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The corporate head office of Ezonexam 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

题目

The corporate head office of Ezonexam 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.

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相似问题和答案

第1题：

Network managers have long(140)practical voice-over-IP(VOIP)solutions. VOIP(141)ease network management and decreases costs by converging a company's telephony and data infrastructures into one network. And a VOIP solution implemented at a company's head-quarters with far-reaching branch offices can(142)tremendous amounts of(143)in long distance phone bills, provided that solution delivers POTS-like voice(144)over the Internet.

A．await

B．awaited

C．awaiting

D．awaits


正确答案：B

第2题：

Which three statements describe the User Datagram Protocol (UDP)?()

A.UDP provides delivery notification and error checking mechanisms.

B.UDP is faster than the Transmission Control Protocol (TCP).

C.UDP application examples include DNS and VoIP.

D.UDP is an application layer protocol.

E.UDP uses a best effort delivery approach.


参考答案：B, C, E

第3题：

Regarding DHCP (dynamic host configuration protocol), which two of the following choices below are true? (Select two answer choices)

A. The DHCP Discover message uses FF-FF-FF-FF-FF as the Layer 2 destination address.

B. The DHCP Discover message uses UDP as the transport layer protocol.

C. The DHCP Discover message uses a special Layer 2 multicast address as the destination address.

D. The DHCP Discover message uses TCP as the transport layer protocol.

E. The DHCP Discover message does not use a Layer 2 destination address.

F. The DHCP Discover message does not require a transport layer protocol.


正确答案：AB
A,B 解析：Explanation:
DHCP uses UDP as its transport protocol. DHCP messages from a client to a server are sent to the DHCP server port (UDP port 67), and DHCP messages from a server to a client are sent to the DHCP client port (UDP port 68).The client broadcasts a DHCPDISCOVER message on its local physical subnet. The DHCPDISCOVER message may include options that suggest values for the network address and lease duration. BOOTP relay agents may pass the message on to DHCP servers not on the same physical subnet.

Each server may respond with a DHCPOFFER message that includes an available network address in the "ipaddr" field (and other configuration parameters in DHCP options). Servers need not reserve the offered network address, although the protocol will work more efficiently if the server avoids allocating the offered network address to another client. The server unicasts the DHCPOFFER message to the client (using the DHCP/BOOTP relay agent if necessary) if possible, or may broadcast the message to a broadcast address (preferably 255.255.255.255) on the client's subnet.

Incorrect Answers:
C. DHCP messages are broadcast to the "all hosts" address. IP multicast addresses are not used.

D. UDP is used, not TCP.

E. Since DHCP is used so that a client can obtain an IP address, a layer two destination address must be used, as the layer 3 IP address does not yet exist on the client for the return traffic.

F. DHCP, along with nearly every other type of traffic, requires the use of a transport layer protocol.

第4题：

Network managers have long awaited practical voice-over-IP(VOIP)solutions. VOIP promises(71)network management and decreases costs by(72)a company's telephony and data infrastructures into one network. And a VOIP solution implemented at a company' s head -quarters with far -reaching branch offices can(73)tremendous amounts of(74)in long distance phone bills, provided that solution delivers POTS -like voice(75)over the Internet.

A．complicated

B．useful

C．ease

D．orderly


正确答案：C

第5题：

What are three characteristics of UDP?()

A. UDP is faster than TCP

B. UDP operates at the Transport Layer

C. UDP is connection-oriented

D. UDP data is sent best-effort

E. UDP is more reliable than TCP


参考答案：A, B, D

第6题：

Each machine supporting TCP has a TCP transport entity, either a library procedure, a user process, or part of the kernel. In all case, it manages TCP streams and (71) to the IP layer. A TCP (72) accepts user data streams from local process, breaks them into pieces not exceeding 64KB, and sends each piece as a separate IP (73). When datagrams containing TCP data arrive at a machine, they are given to the TCP entity, which reconstructs the original byte streams.The IP layer gives no guarantee that datagrams will be delivered properly, so it is up to TCP to time out and (74) them as need be. Datagmms do arrive may well do so in the wrong order, it is also up to TCP to (75) them into messages in the proper sequence.

A．calls

B．interfaces

C．links

D．produces


正确答案：B

第7题：

Which two statements are true about optical networks?()

A. SONET and SDH both use time-division multiplexing.

B. An optical transport network system uses time-division multiplexing.

C. SONET and SDH both use wavelength-division multiplexing.

D. An optical transport network system uses wavelength-division multiplexing.


参考答案：A, D

第8题：

Which one of the following protocols uses both UDP and TCP ports for the transport layer operation?

A．FTP

B．TFTP

C．SMTP

D．Telnet

E．DNS


正确答案：E
解析：Explanation:TCPandUDPmustuseportnumberstocommunicatewiththeupperlayers.Portnumberskeeptrackofdifferentconversationscrossingthenetworksimultaneously.Originating-sourceportnumbersaredynamicallyassignedbythesourcehost,whichwillbesomenumberstartingat1024.1023andbelowaredefinedinRFC1700,whichdiscusseswhatiscalledwell-knownportnumbers.Virtualcircuitsthatdonotuseanapplicationwithawell-knownportnumberareassignedportnumbersrandomlychosenfromwithinaspecificrangeinstead.TheseportnumbersidentifythesourceanddestinationhostintheTCPsegment.OnlyDNSusesbothUDPandTCPport53.

第9题：

Network managers have long awaited practical voice-over-IP(VOIP)solutions. VOIP promises ease network management and decreases(66)by converging a company's telephony and data infrastructures into one network. And a VOIP solution implemented at a company's head-quarters with far-reaching branch offices can(67)tremendous amounts of money in long distance phone bills, provided that solution delivers POTS-like voice(68)over the Internet.

VOIP gateways are designed to convert voice from the(69)domain to the circuit switched domain. VOIP solutions use a digital signal processor(DSP)to process the voice data, preparing the voice sample for transmission by compressing voice and removing jitter. The VOIP equipment must comply with the(70)H.323 standard defined by the International Telecommunication Union, or ITU.

A．time

B．cash

C．costs

D．space


正确答案：C

第10题：

During the boot sequence, a Ezonexam 2800 series router needs to locate and load an operating system. What is the default order the router uses to find an operating system?

A．ROM, TFTP server, Flash

B．Flash, TFTP server, ROM

C．Flash, NVRAM, TFTP server

D．Flash, ROM, TFTP server

E．Flash, TFTP server, RAM


正确答案：B
解析：Explanation:BootinguptheRouter:CiscorouterscanbootCiscoIOSsoftwarefromtheselocations:1.Flashmemory2.TFTPserver3.ROM(notfullCiscoIOS)Multiplesourceoptionsprovideflexibilityandfallbackalternatives.

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