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network-programmingtcpoperating-systemlayerosi

Where does the Transport Layer operate?

I'd like to know where the Transport Layer of the OSI model is running in a computer system. Is it part of the Operating System? Does it run in its own process or thread? How does it pass information up to other applications or down to other layers?

Solution

  • I'd like to know where the Transport Layer of the OSI model is running in a computer system.

    It isn't. The OSI model applies to the OSI protocol suite, which is defunct, and not running anywhere AFAICS. However TCP/IP has its own model, which also includes a transport layer. I will assume that's what you mean hereafter.

    Is it part of the Operating System?

    Yes.

    Does it run in its own process or thread?

    No, it runs as part of the operating system.

    How does it pass information up to other applications

    Via system calls, e.g. the Berkeley Sockets API, WinSock, etc.

    or down to other layers?

    Via internal kernel APIs.