ISO/OSI参考模型的7层协议中第2层是(35)。

At which layer of the OSI model dose PPP perform?（）

OSI参考模型（OSI/RM）的全称是开放系统互连参考模型（Open.System.Interconnection.Reference.Model，OSI/RM）。

Sand painting has also called dry or earth painting and is practiced by several American Indian artists.

（1） analysis emphasizes the drawing of pictorial system models to document and validate both existing and/or proposed systems．Ultimately, the system models become the（2） for designing and constructing an improved system. （3） is such a technique. The emphasis in this technique is process-centered．Systems analysts draw a series of process models called （4） . （5） is another such technique that integrates data and process concerns into constructs called objects.

The(7)technique involves using project characteristics in a mathematical model to predict total project cost. Models can be simple or complex.

The（）technique involves using project characteristics in a mathematical model to predict total project cost. Models can be simple or complex.

As a CCNA candidate, you will be expected to know the OSI model very well. Which of the following are associated with the application layer (layer 7) of the OSI model? (Choose two)

A （）, sometimes called filters, is a device designed to prevent the passage of unwanted solids into the system.

Strainers, sometimes called （）, are devices designed to prevent the passage of unwanted solids into or further along a system.

（）sometimes called filter, is a device designed to prevent the passage of unwanted solids into the system.

In astern towing，a tow span，also called the tow bar or towing arch，is used to（）.