Difference Between TCP/IP and OSI Model

TCP/IP and OSI are communication networking protocols that facilitates the communication between computers over a network. Both these protocols follow a step-by-step procedure (also called layers) for communication purposes. Moreover, these models convert raw data into packets or units of digital information and help them reach their destination node. While these are a few of the similarities, in this article we will be talking about TCP/IP protocol vs OSI or the difference between TCP/IP and OSI models.

Before we move on to list the important differences between the two, let us first learn what is TCP/IP, layers of TCP/IP and what is OSI and layers of OSI. Understanding the definitions of TCP/IP protocol and OSI model will help us to learn the differences at a comparatively quicker rate.

So, without any delay, let us start our reading journey!

What is TCP/IP?

• The full form of TCP/IP is Transmission Control Protocol/Internet Protocol. Typically, protocol is a set of rules that anyone needs to abide by to carry out a specific task. In the language of computers, protocol are guidelines that describes how devices communicate with each other. TCP/IP is one such protocol suite that facilitates communication across devices.
• TCP/IP is a protocol suite because it is a composite protocol comprising many individual protocols. The protocols under TCP/IP are HTTP, FTP, DNS, SMTP etc.
• TCP/IP can be divided into two parts- 1. TCP and 2. IP. TCP segregates data into chunks and transfers it via internet. The function of IP on the other hand is to ensure that the chunks reach their destination. To carry out the protocol functions, internet connectivity is a must. TCP/IP can also be called internet reference model.
• It was developed by DoD or Department of Defence, precisely by the Defense Advanced Research Projects Agency in the 1960s for its use in ARPANET (a wide area network that existed before the internet).

Layers of TCP/IP

TCP/IP protocols comprises 4 layers that performs their individual functionalities to transfer the data from the sender to the receiver. These layers are as follows:

1. Application Layer
2. Transport Layer
3. Internet Layer
4. Network Access Layer

Let us describe these layers in detail:

1. Application Layer

Application Layer is the top layer of the TCP/IP Protocols. With the help of this layer, network service and interface are made available to the user. As you know, an interface enables interaction on the part of the user. Therefore, this layer can be said to facilitate interaction from the user via applications like e-mail, browser, FTP etc. Application Layer is composed of several protocols like HTTP, DNS, FTP, TFTP, SMTP, SNMP, TELNET etc.

2. Transport Layer

• Transport Layer is responsible for the transmission of data. This layer ensures flow control and error checking and provides end-to-end service. Flow control means the right flow of data between the sender and the receiver at a mutually acceptable speed.
• Transport Layer has two divisions- 1. TCP (Transmission Control Protocol) and 2. UDP (User Datagram Protocol). Let us check the differences between TCP and UDP to understand them better.
• TCP is a reliable protocol as it provides guaranteed message delivery and can also be termed “connection-oriented”. It has also provisions for error-detection. If error is spotted, it can perform retransmission of data. An example can be uploaded videos on YouTube.
• UDP on the other hand is an unreliable protocol and it cannot guarantee that the message will be delivered to the right destination. Therefore, it is a connectionless protocol. An example can be a poor network connectivity that might interrupt phone calls.
• However, UDP is better than TCP in terms of its speed. So, if you are streaming videos or gaming, UDP will help you out as its services are faster. If you want a more reliable choice, TCP is the best!

3. Internet Layer

Internet Layer provides a connectionless service and the best delivery route for packets (a chunk of digital information). The protocols that come within the Internet Layer are IP, ICMP, ARP, RARP, IGMP. THE IP Data gram within the Internet Layer contains the source IP address and destination IP address that ensures delivery or reception of data.

4. Network Interface Layer

Network Interface Layer is the lowest layer in TCP/IP protocol. It sends the packets or the digital data to the destination. It doesn’t define any protocol but consists of all the standard protocols. It is also known host-to-Network layer or data link layer as its protocols operate only on a link. These protocols include Ethernet and ARP.

What is OSI model?

The full form of OSI model is Open System Interconnection. The OSI model was first published in the year 1984 by the ISO or International Organization for Standardization. OSI is a conceptual model that defines how applications can communicate over a network. Although it is a communication networking protocol, it is not practically used for communication. The modern internet is based on the TCP/IP model but ISO model is also widely used.

Layers of OSI model

There are 7 layers of OSI model. The TCP/IP is similar to the OSI model in the fact that there are three layers that are common in both. These three layers are the application layer, transport layer and network layer. These layers collaborate with each other for data transmission over networks across the globe. Let us now look at the 7 layers of the OSI model:

1. Physical Layer
2. Data Link Layer
3. Network Layer
4. Transport Layer
5. Session Layer
6. Presentation Layer
7. Application Layer

All of these 7 layers of the OSI model are defined below:

1. Physical Layer

Physical Layer is the lowest layer of the OSI model, also called as Layer 1. It is the last layer from the sender’s part and the topmost layer from the receiver’s end. The physical layer enables physical connection between devices. The physical parts typically include plugs, connectors, cable types etc. Information exists in the form of bits (also called packets in network layer) and can only be transferred when converted to either digital or analog signal. While receiving data, it will receive the signal and convert it into 0s and 1s. After the conversion, the physical layer would send them to the next layer i.e., Data Link Layer.

