Do Transport Layer (TCP and UDP) reads/inspects IP headers (Src IP,Destination IP)?

This is a discussion on Do Transport Layer (TCP and UDP) reads/inspects IP headers (Src IP,Destination IP)? within the Networking/Device Communication forums, part of the General Programming Boards category; We all know that a TCP socket is identified by a four tuple entry: src ip, dest ip, src port ...

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    Question Do Transport Layer (TCP and UDP) reads/inspects IP headers (Src IP,Destination IP)?

    We all know that a TCP socket is identified by a four tuple entry: src ip, dest ip, src port dest port

    TCP does the job of Multiplexing and Demultiplexing the Data from/to differnt processes running on the host.

    In case of Demultiplexing, Destination IP information is there only in IP Headers. How come Dest IP is read by Transport Layer (TCP)?

    Plz explain I m very much confused?

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    Headers can't "read" or "inspect" anything. They're little bits of data that your router/other devices read and understand.

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    Quote Originally Posted by memcpy View Post
    Headers can't "read" or "inspect" anything. They're little bits of data that your router/other devices read and understand.

    I think u misunderstood my question. I am not headers will read somethinh. I am saying that they will be read by the corresponding layers Example: L2 headers will be read by the Data Link Layer. L3 Headers will be read by Network layer and so on.

    Now my question is That Src and Dest IP are at Layer 3 headers, Are they inpected/read by the Layer 4 TCP/UDP layer since they do the job of demultiplexing the data to the right socket and thus to identify a socket uniquely IP+port both information is required

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    You should give the RFCs a read, especially this > RFC 1122 - Requirements for Internet Hosts - Communication Layers

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