the next figure, the repeaters and DTEs are instead separated by a router (packet switch) and are therefore in separate collision domains, since routers do not forward collision signals from one segment to another. Routers contain multiple Ethernet interfaces and are designed to receive a packet on one Ethernet port and transmit the data onto another Ethernet port in a new packet.
FIGURE 2 Routers creates separate collision domains
Instead of propagating collision signals between Ethernet segments, routers interrupt the collision domain and allow the Ethernets they link to operate independently. Therefore, you can use packet switching hubs to build larger network systems by interconnecting individual Ethernet systems.
QUESTION 50
You work as a network technician at Certkiller .com. You have been assigned the task of designing a new Certkiller internetwork. The main priority is to achieve the highest reliability available. Certkiller .com is willing to spend more dollars to avoid downtime caused by link failure. Which of the following four designs is to be preferred?
A. Design Certkiller A
B. Design Certkiller B
C. Design Certkiller C
D. Design Certkiller D
Answer: A Explanation:
A network topology that is set up so that each device is directly connected to every other device on the network. This connection method has built-in redundancy. If one link goes down, the device will transmit via another link.
Example:
If the partial mesh design is a compromise between the network administrators and managers, then the full mesh design implies that the network administrators won. This design is every Cisco network administrator's picture of perfection over a Frame Relay cloud. It gives every site a direct virtual circuit to every other site, as shown in Figure This design gives maximum redundancy and minimum packet latency (latency describes how long it takes a packet to reach each location).
Which of the following services use TCP? (Choose three)
A. DHCP
B. SMTP
C. SNMP
D. FTP
E. HTTP
F. TFTP
Answer: B, D, E
Explanation:
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. Buffering
B. Cut-through
C. Windowing
D. Congestion avoidance
E. Load balancing
Answer: A, C, D
Explanation:
Data transmission flow control occurs at layer 4 with the help of buffering, windowing and congestion avoidance.
QUESTION 43
Which Layer 4 protocol is used for a Telnet connection between two Certkiller routers?
A. IP
B. ICMP
C. DNS
D. TCP
E. UDP
F. RTP
Answer: D
Explanation:
TCP 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. Telnet
B. FTP
C. DNS
D. SMTP
E. None of the above
Answer: C
Explanation:
The following port numbers for the protocols listed above are as follows: FTP: TCP Port 20 and 21
SMTP: TCP Port 25
Telnet: TCP Port 23
DNS: both TCP and UDP Port 53
QUESTION 45
Although TCP segments are similar to UDP segments, TCP packets contains some additional fields. Which of theNfollowing are found in a TCP header, but not in a UDP header? (Choose three)
A. Checksum
B. Sequence number
C. Destination port
D. Window size
E. Acknowledgment number
F. Source port
Answer: B, D, E
Explanation:
The Figure below illustrates the fields and overall format of a TCP packet. Twelve fields comprise a TCP packet.
TCP Packet Field Descriptions
The following descriptions summarize the TCP packet fields illustrated in Figure 30-10:
- Source Port and Destination Port-Identifies points at which upper-layer source and destination processes receive TCP services.
- Sequence Number-Usually specifies the number assigned to the first byte of data in the current message. In the connection-establishment phase, this field also can be used to identify an initial sequence number to be used in an upcoming transmission.
- Acknowledgment Number-Contains the sequence number of the next byte of data the sender of the packet expects to receive.
- Data Offset-Indicates the number of 32-bit words in the TCP header.
- Reserved-Remains reserved for future use.
- Flags-Carries a variety of control information, including the SYN and ACK bits used for connection establishment, and the FIN bit used for connection termination.
- Window-Specifies the size of the sender's receive window (that is, the buffer space available for incoming data).
- Checksum-Indicates whether the header was damaged in transit.
- Urgent Pointer-Points to the first urgent data byte in the packet.
- Options-Specifies various TCP options.
- Data-Contains upper-layer information.
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 and upper-layer processes. UDP protocol ports distinguish multiple applications running on a single 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 less network 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 include source 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 to demultiplex datagrams for receiving application-layer processes. A length field specifies the length of the UDP header and data. Checksum provides an (optional) integrity check on the UDP header and data.
