一个Lan拓扑可以使用令牌传递或CSMA/CD控制媒体访问，其拓扑属于下列的(69)，若仅使用像令牌传递这样的确定性媒体控制方法，其拓扑属于下列的(70)。

(17)

(15)

(16)

(14)

A typical application of this(71)is ADSL. It is emerging as the technology for home-and small-office Internet connectivity. It provides either 1.5 Mb/s～8 Mb/s from the network to the user and 64 kb/s～512 kb/s in the reverse direction depending on the distance, 12000 or 18000 feet. The different speed for each direction gives it the(72)label. ADSL is designed to take advantage of the fact that video-on demand, telecommuting, and Internet access traffic are inherently asymmetrical. The user(73)a brief message up to the network and receives a ton of data coming back, either a movie or a piece of data download. Under such a scenario, low-speed traffic to the network is just fine. ADSL .delivers high(74)where you need it and only uses a single copper pair. Through multiplexing, it also reserves(75)of the bandwidth for POTS.

(11)

(12)

(10)

(9)

With hundreds of millions of electronic transactions taking place daily, businesses and organizations have a strong incentive to protect the(66)of the data exchanged in this manner, and to positively ensure the identities of those involved in the(67). This has led to an industry-wide quest for better, more secure methods for controlling IT operations, and for deploying strong security(68)deeply and broadly throughout networked infrastructures and client devices. One of the more successful concepts to engage the imaginations of the security community has been the development of standards-based security.(69)that can be incorporated in the hardware design of client computers. The principle of encapsulating core security capabilities in(70)and integrating security provisions at the deepest levels of the machine operation has significant benefits for both users and those responsible for securing IT operations.