OSI Model
When I say it is working its way through the stack, here is what that means.
While it can appear in an instant - the message/data had to go through the
stack as part of its journey, it can't do it otherwise - is must start at 7 and to
1 over to the recipient and reverse order 1 and to 7 to see
Communications between computers over networks are made possible by
protocols
Protocol is a set of rules and restrictions that define how data is transmitted
over a network medium.
OSI model serves as an abstract framework or theoretical model for how
protocols should function in an ideal world on ideal hardware
OSI Functionality
OSI model divides networking tasks into 7 distinct layers - each layer is
responsible for performing specific tasks or operations for the ultimate goal
of supporting data exchange (network communication)
Layers are always numbered from bottom to top - in order specifically to
indicate how information flows through the various levels of communication -
each layer communicates directly with the layer above it as well as the layer
below
Application 7
Presentation 6
Session 5
Transport 4
Network 3
Data Link 2
Physical 1
1
, OSI model is an open network architecture guide for network product
vendors - provides a common foundation for the development of new
protocols, network services, and even hardware devices
Encapsulation/De-encapsulation - protocols based on the OSI model employ a
mechanism called encapsulation - Encapsulation is the addition of a header
and maybe a footer to the data received by each layer from the layer above
before it is handed off to the layer below
As the message is encapsulated at each layer, the previous layer's header
and payload combine to become the payload of the current layer -
encapsulation occurs as the data moves down through the OSI model - so
think of word doc with detailed information (payload) and the header tells
you who it is from or what it is about - when the next layer gets that, the
entire page text and header are that layers full payload and so on
De-encapsulation is the reverse when the payload descends down the OSI
model to the physical layer
1. Application layer creates a message
2. Application layer passes that message to the presentation layer
3. Presentation layer encapsulates the message, adding information to it -
usually at the beginning of the message (it's header) and/or to the
footer
4. Process of passing the message down and adding layer specific
information continues until the message reaches the physical layer
5. Physical layer, the message is converted to electrical impulses that
represent bits and is transmitted over the physical connection
6. Receiving computer captures the bits from the physical connection and
re-creates the message in the physical layer
7. Physical layer coverts the message from bits into the DATA LINK frame
and send the message up to the DATA LINK layer
8. The DATA LINK layer strips its information an sends the message up to
the network layer
9. This process of de-encapsulation is performed until the message
reaches the application layer
2
When I say it is working its way through the stack, here is what that means.
While it can appear in an instant - the message/data had to go through the
stack as part of its journey, it can't do it otherwise - is must start at 7 and to
1 over to the recipient and reverse order 1 and to 7 to see
Communications between computers over networks are made possible by
protocols
Protocol is a set of rules and restrictions that define how data is transmitted
over a network medium.
OSI model serves as an abstract framework or theoretical model for how
protocols should function in an ideal world on ideal hardware
OSI Functionality
OSI model divides networking tasks into 7 distinct layers - each layer is
responsible for performing specific tasks or operations for the ultimate goal
of supporting data exchange (network communication)
Layers are always numbered from bottom to top - in order specifically to
indicate how information flows through the various levels of communication -
each layer communicates directly with the layer above it as well as the layer
below
Application 7
Presentation 6
Session 5
Transport 4
Network 3
Data Link 2
Physical 1
1
, OSI model is an open network architecture guide for network product
vendors - provides a common foundation for the development of new
protocols, network services, and even hardware devices
Encapsulation/De-encapsulation - protocols based on the OSI model employ a
mechanism called encapsulation - Encapsulation is the addition of a header
and maybe a footer to the data received by each layer from the layer above
before it is handed off to the layer below
As the message is encapsulated at each layer, the previous layer's header
and payload combine to become the payload of the current layer -
encapsulation occurs as the data moves down through the OSI model - so
think of word doc with detailed information (payload) and the header tells
you who it is from or what it is about - when the next layer gets that, the
entire page text and header are that layers full payload and so on
De-encapsulation is the reverse when the payload descends down the OSI
model to the physical layer
1. Application layer creates a message
2. Application layer passes that message to the presentation layer
3. Presentation layer encapsulates the message, adding information to it -
usually at the beginning of the message (it's header) and/or to the
footer
4. Process of passing the message down and adding layer specific
information continues until the message reaches the physical layer
5. Physical layer, the message is converted to electrical impulses that
represent bits and is transmitted over the physical connection
6. Receiving computer captures the bits from the physical connection and
re-creates the message in the physical layer
7. Physical layer coverts the message from bits into the DATA LINK frame
and send the message up to the DATA LINK layer
8. The DATA LINK layer strips its information an sends the message up to
the network layer
9. This process of de-encapsulation is performed until the message
reaches the application layer
2
