The TCP/IP model and the OSI model are two different conceptual models used to understand and describe how network protocols work. The TCP/IP model is a simpler and more practical model that is widely used in real-world networking, while the OSI model is a more theoretical and detailed model.

The TCP/IP model consists of four layers:

1. Network Interface Layer: This layer deals with the physical connection between the network device and the network medium. It defines how data is transmitted over the physical network, including the protocols used for addressing and error detection.

2. Internet Layer: This layer is responsible for routing packets across different networks. It uses IP (Internet Protocol) to address and route packets between different hosts on the internet.

3. Transport Layer: This layer is responsible for the reliable delivery of data between hosts. It provides mechanisms for establishing connections, breaking data into smaller packets, reassembling packets at the receiving end, and ensuring that data is delivered without errors or loss.

4. Application Layer: This layer is responsible for supporting specific network applications and protocols. It includes protocols such as HTTP (Hypertext Transfer Protocol), FTP (File Transfer Protocol), SMTP (Simple Mail Transfer Protocol), and DNS (Domain Name System).

On the other hand, the OSI model consists of seven layers:

1. Physical Layer: This layer deals with the physical transmission of data over the network medium, including electrical and mechanical specifications.

2. Data Link Layer: This layer provides error-free transmission of data frames between two adjacent nodes over a physical network. It includes protocols such as Ethernet and Wi-Fi.

3. Network Layer: This layer is responsible for routing packets across multiple networks. It includes protocols such as IP (Internet Protocol) and ICMP (Internet Control Message Protocol).

4. Transport Layer: This layer provides reliable end-to-end delivery of data between hosts. It includes protocols such as TCP (Transmission Control Protocol) and UDP (User Datagram Protocol).

5. Session Layer: This layer establishes, manages, and terminates communication sessions between applications. It includes protocols such as NetBIOS (Network Basic Input/Output System).

6. Presentation Layer: This layer is responsible for the formatting and presentation of data to the application layer. It includes protocols such as SSL (Secure Sockets Layer) and MIME (Multipurpose Internet Mail Extensions).

7. Application Layer: This layer supports specific network applications and protocols. It includes protocols such as HTTP, FTP, SMTP, and DNS.

According to the question, the TCP/IP model does not have a session layer, while the OSI model does have a session layer. The session layer in the OSI model is responsible for managing communication sessions between applications, while the TCP/IP model combines this functionality into the application layer.