4. Application Layer
It contains applications that facilitate network
communication.
Such as Hypertext Transfer Protocol (HTTP) for browsing
the World Wide Web transferring files on net-works and over
the Web.
At the Application layer, the data still resembles something
that people can read and interpret.
5. Presentation Layer
At the Presentation layer (Layer 6) data is first converted
into a form that can be sent over a network.
At this layer data is compressed and decompressed and
encrypted or decrypted.
6. Session Layer
It is responsible for establishing, synchronizing,
maintaining, and then terminating the sessions between
computers.
It also handles error detection and notification.
7. Transport Layer
This layer is responsible for resending any packets that do
not receive an acknowledgment from the destination
address.
It's also responsible for any problems that are associated
with fragmentation of packets.
8. Network Layer
The Network layer (Layer 3) is responsible for providing the
mechanism by which data can be moved from computer to
computer or from network to network.
The Network layer does not actually move the data; instead
it provides the addressing information and route discovery
that are necessary to move the data to the appropriate
location.
9. The Network layer contains many protocols that facilitate
these services.
Internet Protocol (IP),
Internet Control Message Protocol (ICMP),
Internet Group Management Protocol (IGMP),
Address Resolution Protocol (ARP).
10. Data Link Layer
The Data Link layer (Layer 2) is responsible for sending data
to the Physical layer so that it can be put onto the "wire" or
network media.
The Data Link layer is subdivided into two other layers:
Logical Link Control (LLC)
Media Access Control (MAC)
11. Physical Layer
The Physical layer (Layer 1) defines the physical
characteristics of the network such as the type of
cable that must be used as well as the voltage that
will be used to transmit data through the network.
