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TCP/IP has its own reference model
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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.