Chapter 2:Application layer ▣2.1 Principles of 2.6 P2P file sharing network applications 2.7 Socket programming 2.2 Web and HTTP with TCP ▣2.3FTP 2.8 Socket programming 口2.4 Electronic Mail with UDP SMTP,POP3,IMAP 2.9 Building a Web ▣2.5DNS server 2:Application Layer 6
2: Application Layer 6 Chapter 2: Application layer 2.1 Principles of network applications 2.2 Web and HTTP 2.3 FTP 2.4 Electronic Mail ❖ SMTP, POP3, IMAP 2.5 DNS 2.6 P2P file sharing 2.7 Socket programming with TCP 2.8 Socket programming with UDP 2.9 Building a Web server
Application architectures ▣Client-server ▣Peer-to-peer(P2P) OHybrid of client-server and P2P 2:Application Layer 7
2: Application Layer 7 Application architectures Client-server Peer-to-peer (P2P) Hybrid of client-server and P2P
Client-server architecture server: always-on host permanent IP address server farms for scaling clients: communicate with server may be intermittently connected may have dynamic IP addresses *do not communicate directly with each other 2:Application Layer 8
2: Application Layer 8 Client-server architecture server: ❖ always-on host ❖ permanent IP address ❖ server farms for scaling clients: ❖ communicate with server ❖ may be intermittently connected ❖ may have dynamic IP addresses ❖ do not communicate directly with each other
Pure P2P architecture no always-on server arbitrary end systems directly communicate peers are intermittently connected and change IP addresses ▣example:Gnutella Highly scalable but difficult to manage 2:Application Layer 9
2: Application Layer 9 Pure P2P architecture no always-on server arbitrary end systems directly communicate peers are intermittently connected and change IP addresses example: Gnutella Highly scalable but difficult to manage
Hybrid of client-server and P2P Skype Internet telephony app Finding address of remote party:centralized server(s) Client-client connection is direct(not through server) Instant messaging Chatting between two users is P2P *Presence detection/location centralized: User registers its IP address with central server when it comes online User contacts central server to find IP addresses of buddies 2:Application Layer 10
2: Application Layer 10 Hybrid of client-server and P2P Skype ❖ Internet telephony app ❖ Finding address of remote party: centralized server(s) ❖ Client-client connection is direct (not through server) Instant messaging ❖ Chatting between two users is P2P ❖ Presence detection/location centralized: • User registers its IP address with central server when it comes online • User contacts central server to find IP addresses of buddies