2012年05月网络工程师考试上午真题【基础知识】-软考吧-您身边的软考专家-www.ruankaoba.com

2012年05月网络工程师考试上午真题【基础知识】

内容：基础知识
时间：150分钟
总分：75分
题数：75题

【64】802.11在MAC层采用了（64）协议。

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【65-66】在无线局域网中，ap的作用是（65）。新标准ieee802.lln提供的最高数据速率可达到（66）。

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【67】ieee802.16工作组提出的无线接入系统空中接口标准是（67）。

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【68】安全电子邮件使用（68）协议。

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【69】建筑物综合布线系统中的园区子系统是指（69）。

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【70】下面有关rmon的论述中，错误的是（70）。

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【71-75】the TCP protocolis a （71） layer protocol. each connection connects two TCPs thatmaybejustone physical network apart or located on opposite sides ofthe globe. in other words， eachconnectioncreates a （72） witha length that may be totally different from another path created byanotherconnection. this means that TCP cannot use the same retransmission time for all connections.selectingafixed retransnussion time for all connections can result in serious consequences. iftheretransmission time does not allow enough time for a （73） to reach the destination and an acknowledgmentto reach the source， it can result in retransmission of segments that are still on the way.conversely，if the retransnussion time is longer than necessary for a short path， it may result indelayforthe application programs.even for one single connection， the retransmission time should notbefixed.aconnection may be able to send segments and receive （74）faster during nontraffic periodthanduringcongested periods. TCP uses the dynamic retransmission time，a transmission time is differentfor each connection and which may be changed during the same connection. retransmission timecanbemade（75） by basing it on the round-trip time （rtt）. several formulas are used for thispurpose.

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