问题 问答题 简答题

简述R4结构中Mc、Nb、Nc接口的定义及作用。

答案

参考答案:

G.MSCServer与MGW之间的Mc接口:支持多种呼叫模式、多种媒体的灵活的连接处理。使用IETFMEGACO(即H.248)协议。

M.SCServer与(G)MSCServer之间的Nc接口:完成局间的呼叫控制。使用基于ISUP的BICC呼叫控制协议。

M.GW之间的Nb接口:完成承载方式的控制和用户信息(语音、数据、图象、多媒体)的传送,完成不同媒体帧格式之间的转换。可以使用RTP/UDP/IP或AAL2/ATM协议。

单项选择题
阅读理解

Everyone should visit a lighthouse at least once.

The most important reasons for such a visit is to realize how our ancestors(祖先) battled nature with the basic tools they had. They had only basic ways of creating light, and yet they found a way of using this simple technology in isolated(孤零零的)places to save ships from hitting rocks.

Secondly, visiting lighthouses will help us to understand the lives of lighthouse keepers. By their very nature, lighthouses were built on some rocks of cliffs. Thus, the lighthouse keepers often lived lonely lives. To walk around their small home, and imagine the angry storm outside beating against the walls, is to take a step towards understanding the lives they had.

The reasons for a visit to a lighthouse are not all so backward-looking in time. It is true that lighthouses were built in out-of-the-way places. But on a pleasant sunny summer day, this very isolation has a natural beauty that many people will love to experience. Therefore, with the gentle waves touching all round the lighthouse, the visitor is likely to think it is a world preferable to the busy and noisy modern life.

Another reason for considering a visit is that the lighthouses themselves can be very attractive buildings. Mankind could often not be content just to put up a basic structure, but felt the need, even in such an isolated place, to build with an artistic touch. The result is a view for tired eyes to enjoy.

Finally, lighthouses have a romantic attraction, summed up by the image of the oil-skin coated keeper climbing his winding stairs to take care of the light to warn ships and save lives.

67. What is the reason to look back into the past of a lighthouse?

A. To escape from the busy and noisy city.

B. To look for the tools used by our ancestors.

C. To experience the natural beauty of a lighthouse.

D. To learn about the living condition of lighthouse keepers.

68. The underlined phrase “out-of-the-way” in Paragraph 4 means ____________.

A. far-away     B. dangerous      C. ancient       D. secret

69. Lighthouses were often built with an artistic touch _________.

A. to attract visitors       B. to guide passing ships

C. to give a pleasant sight  D. to remember lighthouse keepers

70. How many reasons are mentioned for a visit to lighthouse?

A. Three        B. Four         C. Five          D. Six