OSI session layer and presentation layer 到底是干啥的?

the Session layer is responsible for establishing ,maintaining, and terminating communication sessions between two computers
the primary technology within layer is a gateway.
--這個層次主要的作為類似應用網關
the following protocols operate within the Session layer:
Secure Socket Layer(SSL)
Network File System(NFS)
Structured Query Language(SQL)
Remote Procedure Call(RPC)

The presentation layer is responsible for transforming data received from the application layer into a format that any system following the OSI model can understand. it imposes common or standardized structure and formatting rules onto the data.
--這個層次主要是標准化,格式化數據
the Presentation layer is also responsible for encryption and compression
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