网络数据传输 | 封装与解封装详解

注：机翻，未校对。

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Encapsulation, Decapsulation and Queuing

The goal of networks is to transmit data from one host to another.
网络的目标是将数据从一个主机传输到另一个主机。

Encapsulation 封装

To achieve this goal, each layer adds its own header to the data. A header contains information specific for that layer, and it precedes the data itself.
为了实现此目标，每一层都会向数据添加自己的标头。标头包含特定于该层的信息，并且位于数据本身之前。

Consider a case where we have a lookup service, used in order to find a person’s phone number, given the person’s name. The data consists of the person’s first and last name.
考虑一个案例，我们有一个查找服务，用于查找一个人的电话号码，给定这个人的名字。数据由此人的名字和姓氏组成。

Before the packet is sent, the fifth layer might add its own header, describing that this is a REQUEST packet. The header might also specify that this is a request to map from a person’s name to a phone number, and not vice versa.
在发送数据包之前，第五层可能会添加自己的标头，描述这是一个 REQUEST 数据包。标头还可以指定这是从人员姓名映射到电话号码的请求，反之亦然。

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