Chapter 2:application layer our goals: learn about protocols conceptual, by examining popular implementation application-level aspects of network protocols application protocols ·HTTP ■transport-layer FTP service models ·SMTP/POP3 /IMAP ■client-server DNS paradigm creating network peer-to-peer applications paradigm ■socket API Application Layer 2-3Application Layer 2-3 Chapter 2: application layer our goals:  conceptual, implementation aspects of network application protocols  transport-layer service models  client-server paradigm  peer-to-peer paradigm  learn about protocols by examining popular application-level protocols  HTTP  FTP  SMTP / POP3 / IMAP  DNS  creating network applications  socket API