QUESTION 46
DRAG DROP
You work as a network administrator at Certkiller .com. Your boss, Mrs. Certkiller, is interested in the OSI layers. Match the items with the appropriate layers. Note that not all options are used.
Answer:
QUESTION 47
Certkiller is installing IP phones in a new office. The phones and office computers connect to the same device. To ensure maximum throughout for the phone data sessions, the company needs to make sure that the phone traffic is on a different network from that of the office computer data traffic. What is the best network device to which to directly connect the phones and computers and what technology should be implemented on this device? (Choose two)
A. VLAN
B. Subinterface
C. STP
D. Hub
E. Switch
F. Router
G. Wireless Access Point
H. VTP
Answer: A, E
QUESTION 48
The corporate head office of Certkiller has a teleconferencing system that uses VOIP (voice over IP) technology. This system uses UDP as the transport for the data transmissions. 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 order that they arrive.
C. UDP will drop the datagrams.
D. UDP will use the sequence numbers in the datagram headers to reassemble the data in the correct order.
E. UDP will not acknowledge the datagrams and wait for a retransmission of the datagrams.
Answer: B
Explanation:
VOIP systems utilize UDP because it is faster and uses less overhead. In addition, the reliable transport mechanism used in TCP is useless to VOIP because if a packet gets dropped and needs to be resent, it will be already too late. UDP provides a service for applications to exchange messages. Unlike TCP, UDP is connectionless and provides no reliability, no windowing, and no reordering of the received 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 of overhead and with less processing required. UDP data transfer differs from TCP data transfer in that no reordering or recovery is accomplished. Applications that use UDP are tolerant of lost data, or they have some application mechanism to recover data loss.
QUESTION 49
Part of the Certkiller network is shown below:
You work as a network technician for Certkiller and are responsible for this network. Based on the diagram shown above, how many collision domains are there?
A. Six
B. Fourteen
C. Four
D. Two
E. Three
F. One
G. Eight
Answer: D
Explanation:
The multi-segment configuration guidelines apply only to a single Ethernet "collision domain." A collision domain is formally defined as a single CSMA/CD network in which there will be a collision if two computers attached to the system transmit at the same time. An Ethernet system composed of a single segment or multiple segments linked with repeaters is a network that functions as a single collision domain.
FIGURE 1 Repeater hubs create a single collision domain
The figure shows two repeater hubs connecting three computers. Since only repeater connections are used between segments in this network, all of the segments and computers are in the same collision domain. In the next figure, the repeaters and DTEs are instead separated by a router (packet switch) and are therefore in separate collision domains, since routers do not forward collision signals from one segment to another. Routers contain multiple Ethernet interfaces and are designed to receive a packet on one Ethernet port and transmit the data onto another Ethernet port in a new packet.
FIGURE 2 Routers creates separate collision domains
Instead of propagating collision signals between Ethernet segments, routers interrupt the collision domain and allow the Ethernets they link to operate independently. Therefore, you can use packet switching hubs to build larger network systems by interconnecting individual Ethernet systems.
QUESTION 50
You work as a network technician at Certkiller .com. You have been assigned the task of designing a new Certkiller internetwork. The main priority is to achieve the highest reliability available. Certkiller .com is willing to spend more dollars to avoid downtime caused by link failure. Which of the following four designs is to be preferred?
A. Design Certkiller A
B. Design Certkiller B
C. Design Certkiller C
D. Design Certkiller D
Answer: A Explanation:
A network topology that is set up so that each device is directly connected to every other device on the network. This connection method has built-in redundancy. If one link goes down, the device will transmit via another link.
Example:
If the partial mesh design is a compromise between the network administrators and managers, then the full mesh design implies that the network administrators won. This design is every Cisco network administrator's picture of perfection over a Frame Relay cloud. It gives every site a direct virtual circuit to every other site, as shown in Figure This design gives maximum redundancy and minimum packet latency (latency describes how long it takes a packet to reach each location).
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