Learning by Doing: CISCO Certified Network ... - SCN Research

Network
Data Link
Physical
Provides connectivity and path selection between two end systems where
routing occurs. Segments are encapsulated into packets here.
Concerned with physical addressing, network topology, and media access.
Packets are encapsulated into frames here.
Describes the various types of networking media. Frames are converted into
bits here. Defines the electrical and functional specifications for activating
and maintaining the link between end systems.
note: stress underlined areas as “buzz words” to remember for each layer.
Let's take a peek at each layer…
Now when you go to communicate over the network your host computer will begin
readying for transmission from the top down. Therefore, we will start with Layer 7: the
Application layer.
Layer 7: the Application layer
The official definition is the application layers "identifies and establishes the availability
of intended communication partners, synchronizes cooperating applications, and
establishes agreement on procedures for error recovery and control of data integrity.
“browsers” This is the layer the user will see. Correlation's here include FTP, HTTP,
MS-Word, etc.
Visual representation: Application box (MS-WORD, etc), big eyes
Layer 6: The Presentation layer
The official definition of the presentation layer is that it "translates multiple data
representation formats by using a common data representation format. “concerned with
data structures and negotiation data transfer syntax” “encoding, representation of data,
ASCII”
This is the layer that is in charge of "Super Secret Spy Stuff" and "Key" coding. This is
where we compress and encrypt our information before sending. Examples here include
ASCII and PKZIP.
Visual Representation: sunglasses and hat; big key
Layer 5: The Session layer
The official definition of the session layer is that it "synchronizes dialogue between
presentation layer entities and manages their data exchange. Information is encapsulated
into data blocks here."
This is the layer that says "HEY!" I want to establish a networking session. In fact, if you
have internet access from your home computer then you may even see the message
"establishing session" during the connection process.
Visual Representation: Big lips
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