The document discusses the TCP/IP model and its layers. TCP/IP was created after the OSI 7 layer model for use on the Internet. It has four or five layers: Application, Transport, Internet, and Network Access layers. The Network Access layer can also be split into Physical and Data Link layers. Each layer of TCP/IP has specific functions, such as the Transport layer handling error detection and recovery, and the Internet layer using IP and ARP protocols.

3. WHY TCP/IP
• TCP/IP, is a suite of protocols used for communication over
the internet. The TCP/IP model was created after the OSI
7 layer model for two major reasons.
• First, the foundation of the Internet was built using the
TCP/IP suite and through the spread of the World Wide
Web and Internet, TCP/IP has been preferred.
• Second, a project researched by the Department of
Defense (DOD) consisted of creating the TCP/IP protocols.

4. TCP/IP LAYERS
• The TCP/IP model, similar to the OSI
model, is comprised of layers. It contain
four or five layer.
• Some people use the Application,
Transport, Internet and Network Access
layers.
• Others split the Network Access layer
into the Physical and Data Link
components.

5. LAYER 4 - APPLICATION
• This layer is comparable to the application,
presentation, and session layers of the
OSI model.
• It provides a way for applications to have
access to networked services.
• This layer also contains the high level
protocols.
• The main issue with this layer is the ability
to use both TCP1 and UDP2 protocols.

6. LAYER 3-TRANSPORT
• This layer acts as the delivery service
used by the application layer.
• The transport layer also handles all error
detection and recovery.
• It uses checksums, acknowledgements, and
timeouts to control transmissions and end
to end verification.
• Unlike the OSI model, TCP/IP treats
reliability as an end-to-end problem.

7. LAYER 2-INTERNET
• The upper layers are responsible for
the reordering of the data.
• This layer can be compared to the
network layer of the OSI model.
• IP and ARP6 are the major protocols
used at this layer.

8. LAYER 1-NETWORK
ACCESS
• This a combination of the Data Link and
Physical layers of the OSI model
• The frame format is dependent on the
system being used, for example Ethernet
LAN, Frame relay9, etc.
• This layer has actually not been specified
in details because it depends on which
technology is being used such as Ethernet.
• So freedom is given to this layer as far as
implementation is concerned.