User`s guide

TCP/IP Network Basics

TCP/IP Protocols

The Application Layer

The Application Layer is the layer where requests for data or services are

processed. Applications at this layer are waiting for requests to process and

all applications are “listening” at their respective

port. The Application Layer

has two protocols:

! File Transfer Protocol (FTP)

! Hypertext Transfer Protocol (HTTP)

Ports This figure shows the TCP/IP protocol stack. In the stack, TCP and UDP

each have access to 65,536 ports at the Application Layer. As a packet

moves up the stack, IP directs the packet to either a TCP port or to a UDP

port. Since all applications are listening at their respective ports, when the

packet arrives at the appropriate port, it can be processed correctly.

NOTE

The Application Layer is not where an Internet browser, spreadsheet, etc.

interact. Applications running at the Application Layer interact with the

browser, spreadsheet, etc. applications.

Application Layer

Transport Layer

Internet Layer

TCP

UDP

TCP/IP Stack

Ports

2 . . . 65,536

1 2 . . . 65,536

TCP Ports

UDP Ports