osi七层模型,表示层
The primary goal of this layer is to take care of the syntax and semantics of the information exchanged between two communicating systems. Presentation layer takes care that the data is sent in such a way that the receiver will understand the information(data) and will be able to use the data. Languages(syntax) can be different of the two communicating systems. Under this condition presentation layer plays a role translator.
该层的主要目标是照顾两个通信系统之间交换的信息的语法和语义 。 表示层要注意以如下方式发送数据：接收方将理解信息(数据)并能够使用该数据。 两种通信系统的语言(语法)可以不同。 在这种情况下，表示层将扮演角色翻译器的角色。
In order to make it possible for computers with different data representations to communicate, the data structures to be exchanged can be defined in an abstract way. The presentation layer manages these abstract data structures and allows higher-level data structures(eg: banking records), to be defined and exchanged.
为了使具有不同数据表示形式的计算机能够进行通信，可以以抽象的方式定义要交换的数据结构。 表示层管理这些抽象数据结构，并允许定义和交换更高级别的数据结构(例如银行记录)。
表示层的功能 (Functions of Presentation Layer)Translation: Before being transmitted, information in the form of characters and numbers should be changed to bit streams. The presentation layer is responsible for interoperability between encoding methods as different computers use different encoding methods. It translates data between the formats the network requires and the format the computer.
翻译：在传输之前，应将字符和数字形式的信息更改为比特流。 由于不同的计算机使用不同的编码方法，因此表示层负责编码方法之间的互操作性。 它在网络所需的格式和计算机的格式之间转换数据。
Encryption: It carries out encryption at the transmitter and decryption at the receiver.
加密：它在发送方执行加密，在接收方进行解密。
Compression: It carries out data compression to reduce the bandwidth of the data to be transmitted. The primary role of Data compression is to reduce the number of bits to be 0transmitted. It is important in transmitting multimedia such as audio, video, text etc.
压缩：执行数据压缩以减少要传输的数据的带宽。 数据压缩的主要作用是减少要传输的比特数。 在传输音频，视频，文本等多媒体时，这一点很重要。
表示层的设计问题 (Design Issues with Presentation Layer)To manage and maintain the Syntax and Semantics of the information transmitted.
管理和维护所传输信息的语法和语义 。
Encoding data in a standard agreed upon way. Eg: String, double, date, etc.
以商定的标准对数据进行编码 。 例如：字符串，双精度，日期等。
Perform Standard Encoding on wire.
在线执行标准编码 。
翻译自: https://www.studytonight.com/computer-networks/osi-model-presentation-layer
osi七层模型,表示层