网络层（来自 Computer Networks，Tanenbaum）
“每一层的目的都是为用户提供某些服务 ，
现在每一层的目的都是为更高层提供服务。最高层怎么样，没有更多的层可以提供服务了 所以要么句子不正确，要么句子缺失。
"The purpose of each layer is to offer certain services to the
higher layers, shielding those layers from the details of how the offered services are actually implemented."
Now the purpose of each layer is to offer services to the higher layers. How about the highest layer, there is no more layers to offer services to, so either is sentence isn't correct, or it's missing.
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嗯，通常上面的服务是人类可读的数据。无论是网页还是电子邮件，因此您可以说上面的层是人类或至少是浏览器中的解析器。然而，无论如何，人们可以在上面再分层，就像 Twitter API 中所做的那样，例如，它是通过 HTTP 来回发送的消息。因此，7 osi 层如何形成并不像以前那样明确。
Well, usually the service above that is human readable data. Whether it be a webpage or an email, so you could say the layer above is the human or at least the parser in the browser. However one can layer another layer on top anyway, as is done in say the twitter API, it's messages being sent back and forth across HTTP for example. So how 7 osi layers is not as clear cut as it used to be.
应用层是一切开始和结束的层。因此，不需要将数据传递到更高级别。这是语句的异常
The application layer is the layer where everything starts and ends. Therefore, there is no requirement of passing data to a higher level. It's an Exception of the statement