What is the Differences between OSI model and
TCP/IP model?
Network Models:
- Using a formal model allows us to deal with various aspects of
Networks abstractly.
- We will look at two popular models
OSI reference model
TCP/IP model
- Both models are based on the concept of layering.
Layering:
- Divide a task into sub-tasks and then solve each sub-task
independently.
- Establishing a well defined interface between layers makes porting
easier.
- Major Advantages:
Code Reuse
Extensibility
OSI Reference Model:
The International Standards Organization (ISO) proposal for the
standardization of the various protocols used in computer networks
(specifically those networks used to connect open systems) is called the
Open Systems Interconnection Reference Model(1984), or simply the
OSI model.
Why layered model?
Layers with Functions:
The Seven Layers of the OSI Reference Model
- The application (upper) layers
Layer 7: Application
Layer 6: Presentation
Layer 5: Session
- The data-flow (lower) layers
Layer 4: Transport
Layer 3: Network
Layer 2: Data link
Layer 1: Physical
Interface protocols: describe the communication between layers on the
same endpoint.
Peer-to-peer protocols describe communication between peers at the
same layer.
Similarities between OSI Reference and TCP/IP Reference Model
Both are layered architecture.
Layers provide similar functionalities.
Both are protocol stack.
Both are reference models.
Comparison of OSI Reference Model and TCP/IP Reference Model
OSI(Open System Interconnection) TCP/IP(Transmission Control Protocol /
Internet Protocol)
1. OSI is a generic, protocol 1. TCP/IP model is based on standard protocols
independent standard, acting as a around which the Internet has developed. It is a
communication gateway between the communication protocol, which allows
network and end user. connection of hosts over a network.
2. In OSI model the transport layer 2. In TCP/IP model the transport layer does not
guarantees the delivery of packets. guarantees delivery of packets. Still the TCP/IP
model is more reliable.
3. Follows vertical approach. 3. Follows horizontal approach.
4. OSI model has a separate 4. TCP/IP does not have a separate
Presentation layer and Session layer. Presentation layer or Session layer.
5. Transport Layer is Connection 5. Transport Layer is both Connection Oriented
Oriented. and Connection less.
6. Network Layer is both Connection 6. Network Layer is Connection less.
Oriented and Connection less.
7. OSI is a reference model around 7. TCP/IP model is, in a way implementation
which the networks are built. of the OSI model.
Generally it is used as a guidance
tool.
8. Network layer of OSI model 8. The Network layer in TCP/IP model
provides both connection oriented provides connectionless service.
and connectionless service.
9. OSI model has a problem of fitting 9. TCP/IP model does not fit any protocol
the protocols into the model.
10. Protocols are hidden in OSI 10. In TCP/IP replacing protocol is not easy.
model and are easily replaced as the
technology changes.
11. OSI model defines services, 11. In TCP/IP, services, interfaces and
interfaces and protocols very clearly protocols are not clearly separated. It is also
and makes clear distinction between protocol dependent.
them. It is protocol independent.
12. It has 7 layers 12. It has 4 layers
OSI Model and TCP/IP
Model
Diagrammatic Comparison between OSI Reference Model and
TCP/IP Reference Model
Differences of the OSI
and TCP/IP models
TCP/IP combines the presentation
and session layer into its application
layer.
TCP/IP combines the OSI data link
and physical layers into one layer.
TCP/IP appears simpler because it
has fewer layers.
TCP/IP transport layer using UDP
does not always guarantee reliable
delivery of packets as the transport
layer in the OSI model does.
