更多"The usual way to ensure reliable de"的相关试题:
[单项选择]
The usual way to ensure reliable delivery is to provide the (20) with some feedback about what is happening at the other end of the line. Typically, the protocol calls for the receiver to send back special (21) flame bearing positive or negative (22) about the incoming frames. If the sender receives a positive acknowledgement about a frame, it knows the frame has arrived safely. On the other hand, a negative acknowledgement means that’ something has gone wrong, and the frame must be transmitted again.
An additional complication comes from the possibility that hardware troubles may cause a flame to (23) completely. In this case, the receiver will not react at all, since it has no any reason to react. It should be clear that a protocol in which the sender transmits a frame and then waits for an acknowledgement, positive or negative, will hang forever if a frame is ever lost due to, for example, (24) hardware.
（20）是（）
A. receiver
B. controller
C. sender
D. customer
[单项选择]What is the main problem caused by the usual way of plowing
A．The crop’s blooming period is delayed.
B．The roots of crops are cut off.
C．The top soil is seriously damaged.
D．The growth of weeds is accelerated.
[简答题]E-commerce is coming of age, but not in the way predicted in the bubble years. (71.) Now some of the dotcoms are making real profits, but the business world has become much more cautious about the internet’s potential. The funny thing is that the wild predictions made at the height of the boom—namely, that vast chunks of the world economy would move into cyberspace—are, in one way or another, coming true.
(72.) According to America’s Department of Commerce, online retail sales last year rose by 26%, to $55 billion. That sounds a lot of money, but it amounts to only 1.6% of total retail sales. (73.) The vast majority of people still buy most things in the good old “bricks-and-mortar” world.
(74.) But the commerce department’s figures deal with only part of the retail industry. (75.) For instance，they exclude online travel services, one of the most successful and fastest-growing sectors of e-commerce. InterActiveCorp (IAC), the owner of expe
