6、IPV4地址可以划分为(网络号，主机号)两部分，在下面的地址标记中，用0表示所有比特为0，用-1表示所有比特为1。以下选项中，(26)不能作为目标地址，(27)不能作为源地址，(28)只能用于本机测试，(29)只能用于内部网络。IPV6使用了更大的地址空间，每个地址占有128比特，为方便网络管理人员阅读和管理。采用(30)进制加冒号的表示方法。

　　(26)A、{0，0｝　B、{127，主机号｝　C、{10，主机号｝　　　D、{网络号，-1｝

　　(27)A、{0，0｝　B、{127，主机号｝　C、{10，主机号｝　　　D、{网络号，-1｝

　　(28)A、{0，0｝　B、{127，主机号｝　C、{10，主机号｝　　　D、{192，-1｝

　　(29)A、{0，0｝　B、{128，主机号｝　C、{10，主机号｝　　　D、{168，-1｝

　　(30)A、十六　　B、十　　　　　　　　C、八　　　　　D、二
     7、IPV6 is (31)for ”Internet Protocol Version 6”.IPv6 is the “next generation”protocol designed by the IETF to (32) the current version Internet Protocol,IPVersion 4(“IPv4”).

　　Most of today’s internet uses IPv4,which is now nearly twenty years old.IPv4 has been remarkably resilient in spite of its age ,but it is beginning to have problems .Most importantly, there is a growing (33)of IPv4 addresses, which are needed by all new machines added to the internet.

　　IPv6 fixes a number of problems in IPv4,such as the (34)number of available. IPv4addreses.it also adds many improvements to IPv4 in areas such as routing and network autoconfiguration. IPv6 is expected to gradually replace IPv4,with the two coexisting for a number of years during a transition(35).

　　(31)A、 short B、abbreviate C、abbreviation D、initial

　　(32)A、substitution B、replace C、switchover D、swap

　　(33)A、scarcity B、lack C、deficiency D、shortage

　　(34)A、restrict B、limited C、confine D、imprison

　　(35)A、days B、period C、phase D、epoch

　　8、in the following essay,each blank has four choices.Choose the best answer and write down on the anser sheet .

　　Spread spectrum simply means that data is sent in small pieces over a number of the (36)frequencies available for use at any time in the specified rang.Devices using (37)spread spectrum(DSSS)communicate by (38)each byte of data into several parts and sending them concurrently on different (39).DSSS uses a lot of the available (75),about 22megaherts(MHZ).

　　(36)A、continuous B、high C、low D、discrete

　　(37)A、direct-sequence B、discrect-sequence

　　C、duplicate-sequence D、dedicate-sequence

　　(38)A、splitting B、combining C、packing D、compacting

　　(39)A、bits B、frequencies C、packets D、messages

　　(40)A、rate B、velocity C、bandwidth D、period