...
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 provides acknowledgment and retry features and controls the flow of the data through a flow control mechanism. With such essential features, it’s a costly protocol in terms of performance. However, the reliability outweighs the 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)
Parallels the functions of ISO 7-Layer Network layer. It defines the protocols which are responsible for the logical transmission of data over the entire network. IP, ICMP, and ARP are protocols that reside at this level
Network Access Layer (1)
Combines the functionality of the IOS 7-Layer Data Link Layer and the Physical Layer. It is responsible the physical connectivity between Nodes