The OSI Model: Part 5 - Session Layer

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Time
15 hours 43 minutes
Difficulty
Advanced
CEU/CPE
16
Video Transcription
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>> Layer 5 of the OSI reference model
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is known as the session layer.
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That's really a good name for it
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because it is all about controlling a session.
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When we talk about a session,
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we're talking about an application
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to application connection.
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At this layer, if you think about,
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for instance, I have a web browser,
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and that web browser connects to
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a web server and opens up a session on the web server.
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That's what layer 5 is all about.
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Its job is to establish, maintain,
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and tear down a communication
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or connection between computers.
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Setup, tear down
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maintenance of a communication pathway,
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that session layer, full duplex versus half duplex.
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When we talk about duplex,
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it's a matter of communicating.
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It's almost like we had simplex communication,
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which was just one-way communication.
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Then we move to half duplex,
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which is like a walkie-talkie.
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One system could transmit at a time.
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Communication can happen both ways,
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but systems couldn't send and receive at the same time.
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Now, I'll mention that
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hubs were primarily half duplex in earlier switches.
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Most switches today are full duplex,
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which means they can send and receive at the same time.
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That capability is layer 5.
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Remote procedure calls.
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When I open up a session on another computer
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and perform maintenance or whatever that might be,
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that connection is going to be layer 5.
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I think that's probably a layer that you'll
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see less of on the exam.
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I don't think you'll see a lot of questions,
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but things like session hijacking,
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establishing that session,
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having session IDs, intercepting session IDs,
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and stepping in and replacing
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a host in a session, that's layer 5.
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That's a simple session layer setup,
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maintenance, and tear down of a connection.
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