The Application Layer, also known as Layer 7, is the highest layer of the OSI model, responsible for supporting functions like:

1. Smart contract execution

2. Data storage and retrieval

3. User interfaces and interactions

4. Application-level protocols (e.g., HTTP, FTP, SMTP)

This layer provides services to end-user applications, enabling them to communicate with each other and access network resources. The Application Layer is responsible for:

1. Protocol negotiation

2. Data formatting and compression

3. Encryption and decryption

4. Authentication and authorization

Some common protocols that operate at the Application Layer include:

1. HTTP (Hypertext Transfer Protocol)

2. FTP (File Transfer Protocol)

3. SMTP (Simple Mail Transfer Protocol)

4. DNS (Domain Name System)

5. SSH (Secure Shell)

In the context of blockchain, the Application Layer is responsible for supporting the execution of smart contracts, interacting with the blockchain network, and providing user interfaces for applications and services.

Note that the Application Layer is distinct from the Application Service Layer (Layer 10) which is specific to blockchain architecture and provides a interface for users and applications to interact with the blockchain network.