搜题请搜索小程序“爱下问搜题”
问题 单项选择题

Traditional IP packet forwarding analyzes the____(1)____IP address contained in the network layer header of each packet as the packet travels from its source to its final destination．A router analyzes the destination IP address independently at each hop in the network．Dynamic ____(2)____protocols or static configuration builds the database needed to analyze the destination IP address(the routing table)．The process of implementing traditional IP routing also is called hop—by—hop destination—based____(3)____routing．Although successful，and obviously widely deployed，certain restrictions，which have been realized for some time，exist for this method of packet forwarding that diminish its____(4)____．New techniques are therefore required to address and expand the functionality of an IP—based network infrastructure．This first chapter concentrate on identifying these restrictions and presents a rew，architecture，known as multipIeprotocol____(5)____switching，that provides solutions to some of these restrictions．

(5)

A．const

B．cast

C．mark

D．label

答案

参考答案：D

解析：解析：当数据包从其来源到其最终目的地址时，传统的IP报文转发分析包含在每一个数据包的网络层报头的目的IP地址。路由器独立地分析网络中的每一跳目标IP地址。动态路由协议或静态配置生成所需的数据库来分析目标IP地址(路由表)。传统的IP路由实现的过程也被称为基于逐跳目的地的单播路南。虽然成功地广泛采用，但是一些已经实现一段时间的限制仍存在，此方法存在报文的转发减少其灵活性。因此，需要新的技术，以处理和扩展一个基于IP的网络基础设施的功能。第一章着重识别这些限制，并提出了一种新的架构，被称为多协议标签交换，来提供解决这些限制的方法。

单项选择题

Phyllis Wheatley is regarded as America’’s first black poet. She was born in Senegal, Africa, about 1753 and brought to America aboard a slave ship at about the age of seven. John and Susannah Wheatley bought her for three pounds at a slave auction in Boston in 1761 to be a personal servant of Mrs. Wheatley. The family had three other slaves, and all were treated with respect. Phyllis was soon accepted as one of the family, which included being raised and educated with the Wheatley’’s twin 15-year-old children, Mary and Nathaniel. At that time, most females, even from better families, could not read and write, but Mary was probably one of the best educated young women in Boston. Mary wanted to become a teacher, and in fact, it was Mary who decided to take charge of Phyllis’’s education. Phyllis soon displayed her remarkable talents. At the age of twelve she was reading the Greek and Latin classics and passages from the Bible. And eventually, Mrs. Wheatley decided Phyllis should become a Christian.At the age of thirteen Phyllis wrote her first poem. She became a Boston sensation after she wrote a poem on the death of the evangelical preacher George Whitfield in 1770. It became common practice in Boston to have "Mrs. Wheatley’’s Phyllis" read poetry in polite society. Mary married in 1771, and Phyllis later moved to the country because of poor health, as a teacher and caretaker to a farmer’’s three children. Mary had tried to interest publishers in Phyllis’’s poems but once they heard she was a Negro they weren’’t interested.Then in 1773 Phyllis went with Nathaniel, who was now a businessman, to London. It was thought that a sea voyage might improve her health. Thirty-nine of her poems were published in London as Poems on Various Subjects, Religious and Moral. It was the first book published by a black American. In 1775 Phyllis wrote a poem extolling the accomplishments of George Washington and sent it to him. He responded by praising her talents and inviting her to visit his headquarters. After both of her benefactors died in 1777, and Mary died in 1778, Phyllis was freed as a slave. She married in 1778, moved away from Boston, and had three children. But after the unhappy marriage, she moved back to Boston, and died in poverty at the age of thirty.

The word "they" in the last sentence Paragraph 2 refers to________.

A．publishers

B．poems

C．children

D．black people
查看答案
单项选择题

腹部CT检查前口服阳性对比剂的目的是（）。

A.减少胃蠕动

B.加速胃排空

C.消除受检者的焦虑及紧张

D.充盈胃肠道，形成良好对比

E.防止因禁食引起的脱水
查看答案