TCP/IP

The Transmission Control Protocol / Internet Protocol (TCP/IP) is a software protocol that sits on top of the Internet Addressing protocol. It uses control flow and error recovery techniques to guarantee the delivery of transmitted data from one node to another.

TCP/IP has its own reference model

Notice it only has 4 layers

The Application Layer (4)

Performs the functions of the top three layers of the OSI 7-Layer model: Application, Presentation and Session Layers. It is responsible for node-to-node communication.

Typical protocols at this layer are

• HTTP

• HTTPS

• FTP

• Telnet

• SSH

• SMTP

• SNMP

• NTP

• DNS

• DHCP

• NFS

Host-to-Host Layer (3)

Handles the end-to-end communication and error-free delivery of data. It shields the upper-layer applications from the complexities of data. The two main protocols present in this layer are -

• TCP (Transmission Control Protocol)

  • Provides reliable and error-free communication between Nodes. It performs sequencing and segmentation of data. It also has an acknowledgment feature and controls the flow of the data through a flow control mechanism. It is a very effective protocol but has a lot of overhead due to such features. Increased overhead leads to an increased cost. TCP is connection-oriented.

• UDP (User/Unreliable Datagram Protocol)

  • Does not provide any of the features that TCP provides. It is the go-to protocol for applications such as video streaming that do not require reliable transport therefore it is very cost-effective. UDP is connectionless oriented.

Internet Layer (2)

Network Access Layer (1)