Computing – Communications and Networks - Application Layer

Application Layer
 Application layer supports network application
 applications that are distributed over the network
 applications that communicates through the network
 Many known protocols
 FTP: file transfer
 SMTP: email protocol
 HTTP:web protocol
 An application uses UDP or TCP, it is a designer’s choice
 Interface with the transport layer
 use for example the socket API: a library of C functions
 socket also means (IP address, port number)


The Application Layer is responsible for supporting network applications. The application layer
includes many protocols, including HTTP to support the Web, SMTP to support electronic mail,
and FTP to support file transfer. We shall see in Chapter 2 that it is very easy to create our own
new application-layer protocols.