"Session layer" in OSI 7-layer reference model is responsible for creating, maintaining and closing sessions between hosts. Is it possible to distinguish "session layer" in Linux network stack? What are the protocols used? For example if one downloads an ASCII text file using HTTP, then does "session layer" signal the transport layer protocols to create a connection?

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    The Linux kernel is primarily TCP/IP, and so mainly is aimed at the TCP/IP model not the OSI model. The IP model simplifies and merges some of the layers.
    – Zoredache
    Sep 18, 2013 at 22:57

1 Answer 1


While all introduction to primitives of networking refer to OSI model, in Linux the basic networking stack uses four-layer model "Internet Model" (Application Layer, Transport Layer, Network Layer, Link Layer). By using this model, "Linux Networking" does not concern itself with the OSI model's details of session layer semantics and therefore does not consider a session layer.

Session management in connection with the typical transport protocols is contained in the transport-layer protocols, or otherwise considered the realm of the application layer protocols and belongs to the user space problems.

Application Layer of this model belongs to user space, all others in kernel space and device drivers ( system call interface, agnostic protocol interface, network protocols, device agnostic interface, device drivers), then physical hardware devices.

Hope this help

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