The OSI Application Layer

By Stephen Bucaro

The Application layer, layer seven of the OSI model, provides the interface between applications and the Network Operating System (NOS). The Application layer provides network services and applications such as HTTP (Hypertext Transfer Protocol), FTP (File Transfer Protocol), TELNET, SNMP (Simple Netwrok Management Protocol) and SMTP (Simple Mail Transport Protocol).

When you think of the Application layer, don't think in terms of applications, but rather protocols. For example there are several different FTP applications that use the FTP protocol at the Application layer.

More Networking Protocols and Standards:
• IPv6 Dynamic Address Allocation
• The OSI Presentation Layer
• Session Border Controllers - More Than Just a Voice Firewall
• TCP Windowing
• IPv4 Address Classes
• X.25 and Frame Relay Overview
• What's the Difference Between a Packet and a Frame?
• What is PPP, PPPoA and PPPoE?
• OSI Transport Layer
• Representation of IPv6 Addresses

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