Understanding Layer 7 and Layer 4

Layer 7

Layer 7 is a term used to refer to the seventh and highest layer of the seven-layer Open Systems Interconnect  (OSI) reference model for computer networking.  The OSI model is a method of describing how data moves between two networked devices. This layer, also known as the application layer, supports end-user applications and processes. It is closest to the end user and is wholly application-specific. The protocols at this level are processed by software on the communicating computers' application layer programs, which implement specific features corresponding to their roles as client or server in establishing and managing a network connection between them.

Some of the functions that take place at Layer 7 include:

-Processing data that is received

-Making data that is sent more readable for the computer

-Managing the communication between computers on a network

The most common protocols used at Layer 7 are HTTP (hypertext transfer protocol) and SMTP (simple mail transfer protocol). Web servers, for instance, use HTTP to interact with web browsers. The browser will send an HTTP request to the server asking for HTML pages or other types of content, such as images or stylesheets. This layer also handles things like authentication, displaying error messages to users and formatting information for humans to read.

Layer 4

Layer 4 of the OSI model is where we find the transport layer. This layer is responsible for ensuring reliable delivery of data between systems. It does this by managing sessions and providing error handling.

To ensure reliable delivery, the transport layer uses a technique called acknowledgment. With acknowledgment, the receiving system sends back a message to the sending system to let it know that the data has been received successfully. This helps to prevent data loss in cases where packets are lost or corrupted.

The transport layer also provides congestion control. This ensures that the network doesn't become overwhelmed with traffic, which can lead to degraded performance for all users.

Finally, the transport layer sets up end-to-end security for data transmission. This helps to ensure that data is not compromised during transit.

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