Application layer:overview Our goals: learn about protocols by conceptual and examining popular implementation aspects of application-layer protocols application-layer protocols ·HTTP transport-layer service ·SMTP,IMAP models ·DNS client-server paradigm programming network peer-to-peer paradigm applications ·socket API Application Layer:2-3 Application layer: overview Our goals: ▪ conceptual and implementation aspects of application-layer protocols • transport-layer service models • client-server paradigm • peer-to-peer paradigm ▪ learn about protocols by examining popular application-layer protocols • HTTP • SMTP, IMAP • DNS ▪ programming network applications • socket API Application Layer: 2-3