What Is the Application Layer?

The Application layer is the top layer in TCP/IP’s protocol suite. In the Application layer, you’ll find network applications and services that communicate with lower layers through the TCP and UDP ports discussed in Hour 6, “The Transport Layer.” You might ask why the Application layer is considered part of the stack at all, as the TCP and UDP ports form such a well-defined interface to the network. But it is important to remember that, in a layered architecture such as TCP/IP, every layer is an interface to the network. The Application layer must be as aware of TCP and UDP ports as the Transport layer is and must channel data accordingly.

TCP/IP’s Application layer is an assortment of network-aware software components ...

Get Sams Teach Yourself TCP/IP in 24 Hours, Fourth Edition now with the O’Reilly learning platform.

O’Reilly members experience books, live events, courses curated by job role, and more from O’Reilly and nearly 200 top publishers.