根据下面的文字资料回答 68～72 题For each blank．choose the best answerfrom the four choices

A.先左后右

B.先上后下

C.先内后外

D.先易后难

E.先阴角后阳角

A.8

B.16

C.32

D.64

（2 ）is a protocol that most USENET machines nOW use it to allow news articles to propagate from one machine to another over a reliable connection．

（3 ）is an approach preferred by cable TV providers．In this solution the fiber terminates at an optoelectrical converter and the final segment is a shared coaxial cable．

（4 ）is a device used to connect two separate network that use different communication protocol．

（5 ）is a digital-to-digital polar encoding method in which the signal level is always either positive or negative．

第6题：文中（1 ）处正确的答案是（）。

A．MD

B．RSA

C．DES

D．MIB

A.数据链路

B.网络

C.传输

D.应用

A.安全

B.消防

C.规划

D.国家有关规定

E.施工现场平面布置

A.研究数据加密

B.研究数据保密

C.研究数据解密

D.研究信息安全

根据下面的文字资料回答 71～75 题 The Simple Network Management Protocol(SNMP)is an （1 ）protocol that facilitates the exchange of management information between （2 ）．It is part of the Transmission Control ProtocoL/Internet Protocol(TCP/IP)protocol suite. SNMP enables network（3 ）to manage network performance，find and sole network problems，and plan for（4 ）．An SNMP managed network consists of three key components：managed devices，（5 ），and networkmanagement systems．

第6题：文中（1 ）处正确的答案是（）。

A．Physical Layer

B．Link Layer

C．Network Layer

D．Transport Layer

A.费用

B.灵活性

C.可靠性

D.环型

根据下面的文字资料回答 66～70 题

In low-speed network，it is usually adequate to wait for congestion to occur and

then react to it by telling the source of packets to slow down．In high-speed

networks，this approach oftenworks poorly，because in the（1 ）between sending the

notification and notification arriving at the source，thousands of

additional（2 ）may aITive．In ATM network，a major tool for

preventing（3 ）is（4 ）control．when a host wants a new virtual（5 ），it must

describe the traffic to be offered and the service expected．

第66题：文中（1 ）处正确的答案是（）。

A．interval

B．time

C．slot

D．delay

A.数据链路

B.网络

C.传输

D.应用