A transport layer protocol usually has several responsibilities.One is to create a process-to-process communication;UDP uses（ ）numbers to accomplish this. Another responsibility is to provide control mechanisms at the transport level. UDP does this task at a very minimal level. There is no flow control mechanism and there is no（ ）for received packet. UDP，however， does provide error control to some extent. If UDP detects an error in the received packet， it will silently drop it.
The transport layer also provides a connection mechanism for the processes. The （ ） must be able to send streams of data to the transport layer.It is the responsibility of the transport layer at（ ）station to make the connection with the receiver， chop the stream into transportable units，number them， and send them one by one. It is the responsibility of the transport layer at the receiving end to wait until all the different units belonging to the same process have arrived， check and pass those that are（ ）free， and deliver them to the receiving process as a stream.
问题1选项
A.hop
B.port
C.route
D.packet
问题2选项
A.connection
B.window
C.acknowledgement
D.destination
问题3选项
A.jobs
B.processes
C.programs
D.users
问题4选项
A.sending
B.routing
C.switching
D.receiving
问题5选项
A.call
B.state
C.cost
D.error
下面的地址中，属于全局广播地址的是（ ）。在下面的网络中，IP全局广播分组不能通过的通路是（ ）。
问题1选项
A.172.17.255.255
B.0.255.255.255
C.255.255.255.255
D.10.255.255.255
问题2选项
A.a和b之间的通路
B.a和c之间的通路
C.b和d之间的通路
D.b和e之间的通路
下图是一个软件项目的活动图，其中顶点表示项目里程碑，连接顶点的边表示包含的活动，则里程碑（ ）在关键路径上，活动FG的松弛时间为（ ）。
下面是家庭用户安装ADSL宽带网络时的拓扑结构图，图中左下角的X是（ ）设备，为了建立虚拟拨号线路，在用户终端上应安装（ ）协议。
问题1选项
A.DSLAM
B.HUB
C.ADSL Modem
D.IP Router
问题2选项
A.ARP
B.HTTP
C.PPTP
D.PPPoE
下面D类地址中，可用于本地子网作为组播地址分配的是（ ），一个组播组包含4个成员，当组播服务发送信息时需要发出（ ）个分组。
问题1选项
A.224.0.0.1
B.224.0.1.1
C.234.0.0.1
D.239.0.1.1
问题2选项
A.1
B.2
C.3
D.4
在BGP4协议中，（ ）报文建立两个路由器之间的邻居关系，（ ）报文给出了新的路由信息。
问题1选项
A.打开（open）
B.更新（update）
C.保持活动（keepalive）
D.通告（notification）
问题2选项
A.打开（open）
B.更新（update）
C.保持活动（keepalive）
D.通告（notification）
Linux系统中，DHCP服务的主配置文件是（ ），保存客户端租约信息的文件是（ ）。
问题1选项
A.dhcpd.leases
B.dhcpd.conf
C.xinetd.conf
D.lease.conf
问题2选项
A.dhcpd.leases
B.dhcpd.conf
C.xinetd.conf
D.lease.conf
Let us now see how randomization is done when a collision occurs. After a （ ）, time is divided into discrete slots whose length is equal to the worst-case round-trip propagation time on the ether(2τ). To accommodate the longest path allowed by Ethernet, the slot time has been set t0 512 bit times, or 51.2μsec.
After the first collision, each station waits either 0 or 1 （ ） times before trying again. If two stations collide and each one picks the same random number, they will collide again. After the second collision, each one picks either 0,1,2,or 3 at random and waits that number of slot times. If a third collision occurs(the probability of this happening is 0.25), then the next time the number of slots to wait is chosen at （ ）from the interval 0 to 23-1.
In general, after i collisions，a random number between 0 and 2i-1 is chosen, and that number of slots is skippeD. However, after ten collisions have been reached, the randomization（ ） is frozen at a maximum of 1023 slots. After 16 collisions, the controller throws in the towel and reports failure back to the computer. Further recoveryis up to （ ） layers.
问题1选项
A.datagram
B.collision
C.connection
D.service
问题2选项
A.slot
B.switch
C.process
D.fire
问题3选项
A.rest
B.random
C.once
D.odds
问题4选项
A.unicast
B.multicast
C.broadcast
D.interval
问题5选项
A.local
B.next
C.higher
D.lower
可以用于表示地址块220.17.0.0～220.17.7.0的网络地址是（ ），这个地址块中可以分配（ ）个主机地址。
问题1选项
A.220.17.0.0/20
B.220.17.0.0/21
C.220.17.0.0/16
D.220.17.0.0/24
问题2选项
A.2032
B.2048
C.2000
D.2056
有一种特殊的口地址叫做自动专用IP地址(APIPA)，这种地址的用途是（ ），以下地址中属于自动专用IP地址的是（ ）。
问题1选项
A.指定给特殊的专用服务器
B.作为默认网关的访问地址
C.DHCP服务器的专用地址
D.无法获得动态地址时作为临时的主机地址
问题2选项
A.224.0.0.1
B.127.0.0.1
C.169.254.1.15
D.192.168.0.1
用户B收到用户A带数字签名的消息M，为了验证M的真实性，首先需要从CA获取用户A的数字证书，并利用—（ ）验证该证书的真伪，然后利用（ ）验证M的真实性。
问题1选项
A.CA的公钥
B.B的私钥
C.A的公钥
D.B的公钥
问题2选项
A.CA的公钥
B.B的私钥
C.A的公钥
D.B的公钥