2. Data Link Layer

The Data Link Layer (DLL) is also known as Layer 2. This layer is responsible for delivery of data via node-to-node connection where data is packaged into frames. Frames are units of data that is used in the OSI model’s data link layer. It is different from packets in the fact that packets are units of data used in the network layer. The data link layer also takes care of errors that might have occurred at the physical level. The two sub-layers of DLL, Media Access Control (MAC) and Logical Link Control (LLC) provides data flow control.

3. Network Layer

The function of Network Layer is the transmission of data from one host to the other across different networks. It receives data in the form of packets (frames) from the data link layer. The layer then carries out routing and logical addressing. It finds the shortest and possibly the best route to transmit those packets (data) amidst a range of several other routes, which is termed routing. Regarding logical addressing, the Network Layer positions the sender and receiver’s IP addresses in the header that keep such addresses unique to each device universally. The packets are delivered to their destination based on these IP addresses.

4. Transport Layer

The Transport Layer accepts services from the Network Layer. It performs similar functions to that of the TCP/IP protocols. End to end delivery, error-checking, data-flow are its attributes. The data in the Transport Layer is referred to as segments and from a sender’s side, the segments are sent to the network Layer.

5. Session Layer

The session Layer is responsible for the connection and session establishment and termination between computers. Precisely, it establishes, maintains, synchronizes and terminates sessions between end-user applications. Once the data is received it is marked and resynchronized to prevent data loss. Computers can communicate in full-duplex mode where both stations can send and receive data simultaneously. It can also communicate through half-duplex mode where data is transmitted and then received but never simultaneously.

6. Presentation Layer

Message or data units are extracted from session Layer and manipulated in a particular format for transmission. It allows encryption of data from a sender where data is translated to an unreadable format or code. It also allows decryption from a receiver where data is translated to a readable format or where data is decoded. In other words, ciphertext is translated to plain text. The presentational layer also compresses data and is even referred to as the translation layer or Syntax layer.

7. Application Layer

Data is transmitted from the Presentation Layer to the Application layer which is the topmost layer in the OSI model. This layer ensures proper communication is established between computer systems or networks. It enables the user to interact on network where several activities can be carried out like reading messages, transferring files etc via user-end applications.

Difference between TCP/IP and OSI Model

The differences between TCP/IP and OSI model can be said to be a subtle one.

Now, that we have gone through the TCP/IP protocols and OSI model and their layers, it will be easy to understand the differences between them.

TCP/IP vs OSI:

1. The full form of TCP/IP is Transmission Control Protocol/Internet Protocol while the full form of OSI is Open Systems Interconnection.

2. TCP/IP is a communication standard protocol or mandated protocol that facilitates communication between hosts or computers over the network. OSI is a structured or conceptual model that is responsible for the functioning of the network. It is a protocol independent standard that serves as a connection gateway between the network and the user.

3. TCP/IP protocol dates much back than OSI model. TCP/IP was first introduced in the 1960s whereas the OSI model was first introduced in 1980s. In 1982, TCP/IP became the standard language of ARPANET (Advanced Research Project Agency Network).

3. TCP/IP has four layers- Application Layer, Transport Layer, Internet Layer and Network Access Layer. OSI model has 7 layers- Physical Layer, Data Link Layer, Network Layer, Transport Layer, Session Layer, Presentation Layer and Application Layer.

4. TCP/IP follows a horizontal approach while OSI model follows a vertical approach.

5. A layer in TCP/IP model is both connection-oriented and connectionless. For example, TCP and UDP in transport layer of TCP/IP protocol are connection-oriented and connectionless respectively. In OSI model, the transport layer is only connection-oriented.

6. The network interface layer in TCP/IP corresponds to the Data Link and Physical Layers of the OSI model. Thus, the data link layer and physical layer are seperate layers of the OSI model whereas the former two co-exists as one in TCP/IP model.

7. The application layer in TCP/IP is a combination of the functionalities of the session layer, presentation layer and application layer in the OSI model. Therefore, whereas the three layers at the bottom exist seperately in the OSI model, they are combined into one layer i.e., application layer in the TCP/IP model.

8. TCP/IP was defined before the emergence of the internet whereas OSI was defined after the internet emerged.

9. The minimum size of the header in TCP/IP is 20 bytes whereas the minimum size of the header in OSI model is 20 bytes.

10. TCP/IP guarantees reliability whereas OSI is not reliable.

11. TCP/IP does have clear demarcating points or boundaries between services, interfaces and protocols. For OSI model, there exists a clear distinction between the three.

12. TCP/IP first developed protocols followed by the model whereas the reverse is true in the case of the OSI model.

13. Transport layer in TCP/IP does not provide assurance regarding the delivery of packets whereas in OSI model, the transport layer provides assurance of the delivery of packets.

Final Thought!

OSI model is generally the preferable choice because of its easy troubleshooting facilities and improved network performance. TCP/IP is probably preferred by teammates or administrators because it is used in present-day networking structures. Both have their own list of advantages and disadvantages that makes it preferable for users. We have learnt more than 10 differences between TCP/IP and OSI model that will help clear doubts and understand about the protocols in depth.

Can you spot any other differences or similarities between the TCP/IP and OSI models? What are they?